Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
TITLE
BATTERY COMPENSATION SYSTEM USING PWM
CROSS-REFERENCE TO RELATED APPLICATIONS
[001] This application claims the benefit and priority of US Patent
Application Serial Number
14/046,969, filed 06 October 2013 for BATTERY COMPENSATION SYSTEM USING PWM
(hereafter
referred to as "The Priority Application"). The Priority Application is a
continuation-in-part of US
Patent Application Serial Number 13/397,691, filed 16 February 2012 for PWM
HEATING SYSTEM
FOR EYE SHIELD, Publication No. US-2013-0212765-A1, Published 22 August 2013
(hereafter referred
to as "the Parent Application"). The Parent Application has also been filed as
PCT Patent Application
Serial Number PCT/U52013/026,227 which is hereby incorporated by reference.
FIELD
[002] This invention relates to regulating power from a battery to drive a
load, and more
particularly to compensating for a decrease in voltage from a Lithium-Ion
battery as it dissipates over
time in use to consistently power a portable electronic device.
BACKGROUND
[003] Various products, from anti-fog sport goggles, dive masks and other
highly portable
transparent anti-fog eye-protecting shields, to hand-held GPS devices, radios,
telephones and other
portable electronics devices having display units, use batteries not only to
power these devices but
also to heat the devices to prevent fogging of an eye shield or viewing
screen. And while some of
these devices have commonly used Lithium-Ion batteries to power the devices,
the use of Lithium-
Ion batteries is not as well known in others, such as the powering of heated
eye shields. And yet it
would seem desirable to use the benefits of Lithium-Ion battery technology in
many more such
devices to provide power to provide power to them them, except that a known
issue with Lithium-
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Ion batteries is the fact that, as their charge decreases over time in use,
the voltage output they
provide also decreases over time in use.
[004] A common characteristic of such portable devices is the fact that they
are light weight
enough to be carried on a user's body, e.g., worn on a user's head. Examples
of fog-prone sport
goggles intended for use during winter activities, have included goggles for
downhill skiing, cross-
country skiing, snowboarding, snowmobiling, sledding, tubing, ice climbing and
the like, and are
widely known and widely utilized by sports enthusiasts and others whose duties
or activities require
them to be outside in snowy and other inclement cold weather conditions.
Examples of fog-prone
dive masks have included eye and nose masks independent of a breathing
apparatus as well as full-
face masks in which the breathing apparatus is integrated into the mask.
Examples of fog-prone
eye-protecting shields have included a face shield that a doctor or dentist
would wear to prevent
pathogens from getting into the user's mouth or eyes, or a transparent face
shield portion of a
motorcycle helmet. Fogging that impairs vision is a common problem with such
goggles, dive masks
and eye-protecting shields.
[005] Examples of hand-held devices that require consistent power to heat the
displays of
such devices to prevent fogging of the display have included hand-held GPS
units, radios,
telephones, medical devices (EKG readouts), readers, tablets, portable
computers, point of sale
terminals, etc.
[006] There have been various conductive apparatus devised for preventing
condensation
build-up on eye-shields and viewing screens of such hand-held devices. The
purpose of these
conductive apparatus has been to provide an eye shield and viewing screen that
may be maintained
free of condensation so that the user would be able to enjoy unobstructed
vision and viewing during
viewing activities. Prior sports goggles and hand-held electronic devices with
electronic systems
have been primarily used in environments requiring a high degree of
portability, that is, where a
power source for powering the electronics for the device has been
advantageously carried on a strap
for the goggle or on the device itself as shown and described in co-pending US
Patent Application
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Serial No. 61/563,738, by McCulloch, for Modular Anti-fog Goggle System. While
such battery-
powered devices, especially heating devices which consume extraordinary
amounts of power from
batteries, need to be judicious in the use of total power source, generally
measured in amp-hours, to
preserve power source life, it has also become important that the power
circuitry of such systems
provide a consistent level of power to the device, even though the device
battery may become
increasingly depleted over time in use. Thus, the ability to adjust the amount
of current delivered to
the device's resistive element, compensated for decreasing voltage as the
battery charge is
depleted, has also become desirable.
[007] Thus, while it has remained an important goal to maximize battery life,
in which case
the use of pulse-width modulation (PWM) has proven useful as described in co-
pending US Patent
Application, Serial No. 13/397,691 for PWM Heating System for Eye Shield,
Publication No. US-2013-
0212765-A1, the limitation of Lithium-Ion battery depletion and correspondent
voltage depletion
has remained a problem. Thus, it has been recognized that, where there is
sufficiently available
battery power to perform heating operations on a goggle or hand-held device,
an appropriate
amount of additionally available power may be useful to make power supplied to
the device more
consistent throughout the depletion cycle of the battery.
[008] No prior art goggle or hand-held electronic devices have made use of
their battery
supplies to provide consistent power to the device despite depletion of
battery charge. US Patent
No. 4,868,929, to Curcio, for Electrically Heated Ski Goggles, comprises an
eye shield with embedded
resistive wires operatively connected via a switching device to an external
power source pack
adapted to produce heating of the eye shield for anti-fog purposes. US Patent
No. 7,648,234, to
Welchel et al., for Eyewear With Heating Elements, discloses use of nichrome
and thin film heating
elements used for heating an eye shield and discloses use of a control
mechanism for turning on and
off the heat to the eye shield. Neither discusses the foregoing power
regulation, conservation and
distribution concepts using PWM circuitry to provide more even power to the
device despite charge
depletion.
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[009] A problem with sport goggles which have employed electrical heating is
that of uneven
heating over the entire surface of the eye shield. Goggles and goggle eye-
shields are manufactured
with an irregular shape required to maintain a position close to the face of
the wearer and allowing
cutouts for the nose and extended edges for peripheral vision. Even heating of
this irregular shape
has not been accomplished in the prior art.
[010] Prior art devices having irregularly-shaped eye shields have been
susceptible to hot
spots, and using such devices in limited battery-powered applications has
unduly discharged the
battery. The reason for the hot spots has been because the electrical
resistivity between the
electrical connections across the resistive elements on the eye shield has
been greater or lesser at
different locations on the eye shield such that the amount of electrical
current consumed in the
areas with less distance between terminal connections is greater and the
amount of electrical
current consumed in areas with greater distance between the terminal
connections is less. For
example, where the terminals are on either side of the lens in a resistive
wiring application, there
have been problems with evenly heating the lens since the distance the wire
has had to travel from
one terminal to the other has been greater for those wires traveling over the
bridge of the nose and
down under the eyes than other wires that travel the shorter distance across a
central portion of the
lens. To overcome fogging conditions enough power must be applied to overcome
the fog in the
areas with the greatest distance between the terminal connection points,
causing the smaller areas
to overheat, which in turn wastes power. Thus, the problem has resulted in
limited usefulness of
heating of goggle eye-shields. Because of the irregular shape of eye shields,
these problems exist
whether one is considering resistive wire applications or resistive-film
applications.
[011] Thus there has developed a need to provide a preferably automatically
adjusting
variable power source which can provide adequate current to meet the
requirements of anti-fogging
a device, or heating of the device for other reasons, all while providing
consistent power despite
battery depletion across the load and without presenting excessive power above
that which is
required. Also there has developed a need to provide multiple current supplies
to multiple heating
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element regions to enable even heating of goggle eye-shields across the entire
eye shield surface
while providing consistent power despite battery depletion across each region,
or load, but without
excessive use of power or hot-spots at each region, or load.
[012] Switching the power on to a goggle when you experience fog conditions,
and then
switching it off when a user suspects it is no longer needed, or doing this to
otherwise provide
desired heat or power to a hand-held device, is not an efficient way to
overcome fog or to otherwise
heat or provide power to a device. This is because while the device is on, it
is using full power and
this is an inefficient use of battery resources. Also, the user doesn't really
know precisely when to
turn it off, so at best the user is guessing when is the best time to turn it
off. Further, when a user is
involved and concentrating on the activity at hand, it often is not convenient
to have to turn on, or
off, the power to heat the eye shield or other hand-held device. Manual
switching of power to an
eye shield or other hand-held device doesn't allow the user to set an
intermediate heat value that is
sufficient to curtail fogging or otherwise heat but which also conserves
battery life. Further, there
are no known systems disclosed in the prior art for balanced heating of a film
or other resistive
element on an eye shield or hand-held screen, while compensating to provide
consistent power
despite battery depletion, which also provide variable control of a heating
element on the device.
SUMMARY
[013] In accordance with an aspect of the invention, there is provided an eye-
shield
condensation preventing system comprising: an eye shield adapted for
protecting a user's eyes and
adapted for defining at least a partially enclosed space between the user's
eyes and the eye shield, a
power source, a pulse-width modulator (PWM), a switching means responsive to
the pulse-width
modulator, a heating element on the eye shield, and a circuit interconnecting
the power source, the
pulse-width modulator, the switching means and the heating element for
controlling heating of the
eye shield. Preferably, the switching means comprises a metal-oxide-
semiconductor field-effect
transistor.
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[014] The device of this aspect of the invention provides a single-PWM, single
heating region
eye shield fog prevention device that enables efficient heating of the eye
shield or lens so that
battery life is maximized, since PWM can be preset to an output having a
percentage ratio of on to
off cycles that is tailored specifically to the particular goggle lens to
which power is being applied.
[015] In accordance with another aspect of the invention, there is provided an
eye-shield
condensation preventing system comprising: an irregular-shaped eye shield
comprising a surface
area divisible into a plurality of regions of one or more sizes to facilitate
divisible heating of the eye-
shield, the eye shield being adapted for protecting a user's eyes and adapted
for defining at least a
partially enclosed space between the user's eyes and the shield. The system
further comprises a
power source, a plurality of PWMs, each PWM operatively connected with the
power source and a
plurality of switching means, each switching means responsive to a
corresponding PWM. With this
aspect of the invention, there are a plurality of heating elements on the eye-
shield, each the heating
element extending to a corresponding size region of the eye-shield, and a
plurality of circuits, each
the circuit interconnecting one of the PWMs with a corresponding one of the
switching means and
one of the corresponding heating elements. Each the PWM produces a duty cycle
for providing an
amount of current to the corresponding heating element such that the power
output of each region
of the eye shield corresponds to a desired output for the region of the eye
shield.
[016] In accordance with the aspects of the invention described above, there
is provided an
eye-shield condensation preventing system comprising: an eye-shield adapted
for protecting a
user's eyes and adapted for defining at least a partially enclosed space
between the user's eyes and
the eye shield, the eye shield having a surface area divisible into at least
one region for facilitating
region heating of the eye-shield to a desired temperature, a power source, at
least one PWM, at
least one heating element on and corresponding with the at least one region
for facilitating region
heating of the eye shield, the at least one heating element corresponding with
the at least one
PWM. In this embodiment, there is at least one circuit interconnecting the
power source, the at
least one PWM and the at least one corresponding heating element for heating
the eye shield,
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wherein the at least one PWM controls current to maintain the temperature of
the at least one
heating element region to a temperature above the anticipated dew point of an
operating
environment.
[017] The device of the multiple-region aspect of the invention provides a
multiple-PWM
resistive film heating system on the eye shield or lens surface that is
divided into multiple regions,
for example regions according to irregular and differently-shaped portions of
the lens such as
directly over the bridge of the nose as compared to directly in front of the
eyes, to enable even
heating of differently-shaped or sized regions. Thus, for example, the regions
may be used to divide
the lens into a plurality of regions, each of similar area from one region to
the next, to enable more
even heating across the eye shield. Or, conversely this division may be used
to allow specific heating
of a certain area of the eye shield, for example to ensure proper function of
an electronic display
portion of the lens.
[018] In accordance with another aspect of the invention building on the
multiple-region
aspect of the invention, the PWMs may be operated in accordance with a profile
such that the
power per square unit, i.e., power density, of each region of the eye shield
may be assured to be
substantially equal and evenly distributed across the region regardless of the
size of each region. Or,
alternatively, heating of the regions may be independently adjusted to create
a specific profile
desired for a particular eye shield to account for various pre-determined
weather conditions, various
activities or eye shield types, shapes and sizes.
[019] Preferably, the plurality of PWMs of this aspect of the invention
comprises a
microcomputer capable of simultaneously performing a plurality of various
internal PWM functions
corresponding to the plurality of PWMs, the microcomputer having a plurality
of I/O ports for
interconnecting the internal PWM functions with the plurality of circuits.
Further, preferably, each
of the switching means in accordance with this aspect of the invention
comprises a metal-oxide-
semiconductor field-effect transistor (MOSFET).
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[020] In accordance with another aspect of the invention, whether involving
the single-
region, single-PWM device, or whether involving the multiple-region, multiple-
PWM device, there is
provided an eye-shield condensation preventing system as previously summarized
which further
comprises a current adjustment means (CAM) operatively connected to each PWM
(whether a
single-PWM embodiment or a multiple PWM embodiment) for varying duty cycle of
the power
source via each PWM in turn varying the amount of current delivered to each
heating element.
[021] The device of this aspect of the invention provides the ability of the
CAM for efficient
managing of the temperature of the eye shield lens at a temperature that is
just above the dew
point temperature to effectively prevent fogging with a minimum of attention
by the user. This, in
turn, allows power savings to enable longer battery life.
[022] In accordance with another aspect of the invention, there is provided an
eye-shield
condensation preventing system as previously described, whether a multiple-
region, multiple-PWM
embodiment, or a single-region, single-PWM embodiment, the device further
comprising means for
measuring ambient temperature and relative humidity and means for calculating
dew point. The
means for calculating dew point in this aspect of the invention is preferably
operatively connected
with the CAM (preferably further comprising microcomputer means) such that the
CAM increases
power to the electrical circuit when temperature within the space by the eye
shield falls below the
dew point temperature threshold and reduces power to the electrical circuit
when temperature
within the space defined by the eye shield climbs above the dew point
temperature threshold. Thus
the invention is capable of feeding a pulse to the resistive heating element,
e.g., the film heating
element, that is just enough to keep it at just above the dew point to
effectively and automatically
prevent fogging and to conserve battery life. The means for calculating dew
point preferably
comprises microcomputer means operatively connected with the temperature and
relative humidity
sensing means.
[023] The eye-shield condensation preventing system of this aspect of the
invention may
further comprise a relative humidity sensor and a temperature sensor, each
sensor located within
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the space defined by the eye shield. Such a system further comprises means,
for example
microcomputer means, operatively connected with the relative humidity and
temperature sensor for
periodically calculating dew point temperature. Further, the at least one
pulse-width modulator is
responsive to the means for periodically calculating dew point temperature to
control the at least
one heating element such that the at least one heating element is maintained
at a temperature at
above dew point to assure prevention of fogging over time.
[024] In accordance with another aspect of the invention, the eye-shield
condensation
preventing system of the previous two aspects of the invention, as pertaining
to multiple-region
embodiments of the invention, may further comprise region profiling logic
enabling a single
adjustment from the variable current adjustment mechanism to affect
proportional adjustments to
each region relative to other regions. Thus, the invention provides varying
coordinated duty cycles
to power multiple resistive regions of an eye shield for the purpose of
distributing heating evenly
throughout the entire eye shield by adjusting the power delivered to each
segment based on a
profile of the eye shield. Further, the device of this aspect of the invention
provides automated
profile characteristics incorporated into the fog prevention system such that
desired heating of the
lens, whether it be even heating across multiple regions across the entire
lens, or a pre-determined
specific heating pattern, or heating footprint using different regions of the
lens, may be maintained
upon manual, or automated, adjustment of the heating power directed to the
lens.
[025] In accordance with yet another aspect of the invention, there is
provided an eye-shield
condensation preventing system as described above in the single-region or the
multiple-region
aspects of the invention as described above, and further in accordance with
the previous aspect of
the invention comprising a plurality of predetermined data profiles and
corresponding selection
means enabling control of each region of the eye shield in accordance with a
user-selected one of
the data profiles.
[026] The device of this aspect of the invention provides selectable profile
characteristics
incorporated into the eye shield fog preventing system such that appropriate
heating may be
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selected by the user depending upon weather and activity level conditions, or
eye-shield features
employed, such as video recording, heads-up display, global positioning
system, etc.
[027] Each of the eye shields disclosed herein are adapted for protecting a
user's eyes from
wind, debris, snow, rain, extreme temperatures and elements which could harm
the eyes or
otherwise impair vision. Each eye shield is also adapted to form and define at
least a partial
enclosure around and in front of the eyes. This enclosure warms up relative to
conditions outside of
the enclosure as a result of body heat transmitted into the space defined by
the eye shield, and the
enclosure also experiences higher relative humidity compared to outside
conditions as a result of
perspiration. When the temperature of the eye shield drops below the
temperature within the eye
shield at which dew, or condensation, would form on the inside of the eye
shield, fogging of the eye
shield occurs.
[028] One purpose of the present invention is to provide an eye shield fog
prevention
system that effectively prevents the eye shield from fogging, regardless of
weather conditions.
Another purpose of the present invention is to provide an eye shield fog
prevention system that
employs PWM in such a way that power and energy are conserved and battery life
is extended.
Another purpose of the invention is to provide an eye shield fog prevention
system that adjusts the
power to the heater on the lens in accordance with current dew point
conditions, either manually,
or automatically, increases power to the eye shield as temperature within the
eye shield is less than
or falls below the dew point temperature, or so decreases power when
temperature within the eye
shield is above the dew point temperature. Another purpose of the present
invention is to provide
an eye shield fog preventing system that assures and simplifies the attainment
of fog-free usage in
varying weather and activity conditions, with a plurality of different sized
and shaped eye shields, by
providing profiles that at least partially automate heating of the eye-shield.
Yet another purpose of
the invention is to provide such profiles that are user selectable. The
foregoing listing is not
intended as an exclusive listing of purposes of the invention, there may be
other purposes for which
the invention may be suited which are not listed, and the presence or absence
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herein shall not necessarily limit the spirit and scopes of the invention as
further defined and
claimed herein.
[029] The shield condensation preventing system of any of the foregoing
aspects of the
invention may be adapted for use for heating in an anti-fog sport goggle or
any protective eye-
shield, such as for skiing, inner-tubing, tobogganing, ice-climbing, snow-
mobile riding, cycling,
running, working with patients, in other medical or testing environments, and
the like. Further, the
system of any of the foregoing aspects of the invention may be adapted for use
in a diving mask.
[030] In accordance with another aspect of the invention, there is provided a
compensation
system adapted for use with any of the foregoing battery-powered, PWM-driven
eye shields, or
other portable electronic device, to enable consistent power to the device
load despite battery
voltage drop resulting from battery depletion. The compensation system in
accordance with this
aspect of the invention comprises: a voltage divider circuit for
proportionally adjusting the voltage
to a measurable range; an analog to digital converter for receiving the output
from the voltage
divider and converting it into a digital voltage value; and means for
receiving digital voltage input
and user-determined power setting input for determining a compensating duty
cycle for application
to the PWM to drive the load consistently at the user-determined power setting
despite decrease in
battery voltage resulting from battery depletion. Preferably, the voltage
divider circuit of an
embodiment in accordance with this aspect of the invention comprises two
precision resistors in
series between positive and negative terminals of the battery for
proportionally adjusting the
voltage to a measurable range, the voltage divider circuit preferably having a
tap between the two
resistors adapted to provide the proportional voltage measurement to an I/O
pin on an analog-to-
digital converter. Preferably, the user-determined, or provided, power setting
for this and another
aspect of the invention comprises a power level setting set by a dial, a knob,
or a push button
system, together with some form of visual feedback to the user to further
enable selection of the
setting.
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[031] In accordance with an embodiment of the invention, there may be provided
mode
switching means for user selection of battery conservation mode or consistent
power output mode.
The battery conservation mode provides an off switch for the compensation
system, whereas the
consistent power mode provides an on switch for the compensation system.
Though the battery
conservation mode uses less battery power than the consistent power mode, for
those times where
there is sufficient battery power to use the consistent power mode, it may be
preferable to a user to
do so, since a user-determined power level in this latter mode would yield
results consistent with
what a user would expect with an otherwise fully-charged battery. The
selection of battery
conservation mode or consistent power mode depends upon the total battery
charge available, the
longevity of a particular battery as experienced by the user, and the
anticipated level of heating
required for a number of use hours anticipated by the user.
[032] In accordance with an embodiment of the invention, the battery
compensation system
is adapted for use with at least one lithium-ion battery-powered, PWM-driven
portable electronic
device. Such a portable device may include an anti-fog eye shield, such as for
example a ski goggle, a
diving mask, a motorcycle or snowmobile helmet visor, or a medical or testing
visor. Or,
alternatively, such a portable device may include a hand-held GPS unit, a hand-
held radio, or a cell
phone.
[033] In accordance with an embodiment of the invention, the compensation
system of the
invention further comprises a metal-oxide- semiconductor field-effect
transistor switching means
responsive to the pulse-width modulator. Further, in accordance with an
embodiment of the
invention, the compensation system of the invention further comprises current
adjustment means
operatively connected to the pulse-width modulator for varying duty cycle of
the power source via
the pulse-width modulator in turn varying the mount of current delivered to
the load.
[034] In accordance with an embodiment of the invention, the means for
receiving voltage
input and user-determined power setting input for determining compensating
duty cycle comprises
a microprocessing unit for receiving voltage input and user-determined power
setting input and
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executing software code to determine a compensating duty cycle for application
by the software to
the PWM to drive the load consistently at the user-determined power setting
despite decrease in
battery voltage resulting from battery depletion. For this embodiment of the
invention, the
microprocessing unit is preferably a battery-powered microprocessing unit. It
will be appreciated by
those of ordinary skill in the art that readily-available microprocessing
units having on-board analog-
to-digital conversion means may be used for the present invention.
[035] Still further, determination of a compensating duty cycle may comprise a
data lookup
table of PWM duty cycle values organized according to power setting and
battery depletion voltage
drop and for use by the code steps run by the microprocessor to select a
compensating duty cycle
for application to the PWM to drive the load consistently at the user-
determined power setting
despite decrease in battery voltage resulting from battery depletion. This
embodiment of the
invention including a lookup table provides generally faster operation and is
easier to code than
using floating-point calculations, though it will be appreciated that either
may be used to implement
the invention in accordance with its true spirit and scope. Further, while
conceivably a discrete logic
circuit could be used to perform the functions of the compensation system of
the invention, such
would likely be unduly expensive to implement and no more effective than the
software and data
table lookup functions that are preferred for the invention.
[036] In an alternate embodiment, the software steps themselves may be used to
calculate a
compensating duty cycle for application to the PWM to drive the load
consistently at the user-
determined power setting despite decrease in battery voltage resulting from
battery depletion. The
formula for determining the compensating duty cycle for this embodiment of the
invention, which is
the same formula used to determine data table duty cycle values (from user
input power settings
and measured voltage) used in a previous software embodiment is as follows:
Desired Power * Load Resistance
Duty Cycle = _________________________________ * 100
(Battery Voltage)2
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[037] The compensation system in accordance with this aspect of the invention
enables
maintenance of a user-selected and/or desired power setting to drive a load to
consistently heat a
portable device, such as anti-fog goggles or a hand-held GPS, radio or phone,
despite partial
depletion of a device battery, as long as there is sufficient battery charge
to maintain the system-
compensated power output. Thus, as the voltage from the battery drops
resulting from battery
depletion from use over time, the system compensates by increasing the duty
cycle of the PWM
driver for the device.
[038] In accordance with another aspect of the invention, there is provided an
alternative
embodiment compensation system adapted for use with a battery-powered, multi-
channel PWM-
driven portable electronic device having a plurality of loads corresponding to
each PWM channel to
enable consistent power to each of the loads of the device despite battery
voltage drop resulting
from battery depletion. The compensation system in accordance with this aspect
of the invention
comprises: a voltage divider circuit for proportionally adjusting the voltage
to a measurable range;
an analog to digital converter for receiving the output from the voltage
divider and converting it into
a digital voltage value; and a microprocessing unit for running software code
steps for receiving
digital voltage input and user-determined power setting input for each load
for determining a
compensating duty cycle for application by the software to each PWM channel to
drive each
corresponding load consistently at the user-determined power setting despite
decrease in battery
voltage resulting from battery depletion.
[039] The compensation system in accordance with this aspect of the invention
enables
compensation for a depleting battery source for maintaining, with the use of a
multi-channel PWM
system, consistent power over time to each of a plurality of loads of a
portable device (as long as
there remains sufficient battery charge to power the device), such as a multi-
region, anti-fog eye
shield powered by the system to evenly heat each of the regions across the eye
shield to a
consistent temperature. Alternatively, such a system in accordance with this
aspect of the invention
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may be used to provide consistent heating, despite battery depletion over
time, to heat a multi-
heating-element-region eye shield to prevent fogging in each of the regions
according to a custom
heating profile applied to the eye shield.
[040] Thus, preferably the compensation system in accordance with this aspect
of the
invention is embodied wherein each of the plurality of loads comprises a
heating element region on
an eye shield and each corresponding PWM channel is for providing the same
power density to each
heating element region for even heating across the entire eye shield. This
even heating embodiment
of the invention further preferably comprises a data lookup table of PWM duty
cycle values
organized according to power setting and battery depletion voltage drop and
for use by the code
steps to select a compensating duty cycle for application to each PWM to drive
each load
consistently at the user-determined power setting despite decrease in battery
voltage resulting from
battery depletion.
[041] Further, preferably, the compensation system in accordance with this
aspect of the
invention to provide consistent heating in accordance with a custom profile is
embodied wherein
each of the plurality of loads comprises a heating element region on an eye
shield and each
corresponding PWM channel is for providing a power density to each heating
element region in
accordance with the custom heating profile across the eye shield. This custom
heating embodiment
further comprises a plurality of data lookup tables of PWM duty cycle values,
one data lookup table
for each different power density specified by the custom heating profile, each
data table being
organized according to power setting and battery depletion voltage drop and
for use by the code
steps to select a compensating duty cycle for application to each PWM to drive
each load
consistently at the corresponding power setting despite decrease in battery
voltage resulting from
battery depletion.
[042] Each of the aspects of the invention, whether single channel PWM-driven,
or multi-
channel PWM-driven, provides for consistent power to the load of a portable
electronic device,
despite charge/ or power, depletion or dissipation of the battery over time in
use. Thus, these
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aspects of the invention provide a consistent feedback to the user who is
reinforced and supported
in coming to expect that a certain power setting on the device, selected from
a series of power
settings such as 2 Watts, 4 Watts, 6 Watts, 8 Watts or 10 Watts, will
effectively heat the portable
device at the desired power level during anticipated weather conditions.
[043] The compensation system of the invention, whether single-channel PWM or
multi-
channel PWM embodiments of the invention, further preferably comprises a data
lookup table of
PWM duty cycle values organized according to power setting and battery
depletion voltage drop and
for use by the code steps to select a compensating duty cycle for application
to the PWM to drive
the load consistently at the user-determined power setting despite decrease in
battery voltage
resulting from battery depletion.
[044] The subject matter of the present invention is particularly pointed out
and distinctly
claimed in the concluding portion of this specification. However, both the
organization and method
of operation, together with further advantages and objects thereof, may best
be understood by
reference to the following descriptions taken in connection with accompanying
drawings wherein
like reference characters refer to like elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[045] FIG. 1 is a graphic representation of a plurality of electrical signals
emanating from a
pulse-width modulator (PWM);
[046] FIG. 2 is a front plan view schematic representation of an irregular-
shaped eye shield
having a single-region, resistive heating element film heater thereon;
[047] FIG. 3 is a front plan view schematic representation of an irregular-
shaped eye shield
having a resistive heating element film heater thereon that is divided into a
plurality of regions;
[048] FIG. 4 is a front plan view schematic representation of an irregular-
shaped eye shield
having a resistive heating element film heater thereon that is divided into a
plurality of regions;
[049] FIG. 5 is a schematic representation of a single-PWM, single-region eye
shield fog
prevention system in accordance with an aspect of the invention;
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[050] FIG. 6 is a schematic representation of a single-PWM, single-region eye
shield fog
prevention system in accordance with an aspect of the invention;
[051] FIG. 7 is a schematic representation of another embodiment of a single-
PWM, single-
region eye shield fog prevention system in accordance with an aspect of the
invention;
[052] FIG. 8 is a schematic representation of yet another embodiment of an
automated
single-PWM, single-region eye shield fog prevention system in accordance with
another aspect of
the invention;
[053] FIG. 9 is a schematic representation of still another embodiment of a
multiple-PWM,
multiple-region eye shield fog prevention system in accordance with another
aspect of the
invention;
[054] FIG. 10 is a schematic representation of another embodiment of an
automated
multiple-PWM, multiple-region eye shield fog prevention system in accordance
with yet another
aspect of the invention;
[055] FIG. 11 is a schematic representation of a micro-computer controlled
embodiment of
an automated multiple-PWM, multiple-region eye shield fog prevention system
also including a
charger;
[056] FIG. 12 is a block diagram of a prior system for regulating battery
voltage that
otherwise depletes over time in use;
[057] FIG. 13 is a block diagram of an alternate embodiment of a battery
compensation
system in accordance with an aspect of the invention;
[058] FIG. 14 is a flow diagram of software steps for performing the functions
of a battery
compensation system in accordance with the present invention;
[059] FIG. 15 is a sample data table of duty cycles to be applied by a PWM to
a battery
compensation system in accordance with the invention;
[060] FIG. 16 is a block diagram of an alternate embodiment of a battery
compensation
system adapted for a multi-load device; and
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[061] FIG. 17 is another sample data table of duty cycles to be applied by a
PWM to a battery
compensation system in accordance with the invention.
DETAILED DESCRIPTION
PULSE-WIDTH MODULATION
[062] Pulse-Width Modulation (PWM) is used mostly in motor speed control
applications for
varying the speed of a motor. Referring to FIG. 1, PWM is characterized by
either an analog or a
digital signal generated by a pulse width modulator, such as an analog
oscillator, or a digital logic
device, which provides varying duty cycles that are a percentage on, for
example such as 10%, 20%,
30%, and up to 90% or more, on, and a corresponding percentage off, such as
90%, 80%, 30%, and
down to 10% or less, off, all as illustrated by numbers 1-9 on FIG. 1. Dotted
lines 10 are used to
point out the wavelength of the PWM signal, and dotted lines 11 are used to
point out the constant
voltage magnitude on (high) condition and the constant voltage magnitude off
(low) condition.
Thus, for example, where the PWM circuit connected to a 12-volt battery is 40%
on and 60% off, one
might say that the PWM signal represents a 12-volt PWM circuit at 40% power.
Thus, the PWM
circuit can run a motor at 40% of its maximum speed, or alternately another
percentage of the
motor's maximum speed, with a constant voltage source and without adjusting
voltage, and this
provides the effect of providing a continuous lower voltage by regulating the
current delivered to
the motor. PWM signals typically have a fixed frequency as is the case with
those shown in FIG. 1,
and they are typically of a constant full voltage at the full voltage level or
a constant no voltage at
the low voltage level, though this is not absolutely necessary.
SINGLE-REGION, SINGLE-PWM EMBODIMENT
[063] Referring to FIG. 2, there is provided in accordance with part of a
first embodiment of
the invention an eye shield lens or protective eyewear 200 adapted for at
least partially defining an
enclosure around a user's eyes and having thereon a single-region resistive
transparent conductive
film heating member 202. Along an upper edge of the film heating member 202
there is a bus-bar
heating element 204 interconnected with a power source (not shown) via a lead
wire 212. The film
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heating member 202 may be comprised of indium-tin oxide (ITO) or other
material designed in the
form of a resistive element that generates heat when connected to an
electrical circuit.
[064] A lower buss-bar heating element 206 is provided along a lower edge of
the film
heating member 202 and which is interconnected with the power source via
another lead wire 214.
As is typical with many eye shields, such as in the case of winter sports
goggles, the eye shield lens
200 is irregular shaped having two wider similarly shaped square, rectangular,
circular or elliptical
areas 209, 210, directly anterior of a user's eye during use, and a narrower
area 208 above the
bridge of the nose of the user during use. Because of the different shapes of
the lens 200 at each of
these regions, and since the area over the bridge of the nose is smaller than
directly in front of the
eyes, there would be a tendency for the lens to be hotter over the bridge of
the nose since there
would be lesser measured electrical resistance in this area.
[065] As shown in FIG. 5, a first embodiment of the invention is provided as a
single-PWM,
single-region fog prevention system 500 in accordance with the first aspect of
the invention. System
500 comprises a single PWM 502 for generating a constant ratio PWM signal 503,
switching means
504, such as preferably a MOSFET switch as shown in FIG. 6, a heating element
202 deposited on a
lens 200, and a power source 505 having positive and negative terminals 510,
512. The foregoing
elements are interconnected in a circuit via a positive lead wire 212 and a
negative lead wire 214.
PWM signal 503 controls switching means 504 which controls power to the
heating element 202.
Since in this embodiment of the invention there is no means of varying input
voltage to the PWM
502, the PWM is set to a constant ratio, on to off, that would allow for
heating of a single-region
heating element 202 on the lens 200 at a constant temperature. Referring to
FIG. 6, a single-PWM,
single-region fog prevention system 600 is shown comprising a battery power
source 505 having
positive and negative terminals 510, 512, circuit wires 212, 214, PWM 502
(which generates signal
503), eye shield 200 and heating element 202 which is the same as system 500
except the generic
switching means has been replaced with a MOSFET switch 602. While preferably a
MOSFET switch is
employed with the current invention, other switching means including relays,
power transistors or
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other currently known switches may be used without departing from the true
scope and spirit of the
invention.
Current Adjustment Means (CAM)
[066] Referring now to FIG. 7, a single-PWM, single-region fog prevention
system 700 is
shown comprising a battery power source 505 having positive and negative
terminals 510, 512,
circuit wires 212, 214, PWM 502 (which generates signal 503), MOSFET 602, eye
shield 200 and
heating element 202 which system is the same as system 600 except the system
700 further
comprises a current adjustment means (CAM) 702. In this embodiment of the
invention, the CAM
702 is shown as a device which comprises a potentiometer and has an internal
reference voltage
(vref) that is lower than the battery minimum usable voltage and provides an
output voltage (input
voltage to the PWM), the output voltage from the CAM being some voltage
between zero and the
reference voltage (vref) based upon the setting of the potentiometer.
Responsive to the CAM 702,
the PWM 502 produces a corresponding percentage on/off signal that can be
varied as a result of
output from the CAM. In a preferred system using digital logic, as shown and
further described
below in connection with FIG. 11, a software control CAM responsive to a MORE
(increase) button
and responsive to a LESS (decrease) button directly varies the duty cycle of
the PWM and thereby
varies the amount of current delivered to the heating element 202 without
requiring an
intermediate voltage reference.
[067] An output line 704 carrying the output voltage of the CAM 702 is
operatively
connected between the CAM and the PWM 502. The PWM 502 translates the output
voltage from
the CAM 702 into a signal having a duty cycle corresponding and proportional
to the magnitude of
the voltage into the PWM. The duty cycle of the PWM's 502 output will
therefore vary in relation to
the voltage in from the CAM 702 such that a near-zero input voltage from the
CAM to the PWM will
result in a near-zero percent on / near 100 percent off duty cycle output of
the PWM. By contrast,
where the voltage from the CAM 702 to the PWM 502 is near the maximum voltage
(vref) of the
CAM, a resulting near 100 percent on / near-zero percent off duty cycle output
of the PWM would
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result. Further, and accordingly, for each intermediate setting of the CAM 702
between minimum
and maximum output voltage to the PWM 502, a corresponding intermediate
percentage on /
percentage off duty cycle output of the PWM would result. Thus, the CAM 702
enables varied
output duty cycles of the PWM 502.
[068] As further described below, a current adjustment means, such as CAM 702,
may also
be used with a multiple-region embodiment of the invention as shown in FIG. 9.
Dew Point Calculation and Automation
[069] Referring now to FIG. 8, a single-PWM, single-region fog prevention
system 800 is
shown comprising a power source 505 having positive and negative terminals
510, 512, circuit wires
212, 214, PWM 502 (which generates signal 503), MOSFET 602, eye shield or lens
200 and heating
element 202 which system is the same as system 700 except that system 800
further comprises
means 802, preferably a microcomputer, for calculating dew point (dew point
calculator, or DPC), a
temperature sensor 804 and a relative humidity sensor 806 operatively
connected to the DPC via
signal means 807, 809 and in accordance with another aspect of the invention.
This aspect of the
invention enables automation of adjustment of the CAM based upon temperature
sensor 804 and
relative humidity sensor 806 inputs taken from sensing environmental
conditions within the space
defined between the eye shield 200, near the heating element 202, and the
user's eyes.
[070] As shown, the DPC 802 is operatively connected with the CAM 702 via
electrical signal
means 803 to signal an increase in current and signal means 805 to signal a
decrease in current such
that the DPC signals the CAM when environmental conditions within the space
defined by the eye
shield 200 have changed thus requiring an adjustment to the heating element
202 from the system
800. When the system 800 is initially started, the DPC 802 calculates the dew
point temperature and
compares it to the actual temperature within the space defined by the eye
shield 200 and signals the
CAM 702 accordingly. If the dew point temperature, as calculated by the DPC
802, is greater than
the temperature within a space defined between the eye shield 200 and a user's
eyes, then logic
within the DPC signals to the CAM 700 to increase the voltage out to the PWM
502, which in turn
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increases the duty cycle of the PWM output, which in turn increases power to
the heating element
to increase the temperature of the eye shield 200 and the space between the
eye shield and a user's
eyes. Thus, subsequent sensory input to the system 800 from the temperature
sensor 804, the
relative humidity sensor 806, and calculations by the DPC 802, would all
reflect not only changing
ambient conditions, but temperature changes resulting from the aforementioned
increase request
from the system 800 as well. Further adjustments to the system 800 via the DPC
802 are made at
regular intervals in the following manner: as temperature within the space
defined by the eye shield
200 falls below the dew point temperature threshold, the system 800 increases
power to the
heating element 202 via circuit wires 212, 214, and as temperature within the
space defined by the
eye shield climbs above the dew point temperature threshold, the system
decreases power to the
heating element via the circuit wires. The aforementioned operation may employ
hysteresis, such as
used on a typical thermostat, between the increase and decrease states of the
system 800 to avoid
unwanted rapid switching.
MULTIPLE-REGION, MULTIPLE-PWM EMBODIMENT
[071] Referring to FIG. 3, there is provided in accordance with part of
another, second,
embodiment of the invention, an eye shield lens or protective eyewear 300
adapted for at least
partially defining an enclosure around a user's eyes and having thereon a
plurality of regions or
zones of resistive film heating elements or members 302, 304, 306. The film
heating element 302
located over a user's right eye during use, is connected to the power source
(not shown) by a bus-
bar 308 positioned along an upper edge of the film and electrically connected
between the film and
a lead wire 310 leading to a terminal of the power source. The film heating
element 304 located
centrally of the eye shield lens 300 just above a user's nose during use, is
connected to the power
source by a bus-bar 312 positioned along an upper edge of the film and
electrically connected
between the film and a lead wire 314 leading to a terminal of the power
source. The film heating
element 306, located over a user's left eye during use, is connected to the
power source by a bus-
bar 316 positioned along an upper edge of the film and electrically connected
between the film and
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a lead wire 318 leading to a terminal of the power source. A buss-bar 320
positioned along the
lower edge of each of the film elements 302, 304, 306 interconnects the film
elements to the ground
terminal of the power source.
[072] As shown, the surface area of the film members 302, 306 is larger than
the surface
area of the film member 304, such that the resistance of the film member 304
is less than that of the
other film members. Accordingly, in order to have even heating across the
entire lens 300, less
current should be applied to the film member 304 than the other film members.
Or, alternatively,
the divisions between the film members would allow independent heating of one
or more of the film
members, more or less, than the other film members.
[073] Referring to FIG. 4, an eye shield lens 400 is provided in accordance
with the second
embodiment of the invention. The eye shield 400 is adapted for at least
partially defining an
enclosure in front of the user's eyes and has deposited thereon a plurality
(24 are shown in FIG. 4) of
resistive heating film zones or regions 402 A-X. It will be appreciated that
the resistive heating film
may be divided into larger or smaller regions than shown without departing
from the true scope and
spirit of the invention. Each resistive film region 402 A-X is connected to a
terminal of a power
source via lead wires and discrete buss-bars 404 a-x. A single buss-bar 406,
located along a lower
edge of each resistive film region 402 A-X interconnects each of the lower
ends of film regions to a
ground terminal of the power source.
[074] The resistive film regions of the fog prevention system of the present
invention are
preferably deposited on the inner surface of an eye shield 200, 300, 400 with
a process known as ion
sputtering on a polycarbonate lens, but spray coating and other methods and
materials known in the
art may be used without departing from the true scope and spirit of the
invention. The buss-bars
are deposited on the lens 200, 300, 400 by stamping, adhesive backing, or in
the case of a
conductive silver epoxy buss-bar, it may be applied to a polycarbonate
substrate. In the case of a
dive mask, while attachment of the resistive film and buss-bars to the inner
glass surface of the mask
may be employed, a preferred alternative would be to apply these to an inner
polycarbonate
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substrate within the mask. The methods and systems of application of the
resistive film heaters and
the buss-bars to various substrates are known in the art. Each buss-bar and
its corresponding
resistive film region are overlapped on edge portions of each so that they
conduct electricity to and
from the power source as is known in the art.
CAM and DPC in a Multiple-Region Embodiment
[075] The larger number of resistive film regions 302, 304, 306 in the
multiple-region
embodiment of the invention shown in FIG. 3, and alternatively the larger
number of regions 402 A-X
in the multiple-region embodiment of the invention shown in FIG. 4, enables
more even heating of a
wider variety of shapes and sizes of eye shields 300, or alternatively 400,
and requires a
correspondingly larger number of Pulse-Width Modulators (PWMs), or PWM
channels, in a multiple-
region, multiple-PWM eye shield fog prevention system as shown in FIGS. 9 and
10. Thus, it will be
appreciated that, while a three-channel PWM system is shown in FIGS. 9 and 10,
fewer or more
channels may be provided to accommodate a like number of resistive heating
element regions by
using an appropriate number PWM channels to accommodate such a plurality of
heating element
regions.
[076] As shown in FIGS. 9 and 10, a current adjustment means (CAM) may be
employed with
a multiple-region embodiment of the invention, and as shown in FIG. 10, a dew
point calculation
means (DPC) may also be incorporated into a multiple-region embodiment of the
invention to
enable automated adjustment of each region as described above. In the case of
the CAM, the single
output voltage of the CAM is received by a region profile control means (RPC)
as further described
below and used to adjust the input voltage to each of the multiple PWMs in
that embodiment to
allow varying of the current out of the PWM based upon user adjustment of a
selector or to enable
automation as further described below. The DPC of the multiple-region
embodiment of the
invention functions the same way as described above for the DPC in a single-
region embodiment of
the invention.
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Balancing Profiles and Custom Profiles
[077] Referring now to FIG. 9, a multiple-PWM, multiple-region fog prevention
system 900 is
shown comprising a power source 505' having positive and negative terminals
510', 512', circuit
wires 212', 214', a multiple-channel PWM 502' which is shown generating
signals 503a, 503b and
503c on channels a, b and c, respectively, a CAM 702', a plurality of MOSFETs
602', one MOSFET for
each channel of the multiple-channel PWM, an eye shield or lens 300 and
heating element regions
302, 304, 306, which system is similar to the single-PWM systems described
above, except that
system 900 further comprises a region profile controller 902 primarily for
balancing power delivered
to different-sized and shaped resistive heating film regions (302, 304, 306,
or alternatively, 402 A-X),
on the eye shield 300 or 400, respectively.
[078] Differently shaped eye shield lenses 300, 400 would require
corresponding region
profiles that reflect the shape of the lens and its individual regions such
that the electrical
characteristics of each region are appropriately weighted so that each region
is assured the proper
amount of power to keep it in balance with other regions. Thus a region
profile is tied to the shape
of a region (and the resulting electrical resistivity of that region) and the
overall shape of the goggle.
If one were to change the shape of a lens, then a different profile would be
required for that lens.
Calculating the Resistance of Regions
[079] Each of the regions 302, 304 and 306 have a calculated total electrical
resistance (Rt)
determined by a formula which considers the type of resistive coating used,
and the area of the
region where: Rt is the total resistance of the region in ohms, Ri is the
resistance per square inch of
the resistive thin film in ohms, H is the height of the region in inches and W
is the width of the region
in inches. Rt may be calculated using the following formula:
Ri * H
Rt = ________________________________________
W
[080] For example, considering the regions 302 and 306, given Ri is 10 ohms, H
is 3 inches,
and W is 3 inches. The total resistance (Rt) for each region 302 and 306 may
be calculated as (10 x 3)
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/ 3 which equals 10 ohms. Now considering region 304, given an Ri of 10 ohms,
H being 2 inches,
and W being 1.6 inches, the total resistance (Rt) of the region 304 may be
calculated as (10 x 1.6)! 2
which equals 8 ohms. Thus, for a given voltage, due to a lower total
resistance in 304 than in regions
302, 306, more power would be consumed in region 304 than in regions 302 and
306 causing a hot
spot in region 304 as further verified below.
Calculating the Power Density of Regions
[081] Each region 302, 304, 306 has a calculated Power Density (Pd) determined
by a
formula which considers the effective voltage (E) applied to the region, the
resistance per square
inch (Ri) of the resistive thin film in ohms, and the width (W) of the region
in inches. Pd may be
calculated using the following formula:
E2
Pd = Ri * W2
[082] For example, considering regions 302 and 306, given an operating voltage
of 10 volts
for each region, Pd would equal 102/ (10 x 32) which equals 1.11 watts per
square inch. Considering
region 304, given the same operating voltage of 10 volts, region 304 Pd would
equal 102/ (10 x 22)
which equals 2.5 watts per square inch. These calculations show that, given an
equal effective
voltage for all regions, the center region 304 will be hotter than the outside
region 302 and
306.
Determining Region Profile Proportional Control
[083] Given the aforementioned determined hot spot over the nose of the user,
proportional balancing of the regions is desirable. Such balancing requires a
determination
of an appropriate voltage level for region 304 which will provide the same
power level
output as regions 302 and 306 when powering regions 302 and 306 at 10 volts.
Previously,
according to the formula,
E2
________________________________ = 1.11 (Pd same as 302)
Ri * W2
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and solving for E,
E = 1 Ri * W2 * Pd
and plugging in known values, E is equal to
110 * 22 * 1.11 which is equal to 6.66 volts.
[084] Therefore, based on the width and height of the same material used in
regions
302 and 306, to produce an equivalent power density, region 304 will need .666
times (or
66.6%) of the voltage applied to regions 302 and 304. This result is confirmed
by re-
calculating the power density (Pd) for region 304 as 6.662/ (10 x 22) which
equals 1.11 watts per
square inch.
[085] Applying these calculations back to the reference output voltage
produced by
the CAM 702' on channels a and c, delivered to regions 302 and 306
respectively, will also
require reduction of the reference output voltage on channel b by 66.6%
compared to the
values applied to channels a and c. In the case of analog circuitry this
proportional control
may be accomplished by use of a resistor network as will be appreciated by
those of
ordinary skill in the art. In the case of a digital implementation the values
will be retrieved
from a data table and the resulting power levels will be calculated and
applied directly to
the PWM channels using a microcomputer or equivalent digital circuitry as will
be apparent
to those of ordinary skill in the art.
Region Profile Matched to Shape or Region
[086] Accordingly, it should be understood that when a larger region or
regions
receive 100% of the applied effective voltage, smaller regions should receive
a
proportionally smaller percentage of the applied effective voltage to balance
the power
density of all of the regions. While a specific example for a particularly
shaped goggle has
been provided, it will be appreciated that differently-shaped lens regions
will require similar
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calculation and balancing profile determination. In the case of curved edge,
or irregularly
shaped regions, determination of region areas may require the application of
known
mathematical methods to determine the region area for use in the above-
described
calculations.
Balanced and Custom Profiles
[087] The results in the foregoing example disclose a balancing profile. More
precisely, these results yield the analog or digital proportional input
voltages needed to
power differing size regions on a specific goggle to the same power densities.
Region Custom Profile Switch and Automation
[088] Referring to FIG. 10, a multiple-PWM, multiple-region fog prevention
system 1000
similar to system 900 is shown comprising a power source 505' having positive
and negative
terminals 510', 512', circuit wires 212', 214', a multiple-channel PWM 502'
which is shown
generating signals 503a, 503b and 503c on channels a, b and c, respectively, a
CAM 702', a plurality
of MOSFETs 602', one MOSFET for each channel of the multiple-channel PWM, an
eye shield or lens
300 and heating element regions 302, 304, 306. System 1000 differs from system
900 in that in
system 1000 the RCP 902 further comprises a user-selectable region profile
control switch 1002
which enables a user to select a balanced profile or one of several custom
profiles for customized
power delivery as further described below to the different-sized and shaped
resistive heating film
regions (302, 304, 306, or alternatively 402 A-X) on the eye shield 300 or
400, respectively.
[089] A custom profile may be used to enable predetermined proportional input
voltages to
a particular resistive film region, or regions, necessary to achieve a desired
power density pattern
allowing one or more regions 302, 304, 306, or alternatively 402 A-X, to
intentionally become hotter
or cooler than other regions for specific intended purposes. Together with the
DPC 802' and sensors
804', 806', the CAM 702' provides overall automatic variability between all
the way cool to all the
way hot for each of the regions 302, 304, 306, or alternatively regions 402 A-
X, and it is the job of
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the RPC 902' cognizant of the profile to know how much power to apply
proportionally to each of
the regions in accordance with the overall adjustment. For example for a given
dew point
calculation, the CAM 702' may be set to a 50% overall power application or
duty cycle, the RPC will
put out a 50% adjustment for the largest region 302, 304, 306 (or
alternatively 402 A-X) and a
proportionally smaller output for smaller regions in accordance with a
particular predetermined
profile.
[090] Examples of custom profiles may involve a profile for a snow boarder
that may require
added heat to one side of a goggle lens to prevent fogging or to reduce icing
of that side depending
upon which foot the rider usually leads downhill, or as another example, a
particular lens or goggle
shape and configuration may require added heating at the edges of the goggle
to prevent fogging or
icing. Alternatively, further it would be desirable to provide custom settings
for particular weather
conditions, such as a rainy day, a snowy day, a sunny day, or different depths
and water
temperatures for a dive mask, etc. Custom profiling may be user-selectable
with the custom profile
switch 1002.
[091] The multiple-PWM, multiple-region fog prevention system 1000 shown in
FIG. 10 also
further comprises means for calculating dew point 802' (also known as the dew
point calculator, or
DPC), a temperature sensor 804' and a relative humidity sensor 806'
operatively connected to the
DPC via signal means 807', 809' for automated control of the system 1000. The
DPC 802' and
sensors 804', 806' are for the same purposes and function in the same way as
the DPC 802 and
sensors 804, 806 shown and described above in connection with the first
embodiment of the
invention, except the signals from the DPC 802' are used by the CAM and RPC to
provide master
controls for a plurality of signal lines a, b, c to the PWM 502'.
[092] From the foregoing it can be seen that many of the aspects of the
invention, such as
dew point calculation, automation and current adjusting means may be employed
to either of the
first or second embodiments of the invention, whereas the RPC is primarily
adapted for the second
embodiment of the invention employing a plurality of regions on the eye
shield.
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SYSTEM OVERVIEW
[093] While preferably the PWMs of either embodiment of the invention, and
associated
functions such as dew point calculation, profile table lookup, variable
current adjustment
mechanism, switching means, and the like, may be preferably accomplished with
a microcomputer,
any of these functions may be performed with other technology, such as a
programmable logic array
(PLA), a state machine, analog circuitry or other digital logic, without
departing from the true scope
and spirit of the invention.
[094] Referring to FIG. 11, there is provided a preferred embodiment of a
digital version of a
multiple-channel PWM, multiple-region fog prevention system 1100. System 1100
comprises a
power source, such as rechargeable batteries 1102, an on/off switch 1104, a
heat control switch
1106, a profile selector 1108 and a charger jack 1110. Charger jack 1110 may
comprise a mini-USB
charger jack or other suitable charging system as known in the art. System
1100 further comprises a
power level indicator display 1112 preferably comprising a plurality of LEDs
configured as a bar
graph to indicate a selected power level and a battery life indicator display
1114 preferably
comprising a plurality of LEDs configured as a bar graph to indicate remaining
battery life. System
1100 further comprises an eye shield 1116 having deposited thereon a plurality
of thin film heating
elements 1118, 1120, 1122. The eye shield 1116 is adapted for defining at
least a partial enclosure
in front of a user's eyes. A temperature sensor 1124 and a relative humidity
sensor 1126 are
positioned within the partial enclosure defined by the eye shield 1116 for
aiding with calculation of
dew point temperature.
[095] The system 1100 further preferably comprises a low-power microcontroller
1128
preferably further comprising PWM logic, other programmable logic and some
combination of
RAM/ROM/FLASH Memory 1130 as is known in the art of microelectronics. The
microcomputer
controller 1128 is operatively connected to a battery charger circuit 1132.
The battery charger
circuit 1132 is connected to the battery charger jack 1110 and rechargeable
batteries 1102. The
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battery charger circuit 1132 is primarily responsible for maintaining the
rechargeable batteries 1102,
including routing a charge from the charger jack 1110 to the rechargeable
batteries when required
and turning off, disconnecting the charger from the batteries when they have
been fully charged and
reporting battery level to the microcontroller 1128. The system 1100 further
comprises battery life
indicator display logic 1134 such that when the microcontroller 1128 receives
battery level
information from the battery charger circuit as previously described, the
microcontroller may signal
the battery life indicator display logic upon user request or otherwise. The
battery life indicator
display logic 1134 converts the signal received from the microcontroller 1128
into the logic
necessary to drive the battery life indicator display 1114. The battery life
indicator display logic 1134
may include a latch to hold the latest value on the display, relieving the
microcomputer to attend to
other tasks.
[096] The system 1100 further comprises an eye shield heater driver 1136
comprising a
plurality of driver channels 1138, 1140, 1142, each channel corresponding to a
thin film heating
element region or zone, such as regions 1118, 1120, 1122, respectively. The
primary responsibility
of the microcontroller 1128 is to keep the heater driver 1136 and related
channels 1138, 1140, 1142
operating at an optimal and preferably balanced level to eliminate and prevent
fogging while
conserving battery life. The microcontroller 1128 may operate in manual heat
control or automatic
heat control modes. In the manual heat control mode, responsive to an input
from the more or less
heat switch 1106, the microcontroller 1128 adjusts power to the eye-shield
heater driver 1136
according to a predetermined profile contained in microcontroller memory 1130
and which controls
the duty cycle signal on each individual PWM channel in a manner consistent
with the size, shape
and electrical resistivity of each associated heating element 1118, 1120, 1122
to provide power
density balancing.
[097] In the situation where some other custom profile, other than power
density balancing,
is desired, responsive to input from profile selector switch 1108, the system
1100 may engage a
custom profile, also stored in microcontroller memory 1130, resulting in
application of a custom
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power density profile to the heater driver 1136 resulting in a desired portion
of the eye shield 1116
receiving more power than another portion.
[098] The system 1100 further comprises a dew point calculator (DPC) 1144
which calculates
dew point temperature from temperature sensor 1124 and relative humidity
sensor 1126. During
automatic mode balancing of heating levels of the system 1100, the system
adjusts the heat to the
regions in accordance with a calculated dew point from the DPC 1144. When the
system 1100 is
initially started, the DPC 1144 calculates the dew point temperature and
compares it to the actual
temperature within the space defined by the eye shield 1116 and signals the
microcontroller 1128
accordingly. If the dew point temperature, as calculated by the DPC 1144, is
greater than the
temperature within the space defined between the eye shield 1116 and a user's
eyes, then logic
within the microcontroller signals to the eye shield heater driver 1136 to
increase the duty cycle of
the PWM channels in accordance with the profile in effect to increase the
temperature of the eye
shield 1116 and the space between the eye shield and a user's eyes. Thus,
subsequent sensory
input to the DPC 1144 from the temperature sensor 1124, the relative humidity
sensor 1126, and
calculations by the microcontroller 1128, would all reflect not only changing
ambient conditions, but
temperature changes resulting from the aforementioned increase request from
the system 1100 as
well. Further adjustments to the system 1100 via the DPC 1144 are made by the
microcontroller
1128 at regular intervals in the following manner: as temperature within the
space defined by the
eye shield 1116 falls below the dew point temperature threshold, the system
1100 increases power
to the heating elements 1118, 1120, 1122 via PWM channels 1138, 1140, 1142,
and as temperature
within the space defined by the eye shield climbs above the dew point
temperature threshold, the
system decreases power to the heating elements via the PWM channels. The
aforementioned
operation may employ hysteresis, such as used on a typical thermostat, between
the increase and
decrease states of the system 1100 to avoid unwanted rapid switching.
[099] In both the manual and automatic operation modes of the system 1100, it
is
preferable for the user to be apprised of the power level being supplied to
the heating elements of
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the system. This is especially useful in the manual mode when the user may set
the power at a
predetermined level in accordance with visual feedback from the power level
display. In response to
manual changes from the more/less heat switch 1106, and/or at regular
intervals, the
microcontroller 1128 determines from memory 1130 the current operating power
level being
supplied to the heater driver 1136 and sends a power level signal to the power
level display logic
1146, which in turn converts the signal received from the microcontroller 1128
into the logic
necessary to drive the power level indicator display 1112. The power level
indicator display logic
1146 may include a latch to hold the latest value on the display, relieving
the microcomputer to
attend to other tasks.
PRIOR VOLTAGE REGULATION SYSTEM
[100] Referring now to FIG. 12, a block diagram of a battery regulation system
is illustrated
for maintaining a constant regulated voltage to a hand-held electronic device,
such as a cell phone
(represented by load 1235), including a lithium-ion battery 1205, a positive
circuit wire 1210 carrying
3.7 to 3.2 Volts DC, which is depleting with battery discharge over time in
use as specified, to a
voltage regulator 1225. The voltage regulator 1225 is set to supply a
regulated, constant 3.0 Volts
DC via line 1230 as specified to the load 1235. A typical voltage regulator
supplies voltage at the
desired output level only when the actual supply voltage from the battery is
somewhat greater than
the desired output voltage. Thus, for example, where the desired output
voltage is to be 3.0 Volts
DC, the battery voltage would need to be at least 3.2 Volts DC for the voltage
regulator to produce
the desired 3.0 Volts DC. The circuit back to the negative terminal of the
battery 1205 is completed
with circuit line 1220, and the system is grounded at 1240. Such a system is
known to be important
to provide constant voltage necessary to efficient functioning of cell phones.
BATTERY COMPENSATION SYSTEM USING PWM
[101] Unlike the aforementioned battery regulation system 1200 shown and
described
above, a battery compensation system using PWM differs in that it does not
maintain a constant
voltage until the battery is discharged, but rather it varies the PWM cycle to
maintain constant
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power to the load despite the voltage drop until the battery is discharged and
no longer able to
maintain that power level.
[102] Thus, referring now to FIG. 13, a battery compensation system 1300 using
pulse-width
modulation (PWM) 1340 is shown comprising a battery 1305, preferably a lithium-
ion battery,
having positive parallel circuit lines 1380 leading to a voltage divider
circuit 1310, 1315 for
proportionally adjusting the voltage to a measurable range, an analog to
digital converter 1335 for
receiving the output from the voltage divider and converting it into a digital
voltage value, a
microprocessing unit (MPU) 1330 and a single-channel pulse-width modulator
(PWM) 1340.
Preferably, the voltage divider circuit 1310, 1315 comprises two resistors
1310, 1315 in series
between positive and negative terminals of the battery 1305 for proportionally
adjusting the voltage
to a measurable range, the voltage divider circuit preferably having a tap
between the two resistors
(shown as the intersection of lines between the two resistors 1310, 1315)
adapted to provide the
proportional voltage measurement to an I/O pin on the analog-to-digital
converter 1335. Preferably,
the user-determined, or provided, power setting comprises a power level
setting set by a dial, a
knob, or a push button system 1325, together with some form of visual feedback
to the user (e.g.,
1612 of FIG. 16) to further enable selection of the setting.
[103] The PWM 1340 drives the load 1345, which represents a portable
electronic device, or
elements of a portable electronic device, such as for example heating elements
on an anti-fog ski
goggle, a heated diving mask, a heated medical or technical eye shield, or the
like. Alternatively, the
load 1345 may represent a heater on a portable electronic device such as a
hand-held GPS unit, a
cell phone, a radio, an electronic tablet, a reader, or other portable
computer or the like, to be
driven by the PWM circuitry and battery of the device. A power level selector
1325 is provided with
more and less controller for allowing user selection of a desired power
setting, such as 20%, 40%,
60%, 80% 100%, corresponding to, for example, 2 Watts, 4 Watts, 6 Watts, 8
Watts and 10 Watts
respectively 1350, 1355, 1360, 1365, 1370 respectively, for power to drive a
heater (e.g., heating
element 202 of FIG. 5) on the powered electronic device (e.g., an anti-fog
goggle). The MPU 1330 is
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one of several possible means for receiving voltage input and user-determined
power setting input
for determining a compensating duty cycle 1350, 1355, 1360, 1365, 1370 for
application to the PWM
1340 to drive the load consistently at the user-determined power setting
despite decrease in voltage
from the battery 1305 resulting from battery depletion.
[104] Referring now also to FIG. 14, the MPU 1330 is capable of executing
software code
steps 1400 as set forth in the flow chart, to determine a compensating duty
cycle 1350, 1355, 1360,
1365, 1370 for application by the software to the PWM 1340 to drive the load
1345 consistently at
the user-determined power setting despite decrease in battery voltage
resulting from depletion of
the battery 1305. For this embodiment of the invention, preferably the MPU
1330 is battery-
powered, and a readily-available microprocessing unit having on-board analog-
to-digital conversion
means 1335 may be used for the present invention.
[105] The software steps as shown at 1405 for operation of the invention
comprise, after
starting at 1405, reading of the battery voltage 1410, reading the user
setting for power level 1415,
looking up the battery voltage compensation value for a PWM duty cycle 1420 to
be applied to the
PWM circuit 1425. The process ends at 1430, and the steps 1400 are repeated
frequently as needed
to maintain compensated power in accordance with the invention during
operation of the system.
While the portable electronic device 1345 (e.g., 200 of FIG. 5) is powered on,
the compensation
system of the invention may be operated continuously, or it may be controlled
with an on/off switch
to toggle between battery conservation mode and battery compensation mode. As
indicated by line
1430 for as long as the device power is on and the battery is sufficiently
charged and capable of
supplying the power necessary to power the device in battery compensation
mode. While battery
conservation mode will use less battery power, battery compensation mode in
accordance with the
invention may be employed when extra battery power is available to compensate
for a drop in
voltage resulting from battery depletion by increasing the duty cycle 1350,
1355, 1360, 1365, 1370
to be applied to the PWM 1340 to overcome what would otherwise be a drop in
power associated
with the depleted battery 1305.
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[106] Still further, as shown in FIGS. 14 and 15, determination of a
compensating duty cycle
1350, 1355, 1360, 1365, 1370 may comprise a data lookup table 1500 of PWM duty
cycle values
organized according to power setting (shown in Watts across the top of the
table 1500) and battery
depletion voltage drop (shown in the left-hand column of FIG. 15) and for use
by the code steps
1410, 1415, 1420, 1425 run by the microprocessor to select a compensating duty
cycle for
application to the PWM to drive the load 1345 consistently at the user-
determined power setting
despite a decrease in voltage from the battery 1305 resulting from battery
depletion. This
embodiment of the invention preferably comprises a lookup table 1500 stored in
microprocessor
memory (e.g., 1630 of FIG. 16) which, as is true of software data table
controls in general, provides
generally faster operation and is easier to code than using floating-point
calculations, though it will
be appreciated that either may be used to implement the invention in
accordance with its true spirit
and scope. Further, while conceivably a discrete logic circuit could be used
to perform the functions
of the compensation system of the invention, such would likely be unduly
expensive to implement
and no more effective than the software and data table lookup functions that
are preferred for the
invention.
[107] The data lookup table 1500 shown in FIG. 15 is organized by user heater
level setting
(shown in Watts across the top of the table 1500) and actual heater power for
a given battery
voltage ranging from 8.4 Volts DC (assuming two lithium-ion batteries of 3.7
Volts DC each in series)
depleted down to 6.8 Volts DC (shown in the left-hand column of the table
1500). Thus, for
example, when the battery 1305 is at full power (that is there has been no
depletion of battery
charge yet), and 2 Watts of total power has been selected by a user, 11.3 on
cycles (out of 100.0
total cycles) will need to be on. As can be seen from the FIG. 15, the number
of duty cycles increases
as shown as a greater number of Watts is specified by the user, and a larger
number of duty cycles is
required to compensate for increasingly depleted charge in the battery. Thus
for example, 86.5 duty
cycles (that is PWW will switch the power on 86.5 cycles for every 100 cycles
¨ or in other words the
PWM controls transmission of power to allow power to the load 86.5 cycles out
of a hundred, or
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86.5 on and 13.5 off). Thus, as can be seen the number of duty cycles required
increases as the
battery depletes further and the higher the power level selected by the user.
While the example
data table 1500 is based upon a system using two lithium-ion batteries of 3.7
Volts DC each in series,
the invention is not limited to a two-battery, or otherwise plural-battery,
system, and the battery
compensation system of the invention may be used with a single battery with an
appropriately
adjusted data table, or calculations as the case may be. Further, while the
number of duty cycles is
represented as an integer with a decimal portion, these numbers may be rounded
to the nearest
integer in an actual PWM implementation.
[108] In an alternate embodiment, the software steps 1410, 1415, 1420, 1425
themselves
may be used to calculate a compensating duty cycle 1350, 1355, 1360, 1365,
1370 for application to
the PWM 1340 to drive the load 1345 consistently at the user-determined power
setting despite
decrease in voltage from the battery 1305 resulting from battery depletion.
The formula for
determining the compensating duty cycle 1350, 1355, 1360, 1365, 1370 for this
embodiment of the
invention, which is the same formula used to determine data table 1500 duty
cycle values (from user
input power settings ¨ represented by the Watts settings across the top of
table 1500 ¨ and
measured voltage) used in the table is as follows:
Desired Power*Load Resistance
Duty Cycle = _________________________________________ * 100
(Battery Voltage)2
[109] The compensation system 1300 in accordance with the invention enables
maintenance
of a user-selected and/or desired power setting to drive the load 1345 to
consistently heat a
portable device (e.g., goggle lens 200 of FIG. 5), such as anti-fog goggles or
a hand-held GPS, radio or
phone, despite partial depletion of a device battery 1305, as long as there is
sufficient battery charge
to maintain the system-compensated power output. Thus, as the voltage from the
battery 1305
drops resulting from battery depletion from use over time, the system 1300
compensates by
increasing the duty cycle 1350, 1355, 1360, 1365, 1370 of the PWM 1340 driver
for the device 1345.
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[110] Referring now to FIG. 16, there is shown a compensation system 1600
adapted for use
preferably in heating a plurality of devices, for example a plurality of loads
1618, 1620, 1622 of a
portable electronic device 1616. The plurality of loads 1618, 1620, 1622
represent a portable
electronic device, elements of a portable electronic device, or a plurality of
such devices, such as
heating elements on an anti-fog ski goggle, a heated diving mask, a heated
medical or technical eye
shield, or the like. Alternatively, the load 1345 may represent a heater or
other appropriately PWM
driven element on a portable electronic device such as a hand-held GPS unit, a
cell phone, a radio,
an electronic tablet, a reader, or other portable computer or the like, to be
powered by the PWM
circuitry and battery of the device. The example compensation system 1600
comprises a power
source, such as rechargeable batteries 1602, an on/off switch 1604, a power
level control 1606 and a
charger jack 1610. Charger jack 1610 may comprise a mini-USB charger jack or
other suitable
charging system as known in the art. System 1600 further comprises a power
level indicator display
1612 preferably comprising a plurality of LEDs configured as a bar graph to
indicate a selected power
level and a battery life indicator display 1614 preferably comprising a
plurality of LEDs configured as
a bar graph to indicate remaining battery life. System 1600 further comprises
a portable electronic
device 1616 having illustrated therewith a plurality of loads 1618, 1620,
1622.
[111] The system 1600 further preferably comprises a low-power microcontroller
1628
preferably further comprising PWM logic, other programmable logic and some
combination of
RAM/ROM/FLASH Memory 1630 as is known in the art of microelectronics. The
microcomputer
controller 1628 is operatively connected to a battery charger circuit 1632.
The battery charger
circuit 1632 is connected to the battery charger jack 1610 and rechargeable
batteries 1602. The
battery charger circuit 1632 is primarily responsible for maintaining the
rechargeable batteries 1602,
including routing a charge from the charger jack 1610 to the rechargeable
batteries when required
and disconnecting the charger from the batteries when they have been fully
charged and reporting
battery level to the microcontroller 1628. The system 1600 further comprises
battery life indicator
display logic 1634 such that when the microcontroller 1628 receives battery
level information from
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the battery charger circuit as previously described, the microcontroller may
signal the battery life
indicator display logic upon user request or otherwise. The battery life
indicator display logic 1634
converts the signal received from the microcontroller 1628 into the logic
necessary to drive the
battery life indicator display 1614. The battery life indicator display logic
1634 may include a latch to
hold the latest value on the display, relieving the microcomputer to attend to
other tasks.
[112] The system 1600 further comprises drivers 1636 comprising a plurality of
driver
channels 1638, 1640, 1642, each channel corresponding to a load, such as loads
1618, 1620, 1622,
respectively. Preferably, MOSFET for system 1600 is contained in the drivers
1636. The primary
responsibility of the microcontroller 1628 is to keep the driver 1636 and
related channels 1638,
1640, 1642 operating at an optimal and preferably balanced level while
conserving battery life.
Responsive to an input from the power level control 1606, the microcontroller
1628 adjusts power
to the device driver 1636 according to a predetermined profile contained in
microcontroller memory
1630 and which controls the duty cycle signal on each individual PWM channel
in a manner
consistent with the size, shape and electrical resistivity of each associated
load 1618, 1620, 1622 to
provide power density balancing.
[113] In the situation where some other custom profile, other than power
density balancing,
is desired, the system 1600 may engage a custom profile, which may be stored
in microcontroller
memory 1630, resulting in application of a custom power level profile to the
driver 1636 resulting in
a desired portion of the portable electronic device 1616 receiving more or
less power than another
portion.
[114] The system 1600 using pulse-width modulation (PWM) (contained in the
microcontroller 1628 comprises a voltage divider circuit 1610 for
proportionally adjusting the
voltage to a measurable range, and an analog to digital converter (ADC) 1605
preferably contained in
the microcontroller 1628 for receiving the output from the voltage divider and
converting it into a
digital voltage value. Preferably, the voltage divider circuit 1610 comprises
two precision resistors in
series (as described above in connection with FIG. 13) between positive and
negative terminals of a
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battery or batteries 1602 for proportionally adjusting the voltage to a
measurable range, the voltage
divider circuit preferably having a tap between the two resistors adapted to
provide the proportional
voltage measurement to an I/O pin on microcontroller 1628 containing the
analog-to-digital
converter 1605. Preferably, the user-determined, or provided, power setting
comprises a power
level setting set by a dial, a knob, or a push button system (e.g., 1606),
together with some form of
visual feedback to the user (e.g., 1612) to further enable selection of the
setting.
[115] As part of system 1600, it is preferable for the user to be apprised of
the power level
being supplied to the load elements of the system. Thus, a user may select a
desired power level in
accordance with visual feedback from the power level display 1612. In response
to manual changes
from the power level control 1606, and/or at regular intervals, the
microcontroller 1628 determines
from memory 1630 the current operating power level being supplied to the
driver 1636 and sends a
power level signal to the power level display logic 1646, which in turn
converts the signal received
from the microcontroller 1628 into the logic necessary to drive the power
level indicator display
1612. The power level indicator display logic 1646 may include a latch to hold
the latest value on the
display, relieving the microcomputer to attend to other tasks.
[116] Referring now to FIG. 17, there is shown an alternate data lookup table
1700 stored in
microprocessor memory 1630 for allowing software determination of an applied
duty cycle
corresponding to a custom power level profile, for example for each load of a
plurality of different
loads, in a portable electronic device, for example when less than full power
to the device may be
desirable. The data lookup table 1700 shown in FIG. 17 is organized by user
heater level setting
(shown in Watts across the top of the table 1700) and actual heater power for
a given battery
voltage ranging from 8.4 Volts DC (assuming two lithium-ion batteries of 3.7
Volts DC each
connected in series) depleted down to 6.8 Volts DC (shown in the left-hand
column of the table
1700). Thus, for example, when the battery 1602 is at full power (that is
there has been no
depletion of battery charge yet), and 1.5 Watts of total power has been
selected by a user, 8.5 on
cycles (out of 100.0 total cycles) will need to be on. As can be seen from the
FIG. 17, the number of
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duty cycles increases as shown as a greater number of Watts is specified by
the user, and a larger
number of duty cycles is required to compensate for increasingly depleted
charge in the battery.
Thus for example, 64.9 duty cycles (that is PWW will switch the power on 64.9
cycles for every 100
cycles ¨ or in other words the PWM controls transmission of power to allow
power to the load 64.9
cycles out of a hundred, or 64.9 on and 35.1 off). Thus, as can be seen the
number of duty cycles
required increases as the battery depletes further and the higher the power
level selected by the
user. While the example data table 1700 is based upon a system using two
lithium-ion batteries of
3.7 Volts DC each in series, the invention is not limited to a two-battery, or
otherwise plural-battery,
system, and the battery compensation system of the invention may be used with
a single battery
with an appropriately adjusted data table, or calculations as the case may be.
Further, while the
number of duty cycles is represented as an integer with a decimal portion,
these numbers may be
rounded to the nearest integer in an actual PWM implementation.
[117] The table 1700 may be part of a more comprehensive data table and still
fall within the
true scope and spirit of the invention, however it is contemplated that the
system 1600 will
ascertain the battery voltage and the user-determined power level input, and
determine the
appropriate duty cycle according to those inputs and in harmony with either an
even power level
profile, or alternatively a custom power level profile, such as would the be
case for example in an
evenly-heated eye shield device or a custom-heated eye shield device described
previously for
example in connection with FIG. 11.
[118] While a preferred embodiment of the present invention has been shown and
described, it will be apparent to those skilled in the art that many changes
and modifications may be
made without departing from the invention in its broader aspects. For example,
it will be
appreciated that one of ordinary skill in the art may mix and match the
various components of the
various embodiments of the invention without departing from the true spirit of
the invention as
claimed. Thus, by way of example, it will be appreciated that while the system
1100 discloses a
preferred way of accomplishing the purposes of invention, it will be
appreciated by those of ordinary
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PCT/US2014/059040
skill in the art that other combinations of microcontrollers and/or
microcontrollers may be used to
accomplish the purposes hereof without departing from the true scope and
spirit of the invention.
The appended claims are therefore intended to cover all such changes and
modifications as fall
within the true spirit and scope of the invention.
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