Note: Descriptions are shown in the official language in which they were submitted.
CA 2,869,544
CPST Ref: 11744/00002
1 A SOFTWARE CONTROLLED POWER SUPPLY
2
3 FIELD OF THE INVENTION
4 [0001] The present invention relates to power supplies, and more
particularly to a
software-controlled power supply.
6
7 BACKGROUND OF THE INVENTION
8 [0002] Pulse frequency modulated power supplies are common for
producing the
9 fixed voltage DC output required to charge battery powered mobile devices
from a variety of AC
inputs. While smaller, more flexible, and more efficient than simple
transformer power supplies,
11 pulse frequency modulated power supplies are still active mechanisms
that consume power.
12 With the growth of mobile devices, now numbering in the billions,
cumulative standby power
13 consumption by charging power supplies is becoming a problem. The
problem being that power
14 supplies that remain attached to a power source consume standby power in
order to remain
active and achieve regulated output voltage.
16 [0003] Furthermore, power supplies that remain attached to both a
power source
17 and to a charged device consume additional standby power because the
coupled device
18 continues to draw trickle power, even when fully charged. This wasted
power is costly to both
19 individual device owners and to society as a whole.
[0004] Figure 1 illustrates a prior art fixed voltage power supply using
DC/DC pulse
21 frequency modulation. The high voltage DC current, which can be created
by rectifying high
22 voltage AC current (not shown), powers charge pump oscillator (101)
operating at a high
23 frequency (typically 50-150 kHz).
24 [0005] The charge pump oscillator (101) controls the gate of MOSFET
(102), which
in turn, induces a high frequency, high voltage AC signal from the DC supply
current through
26 transformer (103). Transformer (103) outputs a magnetically isolated
high frequency, low
27 voltage AC signal, rectified by diode (104). Rectifier (104) feeds bulk
capacitor (105), which
28 removes ripple from the low voltage rectified signal, producing a DC
output.
29 [0006] The Zener diode network (106) allows current to flow through
the LED of
optical isolator (107) when the output voltage exceeds the Zener threshold.
Optical isolator
31 (107), when illuminated, disables the output of the AC waveform from
charge pump oscillator
32 (101) to MOSFET (102) and through transformer (103). With charge pump
oscillator (101)
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1 .. disabled, output voltage will begin to fall until current no longer flows
through Zener diode
2 network (106) and optical isolator (107), allowing charge pump oscillator
(101) to become active
3 again.
4 [0007] The resulting pulse frequency modulated waveform (108)
generated by
charge pump oscillator (101) and feedback network (104-107) is enabled
whenever the
6 regulated output voltage is below the regulated threshold and disabled
whenever the regulated
7 output voltage is above the regulated threshold. The result is a fixed DC
voltage output from an
8 arbitrary high voltage AC input.
9
BRIEF DESCRIPTION OF THE FIGURES
11 [0008] The present invention is illustrated by way of example, and
not by way of
12 limitation, in the figures of the accompanying drawings and in which
like reference numerals
13 refer to similar elements and in which:
14 [0009] Figure 1 is a prior art pulse frequency modulated power
supply.
[0010] Figure 2 is a block diagram of a power supply in accordance with one
16 embodiment of the present invention.
17 [0011] Figure 3 is a block diagram of a software-controlled power
supply including a
18 standby safety mechanism, in accordance with one embodiment of the
invention.
19 [0012] Figure 4 is a block diagram of a software controlled power
supply including a
standby safety mechanism and an output switch, in accordance with one
embodiment of the
21 invention.
22 [0013] Figure 5 is a block diagram of one embodiment of the standby
safety
23 mechanism.
24 [0014] Figure 6 is a circuit diagram of one embodiment of the system.
[0015] Figure 7 is a state diagram of the micro-controller, in one
embodiment.
26 [0016] Figure 8 is an illustration of an exemplary power consumption
curve.
27 [0017] Figure 9 is a flowchart of one embodiment of using the micro-
controller for
28 providing additional features with the charger system.
29
DETAILED DESCRIPTION
31 [0018] The present invention is a power supply for charging battery
powered mobile
32 devices from a variety of alternating current (AC) inputs. The power
supply has the ability to
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1 disengage power to rechargeable devices that remain coupled but have
completed charging,
2 eliminating trickle power draw. The power supply in one embodiment
further can modally
3 regulate power output such that when no device is coupled to the power
supply the standby
4 power consumed by the power supply itself is reduced. This is
accomplished by using a
software-controlled regulator, with a micro-controller, or microprocessor.
6 [0019] The following detailed description of embodiments of the
invention makes
7 reference to the accompanying drawings in which like references indicate
similar elements,
8 showing by way of illustration specific embodiments of practicing the
invention. Description of
9 these embodiments is in sufficient detail to enable those skilled in the
art to practice the
invention. One skilled in the art understands that other embodiments may be
utilized and that
11 logical, mechanical, electrical, functional and other changes may be
made without departing
12 from the scope of the present invention. The following detailed
description is, therefore, not to
13 be taken in a limiting sense, and the scope of the present invention is
defined only by the
14 appended claims.
[0020] Figure 2 is a block diagram of a simplified diagram of one
embodiment of
16 embodiment of a software-controlled regulator. The fixed Zener regulator
of Figure 1 is
17 replaced with a software-controlled regulator using a micro-controller
209, and elements
18 identified by reference numerals 202-205 parallel the features
identified by reference numerals
19 102-105 in Figure 1. The reference voltage is derived from the output
voltage by a divider
network 206, which is then fed into the micro-controller 209. The micro-
controller 209 monitors
21 this reference voltage using either analog to digital conversion or an
analog comparator. Many
22 modern embedded micro-controllers include one or both of these
capabilities. In one
23 embodiment, the micro-controller used is the ATTiny13A by ATM EL
CORPORATION TM.
24 [0021] In one embodiment, the reference voltage from voltage divider
network (206)
is input to micro-controller (209), which compares it against a target value,
and produces a
26 Boolean enable state. In one embodiment, the enable state is true when
the voltage is below
27 the target value, and false when the voltage is above the target value.
28 [0022] Micro-controller (209) outputs the Boolean enable state,
generated by
29 examining the reference voltage from divider network (206), to optical
isolator (207). In one
embodiment, optical isolator (207) is "on" when the enable state is true, and
"off" when the state
31 is false. This produces the enabled and disabled periods shown in
waveform (208).
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1 [0023] The micro-controller 209 uses the voltage reference to
generate a digital
2 enable signal, which is fed back to charge pump oscillator (201). The
charge pump oscillator
3 (201) is enabled whenever software in the micro-controller 209 determines
that the voltage is
4 too low and disabled when software determines that it is too high.
Because the feedback is
software controlled, it can be set to any arbitrary voltage. In one
embodiment, this enables the
6 system to act as a charger to various devices, including devices that
require a variety of voltage
7 and/or current profiles.
8 [0024] Because standby power consumption is a product of both voltage
and current
9 (P = V* l), the system can leverage software controlled voltage to reduce
standby consumption.
When the "nominal" voltage, the voltage required by a coupled rechargeable
device, is no
11 longer required, the software can downshift the voltage to a
significantly lower "keep-alive" level.
12 This level is sufficient to keep the micro-controller alive while
considerably reducing standby
13 power consumption. Software voltage control can also remove the ripples
in the DC output and
14 provide a completely stable output voltage for charging.
[0025] Those skilled in the art will realize that the tight regulation and
filtration
16 mechanisms, required to make a fixed Zener feedback mechanism operate
successfully, are not
17 required for the micro-controller implementation. Because the feedback
signal is digital, it is
18 either on or off and can be timed and aligned to satisfy the charge pump
oscillator of the DC/DC
19 converter mechanism.
[0026] Those skilled in the art will also realize that, in one embodiment,
the output
21 voltage can be directly fed to the micro-controller without the need for
a voltage divider network.
22 Additionally, other reference implementations, including those that
involve Zener diodes or fixed
23 voltage references, can be substituted for or enhance the voltage
divider.
24 [0027] In one embodiment, micro-controller 209 controls an indication
mechanism
(not shown), which shows the status of the system. In one embodiment, the
indication
26 mechanism is visual, such as an LED (light emitting diode). In one
embodiment, the LED may
27 be a multi-colored LED, or a plurality of separate LEDs that together
output a spectrum of
28 colors, with different colors indicating different statuses. In one
embodiment, indication
29 mechanism is auditory, such as a speaker or piezoelectric element. In
one embodiment, the
indicator is data transmitted to an external device or application. In one
embodiment the
31 indication mechanism shows the status of the coupled device, such as
charging or charged. In
32 one embodiment the indication mechanism shows the status of the system,
such as over
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1 temperature or over current. In one embodiment, the indication mechanism
provides a plurality
2 of metrics and statuses in graphical form within an external application.
3 [0028] The software-controlled power supply has several advantages.
Regulation
4 circuitry is simpler but can be made more precise by software. The
feedback to the DC/DC
voltage converter is digital, eliminating the ripple created by partial on and
partial off states.
6 Using software-controlled power supply also enables the reduction of
standby power by
7 lowering the regulated voltage from nominal levels to keep-alive levels
when a device is not
8 being charged. Additionally, the same power supply can be programmed to
different nominal
9 power output levels, or even multiple power output levels, depending on
application.
[0029] In one embodiment, the coupled device being charged may also connect
to
11 the charger system via a wireless connection, such as Bluetooth Tm, or
via a wired connection,
12 such as USB. The system can in one embodiment, read data from the device
being charged,
13 such as device specification, model and status, and adjust the power
supply output levels, in
14 response. In one embodiment, the system adjusts maximum current output
based on data
communicated over the connection. In one embodiment, the system adjusts
regulated voltage
16 output based on data communicated over the connection. In one
embodiment, the system
17 adjusts maximum charge time based on data communicated over the
connection.
18 [0030] Figure 3 illustrates one embodiment of a software-controlled
power supply
19 that provides a practical implementation to address software-failure
issues. Because the power
supply is controlled by a micro-controller, the system addresses what occurs
if the micro-
21 controller fails, crashes, or needs to be taken offline for
reprogramming or other reasons. A
22 crashed, frozen, or halted micro-controller will no longer provide
regulation feedback and, thus,
23 without a control mechanism can lead to an over-voltage or under-voltage
situation, potentially
24 damaging itself or any coupled device. This embodiment of the power
supply provides an
analog backstop regulation, in case the software crashes, while the elements
identified by
26 reference numerals 301-305 and 308 parallel the features identified by
reference numerals 101-
27 105 and 108 in Figure 1.
28 [0031] Figure 3 illustrates one embodiment of the software controlled
power supply
29 with an analog backstop acting as a standby safety mechanism.
[0032] The digital enable state generated by micro-controller (309) by
observing the
31 reference voltage produced by divider network (306) is no longer
directly coupled to optical
32 isolator (307), as in Figure 2, but connected through standby safety
mechanism (310) instead.
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1 [0033] The standby safety mechanism (310) protects the regulated
output by
2 overriding the digital enable state from micro-controller (309) if the
regulated output voltage
3 exceeds a fixed upper safety limit.
4 [0034] The standby safety mechanism (310) ensures that the regulated
output does
not fall to zero by overriding the digital disable state from the micro-
controller (309) if the output
6 voltage falls below a fixed lower keep-alive limit.
7 [0035] The standby safety mechanism 310 provides two overrides, in
one
8 embodiment. The digital feedback from the micro-controller is allowed to
pass through to the
9 feedback circuitry if, and only if, the regulated output is below a safe
upper limit, and the
regulated output is above a minimum keep-alive limit. The standby safety
mechanism allows for
11 arbitrary software controlled nominal voltage regulation between and
upper safety limit and
12 lower keep-alive limit by passing the digital feedback from the micro-
controller through the
13 optical feedback circuitry.
14 [0036] Those skilled in the art will realize that, in addition to
protection against
software failure, the standby safety mechanism can be designed to allow the
micro-controller to
16 "lock" the regulation to either the upper safety limit or the lower keep-
alive limit. This also
17 enables the micro-controller to go to sleep, thereby disabling software
regulation, with the logic
18 state set to keep-alive during sleep. This is advantageous for
additional standby power savings.
19 Disabling software regulation and defaulting the logic state (or
tristate) to the upper safety limit
can also be used when the micro-controller is offline for in-circuit software
programming.
21 [0037] Figure 4 illustrates one embodiment of a software controlled
power supply
22 with a standby safety mechanism and load attachment detector. The
regulated output power
23 controlled by micro-controller (409) and standby safety mechanism (410)
is fed through
24 MOSFET switch (411) and through shunt (412), and the elements identified
by reference
numerals 401-408 parallel the features identified by reference numerals 101-
108 in Figure 1.
26 The gate of MOSFET switch (411) is enabled and disabled by micro-
controller (409) through
27 signal (413) in order to switch on and off the output of regulated power
to a coupled device.
28 Voltage on the output side of shunt (412) is fed back to micro-
controller (409) via feedback
29 signal (414) in order to provide current output measurement.
[0038] When MOSFET switch (411) is disabled using signal (413), voltage on
the
31 output side of shunt (412) can be pulled up with a high-impedance input
by the micro-controller
32 (409) on feedback signal (414) and used to detect the presence of
coupled devices at the output
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1 port. In one embodiment, voltage feedback on the output is pulled up by a
resistor internal to the
2 micro-controller. In one embodiment, voltage feedback on the output is
pulled up by an external
3 resistor.
4 [0039] Rather than tie the regulated output to the connection between
the power
supply and the charging device, an output switch controlled by digital logic
in the micro-
6 controller connects and disconnects power to the coupled device. In one
embodiment, the
7 output switch is a MOSFET transistor.
8 [0040] A current sensing mechanism provides feedback to the micro-
controller to
9 determine the amount of power flowing to the coupled device. Software in
the micro-controller
monitors power flowing to the coupled device and, once it has determined that
the device is fully
11 charged, disconnects it by disabling the switch. In one embodiment, the
current sensing
12 mechanism is a resistive shunt.
13 [0041] Additionally, the voltage feedback from the output stage of
the current
14 sensing mechanism to the micro-controller can be used as a device
detection mechanism when
the output switch is disabled. By adding a pull-up resistor (or using an
internal micro-controller
16 pull-up) and monitoring the voltage drop on the output stage, a simple
device detection
17 mechanism can be realized.
18 [0042] Those skilled in the art will realize that using a shunt to
provide current (and
19 thus power) feedback is an implementation choice. In one embodiment, the
current feedback is
derived from the voltage drop across the output switch. Power delivered to the
coupled device
21 can also be derived from the digital output signal supplied by the micro-
controller. The ratio of
22 enabled to disabled states over a fixed period of time is proportional
to the amount of power
23 being delivered.
24 [0043] Of course, because of the presence of a micro-controller,
those skilled in the
art will see that a variety of alternate or additional device detection
mechanisms are made
26 available, including but not limited to optical sensors, mechanical
switches and capacitive
27 discharge circuits.
28 [0044] The software controlled power supply with a standby safety
mechanism and
29 load attachment detector has numerous advantages. Device attachment and
detachment can
be detected. The power flow to the coupled device can be monitored, and
disabled, once it is
31 determined that the device is fully charged or no longer requires
charging. This eliminates
32 trickle loss. Once power is disabled to the coupled device, nominal
output can be reduced to a
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1 keep-alive level, and the micro-controller can be mostly disabled,
minimizing standby power
2 consumption.
3 [0045] Figure 5 is one embodiment of the standby safety mechanism
that overrides
4 the digital enable signal from the micro-controller. In one embodiment,
this standby safety
mechanism is used in the circuits described above, in Figure 3 and Figure 4.
Zener network
6 (501) becomes active when the output voltage exceeds the Zener threshold,
forcing the LED in
7 the optical isolator to become active. The Zener threshold is set for the
upper safety limit, in one
8 embodiment.
9 [0046] Diode network (502) remains inactive as long as the digital
enable signal
(503) from the micro-controller is at logic high or in a high-impedance state,
leaving Zener
11 network (501) as the only method of regulation.
12 [0047] Diode network (502) becomes active when the digital enable
signal (503)
13 from the micro-controller is at logic low, and the output voltage
exceeds the keep-alive
14 threshold, determined by the voltage drop across diode network (502) and
the optical isolator.
[0048] A digital waveform supplied on digital enable signal (503) from the
micro-
16 controller will pass through to the LED on the optical isolator and can
be used to regulate output
17 voltage at any level between the minimum enforced by diode network (502)
and the maximum
18 enforced by Zener network (501).
19 [0049] One embodiment of the standby safety mechanism emphasizes
simplicity
over accuracy and is ideal for applications where precise regulation is only
required for the
21 nominal output level. However, those skilled in the art will note that a
variety of alternative
22 embodiments of the standby safety mechanism can be realized by
substituting or adding to the
23 recommended components. For instance, the diode drop mechanism in
network (502) can be
24 replaced by a Zener network. Also, fixed voltage references, such as the
Texas Instruments
LM431, can be used in place of diodes, if more precision is required for the
minimum keep-alive
26 level or maximum safe limit.
27 [0050] The standby safety mechanism defaults to the keep-alive limit
whenever the
28 digital logic input is pulled low. It defaults to the upper safety limit
whenever the digital logic
29 input is set high. Additionally, it remains in the upper safety limit
when the digital logic input is
set to a high-impedance state, such as during micro-controller programming.
31 [0051] The standby safety network provides the ability to set a
preferred DC output
32 level at any level between a keep-alive minimum and a safe upper
maximum, through a digitally
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1 supplied waveform. It also allows a micro-controller to assert a digital
logic level and go to sleep,
2 locking regulation at one of the two enforced limits. The most practical
use of the latter feature is
3 to lock regulation at the lower keep-alive limit and go to sleep for
maximum power savings.
4 Finally, the standby safety network allows power to be supplied to the
micro-controller by the
power supply while the micro-controller is in a passive or halted state, such
as during debug or
6 reprogramming.
7 [0052] If a digital square wave signal is provided by the micro-
controller, this signal
8 will pass through the standby safety mechanism to the feedback circuitry.
This allows for an
9 arbitrary software controlled nominal level anywhere between the upper
safety limit and the
lower keep-alive limit.
11 [0053] The logic table enforced by the standby safety mechanism is as
follows:
12
Digital Logic Safety Mode Output
Passive (high impedance) Blocked Upper safety limit
Enable (low) Blocked Upper safety limit
Disable (high) Blocked Lower keep-alive limit
Waveform Pass through Software controlled
13
14 [0054] In one embodiment of the standby safety mechanism provides
numerous
advantages. It enables software to control the nominal regulation level
through a waveform.
16 Furthermore, software can force the mechanism into a keep-alive mode and
most of the micro-
17 controller can go to sleep, saving power. Furthermore, the system
ensures that software
18 crashes or bugs cannot cause over voltage failure conditions or under
voltage brown-outs.
19 Additionally, the system enables the micro-controller to remain powered
by the power supply
while halted or during programming.
21 [0055] Figure 6 is a circuit diagram of one embodiment of the system,
with which the
22 present invention may be used. Figure 6 includes additional blocks
outside the scope of this
23 invention to provide an example of a practical implementation.
24 [0056] The system is coupled to alternating current (AC) power, such
as the power
provided by a wall outlet. The AC power is rectified by rectifier block (600)
using diode bridge
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1 (603) and bulk capacitor (604). In one embodiment, fuse (602) is included
for safety. Capacitor
2 (601) is included to minimize emissions from the charge pump oscillator.
The output from
3 rectifier block (600) is high voltage DC.
4 [0057] Charge pump oscillator (640) is implemented, in one
embodiment, using an
integrated oscillator controller and MOSFET (641) available from a variety of
vendors. In one
6 embodiment, the TinySwitch from POWER INTEGRATIONSTm is used. The
oscillator (640) is
7 .. powered by bypass capacitor (642). Optical isolator (645) provides
electrically isolated enable
8 signal (646) to integrated oscillator controller (641), which, in turn,
powers transformer (630)
9 through its integrated MOSFET.
[0058] Snubber network (610) is included for illustrative purposes only but
would be
11 used in a practical implementation to protect the MOSFET in integrated
oscillator controller
12 (641) from over-voltage spikes generated by excess energy in transformer
(630) during
13 switching cycles. Those skilled in the art will recognize that there are
many suitable variations of
14 a snubber network and that the values of the components within the
snubber network should be
tuned to match the characteristics of the transformer and other components.
16 [0059] Safety capacitor (620) is included for illustrative purposes
only. It is used to
17 provide a safe ground reference for the isolated portion of the circuit.
18 [0060] Rectifier block (650), consisting of Schottky diode (651) and
bulk capacitor
19 (652), converts the high frequency, isolated AC output of transformer
(630) into isolated DC.
[0061] Standby safety block (660), consisting of Zener network (661) and
diode
21 network (662), implements the standby safety mechanism discussed above.
Signal diode (663)
22 provides a pathway for micro-controller (670) to send an enable signal
waveform via output pin
23 (675) through standby safety block (660) to optical isolator 645,
thereby setting the regulated
24 output voltage.
[0062] Output control block (680) provides regulated output voltage
feedback to
26 micro-controller (670) on comparator input pin (672) via voltage divider
network (683). Those
27 skilled in the art will recognize that the values in divider network
(683) must be tuned to provide
28 a feedback voltage proportional to the output voltage, such that the
feedback voltage on input
29 pin (672) are within the limits of the micro-controller (670).
[0063] Output control block (680) provides current feedback to micro-
controller (670)
31 via positive input pin (671), which provides voltage before resistive
shunt (681), and negative
32 input pin (674), which provides voltage after output gate switch (682).
The voltage drop between
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1 pins (671) and (674) is proportional to the current flowing through shunt
(681) to the coupled
2 charging device.
3 [0064] Output control block (680) includes output gate MOSFET switch
(682), which
4 allows micro-controller (670) to enable or disable current flow to the
coupled device via output
signal (673). When signal (673) is disabled and no current is allowed to flow
through gate (682),
6 input pin (674) can be combined with an internal pull-up within micro-
controller (670) to create
7 an attachment and detachment detection mechanism.
8 [0065] Micro-controller (670) utilizes system software (690) to
provide output voltage
9 regulation and state. The logics described, in one embodiment, are
software running on micro-
controller (670). Regulate logic (692) controls output on enable pin (675) by
monitoring
11 reference voltage at pin (672) in combination with feedback from monitor
logic (693). Monitor
12 .. logic (693) monitors current flow through shunt (681) via pins (671) and
(674) and calculates the
13 charge state of the coupled device as well as other factors, such as
maximum safe current and
14 temperature, and reports results back to regulate logic (692) and state
logic (691). State logic
(691) determines the state of the system and controls output through gate
(682) via signal (673).
16 [0066] The micro-controller, in one embodiment, uses a state machine-
based
17 switching mechanism. The state machine switches the power output among
the states of the
18 power supply. In one embodiment, at a minimum the power supply has two
states, a keep-alive
19 level with power output to the coupled device disabled (standby), and a
nominal level with
power output to the coupled device enabled (charging). In one embodiment, when
no device is
21 connected or the connected device is fully charged, the micro-controller
is at a keep-alive level.
22 [0067] In one embodiment, the micro-controller includes software that
provides a
23 regulator feedback loop for providing digital enable signal to the
standby protection mechanism.
24 The micro-controller, in one embodiment, further includes a monitor
feedback loop to measure
power flow to the coupled device.
26 [0068] In one embodiment, each of these components (state machine,
regulator
27 feedback loop, monitor feedback loop) is implemented as an independent
thread in the micro-
28 controller. Alternatively, each of feedback loops can be implemented as
hardware timer events,
29 and the state machine as an endless main loop. Those skilled in the art
will recognize that all
three software components also can be implemented as a single continuous
running loop.
31 [0069] The software controlled charger has numerous benefits. It
regulates the
32 power very precisely. It also provides current fold-back when the load
attempts to draw
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1 excessive current from the supply. Fold-back reduces both the output
voltage and current to
2 below the normal operating limits. In one embodiment, the current limit
that initiates fold-back is
3 a variable value maintained by the micro-controller.
4 [0070] In one embodiment, the system also provides temperature
triggered fold-
back, reducing the voltage and current when the system approaches the
temperature limit. In
6 one embodiment, the temperature level which initiates fold-back is a
variable value maintained
7 by the micro-controller. In one embodiment, temperature fold-back causes
the algorithm in the
8 micro-processor to incrementally back off the current over a time period.
Because the micro-
9 controller can precisely control current levels, and there is no need for
hardware to limit current
strictly. This enables the system to slowly reduce the current, until it
reaches an acceptable
11 temperature. It can then iteratively increase the current, until it
stabilizes at maximum
12 temperature limit. In one embodiment, above an upper threshold, the
system may lock. This
13 ensures that, unlike some existing chargers which have an overheating
problem, this charging
14 system will not overheat.
[0071] In one embodiment, the micro-controller may include a temperature
sensor.
16 In one embodiment, the ambient temperature may be used to change the set
point for the
17 current limit, since the current limit is controlled by software, and
thus fully adjustable. T his
18 means that the system can adjust based on environmental conditions, and
exhibit different
19 behaviors based on ambient conditions, for example hot or cold weather,
or high or low
humidity. This enables the system to adjust for current conditions, rather
than having to account
21 for the worst case scenario in the design.
22 [0072] One embodiment of the state machine used by the micro-
controller is shown
23 in Figure 7. In the standby state 710, the system instructs the
regulator feedback loop to lock to
24 the keep-alive limit, and ensures that power flow through the power
output port is disabled. In
the standby state 710, the device detection circuitry is active. When a device
attachment is
26 detected, the system moves to the charge state 720. Otherwise, the
system stays in the
27 standby state 710. In one embodiment, when the system moves to the
charge state, the
28 minimum, maximum and count values tracked by the monitor are reset.
29 [0073] In the charge state 720, the process instructs the regulator
feedback loop to
regulate at nominal output, and enables power flow through power output port.
In one
31 embodiment, device detection circuitry is disabled. In the charge state
720, the monitor
32 feedback loop is enabled to monitor power flow to the coupled device and
report back the
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1 charge state. When the monitor feedback loop reports that the charge is
complete, the system
2 moves to the complete state 730. Additionally, in one embodiment, if
current stops flowing
3 through the charge port (indicating probable device disconnection), the
system moves to the
4 complete state 730. In one embodiment, when an optional running timer,
which times a
maximum allowed charge time, expires, the system moves to the complete state
730.
6 [0074] In one embodiment, if monitor feedback loop reports an over-
current
7 condition, charge state 720 temporarily switches to current limit state
725 until current falls
8 below the limit and it can switch back to charge state 720.
9 [0075] In the complete state 730, the process disables power flow
through the power
output port. The process then transitions back to the standby state 710.
11 [0076] Those skilled in the art will note that the above embodiment
is a minimal,
12 exemplary implementation and that a number of practical enhancements can
be added. Such
13 enhancements include, but are not limited to, features such as providing
user feedback through
14 illumination or audible sounds, measurement output through serial or
other interfaces, and
additional states and timers, such as wake-up and re-charge. Further
enhancements include,
16 but are not limited to, wireless or wired communication of measurements
and states.
17 [0077] Those skilled in the art will also recognize that several
enhancements to the
18 above implementation may be required for regulatory approval and safety.
Such enhancements
19 include but are not limited to features such as temperature monitoring
and current limiting.
Finally, practical additions such as device attachment and detachment
detection via voltage
21 drop, mechanical or optical switching, capacitive discharge or other
methods may be utilized.
22 [0078] In one embodiment, a regulator feedback loop controls the
enable signal to
23 the standby protection mechanism. This control loop for the regulator
feedback sets the digital
24 enable state input to the standby safety mechanism. In one embodiment,
the control loop may
be cyclical or execute this process at a fixed interval. In one embodiment,
the control loop may
26 be run within charging state 720.
27 [0079] The control loop for the regulator feedback asserts the
digital input to the
28 standby protection mechanism in order to control the regulated voltage
level in response to
29 certain events. In one embodiment, these events are:
o If the keep-alive flag is set, assert the standby input to logic low,
locking voltage
31 to keep-alive level;
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1 o else, if over-current flag is set, assert the standby input to
logic low, lowering the
2 voltage;
3 o else, if the reference voltage supplied to the micro-controller is
above the software
4 limit, assert the standby input to logic low, lowering the
voltage;
o else, assert the standby input to logic high, raising the voltage.
6 [0080] In one embodiment, the regulator feedback loop cycles at a
frequency
7 sufficient to achieve stable nominal regulation. This frequency is likely
to be in the 1kHz-20kHz
8 range, depending on application.
9 [0081] The monitor feedback loop, as discussed above, monitors the
power flow to
the coupled device and, via computations on the power flow, determines when
the device is
11 charged and no longer requires power. Typical rechargeable devices begin
the charge process
12 by consuming maximum power, usually at a steady state level. This is
then followed by a
13 gradual drop-off in power consumption as charging approaches completion.
In the final phase,
14 the slope of the drop-off in power becomes more gradual, asymptotically
approaching steady
state again. Figure 8 is a graph illustrating the power consumption curve.
16 [0082] The monitor feedback loop may be executed cyclically or at a
fixed
17 frequency. In one embodiment, the monitor feedback loop is active when a
device is connected
18 to the charger.
19 [0083] The monitor feedback loop checks the current flowing through
the shunt by
measuring the voltage drop across it, in one embodiment. In one embodiment,
the monitor
21 feedback loop uses a ratio of enable to disable cycles generated by the
regulator feedback loop
22 over a set time interval to determine the current flow. If the current
exceeds a soft current limit,
23 the system sets the current limit flag (see regulator feedback loop) and
allows nominal voltage
24 to fall below the regulated level, limiting current flow to the coupled
device.
[0084] The monitor feedback loop computes and records power flowing to the
26 coupled device from the measured current. The below exemplary process is
designed to
27 deduce the power curve, shown in Figure 8, based on the power flow
measurements. Note that
28 the specific details are merely exemplary, and could be altered.
29 [0085] If power flowing to the coupled device exceeds the recorded
maximum, in
one embodiment, the system sets a new maximum, sets the minimum to the
maximum, and
31 resets the time-between-minimums counter. Note that the "recorded
maximum" is below the
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1 nominal maximum power, and rather a reflection of how much power the
coupled device is
2 accepting rather than how much power the charger can produce.
3 [0086] If power flowing to the coupled device is below the recorded
minimum, in one
4 embodiment, the system sets a new minimum, and resets the time-between-
minimums counter.
[0087] If power flowing the coupled device is above the recorded minimum
and at a
6 point below the recorded maximum, the process increases the time-between-
minimums
7 counter. In one embodiment, the point below the recorded maximum is
derived as half of the
8 recorded maximum.
9 [0088] If the time-between-minimums counter exceeds a set limit, the
system sets
the charge-complete flag.
11 [0089] In one embodiment, the system may perform additional optional
12 measurements and set additional flags. For example, the monitor feedback
loop may also
13 monitor whether the device is over-temperature, or whether the charging
conditions otherwise
14 exceed specification.
[0090] The above embodiment is designed to observe the drop from the
initial
16 steady state maximum, here arbitrarily set to one-half of the maximum
observed power, and
17 begin an analysis of the drop-off slope. As the slope gradually
approaches steady state, the
18 time between observed new minimums will increase and is tracked by a
running counter. Once
19 this counter has exceeded a set limit in state, the drop-off has become
essentially flat or steady
state. When that occurs, the device is fully charged, and the system can
switch to the complete
21 state.
22 [0091] Those skilled in the art will realize that the advantage of
the proposed
23 embodiment is that it functions for devices with both small and large
power draws because it
24 does not require any pre-programmed fixed values or thresholds. It also
works with devices that
continue to draw significant levels of standby power after charge completion
as well as those
26 that do not. It relies on shape analysis of the power curve and not on
any fixed values.
27 [0092] Finally, those skilled in the art will note that the
transition point for starting the
28 time-between-minimums analysis is arbitrarily set to the half of the
maximum observed power
29 but that any realistic point between the maximum and anticipated
minimums will suffice. Those
skilled in the art will also realize that additional checks can be added to
the monitor feedback
31 loop. For instance, an over temperature check could be combined with the
over current check to
32 throttle back the current limit until the temperature stabilizes to an
acceptable level.
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1 [0093] As mentioned earlier, in one embodiment, the current measured
via shunt
2 and observed in the standby state of the current feedback loop can be
replaced by an internal
3 ratio of enable and disable states set by the regulator feedback loop
over a fixed interval. This
4 ratio is a proxy for power output. Current is a proxy for power when
output voltage is fixed to a
known value.
6 [0094] Figure 9 is a flowchart of one embodiment of using the micro-
controller for
7 providing additional features to the charging system. In one embodiment,
these features may
8 take advantage of the processor in the device coupled to the charging
system, which may be a
9 mobile phone or other mobile computing system.
[0095] At block 910, the micro-controller detects the device coupled to the
charging
11 system. Optionally, at block 910, the charging system can request data
from the coupled device.
12 In one embodiment, data requested from the coupled device is
supplemented by data stored in
13 the charger system. In one embodiment, the data is stored in a table in
a memory, and provides
14 information about various devices (e.g. model number data supplied by
the device is matched to
battery capacity in a table). In one embodiment, this may be done via the USB
plug. In one
16 embodiment, though, the USB data lines are shorted together in order to
conform to Battery
17 Charging Device (BCD) specifications, and thus no data can be obtained
from the USB
18 connection. In one embodiment, data may be requested via a Bluetooth or
other wireless
19 connection.
[0096] In one embodiment, prior to receiving this information, the charger
system
21 may provide a lower power output level to the coupled device. This
ensures that if the coupled
22 device is a low power device, it is not damaged. The system then may
increase the power
23 level, once the device data is received from the coupled device, and the
actual power settings
24 are available. In one embodiment, if no data is received, the charger
system assumes safe
power settings for all allowed coupled devices.
26 [0097] At block 915, device data is received from the coupled device.
In one
27 embodiment, the device data is received via a Bluetooth or other
wireless connection. In one
28 embodiment, the data may be the brand identity, model number, device ID,
or some other data
29 that identifies the coupled device. In one embodiment, the coupled
device data may be
obtained from an application residing on the coupled device. The application
is associated with
31 the charger system, and interacts with the charger system without
requiring user action, in one
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1 embodiment. In one embodiment, if there is an application, the charger
system may not request
2 the data directly, but rather wait for the application to send the data
to it.
3 [0098] At block 920, when the data from the coupled device is
received, the process
4 determines the power and charging configuration for the coupled device.
In one embodiment,
this is done using a look-up table. In another embodiment, the power and
charging
6 configuration is provided directly by an application residing on the
coupled device. The charging
7 configuration may define the voltage and current levels used in charging
the coupled device. In
8 one embodiment, the charging configuration may define the instantaneous
power level (e.g.
9 10VV). In yet another embodiment, the data provided by an application
instructs the charging
system to relinquish power output and state control to the application itself.
11 [0099] At block 925, the coupled device is charged, based on the
available data. In
12 one embodiment, charge status is derived through analysis of the power
curve. In one
13 embodiment, the coupled device supplies charge status to the charger
system as data.
14 [00100] At block 930, the process determines whether the system is
overheating. If
so, at block 935, the process backs off slowly from the current and voltage
level, to ensure that
16 the device does not overheat.
17 [00101] At block 940, the process determines whether the system has a
setting other
18 than full charge. In one embodiment, such settings may be made via an
application. For
19 example, in one embodiment, the user may set the device or charger to
provide a quick boost,
for example to 50% power, after 10 minutes or 75% of power, whichever happens
first.
21 [00102] If there is a setting other than a full charge, the process
considers charging
22 complete, when the set level is reached.
23 [00103] At block 950, the process determines whether charging is
complete. In one
24 embodiment, the process detects that the coupled device is fully
charged. In one embodiment,
the process detects that the coupled device has reached the setting other than
full charge
26 indicated by the user. If not, the process returns to block 925, to
continue charging the coupled
27 device. If charging is complete, the process proceeds to block 960.
28 [00104] In one embodiment, at block 960 when there is an available
application, the
29 system may send a notification to the user, indicating that the coupled
device is fully charged, or
charged to the level indicated by the user (e.g. quick charge). In one
embodiment, the
31 application resides on the coupled device. In another embodiment, the
application resides on a
32 different device, such as a smart watch, computer, or other device that
can connect to the
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1 coupled device. In one embodiment, the charger system provides additional
data to the
2 application, at block 965. In one embodiment, for example, the
application may have a
3 dashboard to show how much power was saved by using the charger system.
In one
4 embodiment, the application shows an estimate of time until complete
charge. In one
embodiment, the application provides an estimate, based on an initial
evaluation by the charger
6 system, and periodically communicates with the charger system, to update
the estimate with
7 real data.
8 [00105] At block 970, in one embodiment, the process utilizes the
Bluetooth
9 connection between the charger system and the coupled device to determine
whether a
forgotten charger alert is needed. A forgotten charger alert is used, if after
charging, the
11 charger is left behind, while the coupled device is moved away. If so,
at block 975, an alert is
12 sent. In one embodiment, if the charger system interfaces with other
devices of the user, in
13 addition to the coupled device, the alert may be provide in connection
with any of those devices,
14 and using any of those devices.
[00106] At block 980, the process determines whether the user has overridden
the
16 alert. In one embodiment, the user may override the forgotten charger
alert, on the mobile
17 device, by indicating that the location in question is one where the
charger is OK to be left
18 behind (e.g., at home). If the user overrides the alert, in one
embodiment, the system uses
19 location data, from GPS, cellular triangulation, or other location
information to tag the location,
at block 985. The process then ends, at block 990. In one embodiment, the left-
behind alerts
21 may also be made if the user leaves the mobile device behind, but takes
the charger system.
22 [00107] Of course, though this process, is shown as a flowchart, it
should be
23 understood by one of the skill in the art that the ordering of the
actions is not necessarily limited
24 by what is shown. In one embodiment this is implemented as an interrupt-
driven system, such
that the system continuously monitors proximity and charge level, when
appropriate.
26 Additionally, the ordering of the process flow may be different, and
many of these steps may
27 take place concurrently. One of skill in the art should understand that
the flowchart format is
28 simply used for convenience in this figure.
29 [00108] In the foregoing specification, the invention has been
described with
reference to specific exemplary embodiments thereof. It will, however, be
evident that various
31 modifications and changes may be made thereto without departing from the
broader spirit and
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1 scope of the invention as set forth in the appended claims. The
specification and drawings are,
2 accordingly, to be regarded in an illustrative rather than a restrictive
sense.
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