Note: Descriptions are shown in the official language in which they were submitted.
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POWER SUPPLY CONTROL DEVICE
TECHNICAL FIELD
This invention relates to the control of -the supply of electrical power to
plug-in electrical equipment, in particular to the control of the supply of
electrical power to groups of such electrical equipment where the power
supply recuirement of these groups is related to the operational status of a
main piece of electrical equipment.
BACKGROUND ART
A desktop computer installation typically has associated with it a number
of peripheral devices and other associated electrical devices, each of
which is separately electrically powered. The peripheral devices can
include such things as printers, scanners and modems or there may be
associated devices such as a desk lamp or a room heater.
These peripheral devices and associated electrical equipment are in general
not used when the computer is not in use. However, because they are
separately electrically powered the user must, when tuming off the computer,
also turn off each of the peripheral and associated devices. This is a time
consuming process and indeed given the placement of the power switches on
many such electrical devices, may be extremely inconvenient.
It is also the case that widely used computer operating systems require
significant time to perform certain "housekeeping" tasks in between receiving
commancf to shut down and actualiy shutting off the power or being in a
position
to have the power supply to the computer shut off without causing problems for
the compLater system. During this time, the computer system also may not
tolerate having power removed from peripheral devices.
Accordingly many users simply leave the additional devices powered on after
the computer has been shut down.
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This is not ideal for a number of reasons. The first of these is that the
devices
continue to consume power which is both costly and a waste of resources. This
is particularly a problem since many modern devices use small plug-in
transformers to provide the lower operating voltages which they require. These
plug-in transformers continue to consume power whilst they are connected to a
mains supply even if the power switch on the device which they are supplying
with power has been switched off. Newer power supplies use solid state
switching devices but still consume about 0.5W.
It is also the case that all electrical devices have a finite life span of
operation
and this life span can be made to extend over a longer period of time if the
device is switched off when not in use.
It is also advantageous that mains power be removed from devices when not
required in order to reduce the possibility of exposure to damaging surges in
the mains power supply.
Prior art devices have attempted to deal with this problem by providing relays
which cut off power to peripheral devices when no current is flowing to the
main
device, the main device being the desktop computer itself.
However, most modern desktop computers have the ability to control their
power usage to some extent by entering one or more lower power consumption
states, usually referred to as standby states. Users may allow the device to
spend extended periods in such a standby state, negating most of the
advantages of the prior art devices.
DISCLOSURE OF THE INVENTION
The term 'master device" as used herein refers to at least one electrical
device
in that it rnay be a single electrical device or a number of electrical
devices each
requiring power supply. The term "master device" is intended to cover a
combination of devices such as a computer, audio equipment, visual
equipmerrt, etc each of which is attached to the power supply device.
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The term "True RMS power" as used herein refers to an average measurement
of power over a predefined period of time, regardless of waveform.
Accordingly there is proposed in one form of the invention, a power supply
control device for permitting energisation of a plurality of electrical
devices from
a single mains powgr, supply electrical outlet characterized in that there are
provided a plurality of controlled electrical outlets; a single electrical
input
adapted to connect to a mains supply electrical output a power sensor adapted
to detect power use of a master electrical devioe and to produce a power use
signal, a computer processor adapted to process said power use signal to
determine at least two power states of the master electrical device and detect
power fluctuations in the power su I to the master electrical device tiirou 6h
the a;wtier use signal, switch means controlEed by the computer processor
adapted to connect an electrical supply from the suppty electrical outlet to
each
of the controlled electrical outiets, which of the controlled electrical
outputs is
controlled to be connected to the electrical supply being determined by the
determined power state.
The 'power sensor' measures True RMS power and may be embodied in the
form of an analogue electronic circuit which multiplies instantaneous voltage
and current signals to derive a True RMS Power signal or by using a micro-
controller to digitise the voltage and current signals and then multiplying,
adding
and averaging the sampled values to calculate the True RMS power value_
In preference the at least two functional states of the master device include
standby, and fully on.
In preference, the master device includes the third functional state off.
In preference the computer processor is adapted to receive digital information
from the master device indicating its actual or intended functional state.
In preference the computer processor is adapted to monitor the state of any
port of the master device in order to determine the state of the master
device.
In preference the port is a serial port.
AMENDED SHEET
IPEA/AU
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In preference the port is a parallel port.
In preference the port is a USB port.
One or more of a number of possible means may be used to detect the state of
the master device. These may include the direct receipt of digital information
from the master device indicating its actual or intended functional state.
It may also include connection to any one or more of the output ports of the
master device which may include serial or parallel communication ports, USB
ports, or atiy other port.
The modern desktop computer generally has a complex and relatively time
consuming "power up sequence" which is the series of activities which the
computer performs immediately upon being first switched on. This sequence
may include activities to discover what peripheral devices are connected to
the
computer and to establish communication with such peripherals. One of the
advantages of the standby mode is that it is not necessary for the computer to
go through this power up sequence when it emerges from standby into fully
powered r-tiode.
However, this has the problem that some types of peripheral device cannot be
switched off while the computer is in standby mode or the computer will lose
the
ability to communicate with such devices until a full power on sequence is
performed.
According?y the controlled electrical outlets are controlled such that at
least one
controlled.electrical outlet continues to provide an electrical power supply
while
the state sensor indicates that the master electrical device is in a standby
condition.
In preference at least one controlled electrical outlet continues to provide
an
electrical power supply while the master electrical device is in an off
condition.
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In preference at least one controlled electrical outlet continues to provide
an
electrical power supply while the master electrical device is in a standby
condition.
In preference at least one controlled electrical outlet is controlled such
that it
5 does not provide an electrical supply when the master electrical device is
in a
standby state, but does provide an electrical supply when the master device is
in an on state.
In preference there are second switch means controlled by the computer
processor adapted to remove mains power from the power supply control
device, and power storage means sufficient to allow powering of circuitry to
return power to the power supply control device when required by a user or
external device.
For example, a modem or an external disk drive would be connected in such a
manner that power was not withdrawn from them when the computer is in a
standby mode but a printer or a desk lamp might be connected such that they.
receive power only when the computer is in a fully on mode.
Depending on the individual computer and its particular hardware
configuration,
the current or power drawn by the computer when in its standby mode may
vary.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described with reference to drawings wherein:
Figure 1 is a pictorial representation of an embodiment of the invention,
Figure 2 is a block diagram showing the main functional blocks of an
embodiment of the invention,
Figure 3 is a circuit diagram of an embodiment of the invention, and
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Figure 4 shows a circuit diagram of a further embodiment of the invention.
Figure 5 shows a block diagram of a further embodiment wherein the
device of the invention is contained within the case of a personal
computer.
Figure 6 is a plot of the power usage of a computer to which a device of
the invention may be applied.
Figure 7 shows a detail of an embodiment of the invention with zero mains
power draw in Off mode.
Figure 8 shows a flowchart of an embodiment of the present invention in
relation to ise with audio-visual equipment.
Figure 9 shows a flowchart of an embodiment of the present invention in
relation to E.ase with computer equipment.
BEST MODE FOR CARRYING OUT THE INVENTION
Turning now to Figure 1 there is shown a perspective drawing of a power
supply control device according to an embodiment of the invention. There is a
box 100 containing the working circuitry of the device. There is a power cord
101 which :s connected to a general-purpose electrical outlet. There is a
power
outlet 102 vvhich is in permanent electrical connection with the mains power
supply to the device. The main device to be powered, in this case a personal
computer 111 is connected to this outlet. The main device could be any other
electrical device whose state determines the power requirements for other
associated devices.
There is a power outlet 104 which is available to have connected to it such
electrical loads as require power only when the main computer is in a full
power
mode. A power board or power strip 107 is connected to this outlet in order to
allow multiple devices to be powered in this manner. Exemplary devices of this
class, being a printer 112 and a desk lamp 113 are shown.
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There is a further electrical outlet 103 which is available for the connection
of
loads which require power when the computer is in a fully on or a standby mode
but which do not require power when the main computer is switched off. A
further power board or power strip 108 is connected to this outlet in order to
allow multiple devices to be powered in this manner. An exemplary device of
this type is a modem 109.
Further there is a connection port 105 for the connection of a serial
communications cable to the device. A switch 106, called the "wake up/modify"
switch, is provided for activating the device in the event that it has powered
itself down.
Considering Figure 2, the main functional blocks of the device can be seen in
block diagi'am form. There is a mains power inlet 201 which supplies power to
a low voltage power supply 202. This supply provides power for the device's
electronic.components. Mains power is also supplied to the PC power module
203 which provides a non switched output 204 for powering the main electrical
device which would usually be a desktop computer. A surge suppressor 202
protects the circuitry from mains power surges.
Mains power is also provided to controlled outputs 205 and 206 via switch
means 207 and 208. The power supply to the non switched outlet 204 is
monitored via state sensor 209. The state sensor provides signals proportional
to the current and voltage drawn by the desktop computer to input 210 and 211
of microcontroller 212.
Thus the microcontroller is able to recognise the power usage levels of the
computer and hence determine the operational state:
An Off state where the power draw is zero or very low, indicating the computer
is off or in a non-operational power saving state. This state may mean that
the
device is completely switched off, functionally switched off, but still
drawing a
small amount of power through its power supply, or in a"hibernaten mode.
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A standby state in which the computer is drawing significantly more power than
in its Off state, but significantly less than in its fully operational mode.
This may
be because the computer has entered a standby mode, in which some
functionality (eg hard disk) is disabled so it draws less power, but is able
to
quickly respond to user input. It may also be in a situation wherethe user has
made no use of the computer for an extended time, but the computer either
does not have or does not enter a standby mode, due to the standby delay time
settings or simply because standby has not been enabled.
In a further embodiment, a standby state caused by user inaction may be
separately identified from a standby state caused by the computer entering a
standby mode. This will be referred to as User Inaction Standby State.
Other operational states with distinct power usage levels could also be
identified.
An On state in which the computer is performing operations.
The microcontroller identifies these three or more states by continuous
monitoring of the power usage of the computer. Referring now to figure 6,
there
is shown a plot 601 of the power usage as measured by the device, plotted
against time.
During time period 610, the computer is in use. The microcontroller monitors
the power usage in order to dynamically determine a baseline power usage,
plotted in figure 6 as plot 602, with frequent excursions to greater values.
This
baseline value, with excursions, is recognised by the power controller as
corresponding to the On state.
The value of dynamically determining the baseline power draw is that the same
power saver device may be used with differing pieces of equipment without the
need to know beforehand the exact power draw which corresponds to the On
state. This also means that altering components of the system, as for example
fitting a more power efficient hard drive, would not cause the power saver
device to 3ncorrectly assume the computer had entered a standby mode.
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During time period 611, the computer remains on, but is not in use. It does
not
enter a standby mode, perhaps because a user has not enabled this feature. It
can be seen that the baseline power usage does not vary, but excursions from
that baseline become rare. When the excursions are sufficiently few for a
sufFicieritly long period, the microcontroller recognises this pattern as
corresponding to the Standby state. In the further embodiment it will be
recognised separately as User Inaction Standby state
During period 612, the computer does enter a standby mode_ The power
consumption falls significantly. This is immediately recognised by.the
microcontroller as indicating Standby state.
During period 613, the computer is either turned off or enters a hibernate
mode.
Power consumption again falls signiftcantly, to a very low or zero level. The
power saver device recognises this as Off state.
The microcontroller 212 processes the signals and produces output signal 213
to turn on first controlled switch 207 only when On state is in force. A
signal is
produced at output 214 by the microcontrolEer to turn on second controlled
switch 208 when the Standby state or the User Inaction Standby state is in
force.
Thus first controlled switch 207 is on only when the computer is fully on,
while
second controlled switch 208 is on when the computer is in either an On state
or a Standby state.
There is also provided a communications module 215 which allows direct data
communication between the desktop computer and the power controller device.
This may be used to update the microcontroller firmware to set or alter any
variables held within the microcontroller, or to allow the computer to
directly
take on the function of the voltage and current detectors 209 and 210 and
directly control switches 207 and 208.
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In a further embodiment, shown in block diagram form in figure 5, the
functional
element of the power saver device are contained within the case 501 of a
computer.
In this case, the mains power inlet 502 is connected to the power saver device
5 circuitry 503. The controlled power outlets 504, 505 are located on the
outside
of the case. The PC power supply 506 is supplied with power from the power
saver device, either directly or via microcontroller controlled switch 507.
The powe, saver device and the PC power supply may be physically located in
the same -emovable sub-housing within the computer case in order to keep all
10 high voltage components together.
In this case, the computer main circuitry or motherboard may be equipped with
data outputs 508 enabling direct communication with the power saver device
circuitry.
The wake -up/modify switch 509 is located on the outside of the computer case,
or remotely. The switch may be an infrared sensor, adapted to sense a signal
from an inrrared remote control device.
Figure 3 snows a circuit diagram of an embodiment of the invention. There is a
mains power supply plug 1 which provides power to the power supply device
and also is the source of the power supply which is switched by the device to
the peripheral and associated devices of the computer installation.
There is a low voltage power supply which is shown as block 7.* This is made
up of a fuse 2, a transformer 3, which has a mains voltage primary coil and
two
nine-volt secondary coils. DC rectification is provided by a bridge rectifier
4 and
a linear voltage regulator 6. This provides a stable five-volt DC power
supply,
V,,,, 90, and a +12V supply, 91, and a -12V supply, 92.
The surge suppression circuitry 30 is connected in parallel with the power
supply. It provides surge suppression using three metal oxide varistors 29
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wired in a delta configuration to limit the maximum voltage between any two
wires to the breakdown rating of the varistors.
The supply of power to the desktop computer which is supplied via the device
of the invention, but is not switched by the device, is provided by power
outlet 9.
The neutral connection to this plug includes current sensing resistor S. There
is
a current signal conditioning differential input amplifier 10. This transfers
the
reference for the current signal from neutral to earth. If this is not done
the
neutral connector would need to be connected to the common terminal of the
power supply. Through any serial port connection, this would be connected to
the neutral dr earth conductor of the computer's internal power supply, which
could cause unwanted tripping of residual current devices protecting the
circuit.
The value of resistor 8 is chosen to be very low in order to reduce the power
dissipated in the resistor. Accordingly there is a requirement for a current
signal amplifier 11 in order to provide a referenced signal of sufficient
magnitude. The gain of this amplifier may be varied under the control of
microcontroller 24 by controlling analogue switches 12 in order to place one
or
more of resistors 13 in or out of circuit.
The current signal is further conditioned by the signal conditioning circuitry
31.
A capacitor eliminates any DC offset in the amplifier output while a resistor
and
two diodes provide a current limit and voltage clamping so that the amplified
current sigrral is in a fixed range about a reference voltage VAref, being the
voltage at 60. The signal range is -.3V to VAref +0.3V. The current detection
signal is then applied to analogue to digital converter input 51 of the micro
controller 24.
The incoming active and neutral. are connected to the resistive divider 14 for
the
purposes of detection of the voltage applied to the desktop computer.
Differential amplifier 15 shifts the reference for the voltage signal from
rteutral to
earth in the same manner as is done by differential input amplifier 10 for the
current signal.
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The voltage signal is then applied to a conditioning circuit 16 which includes
a
current limiting resistor and clamping diodes which limit the signal to -.3v
to var
ref +0.3v. The signal is applied to input 52 of the micro controller 24 which
is
configured to be the second channel of an analogue to digital converter.
A zero crossing detector 17 provides a signal to the micro controller 24 when
the voltage is at zero. This allows the micro controller to ensure that
measurements of the voltage and current signals are synchronised. A voltage
reference is provided by an active precision voltage reference 23. This
reference voltage is applied to the microcontroller to fix the upper limit of
the
analogue to digital converter.
Serial communications circuitry 22 allows for the connection of an RS 232
serial
port. Solid-state relays 27 control the supply of power to switched power
outlets 25, .26. The signals to switch the solid-state relay 27 are provided
from
the micro controller 24 via transistor buffers 28. The switch 33 is provided
to
connect the interrupt input 53 of the micro controller 24 to ground when the
switch is activated. Software in the micro controller monitors the
current/power
consumed by the desktop computer and it controls the power outlets 25 and 26.
The microcontroller automatically detects and establishes power levels which
correspond to the fully operational mode, standby mode and fully off mode of
the desktop compute ras described above in the description of Figure 2.
Startup values for the power thresholds corresponding to each of the
identifiable operational states of the computer are stored into e-prom. These
values are used by the microcontroller at startup, but new values are
continuously calculated based on the detected power usage of the computer. '
When the microcontroller program determines that Standby state is in force
then output 26 is energised, when On state is recognised then both outputs 25
and 26 are energised.
The desktop computer power consumption is calculated by taking the voltage
signal and the current signal which are applied to input 51 and 52 of the
micro
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controller and multiplying the corresponding samples and applying the relevant
calculation to calculate power. This power measurement gives a much more
accurate indication of the power consumption of the desktop computer than a
simple current measurement as it also takes into account any phase shift
between the current and the voltage as well as waveshape.
Figure 4 shows a further embodiment of the invention. This circuit operates in
the same manner as that of Figure 3, with the variations described below.
In some circumstances a user may require that power be withdrawn from the
computer as well as the peripheral devices when the computer is turned off.
This may be because, with modern computer power supplies which are
software switched, the computer will continue to draw a small amount of power
even when it has been instructed to switch off. Aiternativeiy, some users are
simply mor-e comfortable with the knowledge that the computer is isolated from
the mains power supply.
In this embodiment, the unswitched power outiet 9 is replaced by a power
outlet 511 where'the power supply to this outlet is controlled by the
microprocessor 24
via solid state relay 512. This operates to remove power from outlet 511 as
well
as from outlets 25 and 26 when the microprocessor detects that the computer
has shut down.
When this occurs, the computer ON/OFF switch is ineffective, since there is no
power to the outlet 511 to which the computer is connected. In order to turn
on
the PC, the interrupt switch 33 is pressed which causes power to be supplied
to
power outE=et 511 for a brief period (ten seconds in this case). If the PC is
switched on during this time, current begins to be drawn through outlet 511
and
the power control device is able to operate, supplying power to outlets 511,
25
and 26 as appropriate.
The PC ON/OFF 'soft' power switch may be eliminated, replaced or
supplemented by interrupt switch 33. This is due to the fact that the PC bios
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may be setup for the PC to 'power up' as soon as mains power has been
applied to it without the need to press the power ON/OFF switch.
A user may not wish this total shut down of power to occur. Accordingly,
there'
is firmware provided to aliow for two modes of operation_ In one mode the
switch 512 operates as described above. In the second mode, switch 512 is
always on an the device behaves in the same manner as the circuit of figure 3.
The firmware for the microprocessor 24 allows the interrupt switch 33 to be
used to communicate which mode is to be employed. An interrupt extension
socket 517 is provided to allow the interrupt switch to be placed remotely
from
the main power control device.
Where the:main device is not a computer, but, for example, a piece of
audio-visual equipment, or a video cassette recorder or perhaps a microwave
oven, there may be equipment, such as a real time clock, a time display or an
infra-red remote control detector which require ongoing, very small amounts of
power.
This very small amount of power would normally be drawn from the mains. This
requires that power be continue to be supplied to the device power supply. The
minimum power draw of a power supply supplying just these loads is about
0_5W. This is perhaps 50 times the actual power required to maintain the
functions which cannot have power withdrawn from them.
In an embodiment of the invention as illustrated in Figure 4, this smail
standby
power requirement may be supplied from an energy storage device, such as
rechargeable batteries or a storage capacitor. This storage device also
provides
power for a trigger to tell the power saver device to restore power to the
main
device. This allows for the power saver device to operate in the mode
described
above where power is removed from the main device when Off mode is
detected, and wherein mains power is also withdrawn from the power saver
device itself. Withdrawal of the power from the device is accomplished by
mains
power control 700. This may be a simple manual switch, or it may be as here, a
control circuit under the control of microcontroller 24, as illustrated in
Figure 7.
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This could also be a relay under control of the main powered device, or of an
independent control circuit.
The detail of the additional circuitry for the mains power control 700, is
illustrated in Figure 7. Battery activation functional block 710 detects that
mains
5 power is available. When it is available, it makes battery voltage available
at
point 709, otherwise the battery is disconnected. This ensures that battery
power is not wasted by use at times when no mains power is available, and
hence there is no possibility of the main device being called into use.
The presence of mains power provides sufficient current via capacitor 702 to
10 turn on transistor 703, which in turn, turns on p-type MOSFET 704. Power
from
battery 705 is now available at point 709.
When control line 781 goes low, transistor 708 will conduct. This makes
battery
voltage available to Vcc 90, and the power save device circuitry is activated.
The function block 711 now provides temporary power for the power saver
15 device circuitry. Relay 718 is activated. Battery is supplied to relay 718
directly
via transistor 708. The RC network of resistor 713, resistor 717 and capacitor
714 drives transistor 712 which connects earth to the relay 718. The relay 718
is activated which connects incoming mains active to the active terminal 701
of
power supply transformer 3, shown on figure 4.
Vcc 90 is now provided from mains power as described above. Trickle charging
of the battsery 705 is provided via resistor 707 and diode 706.
The presence of Vcc keeps transistor 712 on, which keeps relay 718 on and
power continues to be supplied to the power saver device.
Control line 780 is connected to microcontroller 24, via protection diode 716.
When the microcontroller program determines that the mains power should be
withdrawn from the power saver device, control line 780 is taken low.
Transistor
712 turns off, and relay 718 thereby also turns off. Power is withdrawn from
the
power saver device; and the inactive power usage is reduced to zero.
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In order for the power saver device to be activated, control line 781, must go
low. This is achieved by external, usually user initiated, action.
The simplest method is the manual switch shown as 752. Momentary activation
of this switch will initiate the sequence described and power up the power
saver
circuit.
This switch can be an independent switch on the power saver device, or can be
incorporated in the onloff switch of a controlled device.
Alternatively, the momentary low signal on control line 781 may be provided
via
a remote control receiver 753. This remote control device is powered from
battery 705=whenever mains power is available. The remote control receiver
753 detects a user initiated use of an infra red or wireless remote control
and
provides a momentary low on control line 781.
This is particularly useful when the main controlled device is an audio visual
device such as a television. Such devices are usually turned on by a remote
control. The remote control detector need not decode the message from the
remote control sender. It is sufficient that the remote control sender unit is
in
use to indicate that the user is likely to require that power be available to
the
main device. This. solves one of the major problems of remote controlled
devices with standby power requirements, such as televisions. Users are
generally unwilling to manually turn the units on before use and off after
use. In
this case, the unit is off, with no standby power usage, but is turned on
immediately the remote control is used, without requiring any additional
action
from the user. The normal action of the power saver device, removing power
when the main device is unused, performs the turning off step, which users are
equally unwilling to perform.
When the main device is one which has its own power supply and internal
battery, such as a laptop computer, the circuit of functional block 754 may be
employed. The positive supply of the laptop computer is connected to terminal
755, the common supply to terminal 757. Connected to terminal 756 is a control
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wire controlled by the laptop computer, which is active when the laptop
computer ;s on. When this control wire is active, transistor 760 turns on,
taking
control wire 781 low and activating the power saver device.
As illustrated in the circuit of Figure 4, the current sensing resistor 8 may
be
replaced by a current transformer 510. This has the advantage that the current
sense signal is electrically isolated from the mains voltage. This eliminates
the
need for the current signal conditioning amplifier.
Differential amplifier 15 is also eliminated by providing a mains voltage
sensor
516 which is connected to the power supply transformer 3. This mains voltage
sensor provides a mains voltage signal to the conditioning circuit 16 which is
as
described for the embodiment of figu're 3.
An output of the microprocessor 24 is used to drive Light emitting diode 502
to
indicate the operational status of the device. A buzzer 504 is aiso provided
under the control of the microprocessor 24 to allow status messages to be
communicated to an operator.
A switch 503 is provided to signal to the microprocessor that it should enter
a
programming mode to allow reception of firmware upgrades.
The signal -rom the current transformer 510 is applied to current signal
amplifier
513. The gain of this amplifier is controlled by the microprocessor 24 by
using
control lines 514 to connect selected resistors 515 into the earth path of the
amplifier.
The power supply control device continuously monitors the reticulated mains
voltage and supplies the result to the microcontroller. The microcontroller is
programmed such that if the mains power deviates from a pre-determined
range for a oreset period of time, then switches 26 and 27 are operated in
such
a way that power is removed from all controlled outlets until such time as the
voltage again stabilises within the pre-determined range for a preset period
of
time. This provides protection from mains supply Over-Voltage and Under-
Voltage. The power supply control device samples the mains voltage and then
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calculates the True RMS Voltage. This means that the value will be measured
correctly regardless of supply wave distortion. This method will work
correctly
for non sinusoidal voltages such as those produced by some solid state
inverters.
The present invention may be used in connection with equipment observing
and measuring only two power states, such as on and off or on and standby.
Electrical devices typical of this are electrical audio devices visual display
devices. This is to say that the present invention can function by observing
and
measuring at least two functional states of the device or group of devices as
need be.
For example, an audio visual (AV) set up may consist of a number of individuat
components such as a TV screen, an amplifier and a DVD player, each of
which may be required to be on in order for the unit to function correctly.
The
present invention, through monitoring True RMS power, is able to adapt to
determine the various states of the equipment and their power needs, thereby
dynamically responding to the changing power supply requirements when
different components are attached to the power supply control device.
In this manner, the power supply control device can adapt to the changing
needs of the electrical devices that are attached to it. For example, a user
may
at first attach a television power cord to the power supply control device,
which
will then automatically determine at least two functional states of the
television.
The determination of states of the single television unit is as explained in
relation to the computer device, however, the user may then later add an
additional electrical device, such as an amplifier that is to be connected to
the 25 television.
When the amplifier is first switched on it assumes a Standby mode. When
mains power is applied, the power consumption is measured at a'fast' rate and
the Standby power for the device or collection of devices is extracted from
this
data. The algorithms used in the power supply control device analyse the
absolute power measurements and power fluctuations to determine if any
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19
device is operating and out of standby mode. The lowest power measurement
in the absence of power usage fluctuations is stored as the total standby
power
for the television and amplifier. This variable is then incremented by a
certain
amount so that any power reading below that value implies that both the
television and amplifier are in standby mode.
This new value is referred to as the 'Modified Standby Power Level'. This
allows
for any 'noise' or inaccuracies in the measurements. When the power
measurement for the device or collection of devices drops below the modified
standby level for a period of time, for example 30 seconds, the power supply
control devace will remove mains power from the AV system.
The Standby power level is again confirmed when the power supply control
device re supplies power to all devices placing them in an OFF Standby state
while making sure there are no power fluctuations.
The absence of power fluctuations and a decrease in steady state power below
the computed standby value implies a reduction in the number of collective
devices while an increase steady state power in the absence of power
consumption fluctuations implies an increase in the number of electrical
devices
in the collection connected to the power supply control device.
In this case power is not immediately removed from the television system but
in
the absence of any remote control activity for a period of say 3 hours, power
is
removed from the AV system. Power is then re-applied for the purpose of
computing the standby power level for this new configuration. Figure 8 shows a
flow chart of this method in comparison with the method shown in Figure 9.,
which is for computer electronic devices.
Figure 8 shows a method of the present invention in which the first step 600
is
when the power supply control device finds the Off Standby Power Level, which
is the level of power or cumulative level of power used by the device or
devices
aftached thereto. The power supply control device then waits 610 to receive a
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signal from a remote device, such as an IR or radio frequency signal from a
remote device, and once received power is supplied to all the attached
devices.
Power usage of the devices is then continuously monitored through real time
monitoring and fluctuations in power 620 are detected the system then
5 determines that the device is active and operating and the power to the
device
is maintained 625. If no power fluctuations are observed then the power supply
control device determines if the power level matches that of the predefined
Off
Standby Level at step 630.
If the power measurement matches the predefined Off Standby Level then the
10 power to the devices is then shut off and the systems return the step 610
monitoring for IR or radio frequency. If the devices are determined not to be
at
Off Standby Level, such as when a steady state power level is observed with no
power fluctuations then the system then looks for any remote IR or radio
frequency signals that would be an indication of use at step 640. If such
signals
15 are observed then power to the devices is left on, step 625, but if no
signals are
observed by the system for a predefined period, for example 4 hrs, step 650,
and if no activity is monitored during this time then the system determines
that
the observed power usage may be the New Standby Power Level and all
devices are switched off. The system then re supplies power to the devices
20 and monitors the power usage of the devices. If a steady state is observed
with
no powerfluctuatians then the system determines that this is the New Standby
Power level. The system will then removes power from the devices and the
monitoring of IR and radio frequencies signal, step 610, is continued.
In this manner it is then possible to add additional electronic devices to the
power supply control device or remove electronic devices from the power
supply control device and the system will then be able to continuously monitor
the cumulative power needs of the devices and as required establish new Off
Standby Power Levels required for the devices. This enables the system to be
dynamic and self-learning, avoiding the need for the user to continuously
change settings and monitor any power usage.
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21
The power-supply control device is thus able to adapt to change in power usage
because:
1. Power consumption in equipment when in Standby Mode has very
minor or no power level fluctuations.
2. Power consumption in equipment when operating has significant power
level fluctuations.
3. The power supply control device is able to sample and measure True
RMS Power in a very short time, thus enabling it to monitor power
fluctuations which indicate that a device is operating and hence not in
Standby mode.
True RMS power monitoring requires that the power supply control device is
able to determine the operational state of the attached electronic device or
devices. The RMS power is an average measurement of power over a defined
period of time. In mains electrical power measurements the smallest interval
of
power measurement which is useful in determining power consumption is half
(0.5) a cycle of the mains power frequency, i.e. 10 ms @ 50Hz. Hence an
instantaneous measurement of RMS power in this application can be an
average over 10 ms to 5 seconds and is typically less than 0.5 seconds.
Although the invention has been herein shown and described in what is
conceived to be the most practical and preferred embodiment, it is recognised
that departures can be made within the scope of the invention, which is not to
be limited to the details described herein but is to be accorded the full
scope of
the appended claims so as to embrace any and all equivalent devices and
apparatus.
