WO1993007558A1

WO1993007558A1 - Power management system

Info

Publication number: WO1993007558A1
Application number: PCT/CA1992/000441
Authority: WO
Inventors: Dale K. Tiller; William H. Kemp; Victor J. Shiddler; Guy R. Newsham
Original assignee: National Research Council Of Canada
Priority date: 1991-10-04
Filing date: 1992-10-05
Publication date: 1993-04-15
Also published as: GB9121207D0; AU2660692A

Abstract

A power management system for use in association with desktop computers and like equipment powered from a mains supply, comprises: a monitor for monitoring Input/Output activity on the computer; a device for generating a time-out signal due to the absence of Input/Output activity during a predetermined period of time; a device for storing user-selectable criteria determining the response of the system to said time-out signal; a device for generating a data signal at an external interface port of the desktop computer based on said stored criteria and the presence of the time-out signal; and an external power supply device, comprising a power inlet for connection to the mains supply, a plurality of power outlets for supplying power to the desktop computer and associated peripheral equipment, controllable switches associated with each power outlet for selectively connecting and disconneting the power supply thereto in response to a control signal, an interface connectable to the external interface port for receiving said data signal therethrough, and a processor responsive to the data signal to generate the control signals for the controllable switches associated with the power outlets in accordance with the stored user-selectable criteria. The system can result in substantial energy savings due to the reduction in wasted energy caused by computers being left on while unattended.

Description

POWER MANAGEMENT SYSTEM

This invention relates to a power management system for desktop computers .and like equipment, such as computer terminals and periperals that are normally powered from the mains supply.

Although it has not previously been recognized as a major problem, computer-related equipment accounts for a substantial proportion of electricity consumption in large office buildings. Casual observation of many offices will reveal that computers and associated peripherals often remain switched on even though they are not in use. Typical daytime loads for desktop computers, their peripherals and other electronic office equipment have been estimated at about 10 - 20 w/m². Furthermore, electronic office equipment is expected to have the highest growth rate of all end- uses of electrical energy in the North American commercial sector. By 1995 there will be up to 65 million personal computers in business use in the United States alone, with estimates for office equipment electricity use for 1995 ranging from 25TWh. - 130 TWh., (lTWh. = 1 billion KWh.).

Although this growth in electrical power consumption is well documented, what has not been previously recognized is how much of the total power consumption of EDP equipment and peripherals is wasted.

Not only does wasted energy result directly from the consumption of the computer equipment, it also result from increased load on building cooling systems required to dissipate the heat generated by unused computers and peripherals. Although building cooling load will be climate dependent, and in some cases the heat generated by powered but unused computers will offset a winter heating load, heating will usually be non-electrical, whereas building cooling will almost always be electrical.

Every computer and peripheral consumes electrical energy expressed by the following formula:

^Etotal = ^pwatts ^{x Time}

Where,

^E _total ⁼ tot l energy consumption, (Watt Hours) ; P_{wat s} ⁼ load, when switched on, (Watts) ; Time = time EDP equipment is on, (hours) .

Following the formula above, a reduction in energy consumption can be accomplished by both reducing device wattage and/or length of activation time.

Technical innovations can improve the efficiency of electronic data processing equipment, but potential energy savings will not be fully realized if this equipment is left running when it is not being used.

While power saving devices that de-activate certain power hungry devices, such as the screen and hard disk drive, after a period of inactivity are used in laptop computers due to the obvious energy storage limitations of the internal battery, such devices are directly controlled by the computer's memory bus and cannot be conveniently retrofitted to existing units. Furthermore, they have not been applied to mains- powered devices. An object of the present invention is to provide a power management system that results in significant power savings for PC users.

According to as first aspect of the invention there is provided a power management system for use in association with desktop computers and like equipment powered from a mains supply, comprising: monitoring means for monitoring Input/Output activity on said computer; means for generating a time-out signal due to the absence of Input/Output activity during a predetermined period of time; means for storing user- selectable criteria determining the response of the system to said time-out signal; means for generating a data signal at an external interface port of the desktop computer based on said stored criteria and the presence of said time-out signal; and external power supply means, comprising a power inlet for connection to the mains supply, a plurality power outlets for supplying power to the desktop computer and associated peripheral equipment, controllable switch means associated with each said power outlet for selectively connecting and disconnecting the power supply thereto in response to a control signal, interface means connectable to said external interface port for receiving said data signal therethrough, and processor means responsive to said data signal to generate the control signals for the controllable switch means associated with said power outlets in accordance with said stored user-selectable criteria.

The power management system in accordance with the invention is a retro-fit product for use with a.c. grid powered computers and peripherals, which more closely tailors the power on time of these computers and peripherals to the user activity of these devices without materially affecting the performance of the computer system.

The above system, which .is retrofittable, for example, to a standard Macintosh or IBM-based PC, can result in considerable overall energy savings.

The monitoring means can, for example, monitor Input/Output on the computer by monitoring the activity on the at least one Input/Output buffer, such as the keyboard buffer, the mouse buffer, the video buffer, the serial or parallel port buffers, and the LAN adapter buffer.

The user-selectable criteria can include the - duration of inactivity required to generate a time-out and the affect on the respective power outlets upon the occurrence of a time-out. Some or all of the devices can be shut down on time-out. Alternately, the devices can be shut down sequentially with the computer being the last device to be shut down. Also, the user may switch off certain equipment directly through the computer, i.e. through the keyboard or by activating certain buttons on a standard GUI interface with the mouse.

The external interface port can be the keyboard interface port, in which case the interface means can be connected between the keyboard interface port and the keyboard to permit normal keyboard signals to pass therethrough. The processor means is responsive to the appearance of said data signals at the interface to generate the appropriate control signals for the controllable switch means. The user can also set the system to inhibit shut down if an application is still active. Alternately, the system can be set to transfer the contents of the RAM to disk prior to shut down so that when the computer is restarted it automatically reverts to the state it was in prior to shut down.

The invention also provides retrofittable power saving apparatus for use with desktop computers and like equipment powered from a mains supply, comprising a power inlet for connection to the mains supply, a plurality power outlets for supplying power to a desktop computer and associated peripheral equipment, controllable switch means associated with each said power outlet for selectively connecting and disconnecting the power supply thereto in response to a control signal, interface means connectable to an external interface port in said desktop computer for receiving distinctive data through said port controlling the state of said apparatus, and processor means responsive to said data to generate the appropriate control signals for said switch means.

The apparatus as claimed can further comprise means for monitoring the phase angle of said power outlets, and means for controlling said switch means to manage and reduce the departure from unity of the power factor of the individually connected EDP devices.

The apparatus can also include an infrared occupancy sensor for detecting the presence of an individual at the computer station and generating an inhibit signal in the presence thereof. The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows the overall mean daily computer use profiles for all 94 computers, from January 13, 1992 to March 8, 1992;

Figure 2 shows the mean number of hours per computer per week before (solid line) and after (dashed line) the application of reminder stickers urging computer users to switch off their machines when they were not in use;

Figure 3 shows the mean number of hours per computer per week before (solid line) and after (dashed line) the application of a power management system in accordance with the invention;

Figure 4 is a diagram illustrating the layout of a desktop computer with a power management system in accordance with the invention;

Figures 5a and 5b are a block diagram of the power management system in accordance with the invention;

Figures 6a to 6c show snapshots of a typical GUI control screen for the power management system;

Figure 7 is an exploded view of a power management system in accordance with the invention;

Figure 8 is a flow chart of the TSR control program in the computer; and Figure 9 is a flow chart of the control program for the microcomputer in the power bar.

In order to evaluate the. system, the power consumption and electrical operating characteristics of several hundred typical desktop computers and peripherals were measured on-site using a BMI 3060 Power Profiler (198 computers, 112 monitors, 41 printers, 6 plotting devices, and 7 external hard disk drives) . The measured plug load for these devices was 3.4 W/m² (0.3 W/ft²), which although lower than the 14.0 W/m² (1.3 W/ft²) load calculated from nameplate ratings, represents a major part of the load of an office building.

Prior to the research leading to the invention, no direct data were available on desktop computer use profiles, or the portion of time that a machine is used when it is turned on. Energy modelers have relied on anecdotal evidence, metered plug loads from which office equipment and desktop computer loads are extracted, or indirect estimates of desktop computer use patterns based on time-share mini and mainframe computer system logon records.

The actual desktop computer use patterns on 94 machines at three Canadian Federal Government sites located in the Ottawa area were monitored using custom computer activity monitoring software.

Referring to Figure 1, the top curve shows the mean number of minutes in every hour the computers were switched on. The bottom curve shows the mean number of minutes in every hour there were keystrokes (or keystrokes/mouse clicks for Macintosh computers) : note the expected drop in mean number of minutes per hour there were keystrokes over lunchtime.

These data were used to .calculate the effect on use profiles of switching computers off after specified time intervals of inactivity. These results are depicted on the two middle curves in Figure 1. The two middle curves show the effects of switching off the computer after 60 minutes or 15 minutes keyboard/mouse inactivity. If computers were switched off after 60 minutes of keyboard/mouse inactivity, reductions in mean computer energy consumption of 58 percent would be achieved, with a 35 percent reduction in mean peak electrical power demand. Even shorter inactivity switches (e.g., 15 minutes) would result in even greater energy consumption and peak demand savings.

These data establish that desktop computers are actually used only a small fraction of the time they are switched on, even during the daytime. Significant energy conservation can be achieved if computer on-time is more closely tailored to actual use.

In order to measure the effectiveness of a power management system, reminder stickers were placed on or near test computers urging users to switch off their machines when they were not using them. Stickers were installed near 33 computers, and computer use was monitored for another 8 weeks. Figure 2 shows that the reminder stickers initially produced reductions in mean computer energy consumption of 14 percent, with a 3 percent reduction in mean peak electrical power demand. However, these savings were not maintained over the eight week period after the stickers were first installed, since mean computer energy consumption and peak electrical demand returned to pre-sticker levels, at the end of the 8 week period.

A power management system in accordance with invention was installed on sixteen computers at another of the three monitoring sites, and collected computer use data for another eight weeks. As shown in Figure 3 shows the mean number of hours per computer per week before (solid line) and after (dashed line) the installation of the power management system. After installation, mean computer energy consumption fell by 63 percent, with a mean reduction in peak electrical power demand of 41 percent. Video display unit (VDU) mean energy consumption was reduced by 82 percent.

The predicted savings due to the power management system at this site, with a 60 minute keyboard/mouse inactivity switch off were: a 71 percent reduction in electrical energy consumption, and a 44 percent reduction in mean peak demand. The measured savings are remarkably close to the predictions. The main reason reductions are slightly lower than predicted is that users could opt for the system not to switch off their computer if an application program was open. This option did not affect the switching of VDUs, and the observed reduction in on-time of independently switchable VDUs of 82 percent is almost identical to the prediction of on-time reduction after 15 minutes of keyboard/mouse inactivity of 83 percent.

Figure 4 shows a computer 1, which can, for example be an IBM PC or Macintosh computer, an associated keyboard 13, monitor 6, power bar 7, printer

16, and desk lamp 17. The computer 1, printer 16, lamp

17, and monitor 6 are all plugged into respective, independently switchable outlets 10, 11 on the power bar 7. The power bar 7 is connected to the 120VAC 60 Hz mains supply. The power bar 7 is also connected into the keyboard port. Keyboard connector 14 is plugged into adapter 15. In .accordance with the invention, the power 7 can selectively turn off its power outlets, for example, after a predetermined period of inactivity.

As shown in more detail in Figure 5, the personal computer 1 comprises an internal power supply 2, a motherboard 3 with a data and logic bus 4, microprocessor 100, which in the case of an IBM-based PC, would be, for example, an INTEL 486 microprocessor, and a random access memory 101.

The motherboard 3 is connected through monitor interface 5 to screen monitor 6. The monitor 6 and computer 1 are plugged into the power bar 7 by means of plugs 8 and 9, which are accommodated by respective outlets 10 and 11 in the power bar 7.

The power bar 7 is connected to the AC mains supply through line 24. The power from line 24 is distributed to the outlets 10, 11 (outlet #1, outlet #2) under the control of TRIAC control devices 23, which permit the power outlets 10, 11 to be selectively switched on and off under the control of the microprocessor 21.

The motherboard 3 also comprises a keyboard interface port 12 connected to peripheral interface adapter 32 on the motherboard and normally directly connected to keyboard 13 by connector 14 and line 33. Strobe and interface signals are normally carried through the keyboard interface 12 and connector 14 to the keyboard 13.

The power bar 7 automatically turns off peripheral devices and computers on the basis of a lack of activity from the computer's input/output devices. The power bar 7 also allows manual on/off control of the computer and peripherals. These manual on/off functions are operating conveniences and are not directly related to the energy saving function of The power bar 7.

Sensing of human activity with the computer is accomplished by a control software loaded into the random access memory 101 of the computer. This program known as a Terminate-Stay-Resident program, (TSR) , runs in "background" mode to the user's application program. Generally the user is not aware of the TSR program.

The TSR is a control program (see Figure 8) written in assembly language which becomes RAM resident when the program is installed from the users hard disk drive, (usually during power up on execution of AUTOEXEC.BAT for DOS based machines) .

The TSR program continually monitors the state of the computer 1 and control the power bar 7. In particular, the TSR detects changes in state of the keyboard buffer register 30 located within the computer's system memory. However, other registers that which change data values based on some human activity may be employed. This activity may be the pressing of a key on the keyboard, moving or "clicking" a mouse or any other input/output device which the specific computer is capable of recognizing.

The TSR may also detect changes in state of various registers located within the computer's memory map which change data values based on some machine to computer activity. This may be the exchange of data between a server computer and slave computer on a LAN system.

The change of state over a period of time would indicate to the power bar 7 TSR that a human has interacted with the computer indicating activity or that another machine has interacted with the computer also indicating activity. For example, monitoring serial ports will inhibit shut-down if the computer is communicating with a modem.

Provided that activity is present over a preset period of time, the power bar 7 TSR will remain inactive. Should the user stop interacting with the computer, (no activity) , the TSR program will compare the elapsed time of inactivity with a set of user programmed criteria concerning the action to be taken when inactivity reaches a time programmed into the rules.

When a time-out occurs, (inactivity time = inactivity time from rules, i.e. time-out), the TSR sends a command to the power bar 7 to turn off the device for which the rule matches. By way of example, a user may state that the printer attached to the power bar 7 outlet number three is to be turned off when inactivity time with the computer = five minutes.

The TSR can be called by the user, for example, by activating a hot key, and the criteria for power management entered. Desirably this is done using a graphical user interface, (GUI) with mouth activated control buttons to permit entry of the desired criteria. For example, the user may wish to set the predetermined time delay before a time out occurs, and which components will be switched off upon the occurrence of a timer. The user may wish to switch off all outlets, and thus the entire system, including possibly extraneous features .such as desk lamps, or he may wish only to switch off certain equipment, such as peripherals. The user selected criteria are stored at addresses determined by the TSR in the ram 101.

Also, the user can selectively switch on and off the peripherals in real time through the GUI. For example, the user may wish to call up the TSR and manually switch off the printer. This may be more convenient than manually switching it off through hardware.

The setup menu allows the user to specify by peripheral name, each device plugged into The power bar 7's six switched outlets. Note that outlet number 0 is reserved for the computer.

a) The user may then select a pre-defined time in minutes from the last activity with the computer, until that outlet will turn off.

b) The computer's "turn off" time is always greater than any other device.

c) When The power bar 7 is turned on, all six outlets will be automatically switched to the "on" position.

d) The computer will turn on and execute its initialization program which will contain the TSR.

e) The TSR will reside in RAM in the computer and be invisible to the user of the computer. f) As long as the computer is being accessed by the selected input/output device (s), the TSR will not communicate with the power bar 7 unless a manual outlet turn on/off command is called from the user menu by hot-key or pull down.

g) Should the user of the computer leave the computer on and not operate the computer, the TSR will start counting the number of minutes since the activity on the selected I/O port. When the time since the last activity equals the time-out period selected for a specified peripheral, the TSR sends a "turn off" signal to the power bar 7 over the keyboard communications link to turn off that peripheral device.

. h) This will repeat until the last timer value, (the longest, also associated with the computer) , is reached. When the time out period is reached for the computer, the TSR sends the turn off command for port 0. The computer will now be turned off by The power bar 7.

Figures 6a - 6c show snapshots of a typical GUI control screen, and it will be seen how the user can select power management criteria according to his or her particular preference.

During operation of the computer, the TSR runs in the background continuously monitoring the status of keyboard buffer 30. If no activity occurs during the preset time, for example, thirty minutes, the TSR causes a unique data signal to be transmitted through the keyboard interface 12. This is recognized by microprocessor 21, which acts upon the data signal to control the TRIAC with the data carried thereby. For example, if the user has determined that power to all peripherals should be switched off after thirty minutes of inactivity, the TSR causes an appropriate data signal to be transmitted through the keyboard interface and this is picked by lines 2.0 and acted on by microprocessor 21, which in turn turns control signals to all TRIAC control circuits 23 causing them to switch off outlets 10, lϊ.

After a period of inactivity, as the time-out set by the use is approached, the TSR in the computer 1 first causes a series of warning messages that the computer is about to be shut down to appear on the monitor screen. These can be accompanied by audible warning signals. For example, warning messages can be displayed five minutes and one minute prior to shut down. These warning period can be set by the user.

When time-out occurs, the TSR causes a data byte to appear at the keyboard interface 12. This is recognized by the microprocessor 21 in the power bar 7 as an instruction to take appropriate action in accordance with the stored criteria.

When the power bar 7 receives a command to turn off the computer, a special control sequence is carried out as follows:

a) The TSR determines, (from its rules and inactivity criteria) , that the computer is to be shut¬ down.

b) The TSR terminates or saves the user application program and/or data as previously defined in its rule set. c) The TSR sends the "computer off" command to the computer keyboard interface buffer, which is in turn sent over the keyboard interface by the Peripheral Interface Adapter integrated .circuit.

d) The power bar 7 turns off the power outlet number 10, (computer is plugged into this outlet) .

e) The power bar 7 supplies power to the computer's keyboard through a blocking diode 35, which allows the power bar 7's internal power supply to keep the computer's keyboard active without supplying power to the computer.

f) When the user wishes to use the computer, pressing any key on the computer's keyboard will cause a data signal to be sent to the computer and to the power bar 7 through the interface cable.

g) The computer is turned off, and the computer does not receive the data signal.

h) The power bar 7's internal microcomputer receives the data signal from the computer's keyboard. Upon receipt of this data signal, the power bar's microcomputer 21 activates the appropriate control triac which in turn applies power to the computer.

i) The computer will perform its boot sequence and re-loads the power bar 7 TSR which will start performing its inactivity monitoring and comparison to the previously defined rules.

j) The user application progra (s) may now be accessed. When the computer 1 is shut down, because of the special keyboard "T" cable with blocking diode 35, +5 volts direct current is supplied to the keyboard from the power bar's own power supply. This voltage does not enter the computer because of the blocking diode 35. This voltage ensures that the keyboard remains powered on and active. In this state:

a) All The power bar 7 outlets will remain off until someone presses any key on the keyboard.

b) Because the keyboard is still active, a keyboard strobe signal is sent each time a key is pressed. However since the computer is turned off, the signal is only "sensed" by the power bar 7.

c) When The power bar 7 receives this strobe signal, the power bar 7 activates port 0 which turns on the computer.

d) When the computer enters its normal power up sequence, AUTOEXEC.BAT for DOS computers, for example, is executed which starts the TSR control program running. This then checks the setup table and determines which, of the peripheral ports must also be turned on, if any. (This would be important if the computer's monitor was attached to port 1) .

e) The power bar 7 and the TSR will then continue to function as described earlier in the text.

While in the described embodiment, the power management system monitors the keyboard interface, other external interface ports can be monitored, for example, serial or parallel ports, LAN adapters, mouse interfaces, and any other interface communicating with external devices.

Referring to Figure 7, the robust moulded plastic casing 50 support outlets 10, 11 and circuit board 51 mounting control circuitry 52 and triacs 53 forming part of the triac control circuits associated with each power outlet. An LED 54 for each outlet indicates the status of its associated outlet.

The power bar 7 is designed to allow a non- technical person to connect the power bar 7 to their own computer system and associated peripherals. The chassis is designed to look similar to a standard power bar. The power bar 7 is constructed on a single, double sided printed circuit board which houses all of the necessary sub systems, including, a 120 volt a.c. input from the building power mains, low voltage power supply to drive the power bar 7 logic and supply necessary power to the user's keyboard when the computer is turned off, a keyboard strobe and power supply interface with serial bi-directional communications interface, micro-coded logic containing operational parameters for program control of the power bar 7, six three conductor power outlets, switching triacs for the individual control of each outlet, snubber networks for EMI and electrical surge suppression, and a circuit for controlling the power factor of controlled electrical loads by phase angle control of switching triacs.

Physically, the power bar 7 resembles a standard power bar assembly, having six outlets. Each outlet has a snubber protected switching triac which under control of a custom programmed microcontroller integrated circuit, will allow the control of each individual outlet for a total capacity of 1,500 watts for the entire assembly.

Relays can be used instead of triacs; however triacs will allow phase angle control of power factor related to the controlled load. By monitoring phase angle at the power outlets, the power factor of all connected EDP devices can be monitored and its departure from unity minimized.

The power bar 7 has only one interface cable which connects to the desktop computer. This cable is a custom "T" cable which connects between the computer and the computer's keyboard. This cable contains a blocking diode 35, which supplies power to the keyboard from, the power bar 7 assembly. This will allow the keyboard to remain on even when the host computer is turned off. The cable will also "intercept" signals received from the host computer when the key board is activated.

The power bar 7 is divided into three sections, namely:

1) 120 volt power control and switching system,

2) Logic and micro-coding,

3) Interfacing to computer system.

The building a.c. mains is routed to the power bar 7 via a standard power cord 24. Once the a.c. mains is inside the power bar 7, it is routed to the logic power supply and to the switching triacs, used to operate the peripheral equipment. The logic power supply converts the 120 volt mains supply to the necessary voltages required to operate The power bar's internal microcomputer. It also generates the 5 volt power supply required to operate the computer keyboard when the computer is turned off.

Switching power, (the a.c. mains) are routed to the 6 switched outlets. Neutral and Earth conductors are run in parallel to the six outlets and are not switched. Line one from the a.c. mains is run in a BUS to six triac devices, capable of turning line one on or off to the outlet associated with that particular triac. When a given triac is turned on by a signal from the microcomputer device internal to the power bar 7, Line one from the a.c. mains is connected to the outlet associated with the triac. The peripheral device attached to that outlet is therefore turned on.

Internal to the microcomputer 21, contained within the power bar 7, is a program which runs at all times that the power bar 7 is connected to the a.c. mains. This program is designed to do the following:

1) Receive serial data from the user microcomputer over the keyboard interface which is controlled by the control program.

2) Send serial data to the user microcomputer as directed by the control program.

3) Monitor the operation of the user's keyboard.

4) Send the necessary control signals to the six switching triacs. The TSR resident in the user's computer generates the necessary logic states to determine when a port should be turned on or off. When a state is determined, one of 12 control codes is sent to the power bar 7. These codes are, outlet #1 on or off, outlet #2 on or off and so on.

When the power bar 7 receives any of these control signals, it will act upon them as follows:

OUTLETS #2, #3, #4, #5 and #6 ON OR OFF:

When the control code to turn on or off any of the above outlets is received, The power bar 7 activates or de-activates the associated outlet and waits for further instructions.

When the control code for outlet 1 to turn off is received, that outlet will turn off. The power bar 7 will now monitor the keyboard strobe signal from the keyboard interface. When the keyboard interface strobes. The power bar 7 will turn on outlet #1.

This action is caused by the fact that the computer is to be connected only to outlet #1. When The power bar 7 receives the command from TSR control program to turn off outlet 1, the computer will be turned off. (The TSR will not run when the computer is turned off) .

Due to the blocking diode 35 in the keyboard "T" cable adapter, power will be sent from The power bar 7 only into the keyboard. A user pressing any key on the keyboard will cause the keyboard strobe to go active. This strobe is monitored by the power bar 7 and is assumed to be the "command" for the power bar 7 to turn on outlet #1, (which turns on the computer) .

Control of the power bar 7 is now transferred to the control program, once the computer runs its initialization programs and boots the control program.

The power bar 7 can also include a remote power-up facility, enabling it to be activated by telephone. For this purpose the power bar 7 includes a standard telephone jack 40 (Figure 5) through which it is connected to the public switched telephone network. The line detector 41 detects the presence of an incoming call causing the power bar to switch on the some or all of the outlets 10,11 and maintain them on while the line is in use. Which outlets are switched on by remote control can be set in advance through the set-up program. For example, it might be decided that there is no need to activate the printer when the computer is being accessed remotely. The power bar 7 also remains on for a predetermined time after the line has been dropped. This enables a remote user to access the computer by modem without leaving the computer on continuously and without interfering with the power management functions of the system. If a user leaves his desk without switching off the computer, the power- down sequence will be automatically be initiated after the preset period of time. If the user subsequently wishes, for example, to extract data remotely, he can do so by telephoning in to activate, and after allowing a suitable period of time for the computer to complete its power-up sequence, initiate modem file transfer.

Claims

Clai s :

1. A power management system for use in association with desktop computers and like equipment powered from a mains supply, comprising: monitoring means for monitoring Input/Output activity on said computer; means for generating a time-out signal due to the absence of Input/Output activity during a predetermined period of time; means for storing user-selectable criteria determining the response of the system to said time-out signal; means for generating a data signal at an external interface port of the desktop computer based on said stored criteria and the presence of said time-out signal; and external power supply means, comprising a power inlet for connection to the mains supply, a plurality power outlets for supplying power to the desktop computer and associated peripheral equipment, controllable switch means associated with each said power outlet for selectively connecting and disconnecting the power supply thereto in response to a control signal, interface means connectable to said external interface port for receiving said data signal therethrough, and processor means responsive to said data signal to generate the control signals for the controllable switch means associated with said power outlets in accordance with said stored user-selectable criteria.

2. A power management system as claimed in claim 1, wherein said monitoring means monitors Input/Output activity on the computer by monitoring the activity on at least one Input/Output buffer.

3. A power management system as claimed in claim 2, wherein said monitoring means monitors the keyboard buffer.

4. A power management system as claimed in claim 2, wherein said monitoring means monitors the mouse buffer.

5. A power management system as claimed in claim 2, wherein said monitoring means monitors the video buffer.

6. A power management system as claimed in claim 2, wherein said monitoring means monitors the serial port buffer.

7. A power management system as claimed in claim 2, wherein said monitoring means monitors the parallel port buffer.

8. A power management system as claimed in claim 2, wherein said monitoring means monitors the LAN adapter buffer.

9. A power management system as claimed in claim 1, wherein said user-selectable criteria include the duration of inactivity required to generate a time-out and the affect on the respective power outlets upon the occurrence of a time-out.

10. A power management system as claimed in claim 1, wherein said user-selectable criteria include the manual control of the power outlets through the computer.

11. A power management system as claimed in claim 1, further comprising means for generating said data signals at preset user-selectable times of day.

12. A power management system as claimed in claim 1, further comprising means for generating a data signal to restore power to said power outlets when the keyboard is pressed while power to the computer is off.

13. A power management system as claimed in claim 1, further comprising means for storing the contents of the computer random-access-memory on a permanent storage medium prior to disconnection of said power outlets, and means for restoring said contents to the random-access-memory after restoration of power to said outlets so as to restore the computer to its state prior to disconnection.

14. A power management system as claimed in claim 1, wherein said external interface port is the keyboard interface port, and said interface means is connected between said keyboard interface port and the keyboard to permit normal keyboard signals to pass therethrough, and said processor means is responsive to the appearance of said data signals at said interface means to generate the appropriate control signals for said controllable switch means.

15. A power management system as claimed in claim 1, further comprising an infrared occupancy sensor for generating an inhibit signal to inhibit disconnection of said power supply in the presence of an individual at the computer station.

16. Retrofittable power management apparatus for use with desktop computers and like equipment powered from a mains supply, comprising a power inlet for connection to the mains supply, a plurality power outlets for supplying power to a desktop computer and associated peripheral equipment, controllable switch means associated with each said power outlet for selectively connecting and disconnecting the power supply thereto in response to a control signal, interface means connectable to an external interface port in said desktop computer for receiving distinctive data signals through said port controlling the state of said apparatus, and processor means responsive to said data signals to generate the appropriate control signals for said switch means.

17. Retrofittable power management apparatus as claimed in claim 16, wherein said external interface port in the computer is the keyboard interface port, and said interface means is adapted to be connected between the keyboard interface port and the keyboard, said processor means being responsive to said distinctive data signals to generate appropriate control signals for said switch means.

18. Retrofittable power management apparatus as claimed in claim 16, further comprising means for monitoring the phase angle of said power outlets, and means for controlling said switch means to reduce the departure from unity of the power factor of the apparatus.

19. Retrofittable power management apparatus as claimed in claim 16, further comprising an infrared occupancy sensor for detecting the presence of an individual at the computer station and generating an inhibit signal in the presence thereof.

20. Retrofittable power management apparatus as claimed in claim 16, further comprising a telephone jack for connection to the public switched telephone network and means for activating said apparatus in response to an incoming call.