GB2401494A - Peripheral power supply control device - Google Patents

Abstract

A device controls the power supply to computer peripheral devices by monitoring an output of a computer in order to determine if the computer is turned on or off A switch interrupts the external power supply to peripheral devices of the computer system when the computer is turned off A single operation of shutting down the PC of the system thus results in all peripheral devices being isolated from their power supplies. The device monitors the power supplied to the computer keyboard and mouse to determine if it is on or off.

Description

POWER SUPPLY CONTROL DEVICE

This invention relates to computer systems, and more particularly to a device for controlling the power supply to peripheral devices within such a system.

In recent years, the power supply shut down operation of a personal computer (PC) has become under the control of the operating system of the computer, rather than under the control of a manual power on-off switch.

When the PC has been shut down the peripheral devices within the system typically switch to a standby mode. However, they are not isolated from their power supplies and still consume power. Thus, if a user wishes to turn all appliances off, this has to be carried out manually for each device. In a domestic environment, all of the peripheral devices are likely to be in the same location as the PC itself, and it may be a relatively simple task to switch off all peripheral devices. However, in a more complicated system where a PC is an embedded part of a product, there may be a number of peripheral devices distributed over an area, for example motors, cameras and lights. In this case, switching off all peripheral devices becomes more onerous.

According to the invention, there is provided a device for controlling the power supply to computer peripheral devices within a computer system, comprising: circuitry for monitoring an output of a computer in order to determine if the computer is turned on or off; and a switch for interrupting the external power supply to peripheral devices of the computer system in response to a determination that the computer is turned off, wherein the switch does not interrupt the external power supply if it is determined that the computer is turned on.

This device monitors whether or not the computer is turned on, and when the computer is turned off the external power to the peripheral devices of the system is interrupted. In this way, the single operation of shutting down the PC of the system results in all peripheral devices being isolated from their power supplies. The device monitors an output of the PC simply to determine if the computer is turned on or off, and thereby operates independently of the operating system of the PC, and requires no software. By interrupting the external power supply to the peripheral devices, rather than switching them to a standby mode, there is reduced power consumption and a reduced risk of fire. This reduced power consumption may be particularly significant in large factory or office environments. The shutdown operation is also carried out centrally at the PC and all associated peripheral devices can be fumed off automatically even if they are positioned in remote locations.

If the detemmination is that the computer is fumed on, then the external power supply to the peripheral devices is not interrupted.

The monitoring circuitry may be for detecting a voltage supply to a mouse or keyboard of the computer system. A voltage supply is not provided to the mouse and keyboard of a PC when the computer is in a standby mode. Thus, the voltage supply to the mouse or keyboard provides an indication that the computer is fumed on and is not in standby mode.

The monitoring circuitry may comprise a light emitting diode which is driven by this voltage supply, and a light sensitive element, responsive to the light emitting diode output, then controls the switch. In this way, an electro-optical control loop is established using inexpensive circuit components thus affording electrical isolation with minimal drain on the monitored signal. The light sensitive element may then comprise a TRIAC which controls the supply of power to a relay, with the relay operating the switch.

The device preferably has a mains input port, an unswitched mains output port and a switched mains output port. The switched mains output port is for the peripheral devices, and power is supplied to this port when the PC is fumed on. The unswitched mains output port is for the PC itself.

For the monitoring circuitry, the device preferably has a port for connection to the keyboard or mouse output port of a computer, and a port for connection to the keyboard or mouse. Thus, the device monitors the voltage supply sent to the mouse or keyboard for detection purposes. The signals sent to and received from the keyboard or mouse are not, however, affected and the device does not interrupt the supply of power to the mouse or keyboard.

The device may be a stand-alone device for location in the path of a mains power supply to the peripheral devices. For example, the device may be located in the vicinity of the mains plug socket used for the computer. It may then have a bank of additional plug sockets for the peripheral devices, which are each supplied with the switched mains supply. The peripheral devices then receive power through the device of the invention.

The device may be for integration into a personal computer and thus provide additional functionality for the computer itself. A second aspect of the invention thus provides a personal computer including a device of the invention. The computer then has a mains input port and at least one switched mains output port which acts as the power supply for the one or more peripheral devices.

According to a second aspect of the invention, there is provided a method of controlling the supply of external power to peripheral devices of a computer system, comprising monitoring an output of a computer in order to determine if the computer is turned on or off, and interrupting the external power supply to peripheral devices of the computer system in response to a determination that the computer is turned off and not interrupting the external power supply if it is determined that the computer is turned on.

In this description and claims the term "turned off" can include the computer being in a standby mode, in particular if this results in the output being monitored changing.

An example of the invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 shows a computer system using a device of the invention; Figure 2 is used to explain the functionality of the device of the invention; and Figure 3 shows one possible circuit design for the device of the invention.

Figure 1 shows a computer system 10 comprising a processor 12 and which optionally includes CD-ROM, DVD and disk drives, a monitor 14, keyboard 16 and mouse 18. The system 10 also includes two peripheral devices P1, P2. These may be any devices such as printers, scanners, lighting, cameras. In accordance with the invention, the system includes a device 20 which controls the supply of mains power to the peripheral devices P1, P2. As shown in Figure 1, the device 20 receives mains power from plug 22 and is thus provided in the path of mains power to the peripheral devices P1, P2. The operation of the device 20 is to interrupt this mains power when it is detected that the computer 12 is turned off. For this purpose, the device 20 has circuitry for monitoring an output of the computer 12, in order to determine if the computer is turned on or off. Most conveniently, the computer 12 provides power to the keyboard 16 and mouse 18 only when it is turned on (and not in standby mode). In the system of Figure 1, the power supply to the keyboard 16 is monitored by the device in order to determine if the computer is turned on or off. Thus, the keyboard output port of the computer 12 is connected to the device 20 by lead 24. The device 20 monitors the voltage supply line of the lead 24, but also provides an output for the keyboard 16. The keyboard signals are not affected by the device 20. The device 20 is thus connected to the keyboard 16 by lead 26. In the arrangement of Figure 1, the mouse 1 is connected directly to the computer 12 by lead 28.

The device 20 also provides mains power to the computer 12 by lead 30, and this power supply is not affected by the operation of the device 20.

When the device 20 detects that the computer is turned on, by the presence of a voltage supply on lead 24, it acts to switch mains power to the peripheral devices P1, P2 on leads 32, 34. When the device 20 detects that the computer 12 is turned off, by the absence of a voltage supply to the keyboard 16, it interrupts the mains power supply to the peripheral devices P1, P2. Thus, the device 20 has a number of switched mains outputs which are used for powering the peripheral devices.

Figure 2 shows more clearly the ports of the device 20. As shown, the device has a mains in-port 40, an uninterrupted mains out-port 42 for powering the computer 12, and a number of switched mains out-ports 44 for powering the peripheral devices.

To control the switching operation the device 20 effectively monitors the keyboard lead for power status and thus has a port 46 for connection to the keyboard 16 (or mouse) and a port 48 for connection to the computer port for the keyboard (or mouse).

In the example above, the device 20 is shown located adjacent the computer 12 and providing power to the peripheral devices P1, P2 from a single plug 22. The device 20 may have a bank of output ports for providing switched mains power to the peripheral devices, and these devices are not then plugged directly into the mains.

Alternatively, the device 20 may comprise part of a plug adaptor. In this case, the device may be located at the plug socket. It would then have a first uninterrupted socket for the PC and a bank of switched mains sockets for the peripheral devices. The keyboard (or mouse) lead would then follow a path from the keyboard to the plug socket and back to the computer 12.

When provided as a separate stand-alone device as described above, the device may be sold as an add-on for existing computer systems. As the device simply monitors the presence of a voltage at an output of the computer, it is independent of the operating system of the computer 12 and may therefore be used for any computer s system, provided there is an output from the computer 12 which carries a voltage when the computer is turned on and does not when the computer is turned off. For systems using remote controlled keyboards and/or mice, the device can interrupt the power supply to the infrared sensor, or else it may be appropriate to use a different output port from the computer for monitoring.

The device may, alternatively, be integrated into the computer 12 itself. This will essentially involve locating the device 20 shown in Figure 1 within the casing of the computer 12. This would not change the functionality at all.

There are numerous ways of implementing the circuitry for the device of the invention. Essentially, a voltage simply needs to be used to control the operation of a switch.

Figure 3 shows one possible circuit for implementing the device of the invention, and which provides a low power circuit using inexpensive components.

The mains input 40 provides a neutral in-port 50 and a live in-port 52. The uninterrupted mains output is provided by a neutral out-port 54 and a live out-port 56.

The mains in- and mains out- ports are therefore directly connected together.

A switch 58 is provided in the path of the live terminal 59 for the switched mains output 44. This switch 58 is controlled by a relay 60. The power for the relay 60 is derived from the live in-port 52 after voltage reduction and current limitation. This voltage reduction and current limitation is achieved with Zener diode 64, capacitor 68 and safety resistors 66. This provides a conventional capacitive dropper network to power the relay and minimise the current required from the monitored line. The Zener diode 64, diode 70 and smoothing capacitor 72 act as a rectifier for providing a smoothed do voltage supply to the relay 60. Supply of power to relay 60 does, however, require the light sensitive TRIAC 74 to be conducting. This light sensitive device 74 is responsive to the light output of light emitting diode 76 which is driven by the voltage supply line for the keyboard or mouse.

The device draws very low current from the voltage supply line to the keyboard or mouse, and this current is determined by the resistor 80. As shown, the device has input terminals 82 for receiving the keyboard connection from the computer and output terminals 84 for connection to the keyboard.

The current drawn by the resistor 80 and diode 76 can be very low, for example milliamps is sufficient to provide a light output for controlling the light-sensitive TRLAC.

The device of the invention not only enables shutdown to be performed simply by turning off the computer, but also enables all peripheral devices to be powered when the computer is turned on again.

It should be understood that the specific example shown in detail above is only one possible implementation of the invention. Whilst some other variations have been mentioned above, various other modifications to the system will be apparent to those skilled in the art.

Claims (12)

1. A device for controlling the power supply to computer peripheral devices within a computer system, comprising: circuitry for monitoring an output of a computer in order to determine if the computer is turned on or off; and a switch for interrupting the external power supply to peripheral devices of the computer system in response to a determination that the computer is turned off, wherein the switch does not interrupt the external power supply if it is determined that the computer is turned on.

2. A device as claimed in claim 1, wherein the circuitry for monitoring is for detecting a voltage supply to a mouse or keyboard of the computer system, the presence of a voltage supply indicating that the computer is turned on.

3. A device as claimed in claim 2, wherein the circuitry for monitoring comprising a light emitting diode which is driven by the voltage supply, and wherein the device further comprises a light sensitive element for controlling the switch.

4. A device as claimed in claim 3, wherein the light sensitive element comprises a TRIAC which controls the supply of power to a relay, the relay operating the switch.

5. A device as claimed in claim 4, further comprising a voltage reduction stage for reducing a mains voltage and providing this reduced voltage to the TRIAC, and a rectifier for converting an ac voltage at the output of the TRIAC to a do voltage for actuating the relay.

6. A device as claimed in any preceding claim, wherein the device has a mains input port, a mains output port and a switched mains output port.

7. A device as claimed in claim 6, wherein the device has a port for connection to the keyboard or mouse output port of a computer and a port for connection to the keyboard or mouse.

8. A device as claimed in any preceding claim, wherein the device comprises a stand-alone device for location in the path of a mains power supply to the peripheral devices.

9. A device as claimed in any one of claims 1 to 7, wherein the device is for integration into a personal computer.

10. A personal computer including a device as claimed in claim 9, wherein the personal computer has a mains input port and at least one switched mains output port.

11. A computer system comprising a computer, a device as claimed in any one of claims 1 to 9 and at least one peripheral device, wherein the power supply to the peripheral device is controlled by the device for controlling the power supply.

12. A method of controlling the supply of external power to peripheral devices of a computer system, comprising monitoring an output of a computer in order to determine if the computer is turned on or off; and interrupting the external power supply to peripheral devices of the computer system in response to a determination that the computer is turned off and not interrupting the external power supply if it is determined that the computer is turned on.