Apparatus and method for controlling power supply for use with computer peripheral device

A peripheral equipment comprising:

• means for receiving a power signal reflecting a power supply status of said computer system through a signal cable;
• a switching circuit for switching to provide power supply from a power supply source for automatic operation of said peripheral equipment;
• a microcomputer for generating a power control signal in response to said power signal reflecting said power supply status of said computer system via said signal cable;
• and
• a power control circuit for controlling switching operations of said switching circuit to provide the power supply for automatic operation of said peripheral equipment in response to said power control signal said power control circuit comprising:
• a first resistor for loading said power control signal from said microcomputer,
• a photocoupler connected to said first resistor and disposed to turn on and off in dependence upon said power control signal supplied thereto;
• a second resistor connected to said photocoupler;
• and
• a transistor having a base electrode connected to said to photocoupler via said second resistor and having conducting electrodes disposed between a reference voltage terminal of said power supply source and a ground terminal.

A peripheral equipment of a computer system comprising:

• means for receiving a power signal reflecting a power supply status of said computer system through a signal cable;
• a switching circuit for switching to provide power supply from a power supply source for automatic operation of said peripheral equipment;
• a microcomputer for generating a power control signal in response to said power signal reflecting said power supply status of said computer system via said signal cable;
• a power control circuit for controlling switching operations of said switching circuit to provide the power supply for automatic operation of said peripheral equipment in response to said power control signal;
• and
• said switching circuit comprising:
• a first resistor loading said power control signal output from said microcomputer;
• a switching transistor having a base electrode connected to said first resistor and principally electrical conduction electrodes respectively connected to receive said power signal reflecting a power supply status of said computer system via a diode and a second resistor, said switching transistor disposed to turn on in response to said power control signal applied from said microcomputer;
• and
• a relay having relay terminals connected to both input and output terminals of said diode.

A computer system, comprising:

• a main unit including at least a central processing unit for operation, a power supply source providing power supply, a power switch operable to provide the power supply for operation, and a video card providing a power signal reflecting an electrical power status of said main unit by indicating whether electrical power is being applied to said main unit and providing a composite video signal including a video signal and synchronization signals for a visual display;
• a display unit electrically connected to said main unit, via a signal cable, receiving said power signal from said main unit, via said signal cable, to enable automatic operation of said display unit, and receiving said composite video signal from said main unit, via said signal cable, to enable said visual display of an image, said display unit comprising:
• a signal connector connected to said signal cable and providing said power signal for allowing the display unit to automatically shut down when the main unit is manually shut down, and allowing power to be applied to the display unit automatically when power is supplied manually to the main unit, and providing said composite video signal for said visual display of an image;
• a microcomputer generating a power control signal in response to said power signal provided from said signal connector reflecting said electrical power status of said main unit;
• and
• a switching circuit disposed between said signal connector and said microcomputer for switching allowing the display unit to automatically shut down when the main unit is manually shut down, and allowing power to be applied to the display unit automatically when power is supplied manually to the main unit in response to said power control signal by automatically applying and automatically interrupting provision of the electrical power to said display unit in dependence upon said power control signal.