Patent ID: 7002814

Claim:
A power supply controlling device of an electronic equipment, comprising: a first rectifying unit rectifying an alternating voltage supplied from a power supply cord and outputting a first rectified voltage; a transformer comprising a primary winding wired to receive the first rectified voltage from the first rectifying unit, and a secondary winding coupled to the primary winding; a first switching unit performing an on/off operation by supplying current to the primary winding; a pulse width modulating unit controlling the on/off operation of the first switching unit; and a power supply controlling unit outputting a signal controlling the pulse width modulating unit, wherein the pulse width modulating unit switches the first switching unit to on/off depending on a reception of a power-on signal which is supplied externally, wherein the power supply controlling unit comprises: a USB interface unit; a power supply switch selecting a power on/off signal in response to a power on/off signal received from a host computer connected through the USB interface unit and outputting a trigger signal indicative thereof; a second switching unit connected to a power supply terminal of the USB interface unit and turned on based on the trigger signal from the power supply switch; and a photo coupler comprising a first light emitting device and a phototransistor applying a signal to the pulse width modulating unit, wherein the first light emitting device is connected to the second switching unit and disposed to emit the light in response to the turn-on signal of the second switching unit, and the signal corresponds to an emission of light emitting from the first light emitting device.