Patent ID: 8488341

Claim:
A switching mode power supply (SMPS) comprising a rectifying unit transforming alternating current (AC) power input from outside into direct current (DC) power, a main transformer transforming and outputting the rectified DC power, a pulse width modulation control unit controlling output voltage by applying a pulse signal to a primary winding of the main transformer, and a feedback control unit controlling an output signal of the pulse width modulation control unit by detecting output voltage of the main transformer, wherein the pulse width modulation control unit includes a pulse width modulation integrated circuit device including a high voltage terminal of 85 VAC to 600 VAC, the switching mode power supply further comprising: a first state transform unit, including: a second photo diode; and a second photo transistor that forms a photo coupler with the second photo diode and is included between the AC power input unit receiving the AC power and a high voltage terminal (HV) of the pulse width modulation integrated circuit device, wherein the first state transform unit further comprises any one of a battery and a large-capacity capacitor supplying power to the second photo diode, wherein the first state transform unit, comprises: a timer circuit, comprises: a timer capacitor charging output voltage of the main transformer; a timer resistance consuming voltage charged by the timer capacitor when the switching mode power supply enter a low power state; and a timer transistor that is operated by the voltage consumed in the timer resistance.