Patent ID: 7378889

Claim:
A pulse width modulation device with a power saving mode controlled by an output voltage feedback hysteresis circuit, used in a power supply and varying with the load of the power supply to control and output a drive signal transmitted to a power switch, comprising: a hysteresis comparison circuit extracting a feedback voltage, a high threshold voltage and a low threshold voltage; wherein the feedback voltage, the high threshold voltage and the low threshold voltage are executed a comparison and hysteresis operation to output a blanking signal; a pulse width modulation control unit extracting a detecting current signal and the feedback voltage to output a modulation signal after a comparison operation is executed which the detecting current signal varies with the current value passing through the power switch; an OR gate connected to the hysteresis comparison circuit and the pulse width modulation control unit for receiving the blanking signal and the modulation signal to output a reset signal; and a synchronization signal output unit connected to the OR gate for receiving the reset signal and an oscillation signal to output the drive signal.