SWITCHING POWER SUPPLY APPARATUS

摘要

PROBLEM TO BE SOLVED: To make a switching power apparatus stably even when it is in a high load state with a duty cycle of not less than 50%. SOLUTION: A control circuit 15 has an oscillator 21, which generates and outputs a switching signal applied to a switching device 14, an error amplifier 22, which generates an error voltage signal VEAO from an auxiliary power supply voltage Vcc and outputs the signal VEAO; a rain current detection circuit 23 which detects a drain current ID applied to the switching device 14 and outputs it as a device current detection signal VCL; a slope compensation circuit 40 which adds a triangular wave signal TRW to the device current detection signal VCL and outputs a compensation voltage signal V2 compensating the device voltage detection signal VCL; and a drain current detecting comparator 24 which compares the error voltage signal VEAO with the compensation voltage signal V2 and outputs a pulse width determining signal VPLS as the comparison result.