Patent ID: 7599197

Claim:
A power supply apparatus comprising: converting means for converting input AC power to DC power; switching means receiving said DC power and performing switching operation in accordance with a switching control signal, for converting said DC power to high-frequency power; a voltage transformer for transforming a voltage of said high-frequency power; rectifying means for rectifying the power as voltage-transformed by said voltage transformer; first detecting means for detecting a magnitude of said rectified power, a voltage of said rectified power, or a current of said rectified power and developing a first detection signal representative of the detected magnitude of power, voltage or current; error signal generating means for generating an error signal representative of the difference between said first detection signal and a predetermined reference signal; second detecting means for detecting a voltage value of said DC power and developing a second detection signal representative of the detected voltage value; triangular waveform generating means for generating a triangular waveform signal; and PWM comparing means for comparing said triangular waveform signal with a threshold value, which is a larger one of said second detection signal and said error signal, and generating a PWM control signal for making said switching means ON when said triangular waveform signal is equal to or larger than said threshold value.