Patent ID: 7236375

Claim:
A dc-ac converter, comprising: a dc power supply; a transformer having a primary winding and at least one secondary winding; a semiconductor switch circuit for passing a current alternately in a first direction and a second direction from said dc power supply to said primary winding; a load connected to said secondary winding; a current detection circuit for detecting the current flowing through said load to generate a current detection signal indicative of the current detected; a voltage detector circuit for detecting the voltage impressed on said load to generate a voltage detection signal indicative of the voltage detected; a triangular wave signal generation circuit for generating a triangular wave signal; a slow-start circuit for generating a slow-start signal that rises slowly during a startup of said load; a PWM control signal generation circuit for generating a PWM control signal, said PWM control signal generation circuit adapted to receive said triangular wave signal, current detection signal, voltage detection signal, and slow-start signal; generate an error signal based on said current detection signal and voltage detection signal; automatically select either one of said error signal and said slow-start signal based on the magnitudes of said signals; and compare the selected signal with said triangular wave signal to generate said PWM control signal, and wherein said semiconductor switch circuit is switched on and off-based on said PWM control signal.