Patent ID: 7589981

Claim:
A dc-ac converter, comprising: a dc power supply; a transformer having a primary side and at least one secondary side; a switch circuit having a first and a second semiconductor switches connected in series with each other via said primary side to allow a primary current from said dc power supply to flow through said primary side in a first direction, and a third and a fourth semiconductor switches connected in series with each other via said primary side to allow a primary current from said de power supply to flow through said primary side in a second direction; a current detection circuit for detecting a detection current associated with the current through a load connected to said secondary side; a voltage detection circuit for detecting the voltage supplied to the load connected to said secondary side to generate a detection voltage; and a first error amplifier for comparing a first detection voltage in accord with a detection current detected in said current detection circuit with a first reference voltage, thereby generating an output in accord with the error between them; a PWM circuit for comparing a feedback signal formed based on the output of said first error amplifier with triangle wave signal series, thereby generating a PWM signal; a second error amplifier for comparing a detection voltage detected in said voltage detection circuit with a second reference voltage, thereby generating an output in accord with the error between them; and a logic circuit for generating a drive signal for driving said first semiconductor switch, said second semiconductor switch, said third semiconductor switch and said fourth semiconductor switch in accordance with said PWM signal; wherein said feedback voltage is controlled by the output from said second error amplifier.