Patent ID: 7466566

Claim:
A DC-AC converter, comprising: a transformer having a primary winding and at least one secondary winding; a first and a second semiconductor switches connected in series via said primary winding for allowing current to flow from a DC power source through said primary winding in a first direction; a third and a fourth semiconductor switches connected in series via said primary winding for allowing current to flow from said DC power source through said primary winding in a second direction; a current detection circuit for detecting the current that flows through a load connected to said secondary winding to thereby generate a current detection signal; a triangular wave signal generation circuit for generating a triangular wave signal; a PWM control signal generation circuit for generating a PWM control signal by comparing said triangular wave signal with an error signal generated on the basis of said current detection signal; an intermittent-operation control circuit adapted to set said error signal to a substantially zero level during an OFF period of said intermittent operation, gradually increase the error signal upon transition from an OFF state to an ON state; and gradually decrease the error signal upon transition from an ON state to an OFF state, and a logic circuit that operates on the basis of said PWM control signal to generate a first switch signal for turning on said first semiconductor switch; a second switch signal for turning on said second semiconductor switch; a third switch signal for turning on said third semiconductor switch; and a fourth switch signal for turning on said fourth switch in such a way that a first simultaneously OFF period is established during which said first and fourth switches are simultaneously turned off, and a second simultaneously OFF period is established during which said third and second switches are simultaneously turned off, and that the direction of the current flowing through said primary winding is changed from one direction to the other when the magnitude of said current is zero.