Patent ID: 7209374

Claim:
A capacitor-input positive and negative power supply circuit that drives an inductance load, for use in a digital amplifier, comprising: a transformer having secondary windings with a center tap; at least two rectifier devices that rectify voltages generated across said secondary windings with the center tap; positive and negative capacitors that receive outputs rectified by said at least two rectifier devices, respectively; at least two switching circuits connected in parallel with said at least two rectifier devices, respectively; a control device that controls said switching circuits such that said switching circuits conduct alternately during a time period over which said rectifier devices conduct, whereby imbalance in voltage between a voltage across said positive capacitor and a voltage across said negative capacitor is eliminated; and a detector circuit that detects a time period over which a sinusoidal wave inputted to said rectifier devices exceeds a predetermined level, and wherein said control device controls said switching circuits such that said switching circuits conduct during the time period detected by said detector circuit.