Power supply circuit utilizing voltage and current resonance for reducing switching loss

A power supply circuit comprising:

• a DC power source;
• switching means including a switching element for switching a DC input from the DC power source to convert the DC input to AC and outputting AC from an output terminal thereof, the AC changing between two different potentials;
• series resonance means provided in series to current flowing from the output terminal of the switching means for generating current resonance;
• parallel resonance means provided in parallel to voltage produced at the output terminal of the switching means for generating voltage resonance;
• DC output control means for rectifying and smoothing an AC input supplied from the switching means through the series resonance means and the parallel resonance means;
• and
• switching control means for controlling the switching element of the switching means so as to intermittently turn on the switching element,
• wherein said switching control means, after turning on of the switching means, turns off the switching means when current flowing through the switching means has been reduced substantially to zero by the series resonance means and, after turning off of the switching means, turns on the switching means when voltage applied to the switching means has returned substantially to a voltage immediately before turning off of the switching means by the parallel resonance means, said series resonance means comprises capacitance and inductance connected in series.