Asymmetrical pulse width modulated resonant DC/DC converter topologies

Asymmetrical pulse width modulated (APWM) DC-DC resonant converter topologies which exhibit near zero switching losses while operating at constant and very high frequencies are presented. The converters include a bridged chopper to convert the DC input voltage to a high frequency unidirectional AC voltage which in turn is fed to a high frequency transformer through a resonant circuit. The bridged chopper has two switches which alternately conduct. The duty cycles of the conduction of the switches are complementary with one another and are varied to control the output voltage. Three resonant circuit configurations which are suitable for this type of control are presented. Frequency domain analysis of the converter is given and performance characteristics are presented. Experimental results for a 48 V to 5 V, 30 W converter show an efficiency of 88% at a constant operating frequency of 1 MHz