Diodes as Pseudo-Active Elements in High-Frequency DC/DC converters

A new approach to realizing zero-voltage switching in high-frequency dc/dc converters is presented. Utilizing the parasitic associated with the diode stored charge, it is shown that the diode reverse current established for charge removal can be used advantageously to accomplish soft switching. The entire family of single-transistor dc/dc converters can be realized using the technique. The new converter topologies are seen to differ from their hard switched counterparts only by the presence of a resonant capacitor. It is also seen that device and component stresses are moderate as compared to existing quasi-resonant and resonant techniques. Converter analysis is seen to be rather complex as a result of the dominant diode nonlinearities, and no closed-form expressions are seen to be possible. Converter transfer characteristics are obtained through simulation, and operating limits are analytically obtained. The concept is validated by experimental results using buck-type converters rated at approximately 100 W and operating at frequencies around 1 MHz.