Bi-frequency control for quasi-resonant converters

A new control technique for quasi resonant converters, called the bi-frequency control, is proposed. This control technique can regulate the output of quasi-resonant converters at two fixed switching frequencies without adding an auxiliary switch. The basic principle of the bi-frequency control is presented. Based on a zero-voltage-switching buck converter, the theoretical analysis and design procedures are given. PSPICE simulations are used to demonstrate the operation, and a 50 watts prototype is implemented to verify the analytic work. >