Self-excited continuous conduction mode ZVS flyback converter

Making use of the transformer leakage inductance, a self-excited continuous conduction mode ZVS flyback converter that performs self-excitation operation with a continuous conduction mode and zero voltage switching is proposed. In this converter, by turning off of one switch element, another switch element is turned on. By setting a delay time, ZVS operations are realized alternately. A new control scheme is used for independent control of each on-time of two switching elements. By means of the extended state-space averaging method, the static and dynamic characteristics are derived analytically. Then, the design equation, ZVS operating condition, and frequency characteristic of the transfer function are derived. Based on the analysis, a converter is designed and is tested experimentally for confirmation of the validity of the approach. In the experiment, efficiencies of 94.1% and 90.0% are attained, respectively, with outputs of 24 V/6 A and 24 V/15 A for an input of 141 VDC. In comparison with the converter operated in the critical current mode, the output is about 1.8 times as large and is 360 W. © 2005 Wiley Periodicals, Inc.