A novel variable frequency soft switching method for Flyback converter with synchronous rectifier

This paper proposes a variable frequency zero-voltage-switching (ZVS) control method for Flyback converter with synchronous rectifier. A lossless snubber capacitor is paralleled to the drain and source of primary switch to absorb the leakage inductance energy. The conventional passive clamp circuit with RCD is omitted, and no auxiliary switch or winding is needed. Synchronous rectifier is turned on additionally for a short time before primary switch is on. The negative secondary current transferred to primary side is used to discharge the auxiliary capacitor and achieve ZVS operation. Experimental results from a 16V/4A prototype circuit are provided to demonstrate the converter performance. Both Soft-switching and high efficiency are achieved in the entire input voltage range at both full load and light load conditions.

[1]  I.W. Hofsajer,et al.  Passive component integration in a ZVS flyback converter , 2006, Twenty-First Annual IEEE Applied Power Electronics Conference and Exposition, 2006. APEC '06..

[2]  Milan M. Jovanovic,et al.  Design considerations and performance evaluations of synchronous rectification in flyback converters , 1998 .

[3]  C. T. Choi,et al.  Control of an active clamp discontinuous conduction mode flyback converter , 1999, Proceedings of the IEEE 1999 International Conference on Power Electronics and Drive Systems. PEDS'99 (Cat. No.99TH8475).

[4]  J.A. Cobos,et al.  A low power topology derived from flyback with active clamp based on a very simple transformer , 2006, Twenty-First Annual IEEE Applied Power Electronics Conference and Exposition, 2006. APEC '06..

[5]  Fred C. Lee,et al.  Utilization of an active-clamp circuit to achieve soft switching in flyback converters , 1994, Proceedings of 1994 Power Electronics Specialist Conference - PESC'94.

[6]  Yu-Kang Lo,et al.  Active-Clamping ZVS Flyback Converter Employing Two Transformers , 2007, IEEE Transactions on Power Electronics.

[7]  M. Youn,et al.  A new zero voltage switching active clamp flyback converter , 2004, 2004 IEEE 35th Annual Power Electronics Specialists Conference (IEEE Cat. No.04CH37551).

[8]  Koosuke Harada,et al.  Analysis and optimization of a nondissipative LC turn-off snubber , 1988 .