Analysis and design of a new choke less interleaved ZVS forward-flyback converter

This paper presents an interleaved active-clamping zero-voltage-switching (ZVS) forward-flyback converter without output choke. The presented topology has two active-clamping circuits with two separated transformers. In this converter the main switch of any converter also acts as auxiliary switch for the other one, so only two switches are required and there is no need to additional switches to achieve ZVS operation. Because of interleaved operation of the converter, the output current ripple will be reduced. The proposed converter can approximately share the total load current between two secondaries. Therefore, the transformer copper loss and the rectifier diodes conduction loss can be decreased. The output capacitor is made of two series capacitors which reduce the peak reverse voltage rectifier diodes. The circuit has no output inductor and has a few semiconductor elements such that the adopted circuit has a simpler structure, lower cost and suitable for high power density applications. Detailed analysis and design of this new converter are described. Then simulation results with an ac input voltage of 85-135 Vrms, an output voltage 12 V and output current 20 A verified the validity of the proposed converter.