Zero Voltage Switching Active Clamp Converter with Series-Connected Transformer

This paper presents the analysis, design and implementation of zero voltage switching (ZVS) active clamp converter with series-connected transformer. A family of isolated ZVS active clamp converter is introduced. The technique of the adopted ZVS commutation will not increase additional voltage stress of switching devices. In the adopted converter with series-connected transformer, each transformer can be operated as an inductor or a transformer. Therefore no output inductor is needed. To reduce the voltage stress of switching device in the conventional forward converter, active clamp technique is used to recycle the energy stored in the transformer leakage back into the input dc source. During the transition interval between two active switches, the resonant behavior based on the output capacitance of switches and transformer leakage inductance will turn on the body diode of switches. The operation principles, steady state analysis and design equations of the adopted converter are provided. Finally experimental results are presented taken from a laboratory prototype with 100 W rated power, input voltage of 155 V, output voltage of 5 V, and operating at 150 kHz.