Analysis, design and implementation of active clamp zero voltage switching converter with output ripple current cancellation

The system analysis and circuit implementation of an active clamp converter with current doubler rectifier to reduce the voltage stress of the switching device and the current stress of the transformer secondary winding is presented. An active clamp circuit based on one auxiliary switch and one clamp capacitor is used to recycle the energy stored in the transformer leakage in order to minimise the spike voltage at the transformer primary side and reduce the voltage stress of the switching devices. The resonant behaviour, based on the output capacitance and leakage inductance of the transformer during the transition interval between the main and auxiliary switches in the proposed converter, is used to achieve zero voltage switching. Therefore the switching losses of the switching devices are reduced. For the output stage, the current doubler rectifier offers ripple current cancellation at the output capacitor and reduces the current stress of the transformer secondary winding. The winding turns of the current doubler rectifier are also reduced compared with the center-tapped rectifier. The circuit configuration and operating principle of the proposed converter are analysed and discussed. The design considerations of the circuit are presented. Finally experimental results for a 150W(5V/30A) prototype are presented to verify the theoretical analysis and circuit performance.