Design and analysis of a DC-DC converter for EVs battery charger

A detailed analysis and circuit implementation of a ZVS high output current and high power density converter with an active clamping circuit, ripple current reduced filter, and transformer isolation are presented. To reduce to voltage stress of the main switch in the converter an active clamping circuit is employed to provide ZVS for both main switch and axillary switch and the clamping capacitor is also used to recycle the energy stored in the leakage inductor and magnetizing inductor of both of the two isolation transformers. Four filter inductors are adopted in the circuit to reduce the current ripple of the output side and the usage of transformer provides galvanic isolation for security. Two transformer which is series connected in primary side and parallel in secondary side are used to double the turn ratio of the transformer in order to ensure the switch operating under a more stable switching duty ratio. In this paper the operating principle is analyzed in detail and the design consideration is also presented. The output-voltage feedback controller based on state-space averaging technique under small-signal assumption is built. Simulation Model and a prototype circuit especially used in electrical vehicle battery charging power system based on the proposed converter are built to verify the analysis of the proposed converter.