Self-Driven Synchronous Rectification Scheme for Wide Range Application of DC/DC Converters with Symmetrically Driven Transformers

Synchronous rectifiers are widely used in low voltage and high current DC/DC converters to reduce conduction power loss. For popular and reliable topologies, such as Half-bridge, Push-pull and Phase-shifted Full-bridge, the application of self-driven synchronous rectification has design challenges due to the existence of dead times. Existing solutions are not suitable for wide input voltage ranges. This paper presents a new self-driven scheme which properly combines the signal from the transformer and output inductor to drive the MOSFETs. This method provides a suitable solution for wide range input application, since the risk of exceeding the gate voltage rating is greatly reduced. The synchronous rectifier is driven during all the conduction period, and thus greatly reduces the power loss. The influence of the leakage inductance in practical application is also analyzed. Experimental results based on a 36-75V input, 2.5V/30A output prototype are shown to verify the proposed scheme.