Class D current-driven transformer center-tapped controllable synchronous rectifier

We present analysis and experimental results for a phase-controlled, synchronous, transformer center-tapped rectifier. The rectifier is driven by a resonant inverter. A digital control adjusts the phase in the driver of the rectifier MOSFET's. The output voltage is regulated while maintaining a 94% maximum and a 80% minimum efficiency for a 30% line swing, and 50% efficiency for a load swing of 400% from full power. Experimental results are presented for a 10 W rectifier with an output voltage of 3.3 V. Theoretical calculations agreed well with the experimental results, with certain deviations due to the nonidealities of the transformer. The center-tapped topology allows for high efficiency even at 3.3 V and simplifies the control design, providing simple regulation.