A 1 kW, 500 kHz front-end converter for a distributed power supply system

The analysis, design, and performance are discussed of a prototype high power-density converter suitable for use in the front-end of a distributed power supply system. The system delivers 1 kW to a regulated 40 V distribution bus from the rectified utility line. Its switching frequency is 500 kHz, and it uses a phase-shifted pulse-width modulation technique to avoid primary-side switching losses. The converter´s topology is a standard power MOSFET H-bridge that drives a transformer. The output of this transformer is rectified by a full bridge of Schottky diodes. The switches of this forward converter are operated in a fixed-frequency PWM mode. The dominant parasitic elements are the transformer´s leakage inductor, the MOSFETs´ output capacitors, and the rectifiers´ junction capacitors. Of these three groups of parasitic elements, only the leakage inductors do not result in a direct switching loss. To avoid MOSFET switching losses, the converter is controlled with a special gate-drive pattern that permits full recovery of the MOSFETs´ capacitive energy. At the same time this drive scheme gives zero-voltage switching for the MOSFETs. The converter´s efficiency at full load approaches 90%