Microchip’s Digital Power AC/DC Reference Design unit works with a universal input voltage range and produces three output voltages, with a continuous power output rating of 300Watts. The front-end Power Factor Correction (PFC) boost circuit converts universal AC input voltages to a 420VDC bus voltage. A full bridge transformer isolated buck converter, incorporating a phase-shift Zero Voltage Transition (ZVT) circuit, produces 12VDC @ 30Amps from the 420VDC bus. The phase-shift ZVT converter also provides output-voltage isolation from the AC mains input. A multi-phase synchronous buck converter then produces 3.3VDC @ 69Amps from the 12VDC bus, and a single-phase buck converter produces 5VDC @ 23Amps from the 12VDC bus.
The reference design is powered by one of Microchip’s new dsPIC33F “GS” series of DSCs, which controls the PFC boost circuit and the primary-side ZVT full-bridge circuit. A second “GS” series dsPIC33F monitors the 12VDC bus voltage and controls the four buck converters.