Efficient, high power density, high power factor converter for very low dc voltage applications

摘要

A high efficiency, high power factor, low voltage power converter includes a dual active bridge converter (DABC) having transformer-coupled primary- side and secondary-side bridge connections of switching devices and providing two output voltages. One output voltage drives a resonant boost converter coupled in series between an ac rectifier for rectifying an ac line voltage and the DABC. The boost converter, which is controlled by frequency modulation, boosts a dc bus voltage above the peak line voltage, thereby providing a high power factor. The other output is a low dc voltage which is regulated by controlling the phase shift between the voltages respectively produced by the primary- side and secondary-side connections of switching devices of the DABC. Advantageously, the leakage inductance of the DABC transformer coupling the primary and secondary sides of the DABC is efficiently used for energy transfer therebetween such that an output filter inductor is not needed. Moreover, use of synchronous rectifiers in the DABC allows for active control on the secondary side of the DABC transformer, further increasing efficiency. Zero-voltage switching of the switching devices of the DABC allows for an increase in operating frequency and hence an increase in power density.