Power converter system with synchronous rectifier output stage and reduced no-load power consumption

摘要

A power converter circuit may convert alternating current signals into direct current signals. A load may be powered from output terminals that are provided with the direct current signals. The power converter circuit may have a transformer with primary and secondary sides. A transistor on the primary side may be controlled using a pulse width modulation controller. A diode may be coupled in series with the secondary side of the transformer and the load. To improve efficiency at larger load currents, a synchronous rectifier control circuit may modulate a transistor on the secondary side that is coupled in parallel with the diode. The synchronous rectifier control circuit may monitor voltage pulses on the transistor on the secondary side or may make direct load current measurements to ascertain how much load current is flowing. Under low or no load conditions, synchronous rectification can be inhibited to improve efficiency.

主权项

1. A power converter that converts alternating current (AC) power to direct current (DC) power, the power converter comprising:
a transformer having a primary side terminal and a secondary side terminal; a transistor connected to the primary side terminal; a first control circuit configured to control the transistor; a second control circuit comprising (i) a filter that includes a first terminal and a second terminal and (ii) a comparator, the first terminal connected to the secondary side terminal and the second terminal connected to the comparator, wherein an output of the comparator is based on a frequency of pulses passing through the filter in response to the transistor switching; and a synchronous rectifier circuit connected to the secondary side terminal and the comparator, wherein the synchronous rectifier circuit is activated according to the output of the comparator.