Off-line regulator with pass device and associated method

摘要

An off-line regulator has a rectification circuit configured to rectify an AC line voltage into a rectified line voltage, a pass device coupled between the rectified line voltage and a first capacitor, and a converter. The pass device is configured to be turned ON or OFF according to a comparison signal indicating whether the rectified line voltage is over a threshold voltage. The first capacitor delivers an interim voltage into the converter which supplies power to a load. Wherein a second capacitor coupled across a driver which driving the pass device is charged by the first capacitor when the comparison signal is at a first state, and the driver is boosted when the comparison signal is at a second state.

主权项

1. An off-line regulator comprising:
a rectification circuit configured to rectify an alternating current (AC) line voltage into a rectified line voltage; a pass device having a first end, a second end and a control end, wherein the first end is coupled to the rectified line voltage; a comparator configured to compare the rectified line voltage with a threshold voltage and provide a comparison signal; a driver, having an input, an output, a first power end and a second power end, wherein the input of the driver is coupled to the comparison signal, and wherein the output of the driver is coupled to the control end of the pass device; a first capacitor, having a first end and a second end, wherein the first end of the first capacitor is coupled to the second end of the pass device, the first end of the first capacitor configured to provide an interim voltage, and wherein the second end of the first capacitor is coupled to a reference ground; a second capacitor, having a first end and a second end, wherein the first end of the second capacitor is coupled to the first power end of the driver, and wherein the second end of the second capacitor is coupled to the second power end of the driver; and a converter configured to provide power to a load, the converter having an input and an output, wherein the input of the converter is coupled to the interim voltage, and wherein the output of the converter is configured to provide a direct current (DC) output voltage; wherein the second capacitor is configured to be discharged when the comparison signal is at a first state, and wherein the second capacitor is configured to be charged by the first capacitor when the comparison signal is at a second state.