METHOD FOR REGULATING A VOLTAGE AND CIRCUIT THEREFOR

摘要

A voltage regulator (10) having an undervoltage protection circuit 11 and a method for protecting against an output voltage out being less than a predetermined level. The voltage regulator has an undershoot limitation circuit (11) coupled between a feedback network (30) and a regulation section (42). A power factor correction circuit (46) is connected to the regulation section. An output voltage out from the power factor correction circuit (46) is fed back to the feedback network (30), which transmits a portion of the output voltage to the undershoot limitation circuit (11). If the output voltage is greater than the predetermined voltage level, a switching circuit portion (34) of the undershoot limitation circuit (11) transmits a normal control signal to the regulation circuit (42). If the output voltage is less than the predetermined voltage level, the switching circuit portion transmits an enhanced control signal to the regulation circuit. The enhanced control signal quickly brings the output voltage up to at least the minimum desired level.