Reduced bus voltage integrated boost high power factor circuit

Abstract

A condensed power supply circuit for powering a gas discharge lamp with bi-directional current reduces duty cycle by increasing dead time. The circuit comprises an arrangement for supplying d.c. power from an a.c. voltage, a series half bridge converter, a boost converter, a resistor-capacitor delay circuit associated with a gate to control dead time, and a snubber capacitance for facilitating zero voltage switching to fill the entire dead time. The series half-bridge converter alternately impresses a d.c. bus voltage from a bus conductor across a load circuit first with one polarity and then with an opposite polarity. The series half-bridge converter includes a first switch, a second switch, and a switching control circuit for alternately switching on the first and second switches. The boost converter comprises a boost capacitor, a boost inductor, and means for periodically connecting a load end of the boost inductor through a low impedance path to the ground conductor, thereby charging the boost inductor. The present invention reduces duty cycle via an increase in dead time. The resistor-capacitor delay circuit, associated with a gate, is used to control dead time. The snubber capacitance, which facilitates zero voltage switching to fill the entire dead time range, has a value set by the resistor-capacitor delay circuit.