High efficiency electronic ballast for metal halide lamp

Abstract

A high efficiency electronic ballast for large power metal halide lamp includes a power input circuit, a power factor correction circuit, a secondary power supply, a control circuit, a half bridge power converter, a resonant starting circuit, and lamp current on/off detector. The half bridge power converter has two DC block output capacitor to protect the converter when the output is shorted to ground. The operation frequency of the converter is chosen in the weak area of the acoustic resonant to avoid the acoustic resonant in the lamp. The control circuit adds a method for deep frequency and amplitude modulation and delay control function to the converter. For fine sweep pass through the output resonance point for igniting high voltage, two sweep rate control circuits are added. The metal halide lamp can be operated with very stable from starting to normal operation with high electronic ballast system efficiency.

Dependencies are inferred from the claim text.