Single Stage High Power Factor Electronic Ballast for HID Lamps Using Differential Connection

This paper presents an electronic ballast topology for HID lamps using differential connection of DC/DC converters. The integration of power factor correction, lamp power control and inverter stages results in a single-stage electronic ballast that supplies the lamp with a low frequency symmetrical square voltage waveform, which avoids both the acoustic resonance phenomenon excitation and the lamp restarting. The ballast consists of a buckboost power factor correction converter and two bidirectional flyback converters connected to the lamp in a differential way. These converters are combined using only two switches that share the same source reference, thus resulting in a simple control circuit.