A MHz Electronic Ballast for Automotive-Type HID Lamps

The compatibility of the Current Sourcing Push Pull Resonant Inverter (CS-PPRI) with the driving requirements of HID lamps designated for automotive headlight applications was investigated theoretically, by simulation and experimentally. The study reveals that a based ballast (CS-PPRI) complies with the automotive requirement of very fast warm up. The experimental ballast was run under Zero Voltage Switching (ZVS) at a nominal switching frequency of 1.29MHz while the pre-ignition switching frequency was 124KHz. Warm up time to 80% after cold ignition was about 1 0 s e c o n d s . the nominal power. However, since the lamp voltage during warm up is low (about 20V), the current drive during warm up should reach about 7-8 time the nominal current, i.e. about 3-4 A. Considering the fact that the warm up time lasts few seconds, the ballast must be designed to current levels which are much higher than the nominal ones. The objective of this study was to examine and evaluate the potential application of the Current-Sourcing Push-Pull Parallel-Resonance Inverter (CS-PPRI) topology [2] as a ballast for low wattage HID lamps designated as automotive headlights [5, 6]. Special attention was paid to three major points: 1. To permit the application of an external igniter (rather than using a multiresonance ignition scheme [2]) so that ignition pulses of very high voltage can be realized.