Abstract: A compact, low cost high intensity discharge lamp ballast apparatus which can carry out normal ballasting without extinction at discharge start includes a DC-AC inverting booster circuit, a first resonance circuit, and a second resonance circuit. The DC-AC inverting booster circuit includes a DC-AC converter transformer for converting a DC voltage fed from a DC power supply to an AC voltage in response to switching on and off of FETs, boosting the voltage. The first resonance circuit includes a leakage inductance connected in series with the secondary winding of the DC-AC converter transformer, and a first resonant capacitor connected in parallel with the secondary winding. The second resonance circuit includes a metal halide lamp, an ignitor transformer for producing a voltage to start lighting of the metal halide lamp, and a second resonant capacitor.

Abstract: A ballast for a vehicle metal halide lamp is simplified using a DC-AC one-step-boost high frequency ballast system. To satisfy requirements specific to a metal halide lamp, a discharge developing capacitor is installed on a primary side of a transformer in parallel with a DC power supply, ensuring discharge development after a breakdown. To reduce the size and increase the operating voltage of the transformer, a booster circuit and voltage-doubler circuit are installed on the primary side and secondary side of the transformer, respectively. To reduce the size of the transformer and achieve a stable discharge, the ballast frequency is swept within a range between the specified minimum frequency and maximum frequency so that the center frequency is from 80 kHz to 120 kHz, and the same frequency is unsustained for more than 10 msec.