Acoustic-resonance-free electronic ballast for automotive HID lamps

A novel cost-effective and acoustic-resonance-free electronic ballast used to drive automotive high intensity discharging (HID) lamps that utilise a constant lamp power control scheme is proposed. The presented ballast is comprised of a buck-boost flyback converter to provide negative DC voltages and a half-bridge-type inverter to supply the lamp with low-frequency, square-wave AC voltage/current. Owing to its low-frequency operation, no acoustic resonance occurs on the automotive HID lamps. Design guidelines and experimental results are demonstrated for a 35 W automotive HID lamp prototype ballast operating at 400 Hz switching frequency with battery input DC voltage of 12 V.