A novel low-cost high-reliability igniter for metal halide lamps

Metal halide lamps have very serious acoustic resonance problem. The most widely used method to achieve acoustic-resonance free is low-frequency square-wave electronic ballast with an additional pulse igniter. Compared with high frequency resonance ignition, it needs more devices, such as sidac, thyristor, diac and so on, which increase the complexity and decrease the reliability of the igniter. This paper proposes a novel igniter without any extra switch device and feedback control circuit. High voltage ignition pulses can be obtained by utilizing the quick polarity inversion of output voltage of the full-bridge (FB) inverter. The location of the ignition pulse is just near the peak of the output voltage of the FB inverter, which is beneficial to the arc stability after the lamp starts up. Moreover, the igniter will not influence the steady-state operation of the lamp. Theoretical analysis and experiment results of a prototype for 70W MH lamps both have verified the effectiveness of the igniter.