Dimming control of metal halide lamp with high power factor

A high power factor dimming control for high intensity discharge lamp (HID) is presented in this paper. The system configuration consists of a power factor pre-regulator, a full-bridge inverter, and a series-resonant tank. The power factor pre-regulator, based on a boost converter and diode rectifier, is controlled to produce sinusoidal line current with high power factor and low current harmonics. The phase-shift PWM scheme is adopted for inverter drive. In this control approach, the constant switching frequency with variable duty cycle is implemented for dimming control. The series-resonant parallel-loaded circuit is used to drive the metal halide lamp (MHL), one of the high intensity discharge lamps. Finally, experimental results of a 70 W MHL hardware prototype are presented to verify the characteristics of high power factor and dimming control of electronic ballast