A novel dimmable electronic ballast with very high frequency

An electronic ballast with very high frequency can avoid the intrinsic acoustic resonance problem of HID lamps. The ballast consists of a PFC converter circuit and an inverter circuit The inverter circuit includes a half bridge inverter and a T type filter running on very high frequency. Based on the T type filter, wide dimming ability can be achieved within a narrow frequency variation range. At the same time the lamp current is kept a perfect sine wave, which means low lamp current crest factor is achieved. Frequency modulation with power control is implemented to dim the lamp. Its validity is proved by both theoretical analysis and experimental results.