Abstract
A single-stage electronic ballast with dimming feature and unity power factor is presented in this paper. With the introduction of synchronous switches, the proposed single-stage converter is formed by combining the boost converter and the half bridge series-resonantparallel-loaded inverter. The proposed circuit is capable of increasing the system reliability while reducing both its size and weight. The power stage is operated above its resonant frequency to achieve zero voltage switching. In order to obtain a high power factor, the pre-regulator a boost converter, is operated in discontinuous conduction mode (DCM). The dimming feature is carried out by using pulse-width modulation (PWM) and variable-frequency control simultaneously. In addition, the output voltage of the power factor correction stage can be regulated. Th巳analysis and design of an electronic ballast for fluorescent lamps operated at high frequency is presented. The plasma model is used to replace the lamp in the analysis; thus, a negative dynamic resistant characteristic of the lamp can be presented explicitly. Finally, the effectiveness of the proposed topology is demonstrated by software simulation and hardware measurement.