Improvement of self-oscillating electronic ballast with high power factor: A combination of charged-pump and valley-fill

This paper proposes a novel 36W/220V_rms/50Hz of half-bridge inverter self-oscillating electronic ballast for a fluorescent lamp with high power factor and low line input current harmonics. The system performance can be improved by combining together with a charged pump and valley fill circuit. Details of design and circuit operation are described. This ballast is developed to reduce a number of ICs controlling power electronic switches that are costly and sizeable. Instead of these ICs, This ballast employs self-oscillation method to control power electronic switches. The combination of a bridge rectifier, current source charge pump with valley fill circuit to improve power factor and Series - Resonant Parallel - Load Inverter (SRPLI) are main concept. This electronic ballast is designed and tested to find the proper frequency and signal to stimulate the operation of power electronic switches to trigger fluorescent lamp suitably. The experimental results show that the proper frequency of the prototype is around 40 kHz with input power factor of 0.988, THDi 4.7% at full load and efficiency of more than 90%.