Electronic ballast with modified valley fill and charge pump capacitor for prolonged filaments preheating and power factor correction

A new circuit, modified valley fill (MVF) combined with a resonant inductor of the self-excited resonant inverter and charge pump capacitors (CPCs), is presented to achieve high PF electronic ballast providing sufficient preheat current to lamp filaments for soft start maintaining low DC bus voltage. The MVF can adjust the valley voltage higher than half the peak line voltage. The CPCs draw the current from the input line to make up the current waveform during the valley interval. The measured PF and THD are 0.99 and 12%, respectively. The lamp current CF is also acceptable in the proposed circuit. The proposed circuit is suitable for implementing a cost-effective electronic ballast.