New single-stage cost-effective high power factor electronic ballasts with series/parallel resonant inverters

Abstract

With the adoption of international standards such as IEC61000-3-2, there is a requirement to develop the electronic ballast for fluorescent lamp which can perform line current harmonic reduction and high input power factor correction (PFC). Among various filtering techniques, the active power factor corrector with a boost converter has been proven to be an effective method. The boost-type PFC circuit is one of the most popular configurations due to the advantages such as low ripple and good regulation of DC-link voltage, low flickering, etc. Nevertheless, the boost converter circuits lead to higher circuit complexity and thus higher product cost. The designer of fluorescent lamp ballast is faced with a variety of consideration and trade-offs that significantly affect the performance and cost of the final product. In this thesis, several circuits are presented to obtain high power factor correction ability for cost-effective electronic ballast, which is composed of a self-excited series-resonant inverter / parallel resonant inverter and a power factor correction stage with only passive elements such as small capacitors and several diodes. In the electronic ballast using voltage-fed series-resonant inverter, the power factor correction stage is mainly composed of valley fill DC-link which modified of improved from the conventional valley fill circuit and charge pump capacitors. The modified of improved valley fill circuit can adjust the valley voltage to above half the peak line voltage by changing the value of capacitor connected to the point where the high frequency resonant voltage is occurred in the resonant inverter. To draw the input current from the input line when the line voltage is smaller than the valley voltage, small charge pump capacitors are inserted between the input side and the resonant inverter. Also, to give an filaments preheating ability, small auxiliary resonant tank may be used. The operation mode analyses and experimental results are pres...