Fluorescent electronic ballast with high power factor: A combination charged-pump and valley-fill based on class DE inverter

This paper proposes fluorescent electronic ballast 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. The proposed electronic ballast is modified from single - stage class D electronic ballast by adding capacitor parallel with each power switch and setting the circuit parameter to operate under class DE inverter condition. By using this proposed method the DC bus voltage can be reduced around by 50% compare with conventional class DE inverter circuit. Because the power switches are operated at zero voltage switching condition and low dv/dt of class DE switching, power loss is less and EMI is generated. The experimental results are satisfied with the theoretical derivation. The experimental results show that the proper frequency of the prototype is around 40 kHz with input power factor of 0.988, THD_i 8.5% at full load and efficiency of more than 90%.