An improved "charge pump" electronic ballast with low THD and low crest factor

The "charge pump" electronic ballast circuit, which employs a charging capacitor and a high-frequency AC source to implement power factor correction (PFC), has become an attractive topology for ballasting fluorescent lamps. However, the basic "charge pump" electronic ballast circuit has the problems of high total harmonic distortion (THD) of the input current and high crest factor (CF) of the lamp current. This paper analyzes the origin of the problems and proposes a novel solution. With the addition of two small clamping diodes, good input current (PF>0.99, THD<5%) and lamp current (CF<1.6) can be obtained with open-loop control. Experimental results are provided for verification.