A new current source charge pump electronic ballast having high input power factor and low crest factor

The basic current source charge pump power factor correction electronic ballast as proposed in [J. Qian et al., July 1998] has the problem of high lamp current crest factor. Switching frequency modulation has been proposed [J. Qian et al., July 1998] to improve lamp current crest factor. But, the requirement of wide variation of switching frequency makes the design of the ballast complicated. Moreover, in this case the lamp current has to be sensed which increases the hardware requirement and makes the control issue more involved. Here an attempt has been made to improve the lamp current crest factor without modulation the switching frequency. This is achieved by transferring the excess energy of the resonant inductor to the dc bus at the zero crossing instants of the input voltage by employing a high frequency transformer. As the transformer is required to operate at high frequency while having low volt-ampere rating, increment in passive element count is insignificant. The operating principle of the proposed scheme is presented and analysed. The working of the scheme is verified through extensive simulation studies. A laboratory prototype of the ballast is fabricated and the viability of the proposed scheme is conformed through experimental studies.