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Wednesday, 21 December 2011

A HIGH-POWER-FACTOR SINGLE-STAGE SINGLE SWITCH ELECTRONIC BALLAST FOR COMPACT

A very high power factor electronic ballast that uses a single switch in the power circuit is proposed in this paper for compact fluorescent lamps (CFLs). The reason for the CFL’s increasing popularity is that it conserves energy, and subsequently, reduces energy cost when compared to traditional incandescent lamps. To minimize cost and to ensure that a compact electronic ballast circuit can be installed at the base of a CFL, commercial CFLs normally do not include a power factor correction (PFC) circuit in their electronic ballasts. This paper proposes new high-power-factor single-switch electronic ballast for CFL applications. The proposed power circuit is designed by integrating a SEPIC power factor corrector with a novel single-switch current-fed resonant inverter. The advantage of this single-switch electronic ballast is that it greatly simplifies the gate-drive circuit design due to the elimination of isolation devices that are otherwise required in the conventional half-bridge totem pole configuration. This topology features a reduction of at least two switches in the power stage compared to conventional two-stage approach for high-power-factor electronic ballasts. In addition, the proposed circuit is also able to achieve close-to-unity power factor by operating the integrated SEPIC power factor corrector in discontinuous conduction mode. The conduction loss of the switch in the proposed circuit is also significantly reduced compared to the conventional class-E single-switch resonant inverter. The proposed circuit has both lower peak current and voltage stress across the switch than that of the class-E resonant inverter. Operating principles and characteristics of the proposed circuit are provided in this paper.


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