Dimmable electronic ballasts by variable power density modulation technique

Abstract

Dimming can be accomplished commonly by switching frequency and pulse density modulation techniques and a variable inductor. In this study, a variable power density modulation (VPDM) control technique is proposed for dimming applications. A fluorescent lamp is operated in several states to meet the desired lamp power in a modulation period. The proposed technique has the same advantages of magnetic dimming topologies have. In addition, a unique and flexible control technique can be achieved. A prototype dimmable electronic ballast is built and experiments related to it have been conducted. As a result, a 36WT8 fluorescent lamp can be driven for a desired lamp power from several alternatives without modulating the switching frequency. IntroductionHigh-frequency electronic ballasts are commonly used due to several advantages over magnetic ones. Electronic ballasts offer increased energy efficacy, better controllability and no humming problem. In order to provide energy savings and to meet the desired luminaries in a space, electronic ballasts can be designed with dimming functions.Dimming can be achieved by varying the DC bus voltage, duty ratio and switching