An LED Lamp Driver Compatible With Low- and High-Frequency Sources

Abstract

An LED lamp driver with its input compatible with high- and low-frequency sources is proposed. It can be powered by the ac mains, low-frequency electromagnetic ballast, or high-frequency electronic ballast. Its input impedance is controlled to meet the operational requirements and conditions of different sources and its output is controlled to deliver the required power to the LED array. When the driver is powered by a low-frequency source, like ac mains or low-frequency electromagnetic ballast, it is configured as an active power factor corrector. Its input current follows the wave shape of the source voltage. When the driver is powered by a high-frequency source, like electronic ballast, it is configured as a phase-shifted resonant converter with controllable input resistance and susceptance. Moreover, the driver has a startup mechanism that emulates the ignition process of a fluorescent lamp. Such a wide source compatibility of the driver enables the lamp be applied in new lighting installations or retrofitting fluorescent lamps with LED lamps without modification of existing ballasts and/or lighting infrastructure. A 20-W prototype, which is designed to retrofit a 36-W T8 fluorescent lamp, has been built and evaluated with different sources, including ac mains (110 V/60 Hz, 220 V/50 Hz), electromagnetic ballast, and electronic ballast.