A Low Power LED Driver with a Soft-Switched Buck Converter and a Parallel-Loaded Series L-C Resonant Inverter

摘要

This paper proposes an efficient design of a low power light emitting diode (LED) driver offering a soft-switched buck converter and a parallel-loaded high frequency series L-C resonant inverter. The presented system comprises a rectifier-fed-buck derived power factor controller (PFC) unit which reduces the harmonic distortion of the mains (230V r.m.s.) line current by improving the sending-end power factor. At the receiving-end, there is a high frequency transformer provided isolation and a rectifier to feed appropriate voltage and current to the load. The design incorporates a feedback loop to control the switching operation of the buck converter by varying the duty ratio. The soft-switching application yields to reduced internal electromagnetic interference (EMI) noise. The inverter is operated by two alternating 20kUz pulse width modulation (PWM) signals. The framework has been simulated on PLECS software. The total harmonic distortion (THD) of the mains line current is approximately 10.7904% at 0.9893 sending-end power factor with 12w output power. State space averaging models of the converter circuits have been derived in this paper.