A Multiplexing Ripple Cancellation LED Driver With True Single-Stage Power Conversion and Flicker-Free Operation

Abstract

Although a single-stage off-line power light-emitting diode (LED) driver can achieve low cost and high efficiency, the notorious double-line-frequency flicker issue with a single-stage LED driver limits its usage in high-quality lighting applications. To solve lighting flicker, as well as maintain a low cost and high efficiency, a multiplexing ripple cancellation (MRC) LED driver is proposed in this paper. One switching cycle is divided into two intervals. During the first interval, the proposed LED driver operates as a conventional LED driver that transfers energy from the ac input to LED output, performs power factor correction, and generates the main output voltage. The main output voltage has a double-line-frequency ripple like in a conventional design. During the second interval, the proposed LED driver transfers energy from the ac input again to generate an opposite ripple voltage to cancel the ripple voltage from the main output. In this way, the voltage across the LED load is a dc to achieve flicker-free LED driving performance. More than 99% of the output power goes through one-time power conversion, while less than 1% goes through two-time power conversion. A 7.5-W experimental prototype is built and tested to verify the design concept.