A single‐stage bridgeless LLC resonant converter with constant frequency control based LED driver

Abstract

In this article, a single‐stage bridgeless LLC resonant converter with a constant frequency control method is proposed for a high‐brightness light‐emitting diode (LED) driver. LED strings require drivers with high power density and high efficiency. This article presents a novel LED driver circuit topology based on switch integration and the switching controlled capacitor (SCC) technique. By combining the merits of a totem‐pole bridgeless boost PFC unit and a high frequency SCC‐LLC half‐bridge resonant converter, the proposed topology can achieve high efficiency. Due to the SCC‐LLC circuit topology structure, constant frequency control of the LLC resonant converter is achieved by the regulation of the equivalent resonant capacitance. The proposed novel LED driver topology can automatically achieve soft‐switching characteristics and a high power factor. The operating principle of different operation modes and the characteristics of the proposed LED driver are analysed in detail. Finally, to demonstrate the feature of the proposed topology, a 100 W/70 V laboratory prototype is built. The satisfactory experimental results correspond with the theoretical analysis and parameter design.

Application-Oriented Review of the LLC-Based Resonant Converters

“…These algorithms can dynamically adjust the operation of the converters based on load and input voltage conditions. A bridgeless converter for LED driver applications was proposed in [ 169 ] , by combining an interleaved bridgeless boost Power Factor Correction (PFC) rectifier with an LLC resonant converter. This configuration uses an additional capacitor and a series switch in the resonant tank, which complicate the circuit, increase its cost and power loss.…”