A Single-Stage LED Driver Using Step-Down Cuk/LLC with APWM-PFM Hybird Control

At present, the most of LED driver on the market is designed for worldwide line (90Vac ~ 265Vac) applications, and can not meet the higher voltage input applications. Therefore, step-down Cuk PFC is proposed to be used in higher voltage input applications (277-480Vrms) in the paper. A half-bridge LLC was used as a DC-DC isolation unit of the single-stage converter and adopts an APWM-PFM hybrid control strategy to solve the problem that the conventional pulse frequency modulation (PFM) control strategy leads to unsatisfactory input characteristics of the single-stage circuit and keep the LLC circuit's soft switching characteristics. Therefore, the single-stage resonant converter proposed in this paper possess the advantages such as low input and output current ripple, low stress of the power switch and high system efficiency etc. A 100W experimental prototype was built in the laboratory, which verifies the feasibility of the proposed scheme. Within the entire input voltage range, the zero-voltage switch-on of the switch and the zero-current switch-off of the secondary diode was obtained and the system efficiency achieves up to 91.65% @ the 310Vrms input voltage and rated load.