An Electrolytic-Capacitor-Less PFC LED Driver With Low DC-Bus Voltage Stress for High Power Streetlighting Applications

Abstract

This paper presents a single-stage, soft-switching, high power factor, flicker-free LED driver without any electrolytic capacitors for streetlighting application. The proposed LED driver consists of a buck-boost type power factor correction (PFC) circuit integrated with an asymmetric half-bridge LLC resonant converter. The buck-boost type PFC circuit provides a high power factor, low input current harmonics, and low dc bus average voltage. Unlike other methods that use the first harmonic approximation (FHA) analysis or the differential equations in time domain to analysis the LLC circuit, in this paper, a Fourier series-based analysis is proposed. The proposed method provides better accuracy in comparison with the FHA while being simpler than the time domain analyze method. The half-bridge LLC resonant converter is designed such that ZVS is obtained for the entire input voltage range (185 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 265 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$V_{rms}$</tex-math></inline-formula> ), and for 20% to 100% of the full-load power. In addition, a magnetic integration technique is utilized to increase efficiency and reduce converter size. The designed control system enables lowering the output current ripples without using any electrolytic capacitors. To verify the feasibility of the proposed LED driver, a 200 W prototype is implemented. The proposed LED driver achieves maximum efficiency of 94.6%, high PF, and a maximum of 15% output current ripples.