A Hybrid LED Driver With Improved Efficiency

A high-efficient hybrid light-emitting diode (LED) driver is introduced in this article. By combining the merits of conventional switching-converter- based and inductor-less driving solutions, the proposed topology fully utilizes the input power from the ac mains without causing considerable switching loss or excessive voltage stress. With the help of a small-size inductor and the hybrid scheme, the proposed driver automatically alternates between switching mode and linear mode as the rectified input voltage changes. In addition, the driver can be configured either in a single stage for a high power factor (PF) and high efficiency or in the second stage of a two-stage solution for alleviating harmful low-frequency flicker. The proposed driver-integrated circuit is implemented in a 0.35-mu m high-voltage CMOS process and tested under 110-V-AC 60-Hz input. Measurement results show that, when operating in the high PF configuration, the proposed driver achieves 95.1% power efficiency and 0.986 PF. For the low flicker configuration, it achieves 92% efficiency and 15% flicker while maintaining a 0.918 PF.