Transformer Coupled Recycle Snubber for High-Efficiency Offline Isolated LED Driver With On-Chip Primary-Side Power Regulation

This paper presents a high-efficiency offline isolated LED driver based on a flyback converter. In order to achieve high power conversion efficiency as well as a low-cost design, a simple passive lossless turn-off snubber is proposed to reduce the switching loss of the power switch. A primary-side power regulation scheme is also proposed to compensate for forward voltage variation and aging caused by process and temperature variations. The proposed control scheme is designed and fabricated on-chip using a 0.35-mu m BCDMOS process. Test results of the proposed LED driver show an efficiency level that exceeds 83% (up to 90%) in an output range of 5-10W with an input range of 85-265 V-AC