Self-adjustable feed-forward control and auto-tracking off-time control techniques for 95% accuracy and 95% efficiency AC-DC non-isolated LED driver

The non-isolated buck topology for LED driver is proposed to reduce volume and cost without the need of large transformer. Besides, in the entire universal range of AC input voltage, the proposed self-adjusted feed-forward control (SAFFC) technique ensures small variation in the LED current. The auto-tracking off-time control (ATOTC) technique is also adopted to adjust the off time to guarantee the current accuracy is better than that of the peak current control (PCC) technique while and the efficiency is better than that of the hysteresis current control (HCC) technique. Test chip fabricated in VIS 0.5μm 700V ultra-high voltage (UHV) process demonstrates power factor higher than 0.97, averaged 95% high accuracy, and 95% high efficiency.