A Novel Primary-Side Controlled Universal-Input AC–DC LED Driver Based on a Source-Driving Control Scheme

A novel primary-side controlled universal-input ac- dc LED driver based on the source-driving control scheme is proposed in this paper, which employs low-voltage control MOSFET M₂ to drive high-voltage power MOSFET M₁ without an auxiliary winding commonly used in the conventional primary-side controlled scheme. The proposed control IC adopts minimum voltage detection circuit to monitor the zero crossing information of secondary winding current. The demagnetization time signal is generated by demagnetization time detection circuit. In addition, the ratio between the secondary winding demagnetization time T_Demag and switching period T_S is maintained constant by adopting the intelligent charging and discharging circuit, finally achieving highprecision constant output current. A control IC for the proposed LED driver has been fabricated in TSMC 0.35 μm 5 V/600 V CMOS/LDMOS process. Experimental results of a 3-W circuit prototype show that the constant current precision is within ±1% in a wide range of universal-input ac voltage from 85 to 264 V, and that above 80% efficiency is obtained when driving three 1-W LEDs. The start-up time is only 46 ms under 90 Vac and 60 Hzinput, and the standby power is tested to be lower than 142 mW under 220 Vac and 50 Hz-input.