A single-stage primary side controlled flyback LED driver.

In applications for indoor illumination, light-emitting diode (LED) is widely used. The requirements for small volume, low cost and high reliability LED driver makes additional challenges. Conventional single stage flyback LED driver requires additional feedback components such as opto-coupler or auxiliary winding. These components take space on printed circuit board, reduce the reliability and may introduce interference into the feedback loop. A 2.7 W LED driver without opto-coupler or auxiliary winding is proposed. With novel demagnetizing time sampling method, the feedback circuit is fully integrated into the controller, leaving few off-chip components. The controller integrated circuit (IC) is fabricated in CSMC 0.8 μm 500 V BCD process to verify the proposed sampling method. A power MOS is also integrated into the controller IC to simplify the off-chip circuit further. A prototype of the driver is also built and optimized to reduce the volume into 1.6 × 2.4 × 1.4 cm. The experimental results show that the efficiency is above 72.75 % and the average output current variation is less than 5 % under universal input voltage. [ABSTRACT FROM AUTHOR]