1. AN ADAPTIVE OUTPUT CURRENT ESTIMATION CIRCUIT FOR A
PRIMARY-SIDE CONTROLLED LED DRIVER
ABSTRACT:
A primary-side controlled method is commonly used in flyback LED driver to regulate output
current by employing an auxiliary winding. However, owing to intrinsic propagation delay in real-world
circuits, a primary-side controlled flyback converter experiences a worse line regulation. This paper
proposes a smart output current estimation scheme to improve line regulation for constant on-time control,
and it can be compatible with the current flyback topology. A 9.5-W prototype of the proposed flyback LED
driver has been fabricated in Nuvoton Technology Corporation 0.6-μm 5-V/40-V CMOS process. The
maximum switching frequency is set to around 100 kHz with universal-line input, single-stage power factor
correction for LED lighting applications. Experimental results prove that the proposed scheme can improve
the line regulation within 1.5% and the power efficiency can be up to 89.7%.