A PFM-controlled LED Driver To Achieve Consistent Illuminance

This investigation demonstrates a LED driver with PFM control to generate consistent illuminance, where Illumination Equalizer circuit, PFM Control Circuit, Voltage Limiter, Zero Current Detector, Level Shifter, Clock Generator, and Delay Cell are included. Fabricated using $0.5 \mu \mathrm{m}$ HV CMOS process, the prototype occupies a chip area of 3.2 mm2. The proposed LED driver is also featured with a novel illuminance equalizer, which is able to achieve the accuracy as high as 99% under 20 mA LED output current, and the efficiency is as high as 93% by all-PVT-corner post-layout simulations.