Dimmable multi-channel RGB LED driver

Abstract

This paper proposes a dimmable multi-channel Red-Green-Blue (RGB) LED Driver for backlighting and display and applies variable control technique to regulate color mixing. A linear Control DC-DC converter is used to provide the needed constant current for the RGB LEDs. It is designed to provide greater than 25mA constant output current with high accuracy. A PWM control method is used, of which the variable external voltage determines the available brightness levels and has a dimming frequency of 2 kHz. The proposed LED driver system is also able to dim each individual LED color through the dimming controller circuit; for each of the 3 channel per color around 90%, 93% 93% efficiencies for the red, green and blue channels respectively. A digital port was provided for the option of Digital dimming using a microcontroller. A linear current regulator is presented and this can be extended and applied to multiple strings. The temperature coefficient for the red channel is 75.43 ppm/°C and 89.46 ppm/°C for both green and blue channel. This was designed and simulated using 0.35micron TSMC 2P4M 5V technology and the chip area is 2.31×1.48 (mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ).