A dual mode dimming white LED driver based on Buck DC-DC converter

In order to get high efficiency of LED drive circuit, a novel dual mode dimming LED driver based on buck DC-DC converter is presented in this paper. The peak current control mode with a slope compensation circuit is used in the buck DC-DC converter, which can drive more than 10 350mA LEDs in series with input voltage from 5V to 40V. In the chip a variety protection circuits like under-voltage, over-voltage and over-current protection are integrated. The chip's highest efficiency is over 90%. The driver can automatically switch between PWM and PFM modes according to the dimming input signals. In this way, the driver can achieve a high efficiency over a wide range of varied dimming and avoid color shift. The circuit is simulated with CSMC 0.5μm mixed signal models, and the results show that it possesses a 350mA output current with the duty ratio changed from 0% to 100% to achieve constant luminance control.