A CMOS high dimming ratio power-LED driver with a preloading inductor current method

This paper presents a high dimming ratio LED driver for automotive lighting applications which require avoiding EMI radiation. In order to accomplish a high dimming ratio LED driver, the preloading inductor current methodology is proposed for the power stage of the proposed circuit to achieve the fast transient response time during the LED load switching. The proposed circuit receives the input voltage of 12V and generates the output voltage of 30V with the load current of 350mA. The chip is implemented with 0.35um BCDMOS process, and the die area is 2.35 × 2.35 mm². Measurement results illustrate that the proposed LED drive system features the minimum rising time as small as 240ns and the corresponding dimming ratio becomes 2000:1 at the dimming frequency of 1KHz. The maximum power conversion efficiency of the chip is measured to be 94.82%.