A 16.5 W Single-Inductor 4-Channel Multi-Color Output DC-DC Buck LED Driver with Digital Control and 96 % Efficiency

This paper introduces a 16.5 W single-inductor 4-channel multi-color DC-DC LED driver, based on a Buck architecture omitting any output capacitance. With an inductance of 68µH the switching frequency reaches 1 MHz in CCM. The LED driver operates in DCM for light loads with an adaptive on-pulse generation to guarantee 8.5 bit color resolution for dimming ratios down to 0.25 %. The peak efficiency measures 96 % and stays above 92 % for 1 A LED current, in which a power density of 2.62 W /mm2 is reached. The fully integrated current sense circuit utilizes the RDson of the color selection transistors to reduce the losses and the parts count to a minimum. A 9 bit differential SAR ADC digitizes the LED current, which is regulated by a digital control loop. The circuit has been fabricated in a 0.18 µm 50V HV CMOS process.