Digital Architecture for Driving Large LED Arrays with Dynamic Bus Voltage Regulation and Phase Shifted PWM

This paper introduces a digital architecture suitable for driving a large number of High Brightness Light Emitting Diodes (HB-LEDs) with improved system efficiency and reduced EMI. Key advantages are achieved by combining and coordinating control of the power converter and LED strings, resulting in a system with deterministic load behavior. Uniform phase shifting of LED strings is performed to minimize load current variations, resulting in reduced output capacitance, improved converter efficiency and reduced system EMI. LED string voltages are detected online and used in a feedforward path for dynamic bus voltage scaling, resulting in improved system efficiency at low dimming levels. Experimental results are presented for a 15 W boost converter with FPGA based digital control driving a 64 LED array with 8 LED strings.