Automotive LED Driver based on Resonant DC-DC Converter with Wide Input and Output Voltage Ranges

This paper presents an immitance-network based resonant dc-dc converter capable of operating efficiently over wide input and output voltage ranges. The resonant network results in current-source property on the output side, together with zero-voltage switching and near zero-current switching of switching devices. On the inverter side, a pair of phase-shifted half bridges enables output current control with reduced circulating currents over wide input voltage range. These features are well suited for automotive LED drivers supplied from a battery with wide input voltage range, and regulating output current through a string of LEDs, where the number of LEDs may vary. Experimental results are shown for a 2 MHz converter prototype operating from an input voltage from 8 V to 18 V, and delivering 0.5 A output current to a string of 1-15 LEDs, which corresponds to an output voltage range of 3-to-50 V.