High-Performance Megahertz-Frequency Resonant DC–DC Converter for Automotive LED Driver Applications

This paper introduces a megahertz-frequency resonant dc–dc converter that inherently achieves a load-independent output current while maintaining high efficiency across a wide output voltage range. These properties make the proposed converter well-suited for automotive light-emitting diode (LED) driver applications, where a varying number of LEDs need to be driven with a constant current. The proposed converter achieves load-independent output current by utilizing an <italic>LCL</italic>-T resonant network, and achieves high efficiency using a comprehensive design optimization methodology. This <italic>LCL</italic>-T resonant converter is also capable of regulating its output current at any desired value by utilizing phase-shift control. The performance of the <italic>LCL</italic>-T resonant converter is theoretically and experimentally compared with an <italic>LC</italic>³<italic>L</italic> and an <italic>LCLC</italic> resonant converter. For the experimental comparison, prototypes <italic>LCL</italic>-T, <italic>LC</italic>³<italic>L</italic>, and <italic>LCLC</italic> resonant converters are designed to operate at 2 MHz and across an output voltage range of 3.3–49.5 V while supplying a constant 0.5 A output current to the LEDs. The <italic>LCL</italic>-T resonant converter prototype achieves a peak efficiency of 91.1%, which is 0.6% and 1.8% higher than the peak efficiency of the <italic>LC</italic>³<italic>L</italic> and the <italic>LCLC</italic> converter prototypes, respectively. Furthermore, the <italic>LCL</italic>-T converter prototype maintains 0.8% and 1.6% higher average efficiency over its 15:1 output voltage range relative to the <italic>LC</italic>³<italic>L</italic> and the <italic>LCLC</italic> converter prototypes, respectively.