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 LCL-T resonant network, and achieves high efficiency using a comprehensive design optimization methodology. This LCL-T resonant converter is also capable of regulating its output current at any desired value by utilizing phase-shift control. The performance of the LCL-T resonant converter is theoretically and experimentally compared with an LC
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L and an LCLC resonant converter. For the experimental comparison, prototypes LCL-T, LC
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L, and LCLC 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 LCL-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 LC
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L and the LCLC converter prototypes, respectively. Furthermore, the LCL-T converter prototype maintains 0.8% and 1.6% higher average efficiency over its 15:1 output voltage range relative to the LC
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L and the LCLC converter prototypes, respectively.