A Composite Converter based Automotive LED Driver

The paper presents a composite converter-based LED driver fed by an automotive battery and capable of delivering a constant current to an LED string. A two-stage architecture is proposed consisting of a composite boost converter in the first stage, cascaded with a buck converter in the second stage, which acts as a constant current source for the LED string. The composite boost converter consists of a capacitively coupled transformerless dual active bridge (CC-DAB) module and a partial-power boost converter module connected in an input-parallel output-series (IPOS) configuration. It is capable of processing indirect power efficiently, thereby reducing the device voltage and current stresses, resulting in higher overall efficiency compared to a conventional boost+buck automotive LED driver architecture. Furthermore, the CC-DAB module uses series capacitors to couple the inverting and rectifying bridges and eliminates the need for an isolation transformer, further improving efficiency and power density compared to a conventional transformer-based design. The composite converterbased LED driver is able to operate over wide input (8V to 18 V) and output voltages (3V to 50 V) driving a string of 1 to 15 LEDs. The experimental results show a maximum efficiency of 94.7% and significant efficiency improvements over the reference boost + buck architecture over the entire operating range.