Wide-Input-Voltage-Range 3 kW DC-DC Converter with Hybrid LLC & Boundary / Discontinuous Mode Control

Abstract

Growing applications such as electric vehicles, data centers, and industrial robotics require power-dense and efficient converters systems to provide high output currents at low output voltages of generally 12 V. Today's converters achieve high efficiencies at a specific input voltage, but drastically lose efficiency once the input voltage deviates from its nominal value. A large voltage swing, however, is a common situation in the aforementioned applications, as the respective input voltages, in worst-case, can easily drop by 50 %, whereby full functionality still needs to be maintained. In this work, we demonstrate a wide-input-voltage-range 400 V to 12 V, 3 kW dc-dc converter with a novel control method and transformer design. The employed boundary/discontinuous mode control scheme reduces circulating currents over conventional LLC techniques, and the "snake-core" matrix transformer achieves ideal parallel-connected secondary voltage balance. The converter achieves 350 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> power density while operating from 300 V to 430 V input voltage and from 10 % to full load. An advanced design for a data center power supply application additionally utilizes the magnetizing inductance for boost operation in order to optimize the operating conditions of the converter system and to increase the overall efficiency. A performance comparison is finally explored for comparing the advanced design with the current hardware demonstrator and with conventional LLC converters.