Current Balancing of Paralleled Switches in Resonant Converters with Multiphase Coupled Inductor

Paralleling power devices is a commonly used technique to implement high-capacity power converters. However, device mismatches and uneven circuit parasitics may cause current imbalance among devices, diminishing the benefits of paralleling. This paper investigates the current balancing mechanism of multiphase coupled inductors in resonant converters against a variety of circuit asymmetries and disturbances. The current balancing mechanism of coupled inductors for multiple parallel switches is explained in theory. A 1 MHz, 250 W resonant dc-dc converter with four GaN switches in parallel was built to test the effectiveness of a coupled inductor for current balancing. Simulation and experimental results show that paralleling multiple switching devices with a multiphase coupled inductor can greatly mitigate the impact of uneven circuit parasitics and gate signal mismatches and ensure current sharing, with negligible impact on the overall system behavior, including the dc-dc system efficiency.