Three-Phase Interleaved LLC Converter with Capacitive Current Balancing and Reduced Switch Voltage Stress

Interleaved converters are a typical solution to enhance a current capacity and reduce current ripples of input or output ports. Conventional interleaved LLC converters need additional switches and feedback control loop, or some passive components, for active current balancing, increasing the circuit complexity and cost. This paper proposes a novel three-phase interleaved LLC converter with an automatic capacitive current balancing capability. Two flying capacitors contribute to not only the automatic capacitive current balancing but also reduced switch voltage stresses and asymmetric resonant operations to reduce RMS currents. The operation analysis and capacitive current balancing capability are discussed. The experimental verification using a l-kW prototype demonstrated that the automatic capacitive current balancing could be achieved despite the significant mismatch in transformers' parameters.