A DC-Link Capacitor Voltage Balancer Integrated into LLC-based Auxiliary Power Supply

Capacitor voltage balancing circuits are required for applications using series capacitor to provide high dc-link voltage. This paper propose a new dc-link capacitor voltage balancer integrated into the LLC auxiliary power supply. Only small balancing inductors are added which are connected between the middle points of adjacent capacitors and half-bridge legs in the LLC auxiliary converter. Taking advantages of the 50 % duty cycle operation, the capacitor voltage can be automatically balanced without extra control, thus reducing the system complexity and cost and improving the overall system efficiency.