A Voltage-Competing Flyback-Based Balancer Combined with Auxiliary Power Supplier

Traditional half-bridge converters often suffer from the neutral point voltage fluctuation which may result in unequal voltage stress on switching devices, common mode interference, and poor power quality. Therefore, a voltage-competing flyback-based balancer is proposed, and it simultaneously serves as the auxiliary power supplier and the neutral point voltage balancer with the limited power devices. Since the excessive power of the capacitor with the higher voltage is stored and transferred to the other one through the same primary winding, additional power loss caused by the leakage inductor is avoided. Meanwhile, the output voltage of the secondary winding has a close relation with the lower voltage of the DC-link capacitor, which can be utilized to monitor the capacitor voltage difference without paying the price for the isolated sampling of the DC-side voltage. Compared to the traditional switching balancing methods or the auxiliary-circuit-based balancing methods, the proposed balancer not only alleviates the control burden but also reduces the hardware complexity. The experiments are finally conducted on a balancer with 24V auxiliary power output to verify the effectiveness of the proposed balancer in equalizing the capacitor voltages of the half-bridge-type converters.