Inherent volt-second balancing of magnetic devices in zero-voltage switched power converters

D. Costinett
D. Seltzer
Zane Regan
D. Maksimovic

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Small mismatches in inductor-applied volt-seconds may arise in power converters due to asymmetries in circuit parasitics or modulation waveforms. These small mismatches can have significant impact on circuit operation, including the saturation of magnetic components, loss of regulation, and decrease in converter efficiency. Various auxiliary circuits and control methods have been developed to prevent volt-second imbalances from being applied to magnetic components. In this work, an inherent feedback specific to Zero-Voltage Switched (ZVS) converters is examined which automatically compensates for volt-second mismatch. A closed-form linearized relation between volt-second mismatch and inductor current offset is derived. This relation is then verified through simulation and experimental results using two prototype circuits comprised on an inductively loaded full-bridge and a dual active bridge (DAB) converter.