Digital estimating and balancing of transformer magnetizing current in an isolated full bridge converter

This paper presents a method for estimating and balancing transformer magnetizing current in an isolated full bridge converter. In isolated full bridge converters it is important to avoid transformer saturation which can lead to severe strain on the power transistors or lower converter efficiency. The method presented is based on a digital transformer magnetizing current estimator, which is updated once in each phase of the switching period by only using the transformer primary current. The estimating method works in both steady state and transient converter operating conditions. Based on the estimated transformer magnetizing current the dc-bias magnetizing current can be estimated, controlled and balanced. Furthermore, the experimental results verifies the theoretical analysis in this paper.