Circulating Current Suppression of Current-Fed Push Pull DC-DC Converter with Natural Commutation Strategy

In low-voltage high-current applications, the current-fed push-pull (CFPP) converter stands as one of the promising topological candidates. However, voltage spikes will occur when input inductor current and leakage inductor current become mismatched. Natural commutation techniques have attracted significant attention due to their ability to mitigate voltage spikes without requiring additional clamping circuits. Nevertheless, existing natural commutation strategies still exhibit limitations in terms of excessive current stress and substantial circulating current. To address these challenges, this paper proposes a circulating current suppression (CCS) modulation strategy. The fundamental principle involves strictly controlling both duty cycle and phase shift angle of the CFPP converter to minimize current mismatch duration, thereby significantly reducing current stress and circulating current. Firstly, this paper elaborates on the operational principles of the proposed CCS strategy and derives mathematical expressions for its transmission power, current stress, circulating power and loss model. Furthermore, to highlight the advantages of proposed CCS strategy, mathematical models for current stress and circulating power in existing natural commutation strategies are systematically established, followed by comprehensive comparative analysis and simulation validation. Finally, a 500W CFPP prototype is constructed for experimental validation. Experimental results demonstrate that compared with state-ofthe-art strategies, the proposed CCS strategy achieves at least a 35.21% reduction in current stress and at least a 67.26% reduction in circulating power. On the other hand, it also shows advantages in terms of cost and compactness.