High-Frequency High-Power Density Multicell Transformer-Coupled Input-Series-Output-Parallel (ISOP) Double Clamp ZVS Flyback Converter

Double-clamp zero-voltage-switching (DCZVS) full-bridge flyback converter is one of the most attractive solutions for high-power density applications with wide input range, because of its features of primary-side regulation and excellent soft-switching. By analyzing the zero-voltage switching process and the maximum output power at maximum flux, this article reveals that the dead-time is one of the key parameters to restrict the output power of the DCZVS converter at high switching frequency. Then, the multicell transformer-coupled input-series-output-parallel (ISOP) structure is proposed in this article to shorten the dead-time so as to improve the output power of the DCZVS converter, which does not increase the size of the transformer. In the multicell converters, the number of cells and the transformer design are also discussed. Finally, a DCZVS prototype with two transformer-coupled ISOP cells is built up to validate the design, which achieves a wide input range of 160–420 V and realizes a 28 V/20 A output with a power density of 1203 W/inch³ and a peak efficiency of 93.69%. Compared with the original DCZVS converter, the proposed two-cell DCZVS converter achieves a 15% increase in power density with the same transformer size and maximum flux.