Electronic-Embedded Transformer Based DC Transformer With Trapezoidal Current and Natural Current Sharing

By incorporating an integrated low-voltage full bridge Cao et al., the concept of an electronic-embedded transformer (EET) offers a straightforward means of achieving high-frequency, high-power fixed-gain isolated dc–dc conversion, known as a dc transformer (DCX), through parallel operation of EET units with natural current sharing. However, EET-DCX, characterized by triangular transformer current, exhibits a higher root mean square (rms) value compared to the sinusoidal current in LLC/CLLC-DCX. To address this limitation, this research letter proposes a trapezoidal current modulation technique for EET-DCX. Through the implementation of trapezoidal current modulation, EET-DCX can effectively reduce the rms current by 15% and 11% when compared to triangular current EET-DCX and sinusoidal current CLLC-DCX, respectively. Consequently, this modulation scheme contributes to a noteworthy reduction of total conduction loss, encompassing both device and transformer winding losses, by 28% and 23%. Notably, the proposed trapezoidal current modulation retains all the advantages of previous EET-DCX designs, including natural current sharing, optimal operation at any frequency, load-independent voltage gain, simple open-loop control, and full-load-range zero-voltage switching (ZVS). This letter provides an in-depth analysis of the proposed modulation technique, supported by verification on a 12-kW prototype featuring four parallel transformers. To enhance understanding, two accompanying videos have been prepared to illustrate the current sharing behavior and frequency variation within the EET-DCX system. These visualizations provide valuable insights into the practical implementation and performance of the proposed trapezoidal current modulation approach.