Design and Implementation of a 12 kW Scalable Electronic-Embedded Transformer (EET)-based DC Transformer (DCX) with Trapezoidal Current

The rapid advancements in energy storage systems, data center power supply, and transportation electrification have created a demand for high-power and high-density isolated DC-DC converters. However, designing a high-power and high-frequency transformer poses significant challenges due to the need to balance thermal management, minimize leakage inductance, maintain compactness, and ensure proper insulation. To overcome these challenges and expand the limits of power and frequency, the concept of the scalable electronic-embedded transformer (EET) was proposed in [1]. The EET design offers simple open-loop control and natural current sharing, enabling easy parallel connection and scalability to different power ratings. Based on this concept, we introduce the EET-based DC transformer (EET-DCX) to address transformer-level paralleling issues and the resonant point shift problem encountered in traditional LLC-DCX configurations. By employing an embedded full bridge, the EET-DCX effectively cancels the impedance of the leakage inductance, enabling optimal performance at any frequency.This paper first introduces a trapezoidal current modulation technique to address the higher root mean square (rms) value exhibited by the EET-DCX characterized by triangular transformer current. By implementing this modulation, EET-DCX achieves a significant reduction in rms current, leading to notable improvements in total conduction loss, including device and transformer winding losses. In addition, the proposed modulation scheme retains all the advantages of previous EET-DCX designs, such as natural current sharing, optimal, load-independent voltage gain, simple open-loop control, and full load range zero voltage switching (ZVS). Finally, this paper gives the hardware design of a 300 V to 300 V 12-kW EET-DCX. All the analysis has been verified by this 12 kW prototype with four parallel transformers.