99%, 15W/cm³ Capacitively Coupled Modular DCPET for Low-Voltage DC Power Supply Systems

A capacitively coupled modular DC-DC power electronic transformer (DCPET) has been proposed. The proposed DCPET consists of capacitively coupled unregulated LLC resonant converter modules; these modules are connected in series-parallel combinations. The capacitive coupling topology is considered to be promising to develop highly efficient high-power-density converter modules, and the series-parallel connection of these modules smoothly achieves various voltage ratios of DCPETs. A trial design for a 48 V-48 V, 450 W capacitively coupled LLC converter module using GaN-FETs has been demonstrated, and the potential to achieve 99%, 15 W/cm3 has been confirmed. Moreover, the 48 V-384 V DCPET using eight 98.8%, 15 W/cm3 converter modules has been demonstrated, and the feasibility of the proposed topology has been verified. The proposed DCPET overcomes the stagnant relationship between the efficiency and the output power density of isolated converters, and the proposed topology contributes to the prevalence of power electronics equipment for the economical use of electric power.