Contactless DC Connector Based on GaN LLC Converter for Next-Generation Data Centers

Abstract

An inductively coupled contactless dc connector has been proposed for the next-generation 380-V dc distribution system in data centers. A LLC resonant dc-dc converter topology with gallium nitride (GaN) power transistors has been applied to realize the short-distance highly efficient contactless power transfer. A prototype of a 1.2-kW 384-to 192-V connector has been fabricated and the conversion efficiency of over 95% with the power density of 8.1 W/cm 3 has been confirmed experimentally under 1000-kHz operation. The design consideration has been carried out and the potential to achieve 10.0 W/cm 3 has been also shown taking the feature of the GaN power device and the characteristics of the magnetic core material for the transformer into account. The contactless dc connector integrates the functioning of an isolated dc-dc converter into a connector for space saving, and the dc current can be cut off without arc because of the inductive coupling. The proposed connector contributes to realizing a highly efficient, space saving, and reliable future 380-V dc distribution system. Index Terms-Contactless power supply, dc power distribution, dc-dc power converters, gallium nitride (GaN).0093-9994 , he has been with Osaka University.He is engaged in research and development of power converter control in distribution systems and the design methodology for high power density converter using SiC and GaN power devices. Currently, he is mainly engaged in the development of high power density dc power supplies for 380-V dc distribution systems. His research concerns dc power connectors using LLC resonant circuits.Toshifumi Ise was born in 1957. He received the B.Eng., M. Eng., and Doctor of Engineering degrees in electrical engineering

Optimal design of high frequency high efficiency and high‐power density DC–DC power module based on GaN

“…The coupling coefficient of the coupling inductance is: $$$$\begin{equation}k = \frac{M}{L} = - \frac{{(N_1^2 + N_2^2){R}_{g2} + 2{N}_1{N}_2({R}_{g1} + {R}_{g2})}}{{(N_1^2 + N_2^2){R}_{g1} + {{({N}_1 + {N}_2)}}^2{R}_{g2}}}\end{equation}$$$$according to the target inductance L and coupling coefficient k , the reluctance R g 1 and R g 2 can be deduced: u 0 is available through the core material, l g is the core air gap [7–11]. $$$$\begin{equation}\left\{ { \def\eqcellsep{&}\begin{array}{@{}*{1}{c}@{}} {{R}_{g1} = \frac{{{l}_g}}{{{A}_{e1}*{u}_0}}}\\[12pt] {{R}_{g2} = \frac{{{l}_g}}{{{A}_{e3}*{u}_0}}} \end{array} } \right.\end{equation}$$$$…”

“…The LLC planar transformer primary and secondary winding turns ratio is consistent, in PCB design, can ensure that the primary winding and secondary winding DC resistance is the same, LLC transformer winding DC resistance can be derived [2–9]: $$$$\begin{equation}{R}_{dc} = \frac{{2\pi \rho }}{h}*\frac{1}{{\ln (r + c) - \ln (r)}}\end{equation}$$$$…”

“…With the emergence of new gallium nitride (highelectron-mobility transistor) switching devices in recent years, this bottleneck has turned around. Compared with traditional silicon devices, gallium nitride switching devices have smaller switching loss and conduction resistance [4][5][6][7][8], working frequency can increased to MHz, and relative silicon devices can effectively reduce the on-off loss, conduction loss and turn-off loss. The efficiency and power density of the power module cannot effectively improved only by optimizing the switching devices of powers main circuit, which need to be further combined with power module's planar core design, the main power switching services working at zero voltage switching (ZVS) and zero current switching (ZCS) technology [8][9][10][11], reduce the opening loss and conduction loss of switching devices, enhance the utilization rate of magnetic core of planar transformer, and optimization design of the circuit topology together.…”

“…The efficiency and power density of the power module cannot effectively improved only by optimizing the switching devices of powers main circuit, which need to be further combined with power module's planar core design, the main power switching services working at zero voltage switching (ZVS) and zero current switching (ZCS) technology [8][9][10][11], reduce the opening loss and conduction loss of switching devices, enhance the utilization rate of magnetic core of planar transformer, and optimization design of the circuit topology together. To further improve the efficiency and density of the existing power module, break the technical bottleneck that hinder the stagnant development of power modules [7][8][9][10][11][12].…”

Contactless DC connector based on ISOP-IPOS topology for high power density 380 V DC power feeding system

“…The switching loss energy is smaller than Si power devices and the turn-off energy is independent of the drain current [12]- [14]. In LLC converter topology, the turn-on energy can be eliminated by ZVS and the turn-off energy has to be minimized taking the turn-off time for ZVS into account.…”