22 POWER CONVERSION www.epc-co.com Issue 2 2023 Power Electronics Europe www.power-mag.com is attached to the flat mounting face of the heat-spreader. A two-part gap filler TIM (Bergquist GF4000) is used for the thinnest bond line thickness, and to provide some adhesion between the heatsink and heat-spreader. With this cooling method, figure 7 shows temperature measurements taken from the top side of the PCB with IR camera and only a 30°C temperature rise is recorded. The air flow used is around 1500 - 2000 LFM. Conclusion This article presented the design of a 3 kW capable 2-phase (1.5 kW single phase) DC-to-DC converter reference design using eGaN FETs, EPC2215. A 3-level topology is used which allows for 2x reduction in voltage stresses in the switches. In the experiment, 97.8% peak efficiency is achieved at 200 V input and 40 V output. The temperature rise of the FET is around 30°Cwith top side cooling using a heatspreader and heatsink. References [1] A. Lidow, M. De Rooij, J. Strydom, D. Reusch, and J. Glaser, GaN Transistors for Efficient Power Conversion, 3rd ed. John Wiley & Sons, 2019. ISBN: 978-1119594147. [2] T. A. Meynard and H. Foch, “Multi-level conversion: high voltage choppers and voltage-source inverters”, PESC ’92 Record. 23rd Annual IEEE Power Electronics Specialists Conference, vol. 1, pp. 397-403, June 1992. [3] B. P. McGrath and D. G. Holmes, “Analytical modelling of voltage balance dynamics for a flying capacitor multilevel converter”, IEEE Transactions on Power Electronics, vol. 23, no. 2, pp. 543-550, March 2008. [4] EPC2215 – Enhancement Mode Power Transistor - EPC-co.com (no date). Available at: https://epcco.com/epc/Portals/0/epc/documents/ datasheets/EPC2215_datasheet.pdf (Accessed: November 29, 2022). [5] NCP51820 - high speed halfbridge driver for Gan Power Switches - Onsemi (no date). Available at: https://www.onsemi.com/pdf/datashee t/ncp51820-d.pdf (Accessed: November 29, 2022). [6] How2AppNote012, Thermal Management of eGaN® FETs- EPCco.com. Available at https://epcco.com/epc/Portals/0/epc/documents/ applicationnotes/How2AppNote012%20- %20How%20to%20Get%20More%20P ower%20Out%20of%20an%20eGaN% 20Converter.pdf Figure. 5: Typical switch node waveforms showing several switching cycles when the board is operating from 200 V input and delivering 24 A into a 40 V load. Figure. 6: Measured efficiency (left axis) and power losses (right axis) with VOUT = 40 V and VIN = 200 V Figure.7: Thermal image taken from the top side of the PCB when operating from 200V input and delivering 24 A into 40 V load in an ambient of 20°C
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