POWER DEVICES
Figure 3: The EPC9165 converter with a EPC9528 dsPIC33CK controller module attached
Figure 4a: Measured converter efficiency at 500kHz, 48V input and 14.3V output
bandwidth is set to 800Hz. Thermal management
For the end-use case of vehicle electrification, the heatsinking capability can be considered infinite since this will ultimately function inside a vehicle with the unit mounted to the chassis. For this design, at full output power of 2kW, a standard commercially available 8th brick heatsink is used here. Four metal spacers are installed on the PCB to provide the appropriate clearance for the heatsink mounting. A thermal interface material (TIM) is required between the FETs and heatsink. Usually, the material needs to have a) mechanical compliance due to compression, b) electrical insulation and c) good thermal conductivity. In this design, a TIM with 17.8W/mK is used.
Design validation results
Figure 3 shows a photo of the EPC9165 converter without the heatsink mounted.
The dimensions are 4.3x2.8x1.6 inches (108x70x40 mm) excluding the edge connectors.
With the heatsink installed and 1700 LFM airflow, the converter was operated at 48V input, 14.3V output and tested at 500kHz. The efficiency
30 DECEMBER/JANUARY 2023 | ELECTRONICS TODAY
Figure 4b: Measured converter efficiency at 500kHz, 14.3V input and 48V output
results in Figure 4a and 4b show that at 500kHz, using a 1µH inductor, the converter achieved a peak efficiency of 97% and the converter was also tested at 14.3V input and 48V output for boost mode operation. At full load, EPC eGaN FETs can operate with 96% efficiency at 500kHz switching frequency, enabling 1kW/phase compared to silicon-based solutions, which are limited to 600W/phase due to the limitation on the inductor current at 100kHz maximum switching frequency. With increasing global legislation aimed at higher fuel efficiency standards, vehicle manufacturers are searching for cost-effective solutions to meet these demands while still providing the power required for ever-increasing electronically driven functions. The design of GaN-based bi-directional high-power converters for mild-hybrid cars and battery power backup units can meet the design priorities for system size, cost, and high reliability. This scalable solution can be used to meet the power requirements of the latest 48V mild hybrid systems, with power ranging from 1.5kW to 6kW.
EPC
www.epc-co.com
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