May 2020

22 POWER GaN www.epc-co.com Issue 2 2020 Power Electronics Europe www.power-mag.com one used in the eScooter shown in Figure 1. It can operate from 20 kHz through 1 MHz switching frequency and deliver a peak current of 15 A into each phase of the motor when a heatsink is attached. The board measures just 45 mm x 55 mm. To demonstrate the achievable performance of this BLDC drive, the inverter was operated from a 48 V DC supply voltage while switching at 100 kHz to power a 400 W motor with a sinusoidal modulation frequency of 20 Hz (rotational speed of the motor). The dead times for the half bridges were set to 10 ns for both the rising and falling edges and are very short when compared to MOSFETs that start at 50 ns. Figure 6 shows the measured waveforms on a motor modulation frequency time scale. The drive is operated in an open loop and thus there is no controller to compensate for operation- induced distortions. The measured power loss as a function of one-phase RMS motor current for this drive is expected to exceed 98.4 % in real world conditions. Conclusion GaN FETs have demonstrated high switching frequency capability in BLDC motor drives, and the advent of a monolithically integrated half-bridge FET with full-function gate driver was demonstrated by powering a 400 W capable BLDC motor. The monolithic integration of the FETs and the gate driver ensures low switching losses and enables high switching frequency for the drive. Higher switching frequencies for the drive, together with simple EMI filtering reduces motor loss, keeps audible emissions low even at high speed, and saved significant weight and space. The result is a compact drive solution that could easily be integrated inside the motor housing for further cost, size, and weight savings. GaN-on-Si devices, such as the ePower Stage EPC2152, are a major step toward developing full power systems-on-a-chip. Over the next few years there will be many more such products introduced to the market, each one reducing design time while improving system efficiency and cost. The era of the discrete transistor is coming to a close. Literature [1] A. Lidow, M. de Rooij, J. Strydom, D. Reusch, J. Glaser, GaN Transistors for Efficient Power Conversion. Third Edition, Wiley, ISBN 978-1-119-59414-7. [2] “EPC2152 – 80 V, 10 A Integrated ePowerTM Stage,” Efficient Power Conversion Preliminary Datasheet, Jan. 2020. Figure 4: PCB (top and bottom side) of the 3-phase experimental BLDC motor drive (expl: a top, b bottom side) Figure 6: Motor modulation frequency (20 Hz) timescale measured switch-node and phase-current waveforms of the drive when operating from a 48 V DC supply and delivering 10 ARMS per phase into the motor Figure 5: Zoomed-in photograph of the EPC2152 ePower Stage with support components as designed in the inverter PCB