Efficient Motor Drive Performance at Low Cost for e-bikes, Drones, and Robotics with GaN FETs
Mar 04, 2022
Mobility is a driving factor in all economies. Electro mobility (or e-Mobility) is a clean and impactful way of keeping the gears of commerce grinding without contributing to the environmental stresses of inefficient motors or fossil fuel burning engines that cause damage to our planet. There is an ever-increasing demand for highly efficient and compact motor drive designs. EPC’s GaN-based motor drive reference designs for eMobility applications are in development to jump-start the competitive and environmentally friendly alternatives that support this trend.
The EPC9167 and EPC9167HC reference designs use gallium nitride FET solutions to achieve maximum performance for e-bike inverters. Significant benefits of a GaN-based motor drive include:
- Lower distortion for lower acoustic noise
- Lower current ripple for reduced magnetic loss
- Lower torque ripple for improved precision
- Lower filtering for a lower cost
The EPC9167 boards’ lower weight and size enable incorporation of the drive into the motor housing and supports low inductance, higher power density motors.
The EPC9167 is a 3-phase inverter made of six EPC2065 eGaN FETs. The EPC9167HC employs twelve EPC2065, two in parallel per switch, to halve the equivalent RDS(on). Both boards are three-phase inverters capable of up to 1 kW operation; The EPC9167HC, when powered with a 48 VDCsupply voltage can deliver 18 ARMSper phase without a heatsink with a temperature rise of just 50°C from eGaN FET case to ambient, with a heatsink, it can provide continuous 25 Arms per phase with peak operation up to 35 Arms.
Gallium nitride (GaN) device technology has an exceptional high electron mobility and low-temperature coefficient. The EPC2065 eGaN® FET has a low RDS(on) of 2.7 mΩ (@25°C). In addition, the lateral structure of the eGaN device and the absence of an intrinsic body diode provide an exceptional low gate charge QG and a zero reverse recovery charge QRR when operated in reverse conduction. Compared to silicon MOSFETs with similar RDS(on), eGaN FETs have five times lower switching losses so that the inverter can be operated at higher PWM frequency and with low dead time.
High PWM frequency and low dead time allow a designer to use ceramic capacitors in the DC-Link, resulting in increased reliability and decreased cost and size. Usually, in conventional e-bike designs, an LC filter is inserted between the battery and the inverter to comply with the electromagnetic emissions rules. The input filter can be removed when the EPC9167 is used at 100 kHz.
In addition, EPC’s eGaN FET solutions for motor drives are offered in a wafer-level chip-scale package (CSP), which allows a reduction in the common source and the power loop parasitic inductances by interposing drain and source connections and by soldering the chip directly onto the printed circuit board. The small footprint allows inserting six or twelve EPC2065 in the board in a relatively small area providing high power density. The EPC9167 boards measure just 130 x 100 mm (including connector).
The reference design boards can be used for sensorless or sensored motor control. The Quick Start Guide (QSG) gives you all the design details for these reference designs.
The growing demand for eMobility fuels the need for highly efficient and compact motor drives. GaN-based inverters increase motor efficiency while reducing their size, weight, and cost while delivering the same performance as an expensive motor using a silicon MOSFET-based inverter; this enables motor systems that are smaller, lighter, less noisy, have more torque, more range, and greater precision. For more information on the EPC9167, this comprehensive application note further describes the reference design and performance results.