Bodo Arlt, founder and publishing editor of Bodo’s Power Systems recently got the opportunity to talk to Efficient Power Conversion (EPC) CEO and co-founder Alex Lidow. They discussed why motors are smaller, faster and more precise with GaN and also what Alex believes is the next big market for this evolving technology.
Alex said that the best fit for EPC’s GaN devices is for brushless DC motors where the input voltage is between 24 V and 150 V, typically 48 V and the emerging 96 V. According to him, the applications to benefit the most from motor drives using GaN technology include servo drives, e-bikes and e-scooters, warehouse, autonomous robots, lean production line collaborative robots, medical robotics, and industrial drones.
The rapid emergence of e-scooters and e-bikes has created a surge in demand for compact, lightweight motor drives. They have a very fast-growing market but seem to be cost-sensitive. The high frequency capability of GaN allows for the design of much smaller motor drives and this miniaturization enables better esthetic, lighter weight, and lower cost solutions for eMobility. Also, the higher efficiency provided by GaN is critical for longer battery life to achieve an increased range between charges in these vehicles.
For motor drive applications a GaN inverter can easily operate at 100 kHz PWM frequency thanks to its lower switching dissipation and smoother switching at the allowed dv/dt. This high frequency of GaN motor drives provides a few benefits. An immediate result is that voltage and current ripples at the battery cables are drastically reduced, so there is no need for any LC input filter based on electrolytic capacitors. Ceramic capacitors can replace bulky, temperature-sensitive, and lower reliability electrolytic capacitors, thus saving costs, increasing efficiency, reliability, and lifetime. For example, in a 400 W motor drive, as would be used in an e-bike, a 330 uF electrolytic capacitor can be replaced with 22 uF of ceramic capacitors. In addition, the input filter inductor can be completely eliminated.
Considering a system made of a motor-plus-inverter, a conventional 20 kHz MOSFET inverter can reach 98% efficiency and a GaN inverter can reach 98% when running at 100 kHz. But there is one big difference: the GaN inverter allows very small dead time (tens of ns). Dead time in motor drives is responsible for an even harmonic (the sixth) on the torque that produces only vibration and heat and does not contribute to motion. With a GaN inverter, the even harmonics of the torque is completely removed and the motor itself becomes more efficient delivering more torque per ampere. So, the total system becomes more efficient due to the GaN inverter.
The advantages of compact, lightweight design also benefit many other applications such as autonomous robots and industrial drones. Some of EPC’s earliest motor drive success was in precision motion and positioning and some of the earliest adoption of GaN-based motor drives was for medical robotics. The weight and size of the motor are also important for these designs but precision is even more crucial. The ability to operate at higher frequencies increases control bandwidth for the motor. This increases the precision at which the motor can be controlled. In addition, the higher frequency reduces or even eliminates, mechanical vibration which is crucial to being able to take advantage of the higher control precision. Precision can save lives in medical applications.
There is also an emerging use case for GaN in a myriad of small motors that are inside vehicles. The value for GaN devices in 48 V automotive motors is that they can reduce the size and weight of the motors, reduce audible noise, get better torque, extend battery life, and provide higher efficiency. EPC has a growing line of AEC-Q101 qualified FETs for automotive applications and will be adding AEC-Q100 qualified GaN ICs to the product portfolio as well.
Further technical information on EPC’s GaN solutions for Motor Drive applications can be found on the motor drive landing page on the EPC website. It has an entire repository of information on GaN in motor drives including applications notes and videos. In addition, EPC’s team of field applications engineers is always available to help with everything from product selection to layout reviews and production assistance. The easiest way to reach them is to submit an inquiry via EPC’s Ask a Motor Drive Expert feature.
