Power


Monolithic GaN half-bridge integration for ultra-compact high-bandwidth motor drives


By Maurizio Di Paolo Emilio, Efficient Power Conversion Corporation (EPC) T


he design requirements for motor drive electronics are being significantly altered by the continuous shift from conventional automation to


mobile robotics. Volume, mass, efficiency, acoustic emission, and dynamic response are all simultaneously constrained by actuators integrated into wearable technology, humanoid robots, and aerial platforms. In these applications, the inverter becomes a tightly coupled component of the electromechanical structure rather than a peripheral power stage.


Robotic joints function in thermally constrained environments and are frequently co-located with sensors, reduction gears, and communication electronics, in contrast to industrial drives, where thermal mass and enclosure volume mitigate electrical inefficiencies. Electrical losses therefore have a direct impact on duty cycle and torque density.


Torque feedback stabilization, impedance control, and high-bandwidth field-oriented control are all modern control strategies that need higher PWM switching frequencies to reduce latency and current ripple. To get rid of noise that can be heard and make sure that low-speed motion is smooth, frequencies close to or above 100 kHz are becoming more and more popular. But these operational conditions show the problems that come with using traditional silicon- based half-bridge designs.


Limitations of discrete silicon inverters


In discrete MOSFET motor inverters, switching performance is constrained by a combination of device physics and interconnection parasitics. Switching energy increases significantly with frequency due


24 March 2026


Figure 1


to output capacitance losses and reverse recovery of the body diode. To prevent shoot-through currents, relatively long dead-times are introduced, which produce nonlinear phase voltage distortion and degrade torque linearity.


Furthermore, gate drivers, bootstrap networks and protection circuits occupy substantial PCB area and introduce loop inductance between driver and transistor. This parasitic inductance produces voltage


Components in Electronics


overshoot, ringing, electromagnetic interference and additional switching losses. As the inverter shrinks, the ratio between interconnection parasitics and intrinsic device impedance worsens, eventually dominating system behaviour. For these reasons, many compact silicon motor drives remain limited to switching frequencies below approximately 40 kHz. While acceptable in industrial drives, this limit becomes restrictive in robotics, where


precision motion and acoustic comfort are essential.


GaN technology


Gallium nitride power transistors provide lower capacitances and negligible reverse recovery, significantly reducing switching losses at high frequency. However, the most relevant characteristic for miniature motor drives lies in the lateral structure of enhancement-mode GaN devices.


www.cieonline.co.uk


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44