Power


Unlike vertical silicon MOSFETs, lateral GaN technology allows power devices and control circuitry to be fabricated on the same semiconductor substrate. This property enables the realization of a monolithic half-bridge cell integrating gate drivers, level shifters and bootstrap functionality within the switching device itself. The resulting structure reduces the commutation loop to micrometre-scale dimensions and eliminates PCB-dependent gate paths.


The reduction of parasitic inductance produces predictable switching waveforms and allows extremely short dead-times. The improvement is not only electrical but functional: phase voltage distortion decreases, torque ripple is reduced, and current control bandwidth increases. Consequently, the inverter behaves more like an ideal voltage source than a pulse approximation filtered by motor inductance.


There are two ways to run high- bandwidth motor control at the same time. Short current pulses determine peak torque capability during dynamic events like acceleration, landing stabilization, or disturbance rejection. Thermal equilibrium limits the continuous current when the motion is steady.


Because robotic actuators usually have torque constants close to 1 Nm/Arms, phase current is a direct measure of how much mechanical output they can produce. To predict how well an actuator will work, it is important to accurately measure the RMS and peak currents. Switching losses can only stay acceptable when switching frequencies get close to 100 kHz if both the device capacitances and the commutation inductances are kept as low as possible at the same time. The monolithic GaN half- bridge design meets this need by getting rid of the main effect of PCB parasitics.


Integration of multiple axes Robotic platforms often have more than one motor in a small space. Traditional inverter architectures do not scale well because each axis needs its own driver stage and passive components. The resulting layout complexity makes it harder to design for heat and increases interference between axes.


Integrated switching cells let you put a lot of inverters on one small board close together. A centralized controller can send PWM signals to multiple phases with symmetric geometry. This makes the timing more consistent and reduces electromagnetic coupling. This simplification


www.cieonline.co.uk Figure 2


of architecture is especially important in drone electronic speed controllers and articulated robotic limbs, where multiple motors work together to move.


Example


A three-phase module that uses monolithic GaN half-bridges to combine power transistors, gate drivers, level shifting circuitry, and bootstrap functionality into


References


EPC33110 – 100 V, 3-Phase ePower™ Stage for High-Density Motor Drives: https://epc-co.com/epc/products/gan-fets-and-ics/epc33110 EPC91122: 20 ARMS


, 3-Phase Motor Drive Inverter: https://epc-co.com/epc/products/evaluation-boards/epc91122 Components in Electronics March 2026 25


one small package is an example of the approach described. The device works with voltages up to 80 V (with transients up to 100V) and only needs one 5 V driver supply. It can take standard 3.3 V or 5 V logic inputs, which cuts down on the number of external interfaces needed. The design is optimized for low commutation inductance and good heat transfer through cooling surfaces on the top side.


A representative implementation of the described architecture is provided by the EPC33110 monolithic three-phase GaN inverter module and its associated EPC91122 reference platform. The EPC33110 integrates three GaN half-bridges together with gate drivers, level shifters and bootstrap circuitry within a single compact package operating up to 100 V. Experimental characterization performed using the EPC91122 motor drive board in a robotic joint setup demonstrates stable operation at switching frequencies around 100 kHz with very short dead-time intervals. Under dynamic load conditions representative of robotic motion, phase currents of approximately 20 ARMS can be delivered for short pulses, corresponding to high peak torque capability. Under natural convection cooling, continuous current capability of about 13 ARMS per phase is achieved at thermal equilibrium, while airflow-assisted environments typical of aerial propulsion systems allow higher sustained currents.


Figure 1: Overview of EPC91122 board – three-phase inverter for drones and humanoid motor joints


Figure 2: Output current capabilities of EPC33110 operated at 100 kHz PWM in a humanoid robot joint: (a) detail of the motor phase current reaching 20 ARMS


(b)


overview of the load torque 2 second pulses at 20 Nm peak


Conclusion


Miniaturized robotic systems demand power electronics that combine efficiency, precision and integration density. The transition from discrete silicon half- bridges to monolithic GaN switching cells represents a fundamental architectural evolution rather than a simple improvement in semiconductor performance. By minimizing parasitic inductances and enabling high-frequency switching with short dead-time, monolithic GaN inverters improve torque linearity, acoustic behaviour and dynamic response. Equally important, they allow multi-axis motor control to be realized within extremely compact volumes. As robotics continues to converge toward human-interactive and mobile platforms, the integration level of the power stage becomes a defining parameter of actuator capability, positioning monolithic GaN architectures as a key enabler of next- generation electromechanical systems. https://epc-co.com


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