Feature: Power electronics


Figure 1: EPC91122 PCB


Design constraints and architectural implications of humanoid robot


joints By Maurizio Di Paolo Emilio, Director of Global Marketing Communications, Effi cient Power Conversion (EPC)


H


umanoid robotics is changing what motor drive electronics must do. In traditional industrial drives, the inverter is usually placed in an outside cabinet, connected to the motor by cables. However, in humanoid robots, actuators must fi t into joints that replicate how people move – like


the shoulder, elbow, wrist, and even fi ngers. T is architectural shiſt forces power electronics to migrate inside the motor housing, where space, thermal dissipation and dynamic response requirements are signifi cantly more challenging.


Humanoid actuation trends Two parallel directions are emerging in humanoid actuation: High-power joints and extreme miniaturisation. Hips and torso require higher current and benefi t from lower conduction losses and improved thermal handling. Wrists, hands


20 April 2026 www.electronicsworld.co.uk


and fi ngers require maximum integration, where sensors and even current shunts approach the size of the power IC itself. As switching devices continue shrinking, sensing technology


could become the dominant size limitation rather than the power semiconductors. Future actuator electronics may integrate current sensing directly into the power module to overcome this bottleneck.


System-level constraints in humanoid joints A humanoid joint actuator simultaneously requires high torque density (large torque from a very small motor), high dynamic bandwidth for natural motion control, low thermal rise in confi ned spaces, high electrical effi ciency, as well as minimal weight and volume. Because the inverter is a physical part of the actuator, cabling inductance and parasitics must also be kept to a minimum. Here, the drive needs to fi t the power stage, sensing, control and communication into a small footprint, which is usually round, to fi t the shape of the motor. T e main point is that power density, not just effi ciency,


becomes the most important design metric. You can’t use a drive that is big but works well; on the other hand, a small drive with high switching losses can’t get rid of heat inside a sealed joint.


Integrated inverter architecture A typical joint integrated inverter includes three-phase half-bridge power stage, gate drivers, microcontroller for fi eld-orientated control, rotor position sensing (magnetic encoder), phase current sensing, DC link capacitors, communication interface and onboard auxiliary power supply. To fi t inside a motor housing, the electronics are implemented


on a circular PCB matching the motor diameter; see Figure 1. Ceramic DC link capacitors are preferred due to volumetric effi ciency and low ESL, enabling fast current transitions. T e heart of the system can be a monolithic three-phase GaN


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