High-Efficiency GaN Motor Drive
A 3 kW three-phase servo drive using GaN half-bridges, reaching 97.4 % peak efficiency in a 40 % smaller envelope.
- Client
- Nexora Robotics
- Sector
- —
- Year
- 2023
- Duration
- 24 weeks
- Layers
- 6
- Board size
- 110 × 84 mm
- Placements
- 292
- IPC class
- Class 2
Stack-up: 1.6 mm FR-4, 2 oz outer with 3 oz plated power layers, IMS heat path
The challenge
Replacing a silicon IGBT drive with GaN to reach the efficiency and size targets, without the gate ringing and common-mode noise that had made two earlier in-house attempts unusable above 60 kHz.
Our approach
Commutation loop inductance was the design target from the first placement study. Half-bridges were laid out with vertical loops through the stack rather than lateral ones, giving roughly 1.8 nH of loop inductance. Gate loops were kept under 4 mm with the driver returned to the source sense pin, and a Kelvin connection separated gate return from power return. Current sensing moved to shunts with a dedicated differential path away from the switching node.
The outcome
The drive runs at 100 kHz with 97.4 % peak efficiency and gate ringing under 1.2 V overshoot. Volume fell 40 % against the outgoing IGBT design, and conducted emissions met CISPR 25 Class 3 with the filter originally budgeted.
Measured outcome
97.4%
Peak efficiency
−40%
Volume
1.8nH
Loop inductance
100kHz
Switching frequency
Loop inductance is the whole game
GaN switches fast enough that a few nanohenries of commutation loop turns into tens of volts of overshoot. Routing the loop vertically through the stack-up, rather than around the board, is what makes 100 kHz operation calm rather than marginal.
Kelvin returns everywhere they matter
Separating gate return from power return removes the source inductance from the gate loop. Without it, the device turns itself partially back on during a fast transition — the mechanism behind both earlier attempts.
Have a board that needs designing?
Send us the constraints — schematic, mechanical envelope, volume, timeline. You will get a considered response from an engineer within one business day, not a brochure.
We reply within one business day, from an engineer.