GaN Drive Unit Impedance Matching for Noise Reduction
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Solution Overview
Problem
Existing elevator drive units based on silicon IGBTs and MOSFETs have limitations in switching frequency, leading to acoustic noise and larger size due to higher losses and voltage blocking capabilities, which restricts their practical application.
Innovation Solution
The use of gallium nitride switches with a gate driver and snubber circuits, along with equalized turn-off and turn-on trace impedances, allows for higher switching frequencies and reduced losses, enabling smaller and more efficient drive units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If silicon IGBTs and MOSFETs are used in drive units, then the drive unit can achieve adequate voltage blocking capability and reasonable size, but the switching frequency is limited to audible ranges causing acoustic noise
Solution Approach 1:
The patent changes the material parameter of the switching device from silicon to gallium nitride, which fundamentally alters the switching characteristics. This material substitution enables switching frequencies to exceed 20 kHz, moving beyond the audible range and eliminating acoustic noise while maintaining adequate voltage blocking capability.
2Loss of energy
If silicon based switching devices are used, then the drive unit achieves acceptable loss levels of 3-5%, but the heat sink size becomes a major contributor to overall drive unit size
Solution Approach 1:
By changing the material from silicon to gallium nitride, the patent achieves lower power losses (reducing the 3-5% losses to lower levels). This reduction in energy loss directly decreases the thermal load, allowing for smaller heat sink dimensions and reducing the overall drive unit volume.
3Volume of stationary object
If gallium nitride switches are used to achieve higher switching frequencies and reduced losses, then drive unit size can be minimized, but the gate driver circuit complexity increases due to equalized impedance requirements
Solution Approach 1:
The patent applies local quality by implementing equalized impedance specifically in the turn-off trace paths from the gate driver to each parallel gallium nitride switch. This localized impedance matching ensures simultaneous switching of all switches, reducing voltage spikes and oscillations, thereby simplifying the overall gate driver design while maintaining compact dimensions.
Data Source
AI summary
A drive unit for a motor includes a printed circuit board (PCB); a first gallium nitride switch having a gate, the first gallium nitride switch mounted to the PCB; a second gallium nitride switch having a gate, the second gallium nitride switch mounted to the PCB; a gate driver generating a turn-off drive signal to turn off the first gallium nitride switch and turn off the second gallium nitride switch; a first turn-off trace on the PCB, the first turn-off trace directing the turn-off drive signal to the gate of the first gallium nitride switch; and a second turn-off trace on the PCB, the second turn-off trace directing the turn-off drive signal to the gate of the second gallium nitride switch; wherein an impedance of the first turn-off trace is substantially equal to an impedance of the second turn-off trace.