DC Inverter Gate Coil Inductive Coupling for Voltage Spike Mitigation
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Solution Overview
Problem
In electrified vehicle propulsion systems, simultaneous turn-off of multiple switching devices leads to excessive voltage spikes, necessitating higher voltage ratings for IGBTs, which increases costs and reduces efficiency.
Innovation Solution
The use of inductively coupled gate coils connected between gate drivers and gate loops, sensing the parasitic inductance of the DC link, modifies the turn-off performance by adding a negative voltage to the gate drive signal, reducing the rate of current decrease and thereby mitigating voltage spikes and switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If switching devices are turned off simultaneously in multiple converter bridges, then power conversion efficiency is improved, but voltage spikes increase requiring higher voltage ratings
Solution Approach 1:
The gate coil acts as an intermediary element between the gate driver and the IGBT gate terminal. It introduces a controlled inductive voltage that modifies the gate drive waveform, thereby mediating the switching process to reduce voltage spikes while maintaining efficient simultaneous switching operation
Solution Approach 2:
The gate coil modifies the gate drive signal in advance during the turn-off transition, creating a controlled current decrease profile before the main switching event. This preliminary action on the gate signal prevents excessive voltage spikes from occurring in the first place
2Loss of energy
If switching speed is increased to reduce switching losses, then efficiency is improved, but voltage overshoot and device stress increase
Solution Approach 1:
The gate coil introduces a dynamic, time-varying inductive effect that adapts during the switching transition. The inductive voltage generated by the gate coil dynamically controls the gate current profile, enabling fast switching while preventing voltage overshoot through real-time modulation of the gate drive characteristics
Solution Approach 2:
The gate coil changes the effective parameters of the gate drive circuit during switching. By introducing inductive coupling, it modifies the gate current waveform shape and duration, thereby changing the switching trajectory to achieve low loss without excessive voltage stress
3Reliability
If switching devices with higher voltage ratings are used to withstand voltage spikes, then reliability is improved, but parts cost and packaging space increase
Solution Approach 1:
The gate coil provides beforehand cushioning by pre-modifying the gate drive signal to prevent excessive voltage spikes from occurring. This protective action is built into the switching mechanism itself, cushioning against voltage overshoot before it can damage the devices, thereby allowing use of lower voltage-rated, more cost-effective IGBTs
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces voltage spikes by 80V and decreases switching energy loss by 28%, allowing for lower IGBT voltage ratings and improved efficiency in power electronics converters.
Implementation Method 1
A plurality of gate coils are provided, wherein each gate coil is connected in series between a respective gate driver and a respective gate loop and is each respectively inductively coupled to the link inductance
Data Source
AI summary
An electrified vehicle propulsion system uses current feedback to modify gate drive signals to suppress voltage spikes and increase switching efficiency. A DC link having a link capacitor and a link inductance is connected to first and second converters. A first converter bridge has a first phase leg with first upper and lower switching devices, each switching device having a respective gate loop. A second converter bridge has a second phase leg with second upper and lower switching devices, each switching device having a respective gate loop. A plurality of gate drivers provide gate drive signals to respective gate loops for turning the respective switching devices on and off. A plurality of gate coils are provided, wherein each gate coil is connected in series between a respective gate driver and a respective gate loop. Each gate coil is respectively inductively coupled to the link inductance.