Gate Driver Two-Level Turn-Off for Power Switch Overshoot
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Solution Overview
Problem
Power modules with parasitic inductances, such as those in IGBTs, experience transient voltages during quick power switch shutdowns, which can physically damage the switches, especially during overcurrent fault conditions.
Innovation Solution
Implementing a two-level turn-off mechanism using a microcontroller unit and a less complex gate driver, where a signal generator generates a gate driver input signal with a first and second voltage, toggling between them to provide an intermediate voltage during shutdown, reducing overshoot and eliminating the need for external diodes and capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a power switch is shut off very quickly during overcurrent fault condition, then the response speed is improved, but parasitic inductances create transient voltages that can physically damage the power switches
Solution Approach 1:
The gate driver input signal toggles periodically between first and second voltages during a third time period, creating periodic gate drive signals that progressively reduce the gate voltage. This periodic action allows the gate voltage to be reduced in steps rather than abruptly, reducing dv/dt and minimizing transient voltage spikes caused by parasitic inductances while still achieving quick fault response.
Solution Approach 2:
Before completely shutting off the power switch, the circuit first applies an intermediate voltage level to the gate by toggling the input signal. This preliminary action reduces the gate voltage from the third voltage to an intermediate voltage during the third time period, preparing the switch for safe turn-off and preventing excessive transient voltages before the main shutdown occurs.
2Reliability
If a complex gate driver is used to reduce transient voltages, then the reliability is improved, but the device complexity and cost increase
Solution Approach 1:
The microcontroller unit's signal generator directly generates the toggling gate driver input signal without requiring external diodes or capacitors. The circuit uses internally available components and the natural toggling capability of the signal generator to create the intermediate voltage effect, making the system self-sufficient and eliminating the need for additional protective components that would increase complexity.
Solution Approach 2:
The invention extracts and eliminates the need for external diodes and capacitors that are traditionally required in complex gate driver circuits. By using the signal generator's inherent toggling capability to directly control the gate driver input, the circuit removes unnecessary external components, simplifying the overall system while maintaining transient voltage protection functionality.
3Object-affected harmful factors
If traditional gate driver circuits with external diodes and capacitors are used, then the transient voltage protection is achieved, but the manufacturing cost and area increase
Solution Approach 1:
The functionality of external protective diodes and capacitors is merged into the signal generator's output stage. The signal generator directly produces the toggling signal that creates the intermediate voltage effect, combining the gate drive function with the transient voltage protection function in a single integrated approach, thereby eliminating the need for separate external protective components and reducing manufacturing cost and PCB area.
Data Source
AI summary
An electronic circuit for controlling a power switch having a gate input, includes a signal generator configured to generate a gate driver input signal. The gate driver input signal has a first voltage during a first period of time, a second voltage during a second period of time, and toggles between the first voltage and the second voltage during a third period of time. The electronic circuit also includes a gate driver configured to receive the gate driver input signal and to provide a gate driver output signal based on the gate driver input signal. The signal generator is configured to cause the gate driver input signal to toggle during the third period of time such that the gate driver output signal has a third voltage during the second period of time, and an intermediate voltage that is less than the third voltage during the third period of time.