Semiconductor Switch Monitoring for Overvoltage Damage Detection
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Solution Overview
Problem
Switchable semiconductor components, such as MOSFETs, can be irreversibly damaged by overvoltage when switching off inductive loads, leading to uncontrollable situations, especially in safety-critical applications like electric vehicles, due to avalanche breakdowns and thermal damage.
Innovation Solution
A monitoring device with a protective circuit connected in parallel to the semiconductor component measures and compares electrical variables with stored critical values to detect potential damage, using a sample and hold unit and analog-to-digital converter to identify peak voltages and currents, and issues a damage report to prevent further usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection circuit is connected in parallel with the semiconductor device to prevent breakdown voltage damage, then the semiconductor device is protected from overvoltage, but the complexity of the device increases
Solution Approach 1:
A protection circuit is introduced as an intermediary element connected in parallel with the semiconductor device. This protection circuit includes a clamping diode that activates at a lower voltage than the breakdown voltage of the semiconductor device, dissipating overvoltage before it can damage the main device. The intermediary protection circuit absorbs the harmful overvoltage spikes while allowing the semiconductor device to continue functioning normally.
2Strength
If the semiconductor device is designed to withstand higher voltages to avoid breakdown, then the device can handle larger overvoltage, but the device size and cost increase
Solution Approach 1:
The protection circuit is configured to activate beforehand at a voltage level lower than the semiconductor device's breakdown voltage. The clamping diode in the protection circuit conducts when the voltage reaches this lower threshold, creating a cushioning effect that limits the voltage across the semiconductor device. This prevents the semiconductor device from ever experiencing the full breakdown voltage stress, allowing it to be designed with lower voltage ratings and smaller dimensions.
3Measurement precision
If monitoring is performed continuously to detect damage early, then damage detection accuracy improves, but the complexity and power consumption of the monitoring system increases
Solution Approach 1:
A monitoring circuit is implemented that continuously measures the voltage across the semiconductor device and provides feedback to a control system. When the measured voltage exceeds a predetermined threshold indicating potential damage, the monitoring circuit generates a signal that triggers a protective response, such as shutting down the device or activating additional protection measures. This feedback mechanism enables real-time damage detection and response without requiring complex continuous analysis.
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
The solution effectively detects and prevents the use of damaged semiconductor components, ensuring safe operation by avoiding uncontrolled states and maintaining critical functions in electric vehicles.
Implementation Method 1
The inductance acts as an energy storage device that is discharged during the switch-off process. The overvoltage can exceed the breakdown voltage of the semiconductor device. In this case, charge carriers break away in an avalanche-like manner through a normally barrier layer of the semiconductor device.
Implementation Method 2
The protection circuit becomes conductive at a lower voltage than the breakdown voltage of the semiconductor device. If the overvoltage exceeds the protection circuit's design voltage, the overvoltage can be dissipated by the protection circuit.
Data Source
Figure 1
AI summary
The present invention relates to a method for monitoring a switchable semiconductor device (Q1) with a protection circuit (124) connected in parallel to the semiconductor device (Q1), wherein an electrical quantity (114) applied to the semiconductor device (Q1) and the protection circuit (124) is detected, and damage to the semiconductor device (Q1) and/or the protection circuit (124) is detected when the electrical quantity (114) is greater than a previously known critical value (116).