Clamped Test Circuit for Non-Avalanche Switching Device Screening
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Solution Overview
Problem
Existing test circuits for switching devices, particularly non-avalanche-proof products, face challenges in accurately evaluating and screening devices without causing damage due to the inability to effectively interrupt currents and perform accurate evaluations, leading to potential device breakage and increased maintenance costs.
Innovation Solution
A test circuit with a clamping circuit that controls voltages and currents to simulate avalanche tests on non-avalanche-proof switching devices, using a clamping circuit between the gate and collector terminals to maintain a voltage higher than the threshold when the device is on and lower than the withstand voltage when off, reducing the risk of breakage and allowing for proper evaluation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a current interruption switch is used to protect non-avalanche-proof switching devices, then device damage is reduced, but the interruption time is too long to completely eliminate damage
Solution Approach 1:
The clamping circuit is activated in advance before the switching device turns off. When the switching device is turned off, the clamping circuit immediately clamps the voltage to a safe level, preventing overvoltage damage without requiring time for current interruption. This preliminary protection mechanism ensures the device is protected from the moment the off-state begins.
Solution Approach 2:
The clamping circuit acts as an intermediary protective element between the switching device and the overvoltage condition. Instead of directly interrupting the current flowing through the switching device, the clamping circuit introduces a parallel path that diverts the excess voltage, thereby protecting the device indirectly while maintaining current flow.
2Object-affected harmful factors
If a clamping circuit is used to protect switching devices, then device protection is provided, but accurate evaluation and screening of non-avalanche-proof products cannot be performed
Solution Approach 1:
The clamping circuit dynamically adjusts its operation based on the switching state. When the switching device is on, the clamping circuit is inactive and does not interfere with normal operation, allowing accurate evaluation. When the switching device turns off, the clamping circuit activates to provide protection. This dynamic behavior enables both accurate evaluation during the on-state and protection during the off-state.
Solution Approach 2:
The clamping circuit changes the voltage parameter at the gate terminal based on the switching state. During the on-state, the gate voltage remains above the threshold to maintain conduction, enabling accurate evaluation. During the off-state, the clamping circuit reduces the gate voltage to below the threshold, providing protection while still allowing the device to be screened for defects through the controlled voltage transition.
3Device complexity
If conventional test circuits are used for non-avalanche-proof products, then simple testing is possible, but device breakage occurs and maintenance costs increase
Solution Approach 1:
The clamping circuit provides beforehand cushioning by preparing a protective voltage clamping mechanism in advance. Before the switching device can be damaged by overvoltage during turn-off, the clamping circuit is already in position to immediately clamp the voltage to a safe level, cushioning the device against potential damage and improving the device survival rate during testing.
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 enables the conductance of low-current, high-voltage tests equivalent to avalanche tests, reducing device damage and maintenance needs, while allowing for accurate evaluation of switching devices without the need for frequent probe and stage replacement.
Implementation Method 1
the clamping circuit being configured to, upon turning on of the switching device responsive to the drive signal, cause a voltage at the third terminal to be a first voltage higher than a threshold of the switching device, and the clamping circuit being configured to, upon turning off of the switching device responsive to the drive signal, and while clamping a voltage at the fourth terminal to a second voltage lower than a withstand voltage of the switching device, cause the voltage at the third terminal to be a third voltage that is between the threshold of the switching device and the first voltage
Data Source
AI summary
A test circuit for testing a switching device. The test circuit includes: a first terminal for receiving a drive signal; second, third and fourth terminals respectively coupled to a ground electrode, a control electrode and a power-supply electrode, of the switching device; and a clamping circuit coupled between the second terminal and the fourth terminal. The clamping circuit is configured to, upon turning on of the switching device responsive to the drive signal, cause a voltage at the third terminal to be a first voltage higher than a threshold of the switching device, and, upon turning off of the switching device responsive to the drive signal, cause the voltage at the third terminal to be a third voltage between the threshold and the first voltage, while clamping a voltage at the fourth terminal to a second voltage lower than a withstand voltage of the switching device.