Test Circuit Current Interruption for Switching Device Defect Detection
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Solution Overview
Problem
Avalanche tests for switching devices, such as MOSFETs and IGBTs, face challenges in detecting defects without causing thermal damage to normal products, as increasing the peak current value for defect detection risks damaging products with minor defects.
Innovation Solution
A test circuit with a current interrupting device that turns off after a predetermined period shorter than the time it takes for the drive current to reach zero, reducing the energy applied to the switching device and minimizing thermal damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the peak value of the current flowing through the switching device is increased to detect defects, then defect detection capability is improved, but thermal damage to normal products occurs
Solution Approach 1:
The patent applies periodic action by controlling the current to flow through the switching device in periodic pulses rather than continuous DC. The current is applied for a predetermined time period that is shorter than the time required for the drive current to reach zero, creating a periodic on-off pattern that limits energy accumulation and prevents thermal damage while maintaining defect detection capability.
Solution Approach 2:
The patent changes the time parameter of current application from the natural current decay time to a predetermined shorter duration. By controlling the current application time to be shorter than the time for drive current to reach zero, the energy delivered to the device is reduced, preventing thermal damage while still allowing defect detection through the avalanche effect.
2Object-affected harmful factors
If the current is interrupted before the drive current reaches zero, then thermal damage is suppressed, but the testing completeness may be reduced
Solution Approach 1:
The patent applies partial action by interrupting the current before it naturally reaches zero, delivering just enough current to detect defects through the avalanche effect but stopping before excessive energy causes thermal damage. This partial current application is sufficient for defect detection while preventing harmful thermal effects.
Solution Approach 2:
The patent rushes through the critical phase by quickly applying current for a predetermined short duration to achieve defect detection, then immediately interrupting the current before the drive current naturally decays to zero. This rapid action sequence completes the essential testing function while avoiding the harmful thermal phase.
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 effectively suppresses thermal damage to switching devices while allowing for the detection of defects by increasing the peak current value without exceeding the energy threshold that causes thermal damage.
Implementation Method 1
if the peak value of the current is increased, even normal products with defects that do not matter will be thermally damaged
Data Source
AI summary
A test circuit for conducting a test on a switching device having a ground electrode, a control electrode, and a power-supply electrode. The test circuit includes: a first terminal configured to be connected to the ground electrode of the switching device; a second terminal configured to be connected to the control electrode of the switching device; a third terminal configured to be connected to the power-supply electrode of the switching device; a fourth terminal configured to receive a power supply voltage; and a first switch connected between the third terminal and the fourth terminal, and being configured to turn off in response to a predetermined time period having elapsed since turning off of the switching device. The predetermined time period is shorter than a time period from when the switching device is turned off to when a drive current flowing through the switching device reaches zero without being interrupted.