IGBT Power Cycle Life Estimation via Temperature Warning Signals
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Solution Overview
Problem
Conventional intelligent power modules (IPMs) continue switching operations of IGBTs until just before protection, leading to increased heat stress and reduced power cycle life, which negatively impacts reliability due to significant temperature fluctuations.
Innovation Solution
A semiconductor device with a control IC that includes a chip temperature detector, a case temperature detector, and an abnormality detection circuit, which outputs warning and protection signals to stop switching operations when temperature thresholds are exceeded, and estimates power cycle life to forcibly stop the device before damage occurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the switching operation of the IGBT is continued until immediately prior to protection signal output, then the device can maintain productivity, but the power cycle life decreases due to increased heat stress
Solution Approach 1:
The control IC performs preliminary action by outputting a warning signal when the chip temperature reaches a warning threshold before the protection threshold is reached. This allows the external device to take preventive measures (such as reducing load or improving cooling) before actual damage occurs, thereby extending power cycle life while maintaining productivity during normal operation
Solution Approach 2:
The control IC implements feedback by continuously monitoring chip temperature and case temperature, and providing feedback signals (warning signal and protection signal) to the external device based on temperature thresholds. This feedback mechanism enables the external device to adjust operating conditions to prevent excessive heat stress, thus extending power cycle life without significantly impacting productivity
2Reliability
If the chip temperature is monitored and warning signal is output, then the reliability is improved, but the device complexity increases due to additional temperature detection and control circuits
Solution Approach 1:
The control IC merges multiple functions into a single integrated circuit: it combines the chip temperature detector, case temperature detector, and protection circuit into one control IC. This integration achieves reliable overheating protection while minimizing the increase in overall device complexity by consolidating components rather than adding separate discrete elements
Solution Approach 2:
The control IC achieves multi-functionality by incorporating both chip temperature monitoring and case temperature monitoring capabilities within the same device. This universal approach allows a single control IC to perform multiple protection functions, improving reliability without proportionally increasing device complexity
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 solution improves reliability by preventing overheating-induced deterioration and extending the power cycle life of IPMs by stopping switching operations when temperature thresholds are reached, thereby reducing heat stress and maintaining device integrity.
Implementation Method 1
a chip temperature detector connected to the control IC to measure a chip temperature of the power semiconductor device
Implementation Method 2
a case temperature detector connected to the control IC to measure a case temperature that is defined as a temperature at a portion of the semiconductor device other than the power semiconductor device
Implementation Method 3
aluminum wire bonds on the surface of the IGBT chip experience heat stress, which results in fatigue on and promotes deterioration of the aluminum wire bonds
Implementation Method 4
significant increases and decreases in IGBT temperatures cause solder joints between the IGBT chip and insulating substrate as well as solder joints between the insulating substrate and case (copper base) to deteriorate, which can cause malfunctions to occur due to cracking
Data Source
AI summary
Power cycle life of an intelligent power module that includes an IGBT is estimated by an abnormality detection circuit(s) while a chip temperature detection circuit or a case temperature detection circuit is outputting a chip overheating warning signal or a case overheating warning signal. Once the estimated power cycle life has reached a prescribed value, the abnormality detection circuit outputs an abnormality detection signal to forcedly and permanently stop operation of a driver circuit that drives an IGBT. The abnormality detection circuit may include a prescribed period calculation circuit that calculates the duration of the warning signal, a prescribed count calculation circuit that calculates the number of times the warning signal has been generated, and/or a cumulative time calculation circuit that calculates that the cumulative duration of periods in which the warning signal has been generated so as to estimate the power cycle life of the intelligent power module.