IGBT Junction Temperature Monitoring via Miller Plateau Timing
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Solution Overview
Problem
Existing methods for measuring the junction temperature of IGBT devices lack timely resolution and precision, making them unsuitable for online temperature monitoring, especially at frequencies close to control frequencies.
Innovation Solution
A system and method that differentiate the gate-emitter voltage characteristic to obtain pulses correlating with the Miller plateau phase during switch-off, measuring the time delay between these pulses to determine the junction temperature and remaining lifetime of the IGBT device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard temperature measuring techniques (infrared camera, thermal couple, internal gate resistance measurement) are used, then temperature information can be obtained, but the measurement precision and timely resolution are insufficient for online monitoring at control frequencies
Solution Approach 1:
The patent replaces physical temperature sensing mechanisms (infrared cameras, thermal couples) with an electrical measurement approach. By measuring the Miller plateau duration in the gate-emitter voltage waveform, the system derives junction temperature information without direct thermal contact or infrared detection, thereby eliminating the thermal response delay inherent in physical temperature sensors.
Solution Approach 2:
The patent introduces the Miller plateau duration as an intermediary parameter that correlates with junction temperature. Instead of measuring temperature directly, the system measures the duration of the Miller plateau phase in the gate-emitter voltage characteristic, which serves as a temporal proxy for temperature that can be measured with high speed and precision.
2Reliability
If thermal network simulation based on base plate temperature is used, then IGBT temperature can be estimated, but the delayed thermal response prevents timely resolution close to control frequency
Solution Approach 1:
The patent replaces the thermal network simulation approach with an electrical waveform analysis method. By measuring the Miller plateau duration directly from the gate-emitter voltage characteristic, the system obtains temperature information with electrical measurement speed rather than thermal simulation speed, achieving response times suitable for online control.
Solution Approach 2:
The patent performs temperature-related measurement during the switching process itself rather than after the fact. The Miller plateau duration is measured during the switch-off phase, providing real-time temperature information before thermal conditions change significantly, thus enabling predictive control rather than reactive monitoring.
3Measurement precision
If direct access to IGBT device package or specially designed IGBT devices is required, then temperature can be measured, but the device complexity and ease of operation are compromised
Solution Approach 1:
The patent uses the IGBT device's own switching characteristics to provide temperature information. The Miller plateau duration, which is an inherent feature of the IGBT's switching behavior, serves as a built-in temperature sensor. This eliminates the need for external temperature sensing components or modified device structures, as the device itself provides the measurement data through its normal operation.
Solution Approach 2:
The patent uses the gate-emitter voltage waveform, specifically the Miller plateau phase, as an intermediary that contains temperature information. This waveform feature is naturally present during IGBT switching and can be extracted through signal processing, providing temperature measurement without requiring direct access to the device package or special hardware modifications.
Data Source
AI summary
A system and method are provided for monitoring in real time the operating state of an IGBT device, to determine a junction temperature and/or the remaining lifetime of an IGBT device. The system includes a differential unit configured to receive a gate-emitter voltage characteristic of the IGBT device to be measured and to differentiate the gate-emitter voltage characteristic to obtain pulses correlating with edges formed by a Miller plateau phase during a switch-off phase of the IGBT device. The system also includes a timer unit configured to measure the time delay between the obtained pulses indicating the start and end of the Miller plateau phase during the switch-off phase of the IGBT device, and a junction temperature calculation unit configured to determine at least one of the junction temperature of the IGBT device and/or the remaining lifetime of the IGBT device based on the measured time delay.