This paper presents a novel real-time power-device temperature estimation method that monitors the power MOSFET's junction temperature shift arising from thermal aging effects and incorporates the updated electrothermal models of power modules into digital controllers Currently, the real-time estimator is emerging as an important tool for active control of device junction temperature as well as online health monitoring for power electronic systems, but its thermal model fails to address the device's ongoing degradation Because of a mismatch of coefficients of thermal expansion between layers of power devices, repetitive thermal cycling will cause cracks, voids, and even delamination within the device components, particularly in the solder and thermal grease layers Consequently, the thermal resistance of power devices will increase, making it possible to use thermal resistance (and junction temperature) as key indicators for condition monitoring and control purposes In this paper, the predicted device temperature via threshold voltage measurements is compared with the real-time estimated ones, and the difference is attributed to the aging of the device The thermal models in digital controllers are frequently updated to correct the shift caused by thermal aging effects Experimental results on three power MOSFETs confirm that the proposed methodologies are effective to incorporate the thermal aging effects in the power-device temperature estimator with good accuracy The developed adaptive technologies can be applied to other power devices such as IGBTs and SiC MOSFETs, and have significant economic implications

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Real-Time Temperature Estimation for Power MOSFETs Considering Thermal Aging Effects

In this paper, we propose to monitor the thermal parameters of insulated gate bipolar transistor (IGBT) module using the case temperature. This method works during the shutoff period of IGBT module where the case temperature is in the cooling phase By establishing the relationship between the Cauer-type thermal RC parameters and the time constants of case temperature cooling curves, thermal parameters of the IGBT module can be identified. The proposed method is able to eliminate the influence of thermal interface material (TIM) degradation on the monitored results, which is quite challenging for the current case temperature monitoring methods. Moreover, it enables the detection of thermal resistance and thermal capacitance of the TIM and that of the IGBT module at the same time. Experimental tests are performed to validate the accuracy and feasibility of the proposed method. Moreover, impacts of the junction temperature, case temperature sensing position, and thermal coupling on the monitored results are analyzed.

Thermal Parameter Monitoring of IGBT Module Using Case Temperature

The thermal behavior of a power transistor mounted on a dissipator is considered in order to estimate the transistor temperature junction using a measure of the dissipator temperature only. The thermal transfers between the electric power applied to the transistor, the junction temperature, and the dissipator temperature are characterized by two fractional transfer functions. These models are then used in a Control Output Observer (COO) to estimate the transistor junction temperature.

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Fractional Models for Thermal Modeling and Temperature Estimation of a Transistor Junction

This paper proposes a thermal network parameter estimation method for insulated-gate bipolar transistor (IGBT) modules using the junction temperature cooling curve. The proposed method finds the RC parameters of a fourth-order Cauer network by establishing a relationship between RC parameters and time constants of junction temperature response curves. Experimental tests are performed to validate the accuracy of the developed method. Results show that the difference of total thermal resistance between the proposed method and IEC standard is below 2%. Advantages of the proposed method over the existing methods are that the proposed method does not need 1) to know the power loss information of IGBT and 2) to heat the IGBT module up to thermal steady state. In addition, we show that the identified RC parameters can be used for condition monitoring and junction temperature estimation.

Thermal Network Parameter Estimation Using Cooling Curve of IGBT Module

In this paper, we propose a method to monitor the thermal parameters of insulated gate bipolar transistor (IGBT) module using the junction temperature cooling curves. Relationship between the time constants of junction temperature cooling curves and thermal parameters of the Cauer model is established for condition monitoring. Advantages of the proposed approach include no need to measure the power loss and to heat the module to thermal equilibrium. Simulation and experimental tests are performed to verify the accuracy and effectiveness of the proposed method. Results show that the proposed method can not only monitor the thermal parameter of a single layer, but also enable the concurrent monitoring of thermal parameters in multiple layers.

Thermal Parameter Monitoring of IGBT Module Using Junction Temperature Cooling Curves

Temperature management and control are among the most critical functions in power electronic devices, as operating temperature and thermal cycling can affect device performance and reliability. Therefore, it is useful to develop a device thermal model, which can be implemented in real-time and used to estimate temperature variations within the active region of the device. This paper begins by presenting a device thermal model suitable for a MOSFET power-switch derived from the seven-layer physical structure of the device. However it is shown subsequently that a third-order thermal model can give satisfactory estimates of device temperature. Furthermore, computational efficiency can he improved if the model is implemented as a third-order difference equation. Modelling results are compared with real-time temperature device measurements.

C.M. Johnson

Papers

Open loop real-time power electronic device junction temperature estimation