阅读说明：本技术 一种基于组合热敏电参数灵敏度增强的SiC MOSFET结温检测方法 (SiC MOSFET junction temperature detection method based on combined thermosensitive electrical parameter sensitivity enhancement ) 是由 杨跃茹 秦海鸿 莫玉斌 陈文明 付大丰 谢利标 胡黎明 于 2020-11-19 设计创作，主要内容包括：本发明提供了一种基于组合热敏电参数灵敏度增强的SiC MOSFET结温检测方法,包括以下步骤：采用控制变量法对SiC MOSFET进行温升测试；根据测试数据标定热敏电参数与其相关变量的关系曲线；根据热敏电参数与其相关变量的关系曲线得到拟合方程；对热敏电参数与其相关变量的相关性进行分析,当存在两个热敏电参数与其多个相关变量具有线性关系,并且这两个热敏电参数具有除结温外的同一相关变量,所述同一相关变量与结温对各自热敏电参数相关性的一致性相反时；消去这两个热敏电参数除结温外的同一相关变量。本发明能够在不增加检测变量的同时提高结温检测的灵敏度,有效缓解了单一热敏电参数存在除结温外影响因素多和灵敏度低的问题,提高了SiC MOSFET结温检测精度。(The invention provides a SiC MOSFET junction temperature detection method based on combined thermosensitive electrical parameter sensitivity enhancement, which comprises the following steps: carrying out temperature rise test on the SiC MOSFET by adopting a control variable method; calibrating a relation curve of the thermal sensitive electrical parameter and the related variable thereof according to the test data; obtaining a fitting equation according to a relation curve of the thermal sensitive electrical parameter and the related variable thereof; analyzing the correlation between the temperature-sensitive electrical parameters and the related variables thereof, when two temperature-sensitive electrical parameters have linear relations with a plurality of related variables thereof and have the same related variable except the junction temperature, and the consistency of the same related variable and the junction temperature on the correlation of the respective temperature-sensitive electrical parameters is opposite; the same relevant variables of the two temperature-sensitive electrical parameters except for the junction temperature are eliminated. The invention can improve the sensitivity of junction temperature detection without increasing detection variables, effectively solves the problems of more influence factors except junction temperature and low sensitivity of a single thermal sensitive electrical parameter, and improves the junction temperature detection precision of the SiC MOSFET.)

1. A SiC MOSFET junction temperature detection method based on combined thermosensitive electrical parameter sensitivity enhancement is characterized by comprising the following steps:

carrying out temperature rise test on the SiC MOSFET by adopting a control variable method;

calibrating a relation curve of the thermal sensitive electrical parameter and the related variable thereof according to the test data;

obtaining a fitting equation according to a relation curve of the thermal sensitive electrical parameter and the related variable thereof;

analyzing and comparing the correlation between the temperature-sensitive electrical parameters and related variables thereof, and eliminating the same correlation variables of the two temperature-sensitive electrical parameters except the junction temperature in a linear combination mode when two temperature-sensitive electrical parameters have linear relations with a plurality of correlation variables thereof and have the same correlation variables except the junction temperature, and the consistency of the correlation between the same correlation variables and the junction temperature on the respective temperature-sensitive electrical parameters is opposite;

and taking the thermosensitive electrical parameters after linear combination as combined thermosensitive electrical parameters.

2. The SiC MOSFET junction temperature detection method based on combined thermal electrical parameter sensitivity enhancement of claim 1, wherein: the temperature-sensitive electrical parameter has a plurality of related variables including junction temperature, the relation between the temperature-sensitive electrical parameter and the related variables is calibrated in advance through test data, and the SiC MOSFET junction temperature at the moment is indirectly obtained through detecting the values of the related variables in real time under specific working conditions.

3. The SiC MOSFET junction temperature detection method based on combined thermal electrical parameter sensitivity enhancement of claim 1, wherein: the same correlation variable is inversely correlated with the junction temperature to respective temperature-sensitive electrical parameter correlations, including:

the junction temperature in the temperature-sensitive electrical parameters has consistent correlation with the two temperature-sensitive electrical parameters, and the correlation of the same correlation variable with the two temperature-sensitive electrical parameters is opposite; alternatively, the junction temperature is inversely correlated to the two temperature-sensitive electrical parameters, and the same correlation variable is correlated to the two temperature-sensitive electrical parameters, i.e.:

TSEP₁＝f₁(T_j，A₁)＝a₁·T_j+b₁·A₁+c₁ (1-1)

TSEP₂＝f₂(T_j，A₁)＝a₂·T_j+b₂·A₁+c₂ (1-2)

among them, TSEP₁And TSEP₂For two thermally sensitive electrical parameters, T_jTo junction temperature, A₁The two temperature-sensitive electrical parameters are the same related variable except the junction temperature; a is₁，a₂，b₁，b₂，c₁，c₂Is a fitting coefficient; k is a radical of₁，k₂Is the ratio of the fitting coefficients.

4. The SiC MOSFET junction temperature detection method based on combined thermal electrical parameter sensitivity enhancement of claim 3, wherein: and eliminating the same related variable of the temperature-sensitive electric parameter except the junction temperature in the fitting equation to obtain a combined temperature-sensitive electric parameter, namely:

wherein TSEP is a combined thermosensitive electrical parameter;

meanwhile, the absolute value of the junction temperature coefficient of the SiC MOSFET becomes large, that is:

Technical Field

The invention belongs to the technical field of power electronics and electricians, and relates to a junction temperature detection method suitable for a SiC MOSFET.

Background

The SiC device has the advantages of high temperature, high speed and high voltage resistance, so that the efficiency and the power density of the power electronic converter are remarkably improved. However, the commercial availability of SiC devices requires the maturation of technology and the improvement of reliability to achieve a fully efficient use of its performance. Of all the faults of the converter, the fault rate of the power device is 21%, and in addition, the service life of the power device is also a key factor influencing the reliability of the converter. Excessive junction temperature or excessive fluctuations become a major source of stress and failure. Electrical aspects: higher junction temperatures will result in increased turn-on voltages and increased leakage currents, and increased power losses in both switching transients and on-state. In the aspect of thermodynamics: the maximum instantaneous junction temperature and junction temperature fluctuation caused by thermal cycling cause the increase of the thermomechanical stress, which is the main reason of causing the failure or shortening the service life of the power device

At present, junction temperature detection methods for SiC MOSFET mainly comprise invasive junction temperature detection and non-invasive junction temperature detection. The intrusive junction temperature detection method is to embed a sensor or a temperature-sensitive element into a power device to realize real-time junction temperature detection. The inherent disadvantage of this approach is that the package of the power device needs to be destroyed, reducing the device reliability, while the thermal impedance between the sensor and the die affects the detection accuracy. The non-invasive junction temperature detection method comprises a junction temperature detection method based on a Foster/Cauer thermal network model, a junction temperature solving method based on a Finite Element Method (FEM)/Finite Difference Method (FDM) and a junction temperature detection method based on a thermal-sensitive electrical parameter of a power device. The thermal network model method has the defects of complex model parameter test, aging drift and the like. The finite element method-based junction temperature calculation speed is slow, and online junction temperature detection is difficult to realize. Junction temperature detection based on a thermal-sensitive electrical parameter method obtains junction temperature at the current moment by detecting some electrical parameters related to temperature of the SiC MOSFET in real time, and has the advantages of high response speed and high precision. Therefore, the junction temperature detection method based on the thermal sensitive electrical parameters is the most suitable method for detecting the on-line junction temperature of the SiC MOSFET at present.

The selection of the SiC MOSFET thermal sensitive electrical parameters needs to comprehensively compare the linearity and the sensitivity of each thermal sensitive electrical parameter along with the change of junction temperature and the number of variables related to the thermal sensitive electrical parameter, and preferentially selects the thermal sensitive electrical parameters with good linearity, high sensitivity and less related variables except the junction temperature. However, a single temperature-sensitive electrical parameter often cannot satisfy the above three conditions at the same time, and a temperature-sensitive electrical parameter with poor linearity has the disadvantage of large detection error and even cannot be used for junction temperature detection, so that the sensitivity is low, the detection precision is reduced, and the influence factors other than the junction temperature are more, that is, the related variables in the fitting equation are more, and the calibration difficulty of a pre-curve and the real-time detection difficulty of junction temperature detection are increased.

Disclosure of Invention

In order to solve the problems, the invention provides a SiC MOSFET junction temperature detection method based on the enhancement of the sensitivity of combined thermal-sensitive electrical parameters, which can improve the sensitivity of junction temperature detection without increasing detection variables, effectively solves the problems of more influence factors except junction temperature and low sensitivity possibly existing in single thermal-sensitive electrical parameters, and improves the junction temperature detection precision of the SiC MOSFET.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a SiC MOSFET junction temperature detection method based on combined thermosensitive electrical parameter sensitivity enhancement comprises the following steps:

carrying out temperature rise test on the SiC MOSFET by adopting a control variable method;

calibrating a relation curve of the thermal sensitive electrical parameter and the related variable thereof according to the test data;

obtaining a fitting equation according to a relation curve of the thermal sensitive electrical parameter and the related variable thereof;

analyzing and comparing the correlation between the temperature-sensitive electrical parameters and related variables thereof, and eliminating the same correlation variables of the two temperature-sensitive electrical parameters except the junction temperature in a linear combination mode when two temperature-sensitive electrical parameters have linear relations with a plurality of correlation variables thereof and have the same correlation variables except the junction temperature, and the consistency of the correlation between the same correlation variables and the junction temperature on the respective temperature-sensitive electrical parameters is opposite;

and taking the thermosensitive electrical parameters after linear combination as combined thermosensitive electrical parameters.

Furthermore, the temperature-sensitive electrical parameter has a plurality of related variables including junction temperature, the relationship between the temperature-sensitive electrical parameter and the related variables is calibrated in advance through test data, and the junction temperature of the SiC MOSFET at the moment is indirectly obtained through detecting the values of the related variables in real time under specific working conditions.

Further, the consistency of the same correlation variable with the correlation of the junction temperature with the respective temperature-sensitive electrical parameter is opposite, including:

the junction temperature in the temperature-sensitive electrical parameters has consistent correlation with the two temperature-sensitive electrical parameters, and the correlation of the same correlation variable with the two temperature-sensitive electrical parameters is opposite; alternatively, the junction temperature is inversely correlated to the two temperature-sensitive electrical parameters, and the same correlation variable is correlated to the two temperature-sensitive electrical parameters, i.e.:

TSEP₁＝f₁(T_j，A₁)＝a₁·T_j+b₁·A₁+c₁ (1-1)

TSEP₂＝f₂(T_j，A₁)＝a₂·T_j+b₂·A₁+c₂ (1-2)

among them, TSEP₁And TSEP₂For two thermally sensitive electrical parameters, T_jTo junction temperature, A₁The two temperature-sensitive electrical parameters are the same related variable except the junction temperature; a is₁，a₂，b₁，b₂，c₁，c₂Is a fitting coefficient; k is a radical of₁，k₂Is the ratio of the junction temperature coefficient fitting coefficients.

Further, the same relevant variables of the temperature-sensitive electrical parameters except the junction temperature in the fitting equation are eliminated to obtain the combined temperature-sensitive electrical parameters, namely:

wherein TSEP is a combined thermosensitive electrical parameter;

meanwhile, the absolute value of the junction temperature coefficient of the SiC MOSFET becomes large, that is:

and is

Compared with the prior art, the invention has the beneficial effects that:

the invention provides a SiC MOSFET real-time junction temperature detection method, which can detect the junction temperature of the SiC MOSFET in real time, improves the detection sensitivity without increasing detection variables through the linear combination of thermosensitive electrical parameters, and finally provides more accurate junction temperature data for developing reliability research of the SiC MOSFET.

Drawings

FIG. 1(a) is a schematic diagram of the calibration of the thermosensitive electrical parameters of the SiC MOSFET in the present invention.

FIG. 1(b) is a schematic curve-fitting graph of the thermosensitive electrical parameters of the SiC MOSFET in the present invention.

FIG. 2(a) is a graph of k, the ratio of fitting coefficients when sensitivity enhancement is achieved in the present invention₁And k₂Schematic diagram of conditions to be satisfied.

FIG. 2(b) is a graph of k, the ratio of fitting coefficients when sensitivity enhancement is achieved in the present invention₁And k₂Schematic diagram of conditions to be satisfied.

FIG. 2(c) is a graph of k, the ratio of the fitting coefficients when sensitivity enhancement is achieved in the present invention₁And k₂Schematic diagram of conditions to be satisfied.

FIG. 2(d) is a plot of the ratio of fitting coefficients k for the enhanced sensitivity achieved in the present invention₁And k₂Schematic diagram of conditions to be satisfied.

Fig. 3 is a schematic diagram of real-time detection of SiC MOSFET junction temperature based on combined temperature-sensitive electrical parameters in the present invention.

Detailed Description

The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.

As shown in fig. 1(a) and 1(b), a temperature rise test is performed on the SiC MOSFET, a relationship between a temperature-sensitive electrical parameter and junction temperature and other related variables is calibrated, and a temperature-sensitive electrical parameter with a good linearity is selected and subjected to linear fitting to obtain a fitting equation. And determining the thermosensitive electrical parameters which can be linearly combined according to the related variables of the thermosensitive electrical parameters and the linear relation of the variables.

As shown in fig. 2(a), 2(b), 2(c) and 2(d), taking two thermo-sensitive electrical parameters to eliminate one of the external junction temperature related variables as an example, the fitting equation obtained by the experimental data must satisfy the following condition to combine the two thermo-sensitive electrical parameters: (1) the times of the related variables of the two thermosensitive electrical parameters are consistent; (2) the same correlation variable being cancelled is inversely correlated with the junction temperature dependence of the two temperature-sensitive electrical parameters, i.e. k₁×k₂<0. In addition, in order to achieve an increase in sensitivity,k₁and k₂The conditions to be satisfied are shown in FIG. 2, when k is₁，k₂In the common blank region belonging to fig. 2(b) and fig. 2(d), the purpose of sensitivity enhancement can be achieved, that is:

and is

As shown in fig. 3, the temperature-sensitive electrical parameter (or other independent variables except for the unremoved junction temperature) is detected in real time in the operating condition of the SiC MOSFET, the data detected in real time is transmitted to the microprocessor DSP, and the junction temperature under the corresponding temperature-sensitive electrical parameter is obtained in the microprocessor DSP according to a pre-assembly equation or a table lookup method.

Specifically, for two thermo-sensitive electrical parameters containing only two related variables and satisfying the high sensitivity combination condition, the combined equation will contain only two thermo-sensitive electrical parameters TSEP₁And TSEP₂Two temperature-sensitive electrical parameters of the SiC MOSFET during working are detected in real time, then data obtained through real-time detection are transmitted to a microprocessor DSP, and the microprocessor substitutes the obtained data into a combination equation for calculation, so that real-time junction temperature data of the SiC MOSFET can be obtained.

The working principle of the invention is as follows:

when two or more temperature-sensitive electrical parameters meet the linear combination condition, irrelevant variables outside the junction temperature in the fitting equation can be eliminated in a linear combination mode, the same relevant variable outside the junction temperature can be eliminated by two temperature-sensitive electrical parameters or the same relevant variable outside the junction temperature can be eliminated by three temperature-sensitive electrical parameters, but the condition required to be met by combination becomes more rigorous as the number of the temperature-sensitive electrical parameters is increased. The final purpose of combining the thermosensitive electrical parameters is to improve the sensitivity of junction temperature detection without increasing detection variables, so as to obtain more accurate junction temperature data of the SiC MOSFET in real time.

The invention provides a SiC MOSFET real-time junction temperature detection method, which can detect the junction temperature of the SiC MOSFET in real time, improves the detection sensitivity without increasing detection variables through the linear combination of thermosensitive electrical parameters, and finally provides more accurate junction temperature data for developing reliability research of the SiC MOSFET.

The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modifications made on the basis of the technical scheme according to the technical idea of the present invention fall within the protection scope of the present invention.