SiC power device online junction temperature estimation method

Abstract

The invention relates to the technical field of power electronics, and discloses a SiC power device online junction temperature estimation method, which comprises a storage unit used for pre-calibrating and storing a relation curve or table of temperature and on resistance Rdson when a SiC power module is offline; the Vdson sampling module is used for collecting the conduction voltage drop Vdson of the SiC power module in real time; the current sampling circuit is used for collecting current Ids flowing through a power tube of the SiC power module in real time; and the MCU is internally provided with an Rdson calculation unit and a table look-up unit, the Rdson calculation unit calculates Rdson in real time according to a formula Rdson = Vdson / Ids, and the table look-up unit matches the calculated real-time Rdson with the temperature-Rdson data pre-calibrated in the storage unit. According to the method, the limitation that a traditional direct measurement method (such as a thermocouple and a thermal imager) is only suitable for the development stage is broken through, the Rdson is calculated in real time by collecting the Vdson and the Ids, the junction temperature is looked up and matched, online real-time monitoring in the operation process is achieved, and the requirements for state evaluation and fault early warning of a power electronic system are met.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, specifically to a method for estimating the online junction temperature of SiC power devices. Background Technology

[0002] Junction temperature monitoring of silicon carbide (SiC) power modules is a crucial task, as it has a significant impact on ensuring the stability and reliability of the entire system. Junction temperature, which is the junction temperature of the semiconductor devices inside the power module, is a key indicator for measuring the operating status and performance of the devices. Since SiC power modules generate a large amount of heat during operation, if this heat cannot be effectively dissipated, it will lead to an increase in junction temperature, which will affect the performance and lifespan of the devices, and may even cause system failure.

[0003] However, the existing technology has the following problems: 1. Direct measurement methods (such as using thermocouples, thermal imagers, etc.) are only suitable for the early development stage and cannot monitor junction temperature in real time during system operation; 2. Although the thermal network model method obtains the junction temperature based on controller loss calculation and Foster thermal network model modeling, it relies on reference temperatures such as water temperature and NTC temperature inside the module, resulting in an extremely slow response and making it difficult to adapt to the fast dynamic operation scenarios of the system. 3. The direct measurement method using the internal temperature control diode of the module is highly accurate and has a fast response, but its application range is limited and it lacks versatility because power modules with temperature control diodes are not widely used. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides the following technical solution: an online junction temperature estimation method for SiC power devices, comprising a storage unit for pre-calibrating and storing a curve or table relating temperature and on-resistance Rdson when the SiC power module is off-line; a Vdson sampling module for real-time acquisition of the on-state voltage drop Vdson of the SiC power module; a current sampling circuit for real-time acquisition of the current Ids flowing through the power transistor of the SiC power module; and an MCU, which internally includes an Rdson calculation unit and a lookup table unit. The Rdson calculation unit calculates Rdson in real-time according to the formula Rdson=Vdson / Ids, and the lookup table unit matches the calculated real-time Rdson with the pre-calibrated temperature-Rdson data in the storage unit to obtain the junction temperature of the SiC power module in real time.

[0005] Preferably, the Vdson sampling module includes a SiC power module (U1), a mirror current source (constant current source 1 and constant current source 2, both with a current magnitude of I1), a turn-off current limiting resistor (R1, R2), a high-voltage diode (D1, D2), a digital isolator (U2), and a differential operational amplifier network. When U1 is turned on, the constant current source 1, R1, and D1 circuit generates a voltage Vdson1 = I1R1 + VD1 + Vdson, and the constant current source 2, R2, and D2 circuit generates a voltage Vdson2 = I1R1 + VD2. Vdson1 and Vdson2 are isolated by the digital isolator and then fed into the differential operational amplifier network. The operational amplifier amplification ratio is K = R5 / R3, and the final output Vdson sampling value is (Vdson1 - Vdson2) × K.

[0006] Preferably, when the current sampling circuit is applied to the motor controller, the real-time collected three-phase AC current is used as the current Ids flowing through the power transistor.

[0007] Preferably, a method for estimating the junction temperature of a SiC power module includes the following steps: S1: During the SiC power module rollout phase, pre-calibrate the relationship curve or table between temperature and on-resistance Rdson, and store it in the storage unit; S2: During the operation of the controller, the on-state voltage drop Vdson of the SiC power module is collected in real time using the Vdson sampling module, and the current Ids flowing through the power transistor is collected in real time using the current sampling circuit. S3: Rdson is calculated in real time by the Rdson calculation unit in the MCU according to the formula Rdson=Vdson / Ids; S4: Using the lookup table unit in the MCU, the calculated real-time Rdson is matched with the pre-calibrated temperature-Rdson data in the storage unit to obtain the junction temperature of the SiC power module in real time.

[0008] Preferably, the sampling process of the Vdson sampling module in step S2 is as follows: when the SiC power module (U1) is turned on, the constant current source 1, R1, D1 circuit generates voltage Vdson1=I1R1+VD1+Vdson, and the constant current source 2, R2, D2 circuit generates voltage Vdson2=I1R1+VD2. Vdson1 and Vdson2 are isolated by a digital isolator and then sent to a differential operational amplifier network. After being processed by an operational amplifier with an amplification ratio of K=R5 / R3, the output Vdson sampling value is (Vdson1-Vdson2)×K.

[0009] Preferably, in step S2, in the application scenario of a motor controller, the three-phase AC current collected in real time by the current sampling circuit is used as the current Ids flowing through the power transistor. Beneficial effects

[0010] Compared with existing technologies, this invention provides an online junction temperature estimation method for SiC power devices, which has the following advantages: 1. Breaking through the limitation of traditional direct measurement methods (such as thermocouples and thermal imagers) being only applicable to the development stage, this method collects Vdson and Ids to calculate Rdson in real time and matches the junction temperature by looking up a table, thereby realizing online real-time monitoring during operation and meeting the needs of power electronic system status assessment and fault early warning.

[0011] 2. Compared with the thermal network model method, which relies on a reference temperature (such as water temperature or NTC temperature) and suffers from slow response, this invention directly calculates the correlation between Rdson and junction temperature, without the need for an additional reference temperature. It has a fast response speed and can promptly reflect junction temperature changes under dynamic operating scenarios (such as sudden load changes or frequent start-stop).

[0012] 3. It does not depend on specific module structures (such as temperature control diodes) and is applicable to mainstream ordinary SiC power modules on the market. It solves the application limitations of temperature control diode-based solutions and has wider applicability and compatibility.

[0013] 4. No additional temperature control diodes or complex thermal network model parameter identification processes are required. This can be achieved using existing hardware (Vdson sampling circuit, current sampling circuit) combined with software algorithms, which reduces system cost and design complexity.

[0014] 5. By designing a differential operational amplifier network (Vdson=(Vdson1-Vdson2)×K), common-mode interference can be effectively eliminated. Combined with a pre-calibrated temperature-Rdson relationship curve, high-precision junction temperature estimation can be achieved, with performance close to or even surpassing the direct measurement method based on temperature-controlled diodes in some scenarios.

[0015] 6. Real-time junction temperature feedback provides accurate information for power module thermal management strategies (such as derating control and fault protection), avoiding the risk of module failure due to overheating and significantly improving the reliability and stability of power electronic systems.

[0016] 7. It can be applied to the entire life cycle of SiC power modules, from R&D testing to actual operation, supporting both early characteristic calibration and long-term operation monitoring needs, achieving seamless integration of technical solutions and continuous value creation. Attached Figure Description

[0017] Figure 1 This is a block diagram of the overall method for estimating the Rdson junction temperature of SiC power devices based on SiC conduction, as proposed in this invention. Figure 2 The Rdson spectral density and temperature curves of the online junction temperature estimation method for SiC power devices proposed in this invention are shown. Figure 3 This invention relates to an Rdson sampling circuit for an online junction temperature estimation method for SiC power devices. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figures 1-3 A method for estimating the junction temperature of SiC power devices online includes: a storage unit for pre-calibrating and storing a curve or table showing the relationship between temperature and on-resistance Rdson when the SiC power module is off-line; a Vdson sampling module for real-time acquisition of the on-state voltage drop Vdson of the SiC power module; a current sampling circuit for real-time acquisition of the current Ids flowing through the power transistor of the SiC power module; and an MCU, which internally includes an Rdson calculation unit and a lookup table unit. The Rdson calculation unit calculates Rdson in real-time according to the formula Rdson=Vdson / Ids, and the lookup table unit matches the calculated real-time Rdson with the pre-calibrated temperature-Rdson data in the storage unit to obtain the junction temperature of the SiC power module in real time.

[0020] In this embodiment, the present invention cleverly utilizes the positive correlation between the on-resistance (Rdson) and junction temperature of the SiC power module within a specific temperature range (-40℃ to 175℃) to achieve accurate online estimation of the module's junction temperature. The specific implementation process is as follows: First, when the module is offline, precise calibration is performed in advance to determine the relationship curve or detailed table between temperature and Rdson, and this calibration data is stored in a dedicated storage unit for later retrieval. During controller operation, the on-state voltage drop (Vdson) of the SiC power module is collected in real time through the Vdson sampling module, and the current flowing through the power transistor (Ids) is collected in real time through a high-precision current sampling circuit. The Rdson calculation unit in the MCU calculates the current Rdson value in real time according to the formula Rdson = Vdson / Ids. Subsequently, the lookup unit precisely matches the calculated real-time Rdson with the pre-calibrated temperature-Rdson data in the storage unit, thereby obtaining the junction temperature of the SiC power module in real time and ensuring the stability and reliability of the system operation. Vdson sampling principle: The circuit includes a SiC power module (U1), mirror current sources (constant current source 1 and constant current source 2, both with a current magnitude of I1), turn-off current-limiting resistors (R1, R2), high-voltage diodes (D1, D2), a digital isolator (U2), and a differential operational amplifier network. When U1 is turned on, the constant current source 1, R1, D1 circuit and the constant current source 2, R2, D2 circuit generate voltages Vdson1 and Vdson2 respectively, where Vdson1 = I1R1 + VD1 + Vdson, and Vdson2 = ... I1R1+VD2, after being isolated by a digital isolator, are fed into a differential operational amplifier network. The operational amplifier amplification ratio is K=R5 / R3, and the final output Vdson=(Vdson1-Vdson2)×K=Vdson×K, realizing accurate sampling of the on-state voltage drop; Current sampling principle: Taking the motor controller as an example, the three-phase AC current is collected in real time. This current is the current flowing through the power transistor (Ids), which is an important parameter for calculating Rdson. The specific sampling principle of Vdson is as follows: The sampling circuit mainly consists of a SiC power module (U1), a mirror current source (including constant current source 1 and constant current source 2, both with a current magnitude of I1), a turn-off current limiting resistor (R1, R2), a high-voltage diode (D1, D2), a digital isolator (U2), and a differential operational amplifier network. When U1 is turned on, the constant current source 1, R1, D1 circuit and the constant current source 2, R2, D2 circuit generate voltages Vdson1 and Vdson2 respectively. Vdson1 is calculated as I1R1 + VD1 + Vdson, and Vdson2 is calculated as I1R1 + VD2. These two voltage signals are effectively isolated by a digital isolator before being sent to a differential operational amplifier network for processing.The operational amplifier network has an amplification ratio of K = R5 / R3, and the final output Vdson = (Vdson1 - Vdson2) × K = Vdson × K, thus achieving accurate sampling of the on-state voltage drop. The current sampling principle is explained using a motor controller as an example: the system collects the three-phase AC current in real time, which is the current flowing through the power transistor (Ids), a crucial parameter for calculating the Rdson value. By accurately collecting and processing this current data, the accuracy of the Rdson calculation is ensured, thereby improving the accuracy and reliability of junction temperature estimation.

[0021] Working principle: This invention utilizes the positive correlation between the on-resistance (Rdson) and junction temperature of a SiC power module within a specific temperature range (-40~175℃) to estimate the module's junction temperature online. The specific process is as follows: When the module is offline, a temperature-Rdson relationship curve or table is pre-calibrated and stored in a storage unit; during controller operation, the on-state voltage drop (Vdson) of the SiC power module is collected in real time through the Vdson sampling module, and the current flowing through the power transistor (Ids) is collected in real time through the current sampling circuit; the Rdson calculation unit in the MCU calculates Rdson in real time according to the formula Rdson=Vdson / Ids; the table lookup unit matches the calculated real-time Rdson with the pre-calibrated temperature-Rdson data in the storage unit, thereby obtaining the junction temperature of the SiC power module in real time.

[0022] Vdson sampling principle: The circuit includes a SiC power module (U1), current mirrors (constant current source 1 and constant current source 2, both with a current magnitude of I1), turn-off current-limiting resistors (R1, R2), high-voltage diodes (D1, D2), a digital isolator (U2), and a differential operational amplifier network. When U1 is turned on, the constant current source 1, R1, D1 circuit and the constant current source 2, R2, D2 circuit generate voltages Vdson1 and Vdson2 respectively, where Vdson1 = I1R1 + VD1 + ... Vdson and Vdson2 = I1R1 + VD2 are isolated by a digital isolator and then fed into a differential operational amplifier network. The operational amplifier amplification ratio is K = R5 / R3, and the final output Vdson = (Vdson1 - Vdson2) × K = Vdson × K, realizing accurate sampling of the on-state voltage drop. Current sampling principle: Taking the motor controller as an example, the three-phase AC current is collected in real time. This current is the current (Ids) flowing through the power transistor, which is an important parameter for calculating Rdson.

[0023] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A method for estimating the junction temperature of SiC power devices online, characterized in that, include: The storage unit is used to pre-calibrate and store the relationship curve or table between temperature and on-resistance Rdson when the SiC power module is off the production line; The Vdson sampling module is used to collect the on-state voltage drop Vdson of the SiC power module in real time. The current sampling circuit is used to collect the current Ids flowing through the power transistor of the SiC power module in real time. The MCU has an internal Rdson calculation unit and a lookup table unit. The Rdson calculation unit calculates Rdson in real time according to the formula Rdson = Vdson / Ids. The lookup table unit matches the calculated real-time Rdson with the pre-calibrated temperature-Rdson data in the storage unit to obtain the junction temperature of the SiC power module in real time.

2. The method for estimating the online junction temperature of a SiC power device according to claim 1, characterized in that: The Vdson sampling module includes a SiC power module (U1), a mirror current source (constant current source 1 and constant current source 2, both with a current magnitude of I1), a turn-off current limiting resistor (R1, R2), high-voltage diodes (D1, D2), a digital isolator (U2), and a differential operational amplifier network. When U1 is turned on, the constant current source 1, R1, and D1 circuit generates a voltage Vdson1 = I1R1 + VD1 + Vdson, and the constant current source 2, R2, and D2 circuit generates a voltage Vdson2 = I1R1 + VD2. Vdson1 and Vdson2 are isolated by the digital isolator and then fed into the differential operational amplifier network. The operational amplifier amplification ratio is K = R5 / R3, and the final output Vdson sampling value is (Vdson1 - Vdson2) × K.

3. The method for estimating the online junction temperature of a SiC power device according to claim 1, characterized in that: When the current sampling circuit is applied to the motor controller, the real-time collected three-phase AC current is used as the current Ids flowing through the power transistor.

4. A method for estimating the junction temperature of a SiC power module, characterized in that, Includes the following steps: S1: During the SiC power module rollout phase, pre-calibrate the relationship curve or table between temperature and on-resistance Rdson, and store it in the storage unit; S2: During the operation of the controller, the on-state voltage drop Vdson of the SiC power module is collected in real time using the Vdson sampling module, and the current Ids flowing through the power transistor is collected in real time using the current sampling circuit. S3: Rdson is calculated in real time by the Rdson calculation unit in the MCU according to the formula Rdson=Vdson / Ids; S4: Using the lookup table unit in the MCU, the calculated real-time Rdson is matched with the pre-calibrated temperature-Rdson data in the storage unit to obtain the junction temperature of the SiC power module in real time.

5. The method for estimating the online junction temperature of a SiC power device according to claim 4, characterized in that: The sampling process of the Vdson sampling module in step S2 is as follows: When the SiC power module (U1) is turned on, the constant current source 1, R1, D1 circuit generates a voltage Vdson1 = I1R1 + VD1 + Vdson, and the constant current source 2, R2, D2 circuit generates a voltage Vdson2 = I1R1 + VD2. Vdson1 and Vdson2 are isolated by a digital isolator and then sent to a differential operational amplifier network. After being processed by an operational amplifier with an amplification ratio of K = R5 / R3, the output Vdson sampling value is (Vdson1 - Vdson2) × K.

6. The method for estimating the online junction temperature of a SiC power device according to claim 4, characterized in that: In step S2, in the application scenario of a motor controller, the three-phase AC current collected in real time by the current sampling circuit is used as the current Ids flowing through the power transistor.

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