Global monitoring method for junction temperature of motor-driven power device in robot joint module

Abstract

The invention discloses a global monitoring method for the junction temperature of a motor-driven power device in a robot joint module, and belongs to the technical field of thermal management of power electronic devices. On-resistance is calculated by collecting the on-voltage drop and the on-current of a lower bridge arm MOSFET on line, and the junction temperature of a lower tube is estimated in real time in combination with the calibrated linear relation; the NTC temperature data and the thermal coupling model are fused, the upper tube junction temperature is predicted, and global monitoring of the full-bridge inverter power device is achieved. In hardware, a three-phase current sampling ADC channel is multiplexed, and a voltage drop acquisition circuit containing a clamping-compensating diode is adopted to solve the problem of high voltage measurement. Experiments show that the junction temperature monitoring error of the method is less than or equal to + / -2 DEG C, the response time is less than 10ms, an additional sensor is not needed, and the system reliability and the thermal management efficiency are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal management of power electronic devices, and relates to a method and system for global monitoring of the junction temperature of motor-driven power devices in a robot joint module. Specifically, it relates to a method and system for global monitoring of the junction temperature of power devices based on on-resistance, which is suitable for thermal status monitoring of high-power density motor drives. Background Art

[0002] Motor drivers are composed of a variety of components, including MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), chips, and diodes. As robot motor drivers become increasingly integrated and power-dense, thermal management becomes increasingly challenging. Moore's Law states that the number of transistors that can be accommodated on an integrated circuit doubles every 18 months. This increase in component density results in a continuous reduction in the space occupied by individual components, a gradual reduction in the physical size of chips, and a continuous increase in circuit integration. As components continue to become thinner and more powerful, PCB layout and routing become increasingly complex. Furthermore, to meet high-performance demands, chip operating frequencies continue to increase. These factors significantly increase heat generation per unit volume, leading to a continuous increase in the heat flux generated during motor driver operation, which can cause device overheating.

[0003] Electronic components are extremely sensitive to temperature, and high temperatures can negatively impact their performance. Furthermore, continued temperature increases can lead to significant thermal stress and thermal expansion of materials, potentially damaging components and potentially irreversibly harming chips. According to the Arrhenius equation, component lifespan is halved for every 10°C increase in ambient temperature, a phenomenon known as the "10°C rule."

[0004] Junction temperature is the highest temperature of the actual semiconductor chip (wafer, bare die) in the electronic device. It is usually higher than the case temperature and the surface temperature of the device. Junction temperature can measure the time required for heat dissipation from the semiconductor wafer to the packaged device case and the thermal resistance. It is a key indicator for measuring the working state and health of power devices. Therefore, monitoring junction temperature ( T j) is crucial for improving system performance and reliability. Real-time junction temperature monitoring during driver operation provides data support for improving system reliability, optimizing power density, and managing available capacity. It also serves as the technical foundation for device lifespan prediction and health management. Traditional junction temperature measurement methods primarily include physical contact, optical, electrothermal coupling, and Temperature Sensitive Electrical Parameter (TSEP).

[0005] (1) Physical contact measurement method The physical contact measurement method is the most direct and convenient, but it requires intrusion into the device package, removal of the thermal silicone on the chip, and installation of a thermistor inside the power module to directly measure internal temperature information. Thermistors are made of semiconductor materials, and their resistance changes with temperature. Thermocouple temperature measurement is based on the thermoelectric effect, consisting of two different conductors forming a closed circuit. When a temperature difference exists between the two ends of the thermocouple, the circuit generates a thermoelectric electromotive force, which is measured to obtain the corresponding temperature information. Although the physical contact method is simple, its measurement accuracy is low, it is time-consuming, and it requires strict placement of the thermistor, making it less practical and difficult to use.

[0006] (2) Optical method The optical method uses infrared detection and optical imaging technology to receive infrared radiation energy emitted by the power device under test and convert it into an infrared thermal image. While accurate, this method requires invasive access to the device, opening the device package, and removing the thermal insulation silicone to achieve optical contact. Furthermore, optical junction temperature measurement requires expensive test equipment, making it unsuitable for online, real-time junction temperature estimation.

[0007] (3) Electrothermal coupling model method The electrothermal coupling model is a non-invasive measurement method. Its advantage lies in the lack of direct contact with the device, making the testing method relatively simple. This method calculates the device's junction temperature based on heat loss and a thermal impedance network model. The measurement process uses an equivalent thermal path model to describe the thermal characteristics, typically employing an RC thermal impedance network for modeling and optimization. The literature (Cui H, Hu F, Zhang Y, et al. Heat spreading path optimization of IGBT thermal network model[J]. Microelectronics reliability, 2019, 103: 113511.) regulates the thermal resistance and thermal capacitance parameters by adjusting the heat spreading angles of each material layer. The Caure model also incorporates the interaction between heat conduction and convection, fully accounting for the influence of the baseplate's heat dissipation. This refines the heat transfer path and makes the model more accurate than the traditional Caure model. Reference (Sang Yalei. Research on Fatigue Life and Thermal Stress Reproduction of Power Devices in Electric Vehicle Converters [D]. Guangzhou: South China University of Technology, 2019.) established a coupled thermal network for a multi-chip package module based on transient thermal impedance response and quantified the service life of power devices under actual operating conditions. Reference (Wang Zhaoping, Xin Jinlei, Du Mingxing. Construction of a Hybrid Thermal Network Model and Its Junction Temperature Estimation Method [J]. Journal of Power Supply, 2024, 22(03): 30-37.) Combining the advantages of the two traditional thermal network models of Cauer and Foster, their interface methods were studied and integrated, and the aging effect of the chip solder layer was considered. An improved hybrid thermal network model was proposed. Reference (Sun Xiepeng, Du Mingxing, Hu Jingwei. IGBT module junction temperature estimation and aging monitoring method based on transfer function [J]. Journal of Tianjin University of Technology, 2025, 41 (01): 36-43.) Taking the third-order Cauer model as an example, a method of extracting thermal network model parameters based on the base plate temperature transfer function was studied to achieve accurate junction temperature estimation.

[0008] However, the establishment of relevant thermal network models is often extremely dependent on the actual physical size and material parameters of the chip, and in most applications, it is difficult to obtain relevant material and size data. Based on this, the literature (Liu Ping, Li Haipeng, Miao Yiru, et al. Online extraction method of junction temperature of silicon carbide power module based on built-in temperature sensor [J]. Transactions of the Chinese Society of Electrotechnical Engineering, 2021, 36 (12): 2522-2534.) proposed an online extraction method of junction temperature based on a built-in negative temperature coefficient (NTC) temperature sensor, established a thermal network model of multi-chip thermal coupling, extracted thermal network impedance parameters through finite element simulation, and verified its stability under different boundary conditions. However, the use of built-in NTC temperature sensors will increase the manufacturing complexity and cost of power modules, and may also affect the monitoring results due to sensor accuracy and long-term reliability issues.

[0009] (4) Thermistor electrical parameter method Compared to other junction temperature monitoring methods, the TSEP method uses the chip itself as a temperature sensor, enabling non-invasive measurement and making it ideal for online monitoring of chip junction temperature. TSEP methods can be categorized into different types based on their sensitive parameters. Their core principle is to estimate the junction temperature of a semiconductor device by leveraging the temperature-dependent behavior of certain electrical parameters.

[0010] In power electronic devices, the short-circuit current of switching devices usually shows a good linear relationship with the junction temperature. However, fatigue damage and aging of the bonding wires inside the chip will reduce the short-circuit current test results. Therefore, the paper (Yang Shumeng, Sun Pengju, Du Xiong, et al. A method for measuring the junction temperature of IGBT modules based on combined short-circuit current and not affected by aging [J]. Proceedings of the CSEE, 2020, 40(18): 5770-5779) proposes a junction temperature monitoring method for IGBT modules based on combined short-circuit current. By analyzing and simulating wire-cutting experiments, the influence of aging on the junction temperature measurement method is studied, and the feasibility of online monitoring of the method in the converter is verified based on an experimental platform. Based on theoretical analysis and experimental results, it is found that this method can not only eliminate the influence of bonding wire aging on junction temperature measurement, but also has good linearity, high sensitivity and online monitoring capabilities. However, in practical applications, this method requires the design of specific dual-level special drive circuits for different switching modules, which increases the difficulty of hardware implementation and limits its wide application in engineering.

[0011] In addition, although the threshold voltage in the temperature-sensitive parameter ( V th ) has good temperature sensitivity, but direct measurement is easily affected by current oscillation. Therefore, the literature (Guan Wei, Dong Lei. Threshold voltage junction temperature estimation method based on IGBT Miller platform [J]. Electric Drive, 2024, 54 (06): 22-28.) proposed an indirect calculation method. Vth The method is to indirectly calculate the switching transient process by observing the Miller platform voltage value. V th Furthermore, the literature (Zhang Qinghao, Zhang Pinjia. An online monitoring method for SiC MOSFET junction temperature based on gate voltage threshold detection [J]. Proceedings of the CSEE, 2020, 40 (18): 5742-5751.) proposed a method based on V th A new junction temperature monitoring method based on detection is used to deduce the relationship between junction temperature and V th The linear relationship between them is proposed, and a polynomial fitting method is proposed. V th However, this method requires an accurate description of the device switching transient process, involves complex mathematical models, and its accuracy is easily affected by noise and electromagnetic interference. Furthermore, in practical applications, accurate measurement and calculation of the Miller plateau voltage requires specialized test circuits and related equipment, which increases the difficulty and cost of application.

[0012] In addition to the threshold voltage ( V th ), the on-state voltage drop of the power device is also an important thermally sensitive electrical parameter, and its value will also change with the junction temperature, so it can also be used to estimate the junction temperature. In practical applications, other electrical parameters closely related to junction temperature, such as turn-off voltage overshoot and turn-on transient current overshoot, can also be used as thermally sensitive parameters to estimate the junction temperature. It should be noted that although the TSEP method is simple, fast, and can achieve non-invasive measurement, its estimation accuracy is easily affected by factors such as measurement error and device aging. In addition, due to hardware resource limitations, the TSEP method is usually only applicable to estimating the junction temperature of a single power device, which is difficult to meet the actual needs of complex systems such as motor drives. Therefore, when applying the TSEP method for junction temperature estimation, it is necessary to fully consider the relevant influencing factors and take corresponding optimization measures to improve the applicability and reliability of the monitoring method. Summary of the Invention

[0013] The purpose of the present invention is to provide a global monitoring method for the junction temperature of motor-driven power devices in a robot joint module. By online extracting the MOSFET on-resistance variation characteristics and combining data-driven thermal coupling modeling, the junction temperature of the global device can be estimated. Compared with traditional methods, this method has higher real-time performance and integrability, and can adapt to changes in thermal characteristics under different working conditions. The purpose of the present invention is achieved through the following specific technical solutions.

[0014] A global monitoring method for junction temperature of a power device driven by a motor in a robot joint module includes the following steps: S1 collects the on-state voltage drop and on-state current of the MOSFET in the lower bridge arm of the three-phase inverter in real time; S2 calculates the real-time on-resistance of the lower bridge arm MOSFET by the ratio of the on-state voltage drop to the on-state current; S3 establishes a linear calibration model of on-resistance and junction temperature, and calculates the real-time junction temperature of the lower bridge arm MOSFET based on the real-time on-resistance; S4 uses the junction temperature data of the low-side MOSFET and the measurement data of the negative temperature coefficient (NTC) temperature sensor to build a thermal coupling model to predict the junction temperature of the high-side MOSFET, realizing global monitoring of the junction temperature of power devices in the motor drive.

[0015] The present invention provides a global monitoring method for the junction temperature of motor-driven power devices in a robot joint module. This method can achieve global monitoring of the junction temperature of motor driver power devices without adding additional sensors, with the error controlled within ±2°C.

[0016] Furthermore, online on-resistance extraction reuses the ADC (Analog-Digital Converter) channels used for three-phase current sampling, synchronously acquiring current and voltage drop data through a time-sharing sampling strategy. This reuse of ADC channels saves hardware resources and avoids the need for dedicated sampling circuits.

[0017] Furthermore, a low-end three-resistor sampling circuit is used to measure the three-phase current and collect the on-state voltage drop during the MOSFET conduction window, solving the high-voltage upper-arm measurement challenge and improving sampling safety. Furthermore, the on-state voltage drop acquisition circuit includes a bias current source, clamping diode D1, and compensation diode D2. D1 isolates the busbar high voltage, while D2 compensates for D1's measurement errors, enabling high-precision measurement of tiny voltage drops (mV level).

[0018] Furthermore, the linear calibration model in step S3 is established through calibration experiments, and the operating temperature range is 0° C. to 150° C. This linear calibration model is suitable for medium and high voltage MOSFETs and has a high temperature sensitivity coefficient stability.

[0019] Furthermore, the thermal coupling model in step S4 is generated through data-driven training, with the input being the lower tube junction temperature, the measurement data of the NTC temperature sensor and the load condition, and the output being the predicted value of the upper tube junction temperature.

[0020] The present invention also provides a junction temperature monitoring system that implements the aforementioned global monitoring method. The system comprises: a main control chip; a three-phase current sampling circuit that reuses ADC channels; a forward voltage drop acquisition circuit including clamping and compensation diodes; an NTC temperature sensor; and a thermal coupling model processing module. The junction temperature monitoring system provided by the present invention has low hardware cost and is easily integrated into existing motor drives.

[0021] Furthermore, the main control chip implements a time-sharing sampling algorithm. Within a PWM cycle, it prioritizes collecting three-phase current data for FOC control and switches to sampling the on-state voltage drop during the conduction window, ensuring real-time control and synchronization with temperature monitoring.

[0022] Furthermore, the NTC temperature sensor is mounted on the power module substrate to monitor the changes in heat distribution in real time and enhance the dynamic response capability of the thermal coupling model.

[0023] The present invention also provides a motor driver, characterized by integrating the aforementioned junction temperature monitoring system. The driver can include built-in junction temperature protection logic. Based on the monitoring results of the junction temperature monitoring system, the driver triggers frequency reduction or shutdown when the junction temperature exceeds a threshold, thereby preventing overheating damage and improving system reliability.

[0024] The present invention has the following beneficial technical effects: the junction temperature monitoring method and system provided by the present invention not only have high precision and stability, but also exhibit good dynamic response capabilities. Compared with the traditional junction temperature measurement method, this method combines the actual on-resistance circuit measurement with the data-driven model, and can obtain the junction temperature distribution information of the global power device in real time, effectively eliminating the limitations of traditional single-point temperature measurement, avoiding the blind spot problem in junction temperature monitoring, and thus significantly improving the reliability of monitoring. Experimental results show that the deviation between the junction temperature monitoring value and the actual temperature under different load conditions of this method is always controlled within ±2°C, which can reliably reflect the thermal state of MOSFET in a complex working environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the cell structure of power MOSFET.

[0026] Figure 2 It is the relationship between junction temperature, conduction voltage drop and current.

[0027] Figure 3 It is the relationship between junction temperature and on-resistance.

[0028] Figure 4 This is the principle diagram of collecting the conduction voltage drop of a three-phase inverter.

[0029] Figure 5 It is a three-phase current and conduction voltage drop sampling process within a sampling period.

[0030] Figure 6 This is the block diagram of the motor driver hardware design in the robot joint module.

[0031] Figure 7 This is the front view of the motor driver in the robot joint module.

[0032] Figure 8 This is the reverse side of the motor driver in the robot joint module.

[0033] Figure 9 It is the junction temperature monitoring result under no-load condition.

[0034] Figure 10 It is the junction temperature monitoring result under 50% rated load condition.

[0035] Figure 11 It is the junction temperature monitoring result under 100% rated load condition.

[0036] Figure 12 It is the junction temperature monitoring result under sudden load condition.

[0037] Figure 13 It is the junction temperature monitoring result of sudden load reduction condition. DETAILED DESCRIPTION

[0038] The following is a clear and complete description of the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0039] In the description of the present invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate description and simplify the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance, quantity, or position.

[0040] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0041] The cell structure of power MOSFET is as follows: Figure 1When the MOSFET is turned on, electrons start from the source (S) electrode, flow through the P-type base region, channel, JFET region, N drift region and substrate in sequence, and finally reach the drain (D) electrode. At this time, the MOSFET behaves as a resistor.

[0042] MOSFET on-resistance R ds(on) It is mainly composed of the following parts: leakage contact resistance R CD 、N + Substrate resistance R Sub , drift layer resistance R Drift , JFET region resistance R JFET , accumulation layer resistance R A , channel resistance R CH , source resistance R n+ and source contact resistance R CS , among which the on-resistance is mainly composed of channel resistance R CH , accumulation layer resistance R A and drift layer resistance R Drift Dominant, can be expressed as:

[0043] Where, K A for current injection from the accumulation layer into the JFET region; W G is the gate width; χ JP is the junction depth of the P region; u nA is the electron mobility of the accumulation layer; p D is the resistivity of the drift region; W cell is the cell width; a is the width of the drift region current cross section; t is the width of the drift region. u nA and p D will increase with increasing temperature, and V th As the temperature rises, it decreases. From formulas (2-1) and (2-3), we can see that R CH Has a negative temperature sensitivity coefficient, and RDrift Has a positive temperature coefficient. For medium and high voltage MOSFETs, within the operating temperature range of 0°C to 150°C, R ds(on) Mainly affected by the resistance of the drift region, it shows a positive temperature sensitivity coefficient and can be approximately regarded as R ds(on) There is a linear positive correlation between temperature and humidity.

[0044] like Figure 2 As shown in Figure 1, it is the three-dimensional relationship between junction temperature and on-state voltage drop and current. By simplifying the process, it is converted into a two-dimensional relationship between junction temperature and on-state resistance. Figure 3 As shown, there is a clear linear correlation between junction temperature and on-resistance. Measuring on-resistance accurately measures junction temperature, providing effective technical support for junction temperature monitoring and management. This is particularly applicable to thermal management systems that lack direct temperature measurement methods.

[0045] R ds(on) The online extraction can be achieved by the power MOSFET conduction voltage drop V ds(on) and conduction current I ds(on) The ratio can be expressed as:

[0046] Generally speaking, MOSFET has a higher switching frequency and shorter on-time than IGBT and other devices, so during the on-time I ds(on) Not much change, R ds(on) Online extraction of V ds(on) and I ds(on) The sampling synchronization requirements are low. At the same time, compared with the transient process of the switch, the conduction time is relatively long. V ds(on) and I ds(on) The online extraction does not require high time resolution.

[0047] The vector control system of the PMSM motor samples and transforms the three-phase current, and compares it with the reference current to achieve closed-loop control. The system uses resistor sampling to detect current, and this method is also applicable to I ds(on) measurement.

[0048] The present invention integrates the on-state voltage drop sampling in the system and reuses the ADC sampling channel with the three-phase current sampling. Taking into account the hardware resources, sampling accuracy and time window limitations, the present invention adopts the low-end three-resistance sampling method to measure the three-phase current. Since the on-state voltage drop of MOSFET is extremely small and difficult to measure directly, such as Figure 4 The circuit shown provides a relatively simple and effective test solution. It isolates the drain-source voltage when the MOSFET is off and measures it when the MOSFET is on. The measurement circuit consists of a bias current source and series-connected diodes D1 and D2. The current source provides a stable current to ensure forward conduction of the diodes. Diode D1 clamps the voltage, isolating the high voltage busbar and preventing damage to downstream circuits due to overvoltage. Diode D2 compensates for measurement errors introduced by D1, improving measurement accuracy and precision.

[0049] The on-resistance of the MOSFETs in a three-phase inverter can be calculated by separately measuring their on-current and voltage drop. However, this method is primarily applicable to measuring the lower-side MOSFETs, while the junction temperature of the upper-side MOSFETs is difficult to obtain. Relying solely on traditional on-resistance-based junction temperature measurement methods makes it difficult to achieve global monitoring of the power devices in the entire inverter system.

[0050] To address this technical challenge, the present invention combines historical temperature data from multiple power devices with measurement results from negative temperature coefficient (NTC) resistors (i.e., NTC temperature sensors). This method fully exploits the thermal coupling relationship and can predict the junction temperature of the upper MOSFET by directly measuring the temperature data of the lower MOSFET and the NTC resistor, thereby achieving comprehensive monitoring of the entire power module. Due to the thermal coupling effect between MOSFETs, the temperature of the lower MOSFET not only directly affects the junction temperature of the upper MOSFET but also changes the thermal distribution of the entire inverter. The NTC resistor, with its negative temperature coefficient characteristic, can quickly respond to temperature changes, accurately capturing temperature changes in power devices and playing a key role in MOSFET junction temperature monitoring. By combining historical experimental data, a mathematical model can be established between the upper MOSFET junction temperature, the lower MOSFET temperature, and the NTC resistor data, enabling real-time monitoring of global power device junction temperature and timely detection of potential overtemperature issues.

[0051] The junction temperature monitoring control algorithm calculates the on-resistance based on real-time measurements of the MOSFET's on-state voltage drop and current, thereby estimating the junction temperature. To minimize hardware costs and implement this function within a single MCU, a multiplexed analog-to-digital converter (ADC_123) is used to multiplex the three-phase on-state voltage drop and current sampling. This effectively calculates the on-resistance and estimates the MOSFET's junction temperature, ensuring the accuracy of the overall sampling circuit and its real-time feedback capabilities.

[0052] like Figure 5 The figure shows the three-phase current and on-state voltage drop sampling process within a sampling cycle. First, by setting Sample_Flag = 1, three-phase current data is prioritized, achieving a key parameter for efficient FOC control. After current sampling is complete, the system resets the sampling flag to Sample_Flag = 0 and begins collecting on-state voltage drop data. Through a series of signal processing steps, including compensation, isolation, amplification and conditioning, and noise filtering, the processed sampled data is transmitted to the MCU. Based on an established linear model of on-state resistance and junction temperature, the sampled data is used for real-time MOSFET temperature monitoring. Global junction temperature monitoring is also performed based on the aforementioned thermal coupling model. In this sampling algorithm, the collection and processing of current and on-state voltage drop data are tightly integrated, ensuring accurate motor control while also providing reliable data support for MOSFET temperature monitoring. This is key to achieving efficient motor control and effective MOSFET temperature monitoring.

[0053] The overall hardware design structure of the motor driver in the robot joint module is as follows: Figure 6 As shown, the core component is a minimum system built around the STM32F446RET6 main control chip, which is responsible for central control of the entire drive system. The driver also includes gate drivers, a three-phase inverter power module, a communication module, a position sensor, a sampling circuit, and corresponding protection circuits. The pulse-width modulation (PWM) signal generated by the main control chip is amplified by the driver circuit to effectively control the switching transistors in the power module. The power module obtains three-phase current data through current sampling and, combined with the Field-Oriented Control (FOC) algorithm, adjusts the PWM signal output for precise motor control. The encoder collects and monitors the motor's position in real time, transmitting it back to the main control chip via the RS-485 communication interface for processing. The main control chip then uses this data to calculate and adjust the motor's speed and torque in real time to adapt to varying loads and operating conditions.

[0054] The motor driver in the robot joint module provided by the present invention is as follows Figure 7 and Figure 8 The figure shows a high-performance MOSFET driver. This driver features a wide operating voltage range and excellent heat dissipation performance. It also has a built-in monitoring function that can monitor voltage, current, and key parameters such as junction temperature in real time to prevent overheating and overload, ensuring long-term stable operation of the motor driver and improving the stability of the entire system.

[0055] In order to fully simulate the various load conditions that MOSFET may encounter in actual applications, a variety of different working conditions are designed to carry out experiments to monitor the junction temperature of the motor driver power device. By making the motor driver operate under different load conditions, including constant working conditions from low to high, and sudden increase and decrease of load, the working conditions that may be encountered in actual applications are simulated to verify the applicability of the proposed method. The core purpose of the experiment is to verify whether the junction temperature data obtained by the junction temperature monitoring method based on on-resistance of the present invention is consistent with the actual junction temperature data. The junction temperature data obtained by the junction temperature monitoring method provided by the present invention is compared with the maximum junction temperature data of 6 MOSFET tubes obtained directly by thermocouple measurement to evaluate the accuracy and reliability of the improved junction temperature monitoring method.

[0056] The experiments were conducted under different working conditions, namely no load, 50% and 100% rated load. The experimental results show that as the power load gradually increases, the steady-state junction temperature of MOSFET shows a significant upward trend. Figures 9 to 11 As shown in the figure, under different load conditions, the junction temperature monitoring results are highly consistent with the actual junction temperature change curve, and the error of the estimated junction temperature is always controlled within ±2°C, indicating that the junction temperature monitoring method provided by the present invention can effectively reflect the actual junction temperature of the MOSFET.

[0057] Two different working conditions, sudden increase and sudden decrease of load, were set for the experiment. Figure 12 、 Figure 13 Experimental results show that under conditions of sudden load increases and decreases, the junction temperature monitoring value can accurately track actual junction temperature changes and respond quickly to the instantaneous load change. By comparing MOSFET junction temperature fluctuations in real time, the applicability and high accuracy of this junction temperature monitoring method under dynamic load conditions are verified, ensuring that the junction temperature monitoring results are not distorted under different operating conditions.

[0058] Although the embodiments of the present invention have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art may make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention. The scope of protection of the present invention is defined by the claims and their equivalents.

Claims

1. A global monitoring method for junction temperature of power devices driven by motors in robot joint modules, characterized in that: The following steps are involved: S1 collects the on-state voltage drop and on-state current of the MOSFET of the lower bridge arm of the three-phase inverter in real time; S2 calculates the real-time on-resistance of the lower bridge arm MOSFET by the ratio of the on-state voltage drop to the on-state current; S3 establishes a linear calibration model of on-resistance and junction temperature, and calculates the real-time junction temperature of the lower bridge arm MOSFET based on the real-time on-resistance; S4 uses the junction temperature data of the lower-arm MOSFET and the measurement data of the NTC temperature sensor to build a thermal coupling model to predict the junction temperature of the upper-arm MOSFET and achieve global monitoring of the junction temperature of power devices in the motor drive.

2. The global monitoring method according to claim 1, characterized in that: The online extraction of on-resistance reuses the ADC channels of three-phase current sampling and synchronously obtains current and voltage drop data through a time-sharing sampling strategy.

3. The global monitoring method according to claim 1, characterized in that: A low-end three-resistance sampling circuit is used to measure the three-phase current, and the on-state voltage drop is collected during the MOSFET on-state window.

4. The global monitoring method according to claim 3, characterized in that: The on-state voltage drop acquisition circuit includes a bias current source, a clamping diode D1, and a compensation diode D2. D1 is used to isolate the bus high voltage; D2 compensates for the measurement error of D1.

5. The global monitoring method according to claim 1, characterized in that: The linear calibration model in step S3 is established through calibration experiments, and the operating temperature range is 0°C to 150°C.

6. The global monitoring method according to claim 1, characterized in that: The thermal coupling model in step S4 is generated through data-driven training, with the input being the lower tube junction temperature, the measurement data of the NTC temperature sensor, and the load condition, and the output being the predicted value of the upper tube junction temperature.

7. A junction temperature monitoring system for implementing the global monitoring method according to any one of claims 1 to 6, characterized in that: include: Main control chip; Three-phase current sampling circuit with multiplexed ADC channels; Contains a conduction voltage drop acquisition circuit for clamping and compensation diodes; NTC temperature sensor; Thermal coupling model processing module.

8. The junction temperature monitoring system according to claim 7, wherein: The main control chip executes the time-sharing sampling algorithm. Within one PWM cycle: Prioritize the collection of three-phase current data for FOC control; Switch to on-state voltage drop sampling during the on-state window period.

9. The junction temperature monitoring system according to claim 7, wherein: The NTC temperature sensor is mounted on the power module substrate to monitor heat distribution changes in real time.

10. A motor driver, characterized in that: Integrate the junction temperature monitoring system described in any one of claims 7 to 9.

Images