Turn-off delay time detection device and method for online junction temperature detection

Abstract

The invention discloses a turn-off delay time detection device and a turn-off delay time detection method for on-line junction temperature detection, and aims to solve the contradiction between high voltage tolerance and accurate detection of a low voltage part in a traditional detection method and realize reliable on-line detection of the junction temperature of a power switch device. Comprises: a displacement current extraction circuit detects a capacitor element current having a function relationship with voltages at two ends of a detected power switch device, and outputs an electric signal containing current information; the starting moment detection circuit receives a grid voltage signal and detects a starting moment according to the standard that the grid voltage drops to 90% of a high level, and the ending moment detection circuit receives a current information electric signal and detects an ending moment according to an experimental calibration threshold; the turn-off delay time extraction circuit generates a signal containing delay time based on the time information; the controller calculates the junction temperature according to the calibration relation between the delay time and the junction temperature. High-voltage impact is avoided through indirect current detection, all links are accurately matched, and the device is suitable for various circuit scenes and has low cost and high reliability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of power electronics, and particularly relates to a turn-off delay time detection device and method for online junction temperature detection. BACKGROUND

[0002] As a core component of power electronic devices, the reliability of power switching devices is related to the reliability of the operation of the entire power electronic device. The failure of power switching devices is dominated by thermal failure, and over-temperature and temperature fluctuation are two main reasons for the thermal failure of power switching devices. By detecting the junction temperature of the power switching device in real time, the working condition of the power switching device can be monitored in real time, and the basis for thermal management of the power switching device is provided, thereby improving the reliability of the power switching device and ensuring the reliable operation of the power electronic device.

[0003] There are four existing online junction temperature detection methods: physical contact measurement method, optical method, thermal impedance model method and thermal sensitive electrical parameter method. Among them, the thermal sensitive electrical parameter method uses the parameters of the measured device itself as the temperature detection index to detect the junction temperature of the power switching device, that is, the measured device itself is a thermal sensor, so the method has fast response speed, high accuracy and is easy to integrate. The turn-off delay time is favored due to its excellent linearity with temperature.

[0004] According to the definition, the turn-off delay time is the time for the gate voltage of the measured power switching device to drop to 90% to the time for the voltage across the power switching device to rise to 10%, so the traditional turn-off delay time detection method needs to detect the voltage across the measured power switching device, which requires the detection circuit to withstand the high voltage (high level of voltage across the power switching device) during the operation of the measured device. In order to ensure the reliable operation of the detection circuit, the voltage across the power switching device is usually scaled. However, the actual detection of the detection circuit is only the low voltage part of 10% of the voltage across the power switching device, and the low voltage part is scaled at the same time when the voltage across the power switching device is scaled. Therefore, the detection circuit is difficult to accurately detect the low voltage part of the voltage across the power switching device while withstanding the high voltage, which poses a challenge to the design of the detection circuit. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a turn-off delay time detection device and method for online junction temperature detection to solve the technical problem that the traditional turn-off delay time detection method is difficult to accurately detect the low voltage part of the voltage across the power switching device while withstanding the high voltage of the measured power switching device during detection of the voltage across the power switching device. The detection of the displacement current of the capacitor element is used instead of the detection of the voltage across the measured power switching device, which avoids related problems and completes the detection of the turn-off delay time.

[0006] The application adopts the following technical solutions: A turn-off delay time detection method for online junction temperature detection, comprising the following steps: extracting a displacement current of a capacitor element associated with a power switching device, and outputting an electrical signal representing the displacement current; detecting a start time of the turn-off delay time based on a gate voltage signal of the power switching device, and outputting a start time signal; detecting an end time of the turn-off delay time based on the output electrical signal, and outputting an end time signal; extracting a turn-off delay time signal according to the time interval between the start time signal and the end time signal; calculating the junction temperature of the measured device according to the turn-off delay time signal based on the pre-calibrated corresponding relationship between the turn-off delay time and the junction temperature.

[0007] Preferably, the capacitor element is an independent capacitor element or a parasitic capacitor. When the measured power switching device is in the upper tube of a half-bridge circuit, the capacitor element is the gate-drain parasitic capacitor of the upper tube power switching device of the half-bridge circuit.

[0008] Preferably, the detection of the start time is realized by comparing the gate voltage with a first threshold voltage, and the first threshold voltage corresponds to 90% of the high level of the gate voltage.

[0009] Preferably, the detection of the end time is realized by comparing the voltage signal corresponding to the displacement current signal with a second threshold voltage, and the second threshold voltage is obtained by experimental calibration and corresponds to the displacement current signal amplitude when the voltage across the power switching device rises to 10% of the high level.

[0010] Preferably, the second threshold voltage is set to be less than the calibration value.

[0011] Another technical solution of the application is a turn-off delay time detection device for online junction temperature detection, comprising: a controller for generating a driving signal and processing turn-off delay time information; a driving circuit connected with the controller, for controlling the turn-on and turn-off of the power switching device according to the driving signal; a detection circuit, comprising: a displacement current extraction circuit for extracting a displacement current signal of a capacitor element associated with the power switching device; a start time detection circuit connected with the driving circuit, for detecting the start time of the turn-off delay time based on the gate voltage signal of the power switching device; An end-time detection circuit, connected to the displacement current extraction circuit, is used to detect the end time of the turn-off delay time based on the displacement current signal. A shutdown delay time extraction circuit is connected to the start time detection circuit and the end time detection circuit respectively, and is used to extract shutdown delay time information based on the start time and the end time; The controller is also connected to the shutdown delay time extraction circuit for reading the shutdown delay time information and calculating the junction temperature.

[0012] Preferably, an isolation device is included, which is disposed between the start time detection circuit, the end time detection circuit and the turn-off delay time extraction circuit, for isolating the signal input to the turn-off delay time extraction circuit.

[0013] Preferably, the start time detection circuit includes a first comparator circuit for comparing the gate voltage with a first threshold voltage to detect the start time.

[0014] Preferably, the end time detection circuit includes a second comparator circuit for comparing the voltage signal output by the displacement current extraction circuit with a second threshold voltage to detect the end time.

[0015] Preferably, the turn-off delay time extraction circuit includes an XOR gate circuit, used to generate a square wave signal with a pulse width equal to the turn-off delay time based on the output signals of the start time detection circuit and the end time detection circuit.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: A method for detecting turn-off delay time in online junction temperature monitoring replaces voltage detection across power switching devices with capacitor displacement current detection. This avoids the impact of high voltage on the circuit while ensuring the basic accuracy of turn-off delay time detection. Each step is interconnected; the electrical signals and timing information output from previous steps directly provide data support for subsequent steps, ensuring the integrity and continuity from signal acquisition to junction temperature calculation, and providing a practical solution for online junction temperature monitoring.

[0017] Furthermore, by clarifying the selectable types of capacitor components and their specific applications in half-bridge circuits, the practicality and flexibility of the method are significantly improved.

[0018] Furthermore, the detection criteria and implementation methods for the start moment are refined to ensure the accuracy of the identification of the start point of the turn-off delay time. The detection benchmark is set based on the classic definition of the turn-off delay time, conforming to industry consensus and technical specifications. A comparator circuit is used to output a level transition signal through threshold comparison; the hardware implementation is simple and the response speed is fast, accurately capturing the critical change moment of the gate voltage. This design provides a clear judgment basis and a reliable implementation path for the start moment detection, avoiding subjective judgment errors and providing an accurate starting benchmark for subsequent time calculations.

[0019] Furthermore, using the voltage across the device rising to 10% of its high level as a defining benchmark, a complete time boundary is formed with the start time. By experimentally calibrating the comparison threshold, a precise correlation is established between the displacement current signal and the voltage critical state. Then, by using a comparator to detect the signal rise time, the end time is indirectly and accurately captured. This method of calibrating the threshold and comparing the signal eliminates the need for direct detection of low-voltage signals, avoiding high-voltage interference and ensuring detection accuracy through calibration compensation, thus providing a reliable endpoint basis for delay time calculation.

[0020] Furthermore, explicitly setting the threshold value below the experimental calibration value effectively avoids false triggering caused by circuit noise and signal fluctuations, ensuring that the end time is only identified when the displacement current signal actually reaches the correlation value of the corresponding voltage critical state. This conservative setting does not affect the detection accuracy, but also enhances the circuit's tolerance to environmental interference, reduces the probability of false detection, and makes the end time identification more robust.

[0021] Furthermore, the XOR gate can quickly respond to the level transition signals at the start and end times, forming a square wave with a pulse width equal to the delay time through two transitions, thus transforming abstract time information into a directly measurable pulse width parameter. This design does not require complex signal processing algorithms, has low hardware cost, and fast response speed. The controller can directly obtain the delay time by reading the pulse width, reducing data processing difficulty and improving detection efficiency.

[0022] Furthermore, the calibration method is tailored to the individual characteristics of power switching devices, which can compensate for parameter differences between devices and avoid errors caused by general models; the calibration relationship is stored in the controller, enabling real-time and rapid calculation of junction temperature, ensuring the timeliness and accuracy of online detection.

[0023] Furthermore, the controller and detection circuit have a clear division of labor. The controller is responsible for driving and data processing, while the detection circuit focuses on signal acquisition and time extraction. Each sub-circuit forms a closed loop through input and output connections. The output of the displacement current extraction circuit directly supplies the end-time detection, and the time signals from both ends are input to the time extraction circuit. Finally, the data is uploaded to the controller. This architecture has a clear logic and a high degree of modularity, ensuring the independent implementation of each function while ensuring the integrity of signal transmission through reasonable connections, enabling the device to operate stably and output reliable data.

[0024] In summary, this invention replaces the detection of the voltage across the power switching device under test with the detection of the displacement current of the capacitor element, thereby completing the detection of the end time of the turn-off delay time. While ensuring the accuracy of online junction temperature detection using the turn-off delay time, it also enhances the flexibility of online junction temperature detection applications using the turn-off delay time.

[0025] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the following description of the relative embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic block diagram of the overall structure of a turn-off delay time detection device used for online junction temperature detection; Figure 2 This is a schematic diagram of the specific structure of a half-bridge circuit testing device using a silicon carbide MOSFET as the device under test. Figure 3 This is a schematic diagram of the operating waveform of the detection circuit; Figure 4 This is a schematic diagram of a turn-off delay time detection device with isolation components.

[0028] Wherein: 100. Controller; 110. Detection circuit; 111. Turn-off delay time extraction circuit; 112. End time detection circuit; 113. Start time detection circuit; 114. Displacement current extraction circuit; 120. Drive circuit; 130. Capacitor element; 140. Power switching device; 141. Upper tube power switching device. Detailed Implementation

[0029] 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, not all, of the embodiments of the present invention. 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.

[0030] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "one side," "one end," and "one side," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0033] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0034] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0035] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0036] This invention provides a turn-off delay time detection device and method for online junction temperature detection. By detecting the displacement current of the capacitor element, the detection of the voltage across the power switch device under test is replaced by the detection of the voltage across the power switch device under test. This avoids the problem that the detection circuit is difficult to accurately detect the low voltage part of the power switch device while withstanding the high operating voltage of the device under test.

[0037] Please see Figure 1 The present invention discloses a turn-off delay time detection device for online junction temperature detection, comprising a controller 100 and a detection circuit 110. The detection circuit 110 extracts the turn-off delay time based on the signals of the capacitor element 130 and the driving circuit 120 of the power switching device 140 in the circuit. The controller 100 provides a control signal to the detection circuit 110 and a driving signal to the driving circuit 120, and completes the reading of the turn-off delay time.

[0038] The detection circuit 110 comprises a displacement current extraction circuit 114, a start time detection circuit 113, an end time detection circuit 112, and a turn-off delay time extraction circuit 111.

[0039] The controller 100 includes a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, and is suitable for implementing one or more instructions, specifically for loading and executing one or more instructions to achieve corresponding method flows or corresponding functions.

[0040] The power switching device 140 is the device under test, which can be a metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated-gate bipolar transistor (IGBT).

[0041] The drive circuit 120 is used to control the power switching device 140 to turn on or off according to the drive signal.

[0042] Capacitor element 130 can be an independent capacitor element or a parasitic capacitor (referring to the accidental capacitance generated between circuit conductors such as printed circuit boards, component leads, and connectors). There is a functional relationship between the voltage across capacitor element 130 and the voltage across power switching device 140; the voltage across capacitor element 130 can be calculated based on the voltage across power switching device 140. At the end of the turn-off delay time, the voltage across power switching device 140 begins to rise, and the voltage across capacitor element 130 also begins to change, thus generating a displacement current.

[0043] A method for detecting turn-off delay time for online junction temperature detection includes the following steps: S1, the displacement current extraction circuit 114 detects the current of the capacitor element 130, which can be the entire current or a portion of the current. Simultaneously, it outputs a voltage or current signal. For example, in a half-bridge circuit, when the power switching device 140 of the lower transistor is used as the device under test, the Miller capacitor of the transistor pair can be selected as the capacitor element 130. When the turn-off delay time of the device under test ends, the voltage across the power switching device 140 begins to rise, and the voltage across the transistor pair begins to fall. The Miller capacitor discharges, generating a displacement current. Part of this displacement current flows through the drive circuit of the transistor pair. Therefore, detecting the current flowing through the drive circuit of the transistor pair can replace detecting the voltage across the device under test.

[0044] S2, the start time detection circuit 113 detects the start time and turn-off time of the power switching device 140 under test according to the end time detection circuit 112 respectively; S201, the gate voltage input start time detection circuit 113 of the power switching device 140 detects the start time of the turn-off delay time according to the definition of the start time of the turn-off delay time, and outputs a signal containing the start time information of the turn-off delay time. For example, the start time of the turn-off delay is defined as when the gate voltage drops to 90% of the high level. The start time detection circuit 113 can use a comparator circuit to set a comparison threshold based on 90% of the high level of the gate voltage. At the same time, the gate voltage signal is input to the comparator circuit, and the output signal of the comparator circuit can switch levels at the start time of the turn-off delay, outputting a signal containing the start time information of the turn-off delay.

[0045] S202. The output signal of the displacement current extraction circuit 114 is input to the end time detection circuit 112 to detect the end time of the turn-off delay time and output a signal containing the end time information of the turn-off delay time.

[0046] For example, in a half-bridge circuit, the displacement current extraction circuit 114 converts the current flowing through the transistors of the device under test into a voltage signal, which is input to the end-time detection circuit 112. When the turn-off delay time of the device under test ends and the voltage across the device under test begins to rise, the voltage signal output by the displacement current extraction circuit 114 begins to rise. The end-time detection circuit 112 can select a comparator circuit to detect the moment when the output signal of the displacement current extraction circuit 114 begins to rise, switch levels, and output a signal containing information about the end time of the turn-off delay time.

[0047] In addition, the threshold voltage of the comparator circuit can be obtained through experimental calibration. For example, the end time of the turn-off delay time is defined as the voltage across the device under test rising to 10%. Through experimentation, the amplitude (calibrated value) of the output voltage of the displacement current extraction circuit 114 when the voltage across the device under test rises to 10% is measured. Based on this, the comparator threshold voltage is set through the digital-to-analog converter. However, it does not need to be exactly the same as the calibrated value. It is sufficient to select a fixed value that is close to the calibrated value. It is recommended to be lower than the calibrated value. S3. Input the output signals of the end time detection circuit 112 and the start time detection circuit 113 to the turn-off delay time extraction circuit 111. The turn-off delay time extraction circuit generates a signal containing the turn-off delay time information based on the turn-off delay time start time information and end time information in the output signal. For example, the output signal of the start time detection circuit 113 jumps to a new level at the start of the turn-off delay time, and the output signal of the end time detection circuit 112 jumps to a new level at the end of the turn-off delay time. The output signal of the turn-off delay time extraction circuit 111 jumps to a new level when the output signals of the start time detection circuit 113 and the end time detection circuit 112 jump to a new level. The time interval between the two jump levels is the turn-off delay time, and the turn-off delay time extraction circuit 111 can output a signal containing the turn-off delay time information.

[0048] S4. The controller 100 extracts the turn-off delay time information contained in the output signal of the turn-off delay time extraction circuit 111, and calculates the junction temperature of the device under test based on the relationship between the turn-off delay time and the junction temperature.

[0049] The relationship between turn-off delay time and junction temperature can be obtained through calibration. By applying a specific and known junction temperature to the device under test, the controller 100 extracts the turn-off delay time measured by the detection circuit 110, thereby obtaining the relationship between the turn-off delay time and junction temperature.

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0051] Example 1 Taking silicon carbide MOSFETs as an example of power switching devices, such as Figure 2 As shown, in a half-bridge application, the lower transistor is the power switch device under test 140, and the gate-drain capacitance of the upper transistor power switch device 141 can be used. C GD As a capacitor element 130, the controller 100 controls the power switching device 140 via the drive circuit 121. R Gob and R Gcb These are the on-resistance and off-resistance, respectively; simultaneously, the power switching device 141 is controlled by the drive circuit 122. R Got and R Gct These are the on-resistance and off-resistance, respectively. Controller 100 can be of models such as the DSP TMS320F28335.

[0052] In this situation, at the end of the turn-off delay time of the lower power switch 140, the drain-source voltage of the lower power switch 140 begins to rise, the drain-source voltage of the upper power switch 141 begins to fall, and the gate-drain capacitance (capacitor element 130) of the upper power switch 141 begins to discharge, generating a displacement current. A portion of this current ( I Gct ) flows through the turn-off resistor ( R Gct Another part will be given to the gate-source capacitance ( C GS Charging, such as Figure 2 As shown by the dashed line. Therefore, the flow through the turn-off resistor can be detected. R Gct The current is used to replace the measurement of the drain-source voltage of the power switching device 140 under test.

[0053] The displacement current extraction circuit 114 is built based on operational amplifier A3. A3 can be of models such as OPA817. R 1= R 2 and R 3= R 4 / / R Under the condition of 5, the output voltage of the current extraction circuit 114 is I Gct R Gct R 4 / R 2, its waveform is as follows Figure 3 As shown, at the end of the turn-off delay time, the drain-source voltage of the power switching device 140 under test begins to rise, and at the same time, the output voltage of the current extraction circuit 114 begins to rise.

[0054] The start-time detection circuit 113 is built based on comparator A2. A2 can be a high-speed comparator such as the TLV3603 with latching function. The latching state of comparator A2 is controlled by a NAND gate G2, such as the SN74LVC1G00. The gate-source voltage of the power switching device 140 under test is divided by resistors and input to the inverting input of comparator A2. Simultaneously, the comparison threshold is set by controlling the voltage at the non-inverting input. V 3. Comparison threshold V 3. The turn-off delay time can be selected based on the definition of its start time. For example, the start time of the turn-off delay time is defined as the gate-source voltage of the power switching device 140 under test dropping to 90% of its high level, and this high level decaying to 5V after being divided by resistors. Then, the comparison threshold is... V 3 can be set to 4.5V. Before the shutdown process begins, controller 100 controls comparator A2 through NAND gate G2, causing it to exit the latched state and output a low level. At the start of the shutdown delay time... t 2. The output signal of comparator A2, that is, the output signal level of the detection circuit 113 at the beginning, is reversed to a high level and enters the latch state, and remains at a high level.

[0055] The end-time detection circuit 112 is built based on comparator A1. A1 can be a high-speed comparator such as the TLV3603 with latching function, and the latching state of comparator A1 is controlled by a NAND gate G1, such as the SN74LVC1G00. The output signal of the displacement current extraction circuit 114 is input to the non-inverting input of comparator A1. If the comparator is single-voltage powered, such as using a TLV3603, a resistor can be used to boost the output signal of the displacement current extraction circuit 114 to a DC level before inputting it into comparator A1. For example, as... Figure 2 As shown, in R 6= R Under condition 7, the output signal of displacement current extraction circuit 114 will be boosted. V 2 / 2 DC level. Comparison threshold of comparator A1. V 1. This can be measured experimentally. For example, the end time of the turn-off delay is defined as the time when the drain-source voltage of the power switching device 140 under test rises to 10% of its high level. The voltage value of the output signal of the displacement current extraction circuit 114 at this moment can be measured. V o114 Then, the range that the comparison threshold can be set to is... V 2 / 2 to V 2 / 2+ V o114 / 2, when set to V 2 / 2+ V o114When / 2, the turn-off delay time ultimately measured by the detection circuit 110 is equal to the defined turn-off delay time. When the set value is less than V 2 / 2+ V o114 When / 2, the turn-off delay time ultimately measured by the detection circuit 110 will have a fixed difference from the defined turn-off delay time. It is recommended that the comparison threshold setting be less than V 2 / 2+ V o114 / 2. Similarly, before the shutdown process arrives, the controller 100 controls the comparator A1 through the NAND gate G1, causing it to exit the latched state and output a low level. At the end of the shutdown delay time... t 3. The output signal of comparator A1, that is, the output signal level of the end-time detection circuit 112, is reversed to a high level and enters a latching state, remaining at a high level.

[0056] Before the next shutdown process arrives, the controller 100 controls comparators A1 and A2 through NAND gates G1 and G2, causing them to exit the latched state and simultaneously go low.

[0057] At this time, the output signals of the start time detection circuit 113 and the end time detection circuit 112 are input to the turn-off delay time extraction circuit 111. The turn-off delay time extraction circuit 111 can be built based on an XOR gate G3, such as the SN74LVC1G86. The output signal of the XOR gate G3, which is also the output signal of the turn-off delay time extraction circuit 111, jumps to the appropriate level at the same time as the output signals of the start time detection circuit 113 and the end time detection circuit 112, thus outputting a square wave with a pulse width equal to the turn-off delay time.

[0058] The controller 100 can obtain the turn-off delay time of the power switching device 140 under test by reading the pulse width of the square wave output by the turn-off delay time extraction circuit 111. Based on the relationship between the turn-off delay time and the junction temperature stored in the controller, the junction temperature of the power switching device 140 under test can be obtained.

[0059] The relationship between turn-off delay time and junction temperature can be obtained through calibration. By applying a specific and known junction temperature to the device under test, the controller 100 extracts the turn-off delay time measured by the detection circuit 110, thereby obtaining the relationship between the turn-off delay time and junction temperature.

[0060] Example 2 Example 2 is an isolation scheme based on Example 1, such as... Figure 4As shown, its principle is the same as that of Embodiment 1. The difference is that before the output signals of the start time detection circuit 113 and the end time detection circuit 112 are input to the turn-off delay time extraction circuit 111, they pass through the isolation device ISO. The isolation device ISO can be a digital isolation device of various forms. In this case, the displacement current extraction circuit 114 can use the midpoint of the bridge arm as ground. Then, the displacement current extraction circuit 114 will not contain a high voltage signal, and the reliability of the detection circuit is higher.

[0061] In summary, this invention provides a turn-off delay time detection device and method for online junction temperature monitoring. Its core innovation—replacing voltage detection with displacement current detection—completely resolves the contradiction between high voltage tolerance and low voltage detection accuracy in traditional methods. Hardware-wise, parasitic capacitance can be utilized to reduce costs, and modular circuit design improves integration. Logically, precise timing identification is achieved through calibrated thresholds and comparator circuits, while XOR gates extract timing information, ensuring accurate delay time detection. The device is compatible with MOSFETs, IGBTs, and other devices, as well as half-bridge topologies, and can be integrated into drive circuits. Optional isolation schemes enhance safety. The overall solution combines low cost, high accuracy, and strong adaptability, providing an efficient and reliable technical path for online junction temperature monitoring of power switching devices.

[0062] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for detecting the turn-off delay time for online junction temperature detection, characterized in that, Includes the following steps: Extract the displacement current of the capacitor element (130) associated with the power switching device (140) and output an electrical signal characterizing the displacement current; Based on the gate voltage signal of the power switching device (140), the start time of the turn-off delay time is detected and the start time signal is output. Based on the output electrical signal, the end time of the turn-off delay time is detected, and the end time signal is output. Based on the time interval between the start time signal and the end time signal, extract the shutdown delay time signal; Based on the pre-calibrated correspondence between turn-off delay time and junction temperature, the junction temperature of the device under test is calculated according to the turn-off delay time signal.

2. The method for detecting turn-off delay time for online junction temperature detection according to claim 1, characterized in that, The capacitor element (130) is an independent capacitor element or a parasitic capacitor. When the power switching device under test is in the lower tube of the half-bridge circuit, the capacitor element is the gate-drain parasitic capacitance of the power switching device in the upper tube of the half-bridge circuit.

3. The method for detecting turn-off delay time for online junction temperature detection according to claim 1, characterized in that, The detection of the start time is achieved by comparing the gate voltage with a first threshold voltage, the first threshold voltage corresponding to 90% of the high level of the gate voltage.

4. The method for detecting turn-off delay time for online junction temperature detection according to claim 1, characterized in that, The detection of the end time is achieved by comparing the voltage signal corresponding to the displacement current signal with the second threshold voltage, which is obtained through experimental calibration and corresponds to the amplitude of the displacement current signal when the voltage across the power switch device (140) rises to 10% of the high level.

5. The method for detecting turn-off delay time for online junction temperature detection according to claim 4, characterized in that, The second threshold voltage is set to be less than the calibration value.

6. A turn-off delay time detection device for online junction temperature detection, characterized in that, include: Controller (100) is used to generate drive signals and process turn-off delay time information; A drive circuit (120), connected to the controller (100), is used to control the power switching device (140) to turn on and off according to the drive signal; The detection circuit (110) includes: Displacement current extraction circuit (114) is used to extract the displacement current signal of the capacitor element (130) associated with the power switching device (140); A start time detection circuit (113) is connected to the drive circuit (120) and is used to detect the start time of the turn-off delay time based on the gate voltage signal of the power switching device (140); The end time detection circuit (112) is connected to the displacement current extraction circuit (114) and is used to detect the end time of the turn-off delay time based on the displacement current signal. The shutdown delay time extraction circuit (111) is connected to the start time detection circuit (113) and the end time detection circuit (112) respectively, and is used to extract shutdown delay time information based on the start time and the end time; The controller (100) is also connected to the shutdown delay time extraction circuit (111) for reading the shutdown delay time information and calculating the junction temperature.

7. The off-delay time detection device for online junction temperature detection according to claim 6, characterized in that, It includes an isolation device, which is disposed between the start time detection circuit, the end time detection circuit and the turn-off delay time extraction circuit, and is used to isolate the signal input to the turn-off delay time extraction circuit.

8. The turn-off delay time detection device for online junction temperature detection according to claim 6, characterized in that, The start time detection circuit (113) includes a first comparator circuit for comparing the gate voltage with a first threshold voltage to detect the start time.

9. The turn-off delay time detection device for online junction temperature detection according to claim 6, characterized in that, The end time detection circuit (112) includes a second comparator circuit for comparing the voltage signal output by the displacement current extraction circuit (114) with a second threshold voltage to detect the end time.

10. The turn-off delay time detection device for online junction temperature detection according to claim 6, characterized in that, The turn-off delay time extraction circuit (111) includes an XOR gate circuit, which is used to generate a square wave signal with a pulse width equal to the turn-off delay time based on the output signals of the start time detection circuit (113) and the end time detection circuit (112).

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