Over-temperature protection circuit for switching device

Abstract

An embodiment of the present disclosure provides an over-temperature protection circuit for a switching device, comprising: a current measurement unit connected to a first electrode of the switching device and capable of generating a first indication signal for indicating the magnitude of a current at the first electrode; the first input end of the voltage measuring unit is connected to the second electrode of the switching device, the second input end of the voltage measuring unit is connected to the first electrode of the switching device, and the voltage measuring unit can generate a second indication signal used for indicating the magnitude of voltage between the second electrode and the first electrode of the switching device; the first input end of the control unit is connected to the output end of the current measuring unit, the second input end of the control unit is connected to the output end of the voltage measuring unit, and the first output end of the control unit is connected to the grid electrode of the switching device; the control unit can determine the working temperature of the switching device based on the first indication signal and the second indication signal and drive the switching device to be turned off under the condition that the working temperature of the switching device is larger than a preset threshold value.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to the field of electrical equipment, and more particularly to an over-temperature protection circuit for a switching device. BACKGROUND

[0002] In solid-state application scenarios, a high-power metal oxide semiconductor field effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT) is usually used to turn off and turn on the main circuit, but the loss generated by turning off and turning on the main circuit is ultimately manifested in the form of heat. The junction temperature of the MOSFET or IGBT should not exceed the maximum junction temperature allowed. If the maximum junction temperature is exceeded, the MOSFET or IGBT will eventually fail.

[0003] If the solid-state product is applied to a motor, over-temperature protection needs to be considered more. Generally speaking, the starting current of the motor will be 5 to 10 times the rated current. Depending on the load, the starting time of the motor can vary greatly, usually between 2 to 30 seconds. In this overload case, it is easy to cause the MOSFET or IGBT to overheat and be damaged. Therefore, it is necessary to monitor the temperature of the MOSFET or IGBT in real time to perform over-temperature protection.

[0004] The traditional temperature detection method of the switching device usually needs to assemble a thermistor on the heat sink of the switching device. Such a detection method is easily limited by the structure. If the product size is small and the installation space is insufficient, this detection method cannot be used. CONTENT OF THE INVENTION

[0005] The purpose of the present disclosure is to provide an over-temperature protection circuit for a switching device to at least partially solve the above problems.

[0006] In a first aspect of the present disclosure, an over-temperature protection circuit for a switching device is provided, comprising: a current measurement unit connected to a first electrode of the switching device and capable of generating a first indication signal indicating the size of the current at the first electrode of the switching device; a voltage measurement unit, a first input end of the voltage measurement unit being connected to a second electrode of the switching device and a second input end being connected to the first electrode of the switching device, the voltage measurement unit being capable of generating a second indication signal indicating the size of the voltage between the second electrode and the first electrode of the switching device; and a control unit, a first input end of the control unit being connected to an output end of the current measurement unit and a second input end being connected to an output end of the voltage measurement unit, a first output end of the control unit being connected to a gate electrode of the switching device, the control unit being capable of determining the operating temperature of the switching device based on the first indication signal and the second indication signal and driving the switching device to turn off if the operating temperature of the switching device is greater than a predetermined threshold.

[0007] In embodiments according to the present disclosure, the current magnitude at the first electrode of the switching device can be reliably detected by the current measurement unit, the voltage magnitude between the second electrode and the first electrode of the switching device can be reliably detected by the voltage measurement unit, the operating temperature of the switching device can be determined based on the first indication signal and the second indication signal by employing the control unit, and the switching device can be reliably driven to turn off in the case that the operating temperature of the switching device is greater than a predetermined threshold value.

[0008] In some embodiments, the current measurement unit comprises a sampling resistor connected to the first electrode of the switching device and a first voltage measurement circuit having a first input and a second input connected to two ends of the sampling resistor to measure the voltage between the two ends of the sampling resistor.

[0009] In some embodiments, the first voltage measurement circuit comprises a first operational amplifier having a non-inverting input and an inverting input connected to the two ends of the sampling resistor, and an output connected to the first input of the control unit.

[0010] In some embodiments, the voltage measurement unit comprises an isolation unit having a first input connected to the second electrode of the switching device and a second input connected to the first electrode of the switching device, a control end connected to the second output of the control unit and capable of isolating the switching device and the second voltage measurement circuit under the control of the control unit, and a second voltage measurement circuit having a first input connected to a first output of the isolation unit and a second input connected to a second output of the isolation unit to measure the voltage between the first output and the second output of the isolation unit.

[0011] In some embodiments, the voltage measurement unit comprises an isolation unit having a first input connected to the second electrode of the switching device and a second input connected to the first electrode of the switching device, a control end connected to the second output of the control unit and capable of isolating the switching device and the second voltage measurement circuit under the control of the control unit, and a second voltage measurement circuit having a first input connected to a first output of the isolation unit and a second input connected to a second output of the isolation unit to measure the voltage between the first output and the second output of the isolation unit.

[0012] In some embodiments, the second voltage measurement circuit comprises a second operational amplifier having a non-inverting input connected to the first output of the isolation unit and an inverting input connected to the second output of the isolation unit, and an output connected to the second input of the control unit.

[0013] In some embodiments, the isolation unit comprises a first resistor and a second resistor, a first end of the first resistor is connected to the second electrode of the switching device, and a first end of the second resistor is connected to the first electrode of the switching device.

[0014] In some embodiments, the voltage measurement unit further comprises a current limiting protection circuit, a first input end of the current limiting protection circuit is connected to a second end of the first resistor, a second input end of the current limiting protection circuit is connected to a second end of the second resistor, a first output end of the current limiting protection circuit is connected to the first input end of the second voltage measurement circuit, and a second output end of the current limiting protection circuit is connected to the second input end of the second voltage measurement circuit.

[0015] In some embodiments, the second electrode of the switching device is connected to one of an external load and a power supply.

[0016] It should be understood that the contents described in this content part are not intended to limit the key features or important features of the embodiments of the present disclosure, nor are they used to limit the scope of the present disclosure. Other features of the present disclosure will become apparent through the following description. BRIEF DESCRIPTION OF DRAWINGS

[0017] The above and other features, advantages, and aspects of embodiments of the present disclosure will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which:

[0018] Figure 1 A circuit block diagram of an over-temperature protection circuit according to one embodiment of the present disclosure is shown;

[0019] Figure 2 A circuit schematic diagram of a voltage measurement unit according to one embodiment of the present disclosure is shown;

[0020] Figure 3 A circuit schematic diagram of a voltage measurement unit according to another embodiment of the present disclosure is shown; and

[0021] Figure 4 A curve diagram showing the on-resistance of a switching device varying with temperature according to one embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0022] Preferred embodiments of the present disclosure will be described in greater detail below with reference to the accompanying drawings. Although preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure is more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0023] The term "comprising" and its variations as used herein signify open inclusion, i.e., "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "at least partially based on". The terms "one example embodiment" and "one embodiment" mean "at least one example embodiment". The term "another embodiment" means "at least one additional embodiment". The terms "first", "second", etc., may refer to different or the same objects.

[0024] As described above, traditional methods for temperature detection in switching devices typically require mounting the thermistor on the heatsink of the switching device. This method is easily limited by structural constraints. If the product is small and there is insufficient installation space, this method cannot be used.

[0025] Therefore, embodiments of this disclosure provide an over-temperature protection circuit for switching devices. According to various embodiments of this disclosure, the on-resistance of the switching device can be calculated by detecting the voltage and current of the switching device, thereby inferring the operating junction temperature of the switching device to determine whether overheating has occurred. No additional temperature sensing element is required, avoiding situations where insufficient installation space prevents real-time temperature measurement. In the following sections, [further details will be provided]. Figures 1 to 4 The principles of this disclosure are described in detail.

[0026] Figure 1 A circuit block diagram of an over-temperature protection circuit 100 according to an embodiment of the present disclosure is shown. Figure 1 As shown, the over-temperature protection circuit 100 generally includes a current measurement unit 10, a voltage measurement unit 20, and a control unit 30. The current measurement unit 10 is connected to the first electrode of the switching device 1 and is capable of generating a first indication signal to indicate the magnitude of the current at the first electrode of the switching device 1. The first input terminal of the voltage measurement unit 20 is connected to the second electrode of the switching device 1, and the second input terminal is connected to the first electrode of the switching device 1. The voltage measurement unit 20 is capable of generating a second indication signal to indicate the magnitude of the voltage between the second electrode and the first electrode of the switching device 1. The first input terminal of the control unit 30 is connected to the output terminal of the current measurement unit 10, and the second input terminal is connected to the output terminal of the voltage measurement unit 20. The first output terminal of the control unit 30 is connected to the gate of the switching device 1. The control unit 30 is capable of determining the operating temperature of the switching device 1 based on the first and second indication signals and driving the switching device 1 to turn off when the operating temperature of the switching device 1 exceeds a predetermined threshold.

[0027] In some embodiments, the switching device 1 can be a metal-oxide-semiconductor field-effect transistor (MOSFET). In the case where the switching device 1 is a MOSFET, the first electrode is the source S and the second electrode is the drain D. In the following, the principles of the present disclosure will be described with the MOSFET as an example of the switching device 1. However, it should be understood that the switching device 1 can also be of other types, without limitation to the embodiments of the present disclosure. As an example, the switching device 1 can also be an insulated-gate bipolar transistor (IGBT). In such an example, the first electrode is the emitter and the second electrode is the collector. The embodiments of the present disclosure are equally applicable to detecting whether the operating temperature of the IGBT is too high.

[0028] In some embodiments, as shown in FIG. 1, a pair of switching devices 1 can be included on a main circuit. The current measurement unit 10 can be disposed between the pair of switching devices 1 and connected to the sources S of the pair of switching devices 1. The first input end of the voltage measurement unit 20 can be connected to the drain D of one of the switching devices 1 in the pair of switching devices 1 and the second input end can be connected to the source S of the switching device 1. In other embodiments, each of the switching devices 1 in the pair of switching devices 1 can be connected with one voltage measurement unit 20. It should be understood that the number of switching devices 1, current measurement units 10 and voltage measurement units 20 can be determined according to actual operating conditions, without limitation to the present disclosure. Figure 1 In some embodiments, the current measurement unit 10 can include a sampling resistor 11. The two ends of the sampling resistor 11 can be connected to the sources S of the pair of switching devices 1, respectively. The sampling resistor 11 has a predetermined resistance and can sample the current on the circuit where the pair of switching devices 1 is located. It should be understood that other types of current sampling devices, such as a Rogowski coil, a Hall element, etc., which can be conceived by those skilled in the art based on the teachings given in the present disclosure, are all within the scope of the present disclosure.

[0029] In some embodiments, the current measurement unit 10 can further include a first voltage measurement circuit 12. The first input end and the second input end of the first voltage measurement circuit 12 are connected to the two ends of the sampling resistor 11, respectively, to measure the voltage between the two ends of the sampling resistor 11. In some embodiments, the first voltage measurement circuit 12 can include a first operational amplifier. The non-inverting input end and the inverting input end of the first operational amplifier are connected to the two ends of the sampling resistor 11, respectively. The output end of the first operational amplifier is connected to the first input end of the control unit 30. The first operational amplifier can generate a first indication signal to be delivered to the control unit 30. The control unit 30 can calculate the current on the circuit where the switching device 1 is located based on the voltage between the two ends of the sampling resistor 11 indicated by the first indication signal and the resistance of the sampling resistor 11.

[0030] In some embodiments, the current measurement unit 10 can include a sampling resistor 11. The two ends of the sampling resistor 11 can be connected to the sources S of the pair of switching devices 1, respectively. The sampling resistor 11 has a predetermined resistance and can sample the current on the circuit where the pair of switching devices 1 is located. It should be understood that other types of current sampling devices, such as a Rogowski coil, a Hall element, etc., which can be conceived by those skilled in the art based on the teachings given in the present disclosure, are all within the scope of the present disclosure.

[0031] With reference to the foregoing Figure 1 In some embodiments, the voltage measurement unit 20 can comprise an isolation unit 21 and a second voltage measurement circuit 22. The first input terminal of the isolation unit 21 is connected to the drain D of the switching device 1 and the second input terminal is connected to the source S of the switching device 1. The control terminal of the isolation unit 21 is connected to the second output terminal of the control unit 30 and is capable of isolating the switching device 1 and the second voltage measurement circuit 22 under the control of the control unit 30. The first input terminal of the second voltage measurement circuit 22 is connected to the first output terminal of the isolation unit 21 and the second input terminal is connected to the second output terminal of the isolation unit 21, so as to measure the voltage between the first output terminal and the second output terminal of the isolation unit 21.

[0032] By providing the isolation unit 21 between the switching device 1 and the second voltage measurement circuit 22, the second voltage measurement circuit 22 can be prevented from being damaged due to the excessively high voltage it bears when the switching device 1 is turned off. The circuit structure and working principle of the voltage measurement unit 20 in different embodiments will be introduced below in connection with Figure 2 and Figure 3 respectively.

[0033] Figure 2 A circuit schematic diagram of the voltage measurement unit 20 according to one embodiment of the present disclosure is shown. In some embodiments, as shown in Figure 2 the isolation unit 21 comprises an isolation switch 210. The first terminal of the isolation switch 210 is connected to the drain D of the switching device 1 and the second terminal is connected to the source S of the switching device 1. The control terminal of the isolation switch 210 is connected to the second output terminal of the control unit 30 and is capable of being turned on and turned off under the control of the control unit 30.

[0034] In some embodiments, as shown in Figure 1 and Figure 2 the drain D of the switching device 1 can be connected to one of the external load 3 and the power supply 2. It should be understood that the connection relationship of the switching device 1 and the main circuit shown in Figure 1 and Figure 2 is only exemplary, and the switching device 1 and the main circuit can also be connected in any appropriate manner.

[0035] In some embodiments, the control unit 30 can control the switching device 1 and the isolation switch 210 to be turned on and turned off according to a predetermined timing. For example, when the switching device 1 needs to be turned on, the control unit 30 can first turn on the switching device 1 and then turn on the isolation switch 210. When the switching device 1 needs to be turned off, the control unit 30 can first turn off the isolation switch 210 and then turn on the switching device 1. In this way, the voltage on the main circuit can be prevented from being directly applied to the second voltage measurement circuit 22 and causing damage to the second voltage measurement circuit 22.

[0036] In some embodiments, the second voltage measurement circuit 22 comprises a second operational amplifier 220. The non-inverting input of the second operational amplifier 220 is connected to the first output of the isolation unit 21 and the inverting input is connected to the second output of the isolation unit 21. The output of the second operational amplifier 220 is connected to the second input of the control unit 30. The control unit 30 can obtain the voltage between the drain D and the source S of the switching device 1 based on the second indication signal generated by the second operational amplifier 220. Further, the control unit 30 can calculate the real-time on-resistance R of the switching device 1 using Ohm’s law based on the voltage between the drain D and the source S of the switching device 1 and the current of the loop in which the switching device 1 is located. DS(on) .

[0037] In some embodiments, the over-temperature protection circuit 100 can be applied to a high-voltage working environment, for example, a three-phase power supply system with a supply voltage of 380V. For example, Figure 2 A case where a two-phase loop in a three-phase power supply system is equipped with the over-temperature protection circuit 100 is shown, and it should be understood that any one-phase loop in a three-phase power supply system can be equipped with the over-temperature protection circuit 100 provided by the embodiments of the present disclosure.

[0038] Figure 3 A circuit schematic diagram of the voltage measurement unit 20 according to another embodiment of the present disclosure is shown. In some embodiments, as shown in Figure 3 The isolation unit 21 can comprise a first resistor 211 and a second resistor 212. The first end of the first resistor 211 is connected to the drain D of the switching device 1. The first end of the second resistor 212 is connected to the source S of the switching device 1. By using the first resistor 211 and the second resistor 212 with high resistance values, the influence of the high voltage of the main loop on the second voltage measurement circuit 22 can be effectively reduced.

[0039] In some embodiments, as shown in Figure 3 The voltage measurement unit 20 further comprises a current limiting protection circuit 23. The first input of the current limiting protection circuit 23 is connected to the second end of the first resistor 211. The second input of the current limiting protection circuit 23 is connected to the second end of the second resistor 212. The first output of the current limiting protection circuit 23 is connected to the first input of the second voltage measurement circuit 22. The second output of the current limiting protection circuit 23 is connected to the second input of the second voltage measurement circuit 22. By setting the current limiting protection circuit 23 between the isolation unit 21 and the second voltage measurement circuit 22, the current from the main loop can be further reduced, thereby protecting the second voltage measurement circuit 22.

[0040] Figure 4A curve diagram showing the variation of the on-state impedance of the switching device with temperature is shown. In some embodiments, the control unit 30 can calculate the real-time on-state impedance R DS(on) and Figure 4 The curve diagram 200 shown determines the working temperature T vj of the switching device 1. By comparing the working temperature T vj with the maximum junction temperature allowed by the switching device 1, it can be determined whether the switching device 1 needs to be driven to turn off. In this way, the working temperature of the switching device 1 can be monitored in real time without installing any temperature measuring device, so that the turn-off operation can be performed in time, greatly improving the reliability of the solid-state circuit breaker.

[0041] The above has described various embodiments of the present disclosure, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, practical application, or technical improvement in the market, or to enable other ordinary skilled persons in the art to understand the embodiments disclosed herein.

Claims

1. An over-temperature protection circuit (100) for a switching device (1), characterized in that The over-temperature protection circuit (100) comprises: a current measurement unit (10) connected to a first electrode of the switching device (1) and capable of generating a first indication signal for indicating a magnitude of current at the first electrode of the switching device (1); a voltage measurement unit (20) having a first input connected to a second electrode of the switching device (1) and a second input connected to the first electrode of the switching device (1), and capable of generating a second indication signal for indicating a magnitude of voltage between the second electrode and the first electrode of the switching device (1); and a control unit (30) having a first input connected to an output of the current measurement unit (10) and a second input connected to an output of the voltage measurement unit (20), and having a first output connected to a gate of the switching device (1), and capable of determining an operating temperature of the switching device (1) based on the first indication signal and the second indication signal and driving the switching device (1) to turn off in a case where the operating temperature of the switching device (1) is greater than a predetermined threshold.

2. The over-temperature protection circuit (100) according to claim 1, characterized in that The current measurement unit (10) comprises a sampling resistor (11) connected to the first electrode of the switching device (1) and a first voltage measurement circuit (12) having a first input and a second input connected to two ends of the sampling resistor (11) respectively to measure a voltage between the two ends of the sampling resistor (11).

3. The over-temperature protection circuit (100) according to claim 2, characterized in that The first voltage measurement circuit (12) comprises a first operational amplifier having a non-inverting input and an inverting input connected to the two ends of the sampling resistor (11) respectively, and an output connected to the first input of the control unit (30).

4. The over-temperature protection circuit (100) according to claim 1, characterized in that The voltage measurement unit (20) comprises an isolation unit (21) having a first input connected to the second electrode of the switching device (1) and a second input connected to the first electrode of the switching device (1), and having a control end connected to a second output of the control unit (30) and capable of isolating the switching device (1) and a second voltage measurement circuit (22) under control of the control unit (30), and a second voltage measurement circuit (22) having a first input connected to a first output of the isolation unit (21) and a second input connected to a second output of the isolation unit (21) to measure a voltage between the first output and the second output of the isolation unit (21).

5. The over-temperature protection circuit (100) according to claim 4, characterized in that The isolation unit (21) comprises a disconnector (210), a first end of the disconnector (210) is connected to the second electrode of the switching device (1) and a second end is connected to the first electrode of the switching device (1), a control end of the disconnector (210) is connected to the second output end of the control unit (30) and can be turned on and turned off under the control of the control unit (30).

6. The over-temperature protection circuit (100) according to claim 4, characterized in that The second voltage measurement circuit (22) comprises a second operational amplifier (220), a non-inverting input end of the second operational amplifier (220) is connected to the first output end of the isolation unit (21) and an inverting input end is connected to the second output end of the isolation unit (21), an output end of the second operational amplifier (220) is connected to the second input end of the control unit (30).

7. The over-temperature protection circuit (100) according to claim 4, characterized in that The isolation unit (21) comprises a first resistor (211) and a second resistor (212), a first end of the first resistor (211) is connected to the second electrode of the switching device (1), a first end of the second resistor (212) is connected to the first electrode of the switching device (1).

8. The over-temperature protection circuit (100) according to claim 7, characterized in that The voltage measurement unit (20) further comprises a current limiting protection circuit (23), a first input end of the current limiting protection circuit (23) is connected to the second end of the first resistor (211), a second input end of the current limiting protection circuit (23) is connected to the second end of the second resistor (212), a first output end of the current limiting protection circuit (23) is connected to the first input end of the second voltage measurement circuit (22), and a second output end of the current limiting protection circuit (23) is connected to the second input end of the second voltage measurement circuit (22).

9. The over-temperature protection circuit (100) according to claim 1, characterized in that The second electrode of the switching device (1) is connected to one of an external load (3) and a power supply (2).

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