Solid-state circuit breaker fault detection device and solid-state circuit breaker comprising same

Abstract

A fault detection device for a solid state circuit breaker and a solid state circuit breaker including the fault detection device, the solid state circuit breaker including a power semiconductor, the fault detection device including a comparator wherein a positive input terminal of the comparator is configured to be connected to an input terminal of the power semiconductor, and a negative input terminal of the comparator is configured to be connected to an output terminal of the power semiconductor. The negative input end of the comparator is connected to a reference voltage through a current path, and the current path is configured to be capable of providing a first threshold voltage for the negative input end of the comparator. The first threshold voltage corresponds to the voltage at the two ends of the power semiconductor when an over-current and over-temperature fault occurs under the condition that the power semiconductor is conducted, and the comparator outputs a signal used for indicating that the power semiconductor breaks down.

Description

Technical Field

[0001] The present invention belongs to the field of solid-state circuit breakers, and in particular relates to a solid-state circuit breaker fault detection device and a solid-state circuit breaker comprising the same. Background Art

[0002] A circuit breaker is a switching device that can close (also called conduction), carry and interrupt (also called interruption) the current under normal circuit conditions and can close, carry and interrupt the current under abnormal circuit conditions within a specified time, such as short circuit, overload or other emergency situations.

[0003] Solid-state circuit breakers (SSCBs) are one of the intelligent forms of circuit breakers, which can replace traditional mechanical circuit breakers for circuit protection. Solid-state circuit breakers are contactless switching devices. Unlike traditional circuit breakers, they are turned on and off by controlling the carriers and carrier channels inside semiconductor power devices (also called "power semiconductors"). In the on state, carrier channels are formed inside the device, carriers are excited in large quantities, and the device's ability to conduct current is enhanced; in the off state, the carrier channels inside the device disappear, and the device blocks the flow of current. Summary of the invention

[0004] Therefore, the object of the present invention is to overcome the defects of the above-mentioned prior art and provide a fault detection device for a solid-state circuit breaker, wherein the solid-state circuit breaker includes a power semiconductor, and the fault detection device includes a comparator, wherein the positive input terminal of the comparator is configured to be connected to the input terminal of the power semiconductor, and the negative input terminal of the comparator is connected to a reference voltage via a current path, and the current path is configured to be able to provide a first threshold voltage for the negative input terminal of the comparator, wherein the first threshold voltage corresponds to the voltage across the power semiconductor when an over-current and over-temperature fault occurs when the power semiconductor is turned on, and the comparator outputs a signal indicating that a fault has occurred in the power semiconductor.

[0005] According to the fault detection device of the present invention, preferably, the current path is also configured to be able to provide a second threshold voltage for the negative input terminal of the comparator, wherein the second threshold voltage corresponds to the voltage across the power semiconductor when a breakdown fault occurs when the power semiconductor is turned off.

[0006] According to the fault detection device of the present invention, preferably, the current path comprises a transistor, and the transistor controls the input voltage of the negative input terminal of the comparator to be the first threshold voltage or the second threshold voltage.

[0007] According to the fault detection device of the present invention, preferably, when the crystal is turned on, the input voltage of the negative input terminal of the comparator is the first threshold voltage; and when the transistor is turned off, the input voltage of the negative input terminal of the comparator is the second threshold voltage.

[0008] According to the fault detection device of the present invention, preferably, the control electrode of the transistor is connected to the gate of the power semiconductor.

[0009] According to the fault detection device of the present invention, preferably, it also includes a first resistor, a second resistor and a third resistor, wherein the second resistor and the third resistor are connected in series between an auxiliary power supply and the reference voltage, a node between the second resistor and the third resistor is connected to a negative input terminal of the comparator, and the transistor is connected in series with the first resistor and in parallel to the third resistor.

[0010] According to the fault detection device of the present invention, preferably, the transistor is a triode, and the first resistor is connected to the emitter of the triode.

[0011] According to the fault detection device of the present invention, preferably, the transistor is a triode, and the first resistor is connected to the collector of the triode.

[0012] According to the fault detection device of the present invention, preferably, it also includes a diode and a pull-up resistor, the diode is reversely arranged between the positive input terminal of the comparator and the input terminal of the power semiconductor, and the pull-up resistor is arranged between the node between the positive input terminal of the comparator and the anode of the diode and the auxiliary power supply.

[0013] The present invention also provides a solid-state circuit breaker, comprising:

[0014] Power semiconductors, which can be placed in a current loop to switch the current on or off;

[0015] an energy absorber connected in parallel to the power semiconductor;

[0016] A driver, which is used to drive the power semiconductor to be turned on and off;

[0017] an auxiliary power supply configured to power the driver; and

[0018] A fault detection device according to the present invention.

[0019] Compared with the prior art, the fault detection device of the present invention can detect overtemperature and overheating faults during the conduction process of the power semiconductor and breakdown faults during the shutdown process of the power semiconductor, thereby ensuring the normal operation of the power semiconductor, with a simple structure and easy operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The embodiments of the present invention are further described below with reference to the accompanying drawings, in which:

[0021] Figure 1 is a structural block diagram of a solid-state circuit breaker according to an embodiment of the present invention;

[0022] Figure 2a-2c Shows the relationship between the electrical characteristics of different power semiconductors and the junction temperature;

[0023] Figure 3 is a circuit diagram of a fault detection device according to an embodiment of the present invention;

[0024] Figure 4 is a circuit diagram of a fault detection device according to another embodiment of the present invention;

[0025] Figure 5 is a circuit diagram of a fault detection device according to another embodiment of the present invention;

[0026] Figure 6 A circuit diagram of a fault detection device according to another embodiment of the present invention;

[0027] Figure 7 is a circuit diagram of a fault detection device according to another embodiment of the present invention; and

[0028] Figure 8 4 is a structural block diagram of a solid-state circuit breaker including a fault detection device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail by specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] See also Figure 1 The structural block diagram of the solid-state circuit breaker according to an embodiment of the present invention is shown, which includes a power semiconductor 100, an energy absorber 102, a driver 104 and an auxiliary power supply 106, wherein the power semiconductor 100 and the energy absorber 102 are connected in parallel in a current loop, the driver 104 is used to drive the power semiconductor 100 to turn on or off, and the auxiliary power supply 106 is used to supply power to the driver 104. When the current loop is abnormal, the driver 104 drives the power semiconductor 100 to turn off to cut off the current loop, and the energy absorber 102 is used to absorb a large amount of inductive energy accumulated in the current loop when the power semiconductor 100 is turned off, thereby realizing the circuit protection function.

[0031] Solid-state circuit breakers include pure solid-state circuit breakers based on pure power semiconductors or hybrid solid-state circuit breakers based on a combination of power semiconductors and mechanical contactors, wherein the power semiconductors may be, for example, insulated gate bipolar transistors (IGBTs), metal oxide semiconductor field effect transistors (MOSFETs), integrated gate commutated thyristors (IGCTs) or a combination thereof. As the main component of SSCB, the reliable operation of power semiconductors is very important for the realization of circuit protection functions. In particular, over-temperature or over-current of power semiconductors in the on state and breakdown of power semiconductors in the off state will cause the power semiconductors to fail to work properly. Therefore, it is necessary to detect and monitor the faults of power semiconductors.

[0032] However, the operating characteristics of power semiconductors in solid-state circuit breaker applications are significantly different from those in power conversion applications (e.g., inverters, DC-DC converters). Therefore, commonly used protection methods, such as Miller clamping protection, active overvoltage clamping protection, and desaturation protection cannot be directly applied to solid-state circuit breaker applications.

[0033] In order to realize fault detection and monitoring of power semiconductors in solid-state circuit breaker applications, the inventors have studied the electrical characteristics of various power semiconductors. The inventors have found that the voltage across the power semiconductor can reflect the current and temperature changes of the power semiconductor, and can therefore be used as an over-temperature and over-current indicator. For example, see Figure 2a-2c The relationship between the electrical characteristics and junction temperature of three different power semiconductors MOSFET, IGBT and IGCT is shown in Figure 1. Figure 2a is the on-state resistance R of the MOSFET DSOn With the junction temperature T J The test condition is the main current I DS =75A, gate voltage V GS =15V, the pulse duration of the test process is t p <200μs, it can be seen that when the main current remains unchanged, the on-resistance increases with the increase of the junction temperature, that is, the voltage across the MOSFET increases with the increase of the junction temperature; Figure 2b The junction temperature T of IGBT is different vj , main current I c As the voltage between its collector and emitter V CE The change curve of the gate voltage V GE =15V, it can be seen that the voltage V CE It increases with the increase of current and also with the increase of junction temperature; Figure 2c is the on-state peak voltage V of the IGCT at different junction temperatures (including standard junction temperature and maximum junction temperature). TWith the on-state peak current I T From the change curve, we can see that the on-state peak voltage increases with the increase of current and also with the increase of junction temperature. Figure 2a-2c It can be seen that the voltage across the power semiconductor increases with the increase of current and temperature. For example, when the power semiconductor operates within the current operating boundary, the abnormal voltage across it reflects an over-temperature fault; when the power semiconductor operates at a constant temperature, the abnormal voltage across it reflects an over-current fault. By detecting and monitoring the voltage across the power semiconductor, the fault of the current loop can be identified, thereby ensuring the normal operation of the SSCB.

[0034] An embodiment of the present invention provides a fault detection device for a power semiconductor to detect over-temperature and over-current faults of the power semiconductor. Figure 3 The circuit diagram of the fault detection device of the embodiment shown includes a comparator U1, wherein the positive power supply terminal of the comparator U1 is powered by the auxiliary power supply 106, and is particularly connected to the power supply port VDD of the auxiliary power supply 106, and the negative power supply terminal is grounded, the positive input terminal of the comparator U1 is connected to the input terminal Port+ of the power semiconductor, and the negative input terminal is provided with a first threshold voltage V1. In this embodiment, the output terminal Port- of the power semiconductor is grounded, and the voltage of the input terminal Port+ of the power semiconductor is equal to the voltage across the power semiconductor. When the voltage across the power semiconductor exceeds the first threshold voltage V1, the signal of the output terminal FB of the comparator U1 changes from low to high, thereby indicating an over-temperature and over-current fault of the power semiconductor. According to other embodiments of the present invention, the output terminal Port- of the power semiconductor does not have to be grounded. As long as the voltage of this terminal is fixed, for example, a fixed reference value is input, the change of the voltage of the input terminal Port+ of the power semiconductor can reflect the change of the voltage across the power semiconductor. In the embodiment of the present invention, if the output terminal Port- of the power semiconductor is grounded, the first threshold voltage V1 provided to the negative input terminal of the comparator U1 is set to be equal to the voltage across the two terminals when an over-temperature and over-current fault occurs to the power semiconductor; if the voltage at the output terminal Port- of the power semiconductor is locked to the reference value V R , then the first threshold voltage V1 provided to the negative input terminal of the comparator U1 is set to be the voltage across the two ends when an over-temperature and over-current fault occurs in the power semiconductor plus the reference value V R In summary, the first threshold voltage V1 corresponds to the voltage across the power semiconductor when an over-temperature and over-current fault occurs.

[0035] Preferably, see Figure 4The circuit diagram of the fault detection device according to another embodiment of the present invention is shown, wherein a reverse diode D1 is connected between the positive input terminal of the comparator U1 and the input terminal Port+ of the power semiconductor, that is, the anode of the diode D1 is connected to the positive input terminal of the comparator U1, and the cathode is connected to the input terminal Port+ of the power semiconductor, so as to prevent the high voltage of the input terminal Port+ from breaking down the comparator U1. In addition, the positive input terminal of the comparator U1 is also connected to the power supply through the pull-up resistor R0, in particular, to the power supply port VDD of the auxiliary power supply. In this case, when the power semiconductor is turned on, there is a low resistance between its input terminal Port+ and the output terminal Port-, and the potential of the cathode of the diode D1 is not much different from the potential of Port-, while the potential of VDD is much higher than that of Port-, so the diode D1 is forward-conducted, and the potential of the anode of the diode D1 (that is, the potential of the positive input terminal of the comparator U1) is equal to the potential of Port+ plus the voltage drop of the diode D1. Therefore, the voltage at the positive input terminal of the comparator U1 can reflect the voltage of Port+, that is, the voltage across the power semiconductor. When the voltage across the power semiconductor exceeds the first threshold voltage V1, the signal at the output terminal FB of the comparator U1 changes from low to high, indicating that the power semiconductor is no longer in a low-resistance state and there is a problem with its conduction, thereby indicating that the power semiconductor is over-temperature and over-current fault.

[0036] According to another embodiment of the present invention, Figure 5 The circuit diagram of the fault detection device of this embodiment is shown in FIG. Figure 4 Compared with the circuit schematic diagram shown in FIG. 1 , the fault detection device of this embodiment further includes a first resistor R1 and a second resistor R2, wherein the negative input terminal of the comparator U1 is connected to the node between the first resistor R1 and the second resistor R2, the other end of the first resistor is connected to the output terminal Port- of the power semiconductor and grounded, and the other end of the second resistor R2 is connected to the power supply port VDD of the auxiliary power supply 106. By setting the resistance values ​​of R1 and R2, the input voltage of the negative input terminal of the comparator U1 can be set, that is, the voltage of the negative input terminal can be set to the first threshold voltage V1 by adjusting R1 and R2. When the power semiconductor has an over-temperature or over-current fault, when the voltage of the positive input terminal of the comparator U1 exceeds the first threshold voltage V1 input at the negative input terminal, the signal of its output terminal FB changes from low to high.

[0037] According to another embodiment of the present invention, Figure 6 The circuit diagram of the fault detection device of this embodiment is shown in FIG. Figure 5Compared with the circuit schematic diagram shown in FIG. 1 , the fault detection device of this embodiment further includes a transistor Q1 and a third resistor R3, wherein the other end of the first resistor R1 is grounded through the transistor Q1, specifically, the other end of the first resistor R1 is connected to the collector of the transistor Q1, the emitter of the transistor Q1 is grounded, and the base of the transistor Q1 is connected to the gate G_P of the power semiconductor; in addition, one end of the third resistor R3 is connected to the negative input end of the comparator U1, and the other end is grounded. Alternatively, in this embodiment, the first resistor R1 is connected between the emitter of the transistor Q1 and the ground line.

[0038] Continue to refer to Figure 6 The working principle of the fault detection device of this embodiment is discussed.

[0039] When the power semiconductor is turned on by the gate G_P signal, the gate G_P signal of the power semiconductor simultaneously drives the transistor Q1 to turn on. At this time, by presetting the values ​​of the resistors R1, R2 and R3, the input voltage of the negative input terminal of the comparator U1 is exactly the first threshold voltage V1. In addition, as mentioned above, the voltage of the positive input terminal of the comparator U1 is equal to the voltage of the input terminal Port+ of the power semiconductor plus the voltage drop on the diode D1, and the output terminal Port- of the power semiconductor is grounded, so the voltage of the positive input terminal of the comparator U1 reflects the voltage across the power semiconductor. When the power semiconductor is working normally, the voltage of the positive input terminal of U1 is lower than the first threshold voltage V1, and the signal of the output terminal FB of the comparator U1 is low. When the power semiconductor is overheated or overcurrent occurs, the voltage of the positive input terminal of U1 will reach the first threshold voltage V1, and the signal of the output terminal FB of the comparator U1 will change from low to high, thereby indicating an overcurrent or overtemperature fault during the conduction process of the power semiconductor.

[0040] When the power semiconductor is turned off, since there is no signal input to its gate G_P, the transistor Q1 is disconnected. At this time, the voltage at the negative input terminal of the comparator U1 depends on the settings of the second resistor R2 and the third resistor R3. By setting the resistance values ​​of R2 and R3, the voltage at the negative input terminal of U1 can be set at the second threshold voltage V2. Under normal circumstances, Port+ and Port- are in a high impedance state. When an external high voltage is applied to the power semiconductor, the potential of Port+ (i.e., the potential of the cathode of the diode D1) is very high, the diode is reversely cut off, and the leakage current is very small. The potential of the anode of the diode D1 is equivalent to the potential of VDD plus the voltage drop on R0. Since the leakage current is extremely small, the current passing through R0 is also extremely small. The potential of the anode of the diode D1 is slightly higher than the potential of VDD, that is, the positive input terminal of U1 inputs a high voltage similar to Port+, and the positive input terminal of U1 inputs a voltage significantly higher than the voltage when the power semiconductor is generally turned on, which can represent the voltage of the high impedance state of the power semiconductor, which is higher than the second threshold voltage V2. Therefore, the signal of the output terminal FB of the comparator U1 is high. When the power semiconductor fails to breakdown, Port+ and Port- are short-circuited, the potential of Port+ becomes low, the diode D1 is forward-conducted, and its anode potential is only higher than the cathode potential by the voltage drop of the diode D1. The voltage at the positive input terminal of U1 is a low voltage similar to Port+, which is lower than the second threshold voltage V2. Therefore, the signal at the output terminal FB of the comparator U1 changes from high to low, indicating that the power semiconductor is no longer in a high-impedance state between Port+ and Port-, thereby indicating a breakdown fault in the off state of the power semiconductor.

[0041] According to another embodiment of the present invention, Figure 7 The circuit diagram of the fault detection device of this embodiment is shown in FIG. Figure 6 As shown in the circuit schematic diagram, the fault detection device of this embodiment also includes a fourth resistor R4 and first to fourth capacitors C1-C4, wherein the fourth resistor R4 is connected between the base of the transistor Q1 and the gate of the power semiconductor, and is used as a base resistor for driving the transistor Q1; the first capacitor C1 is connected between the positive input terminal and the ground of the comparator U1, the second capacitor C2 is connected between the base of the transistor Q1 and the ground, the third capacitor C3 is connected between the negative phase input terminal and the ground of the comparator U1, and the fourth capacitor C4 is connected between the output terminal FB of the comparator U1 and the ground, and they are respectively used as filter capacitors.

[0042] Those skilled in the art will appreciate that the fourth resistor R4 and the first to fourth capacitors C1 - C4 do not have to be arranged in the same circuit structure at the same time, and those skilled in the art may arrange one or more of them in the circuit according to actual needs.

[0043] In the embodiment of the present invention, the transistor Q1 can be replaced by any transistor known in the art, such as IGBT, MOSFET, etc. As long as the control electrode of the transistor is connected to the gate of the power semiconductor, a fault detection logic similar to the above can be implemented.

[0044] The power semiconductor fault detection device according to the embodiment of the present invention can detect overtemperature and overheating faults during the conduction process of the power semiconductor through a simple circuit design, and can also detect breakdown faults during the shutdown process of the power semiconductor, thereby ensuring the normal operation of the power semiconductor.

[0045] An embodiment of the present invention further provides a solid-state circuit breaker, such as Figure 8 The structural block diagram of the solid-state circuit breaker of this embodiment is shown, which includes a power semiconductor 200, an energy absorber 202, a driver 204, an auxiliary power supply 206 and a fault detection unit 208, wherein the power semiconductor 200 and the energy absorber 202 are connected in parallel in a current loop, the input end of the power semiconductor 200 is Port+, the output end is Port-, and the output end Port- is grounded, the driver 204 is used to provide a driving signal to the gate G_P of the power semiconductor 200, and the power supply end of the auxiliary power supply 206 is VDD for powering the driver 204. The fault detection unit 208 of this embodiment can be any one of the fault detection devices in the aforementioned embodiments, and the fault detection unit 208 is configured to be connected to the power supply end VDD of the auxiliary power supply 206, the driving end G_P of the driver 204, and the input end and output end Port+ and Port- of the power semiconductor 200, and the output end FB of the fault detection unit 208 feeds the output signal back to the driver 204.

[0046] In an embodiment of the present invention, the output terminal FB of the fault detection unit 208 can be connected to the analog ADC port, the programmable fault detection device port or the reserved GPIO port of the driver 204. The driver 204 can identify the state of the power semiconductor 200 or transmit the state information of the power semiconductor 200 to the central controller, thereby realizing the protection and monitoring functions.

[0047] According to other embodiments of the present invention, the power semiconductor uses an integrated gate collector thyristor IGCT, and its driver 204 includes a local microcontroller and a commutation chip. It is easy to connect the output terminal FB of the fault detection unit 208 to the local microcontroller to realize monitoring and protection functions.

[0048] According to other embodiments of the present invention, the driver 204 uses a conventional driver chip, and the conventional driver chip does not have a port directly connected to the FB terminal. In this case, the FB terminal can be directly connected to the desaturation terminal of the conventional driver chip, and then external hardware is used to implement over-temperature and over-current protection. The FB terminal can also be directly connected to a separate microcontroller to implement all functions.

[0049] According to other embodiments of the present invention, the comparator in the fault detection device is powered by an additional power supply.

[0050] Although the present invention has been described through preferred embodiments, the present invention is not limited to the embodiments described herein but includes various changes and modifications that may be made without departing from the scope of the present invention.

Claims

1. A fault detection device for a solid-state circuit breaker, the solid-state circuit breaker comprising a power semiconductor, the fault detection device comprising a comparator, wherein: The positive input terminal of the comparator is configured to be connected to the input terminal of the power semiconductor, and the negative input terminal of the comparator is connected to a reference voltage via a current path, and the current path is configured to be able to provide a first threshold voltage for the negative input terminal of the comparator, wherein the first threshold voltage corresponds to the voltage across the power semiconductor when an overcurrent and overtemperature fault occurs when the power semiconductor is turned on, and the comparator outputs a signal indicating that a fault has occurred in the power semiconductor.

2. The fault detection device according to claim 1, wherein: The current path is further configured to provide a second threshold voltage for the negative input terminal of the comparator, wherein the second threshold voltage corresponds to a voltage across the power semiconductor when a breakdown failure occurs when the power semiconductor is turned off. 3 . The fault detection device according to claim 2 , wherein the current path comprises a transistor, and the transistor controls the input voltage of the negative input terminal of the comparator to be the first threshold voltage or the second threshold voltage.

4. The fault detection device according to claim 3, wherein: When the transistor is turned on, the input voltage of the negative input terminal of the comparator is the first threshold voltage; and when the transistor is turned off, the input voltage of the negative input terminal of the comparator is the second threshold voltage.

5. The fault detection device according to claim 3, wherein: The control electrode of the transistor is connected to the gate of the power semiconductor.

6. The fault detection device according to claim 3, further comprising a first resistor, a second resistor and a third resistor, wherein: The second resistor and the third resistor are connected in series between the auxiliary power supply and the reference voltage, a node between the second resistor and the third resistor is connected to the negative input terminal of the comparator, and the transistor is connected in series with the first resistor and in parallel to the third resistor.

7. The fault detection device according to claim 6, wherein: The transistor is a triode, and the first resistor is connected to the emitter of the triode.

8. The fault detection device according to claim 6, wherein: The transistor is a triode, and the first resistor is connected to the collector of the triode.

9. The fault detection device according to any one of claims 1-8 further includes a diode and a pull-up resistor, wherein the diode is reversely arranged between the positive input terminal of the comparator and the input terminal of the power semiconductor, and the pull-up resistor is arranged between the node between the positive input terminal of the comparator and the anode of the diode and the auxiliary power supply.

10. A solid-state circuit breaker comprising: Power semiconductors, which can be placed in a current loop to switch the current on or off; an energy absorber connected in parallel to the power semiconductor; A driver, which is used to drive the power semiconductor to be turned on and off; an auxiliary power supply configured to supply power to the driver; and A fault detection device according to any one of claims 1 to 9.

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