IGBT short circuit detection circuit and frequency converter

Abstract

The utility model relates to an IGBT short circuit detection circuit and a frequency converter. The IGBT short circuit detection circuit comprises a bias current source, a discharge loop and a voltage comparison circuit. The input end of the bias current source is connected with the output end of a driving branch for driving the IGBT; the input end of the discharge loop is connected with the output end of the bias current source, and the output end of the discharge loop is connected with the collector electrode of the IGBT and is used for providing a discharge channel for the bias current source when the IGBT is conducted; the first input end of the voltage comparison circuit is connected with the input end of the discharging loop and the output end of the bias current source, and the voltage comparison circuit is used for comparing a first voltage signal input by the first input end with a reference voltage signal input by the second input end so as to detect whether the IGBT is short-circuited or not. According to the application, the bias voltage can be provided for short-circuit detection when the IGBT is switched on, and the detection circuit does not work when the IGBT is switched off, so that the power consumption of the resistor on the bias current source and the risk of false triggering are reduced, the anti-interference capability is stronger, and the problems of relatively high power consumption and easy false detection are solved.

Description

Technical Field

[0001] This application relates to the field of IGBT technology, and in particular to an IGBT short-circuit detection circuit and frequency converter. Background Technology

[0002] In the field of power electronics such as frequency converters, IGBTs (Insulated-Gate Bipolar Transistors) are commonly used as the core inverter unit for output inversion. In actual use, various factors such as environmental conditions and load faults can cause output short circuits in the frequency converter. During a short circuit, a large amount of heat is generated, burning out the IGBTs and causing irreversible damage to the entire frequency converter. Therefore, it is necessary to be able to quickly detect short circuit faults and provide protection.

[0003] Currently, in addition to dedicated driver chips with integrated short-circuit detection that are expensive, short-circuit detection can also be performed by detecting the output current of the frequency converter. However, this method mostly uses a constant current source, which consumes a lot of power and is prone to false detection.

[0004] There is currently no effective solution to the problems of high power consumption and easy false detection in related technologies. Utility Model Content

[0005] Therefore, it is necessary to provide an IGBT short-circuit detection circuit and frequency converter that can reduce power consumption and false detection, in order to address the above-mentioned technical problems.

[0006] Firstly, this embodiment provides an IGBT short-circuit detection circuit, including a bias current source, a discharge circuit, and a voltage comparison circuit;

[0007] The input terminal of the bias current source is connected to the output terminal of the drive branch that drives the IGBT;

[0008] The input terminal of the discharge circuit is connected to the output terminal of the bias current source, and the output terminal of the discharge circuit is connected to the collector of the IGBT, which is used to provide a discharge channel for the bias current source when the IGBT is turned on.

[0009] The first input terminal of the voltage comparison circuit is connected to the input terminal of the discharge circuit and the output terminal of the bias current source, respectively, and is used to compare the first voltage signal input to the first input terminal and the reference voltage signal input to the second input terminal to detect whether the IGBT has a short circuit.

[0010] In some embodiments, the bias current source includes a protection filter circuit and a pull-up resistor; the protection filter circuit includes a first filter capacitor; one end of the pull-up resistor is connected to the output terminal of the drive branch, and the other end of the pull-up resistor is connected to the first filter capacitor;

[0011] The connection points of the pull-up resistor and the first filter capacitor are respectively connected to the input terminal of the discharge circuit and the first input terminal of the voltage comparison circuit.

[0012] In some embodiments, the protection filter circuit further includes a first Zener diode; the first filter capacitor is connected in parallel with the first Zener diode, the anode of the first Zener diode is connected to the DC negative bus, and the cathode of the first Zener diode is connected to the pull-up resistor.

[0013] In some embodiments, the discharge circuit includes a first diode and a first current-limiting resistor connected in series;

[0014] One end of the first current-limiting resistor is connected to the anode of the first diode, and the other end of the first current-limiting resistor is connected to the output terminal of the bias current source and the first input terminal of the voltage comparison circuit, respectively; the cathode of the first diode is connected to the collector of the IGBT.

[0015] In some embodiments, the voltage comparison circuit includes a reference voltage circuit, an input filter circuit, and a voltage comparator;

[0016] The reference voltage circuit is connected to the second input terminal of the voltage comparator to provide a reference voltage signal;

[0017] The input filter circuit is connected to the first input terminal of the voltage comparator and is used to receive the first voltage signal and input the first voltage signal into the first input terminal.

[0018] In some embodiments, the reference voltage circuit includes a second current-limiting resistor, a second Zener diode, and a second filter capacitor;

[0019] One end of the second current-limiting resistor is connected to the positive power supply of the voltage comparator, the other end of the second current-limiting resistor and the cathode of the second Zener diode are connected to the second input terminal of the voltage comparator, the anode of the second Zener diode is connected to the negative power supply of the voltage comparator, and the second filter capacitor is connected in parallel across the second Zener diode.

[0020] In some embodiments, the input filter circuit includes a resistor connected in series between the discharge circuit and the first input terminal, and a capacitor connected in parallel between the positive and negative power supply terminals of the voltage comparator.

[0021] In some embodiments, the voltage comparator circuit further includes an input protection circuit; the input protection circuit includes two switching diodes whose cathodes and anodes are connected to each other, and the connection point between the cathodes and anodes of the switching diodes is connected to the first input terminal of the voltage comparator.

[0022] In some embodiments, the short-circuit detection circuit further includes an output unit connected to the output terminal of the voltage comparison circuit;

[0023] The output unit includes an optocoupler.

[0024] Secondly, this embodiment provides a frequency converter, including: a DC positive bus, a DC negative bus, a control unit, a drive branch, at least one set of IGBT modules, and the IGBT short-circuit detection circuit described in the first aspect;

[0025] The IGBT modules are connected in parallel between the DC positive bus and the DC negative bus; the IGBT short-circuit detection circuit is connected to each group of IGBT modules and is used to perform short-circuit detection of the inverter output;

[0026] One end of the control unit is connected to the control terminal of the IGBT in the IGBT module via the drive branch, and the other end of the control unit is connected to the output terminal of the IGBT short-circuit detection circuit. The control unit is used to control the IGBT module to turn on or off according to the output signal of the output terminal via the drive branch.

[0027] Compared with related technologies, the IGBT short-circuit detection circuit and inverter provided in this embodiment include a bias current source, a discharge circuit, and a voltage comparison circuit. The input terminal of the bias current source is connected to the output terminal of the drive branch driving the IGBT. The input terminal of the discharge circuit is connected to the output terminal of the bias current source, and the output terminal of the discharge circuit is connected to the collector of the IGBT, providing a discharge channel for the bias current source when the IGBT is turned on. The first input terminal of the voltage comparison circuit is connected to the input terminal of the discharge circuit and the output terminal of the bias current source, respectively, and is used to compare the first voltage signal input at the first input terminal and the reference voltage signal input at the second input terminal to detect whether the IGBT is short-circuited. Through this embodiment, the drive branch provides a bias voltage to the bias current source when driving the IGBT to turn on, enabling short-circuit detection by providing a bias voltage when the IGBT is turned on. The detection circuit does not work when the IGBT is turned off, thereby reducing the power consumption of the resistor on the bias current source and the risk of false triggering, providing stronger anti-interference capability, and solving the problems of high power consumption and easy false detection.

[0028] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0029] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0030] Figure 1 This is a schematic diagram of the IGBT short-circuit detection circuit in one embodiment;

[0031] Figure 2 This is a schematic diagram of the inverter structure in one embodiment;

[0032] Figure 3 This is a circuit diagram of a frequency converter in one embodiment.

[0033] In the diagram: 1. IGBT short-circuit detection circuit; 11. Bias current source; 12. Discharge circuit; 13. Voltage comparison circuit; 14. Output unit; 2. Inverter; 21. Control unit; 22. Drive branch; 23. IGBT module. Detailed Implementation

[0034] To better understand the purpose, technical solution, and advantages of this application, the application is described and explained below in conjunction with the accompanying drawings and embodiments.

[0035] Unless otherwise defined, the technical or scientific terms used in this application shall have the general meaning as understood by one of ordinary skill in the art to which this application pertains. Words such as “a,” “an,” “an,” “the,” “the,” and “these,” used in this application, do not indicate quantitative limitation and may be singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or modules (units) is not limited to the listed steps or modules (units) but may include steps or modules (units) not listed, or may include other steps or modules (units) inherent to such processes, methods, products, or devices. The terms “connected,” “linked,” and “coupled,” used in this application, are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. The term “multiple” used in this application refers to two or more. The "and / or" operator describes the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: A alone, A and B simultaneously, and B alone. Typically, the character " / " indicates that the objects before and after it are in an "or" relationship. The terms "first," "second," and "third," etc., used in this application are merely for distinguishing similar objects and do not represent a specific ordering of the objects.

[0036] Figure 1 This is a schematic diagram of the IGBT short-circuit detection circuit in this embodiment, as shown below. Figure 1 As shown, the IGBT short-circuit detection circuit 1 includes a bias current source 11, a discharge circuit 12, and a voltage comparison circuit 13.

[0037] The input terminal of the bias current source 11 is connected to the output terminal of the drive branch that drives the IGBTs (Q1, Q2); the input terminal of the discharge circuit is connected to the output terminal of the bias current source, and the output terminal of the discharge circuit is connected to the collector of the IGBT, which is used to provide a discharge path for the bias current source when the IGBT is turned on; the first input terminal of the voltage comparison circuit is connected to the input terminal of the discharge circuit and the output terminal of the bias current source, respectively, and is used to compare the first voltage signal input to the first input terminal and the reference voltage signal input to the second input terminal to detect whether the IGBT is short-circuited.

[0038] Specifically, this short-circuit detection circuit is suitable for IGBTs where the drive branch is connected to its control terminal and the discharge circuit is connected to its collector. When the drive branch drives the IGBT, it also provides a bias voltage to the bias current source 11 to provide a bias voltage for short-circuit detection when the IGBT is turned on. When the IGBT is turned off, the short-circuit detection circuit does not work and cannot perform short-circuit detection, thereby reducing the power consumption of the resistor on the bias current source 11 and the risk of false triggering, and improving the anti-interference capability.

[0039] The discharge circuit 12 is connected between the bias current source 11 and the voltage comparator circuit 13, and is also connected to the collector of the IGBT. The discharge circuit 12 provides a discharge path for the bias current source 11 only when the IGBT is turned on, i.e., when the IGBT is not short-circuited. The first input terminal of the voltage comparator circuit 13 is connected to both the discharge circuit 12 and the output terminal of the bias current source 11. When the bias current source 11 outputs power, it monitors the first voltage signal input to its first input terminal and combines it with the reference voltage signal input to its second input terminal to detect whether the IGBT is short-circuited. The first voltage signal is the voltage after the bias voltage of the bias current source 11 has passed through the discharge circuit 12. The reference voltage signal is a reference voltage signal used for comparison with the input first voltage signal and can be provided by a reference voltage circuit, a voltage regulator chip, etc.

[0040] Taking the first input terminal as the non-inverting input terminal and the second input terminal as the inverting input terminal as an example, when the IGBT is turned on in the drive branch, the bias current source 11 input terminal receives the bias voltage, and the voltage at the first input terminal of the voltage comparator circuit 13 begins to rise slowly. When the IGBT is not short-circuited, the voltage drop across the drain and source terminals of the IGBT drops rapidly, reaching the saturation conduction state. At this time, the discharge circuit 12 provides a discharge channel for the bias current source 11 through the IGBT, and the first voltage signal at the first input terminal of the voltage comparator circuit 13 no longer rises. This voltage value cannot exceed the reference voltage signal at the second input terminal of the voltage comparator circuit 13, so the output voltage of the voltage comparator circuit 13 remains at a low level, indicating that the IGBT is not short-circuited. When an IGBT short-circuits, a very large current flows through the drain and source terminals, causing the voltage across the drain and source terminals to rise rapidly. The voltage rise is much greater than the bias voltage provided by the bias current source 11, and the discharge circuit 12 cannot provide a discharge path for the bias current source 11. This causes the first voltage signal at the first input terminal of the voltage comparator circuit 13 to rise continuously until it equals the bias voltage of the bias current source 11. This voltage value will exceed the reference voltage signal at the second input terminal of the voltage comparator circuit 13, causing the output voltage of the voltage comparator circuit 13 to change from low level to high level. This indicates that the IGBT has experienced an output short circuit. The circuit is simple, effective, and low in cost.

[0041] This embodiment provides a frequency converter. Figure 2 This is a schematic diagram of the inverter structure in this embodiment, as shown below. Figure 2 As shown, the frequency converter 2 includes: a DC positive bus P+, a DC negative bus N-, a control unit 21, a drive branch 22, at least one set of IGBT modules 23, and an IGBT short-circuit detection circuit 1.

[0042] IGBT module 23 is connected in parallel between DC positive bus P+ and DC negative bus N-; IGBT short circuit detection circuit 1 is connected to each group of IGBT modules 23 and is used to perform short circuit detection of the inverter output;

[0043] One end of the control unit 21 is connected to the control terminal of the IGBT in the IGBT module 23 via the drive branch 22, and the other end of the control unit 21 is connected to the output terminal of the IGBT short circuit detection circuit 1. It is used to control the IGBT module 23 to turn on or off according to the output signal of the output terminal via the drive branch 22.

[0044] In order to achieve short-circuit detection in three cases during the three-phase inverter operation of inverter 2: short circuit between output phase U and phase V, short circuit between phase V and phase W, and short circuit between phase W and phase U, inverter 2 in this embodiment includes three sets of IGBT modules 23. Figure 2 Only one IGBT module is shown in the diagram. Each IGBT module includes two IGBTs connected in series and then in parallel between the DC positive bus P+ and the DC negative bus N-, which are the upper bridge IGBT and the lower bridge IGBT, respectively. Each IGBT module 23 is connected to a corresponding IGBT short-circuit detection circuit 1. Specifically, the IGBT short-circuit detection circuit 1 is connected to the series connection point of the two IGBTs in the IGBT module and is used to perform short-circuit detection of the inverter output.

[0045] One end of the control unit 21 is connected to the control terminal of the IGBT in the IGBT module 23 via the drive branch 22, controlling the IGBT module 23 to turn on or off. The other end of the control unit 21 is connected to the output terminal of the IGBT short-circuit detection circuit 1, which provides a short-circuit signal to the control unit 21. It can be understood that when the IGBT short-circuit detection circuit 1 includes an output unit 14, the output terminal of the IGBT short-circuit detection circuit 1 is the output terminal of the output unit 14; otherwise, it is the output terminal of the voltage comparator circuit 13. The control unit 21 includes a control chip that generates control signals based on system operating requirements, feedback signals (such as motor speed and current), and a preset control algorithm. These control signals contain key information such as the timing, frequency, and duty cycle of the IGBT turn-on and turn-off. The drive branch 22 is connected to the control unit 21, and the drive chip can amplify the control signals output by the control unit 21, using high and low levels to drive the IGBT to turn on or off.

[0046] The output of drive branch 22 is connected to the input of bias current source 11 in IGBT short-circuit detection circuit 1. When drive branch 22 controls IGBT module 23 to turn on, it provides bias voltage to the bias current source to start short-circuit detection of the inverter output. When no short circuit occurs, the output of IGBT short-circuit detection circuit 1 remains high. When a short circuit occurs, IGBT short-circuit detection circuit 1 outputs low. After receiving the low level, control unit 21 controls drive branch 22 to turn off IGBT module 23, stopping the inverter output for short-circuit protection.

[0047] The IGBT short-circuit detection circuit provided in this embodiment can achieve short-circuit detection of IGBTs and even frequency converters in a simple, effective, and low-cost manner. At the same time, when the drive branch drives the IGBT to conduct, it also provides a bias voltage to the bias current source to provide a bias voltage for short-circuit detection when the IGBT is conducting. When the IGBT is off, the detection circuit does not work and cannot perform short-circuit detection. This can reduce the power consumption of the resistor on the bias current source and the risk of false triggering, and has stronger anti-interference ability, solving the current problems of high power consumption and easy false detection.

[0048] In some embodiments, the IGBT short-circuit detection circuit 1 further includes an output unit 14, which is connected to the output terminal of the voltage comparison circuit 13; the output unit 14 includes an optocoupler.

[0049] Specifically, when the IGBT is not short-circuited, the output voltage of the voltage comparator circuit 13 remains at a low level, and the input terminal of the output unit 14 remains at a low level, so the LED of the optocoupler is not lit. Therefore, the signal output by the output unit 14 to the control unit 21 remains at a high level. When the IGBT is short-circuited, the output voltage of the voltage comparator circuit 13 changes from a low level to a high level, lighting the LED of the optocoupler. Therefore, the signal output by the output unit 14 to the control unit 21 changes from a high level to a low level. After receiving the low level signal from the output unit 14, the control unit 21 controls the drive branch 22 to turn off the IGBT. For example, the optocoupler can be a high-speed optocoupler.

[0050] The output unit configured in this embodiment can, when an IGBT output short circuit is detected, provide feedback to the control unit to shut down the IGBT for circuit protection based on the short circuit signal output by the voltage comparison circuit.

[0051] Figure 3 This is a circuit diagram of the inverter in this embodiment. In some embodiments, such as... Figure 3As shown, the bias current source 11 includes a protection filter circuit and multiple pull-up resistors R7 and R8; the protection filter circuit includes a first filter capacitor C2; one end of the pull-up resistors R7 and R8 is connected to the output terminal of the drive branch, and the other end of the pull-up resistors is connected to the first filter capacitor C2; the connection point of the pull-up resistors R7 and R8 and the first filter capacitor C2 is connected to the input terminal of the discharge circuit and the first input terminal of the voltage comparison circuit, respectively.

[0052] In some embodiments, the protection filter circuit further includes a first Zener diode ZD1; a first filter capacitor C1 is connected in parallel with the first Zener diode ZD1, the anode of the first Zener diode ZD1 is connected to the DC negative bus N-, and the cathode of the first Zener diode ZD1 is connected to pull-up resistors R7 and R8 to control the first voltage signal to prevent overvoltage.

[0053] In some of these embodiments, such as Figure 3 As shown, the discharge circuit 12 includes a first diode D1, D2 and a first current-limiting resistor R4 connected in series. The first diode may include one or more. One end of the first current-limiting resistor R4 is connected to the anode of the first diode, and the other end of the first current-limiting resistor R4 is connected to the cathode of the first Zener diode ZD1 in the bias current source 11 and the input terminal of the voltage comparator circuit 13, respectively. The cathode of the first diode is connected to the collector of the lower bridge IGBT in the IGBT module 23.

[0054] When the drive branch 22 turns on the IGBT module 23 under the control of the control unit 21, the input terminal of the bias current source 11 receives the bias voltage and begins to charge the first filter capacitor C2. The voltage at the first input terminal of the voltage comparison circuit 13 begins to rise slowly. During the charging process of the first filter capacitor C2, when the inverter 2 is not short-circuited, the voltage drop across the drain and source terminals of the lower bridge IGBT in the IGBT module 23 drops rapidly and reaches the saturation conduction state. At this time, the discharge circuit 12 provides a discharge channel for the bias current source 11 through the lower bridge IGBT of the IGBT module 23. The voltage of the first filter capacitor C2 and the first voltage signal at the first input terminal of the voltage comparison circuit 13 no longer rise. At this time, the voltage value of the first voltage signal is the sum of the saturation voltage drop of the lower bridge IGBT (Q2), the forward voltage drop of the first diode, and the voltage drop of the first current limiting resistor R4. This voltage value cannot exceed the reference voltage signal at the second input terminal of the voltage comparison circuit 13, and the output voltage of the voltage comparison circuit 13 remains at a low level. When a short circuit occurs in inverter 2, a very large current will flow through the drain and source terminals of the lower bridge IGBT of IGBT module 23. This causes the voltage across the drain and source terminals to rise rapidly. The voltage rise across the drain and source terminals is much greater than the bias voltage provided by the bias current source 11, causing the first diode in the discharge circuit 12 to be reverse cut off, unable to provide a discharge path for the bias current source 11. This causes the voltage of the first filter capacitor C2 and the first voltage signal at the first input terminal of the voltage comparison circuit 13 to rise continuously until they are equal to the bias voltage of the bias current source 11. This voltage value will exceed the reference voltage signal at the second input terminal of the voltage comparison circuit 13, causing the output voltage of the voltage comparison circuit 13 to change from low level to high level. This indicates that an output short circuit has occurred in inverter 2.

[0055] In some cases, due to improper design of the detection circuit, especially when a dual-level conversion unit is used to provide a dual-level voltage to the drive branch, the positive voltage of the dual-level voltage is usually the positive power supply voltage of the dual-level conversion unit, which is higher than the voltage of the DC negative bus N-. The negative voltage of the dual-level voltage is usually the power supply ground of the dual-level conversion unit, which is lower than the voltage of the DC negative bus N-. The output of the dual-level conversion unit is finally output to the IGBT module through the drive branch. When the control unit controls the drive branch to turn off the IGBT module, the drive branch outputs the negative voltage of the aforementioned dual-level conversion unit. In the above scheme, this negative voltage will be input to the first input terminal of the voltage comparison circuit through the bias current source. If the power supply ground of the voltage comparison circuit is the DC negative bus N- at this time, this negative voltage will cause the voltage comparison circuit to malfunction, or even damage the voltage comparison circuit and the entire detection circuit.

[0056] Based on this, a first Zener diode ZD1 is set in the bias current source 11, with its anode connected to the DC negative bus N- and its cathode connected to the drive branch 22. In this way, when the drive branch 22 outputs a negative voltage lower than the DC negative bus N-, the DC negative bus N- forms a discharge branch with the drive branch 22 through the bias current source 11. This clamps the first voltage signal at the first input terminal of the voltage comparator circuit 13 to a stable voltage value by the first Zener diode ZD1. This voltage value is the voltage of the DC negative bus N- minus the normal voltage drop of the first Zener diode ZD1 and the bias voltage of the bias current source 11. Furthermore, this voltage value is higher than the power supply ground of the voltage comparator circuit 13, preventing overvoltage damage to the detection circuit at the input terminal of the voltage comparator circuit 13, protecting the input pin of the voltage comparator in the voltage comparator circuit, and improving the anti-interference and stability of the circuit.

[0057] The bias current source and discharge circuit in this embodiment can provide a first voltage signal at the input terminal of the voltage comparison circuit to be compared with the reference voltage signal to detect whether there is a short circuit at the inverter output.

[0058] In some of these embodiments, such as Figure 3 As shown, the voltage comparison circuit 13 includes a reference voltage circuit, an input filter circuit, and a voltage comparator; the reference voltage circuit is connected to the second input terminal of the voltage comparator to provide a reference voltage signal; the input filter circuit is connected to the first input terminal of the voltage comparator to receive the first voltage signal from the discharge circuit 12 and the bias current source 11 and input the first voltage signal to the first input terminal.

[0059] The voltage comparator circuit 13 also includes an input protection circuit; the input protection circuit includes two switching diodes D3 whose cathodes and anodes are connected to each other, and the connection point between the cathodes and anodes of the switching diodes is connected to the first input terminal of the voltage comparator.

[0060] The reference voltage circuit includes a second current-limiting resistor R1, a second Zener diode Z1, and a second filter capacitor C1. One end of the second current-limiting resistor R1 is connected to the positive terminal VCC of the power supply, and the other end of the second current-limiting resistor R1 is connected to the cathode of the second Zener diode Z1. The cathode of the second Zener diode Z1 is connected to the second input terminal of the voltage comparator U1A, and the anode of the second Zener diode Z1 is connected to the DC negative bus N-. The second filter capacitor C1 is connected in parallel across the second Zener diode Z1.

[0061] The input filter circuit includes a resistor R5 connected in series between the discharge circuit 12 and the first input terminal, and capacitors C5 and C6 connected in parallel between the positive power supply VCC of the voltage comparator U1A and the negative DC bus N-.

[0062] Specifically, in the reference voltage circuit, the positive terminal of the power supply VCC is connected to the Zener diode Z1 through the current-limiting resistor R1, so that the Zener diode Z1 operates in the reverse breakdown region. The stable voltage across its two ends, after processing, can be used as a reference voltage signal input to the second input terminal of the voltage comparator U1A.

[0063] The voltage comparator can be a voltage comparator chip U1A, which is used to compare a reference voltage signal and a first voltage signal. When the reference voltage signal at the second input terminal is higher than the first voltage signal at the first input terminal, the voltage comparator chip U1A outputs a low level, and vice versa.

[0064] In some of these embodiments, such as Figure 3 As shown, the output unit 14 includes a high-speed optocoupler U2. The anode of the light-emitting diode in the high-speed optocoupler U2 is connected to the positive voltage VCC through a resistor R3, and is also connected to the output terminal of the voltage comparator U1A. The cathode of the light-emitting diode is connected in parallel with the DC negative bus N- through a capacitor C4 and a resistor R6. The transistor side of the high-speed optocoupler U2 is connected to the drive power supply VDD and the power ground GND through a resistor R2 and a capacitor C3, and is also connected to the control unit 21 to provide a short-circuit signal.

[0065] The present embodiment will now be described and illustrated through preferred embodiments.

[0066] like Figure 3 As shown, the inverter 2 in this embodiment includes: a DC positive bus P+, a DC negative bus N-, a control unit 21, a drive branch 22, at least one IGBT module 23, and an IGBT short-circuit detection circuit 1.

[0067] To enable short-circuit detection in the three-phase inverter of inverter 2 for three scenarios: short circuit between phase U and phase V, short circuit between phase V and phase W, and short circuit between phase W and phase U, inverter 2 includes three sets of IGBT modules 23. Each set of IGBT modules 23 includes two IGBTs connected in series and then in parallel between the DC positive bus P+ and the DC negative bus N-, namely the upper bridge IGBT (Q1) and the lower bridge IGBT (Q2). Each set of IGBT modules 23 is connected to a corresponding IGBT short-circuit detection circuit 1, which is specifically connected to the collector of the IGBT in the IGBT module for short-circuit detection of the inverter output.

[0068] The control unit 21 includes a control chip, a drive power supply connected to VDD, and ground GND. One end of the control unit 21 is connected to the control terminal of the lower bridge IGBT in the IGBT module 23 via a drive branch 22. The drive branch 22 controls the IGBT module 23 to turn on or off. The drive branch 22 includes a drive chip U3, whose pins 6 and 4 are connected to the positive power supply VCC and the negative DC bus N-, respectively. The other end of the control unit 21 is connected to the output unit 14 of the IGBT short-circuit detection circuit 1, which provides a short-circuit signal to the control unit 21. The output terminal of the drive branch 22 is connected to the input terminal of the bias current source in the IGBT short-circuit detection circuit 1. When the drive branch 22 controls the IGBT module 23 to turn on, it provides a bias voltage to the bias current source to initiate the short-circuit detection of the inverter output.

[0069] The IGBT short-circuit detection circuit 1 includes a bias current source 11, a discharge circuit 12, a voltage comparison circuit 13, and an output unit 14.

[0070] The bias current source 11 includes a first Zener diode ZD1, a first filter capacitor C2, and multiple pull-up resistors R7 and R8. One end of the pull-up resistor is connected to the output terminal of the drive branch 22, and the other end is connected to the cathode of the first Zener diode ZD1. The first filter capacitor C2 is connected in parallel with the first Zener diode ZD1. The anode of the first Zener diode ZD1 is connected to the DC negative bus N-, and the cathode is connected to the output terminal of the drive branch 22. The discharge circuit 12 includes a first diode D1 and D2 connected in series and a first current-limiting resistor R4. One end of the first current-limiting resistor R4 is connected to the anode of the first diode, and the other end is connected to the cathode of the first Zener diode ZD1 in the bias current source 11 and the input terminal of the voltage comparator circuit 13, respectively. The cathode of the first diode is connected to the collector of the IGBT in the IGBT module 23.

[0071] The voltage comparison circuit 13 includes a reference voltage circuit, an input filter circuit, an input protection circuit, and a voltage comparator chip U1A. The reference voltage circuit is connected to the second input terminal of the voltage comparator chip U1A to provide a reference voltage signal; the input filter circuit is connected to the first input terminal of the voltage comparator chip U1A to receive the first voltage signal from the discharge circuit 12 and the bias current source 11 and input the first voltage signal to the first input terminal; the input protection circuit includes two switching diodes D3 with their cathodes and anodes connected to each other, and the connection point between the cathodes and anodes of the switching diodes is connected to the first input terminal of the voltage comparator chip U1A.

[0072] The reference voltage circuit includes a second current-limiting resistor R1, a second Zener diode Z1, and a second filter capacitor C1. One end of the second current-limiting resistor R1 is connected to the positive terminal VCC of the power supply, and the other end of the second current-limiting resistor R1 is connected to the cathode of the second Zener diode Z1. The cathode of the second Zener diode Z1 is connected to the second input terminal of the voltage comparator chip U1A, and the anode of the second Zener diode Z1 is connected to the DC negative bus N-. The second filter capacitor C1 is connected in parallel across the second Zener diode Z1.

[0073] The input filter circuit includes a resistor R5 connected in series between the discharge circuit 12 and the first input terminal, and capacitors C5 and C6 connected in parallel to the positive power supply VCC and the negative DC bus N- of the voltage comparator chip U1A.

[0074] The voltage comparator chip U1A compares the reference voltage signal and the first voltage signal. When the reference voltage signal at the second input terminal is higher than the first voltage signal at the first input terminal, the voltage comparator chip U1A outputs a low level, and vice versa.

[0075] Output unit 14 includes a high-speed optocoupler U2. The anode of the light-emitting diode in the high-speed optocoupler U2 is connected to the positive voltage VCC through resistor R3, and is also connected to the output terminal of voltage comparator chip U1A. The cathode of the light-emitting diode is connected in parallel with capacitor C4 and resistor R6 between the DC negative bus N-. The transistor side of the high-speed optocoupler U2 is connected to the drive power supply VDD and power ground GND through resistor R2 and capacitor C3, and is also connected to control unit 21 to provide a short-circuit signal.

[0076] In IGBT module 23, the gate (G) of the lower IGBT is connected to the output terminal of the drive branch 22 through resistor RB1. It also includes a diode ZD2 whose cathode is connected between resistor RB1 and the gate (G). The anode of diode ZD2 is connected between the emitter (E) of the lower IGBT and the DC negative bus N-. Resistor R11 and capacitor C8 are also connected in parallel with diode ZD2.

[0077] When the drive branch 22 turns on the IGBT module 23 under the control of the control unit 21, the input terminal of the bias current source 11 receives a bias voltage and begins to charge the first filter capacitor C2. The voltage at the first input terminal of the voltage comparator circuit 13 begins to rise slowly. During the charging process of the first filter capacitor C2, when the inverter 2 is not short-circuited, the voltage drop across the drain and source of the lower bridge IGBT in the IGBT module 23 drops rapidly, reaching a saturation conduction state. At this time, the discharge circuit 12 provides a discharge path for the bias current source 11 through the lower bridge IGBT of the IGBT module 23. The first voltage signal at the first input terminal of voltage comparator circuit 13 no longer rises. At this time, the voltage value of the first voltage signal is the sum of the saturation voltage drop of the lower bridge IGBT (Q2), the forward voltage drop of the first diodes D1 and D2, and the voltage drop of the current limiting resistor R4. This voltage value cannot exceed the reference voltage signal at the second input terminal of voltage comparator circuit 13. The output voltage of voltage comparator circuit 13 remains low. The input terminal of output unit 14 is still low, and the light-emitting diode of high-speed optocoupler U2 cannot be lit. Therefore, the signal output by output unit 14 to control unit 21 remains high.

[0078] When a short circuit occurs in inverter 2, a very large current flows through the drain and source terminals of the lower bridge IGBT of IGBT module 23. This causes the voltage across the drain and source terminals to rise rapidly. The voltage rise across the drain and source terminals is much greater than the bias voltage provided by the bias current source 11. This causes the first diodes D1 and D2 in the discharge circuit 12 to be reverse cut off, unable to provide a discharge path for the bias current source 11. This causes the voltage of the first filter capacitor C2 and the first voltage signal at the first input terminal of the voltage comparison circuit 13 to rise continuously until they are equal to the bias voltage of the bias current source 11. This voltage value will exceed the reference voltage signal at the second input terminal of the voltage comparison circuit 13, causing the output voltage of the voltage comparison circuit 13 to change from low level to high level. The input terminal of the output unit 14 changes from low level to high level, lighting up the LED of the high-speed optocoupler U2. Therefore, the signal output by the output unit 14 to the control unit 21 changes from high level to low level. After the control unit 21 receives the voltage of the output unit 14 changing to low level, it indicates that an output short circuit has occurred in inverter 2, and controls the drive branch 22 to stop the output of inverter 2.

[0079] The IGBT short-circuit detection circuit and inverter in this embodiment provide a simple, effective, and cost-efficient way to detect short circuits at the inverter output. Furthermore, by adding a Zener diode to the bias current source, with its anode connected to the inverter's DC negative bus and its cathode connected to the input of the drive branch, the first voltage signal is clamped. This prevents the short-circuit detection circuit from being damaged due to overvoltage of the first voltage signal from the input voltage comparator circuit, thus solving the problem of improper design leading to abnormal circuit damage. Additionally, when the drive branch turns on the IGBT module under the control of the control unit, it also provides a bias voltage to the bias current source. This bias voltage is used for short-circuit detection when the IGBT is on, and the short-circuit detection circuit does not operate when the IGBT is off. This reduces the power consumption of the resistor on the bias current source and the risk of false triggering, resulting in stronger anti-interference capabilities.

[0080] It should be understood that the specific embodiments described herein are merely illustrative of the application and not intended to limit it. All other embodiments derived by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0081] Obviously, the accompanying drawings are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar situations based on these drawings without any creative effort. Furthermore, it is understood that although the work done in this development process may be complex and lengthy, for those skilled in the art, certain design, manufacturing, or production modifications made based on the technical content disclosed in this application are merely conventional technical means and should not be considered as insufficient disclosure of this application.

[0082] The term "embodiment" in this application refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily imply the same embodiment, nor does it imply that it is mutually exclusive with or alternative to other embodiments. It will be clearly or implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0083] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. An IGBT short-circuit detection circuit, characterized in that, Includes a bias current source, a discharge circuit, and a voltage comparison circuit; The input terminal of the bias current source is connected to the output terminal of the drive branch that drives the IGBT; The input terminal of the discharge circuit is connected to the output terminal of the bias current source, and the output terminal of the discharge circuit is connected to the collector of the IGBT, which is used to provide a discharge channel for the bias current source when the IGBT is turned on. The first input terminal of the voltage comparison circuit is connected to the input terminal of the discharge circuit and the output terminal of the bias current source, respectively, and is used to compare the first voltage signal input to the first input terminal and the reference voltage signal input to the second input terminal to detect whether the IGBT has a short circuit.

2. The IGBT short-circuit detection circuit according to claim 1, characterized in that, The bias current source includes a protection filter circuit and a pull-up resistor; the protection filter circuit includes a first filter capacitor; one end of the pull-up resistor is connected to the output terminal of the drive branch, and the other end of the pull-up resistor is connected to the first filter capacitor; The connection points of the pull-up resistor and the first filter capacitor are respectively connected to the input terminal of the discharge circuit and the first input terminal of the voltage comparison circuit.

3. The IGBT short-circuit detection circuit according to claim 2, characterized in that, The protection filter circuit further includes a first Zener diode; the first filter capacitor is connected in parallel with the first Zener diode, the anode of the first Zener diode is connected to the DC negative bus, and the cathode of the first Zener diode is connected to the pull-up resistor.

4. The IGBT short-circuit detection circuit according to claim 1, characterized in that, The discharge circuit includes a first diode and a first current-limiting resistor connected in series; One end of the first current-limiting resistor is connected to the anode of the first diode, and the other end of the first current-limiting resistor is connected to the output terminal of the bias current source and the first input terminal of the voltage comparison circuit, respectively; the cathode of the first diode is connected to the collector of the IGBT.

5. The IGBT short-circuit detection circuit according to claim 1, characterized in that, The voltage comparison circuit includes a reference voltage circuit, an input filter circuit, and a voltage comparator; The reference voltage circuit is connected to the second input terminal of the voltage comparator to provide a reference voltage signal; The input filter circuit is connected to the first input terminal of the voltage comparator and is used to receive the first voltage signal and input the first voltage signal into the first input terminal.

6. The IGBT short-circuit detection circuit according to claim 5, characterized in that, The reference voltage circuit includes a second current-limiting resistor, a second Zener diode, and a second filter capacitor. One end of the second current-limiting resistor is connected to the positive power supply of the voltage comparator, the other end of the second current-limiting resistor and the cathode of the second Zener diode are connected to the second input terminal of the voltage comparator, the anode of the second Zener diode is connected to the negative power supply of the voltage comparator, and the second filter capacitor is connected in parallel across the second Zener diode.

7. The IGBT short-circuit detection circuit according to claim 5, characterized in that, The input filter circuit includes a resistor connected in series between the discharge circuit and the first input terminal, and a capacitor connected in parallel between the positive and negative terminals of the power supply of the voltage comparator.

8. The IGBT short-circuit detection circuit according to claim 5, characterized in that, The voltage comparison circuit also includes an input protection circuit; the input protection circuit includes two switching diodes whose cathodes and anodes are connected to each other, and the connection point between the cathodes and anodes of the switching diodes is connected to the first input terminal of the voltage comparator.

9. The IGBT short-circuit detection circuit according to claim 1, characterized in that, The short-circuit detection circuit also includes an output unit connected to the output terminal of the voltage comparison circuit; The output unit includes an optocoupler.

10. A frequency converter, characterized in that, include: A DC positive bus, a DC negative bus, a control unit, a drive branch, at least one set of IGBT modules, and the IGBT short-circuit detection circuit according to any one of claims 1 to 9; The IGBT modules are connected in parallel between the DC positive bus and the DC negative bus; the IGBT short-circuit detection circuit is connected to each group of IGBT modules and is used to perform short-circuit detection of the inverter output; One end of the control unit is connected to the control terminal of the IGBT in the IGBT module via the drive branch, and the other end of the control unit is connected to the output terminal of the IGBT short-circuit detection circuit. The control unit is used to control the IGBT module to turn on or off according to the output signal of the output terminal via the drive branch.

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