Overcurrent protection device of NPC I-type three-level circuit test circuit

Abstract

The utility model belongs to the field of inverter circuits, and comprises an NPC I-type three-level circuit test circuit. The NPC I-type three-level circuit test circuit comprises a first capacitor C1 which is bridged between a positive electrode and a midpoint N, a second capacitor C2 which is bridged between a negative electrode and the midpoint N, and a first diode D1 and a second diode D2 which are connected in series and are bridged on two sides of two middle IGBTs of four IGBTs which are connected in sequence, the circuit also comprises an over-current resistor and a controller. The overcurrent resistor is arranged between a connection point of the first diode D1 and the second diode D2 of the NPC I type three-level circuit test circuit and a connection point of the first capacitor C1 and the second capacitor C2; and the controller is connected with the gate pole of each IGBT of the four IGBTs, is connected with the two ends of the overcurrent resistor, and is used for obtaining the magnitude of the current flowing through the overcurrent resistor so as to determine whether to close any one or more IGBTs when the current is too large. The IGBT protection circuit is used for protecting the test circuit from being burnt out due to the fact that the current is too large.

Description

Technical Field

[0001] The present application relates to the field of inverter circuits, and in particular to an overcurrent protection device for an NPC I type three-level circuit test circuit. Background Art

[0002] The NPC I type three-level circuit is a topology widely used in power converters, such as Figure 1 As shown. It has the advantages of high efficiency, low loss and the ability to achieve higher voltage and current. The structural feature of the NPC I type three-level circuit is that it realizes the output of three levels (positive level, zero level and negative level) by adding a clamping diode. In the NPC I type three-level circuit, when the upper bridge arm is turned on and the lower bridge arm is disconnected, the upper output voltage is a positive voltage; when the lower bridge arm is turned on and the upper bridge arm is disconnected, the upper output voltage is a negative voltage; when both the upper and lower bridge arms are disconnected, the upper output voltage is zero. The change in direction of the current through the midpoint capacitor is controlled by the control switch. Now, in order to ensure the safe use of the NPC I type three-level circuit, an NPC I type three-level circuit test circuit is designed, as shown Figure 2 However, when testing the IGBT in the NPC I type three-level circuit, there may be a problem of excessive current, which may cause the IGBT to burn out. Utility Model Content

[0003] In order to solve the technical problem of excessive current causing IGBT to burn out, the present application provides an overcurrent protection device for an NPC I type three-level circuit test circuit.

[0004] This application proposes an overcurrent protection device for an NPC I type three-level circuit test circuit, which adopts the following technical solution:

[0005] In a first aspect, an overcurrent protection device for an NPC I type three-level circuit test circuit is provided, comprising an NPC I type three-level circuit test circuit; the NPC I type three-level circuit test circuit comprises: a first capacitor C1 connected between a positive electrode and a midpoint N, a second capacitor C2 connected between a negative electrode and the midpoint N, a first diode D1 and a second diode D2 connected in series across two middle IGBTs of four sequentially connected IGBTs; an overcurrent resistor Rs, and a controller;

[0006] The overcurrent resistor Rs is provided between the connection point between the first diode D1 and the second diode D2 of the NPC I type three-level circuit test circuit and the connection point between the first capacitor C1 and the second capacitor C2;

[0007] The controller is connected to the gate of each of the four IGBTs and to both ends of the overcurrent resistor Rs, and is used to obtain the current flowing through the overcurrent resistor Rs to determine whether to turn off any one or more of the four IGBTs when the current is too large.

[0008] Preferably, it also includes: a comparator; the input end of the comparator is connected to the two ends of the overcurrent resistor Rs, and the output end of the comparator is connected to the input end of the controller; the comparator is used to obtain the voltage difference between the two ends of the overcurrent resistor Rs and send it to the controller, so that the controller can determine whether the current flowing through the overcurrent resistor Rs is too large.

[0009] Preferably, a first switch U1 and a first inductor L1 connected in series are provided between the connection point between the second IGBT and the third IGBT among the four sequentially connected IGBTs of the NPC I type three-level circuit test circuit and the connection point between the first diode D1 and the second diode D2.

[0010] Preferably, the controller is further configured to control the opening and closing of the first switch U1 through electrical connection.

[0011] Preferably, a second switch U2 and a second inductor L2 connected in series are connected in parallel on both sides of the first IGBT and the second IGBT of the four sequentially connected IGBTs of the NPC I type three-level circuit test circuit.

[0012] Preferably, the controller is further configured to control the opening and closing of the second switch U2 through electrical connection.

[0013] Preferably, a third switch U3 and a third inductor L3 connected in series are connected in parallel on both sides of the third IGBT and the fourth IGBT below the four sequentially connected IGBTs of the NPC I type three-level circuit test circuit.

[0014] Preferably, the controller is further configured to control the opening and closing of the third switch U3 through electrical connection.

[0015] Preferably, the controller includes any one of a CPU, a single chip microcomputer, an FPGA or a CPLD.

[0016] In a second aspect, a circuit board is provided, comprising an overcurrent protection device for an NPC I type three-level circuit test circuit as described in any one of the above technical solutions.

[0017] In summary, this application includes at least one of the following beneficial technical effects:

[0018] 1. Use the controller to obtain the current flowing through the overcurrent resistor Rs and determine whether to stop the test;

[0019] 2. Use the controller to obtain the current flowing through the overcurrent resistor Rs and determine whether to turn off the gate of any one or more of the four IGBTs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the NPC I type three-level circuit diagram;

[0021] Figure 2 This is the NPC I type three-level circuit test circuit diagram;

[0022] Figure 3 1 is a diagram of a first embodiment of an overcurrent protection device for an NPC I type three-level circuit test circuit;

[0023] Figure 4 2 is a diagram of a second embodiment of an overcurrent protection device for an NPC I type three-level circuit test circuit;

[0024] Figure 5 is a diagram of a third embodiment of an overcurrent protection device for an NPC I type three-level circuit test circuit;

[0025] Figure 6 is a diagram of a fourth embodiment of an overcurrent protection device for an NPC I type three-level circuit test circuit;

[0026] Figure 7 is a diagram of a fifth embodiment of an overcurrent protection device for an NPC I type three-level circuit test circuit;

[0027] Figure 8 is a sixth embodiment diagram of an overcurrent protection device for an NPC I type three-level circuit test circuit;

[0028] Figure 9 FIG7 is a seventh embodiment of an overcurrent protection device for an NPC I type three-level circuit test circuit;

[0029] Figure 10 FIG. 8 is a diagram of an eighth embodiment of an overcurrent protection device for an NPC I type three-level circuit test circuit. DETAILED DESCRIPTION

[0030] Explanation of terms:

[0031] NPC I type three-level circuit: NPC I type (Neutral Point Clamped) is a neutral point clamped circuit. It is also called a neutral-point-clamped inverter.

[0032] In the first aspect, the present application proposes an overcurrent protection device for an NPC I type three-level circuit test circuit, which adopts the following technical solution:

[0033] like Figure 3 As shown, an overcurrent protection device for an NPC I type three-level circuit test circuit includes an NPC I type three-level circuit test circuit; the NPC I type three-level circuit test circuit includes: a first capacitor C1 connected across a positive electrode and a midpoint N, a second capacitor C2 connected across a negative electrode and the midpoint N, a first diode D1 and a second diode D2 connected in series across two middle IGBTs of four sequentially connected IGBTs; an overcurrent resistor Rs, and a controller; the NPC I type three-level circuit has three power supply interfaces, namely a positive electrode, a negative electrode, and a negative electrode.

[0034] The overcurrent resistor Rs is disposed between the connection point of the first diode D1 and the second diode D2, and the connection point of the first capacitor C1 and the second capacitor C2, of the NPC I-type three-level circuit test circuit. The overcurrent resistor Rs is disposed at this location to detect the current flowing therethrough. If the current is excessive, it indicates that the current flowing through the IGBT under test is high, and if no further processing is performed, the IGBT under test may burn out. If the current does not exceed expectations, it indicates that the current flowing through the IGBT under test is low, and the circuit under test is operating normally.

[0035] The controller is connected to the gate of each of the four IGBTs and to both ends of the overcurrent resistor Rs, and is used to obtain the current flowing through the overcurrent resistor Rs to determine whether to shut down any one or more of the four IGBTs if the current is too high. The controller obtains the voltage across the overcurrent resistor Rs, then internally calculates the current value of the overcurrent resistor Rs and compares this current value with the preset maximum current value that the IGBT can withstand. If the current flowing through the overcurrent resistor Rs exceeds the maximum current value that the IGBT can withstand, the controller sends a low-level signal to the gate of the IGBT to shut it down, disconnecting the current loop of the tested circuit and preventing the IGBT from being burned by excessive current. If the current flowing through the overcurrent resistor Rs is less than the maximum current value that the IGBT can withstand, the controller does not need to send a low-level signal to the gate of the IGBT, and the test circuit operates normally.

[0036] Preferably, Figure 4As shown, the device further includes: a comparator; the input end of the comparator is connected to the two ends of the overcurrent resistor Rs, and the output end of the comparator is connected to the input end of the controller; the comparator is used to obtain the voltage difference across the overcurrent resistor Rs and send it to the controller, so that the controller can determine whether the current flowing through the overcurrent resistor Rs is too large. In this embodiment, the comparator is used to obtain the voltage value across the overcurrent resistor Rs, then compare and obtain the voltage drop, divide the voltage drop by the resistance value of the overcurrent resistor Rs, and obtain the current value flowing through the overcurrent resistor Rs, which is then sent to the controller. If the current value obtained by the comparator is greater than the maximum current value that the IGBT can withstand, the controller sends a low level to the gate of the IGBT, preventing current from flowing in the circuit under test and preventing the IGBT from burning out. If the current value obtained by the comparator is less than the maximum current value that the IGBT can withstand, the controller does not need to interfere with the current flow in the circuit under test and continues to test the function of the IGBT.

[0037] Preferably, Figure 5 、 Figure 6 As shown, a first switch U1 and a first inductor L1 are provided in series between the connection point between the second and third IGBTs among the four sequentially connected IGBTs of the NPC I-type three-level circuit test circuit and the connection point between the first diode D1 and the second diode D2. In this embodiment, if the current flowing through the overcurrent resistor Rs detected by the controller is too large, the first switch U1 can be manually disconnected to shut off the current flowing through Q1, Q2 or Q3, Q4 of the four IGBTs in sequence.

[0038] Preferably, the controller is further configured to control the opening and closing of the first switch U1 via an electrical connection. In this embodiment, the first switch U1 is controlled by the electrical connection of the controller. If the current flowing through the overcurrent resistor Rs received by the controller is too large, exceeding the maximum current that can be tolerated by Q1, Q2, or Q3, Q4 of the four IGBTs, the first switch U1 is controlled by the controller to open, thereby preventing Q1, Q2, or Q3, Q4 from burning out.

[0039] Preferably, Figure 7 、 Figure 8As shown, a second switch U2 and a second inductor L2 are connected in parallel on both sides of the first and second IGBTs of the four sequentially connected IGBTs in the NPC I-type three-level circuit test circuit. In this embodiment, the second switch U2 is closed. At this time, the current flows through L2, Q3, D2, and Rs in sequence. If the current flowing through the overcurrent resistor Rs exceeds the maximum current that Q3 can withstand, the second switch U2 is manually opened, thereby disconnecting the current flowing through L2, Q3, D2, and Rs in sequence. If the current flowing through the overcurrent resistor Rs does not exceed the maximum current that Q3 can withstand, the test of Q3 continues, and the second switch U2 remains closed.

[0040] Preferably, the controller is further configured to control the opening and closing of the second switch U2 via an electrical connection. In this embodiment, the controller is electrically connected to the second switch U2. If the current flowing through Q3 exceeds the maximum current it can withstand, that is, the current on the overcurrent resistor Rs exceeds a preset current, the controller controls the second switch U2 to open, thereby disconnecting the current loop that flows through L2, Q3, D2, and Rs in sequence.

[0041] Preferably, Figure 9 , Figure 10 As shown, a third switch U3 and a third inductor L3 are connected in series on both sides of the third and fourth IGBTs below the four sequentially connected IGBTs in the NPC I-type three-level circuit test circuit. In this embodiment, the third switch U3 is closed. At this time, the current flows through Rs, D1, Q2, and L3 in sequence. If the current flowing through the overcurrent resistor Rs exceeds the maximum current that Q2 can withstand, the third switch U3 is manually opened, thereby disconnecting the current flowing through Rs, D1, Q2, and L3 in sequence. If the current flowing through the overcurrent resistor Rs does not exceed the maximum current that Q2 can withstand, the test of Q2 continues, and the third switch U3 remains closed.

[0042] Preferably, the controller is further configured to control the opening and closing of the third switch U3 via an electrical connection. In this embodiment, the controller is electrically connected to the third switch U3. If the current flowing through Q2 exceeds the maximum current it can withstand, that is, the current on the overcurrent resistor Rs exceeds a preset current, the controller controls the third switch U3 to open, thereby disconnecting the current loop that flows through Rs, D1, Q2, and L3 in sequence.

[0043] Preferably, the controller includes any one of a CPU, a single chip microcomputer, an FPGA or a CPLD.

[0044] In a second aspect, a circuit board is provided, comprising an overcurrent protection device for an NPC I type three-level circuit test circuit as described in any one of the above technical solutions.

[0045] In this embodiment, the test current is usually 150A or 200A. When the current flowing through the overcurrent resistor Rs reaches 150A or 200A, the controller will control Q1, Q2, Q3, Q4 or U1, U2, U3 to be in the disconnected state to prevent Q1, Q2, Q3 or Q4 from burning.

[0046] In summary, this application includes at least one of the following beneficial technical effects:

[0047] 1. Use the controller to obtain the current flowing through the overcurrent resistor Rs and determine whether to stop the test;

[0048] 2. Use the controller to obtain the current flowing through the overcurrent resistor Rs and determine whether to turn off the gate of any one or more of the four IGBTs.

[0049] The above are all preferred embodiments of the present application and are not intended to limit the scope of protection of this application. Unless otherwise stated, any feature disclosed in this specification (including the abstract and drawings) may be replaced by other equivalent or similar features. In other words, unless otherwise stated, each feature is merely an example of a series of equivalent or similar features.

Claims

1. An overcurrent protection device for an NPCI type three-level circuit test circuit, comprising an NPCI type three-level circuit test circuit; the NPCI type three-level circuit test circuit comprising: A first capacitor C1 is connected across the positive electrode and the midpoint N, a second capacitor C2 is connected across the negative electrode and the midpoint N, and a first diode D1 and a second diode D2 are connected in series on both sides of the two middle IGBTs of the four sequentially connected IGBTs; characterized in that it also includes an overcurrent resistor Rs and a controller; The overcurrent resistor Rs is provided between the connection point between the first diode D1 and the second diode D2 of the NPCI type three-level circuit test circuit, and the connection point between the first capacitor C1 and the second capacitor C2; The controller is connected to the gate of each of the four IGBTs and to both ends of the overcurrent resistor Rs, and is used to obtain the current flowing through the overcurrent resistor Rs to determine whether to turn off any one or more of the four IGBTs when the current is too large.

2. The overcurrent protection device according to claim 1, characterized in that: Also includes: Comparator; The input end of the comparator is connected to the two ends of the overcurrent resistor Rs, and the output end of the comparator is connected to the input end of the controller; the comparator is used to obtain the voltage difference between the two ends of the overcurrent resistor Rs and send it to the controller, so that the controller can determine whether the current flowing through the overcurrent resistor Rs is too large.

3. The overcurrent protection device according to claim 1 or 2, characterized in that: A first switch U1 and a first inductor L1 connected in series are provided between a connection point between the second IGBT and the third IGBT among the four sequentially connected IGBTs of the NPCI type three-level circuit test circuit and a connection point between the first diode D1 and the second diode D2.

4. The overcurrent protection device according to claim 3, characterized in that: The controller is further configured to control the opening and closing of the first switch U1 through electrical connection.

5. The overcurrent protection device according to claim 1 or 2, characterized in that: A second switch U2 and a second inductor L2 connected in series are connected in parallel on both sides of the first IGBT and the second IGBT of the four sequentially connected IGBTs of the NPCI type three-level circuit test circuit.

6. The overcurrent protection device according to claim 5, characterized in that: The controller is further configured to control the opening and closing of the second switch U2 through electrical connection.

7. The overcurrent protection device according to claim 1 or 2, characterized in that: A third switch U3 and a third inductor L3 connected in series are connected in parallel on both sides of the third IGBT and the fourth IGBT below the four sequentially connected IGBTs of the NPCI type three-level circuit test circuit.

8. The overcurrent protection device according to claim 7, characterized in that: The controller is further configured to control the opening and closing of the third switch U3 through electrical connection.

9. The overcurrent protection device according to claim 1 or 2, characterized in that: The controller includes any one of a CPU, a single chip microcomputer, an FPGA or a CPLD.

10. A circuit board, characterized in that: An overcurrent protection device for an NPCI type three-level circuit test circuit comprising the device described in any one of claims 1 to 2.

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