A power element protection circuit

Abstract

This application provides a power element protection circuit, including: a current change rate detection module, a boost module, and a drive module. The drive module has a protection terminal and a drive terminal. The current change rate detection module is configured to send a first trigger signal to the boost module when it detects that the rate of change of current flowing through the power element is greater than or equal to a preset threshold for a continuous preset duration. The boost module is configured to increase the voltage at the protection terminal of the drive module to a preset voltage when it receives the first trigger signal. The drive module is configured to output a shutdown signal to the control terminal of the power element through the drive terminal to shut down the power element when the voltage at the protection terminal increases to the preset voltage. Applying the technical solution of this application can solve the problem in related technologies where detecting the voltage of the power element to determine whether a short circuit has occurred leads to the overcurrent protection function of the drive module being easily falsely triggered.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to a power element protection circuit. Background Technology

[0002] The motor controller plays a crucial role in the three-electric system of new energy vehicles, directly determining key performance parameters such as motor output power, torque, and speed. During motor operation, faults may cause short-circuit currents in the motor controller circuit. For example, faults could include foreign objects entering the motor or program errors within the controller causing simultaneous conduction of the upper and lower bridge switching units. In related technologies, if a fault current occurs in the motor controller circuit, the voltage detection unit of the drive module checks whether the voltage of the power components exceeds a threshold voltage to determine if a short-circuit current has occurred in the motor controller circuit. However, voltage fluctuations in the power components can easily lead to false triggering of the drive module's overcurrent protection function.

[0003] Application content

[0004] In view of the above problems, this application provides a power element protection circuit to solve the problem that the overcurrent protection is easily triggered falsely by detecting the voltage of the power element to determine whether a short circuit current has occurred.

[0005] According to one aspect of the embodiments of this application, a power element protection circuit is provided, including: a current change rate detection module, a boost module, and a drive module. The drive module has a protection terminal and a drive terminal. The current change rate detection module is configured to send a first trigger signal to the boost module when it detects that the rate of change of the current flowing through the power element is greater than or equal to a preset threshold for a continuous preset duration. The boost module is configured to increase the voltage of the protection terminal of the drive module to a preset voltage when it receives the first trigger signal. The drive module is configured to output a shutdown signal to the control terminal of the power element through the drive terminal to shut down the power element when the voltage of the protection terminal increases to the preset voltage.

[0006] In one alternative embodiment, the current change rate detection module includes a first capacitor and an inductor connected in parallel, the inductor being configured to be connected in series with the power element; a first terminal of the first capacitor is electrically connected to the control terminal of the boost module, and a second terminal of the first capacitor is grounded.

[0007] In one alternative, the inductor is connected in series with the output of the power element.

[0008] In one alternative embodiment, the current change rate detection module further includes: a first diode; the positive terminal of the first diode is connected to a first terminal of the inductor, and the negative terminal of the first diode is connected to a first terminal of the first capacitor.

[0009] In one alternative embodiment, the current change rate detection module further includes a fifth resistor; the first end of the fifth resistor is connected to the negative terminal of the first diode, and the second end of the fifth resistor is connected to the first end of the first capacitor.

[0010] In one alternative embodiment, the current change rate detection module further includes a second diode; the positive terminal of the second diode is grounded, and the negative terminal of the second diode is connected to the first terminal of the inductor.

[0011] In an alternative embodiment, the current change rate detection module further includes a sixth resistor; the sixth resistor is connected in parallel with the first capacitor.

[0012] In one optional embodiment, the boost module includes: a voltage source having a preset voltage, a first switching unit, and a second switching unit; the first switching unit is electrically connected to the current change rate detection module, and is used to generate a second trigger signal and send it to the second switching unit after receiving a first trigger signal from the boost module; the second switching unit is connected to the voltage source and the drive module respectively, and is used to turn on according to the second trigger signal to increase the voltage at the protection terminal of the drive module to the preset voltage of the voltage source.

[0013] In one optional embodiment, the first switching unit includes: a first resistor, a first switching transistor, a second resistor, and a third resistor; a first terminal of the first resistor is connected to the current change rate detection module, and a second terminal of the first resistor is connected to the control terminal of the first switching transistor; the input terminal of the first switching transistor is connected to the second terminal of the second resistor, and the output terminal of the first switching transistor is grounded; the second resistor and the third resistor are connected in series between the voltage source and the input terminal of the first switching transistor; the control terminal of the second switching unit is connected between the third resistor and the second resistor; and a first terminal of the third resistor is connected to the voltage source.

[0014] In one alternative embodiment, the second switching unit includes a second switching transistor and a fourth resistor; the control terminal of the second switching transistor is connected between the second resistor and the third resistor; the input terminal and the output terminal of the second switching transistor are respectively connected to the protection terminal of the drive module and the first terminal of the fourth resistor; the second terminal of the fourth resistor is grounded.

[0015] In this embodiment, a current change rate detection module detects the rate of change of current in the power element. If the current change rate detection module detects a current change rate on the power element that is greater than or equal to a preset threshold for a preset duration, it indicates that a short circuit has occurred and sends a first trigger signal to the boost module. When the boost module receives the first trigger signal, it raises the voltage at the protection terminal of the drive module to a preset voltage to trigger the protection of the drive module. When the voltage at the protection terminal of the drive module rises to the preset voltage, it outputs a shutdown signal to the power element through the control terminal, thereby cutting off the short circuit current and realizing overcurrent protection.

[0016] The method of determining whether a short circuit has occurred by detecting the voltage of the power component is flawed because the voltage of the power component may fluctuate, potentially triggering the overcurrent protection function of the drive module. This solution, however, uses a current change rate detection module to continuously monitor the rate of change of the power component's current to determine if a short circuit has occurred. When a short circuit current is generated, the rate of change of the current will continuously exceed a preset threshold. This solution eliminates the need to detect the voltage of the power component, thus preventing the overcurrent protection function of the drive module from being falsely triggered and offering higher reliability.

[0017] The above description is merely an overview of the technical solutions of the embodiments of this application. In order to better understand the technical means of the embodiments of this application and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of this application more obvious and understandable, specific implementation methods of this application are described below. Attached Figure Description

[0018] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0019] Figure 1 A circuit diagram of a motor controller loop provided in the related art is shown;

[0020] Figure 2 A structural diagram of a power element protection circuit provided by an exemplary embodiment of this application is shown;

[0021] Figure 3 A circuit diagram of a power element protection circuit provided by an exemplary embodiment of this application is shown. Detailed Implementation

[0022] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0023] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0024] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily need to be performed in the order described. "Multiple" as mentioned in this application refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship.

[0025] Figure 1 A circuit diagram of a motor controller loop provided in the related art is shown below. Please refer to [link / reference]. Figure 1 As shown in the related technology, when the motor controller circuit is working normally, the PWM (Pulse Width Modulation) signal is input through the IN pin of the drive module U, amplified by the drive module U, and then output. When the amplified PWM signal turns on the power module's switching transistor Q, the DS terminals of the switching transistor Q are turned on. The inductance Lm is relatively large, and the current in inductor Lm rises slowly. The inductance Lm is the winding inductance of the motor. The voltage across the DS terminals of the switching transistor Q is equal to the internal resistance of the switching transistor Q multiplied by the current, which is approximately 2V. The switching transistor Q can be the upper-bridge switching transistor or the lower-bridge switching transistor of the power module. The switching transistor Q can be a SiC (silicon carbide) module or an IGBT (Insulated Gate Bipolar Transistor) module.

[0026] When the PWM signal is turned on, the constant current source inside the driver module U charges the external circuit with a current of 5mA. This 5mA current flows out through the second resistor R2 and the first diode D1. Since the voltage across DS is approximately 2V at this time, the voltage across the third capacitor C3 is also 2V, which is less than the overcurrent protection trigger voltage of 9V for the driver module U. When the voltage across the third capacitor C3 is less than 9V, the desat terminal of the driver module U does not trigger the overcurrent protection.

[0027] When a short circuit occurs, the PWM signal is input through the IN pin of the driver module U, amplified by the driver module U, and output. When the amplified PWM signal turns on the power module's switching transistor Q, the DS terminals of the switching transistor Q are turned on. Since the inductance of Lm is very small after the short circuit, the current of Lm rises rapidly. The voltage across the DS terminals of the switching transistor Q is equal to the internal resistance of the switching transistor Q multiplied by the current, which is approximately tens to hundreds of volts. When the PWM signal turns on the switching transistor Q, the constant current source inside the driver module U charges the external circuit with a current of 5mA. Because the voltage across the DS terminals is greater than 9V at this time, the 5mA current will not flow out through the second resistor R2 and the first diode D1. The voltage across the third capacitor C3 will be greater than or equal to 9V as the constant current source charges. When the voltage across the third capacitor C3 is greater than or equal to 9V, the desat terminal of the driver module U triggers overcurrent protection, and the g terminal of the driver module U will send a control signal to control the switching transistor Q to perform soft turn-off.

[0028] However, under current technological conditions, SiC modules can only guarantee protection against short circuits for 2µs without damage, while IGBT modules can withstand short circuits for 10µs. Therefore, SiC modules require a shorter response time for short circuit protection. To ensure a 2µs protection duration, the value of the third capacitor C3 is usually reduced, but this reduces the probability of accidental activation due to interference.

[0029] Figure 2 A structural diagram of a power element protection circuit provided in an exemplary embodiment of this application is shown below. Please refer to [link / reference]. Figure 2 As shown, the power component protection circuit includes: a current change rate detection module 300, a boost module 400, and a drive module U, with the drive module U having a protection terminal and a drive terminal.

[0030] Specifically, the current change rate detection module 300 is configured to send a first trigger signal to the boost module 400 when the change rate of the current flowing through the power element Q3 is greater than or equal to a preset threshold after a preset duration of continuous detection.

[0031] The boost module 400 is configured to increase the voltage at the protection terminal of the drive module U to a preset voltage when a first trigger signal is received;

[0032] The drive module U is configured to output a shutdown signal to the control terminal of the power element Q3 through the drive terminal to turn off the power element Q3 when the voltage at the protection terminal rises to a preset voltage.

[0033] When no short circuit occurs, the drive module U can amplify the received first PWM signal to obtain the second PWM signal. The power element Q3 receives the second PWM signal and turns on. The power element Q3 is connected to the bus power supply terminal HV+ through the motor winding. The voltage of the bus power supply terminal HV+ can be between DC 400V and 800V. After the bus power supply terminal HV+ is turned on, the generated drive current will flow through the power element Q3. The power element Q3 can be the upper or lower bridge switch of the power module. The current change rate detection module 300 detects the rate of change of the current in the power element Q3. If the current change rate detection module 300 detects that the rate of change of the current in the power element Q3 is greater than or equal to a preset threshold for a preset duration, it indicates that a short circuit has occurred. A first trigger signal is sent to the boost module 400. When the boost module 400 receives the first trigger signal, it raises the voltage at the protection terminal of the drive module U to a preset voltage to trigger the protection function of the drive module U. When the voltage at the protection terminal of the drive module U rises to the preset voltage, it outputs a shutdown signal to the power element Q3 through the control terminal, thereby cutting off the short circuit current and realizing overcurrent protection.

[0034] The solution determines whether a short circuit has occurred in power component Q3 by detecting its voltage. However, the voltage of power component Q3 may fluctuate, which could trigger the overcurrent protection function of the drive module U. This solution uses a current change rate detection module 300 to continuously detect the rate of change of the current in power component Q3 to determine if a short circuit has occurred. When a short circuit current occurs, the rate of change of the current will continuously exceed a preset threshold. This solution does not require detecting the voltage of power component Q3 and will not trigger the overcurrent protection function of the drive module, thus providing higher reliability.

[0035] Figure 3 A circuit diagram of a power element Q3 protection circuit provided in an exemplary embodiment of this application is shown. Please refer to [link / reference]. Figure 3 As shown, the current change rate detection module 300 includes a first capacitor C1 and an inductor L1 connected in parallel. The inductor L1 is configured to be connected in series with the power element Q3. The first terminal of the first capacitor C1 is electrically connected to the control terminal of the boost module 400, and the second terminal of the first capacitor C1 is grounded. The inductor L1 is connected in series with the output terminal of the power element Q3.

[0036] In this circuit, inductor L1 can be considered as the stray inductance equivalent to the copper busbar of drive module U. The current of power element Q3 will flow through inductor L1. When a short-circuit current occurs, the rate of change of current will increase, and the voltage of inductor L1 will rise. When the rate of change of current is greater than or equal to a preset threshold, that is, when the voltage of inductor L1 exceeds the preset voltage threshold, a first trigger signal is sent to boost module 400. When a short-term interference occurs, for example, less than 10 ns, due to the presence of the first capacitor C1, the small voltage generated on inductor L1 will be absorbed by the first capacitor C1, which can filter out the short-term interference. When the voltage of inductor L1 exceeds the preset voltage threshold and is maintained for a preset duration, which can be 500 ns, the first trigger signal will be sent.

[0037] The current change rate detection module 300 also includes: a first diode D1; the positive terminal of the first diode D1 is connected to the first terminal of the inductor L1, and the negative terminal of the first diode D1 is connected to the first terminal of the first capacitor C1.

[0038] The first diode D1 is used to prevent the current generated by the discharge of the first capacitor C1 from flowing through the inductor L1, so as to avoid forming a closed circuit and causing resonance between the first capacitor C1 and the inductor L1.

[0039] The current change rate detection module 300 also includes: a fifth resistor R5; the first end of the fifth resistor R5 is connected to the negative terminal of the first diode D1, and the second end of the fifth resistor R5 is connected to the first end of the first capacitor C1.

[0040] The fifth resistor R5 is used to limit the current, restricting the charging speed to the first capacitor C1 and preventing damping of circuit oscillations.

[0041] The current change rate detection module 300 also includes: a sixth resistor R6; the sixth resistor R6 is connected in parallel with the first capacitor C1.

[0042] Among them, the sixth resistor R6 and the first capacitor C1 form a discharge circuit to release the charge on the first capacitor C1.

[0043] The current change rate detection module 300 also includes: a second diode D2; the positive terminal of the second diode D2 is grounded, and the negative terminal of the second diode D2 is connected to the first terminal of the inductor L1.

[0044] When power component Q3 is disconnected, due to the characteristic of inductor L1 to impede current change, an induced electromotive force will exist on inductor L1 in the same direction as the motor drive current in order to maintain the current constant. This induced electromotive force may generate a very high voltage, thereby damaging other components in the circuit. By setting a second diode D2, after the drive module U is disconnected, the remaining current in inductor L1 can flow through the second diode D2 for freewheeling, so that the electrical energy in inductor L1 can be discharged and high voltage is avoided from being generated across inductor L1.

[0045] The boost module 400 includes: a voltage source VCC+ with a preset voltage, a first switching unit 410, and a second switching unit 420; the first switching unit 410 is electrically connected to the current change rate detection module 300, and is used to generate a second trigger signal and send it to the second switching unit 420 after receiving the first trigger signal of the boost module 400 to turn on.

[0046] The second switching unit 420 is connected to the voltage source VCC+ and the drive module U respectively, and is used to turn on according to the second trigger signal to raise the voltage of the protection terminal desat of the drive module U to the preset voltage of the voltage source VCC+.

[0047] In this circuit, after the first switching unit 410 receives and turns on the first trigger signal, it generates a second trigger signal and sends it to the second switching unit 420. Upon turning on the second trigger signal, the second switching unit 420 connects the protection terminal desat of the drive module U to the voltage source VCC+, thereby raising the voltage at the protection terminal desat of the drive module U to a preset voltage of the voltage source VCC+. It is understood that in order to trigger the overcurrent protection function of the drive module U, the voltage of the voltage source VCC+ should be greater than or equal to the trigger voltage of the protection terminal desat of the drive module U. For example, the voltage of the voltage source VCC+ can be set to 12V.

[0048] The first switching unit 410 includes: a first resistor R1, a first switching transistor Q1, a second resistor R2, and a third resistor R3; the first end of the first resistor R1 is connected to the current change rate detection module 300, and the second end of the first resistor R1 is connected to the control terminal of the first switching transistor Q1; the input terminal of the first switching transistor Q1 is connected to the second end of the second resistor R2, and the output terminal of the first switching transistor Q1 is grounded; the second resistor R2 and the third resistor R3 are connected in series between the voltage source VCC+ and the input terminal of the first switching transistor Q1; the control terminal of the second switching unit 420 is connected between the third resistor R3 and the second resistor R2; the first end of the third resistor R3 is connected to the voltage source VCC+. The first switching transistor Q1 can be an NPN transistor or a MOSFET.

[0049] The first resistor R1 is used to limit the current flowing into the first switch Q1. When the rate of change of the current of the inductor L1 is greater than or equal to a preset threshold for a preset duration, the voltage across the first capacitor C1 will exceed the turn-on voltage of the first switch Q1, thereby triggering the first switch Q1 to turn on, connecting the first switch Q1 to the voltage source VCC+, and outputting a second trigger signal through the voltage divider between the third resistor R3 and the second resistor R2.

[0050] The second switching unit 420 includes: a second switching transistor Q2 and a fourth resistor R4; the control terminal of the second switching transistor Q2 is connected between the second resistor R2 and the third resistor R3, the input terminal and the output terminal of the second switching transistor Q2 are respectively connected to the protection terminal desat of the drive module U and the first terminal of the fourth resistor R4; the second terminal of the fourth resistor R4 is grounded.

[0051] In this circuit, the control terminal of the second switch Q2 will conduct upon receiving the second trigger signal, connecting the protection terminal desat of the drive module U to the voltage source VCC+. This raises the voltage at the protection terminal desat of the drive module U to a preset voltage of the voltage source VCC+. Once the voltage at the protection terminal desat of the drive module U reaches the preset voltage, the drive terminal g of the drive module U sends a turn-off signal to turn off the power element Q3, thereby cutting off the short-circuit current and achieving overcurrent protection. The drive module U can be a gate driver chip, specifically the NCD57100. It is understood that different gate driver chips will have different overcurrent protection trigger voltages at their corresponding protection terminal desat. The second switch Q2 can be a PNP transistor or a MOSFET.

[0052] The power element protection circuit also includes: a seventh resistor R7, a third diode D3, and an eighth resistor R8; the protection terminal desat of the drive module U is also connected to the first terminal of the seventh resistor R7, and the drive terminal g of the drive module U is connected to the first terminal of the eighth resistor R8; the second terminal of the seventh resistor R7 is connected to the positive terminal of the third diode D3; the negative terminal of the third diode D3 is connected to the second terminal of the motor winding and the drain D of the power element Q3 respectively; the second terminal of the eighth resistor R8 is connected to the gate of the power element Q3.

[0053] The above description is merely a preferred exemplary embodiment of this application and is not intended to limit the implementation of this application. Those skilled in the art can easily make corresponding modifications or alterations based on the main concept and spirit of this application. Therefore, the scope of protection of this application should be determined by the scope of protection claimed in the claims.

Claims

1. A power element protection circuit, characterized in that, include: The system includes a current change rate detection module, a boost module, and a drive module, wherein the drive module has a protection terminal and a drive terminal. The current change rate detection module is configured to send a first trigger signal to the boost module when it detects that the rate of change of the current flowing through the power element is greater than or equal to a preset threshold for a continuous preset duration. The boost module is configured to increase the voltage at the protection terminal of the drive module to a preset voltage when the first trigger signal is received; The drive module is configured to output a shutdown signal to the control terminal of the power element to shut down the power element when the voltage at the protection terminal rises to the preset voltage.

2. The power element protection circuit as described in claim 1, characterized in that, The current change rate detection module includes a first capacitor and an inductor connected in parallel, wherein the inductor is configured to be connected in series with the power element. The first terminal of the first capacitor is electrically connected to the control terminal of the boost module, and the second terminal of the first capacitor is grounded.

3. A power element protection circuit as described in claim 2, characterized in that, The inductor is connected in series at the output terminal of the power element.

4. A power element protection circuit as described in claim 2, characterized in that, The current change rate detection module further includes: a first diode; The positive terminal of the first diode is connected to the first terminal of the inductor, and the negative terminal of the first diode is connected to the first terminal of the first capacitor.

5. A power element protection circuit as described in claim 4, characterized in that, The current change rate detection module further includes: a fifth resistor; The first end of the fifth resistor is connected to the negative terminal of the first diode, and the second end of the fifth resistor is connected to the first end of the first capacitor.

6. A power element protection circuit as described in claim 5, characterized in that, The current change rate detection module further includes: a second diode; The positive terminal of the second diode is grounded, and the negative terminal of the second diode is connected to the first terminal of the inductor.

7. A power element protection circuit as described in claim 6, characterized in that, The current change rate detection module further includes: a sixth resistor; The sixth resistor is connected in parallel with the first capacitor.

8. A power element protection circuit as described in claim 2, characterized in that, The boost module includes: a voltage source with a preset voltage, a first switching unit, and a second switching unit; The first switching unit is electrically connected to the current change rate detection module, and is used to generate a second trigger signal and send it to the second switching unit after receiving the first trigger signal of the boost module and turning it on. The second switching unit is connected to the voltage source and the drive module respectively, and is used to turn on according to the second trigger signal to increase the voltage at the protection terminal of the drive module to the preset voltage of the voltage source.

9. A power element protection circuit as described in claim 8, characterized in that, The first switching unit includes: a first resistor, a first switching transistor, a second resistor, and a third resistor; The first end of the first resistor is connected to the current change rate detection module, and the second end of the first resistor is connected to the control terminal of the first switching transistor. The input terminal of the first switching transistor is connected to the second terminal of the second resistor, and the output terminal of the first switching transistor is grounded. The second resistor and the third resistor are connected in series between the voltage source and the input terminal of the first switching transistor; The control terminal of the second switching unit is connected between the third resistor and the second resistor; The first terminal of the third resistor is connected to the voltage source.

10. A power element protection circuit as described in claim 9, characterized in that, The second switching unit includes: a second switching transistor and a fourth resistor; The control terminal of the second switch is connected between the second resistor and the third resistor, and the input terminal and the output terminal of the second switch are respectively connected to the protection terminal of the drive module and the first terminal of the fourth resistor. The second terminal of the fourth resistor is grounded.

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