An overcurrent protection circuit

Abstract

The embodiment of the present invention discloses an overcurrent protection circuit. The overcurrent protection circuit is configured by arranging a switch module and a sampling control module between a driving module and a first transistor. When the sampling control module samples that the voltage at the third end of the first transistor reaches a first preset voltage, the switch module is controlled to disconnect the discharge path of the charging and discharging module, so that the current output by the driving module cannot pass through the switch module, but is output to the charging and discharging module, so that the charging and discharging module is charged; and when the voltage of the charging and discharging module reaches a second preset voltage, the driving module outputs a shutdown control signal to the first end of the first transistor to shut down the first transistor. By reasonably setting the first preset voltage and the second preset voltage, when there is a certain gap between the current flowing through the first transistor and the overcurrent protection point of the first transistor, the first transistor is shut down, thereby protecting the first transistor and preventing the current flowing through the first transistor from being too large and being damaged.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of power device protection, and in particular to an overcurrent protection circuit. Background Art

[0002] When driving IGBT / MOS tubes, the drive requires isolation, and usually uses a driver chip to drive, such as 1ED020I12FA2 driver chip to drive IGBT / MOS tubes. However, when driving IGBT / MOS tubes, the device is usually damaged due to overcurrent, so overcurrent protection of the drive circuit is particularly important.

[0003] In the prior art, the desaturation detection method is usually used to implement overcurrent protection of the driving circuit. The main principle is: taking the 1ED020I12FA2 driver chip as an example, the Desat pin of the driver chip is used to detect the voltage drop between the collector and the emitter of the IGBT / MOS tube to protect the IGBT / MOS tube and prevent the IGBT / MOS tube from being damaged due to excessive current. However, this method has some disadvantages: when the Desat pin of the driver chip detects a rapid rise in the voltage between the collector and the emitter, the current of the driver tube will generally reach about 4 times the nominal current. At this time, turning off the driver tube will cause a large turn-off spike at both ends of the collector and the emitter, thereby requiring additional circuits to suppress the voltage spikes. At the same time, the loss of the driver tube is also large, which will affect the service life of the driver tube and may even directly cause damage to the driver tube. Summary of the invention

[0004] The present invention provides an overcurrent protection circuit to realize shutting off a driving tube before the driving tube reaches a relatively large current, thereby preventing the driving tube from being damaged due to the excessive current.

[0005] An embodiment of the present invention provides an overcurrent protection circuit, which includes: a driving module, a first transistor, a charging and discharging module, a switch module and a sampling control module; wherein the first output end of the driving module is electrically connected to the first end of the first transistor, the second end of the first transistor is connected to the power supply end, and the third end of the first transistor is grounded through the sampling control module; the second output end of the driving module is electrically connected to the charging and discharging module and the switch module respectively, and the switch module is also electrically connected to the sampling control module;

[0006] The sampling control module is used to sample the voltage of the third terminal of the first transistor, and when the voltage of the third terminal of the first transistor reaches a first preset voltage, control the switch module to disconnect the discharge path of the charge and discharge module, so that the driving module charges the charge and discharge module;

[0007] The driving module is used for outputting a shut-off control signal to the first end of the first transistor through the first output end when the voltage of the charging and discharging module reaches a second preset voltage, so as to shut down the first transistor.

[0008] The present invention provides an overcurrent protection circuit. The overcurrent protection circuit is provided by arranging a switch module and a sampling control module between a driving module and a first transistor. When the sampling control module samples that the voltage at the third end of the first transistor reaches a first preset voltage, the switch module is controlled to disconnect the discharge path of the charging and discharging module so that the driving module charges the charging and discharging module. When the voltage of the charging and discharging module reaches a second preset voltage, the driving module outputs a shutdown control signal to the first end of the first transistor through its first output end so that the first transistor is turned off. Among them, the first preset voltage is a voltage that is lower than the overcurrent protection voltage by a preset threshold, wherein the overcurrent protection voltage is the voltage of the third terminal of the first transistor when the current flowing through the first transistor is equal to the overcurrent protection point, and the preset threshold is a range value. When the sampling control module samples that the voltage of the third terminal of the first transistor reaches the first preset voltage, the switch module is controlled to disconnect the discharge path of the charge and discharge module, so that the current output by the drive module cannot pass through the switch module, but is output to the charge and discharge module, so that the charge and discharge module is charged; and when the voltage of the charge and discharge module reaches the second preset voltage, the drive module outputs a shutdown control signal to the first terminal of the first transistor to turn off the first transistor. By reasonably setting the size of the first preset voltage and the second preset voltage, when there is a certain gap between the current flowing through the first transistor and the overcurrent protection point of the first transistor, the first transistor is turned off, thereby protecting the first transistor and avoiding damage due to excessive current flowing through the first transistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a schematic diagram of the structure of an overcurrent protection circuit in Embodiment 1 of the present invention;

[0010] Figure 2 It is a circuit schematic diagram of an overcurrent protection circuit in Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0011] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0012] Embodiment 1

[0013] Figure 1 FIG. 1 is a schematic diagram of an overcurrent protection circuit structure provided in Embodiment 1 of the present invention, referring to FIG. Figure 1, the overcurrent protection circuit includes a driving module 100, a first transistor M1, a charging and discharging module 200, a switch module 300 and a sampling control module 400; wherein the first output terminal A1 of the driving module 100 is electrically connected to the first terminal B1 of the first transistor M1, the second terminal B2 of the first transistor M1 is connected to the power supply terminal V0, and the third terminal B3 of the first transistor M1 is grounded through the sampling control module 400; the second output terminal A2 of the driving module 100 is electrically connected to the charging and discharging module 200 and the switch module 300 respectively, and the switch module 300 is also electrically connected to the sampling control module 400;

[0014] The sampling control module 400 is used to sample the voltage of the third terminal B3 of the first transistor M1, and when the voltage of the third terminal B3 of the first transistor M1 reaches a first preset voltage, the switch module 400 is controlled to disconnect the discharge path of the charge and discharge module 200, so that the driving module 100 charges the charge and discharge module 200;

[0015] The driving module 100 is used for outputting a shut-off control signal to the first terminal B1 of the first transistor M1 through the first output terminal A1 when the voltage of the charging and discharging module 200 reaches a second preset voltage, so as to shut down the first transistor M1.

[0016] The driving module 100 is a driving chip, such as a 1ED020I12FA2 driving chip, and the second output terminal A2 of the driving module 100 may correspond to the Desat pin of the 1ED020I12FA2 driving chip. The first transistor M1 is a driving transistor, driven by the driving module.

[0017] The current of the first transistor can be detected by sampling the voltage at the third terminal of the first transistor M1 through the sampling control module. The first preset voltage is a voltage lower than the overcurrent protection voltage by a preset threshold, wherein the overcurrent protection voltage is the voltage at the third terminal of the first transistor when the current flowing through the first transistor M1 is equal to the overcurrent protection point, the preset threshold is a range value, and the first preset voltage is also a range value, which can be set according to actual needs. The second preset voltage is the charging threshold voltage set by the driving module 100. When the charging voltage of the charging and discharging module 200 reaches the second preset voltage, the driving module 100 will control the first transistor M1 to be turned off to protect the first transistor M1. Optionally, according to the requirements of the overcurrent protection point of the first transistor or the driving tube, the first preset voltage and the second preset voltage parameters are reasonably set to protect the first transistor at a current far less than the overcurrent protection point.

[0018] In the technical solution of this embodiment, the implementation process of the overcurrent protection circuit is: Figure 1The driving module 100 inputs a driving voltage to the first terminal B1 of the first transistor M1 through the first output terminal A1 to drive the first transistor M1. The switch module 300 is in an on state by default. The current output by the internal current source of the driving module 100 is output to the switch module 300 through the second output terminal A2. The discharge current of the charge and discharge module 200 is also output to the switch module 300. The sampling control module 400 samples the voltage of the third terminal B3 of the first transistor M1 in real time. When the voltage of the third terminal B3 of the first transistor M1 reaches the first preset voltage, the sampling control module 400 controls the switch module 300 to disconnect, thereby disconnecting the charge and discharge. The discharge path of the module 200 makes it impossible for the current output by the internal current source of the driving module 100 to be input into the switch module but into the charging and discharging module 200, and the charging and discharging module 200 is charged, and when the voltage of the charging and discharging module reaches the second preset voltage, the driving module outputs a shutdown control signal to the first end of the first transistor to turn off the first transistor, and by reasonably setting the magnitude of the first preset voltage and the second preset voltage, when there is a certain gap between the current flowing through the first transistor and the overcurrent protection point of the first transistor, the first transistor is turned off, thereby protecting the first transistor and avoiding the overcurrent problem of the first transistor M1. When the voltage of the charging and discharging module 200 reaches the second preset voltage, the driving module 100 outputs a shutdown control signal to the first end B1 of the first transistor M1 through the first output terminal A1 to turn off the first transistor M1, thereby protecting the first transistor and avoiding it from being damaged by excessive voltage or current. In addition, according to the actual requirements of the overcurrent protection point of the first transistor, the first preset voltage and the second preset voltage parameters can be reasonably set to protect the first transistor at a current far less than the overcurrent protection point.

[0019] The technical solution of this embodiment provides an overcurrent protection circuit. The overcurrent protection circuit sets a switch module and a sampling control module between the driving module and the first transistor. When the sampling control module samples that the voltage at the third end of the first transistor reaches a first preset voltage, the switch module is controlled to disconnect the discharge path of the charging and discharging module so that the driving module charges the charging and discharging module. When the voltage of the charging and discharging module reaches a second preset voltage, the driving module outputs a shutdown control signal to the first end of the first transistor through its first output end to shut down the first transistor. Among them, the first preset voltage is a voltage that is lower than the overcurrent protection voltage by a preset threshold, wherein the overcurrent protection voltage is the voltage of the third terminal of the first transistor when the current flowing through the first transistor is equal to the overcurrent protection point, and the preset threshold is a range value. When the sampling control module samples that the voltage of the third terminal of the first transistor reaches the first preset voltage, the switch module is controlled to disconnect the discharge path of the charging and discharging module, so that the current output by the driving module cannot pass through the switch module, but is output to the charging and discharging module, so that the charging and discharging module is charged; and when the voltage of the charging and discharging module reaches the second preset voltage, the driving module outputs a shutdown control signal to the first terminal of the first transistor to turn off the first transistor, thereby protecting the first transistor. By reasonably setting the first preset voltage and the second preset voltage, when there is a certain gap between the current flowing through the first transistor and the overcurrent protection point of the first transistor, the first transistor is turned off to avoid damage caused by excessive current flowing through the first transistor.

[0020] Embodiment 2

[0021] Figure 2 is a circuit schematic diagram of an overcurrent protection circuit provided in the second embodiment of the present invention. This embodiment is based on the above-mentioned first embodiment. Figure 2 The switch module 300 includes a first resistor R1, a first diode D1, a second transistor M2 and a third transistor M3. The first resistor R1 is electrically connected to the second output terminal A2 of the driving module 100 and the anode of the first diode D1 respectively, the cathode of the first diode D1 is electrically connected to the second end of the second transistor M2, the first end of the second transistor M2 is electrically connected to the second end of the third transistor M3, the third end of the second transistor M2 is grounded, the first end of the third transistor M3 is electrically connected to the sampling control module 400, and the third end of the third transistor M3 is grounded.

[0022] The second transistor M2 and the third transistor M3 can be NPN transistors. The working principle of the switch module 300 is as follows: the driving module 100 inputs a driving voltage to the first end B1 of the first transistor M1 through the first output end A1 to drive the first transistor M1, and the first transistor M1 works normally. When the sampling voltage of the sampling control module is low, the second transistor M2 is in the on state by default, and the third transistor M3 is in the off state by default. The current output by the internal current source of the driving module 100 is output through the second output end A2 and output to the second end of the second transistor M2 through the first resistor R1 and the first diode D1. The discharge current of the charge and discharge module 200 is also output to the second end of the second transistor M2 through the first resistor R1 and the first diode D1, and finally output to the ground GND through the third end of the second transistor M2. The sampling control module 400 samples the voltage of the third terminal B3 of the first transistor M1 in real time. When the voltage of the third terminal B3 of the first transistor M1 reaches the first preset voltage, the sampling control module 400 inputs a high-level signal to the first terminal of the third transistor M3, so that the third transistor M3 is turned on. After the third transistor M3 is turned on, the voltage of the first terminal of the second transistor M2 is pulled down, so that the second transistor M2 is turned off, so that the current output by the internal current source of the driving module 100 cannot pass through the second transistor M2, but is input to the charging and discharging module 200, so that the charging and discharging module 200 is charged.

[0023] Optionally, the switch module 300 further includes a second resistor R2, a first end of the second resistor R2 is connected to the power supply end V0, and a second end of the second resistor R2 is electrically connected to the first end of the second transistor M2.

[0024] Since the second transistor M2 is in the on state by default, the power supply voltage is connected through the power supply terminal V0 and output to the first end of the second transistor M2 through the second resistor R2 to turn on the second transistor M2. In addition, the second resistor R2 is also used to prevent the base voltage of the second transistor M2 from being too large.

[0025] Optionally, the switch module 300 also includes a third resistor R3, a fourth resistor R4 and a fifth resistor R5, the third resistor R3 is connected between the first end and the third end of the second transistor M2, the fourth resistor R4 is connected between the first end and the third end of the third transistor M3, the first end of the fifth resistor R5 is electrically connected to the first end of the third transistor M3, and the second end of the fifth resistor R5 is electrically connected to the sampling control module 400.

[0026] Among them, the third resistor R3 is used to share the voltage of the first end (base) of the second transistor M2, and provide a static operating point of the base for the second transistor M2, so that the base energy is consumed on the resistor when the power is off, so as to ensure that the second transistor M2 is reliably turned off. Similarly, the fourth resistor R4 is used to share the voltage of the first end (base) of the third transistor M3, and provide a static operating point of the base for the third transistor M3, so that the base energy is consumed on the resistor when the power is off, so as to ensure that the third transistor M3 is reliably turned off. The fifth resistor R5 is used for voltage division and current limiting.

[0027] Optionally, the first transistor M1 , the second transistor M2 and the third transistor M3 are MOS transistors or IGBT transistors.

[0028] The first transistor M1, the second transistor M2 and the third transistor M3 can all be NPN MOS transistors or NPN IGBT transistors. The first transistor M1 can be used as a driving transistor to drive a load. The second transistor M2 and the third transistor M3 can be used as switch transistors.

[0029] Optionally, the sampling control module 400 includes a sixth resistor R6, a seventh resistor R7 and a second diode D2, the first end of the sixth resistor R6 is electrically connected to the third end of the first transistor M1, the second end of the sixth resistor R6 is grounded, the cathode of the second diode D2 is electrically connected to the first end of the sixth resistor R6, the anode of the second diode D2 is electrically connected to the second end of the sixth resistor R6 through the seventh resistor R7, and the anode of the second diode D2 is also electrically connected to the switch module 300.

[0030] Among them, the second diode D2 is a voltage stabilizing diode, and the sixth resistor R6 is a sampling resistor, which is used to collect the voltage of the third end of the first transistor M1. Under the drive of the driving module 100, the current of the first transistor M1 gradually increases, and the voltage of the sampling resistor R6 gradually increases. When the voltage of the third end of the first transistor M1 is greater than the first preset voltage, the overcurrent point required by the first transistor M1 is reached, and the voltage of the sampling resistor R6 increases, causing the second diode D2 to enter a breakdown state. In the breakdown state, the voltage of the third end of the first transistor M1 will flow into the first end of the third transistor M3, turning on the third transistor M3. After the third transistor M3 is turned on, it pulls down the voltage of the first end of the second transistor M2, turning off the second transistor M2, so that the discharge current output by the charge and discharge module 200 and the current output by the internal current source of the driving module 100 can no longer be input to the second transistor M2 through the first resistor R1 and the first diode D1, and input to the charge and discharge module 200, so that the charge and discharge module 200 is charged.

[0031] Optionally, the sampling control module 300 further includes a first capacitor C1 , a first end of the first capacitor C1 is electrically connected to the anode of the second diode D2 , and a second end of the first capacitor C1 is grounded.

[0032] The first capacitor C1 is used for filtering.

[0033] Optionally, the second diode D2 is a voltage regulator diode.

[0034] The first preset voltage can be adjusted by selecting a Zener diode with different parameters. Specifically, the Zener diode is selected according to the reverse breakdown voltage of the Zener diode to adjust the first preset voltage, thereby protecting the first transistor M1 at a current far less than the desaturation point, avoiding overcurrent in the first transistor M1, and thus protecting the first transistor M1.

[0035] Optionally, the charge and discharge module includes a second capacitor C2, a first end of the second capacitor C2 is electrically connected to the second output end A2 of the driving module 100 and the switch module 300, and a second end of the second capacitor C2 is grounded.

[0036] Among them, when the voltage at the third terminal of the first transistor M1 is less than the first preset voltage, the second capacitor C2 is in a discharging state, and the discharge current of the second capacitor C2 is input to the second transistor M2 through the first resistor R1 and the first diode D1, and output to the ground terminal GND through the second transistor M2. When the voltage at the third terminal of the first transistor M1 is greater than the first preset voltage, since the third transistor M3 is turned on and the second transistor M2 is turned off, the current output by the internal current source of the driving module 100 is input to the second capacitor C2, so that the second capacitor C2 is charged. When the voltage of the second capacitor C2 reaches the second preset voltage, the driving module 100 outputs a shutdown control signal to the first terminal B1 of the first transistor M1 through the first output terminal A1 to turn off the first transistor M1, thereby protecting the first transistor from being damaged due to excessive voltage or current. In addition, according to the actual requirements of the overcurrent protection point of the first transistor, the first preset voltage and the second preset voltage parameters can be reasonably set to protect the first transistor at a current far less than the overcurrent protection point.

[0037] Optionally, an eighth resistor R8 and a ninth resistor R9 are also included, the first end of the eighth resistor R8 is electrically connected to the first output end A1 of the driving module 100, the second end of the eighth resistor R8 is electrically connected to the first end of the first transistor M1, and the ninth resistor R9 is connected between the first end and the third end of the first transistor M1.

[0038] The eighth resistor R8 and the ninth resistor R9 are used for voltage division and current limiting.

[0039] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. An overcurrent protection circuit, characterized in that: include: A driving module, a first transistor, a charging and discharging module, a switch module and a sampling control module; wherein the first output terminal of the driving module is electrically connected to the first terminal of the first transistor, the second terminal of the first transistor is connected to the power supply terminal, and the third terminal of the first transistor is grounded through the sampling control module; the second output terminal of the driving module is electrically connected to the charging and discharging module and the switch module respectively, and the switch module is also electrically connected to the sampling control module; The sampling control module is used to sample the voltage of the third terminal of the first transistor, and when the voltage of the third terminal of the first transistor reaches a first preset voltage, control the switch module to disconnect the discharge path of the charge and discharge module, so that the driving module charges the charge and discharge module; The driving module is used for outputting a shutdown control signal to the first end of the first transistor through the first output end when the voltage of the charging and discharging module reaches a second preset voltage, so as to shut down the first transistor; The switch module includes a first resistor, a first diode, a second transistor and a third transistor, the first resistor is electrically connected to the second output terminal of the driving module and the anode of the first diode respectively, the cathode of the first diode is electrically connected to the second terminal of the second transistor, the first terminal of the second transistor is electrically connected to the second terminal of the third transistor, the third terminal of the second transistor is grounded, the first terminal of the third transistor is electrically connected to the sampling control module, and the third terminal of the third transistor is grounded; The switch module further includes a second resistor, a first end of the second resistor is connected to the power supply end, and a second end of the second resistor is electrically connected to the first end of the second transistor; The switch module further includes a third resistor, a fourth resistor and a fifth resistor, the third resistor is connected between the first end and the third end of the second transistor, the fourth resistor is connected between the first end and the third end of the third transistor, the first end of the fifth resistor is electrically connected to the first end of the third transistor, and the second end of the fifth resistor is electrically connected to the sampling control module; The charging and discharging module comprises a second capacitor, a first end of the second capacitor is electrically connected to the second output end of the driving module and the switch module respectively, and a second end of the second capacitor is grounded.

2. The overcurrent protection circuit according to claim 1, characterized in that: The first transistor, the second transistor and the third transistor are MOS transistors or IGBT transistors.

3. The overcurrent protection circuit according to claim 1, characterized in that: The sampling control module includes a sixth resistor, a seventh resistor and a second diode, the first end of the sixth resistor is electrically connected to the third end of the first transistor, the second end of the sixth resistor is grounded, the cathode of the second diode is electrically connected to the first end of the sixth resistor, the anode of the second diode is electrically connected to the second end of the sixth resistor through the seventh resistor, and the anode of the second diode is also electrically connected to the switch module.

4. The overcurrent protection circuit according to claim 3, characterized in that: The sampling control module further includes a first capacitor, a first end of the first capacitor is electrically connected to the anode of the second diode, and a second end of the first capacitor is grounded.

5. The overcurrent protection circuit according to claim 3, characterized in that: The second diode is a voltage regulator diode.

6. The overcurrent protection circuit according to claim 1, characterized in that: It also includes an eighth resistor and a ninth resistor, wherein the first end of the eighth resistor is electrically connected to the first output end of the driving module, the second end of the eighth resistor is electrically connected to the first end of the first transistor, and the ninth resistor is connected between the first end and the third end of the first transistor.

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