Low voltage power supply power-off protection circuit and low voltage power supply power-off protection device

Abstract

The present invention provides a low-voltage power supply power-off protection circuit and a low-voltage power supply power-off protection device. The low-voltage power supply power-off protection circuit includes a first power supply input terminal connected to a first low-voltage power supply, a second power supply input terminal connected to a second low-voltage power supply, a comparison switch circuit, and an execution circuit. The first comparison terminal of the comparison switch circuit is connected to the first power supply input terminal, the second comparison terminal of the comparison switch circuit is connected to the second power supply input terminal, the power input terminal of the comparison switch circuit is connected to the first low-voltage power supply, and the power output terminal of the comparison switch circuit is connected to the power terminal of the execution circuit. The technical solution of the present invention can solve the technical problem of damage to insulated gate bipolar transistors caused by active short-circuiting operations performed by the electric drive system when the low-voltage power supply is lost.

Description

Technical Field

[0001] The present invention relates to the technical field of electric vehicles, and in particular to a low-voltage power supply power-off protection circuit and a low-voltage power supply power-off protection device. Background Art

[0002] With the popularity of electric vehicles, the safety of electric vehicles has received increasing attention. Specifically, when a safety fault occurs in the electric drive system, such as a fault that violates torque safety, the electric drive system should enter a safe state, namely ASC (active short circuit) or Freewheeling. Among them, the path for the electric drive system to enter a safe state is usually divided into three levels: torque control level (software category), torque monitoring level (software category), and MCU (Micro Control Unit) monitoring level (hardware category). The MCU monitoring level is completely triggered by hardware and is not controlled by software to ensure that ASC operations can still be performed in the event of MCU failure.

[0003] When the electric drive system is in operation and the low-voltage power supply fails, the MCU monitoring layer triggers the execution of ASC. However, due to the loss of low-voltage power, the output voltage of the driver power supply drops, resulting in insufficient driver voltage. Performing ASC with insufficient driver voltage can damage the IGBT (Insulated Gate Bipolar Transistor). To prevent damage to the IGBT during ASC in this situation, a backup driver power supply is often used, drawing power from the high-voltage power battery. However, adding a backup power supply increases the cost of the electric drive system and the PCB area. Summary of the Invention

[0004] The present invention provides a low-voltage power supply power-off protection circuit and a low-voltage power supply power-off protection device, aiming to solve the technical problem that when the low-voltage power supply is powered off, an electric drive system performs an active short-circuit operation, which causes damage to an insulated gate bipolar transistor.

[0005] To achieve the above object, the present invention provides a low-voltage power supply power-off protection circuit, the low-voltage power supply power-off protection circuit comprising a first power supply input terminal connected to a first low-voltage power supply, a second power supply input terminal connected to a second low-voltage power supply, a comparison switch circuit, and an execution circuit;

[0006] The first comparison terminal of the comparison switch circuit is connected to the first power input terminal, the second comparison terminal of the comparison switch circuit is connected to the second power input terminal, the power input terminal of the comparison switch circuit is connected to the first low-voltage power supply, and the power output terminal of the comparison switch circuit is connected to the power terminal of the execution circuit;

[0007] The comparison switch circuit is used to disconnect the input power of the execution circuit according to a predetermined method when the second low-voltage power supply is powered off, so that the execution circuit stops performing the active short-circuit operation.

[0008] Optionally, the power input terminal of the comparison switch circuit is connected to the first power input terminal.

[0009] Optionally, the comparison switch circuit includes a comparison circuit and a switch circuit;

[0010] The positive input terminal of the comparison circuit is the first comparison terminal of the comparison switch circuit, the negative input terminal of the comparison circuit is the second comparison terminal of the comparison switch circuit, and the output terminal of the comparison circuit is connected to the controlled terminal of the switch circuit;

[0011] The power input end of the switch circuit is the power input end of the comparison switch circuit, and the power output end of the switch circuit is the power output end of the comparison switch circuit.

[0012] Optionally, the switch circuit includes a first resistor, a second resistor and a first transistor;

[0013] The first end of the first resistor is connected to the first power input terminal, the second end of the first resistor is connected to the first end of the second resistor, the first end of the second resistor is the controlled end of the switch circuit, and the second end of the second resistor is connected to the controlled end of the first transistor;

[0014] The input end of the first transistor is the power input end of the switch circuit, and the output end of the first transistor is the power output end of the switch circuit.

[0015] Optionally, the low-voltage power supply power-off protection circuit further includes a signal detection circuit and an execution signal input terminal;

[0016] The input end of the signal detection circuit is connected to the execution signal input end, and the output end of the signal detection circuit is connected to the signal input end of the execution circuit.

[0017] Optionally, the signal detection circuit includes a third power input terminal, a third resistor, a fourth resistor, a fifth resistor, a first capacitor, a second capacitor and a second transistor;

[0018] A first end of the third resistor is an input end of the signal detection circuit, a second end of the third resistor is connected to the controlled end of the second transistor, a second end of the third resistor is connected to the first end of the fourth resistor, and a second end of the third resistor is connected to the first end of the first capacitor; a second end of the fourth resistor, an output end of the second transistor, and a second end of the first capacitor are grounded;

[0019] A first end of the fifth resistor is connected to the third power input terminal, a second end of the fifth resistor is the output terminal of the signal detection circuit, and a second end of the fifth resistor is connected to the input terminal of the second transistor;

[0020] A second end of the fifth resistor is connected to a first end of the second capacitor, and a second end of the second capacitor is grounded.

[0021] Optionally, the execution circuit includes a digital isolator and an active short-circuit execution circuit;

[0022] The power supply end of the digital isolator is the power supply end of the execution circuit, the signal input end of the digital isolator is the signal input end of the execution circuit, and the signal output end of the digital isolator is connected to the input end of the active short-circuit execution circuit.

[0023] Optionally, the low-voltage power supply power-off protection circuit further includes a voltage stabilizing circuit;

[0024] The input end of the voltage stabilizing circuit is connected to the first low-voltage power supply, and the output end of the voltage stabilizing circuit is connected to the first power supply input end.

[0025] Optionally, the voltage stabilizing circuit includes a sixth resistor, a voltage stabilizing diode and a third capacitor;

[0026] The first end of the sixth resistor is connected to the first low-voltage power supply, the second end of the sixth resistor is connected to the first power supply input end, the second end of the sixth resistor is connected to the cathode of the voltage-stabilizing diode and the first end of the third capacitor; the anode of the voltage-stabilizing diode and the second end of the third capacitor are grounded.

[0027] Optionally, the low-voltage power supply power-off protection circuit further includes an EMC filter circuit, an anti-reverse connection circuit and a filter circuit;

[0028] The input end of the EMC filter circuit is connected to the second low-voltage power supply, the output end of the EMC filter circuit is connected to the input end of the anti-reverse connection circuit, the output end of the anti-reverse connection circuit is connected to the input end of the filter circuit, and the output end of the filter circuit is connected to the second power supply input end.

[0029] To achieve the above object, the present invention further provides a low-voltage power supply power-off protection device, which includes the low-voltage power supply power-off protection circuit as described in any one of the above items.

[0030] According to the technical solution of the present invention, a power failure of the battery of the electric vehicle triggers the shutdown of the comparison switch circuit, which cuts off the power supply to the execution circuit, so that the execution circuit does not perform the ASC operation, thereby avoiding damage to the IGBT caused by performing the ASC operation under insufficient driving voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0032] Figure 1 This is a structural block diagram of an embodiment of a low-voltage power supply power-off protection circuit of the present invention;

[0033] Figure 2 for Figure 1 A schematic diagram of the circuit structure of an embodiment of a comparative switch circuit;

[0034] Figure 3 This is a structural block diagram of another embodiment of the low-voltage power supply power-off protection circuit of the present invention;

[0035] Figure 4 for Figure 3 A schematic diagram of the circuit structure of an embodiment of a signal detection circuit;

[0036] Figure 5 for Figure 3 A structural block diagram of an embodiment of an execution circuit;

[0037] Figure 6 This is a structural block diagram of another embodiment of the low-voltage power supply power-off protection circuit of the present invention.

[0038] Description of Figure Numbers:

[0039] Vin1 First low voltage power supply Vin2 Second low voltage power supply V1 First power input terminal V2 Second power input terminal V3 The third power input terminal IN Execution signal input terminal 10 Comparison switch circuit 20 Execution circuit 30 Signal detection circuit 40 voltage stabilization circuit 50 EMC filter circuit 60 Anti-reverse polarity circuit 70 filter circuit R1~R7 The first resistor to the seventh resistor T Zener diode C1~C3 First capacitor to third capacitor Q1 First transistor Q2 The second transistor 101 Comparison circuit 102 Switching Circuit 201 Digital Isolators 202 Active short-circuit execution circuit

[0040] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0042] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0043] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features specified as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0044] Figure 1 This is a structural block diagram of an embodiment of a low-voltage power supply power-off protection circuit of the present invention.

[0045] Reference Figure 1 The low-voltage power supply power-off protection circuit includes a first power input terminal V1 connected to a first low-voltage power supply Vin1, a second power input terminal V2 connected to a second low-voltage power supply Vin2, a comparison switch circuit 10 and an execution circuit 30;

[0046] The first comparison terminal of the comparison switch circuit 10 is connected to the first power input terminal V1, the second comparison terminal of the comparison switch circuit 10 is connected to the second power input terminal V2, the power input terminal of the comparison switch circuit 10 is connected to the first low-voltage power supply Vin1, and the power output terminal of the comparison switch circuit 10 is connected to the power terminal of the execution circuit 20.

[0047] The comparison switch circuit 10 has two states: off and on, and has the following characteristics: when the voltage at the first comparison terminal of the comparison switch circuit 10 is greater than the voltage at its second comparison terminal, the comparison switch circuit 10 is off; when the voltage at the first comparison terminal of the comparison switch circuit 10 is less than the voltage at its second comparison terminal, the comparison switch circuit 10 is on.

[0048] The execution circuit 20 is a hardware ASC (active short circuit) execution circuit, which is used to execute an ASC operation according to an externally input execution signal when the comparison switch circuit 10 is turned on.

[0049] The voltage input to the second power input terminal V2 is provided by the positive electrode (KL30) of the battery in the electric vehicle, that is, the second low-voltage power supply Vin2, through an EMC filter circuit 50, an anti-reverse connection circuit 60 and a filter circuit 70.

[0050] It should be noted that in this embodiment, the first low-voltage power source Vin1 connected to the first power input terminal V1 is derived from a weak-side power source that is unrelated to the hardware ASC trigger and has a relatively slow power-down rate. For example, if the hardware ASC trigger signal is provided by an SBC (single-board computer), and the second low-voltage power source Vin2 is also provided by the SBC, then the first low-voltage power source Vin1 connected to and supplying the first power input terminal V1 is selected from a low-voltage power source not generated by the SBC, and the low-voltage power source with the slowest power-down rate among the low-voltage power sources not generated by the SBC is selected. In other words, the first low-voltage power source supplying the first power input terminal V1 is not selected from the low-voltage power sources generated by the SBC. This configuration prevents common cause failures in the event of a battery failure in a non-electric vehicle, since the first low-voltage power source Vin1 connected to the first power input terminal V1 is unrelated to the hardware ASC trigger, allowing the execution circuit 20 to perform the ASC operation normally.

[0051] Optionally, in a specific embodiment, the first power input terminal V1 can be directly connected to the power input terminal of the comparison switch circuit 10, so that the voltage input by the first power input terminal V1 serves as both a reference voltage for the comparison switch circuit 10 and a power supply for the execution circuit 20. Of course, the power input terminal of the comparison switch circuit 10 can also be connected to or communicated with other low-voltage power supplies, wherein the other low-voltage power supplies mentioned here are selected from weak-voltage side power supplies that are not related to the hardware ASC triggering and have a relatively slow power-off speed.

[0052] The specific operating principle is as follows: When the electric vehicle's KL30 (the positive battery terminal) is in a non-deenergized state, that is, when the second low-voltage power supply Vin2 is not deenergized, the voltage input to the second power input terminal V2 is normal. Specifically, the voltage input to the second power input terminal V2 is greater than the voltage input to the first power input terminal V1, and the comparison switch circuit 10 is turned on. When the comparison switch circuit 10 is in the on state, the first power input terminal V1 supplies power to the execution circuit 20 through the turned-on comparison switch circuit 10. In this case, if an external execution signal is input to the execution circuit 20, the execution circuit 20 performs the ASC operation. If no external execution signal is input to the execution circuit 20, the execution circuit 20 does not perform the ASC operation.

[0053] When the KL30 of an electric vehicle loses power, the voltage input to the second power input terminal V2 gradually decreases. When the voltage input to the second power input terminal V2 is lower than the voltage input to the first power input terminal V1, it indicates that the driving voltage is insufficient. Performing the ASC operation under insufficient driving voltage conditions can damage the IGBT. At this point, the comparison switch circuit 10 switches from an on state to an off state. When the comparison switch circuit 20 is turned off, the electrical connection between the first power input terminal V1 and the execution circuit 20 is disconnected, and the execution circuit 20 is powered off. After the execution circuit 20 is powered off, regardless of whether an external execution signal is input to the execution circuit 20, the execution circuit 20 does not perform the ASC operation. With this configuration, when the KL30 loses power, the power supply to the execution circuit 20 is cut off, preventing the execution circuit 20 from performing the ASC operation. This prevents the ASC operation from being performed under insufficient driving voltage due to the KL30 power loss, which in turn damages the IGBT. Furthermore, this configuration eliminates the need for a backup driving power supply, thereby saving the cost of the electric vehicle.

[0054] According to the technical solution of the present invention, when the battery of the electric vehicle loses power, the comparison switch circuit 10 is triggered to shut down. The power supply of the execution circuit 20 is cut off by shutting down the comparison switch circuit 10, so that the execution circuit 20 cannot perform the ASC operation, thereby avoiding the IGBT from being damaged due to the execution of the ASC operation under the condition of insufficient driving voltage, and no backup driving power supply is required, which can reduce the cost of the electric vehicle and reduce the complexity of the PCB design of the electric vehicle.

[0055] Optional, see Figure 2 In one embodiment, the comparison switch circuit 10 includes a comparison circuit 101 and a switch circuit 102;

[0056] The positive input terminal of the comparison circuit 101 is the first comparison terminal of the comparison switch circuit 10, the negative input terminal of the comparison circuit 101 is the second comparison terminal of the comparison switch circuit 10, and the output terminal of the comparison circuit 101 is connected to the controlled terminal of the switch circuit 102; the power input terminal of the switch circuit 102 is the power input terminal of the comparison switch circuit 10, and the power output terminal of the switch circuit 102 is the power output terminal of the comparison switch circuit 10.

[0057] The comparison circuit 101 may be selected as a comparator, and the comparison circuit 101 has the following characteristics: when the voltage at the positive input terminal of the comparison circuit 101 is greater than the voltage at its negative input terminal, the comparison circuit 101 outputs a high level; when the voltage at the positive input terminal of the comparison circuit 101 is less than the voltage at its negative input terminal, the comparison circuit 101 outputs a low level.

[0058] The switch circuit 102 has two states, OFF and ON, and can be implemented by a circuit composed of a transistor or a MOS transistor. In this embodiment, the switch circuit 102 can be a switch circuit that is turned on at a low level.

[0059] It is understandable that in other embodiments, if the positive input terminal of the comparison circuit 101 is connected to the second power input terminal V2, and the negative input terminal of the comparison circuit 102 is connected to the first power input terminal V1, the switch circuit 102 can be selected as a high-level conductive switch circuit.

[0060] The specific operating principle is as follows: When the electric vehicle's KL30 is in a non-power-down state, the voltage input to the second power input terminal V2 is greater than the voltage input to the first power input terminal V1. Therefore, the voltage at the positive input terminal of the comparison circuit 101 is less than the voltage at its negative input terminal. The comparison circuit 101 outputs a low-level electrical signal to the controlled terminal of the switch circuit 102, turning on the switch circuit 102. When the switch circuit 102 is in the on state, the first power input terminal V1 supplies power to the execution circuit 20 through the turned-on switch circuit 102. In this case, if an external execution signal is input to the execution circuit 20, the execution circuit 20 performs the ASC operation. If no external execution signal is input to the execution circuit 20, the execution circuit 20 does not perform the ASC operation.

[0061] When the KL30 of the electric vehicle loses power, the voltage input to the second power input terminal V2 gradually decreases. When the voltage input to the second power input terminal V2 is lower than the voltage input to the first power input terminal V1, the voltage at the positive input terminal of the comparison circuit 101 becomes greater than the voltage at its negative input terminal. The comparison circuit 101 outputs a high-level electrical signal to the controlled terminal of the switch circuit 102, causing the switch circuit 102 to switch from the on state to the off state. When the switch circuit 102 is turned off, the electrical connection between the first power input terminal V1 and the execution circuit 20 is disconnected, and the execution circuit 20 is powered off. After the execution circuit 20 is powered off, regardless of whether an external execution signal is input to the execution circuit 20, the execution circuit 20 does not perform the ASC operation. This embodiment stops the execution circuit 20 from performing the ASC operation by cutting off the power supply to the execution circuit 20 when the KL30 loses power. This prevents damage to the IGBT caused by performing the ASC operation when the drive voltage is insufficient.

[0062] In one embodiment, the switch circuit 102 may be composed of a MOS transistor. The MOS transistor in the switch circuit 102 is a P-channel MOS transistor, which is controlled to be turned off by a high-level electrical signal and to be turned on by a low-level signal. Therefore, when the switch circuit 102 is turned off, the execution circuit 20 cannot perform the ASC operation. In actual applications, the MOS transistor in the switch circuit 102 may also be an N-channel MOS transistor. In this case, the negative input of the comparison circuit 101 is connected to the first power input terminal V1, and the positive input is connected to the second power input terminal V2. The comparison circuit 101 can be controlled to be turned off by outputting a low-level electrical signal and to be turned on by outputting a high-level signal. However, this will increase the cost. Specifically, since the low level output by the comparison circuit 101 is relative to the ground, and the source of the MOS transistor is not grounded, a non-common ground conversion is required, which may require the addition of additional hardware. Therefore, if the positive input terminal of the comparison circuit 101 is connected to the first power input terminal V1 and the negative input terminal of the comparison circuit 101 is connected to the second power input terminal V2, the switch circuit 102 is selected as a low-level conductive switch circuit, which can reduce costs.

[0063] Optionally, the switch circuit 102 may also be formed by a transistor. The transistor in the switch circuit 102 may be a PNP transistor, and the comparison circuit 101 may control the PNP transistor to turn off via a high-level electrical signal. The transistor in the switch circuit 102 may also be an NPN transistor. In this case, the negative input of the comparison circuit 101 is connected to the first power input terminal V1, and the positive input is connected to the second power input terminal V2. The comparison circuit 101 may control its shutdown by outputting a low-level electrical signal and its conduction by outputting a high-level signal. However, this will increase the cost. Specifically, since the low-level output of the comparison circuit 101 is relative to the ground, and the emitter of the transistor is not grounded, a non-common ground conversion is required, which may require the addition of other hardware.

[0064] Optional, see Figure 2 In one embodiment, the switch circuit 102 includes a first resistor R1, a second resistor R2 and a first transistor Q1;

[0065] The first end of the first resistor R1 is connected to the first power input terminal V1, the second end of the first resistor R1 is connected to the first end of the second resistor R2, and the first end of the second resistor R2 is the controlled end of the switch circuit 102. At the same time, the second end of the second resistor R2 is connected to the controlled end of the first transistor Q1; the input end of the first transistor Q1 is the power input end of the switch circuit 102, and the output end of the first transistor Q1 is the power output end of the switch circuit 102.

[0066] The first transistor Q1 can be a P-MOS transistor or a PNP transistor.

[0067] The specific working principle is as follows: when the KL30 of the electric vehicle is in a non-power-off state, the comparison circuit 101 outputs a low-level electrical signal to the controlled end of the first transistor Q1, the first transistor Q1 is turned on, and the first power input end V1 supplies power to the execution circuit 20 through the turned-on first transistor Q1.

[0068] When KL30 is powered off, the comparison circuit 101 outputs a high-level electrical signal to the controlled terminal of the first transistor Q1, the first transistor Q1 is turned off, the electrical connection between the first power input terminal V1 and the execution circuit 20 is disconnected, and the execution circuit 20 is powered off.

[0069] Optional, see Figure 3 In one embodiment, the low voltage power supply power-off protection circuit further includes a signal detection circuit 30 and an execution signal input terminal IN;

[0070] The input end of the signal detection circuit 30 is connected to the execution signal input end IN, and the output end of the signal detection circuit 30 is connected to the signal input end of the execution circuit 20 .

[0071] The signal detection circuit 30 is used to detect whether there is an execution signal input to the execution signal input terminal IN, and when there is an execution signal input, the execution signal is transmitted to the execution circuit 20 to trigger the execution circuit 20 to perform the ASC operation. It should be noted that due to the power failure of the battery of the electric vehicle, there will be multiple power-off and power-on situations, that is, jitter, and the power-off and power-on process is often accompanied by a series of initial processes such as chip initialization. In this process, once the ASC signal is enabled and the driving voltage has not been fully established, the IGBT will not be saturated and the ASC operation will be performed. Therefore, in order to avoid the situation where the IGBT is not saturated and the ASC operation is performed, the delay time of the signal detection circuit 30 is set to be greater than the delay time required for the driving voltage to rise to meet the saturation conduction of the IGBT.

[0072] Optional, see Figure 4 In one embodiment, the signal detection circuit 30 includes a third power input terminal V3, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first capacitor C1, a second capacitor C2, and a second transistor Q2;

[0073] A first end of the third resistor R3 is an input end of the signal detection circuit 30, and a second end of the third resistor R3 is connected to the controlled end of the second transistor Q2. A second end of the third resistor R3 is connected to a first end of a fourth resistor R4, and a second end of the third resistor R3 is connected to a first end of the first capacitor. A second end of the fourth resistor R4, an output end of the second transistor Q2, and a second end of the first capacitor C1 are all grounded.

[0074] A first end of the fifth resistor R5 is connected to the third power input terminal V3, a second end of the fifth resistor R5 is the output terminal of the signal detection circuit 30, and a second end of the fifth resistor R5 is connected to the input terminal of the second transistor Q2; and a second end of the fifth resistor R5 is connected to a first end of the second capacitor C2, and a second end of the second capacitor C2 is grounded.

[0075] In this embodiment, the third power input terminal V3 can be connected to the first low-voltage power supply Vin1, or other weak-current side power supply that is independent of the triggering of the hardware ASC and has a relatively slow power-off speed can be used (for example, the hardware ASC signal is triggered by the SBC, and the low-voltage power supply VAUX is also generated by the SBC, then the power supply does not use the VAUX power supply generated by the SBC).

[0076] In this embodiment, the second transistor Q2 can be a triode or a MOS transistor. For the sake of convenience, the following takes the second transistor Q2 as a transistor that is turned on at a high level, and takes the execution circuit 20 performing the ASC operation when receiving a high-level electrical signal as an example for explanation.

[0077] The specific working principle is as follows: when a high level electrical signal is input to the execution signal input terminal IN, the second transistor Q2 is turned on. When the second transistor Q2 is turned on, the signal input terminal of the execution circuit 20 is at a low level, and the execution circuit 20 does not perform the ASC operation.

[0078] When a low-level electrical signal is input to the execution signal input terminal IN, the second transistor Q2 is turned off. When the second transistor Q2 is turned off, the signal input terminal of the execution circuit 20 is pulled up to a high level by the fifth resistor R5. If the comparison switch circuit 10 is also in the on state at this time, the execution circuit 20 performs the ASC operation.

[0079] Optionally, the following description will be made by taking the second transistor Q2 as a transistor that is turned on at a low level, and taking the execution circuit 20 performing the ASC operation when receiving a low-level electrical signal as an example.

[0080] The specific operating principle is as follows: When a low-level electrical signal is input to the execution signal input terminal IN, the second transistor Q2 is turned on. When the second transistor Q2 is turned on, the signal input terminal of the execution circuit 20 is at a low level. If the comparison switch circuit 10 is also in the on state at this time, the execution circuit 20 performs the ASC operation.

[0081] When a high level electrical signal is input to the execution signal input terminal IN, the second transistor Q2 is turned off. When the second transistor Q2 is turned off, the signal input terminal of the execution circuit 20 is pulled up to a high level by the fifth resistor R5, and the execution circuit 20 does not perform the ASC operation.

[0082] It should be noted that two conditions must be met for the execution circuit 20 to perform the ASC operation. First, the comparison switch circuit 10 is turned on and the first power input terminal V1 supplies power to the execution circuit 20. Second, the execution circuit 20 receives an execution signal transmitted by the signal detection circuit 30 indicating the execution of the ASC operation.

[0083] Optional, see Figure 5 In one embodiment, the execution circuit 20 includes a digital isolator 201 and an active short-circuit execution circuit 202;

[0084] The power supply terminal of the digital isolator 201 is the power supply terminal of the execution circuit 20 , the signal input terminal of the digital isolator 201 is the signal input terminal of the execution circuit 20 , and the signal output terminal of the digital isolator 201 is connected to the input terminal of the active short-circuit execution circuit 202 .

[0085] The digital isolator 201 is used to transmit the execution signal to the active short-circuit execution circuit 202. It has strong anti-interference ability and is used to ensure the stability and reliability of the system.

[0086] The active short circuit execution circuit 202 is used to execute an ASC operation.

[0087] The specific operating principle is as follows: When KL30 is in the non-power-down state, the comparison switch circuit 10 is turned on. When the comparison switch circuit 10 is turned on, the first power input terminal V1 supplies power to the digital isolator 201 through the turned-on comparison switch circuit 10. In this case, if the signal detection circuit 30 inputs an execution signal to the digital isolator 201, the digital isolator 201 transmits the execution signal to the active short circuit execution circuit 202, thereby driving the active short circuit execution circuit 202 to perform the ASC operation.

[0088] When KL30 is powered off, the voltage input to the second power input terminal V2 gradually decreases. When the voltage input to the second power input terminal is lower than the voltage input to the first power input terminal V1, the comparison switch circuit 10 is turned off and the digital isolator 201 is powered off. In this case, regardless of whether the signal detection circuit 30 detects the execution signal, the digital isolator 201 cannot transmit the execution signal to the active short-circuit execution circuit 202, and the active short-circuit execution circuit 202 does not perform the ASC operation.

[0089] Optional, see Figure 6 In one embodiment, the low-voltage power supply power-off protection circuit further includes a voltage stabilizing circuit 40; the input end of the voltage stabilizing circuit 40 is connected to the first low-voltage power supply Vin1, and the output end of the voltage stabilizing circuit 40 is connected to the first power supply input end V1.

[0090] The voltage stabilizing circuit 40 is used to stabilize the voltage output by the first low-voltage power supply Vin1 to a certain voltage, thereby providing a reference voltage for the comparison switch circuit 10 and powering the execution circuit 20 .

[0091] Optional, see Figure 6 In one embodiment, the voltage stabilizing circuit 40 includes a sixth resistor R6, a voltage stabilizing diode T, and a third capacitor C3; a first end of the sixth resistor R6 is connected to the first low-voltage power supply Vin1, a second end of the sixth resistor R6 is connected to the cathode of the voltage stabilizing diode T and the first end of the third capacitor C3; an anode of the voltage stabilizing diode T and a second end of the third capacitor C3 are grounded.

[0092] The voltage stabilizing diode T is used to stabilize the voltage input from the first low-voltage power supply Vin1 to a certain voltage.

[0093] Optional, see Figure 6 In one embodiment, the low-voltage power supply power-off protection circuit further includes an EMC filter circuit 50, an anti-reverse connection circuit 60 and a filter circuit 70;

[0094] The input end of the EMC filter circuit 50 is connected to the second low-voltage power supply Vin2, the output end of the EMC filter circuit 50 is connected to the input end of the anti-reverse connection circuit 60, the output end of the anti-reverse connection circuit 60 is connected to the input end of the filter circuit 70, and the output end of the filter circuit 70 is connected to the second power supply input end V2.

[0095] The EMC filter circuit 50 is used to eliminate and suppress electromagnetic interference in the electric energy output by the second low-voltage power supply Vin2.

[0096] The anti-reverse connection circuit 60 is used to prevent the back-end circuit from being damaged due to the reverse connection of the positive and negative poles of the second low-voltage power supply Vin2. Specifically, when the positive and negative poles of the second low-voltage power supply Vin2 are connected correctly, the electric energy output by the second low-voltage power supply Vin2 can be transmitted to the back-end circuit. When the positive and negative poles of the second low-voltage power supply Vin2 are not connected correctly, the back-end circuit is powered off.

[0097] The filter circuit 70 is used to filter ripple in the power output by the second low-voltage power supply Vin2. Optionally, the filter circuit 70 includes a seventh resistor R7 and a fourth capacitor C4. The first end of the seventh resistor R7 is connected to the output terminal of the anti-reverse connection circuit 60, and the first end of the seventh resistor R7 is connected to the first end of the fourth capacitor C4, and the second end of the fourth capacitor C4 is grounded. The second end of the seventh resistor R7 is connected to the second power supply input terminal V2, that is, the second end of the seventh resistor R7 is connected to the second comparison terminal of the comparison switch circuit 10.

[0098] The present invention also provides a low-voltage power supply power-off protection device, which includes the low-voltage power supply power-off protection circuit as described above. The detailed structure of the low-voltage power supply power-off protection circuit can be referred to the above embodiment and will not be described in detail here. It can be understood that since the above low-voltage power supply power-off protection circuit is used in the low-voltage power supply power-off protection device of the present invention, the embodiments of the low-voltage power supply power-off protection device of the present invention include all technical solutions of all embodiments of the above low-voltage power supply power-off protection circuit, and the technical effects achieved are also exactly the same, which will not be described in detail here.

[0099] The above descriptions are merely optional embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present description and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A low voltage power supply power-off protection circuit, characterized in that: The low-voltage power supply power-off protection circuit includes a first power supply input terminal connected to a first low-voltage power supply, a second power supply input terminal connected to a second low-voltage power supply, a comparison switch circuit and an execution circuit; The first comparison terminal of the comparison switch circuit is connected to the first power input terminal, the second comparison terminal of the comparison switch circuit is connected to the second power input terminal, the power input terminal of the comparison switch circuit is connected to the first low-voltage power supply, and the power output terminal of the comparison switch circuit is connected to the power terminal of the execution circuit; The comparison switch circuit is used to disconnect the input power of the execution circuit according to a predetermined method when the second low-voltage power supply is powered off, so that the execution circuit stops performing the active short-circuit operation.

2. The low voltage power supply power-off protection circuit according to claim 1, wherein: The comparison switch circuit includes a comparison circuit and a switch circuit; The positive input terminal of the comparison circuit is the first comparison terminal of the comparison switch circuit, the negative input terminal of the comparison circuit is the second comparison terminal of the comparison switch circuit, and the output terminal of the comparison circuit is connected to the controlled terminal of the switch circuit; The power input end of the switch circuit is the power input end of the comparison switch circuit, and the power output end of the switch circuit is the power output end of the comparison switch circuit.

3. The low voltage power supply power-off protection circuit according to claim 2, wherein: The switch circuit includes a first resistor, a second resistor and a first transistor; The first end of the first resistor is connected to the first power input terminal, the second end of the first resistor is connected to the first end of the second resistor, the first end of the second resistor is the controlled end of the switch circuit, and the second end of the second resistor is connected to the controlled end of the first transistor; The input end of the first transistor is the power input end of the switch circuit, and the output end of the first transistor is the power output end of the switch circuit.

4. The low voltage power supply power-off protection circuit according to claim 1, wherein: The low-voltage power supply power-off protection circuit further includes a signal detection circuit and an execution signal input terminal; The input end of the signal detection circuit is connected to the execution signal input end, and the output end of the signal detection circuit is connected to the signal input end of the execution circuit.

5. The low voltage power supply power-off protection circuit according to claim 4, characterized in that: The signal detection circuit includes a third power input terminal, a third resistor, a fourth resistor, a fifth resistor, a first capacitor, a second capacitor and a second transistor; A first end of the third resistor is an input end of the signal detection circuit, a second end of the third resistor is connected to the controlled end of the second transistor, a second end of the third resistor is connected to the first end of the fourth resistor, and a second end of the third resistor is connected to the first end of the first capacitor; a second end of the fourth resistor, an output end of the second transistor, and a second end of the first capacitor are grounded; A first end of the fifth resistor is connected to the third power input terminal, a second end of the fifth resistor is the output terminal of the signal detection circuit, and a second end of the fifth resistor is connected to the input terminal of the second transistor; A second end of the fifth resistor is connected to a first end of the second capacitor, and a second end of the second capacitor is grounded.

6. The low voltage power supply power-off protection circuit according to claim 4, characterized in that: The execution circuit includes a digital isolator and an active short-circuit execution circuit; The power supply end of the digital isolator is the power supply end of the execution circuit, the signal input end of the digital isolator is the signal input end of the execution circuit, and the signal output end of the digital isolator is connected to the input end of the active short-circuit execution circuit.

7. The low-voltage power supply power-off protection circuit according to any one of claims 1 to 6, characterized in that: The low-voltage power supply power-off protection circuit also includes a voltage stabilizing circuit; The input end of the voltage stabilizing circuit is connected to the first low-voltage power supply, and the output end of the voltage stabilizing circuit is connected to the first power supply input end.

8. The low voltage power supply power-off protection circuit according to claim 7, wherein: The voltage stabilizing circuit includes a sixth resistor, a voltage stabilizing diode and a third capacitor; The first end of the sixth resistor is connected to the first low-voltage power supply, the second end of the sixth resistor is connected to the first power supply input end, the second end of the sixth resistor is connected to the cathode of the voltage-stabilizing diode and the first end of the third capacitor; the anode of the voltage-stabilizing diode and the second end of the third capacitor are grounded.

9. The low voltage power supply power-off protection circuit according to claim 7, wherein: The low-voltage power supply power-off protection circuit also includes an EMC filter circuit, an anti-reverse connection circuit and a filter circuit; The input end of the EMC filter circuit is connected to the second low-voltage power supply, the output end of the EMC filter circuit is connected to the input end of the anti-reverse connection circuit, the output end of the anti-reverse connection circuit is connected to the input end of the filter circuit, and the output end of the filter circuit is connected to the second power supply input end.

10. A low voltage power supply power failure protection device, characterized in that: The low-voltage power supply power-off protection device comprises the low-voltage power supply power-off protection circuit according to any one of claims 1 to 9.

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