CN112134269B - Protection circuit, circuit protection device and motor control system - Google Patents

Protection circuit, circuit protection device and motor control system Download PDF

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Publication number
CN112134269B
CN112134269B CN202011039157.7A CN202011039157A CN112134269B CN 112134269 B CN112134269 B CN 112134269B CN 202011039157 A CN202011039157 A CN 202011039157A CN 112134269 B CN112134269 B CN 112134269B
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circuit
electrically connected
input
resistor
voltage
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CN112134269A (en
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刘学
张俊杰
刘超
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Jiangsu Leili Motor Co Ltd
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Jiangsu Leili Motor Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/02—Details
    • H02H3/025—Disconnection after limiting, e.g. when limiting is not sufficient or for facilitating disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/08—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors
    • H02H7/085—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors against excessive load
    • H02H7/0854—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors against excessive load responsive to rate of change of current, couple or speed, e.g. anti-kickback protection

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

The invention relates to a protection circuit, a circuit protection device and a motor control system, wherein the protection circuit comprises: the first comparison circuit is provided with a first input end and a first output end, the first input end is electrically connected with the input voltage, and the first output end is electrically connected with the execution circuit; a second comparator circuit having a second input terminal and a second output terminal, the second input terminal being electrically connected to the input voltage; the self-locking circuit is provided with a third input end and a third output end, the third input end is electrically connected with the second output end, and the third output end is electrically connected with the first input end and the second input end, wherein the first comparison circuit is provided with a first threshold value and a second threshold value smaller than the first threshold value, when the input voltage is larger than or equal to the first threshold value, the first output end outputs a first level turnover signal, and the execution circuit receives the first level turnover signal so as to close a power device in the execution circuit.

Description

Protection circuit, circuit protection device and motor control system
Technical Field
The invention relates to a protection circuit, a protection device with the protection circuit and a motor control system.
Background
Power devices (e.g., power devices) have been widely used in the field of power electronic control, and the controllability and high-speed switching characteristics of the power devices can achieve high efficiency of power supply and complex control of motors. In practical applications, it is necessary to ensure not only the reliability of the system, but also to protect the expensive power devices and their loads, which requires some protection measures for the control system.
The control of the current mainly comprises current-limiting protection control, for example, when the motor is started or runs at a low speed, because the back electromotive force is very small, the current is very large especially during starting, and if the current is not limited at the moment, the power device and the motor are easily damaged by the overlarge current; and overcurrent protection control, in which, for example, a very large short-circuit current is instantaneously generated when an overcurrent fault occurs in a circuit, and a power device and a motor can be damaged in a very short time, so that it is necessary to control the overcurrent.
Therefore, a protection circuit which has the functions of current-limiting protection control and overcurrent protection control, is high in response speed and cost-effective, a protection device with the protection circuit and a motor control system need to be designed.
Disclosure of Invention
The present invention addresses the above-mentioned problems and needs, and provides a protection circuit, a protection device having the protection circuit, and a motor control system, which are capable of solving the above-mentioned problems and having other technical advantages due to the following technical solutions.
According to an aspect of the present invention, there is provided a protection circuit that performs a circuit protection operation based on an input voltage, the protection circuit including a first comparison circuit having a first input terminal and a first output terminal, the first input terminal being electrically connected to the input voltage, the first output terminal being electrically connected to an execution circuit; a second comparator circuit having a second input terminal and a second output terminal, the second input terminal being electrically connected to the input voltage; and the self-locking circuit is provided with a third input end and a third output end, the third input end is electrically connected with the second output end, and the third output end is electrically connected with the first input end and the second input end. The first comparison circuit has a first threshold and a second threshold smaller than the first threshold, when the input voltage is greater than or equal to the first threshold, the first output end outputs a first level flip signal, and the execution circuit receives the first level flip signal so as to close a power device in the execution circuit; when the input voltage is less than or equal to a second threshold value, the first output end outputs a second level turnover signal, and the execution circuit receives the second level turnover signal so as to start a power device in the execution circuit. The second comparison circuit has a third threshold larger than the first threshold, when the input voltage is larger than the third threshold, the second output end outputs a third level flip signal, the self-locking circuit receives the third level flip signal and latches the voltages of the first input end and the second input end to a preset voltage, and the preset voltage is larger than the third threshold, so that the first comparison circuit outputs the first level flip signal to close a power device in the execution circuit. The self-locking circuit is configured to receive an external unlocking signal so as to release the latching state, and the voltages of the first input end and the second input end are recovered to the input voltage.
With the above features, when the input voltage is equal to or greater than the first threshold or the input voltage is equal to or less than the second threshold, the first output terminal will output the current-limiting control logic, and the execution circuit processes the received logic and controls the power device in the execution circuit to be turned on or off to maintain the voltage and/or current in the circuit (e.g., the load) stable.
When overcurrent faults occur, the self-locking circuit is triggered through the second comparison circuit, and the voltages of the first input end and the second input end are latched to the preset voltage. The scheme simplifies the circuit to the maximum extent under the condition of simultaneously meeting two functions, not only reduces the complexity of the circuit, but also optimizes the design cost.
In some examples, the first comparison circuit includes a first comparison voltage U R1 A comparator U2, a resistor R4, a resistor R5 and a resistor R6, a first comparison voltage U R1 Is electrically connected with the positive input end of the comparator U2, one end of the resistor R4 is electrically connected with the input voltage, the other end of the resistor R4 is electrically connected with the negative input end of the comparator U2, one end of the resistor R5 is electrically connected with the positive input end of the comparator U2, the other end of the resistor R5 is electrically connected with the output end of the comparator U2 and one end of the resistor R6, and the other end of the resistor R6 is electrically connected with the direct-current voltage U6 C And (6) electrically connecting.
In some examples, the second comparison circuit includes a second comparison voltage U R2 A comparator U1, a resistor R1, a resistor R2 and a resistor R3, a second comparison voltage U R2 Is electrically connected with the positive input end of the comparator U1, one end of the resistor R1 is electrically connected with the input voltage, the other end of the resistor R1 is electrically connected with the negative input end of the comparator U1, one end of the resistor R2 is electrically connected with the positive input end of the comparator U1, the other end of the resistor R2 is electrically connected with the output end of the comparator U1 and one end of the resistor R3, and the other end of the resistor R3 is electrically connected with the direct-current voltage U3 C And (6) electrically connecting.
In some examples, the self-locking circuit includes a transistor Q1 and a transistor Q2, a base of the transistor Q1 is electrically connected to an output terminal of the comparator U1, and an emitter of the transistor Q1 is connected to the predetermined voltage U1 0 And the collector of the triode Q1 is electrically connected with the emitter of the triode Q2, the base of the triode Q2 is electrically connected with an external unlocking signal source, and the collector of the triode Q2 is electrically connected with the first input end and the second input end.
In some examples, transistor Q1 and transistor Q2 are PNP transistors.
In some examples, the protection circuit further comprises a controller including a first control port, the first control port being an unlock signal source that emits the unlock signal.
In some examples, the controller further includes a second control port electrically connected to the second output terminal, and configured to receive the third level-reversal signal to trigger the controller to start counting once and start timing at the same time, and after timing for a preset time, the first control port of the controller issues an unlocking signal to release the latched state.
In some examples, when the input voltage is still greater than the third threshold, the latching circuit is triggered again and the brake pin of the controller triggers the count again and the count is incremented by one, and when the count of the controller is greater than the preset count, the controller stops outputting the unlock signal and indicates that the circuit is malfunctioning.
In some examples, the first level-flip signal is a flip from a high level to a low level, the second level-flip signal is a flip from a low level to a high level, and the third level-flip signal is a flip from a high level to a low level.
In some examples, the protection circuit further includes a sampling circuit configured to sample a voltage of the load, an output of the sampling circuit being connected to inputs of the first and second comparison circuits.
In some examples, the protection circuit further includes an amplification circuit configured to amplify and output the voltage signal of the sampling circuit as an input voltage, the amplification circuit being connected between an output terminal of the sampling circuit and input terminals of the first and second comparison circuits.
According to another aspect of the present invention, there is provided a circuit protection device comprising a protection circuit as described above.
According to a further aspect of the present invention there is provided a motor control system comprising a circuit protection device as hereinbefore described.
In summary, the protection circuit provided by the invention integrates the current limiting protection function and the overcurrent protection function, the latch of the overcurrent state is realized through the self-locking circuit, the circuit is simplified to the maximum extent under the condition of simultaneously meeting the two functions, the complexity of the circuit is reduced, and the design cost is optimized. Furthermore, the detection of the power device from current flow to perform the shutdown action is performed entirely by hardware circuitry, thereby avoiding the time delay associated with using a software processing scheme. Tests show that the execution time of hardware can be controlled within 5 microseconds by selecting the response speed of the device, the response speed is high, and the overcurrent bearing time of the power device is sufficiently met. The circuit protection device and the motor control system provided by the invention have the same advantages and benefits due to the protection circuit.
The following description of the preferred embodiments for carrying out the present invention will be made in detail with reference to the accompanying drawings so that the features and advantages of the present invention can be easily understood.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments of the present invention will be briefly described below. Wherein the drawings are only for purposes of illustrating some embodiments of the invention and are not to be construed as limiting the invention to all embodiments thereof.
Fig. 1 is a block diagram of a protection circuit according to a first embodiment of the present invention;
fig. 2 is a block diagram of a protection circuit according to a second embodiment of the present invention;
fig. 3 is a block diagram of a protection circuit according to a third embodiment of the present invention;
fig. 4 is a block diagram of a protection circuit according to a fourth embodiment of the present invention;
FIG. 5 is a schematic diagram of at least one embodiment of a protection circuit according to the present disclosure;
FIG. 6 illustrates a graph of a load voltage and a comparator output signal of a protection circuit in accordance with at least one embodiment of the present disclosure;
FIG. 7 illustrates a graph of a load waveform and a comparator output signal of a protection circuit in accordance with at least one embodiment of the present disclosure;
fig. 8 shows a graph of a load waveform and a comparator output signal of a protection circuit according to a further embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the technical solutions of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of specific embodiments of the present invention. Like reference symbols in the various drawings indicate like elements. It should be noted that the described embodiments are only some embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without inventive step, are within the scope of protection of the invention.
Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in the description and claims of the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. Also, the use of the terms "a" or "an" and the like do not necessarily denote a limitation of quantity. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.
In the motor control system, control of electric current is roughly classified into the following two types:
one is current-limiting protection control, for example, when the motor is started or runs at low speed, because the back electromotive force is very small, especially the current is very large during starting, and if the current is not limited at this time, the power device and the motor are easily damaged by the excessive current. The current limiting protection control method comprises the steps of comparing the current flowing through the motor with a preset current limiting value, closing the conducted power device when the current of the motor rises and is larger than the current limiting comparison value, reducing the current flowing through the motor due to the fact that the power device is closed, conducting the power device again when the current is smaller than the current limiting value, and keeping the current of the motor close to the preset current limiting value in the reciprocating mode.
The other is overcurrent protection control, and some extreme fault phenomena often occur in a motor control system, such as simultaneous conduction of an upper bridge arm and a lower bridge arm on a power inverter side, short circuit of a motor winding and the like. When these faults occur, a very large short-circuit current is generated instantaneously, and the power device and the motor body can be damaged in a very short time. The overcurrent protection control also sets an overcurrent comparison value, and because the fault current speed is high and the energy is high, when the fault current occurs once, the power device needs to be quickly turned off and the fault state needs to be kept until the fault is relieved.
Finally, the two current control modes are finally realized by switching on and off the power device.
The two types of current control are mainly different in that the current limiting protection control limits the output current of the motor control system to a reliable maximum constant value and can continuously output. Overcurrent protection control requires that the motor control system be able to quickly shut down the power devices to block current output when a fault current occurs. The current limiting control ensures that the current can be output to the maximum extent on the premise of reliability, and the overcurrent ensures the reliability by cutting off the current.
The sampling of motor current usually adopts low resistance resistor to sample current signal, it converts the current signal into voltage signal proportional to it, and then amplifies it by proportional operational amplifier, the amplified current signal is sent to the input end of comparator and compared with preset comparison threshold, when the current is greater than the preset threshold of comparator, the output level of comparator is turned over. The output of the comparator is connected with a pin of the MCU control main chip and triggers current interruption, and the power device is controlled to be switched on and off through interruption execution software so as to control the current. The design using the combination of software and hardware has the advantage that the circuit can be greatly simplified, but the time delay generated by sampling, comparing and then responding to the software and executing the current signal is fatal to the power device with the overcurrent protection capability of only a few microseconds, and the delay is mainly generated by responding to the software and executing the software.
In addition, because the current limiting control and the overcurrent control are performed differently on the power device, different control circuits need to be designed respectively for the control system to simultaneously implement the two functions, which complicates the control circuit and increases the number of components used. Considering that the maximum continuous output current value of the power device is far smaller than the short-time tolerable overcurrent value, the current-limiting protection comparison threshold value is set smaller than the overcurrent protection comparison threshold value, which means that the current-limiting protection is necessarily simultaneously performed when the overcurrent protection occurs. Therefore, in order to simplify the circuit design, the two functions can be combined into one, which requires that the simplified current control circuit can identify which current control state is, and the power device is frequently switched to limit the current at a constant value when a current limiting control request occurs; and performing state latching and turning off the power device when an overcurrent control request occurs.
Based on the requirements, the protection circuit provided by the invention integrates a current limiting protection function and an overcurrent protection function, realizes latching of an overcurrent state through the self-locking circuit, and maximally simplifies the circuit under the condition of simultaneously meeting the two functions.
Preferred embodiments of the protection circuit according to the present disclosure are described below in detail with reference to the accompanying drawings. Fig. 1 is a block diagram of a protection circuit according to a first embodiment of the present invention. Fig. 2 is a block diagram of a protection circuit according to a second embodiment of the present invention. Fig. 3 is a block diagram of a protection circuit according to a third embodiment of the present invention. Fig. 4 is a block diagram of a protection circuit according to a fourth embodiment of the present invention. Fig. 5 is a schematic structural diagram of at least one embodiment of a protection circuit according to the present invention.
First, referring to fig. 1, a protection circuit provided by at least one embodiment of the present disclosure performs a circuit protection operation based on an input voltage, and includes a first comparison circuit 1, a second protection circuit 2, a self-locking circuit 3, and an execution circuit 4.
The first comparison circuit 1 has a first input terminal electrically connected to the input voltage and a first output terminal electrically connected to the execution circuit 4;
the second comparator circuit 2 has a second input and a second output, the second input being electrically connected to the input voltage and thus also to the first input of the first comparator circuit 1.
Examples of the first and/or second comparison circuit 1, 2 may comprise a comparator having a positive input and a negative input, and an output of the comparator. The selection of the positive input terminal and the negative input terminal may be selected according to an actual circuit configuration, and necessary circuit elements (such as resistors) may be further provided between the positive input terminal and the negative input terminal and the first input terminal and the second input terminal, which is not limited by the disclosure.
The self-locking circuit 3 has a third input terminal electrically connected to the second output terminal and a third output terminal electrically connected to the first input terminal and the second input terminal.
The first comparison circuit 1 has a first threshold value U TH1 And a second threshold value U less than the first threshold value TH2 When the input voltage is greater than or equal to the first threshold value U TH1 When the first output end outputs the first level turnover signal, the execution circuit 4 receives the first level turnover signal so as to close the power device in the execution circuit 4. When the input voltage is less than or equal to the second threshold value U TH2 When the first output end outputs the second level turnover signal, the execution circuit 4 receives the second level turnover signal, so as to turn on the power device in the execution circuit 4.
Alternatively, the power devices may form a bridge inverter circuit, and the switching states of the upper and lower bridges are determined by the voltage signals applied to the control electrodes. Therefore, the execution circuit 4 can be connected to the control electrodes of the upper bridge and the lower bridge of the bridge type inverter circuit to control the on and off of the power devices. For example, a low input turns off the power device and a high input turns on the power device.
The protection circuit can control the input voltage at the first threshold U through the first comparison circuit 1 and the execution circuit 4 TH1 And a second threshold value U TH2 Accordingly, the current of the load is correspondingly limited within an interval, and the current limiting function is realized.
In addition, the second comparison circuit 2 has the first threshold U or more TH1 Third threshold value U of TH3 When the input voltage is greater than the third threshold value U TH3 When the circuit is in use, the second output end outputs a third level turnover signal, and the self-locking circuit 3 receives the third level turnover signal and latches the voltages of the first input end and the second input end to a preset voltage U 0 The predetermined voltage U 0 Greater than a third threshold value U TH3 Thereby causing the first comparison circuit 1 to output a first level-flip signal to turn off the power device in the execution circuit 4.
Alternatively, the predetermined voltage U 0 May be supplied by a power supply VCC, for example, a 5V dc voltage. The disclosure is not limited thereto, the predetermined voltage U 0 The voltage can be selected according to the practical application.
In addition, the self-locking circuit 3 may be configured to receive an external unlocking signal to release the latch state, in which the voltages of the first input terminal and the second input terminal are restored to the input voltage.
Through the second comparison circuit 2 in the protection circuit, the protection circuit can realize self-locking protection when the load is in overcurrent, so that damage to a power device in the circuit due to overcurrent faults is prevented, and the self-locking circuit can be unlocked by receiving an external unlocking signal. In summary, the protection circuit provided in at least one embodiment of the present disclosure can simultaneously achieve the current limiting protection function and the over-current protection function, and the protection circuit adopts pure hardware feedback control, so that the response speed is fast, and the protection circuit has cost benefits.
As shown in fig. 2, on the basis of the first embodiment, the protection circuit of the second embodiment provided by the present disclosure may further include a sampling circuit 6, and the sampling circuit 6 is configured to sample a voltage of a load. The output of the sampling circuit 6 may be connected as an output voltage to the inputs of the first and second comparison circuits 1, 2.
Further, in this embodiment, the protection circuit may further include an amplification circuit 7, the amplification circuit 7 being configured to amplify and output the voltage signal of the sampling circuit 6 as an input voltage, the amplification circuit 7 being connected between the output terminal of the sampling circuit 6 and the input terminals of the first comparison circuit 1 and the second comparison circuit 2.
Those skilled in the art can easily adopt the implementation of the sampling circuit and the amplifying circuit, which are common in the art, and the internal circuit configuration of the present disclosure is not specifically described here.
Fig. 3 is a block diagram of a protection circuit according to a third embodiment of the present invention. The third embodiment has the functions and effects of the foregoing embodiments, and only the differences from the first embodiment will be described below.
As shown in fig. 3, the protection circuit may further include a controller 5 including a first control port 51 and a second control port 52. The first control port 51 is an unlock signal source that issues an unlock signal.
Illustratively, the controller 5 may further include a second control port 52 electrically connected to the second output terminal, and configured to receive a third level-reversal signal to trigger the controller 5 to start counting once and start timing at the same time, and after timing for a preset time, the first control port 51 of the controller 5 issues an unlocking signal to release the latched state.
At this time, if the overcurrent fault has been relieved, the input voltage is equal to or less than the third threshold value U TH3 And the system resumes normal operation. Therefore, the controller 5 is adopted as an unlocking signal source, and the protection circuit can distinguish whether the overcurrent state really occurs or not, so that the protection circuit has robustness. The unreal overcurrent generated under some conduction or some electromagnetic interference and other conditions can be beneficialThe controller 5 is used for fault recovery of the overcurrent frequency judgment, and the system can work normally again. When the circuit is in fault and causes overcurrent, the controller 5 can be used for judging the overcurrent times to carry out fault judgment, and if the fault exists and is not eliminated all the time, the fault of the circuit is indicated in time to protect the power device.
The Controller 5 may be a Micro Controller Unit (MCU), a single chip, a Field Programmable Gate Array (FPGA), a digital signal processor, or other Controller with data receiving and processing capabilities. In the embodiment shown herein, the controller employs an MCU. For example, the second control port 52 may be connected to a brake pin, also called a brake emergency pin (BKIN), of the MCU, so as to trigger the brake pin to count and time according to the third level-flipping signal.
Further, when the input voltage is still greater than the third threshold, at which time the overcurrent fault still exists, the self-locking circuit is triggered again, and the brake pin of the controller 5 triggers the count again, and the count is increased by one, and when the count of the controller is greater than the preset count, the controller 5 stops outputting the unlock signal and indicates that the circuit has a fault.
Specifically, the MCU sets a certain overcurrent fault number (preset count), and after attempting fault recovery for multiple times, the count of the MCU is greater than the preset count, which indicates that the fault state still exists and is not resolved. At this time, the MCU stops outputting the unlock signal and performs an overcurrent fault indication through the indication circuit.
Fig. 4 is a block diagram of a protection circuit according to a fourth embodiment of the present invention. Similar to the second embodiment shown in fig. 2, the fourth embodiment shown in fig. 4 adds peripheral circuits, such as the sampling circuit 6 and the amplifying circuit 7, to the third embodiment, and the configuration thereof is not described again.
The protection circuit of the fourth embodiment shown in fig. 4 includes a first comparison circuit 1, a second comparison circuit 2, a self-locking circuit 3, an execution circuit 4, a controller 5, a sampling circuit 6, and an amplification circuit 7. The description of the above circuit can be obtained by a combination of the foregoing embodiments, and is not repeated herein.
According to the technical scheme of the present disclosure with the above features, the circuit is simplified to the maximum extent under the condition of simultaneously satisfying two functions of current limiting protection and overcurrent protection, so that not only is the complexity of the circuit reduced, but also the design cost is optimized. The scheme detects that the power device executes the closing action from the current, and the closing action is completely executed by a hardware circuit, so that the time delay caused by using a software processing scheme is avoided. By selecting the response speed of the device, the execution time of the hardware can be controlled within 5 microseconds, and the overcurrent endurance time of the power device is enough.
Fig. 5 is a schematic structural diagram of at least one embodiment of a protection circuit according to the present invention, which shows an exemplary implementation for implementing the functions of the foregoing embodiments. It should be noted that fig. 5 illustrates one possible implementation of the protection circuit by way of example and not limitation, and is not intended to limit the scope of the present disclosure.
Exemplarily, the first comparison circuit 1 may include a first comparison voltage U R1 Comparator U2, resistance R4, resistance R5 and resistance R6.
First comparison voltage U R1 Is electrically connected with the positive input end of the comparator U2, one end of the resistor R4 is electrically connected with the input voltage, the other end of the resistor R4 is electrically connected with the negative input end of the comparator U2, one end of the resistor R5 is electrically connected with the positive input end of the comparator U2, the other end of the resistor R5 is electrically connected with the output end of the comparator U2 and one end of the resistor R6, and the other end of the resistor R6 is electrically connected with the direct-current voltage U6 C And (6) electrically connecting.
The first comparison circuit 1 thus constitutes a typical hysteretic comparison circuit, characterized in that when the input voltage is gradually increased or gradually decreased, there are two unequal thresholds, the transfer characteristic of which has the shape of a "hysteretic" curve. As shown in fig. 5, the first comparison circuit 1 constitutes a forward input hysteresis comparison circuit. Optionally, the first comparison voltage U may also be used R1 The input is from the inverting input terminal of the comparator to form an inverting input hysteresis comparison circuit.
Thus, the first threshold value U TH1 And a second threshold value U TH2 The value of (A) can be calculated according to the calculation principle of the hysteresis comparison circuitIt is determined that the present disclosure is not specifically developed. Wherein the first threshold value U TH1 Greater than a second threshold value U TH2 。
Therefore, according to this example, the first comparison circuit 1 can realize the current limiting protection function of the foregoing embodiment, that is, when the input voltage is equal to or greater than the first threshold value U TH1 Meanwhile, the output terminal of the comparator U2 outputs a first level-flipping signal, and the execution circuit 4 receives the first level-flipping signal to turn off the power device in the execution circuit 4.
When the input voltage is less than or equal to the second threshold value U TH2 Meanwhile, the output end of the comparator U2 outputs a second level-flipping signal, and the execution circuit 4 receives the second level-flipping signal to turn on the power device in the execution circuit 4.
By selecting a suitable first comparison voltage U R1 DC voltage U C The values of resistor R5 and resistor R6 may determine a suitable first threshold U TH1 And a second threshold value U TH2 In this regard, the numerical values in the present disclosure are not particularly limited, and those skilled in the art can select suitable parameters according to actual needs.
In this embodiment, the first level-shift signal is shifted from a high level to a low level, and the second level-shift signal is shifted from a low level to a high level. When other comparator logic is used, the first level-flip signal and the second level-flip signal may also be corresponding flip signal logic.
Exemplarily, the second comparison circuit 2 may include a second comparison voltage U R2 Comparator U1, resistance R1, resistance R2 and resistance R3.
Second comparison voltage U R2 Is electrically connected with the positive input end of the comparator U1, one end of the resistor R1 is electrically connected with the input voltage, the other end of the resistor R1 is electrically connected with the negative input end of the comparator U1, one end of the resistor R2 is electrically connected with the positive input end of the comparator U1, the other end of the resistor R2 is electrically connected with the output end of the comparator U1 and one end of the resistor R3, and the other end of the resistor R3 is electrically connected with the direct-current voltage U3 C And (6) electrically connecting.
Similarly, the third threshold U TH3 Or by the calculation of hysteresis comparison circuitAnd (4) determining.
In this embodiment, the third level-reversal signal is reversed from high level to low level.
For implementing the over-current protection function, the third threshold value U is set TH3 Is set to be greater than a first threshold value U TH1 From the above formula, by selecting the appropriate second comparison voltage U R2 DC voltage U C The values of the resistor R2 and the resistor R3, a third threshold U may be determined TH3 . In one example, the DC voltage U C Is 5V.
Therefore, according to this example, the second comparison circuit 2 can realize the overcurrent protection function of the foregoing embodiment, i.e., when the input voltage is greater than the third threshold value U TH3 When the voltage of the first input end and the second input end is higher than the preset voltage U, the output end of the comparator U1 outputs a third level turnover signal, the self-locking circuit 3 receives the third level turnover signal and latches the voltages of the first input end and the second input end to the preset voltage U 0 The predetermined voltage U 0 Greater than a third threshold value U TH3 Thereby enabling the first comparison circuit 1 to output a first level-reversal signal to turn off the power device in the execution circuit. At this time, if an unlocking signal sent by the outside is not received, the self-locking circuit 3 keeps the latching state all the time, and the power device keeps the closing state.
When receiving an external unlocking signal, the self-locking circuit 3 releases the latching state, and the voltages of the first input end and the second input end are restored to the input voltage.
Alternatively, the comparators U1 and U2 may also employ operational amplifiers.
Fig. 5 shows a possible embodiment of the self-locking circuit 3. As shown in fig. 5, the self-latch circuit 3 may include a transistor Q1 and a transistor Q2.
The base of the transistor Q1 is electrically connected with the output terminal of the comparator U1, and the emitter of the transistor Q1 is connected with the predetermined voltage U 0 And the collector of the triode Q1 is electrically connected with the emitter of the triode Q2, the base of the triode Q2 is electrically connected with an external unlocking signal source, and the collector of the triode Q2 is electrically connected with the first input end and the second input end.
Illustratively, transistors Q1 andthe transistor Q2 is a PNP transistor. Under normal condition, the input voltage is less than the third threshold value U TH3 The output of the comparator U1 is high, and the transistor Q1 is off. And the transistor Q2 is turned on by default, i.e., the signal source is unlocked to output a low level. For embodiments where controller 5 is present, first control port 51 of controller 5 may be connected to the base of transistor Q2 as a source of unlock signal.
When the current in the load rises, its corresponding input voltage also rises until the third threshold U is exceeded TH3 . At this time, the output of the comparator U1 is inverted from high to low, thereby turning on the transistor Q1 to predetermine the voltage U 0 Directly to the input voltage terminal, thereby shielding the input voltage. Due to the predetermined voltage U 0 Greater than a third threshold value U TH3 And therefore also necessarily greater than the first threshold U TH1 And thus can also trigger the first toggle signal at the output terminal of the comparator U2, i.e. the output terminal of the comparator U2 toggles from high level to low level, thereby turning off the power device in the execution circuit 4. Before the unlocking signal is not received, the input voltage end always keeps the preset voltage U 0 The comparators U1 and U2 maintain the latched state, and the power devices in the execution circuit 4 maintain the off state.
When the unlocking is needed, an unlocking signal, such as a high-level single pulse, is sent to the self-locking circuit 3, the self-locking circuit 3 sends the pulse signal, the triode Q2 is disconnected, and the voltages of the first input end and the second input end are restored to the input voltage.
Optionally, the transistor Q1 and the transistor Q2 may be either NPN transistors or PNP transistors, and those skilled in the art can modify the connection of the circuits accordingly to implement the self-locking logic of the present disclosure.
Alternatively, for embodiments in which the controller 5 is present, the first control port 51 is the source of the unlock signal that issues the unlock signal. The second control port 52 receives the third level-reversal signal to trigger the controller 5 to start counting once and start timing at the same time, and after the timing reaches a preset time, the first control port 51 of the controller sends an unlocking signal to release the latch state, and the voltages of the first input end and the second input end are restored to the input voltage.
At this time, if the overcurrent fault is removed and the load current is restored to normal, the input voltage is lowered to be less than the first threshold value U TH1 At this point the circuit resumes normal operation.
Conversely, if the overcurrent fault has not been eliminated, i.e. the input voltage is still greater than the third threshold value U TH3 The latch circuit 3 is triggered again and the brake pin of the controller 5 triggers the count again and the count is incremented by one. The above steps are repeated in a circulating mode until the count of the controller is larger than the preset count, at this time, because the overcurrent fault is still not eliminated due to multiple times of unlocking, the controller 5 can think that the overcurrent fault is not eliminated all the time, and therefore the controller 5 stops outputting the unlocking signal and indicates that the circuit has a fault, and the function of protecting the power device in the circuit is achieved.
Alternatively, since the logic of the third level-shifted signal is the same as the logic of the first level-shifted signal, the second control port 52 can also be electrically connected to the output terminal of the comparator U2, and the effect of triggering the brake pin timing and counting can also be substantially achieved.
Fig. 6 shows a graph of a load voltage and a comparator output signal of a protection circuit according to at least one embodiment of the invention. Fig. 7 illustrates a graph of a load waveform and a comparator output signal of a protection circuit in accordance with at least one embodiment of the present invention. Fig. 8 shows a graph of a load waveform and a comparator output signal of a protection circuit according to a further embodiment of the present invention. Fig. 6, 7 and 8 schematically show the operating state diagram of the protection circuit.
As shown in fig. 6, under the current-limiting protection function, the waveform of the input voltage is limited to the first threshold U TH1 And a second threshold value U TH2 To fluctuate.
When the input voltage reaches the first threshold U TH1 At this time, the comparator U2 outputs a first level-flip signal (from high level to low level) to turn off the power devices in the execution circuit 4, causing the load current to drop, thereby causing the input voltage to drop.
When the input voltage drops to reach a second threshold U TH2 Comparator U2 outputThe second level-flip signal (flip from low to high) turns on the power devices in the execution circuit 4, causing the load current to rise, thereby causing the input voltage to rise.
By repeating the above steps, the input voltage waveform (corresponding to the load current) can be limited to the first threshold value U TH1 And a second threshold value U TH2 The current is limited and protected.
Fig. 7 shows an operating state diagram without the controller 5. When the waveform of the input voltage reaches or even exceeds the third threshold U TH3 When the latch circuit 3 latches and latches, the comparator U1 outputs a third level flip signal (flip from high to low) to turn off the power device in the execution circuit 4, and the comparator U2 outputs a first level flip signal (flip from high to low) to turn off the power device in the execution circuit 4. The specific process can be referred to the description of the embodiment of fig. 5. An overcurrent protection function can be realized.
Fig. 8 shows an operating state diagram in the presence of the controller 5. When the waveform of the input voltage reaches or even exceeds the third threshold U TH3 In this case, similarly to fig. 7, the comparator U1 outputs a third level flip signal (flip from high level to low level) so that the latch circuit 3 performs latch and latching, and the comparator U2 outputs a first level flip signal (flip from high level to low level) to turn off the power device in the execution circuit 4.
The second control port 52 receives the third level-reversal signal to trigger the controller 5 to start counting once and start timing at the same time, and after the timing reaches the preset self-locking time, the first control port 51 of the controller sends out an unlocking signal to release the latching state, and the voltages of the first input end and the second input end are restored to the input voltage. The self-locking time may be set by the controller 5, e.g. the MCU.
If the over-current fault has not been eliminated, i.e. the input voltage is still greater than the third threshold value U TH3 The latch circuit 3 is triggered again and the brake pin of the controller 5 triggers the count again and the count is incremented by one. The time from the start of unlocking to the re-locking can be denoted as the unlocking time.
Fig. 8 only shows the second triggering after the self-locking time, and those skilled in the art will understand that multiple triggering may be implemented as long as the preset count is greater than two times.
At least one embodiment of the present disclosure also provides a circuit protection device, which may include the protection circuit as described above. Examples of the circuit protection device may be a printed circuit board, a flexible circuit board, or other circuit devices commonly known in the art.
At least one embodiment of the present disclosure also provides a motor control system including the circuit protection device as described above. A typical motor may employ the motor control system to simultaneously implement a current limiting protection function and an over-current protection function.
In conclusion, the protection circuit provided by the invention integrates the current limiting protection function and the overcurrent protection function, the latch of the overcurrent state is realized through the self-locking circuit, the circuit is simplified to the maximum extent under the condition of simultaneously meeting the two functions, the complexity of the circuit is reduced, and the design cost is optimized. In addition, the power device performs the shutdown action from the current detection is performed entirely by hardware circuitry, thereby avoiding the time delay associated with using a software processing scheme. Tests show that the execution time of hardware can be controlled within 5 microseconds by selecting the response speed of the device, the response speed is high, and the overcurrent bearing time of the power device is sufficiently met. The circuit protection device and the motor provided by the invention have the same advantages and benefits due to the protection circuit.
The protective circuit proposed by the invention, the protective device with the protective circuit and the motor have been described in detail with reference to the preferred embodiments, however, it will be understood by those skilled in the art that many variations and modifications can be made to the specific embodiments described above, and many combinations of the various technical features and structures proposed by the invention can be made without departing from the inventive concept, and the scope of the invention is determined by the appended claims.

Claims (11)

1. A protection circuit that performs a circuit protection operation based on an input voltage, the protection circuit comprising:
the first comparison circuit is provided with a first input end and a first output end, the first input end is electrically connected with the input voltage, and the first output end is electrically connected with the execution circuit;
a second comparator circuit having a second input terminal and a second output terminal, the second input terminal being electrically connected to the input voltage; and
a self-locking circuit having a third input terminal and a third output terminal, the third input terminal being electrically connected to the second output terminal, the third output terminal being electrically connected to the first input terminal and the second input terminal,
when the input voltage is greater than or equal to the first threshold, the first output end outputs a first level turnover signal, and the execution circuit receives the first level turnover signal so as to close a power device in the execution circuit;
when the input voltage is less than or equal to a second threshold value, the first output end outputs a second level turnover signal, and the execution circuit receives the second level turnover signal so as to start a power device in the execution circuit;
wherein the second comparing circuit has a third threshold larger than the first threshold, when the input voltage is larger than the third threshold, the second output terminal outputs a third level flip signal, the self-locking circuit receives the third level flip signal and latches the voltages of the first input terminal and the second input terminal to a predetermined voltage, the predetermined voltage is larger than the third threshold, so that the first comparing circuit outputs the first level flip signal to turn off the power device in the executing circuit,
wherein the self-locking circuit is configured to receive an external unlocking signal to release the latch state, and the voltages of the first input terminal and the second input terminal are restored to the input voltage,
the protection circuit further includes:
a controller including a first control port, the first control port being an unlock signal source that emits the unlock signal,
when the input voltage is still larger than the third threshold value, the self-locking circuit is triggered again, the brake pin of the controller triggers counting again, the counting is increased by one, and when the counting of the controller is larger than the preset counting, the controller stops outputting the unlocking signal and indicates that the circuit breaks down.
2. The protection circuit of claim 1, wherein the first comparison circuit comprises: first comparison voltage U R1 A comparator U2, a resistor R4, a resistor R5 and a resistor R6, a first comparison voltage U R1 Is electrically connected with the positive input end of the comparator U2, one end of the resistor R4 is electrically connected with the input voltage, the other end of the resistor R4 is electrically connected with the negative input end of the comparator U2, one end of the resistor R5 is electrically connected with the positive input end of the comparator U2, the other end of the resistor R5 is electrically connected with the output end of the comparator U2 and one end of the resistor R6, and the other end of the resistor R6 is electrically connected with the direct-current voltage U6 C And (6) electrically connecting.
3. The protection circuit of claim 1, wherein the second comparison circuit comprises:
second comparison voltage U R2 A comparator U1, a resistor R1, a resistor R2 and a resistor R3, a second comparison voltage U R2 Is electrically connected with the positive input end of the comparator U1, one end of the resistor R1 is electrically connected with the input voltage, the other end of the resistor R1 is electrically connected with the negative input end of the comparator U1, one end of the resistor R2 is electrically connected with the positive input end of the comparator U1, the other end of the resistor R2 is electrically connected with the output end of the comparator U1 and one end of the resistor R3, and the other end of the resistor R3 is electrically connected with the direct-current voltage U3 C And (6) electrically connecting.
4. The protection circuit of claim 3, wherein the self-locking circuit comprises:
a transistor Q1 and a transistor Q2, wherein the base of the transistor Q1 is electrically connected with the output end of the comparator U1, and the emitter of the transistor Q1 is connected with the predetermined voltage U 0 The collector of the transistor Q1 is electrically connected with the emitter of the transistor Q2, and the base of the transistor Q2 is connected with the outsideThe unlocking signal source is electrically connected, and the collector of the triode Q2 is electrically connected with the first input end and the second input end.
5. The protection circuit of claim 4, wherein the transistor Q1 and the transistor Q2 are PNP transistors.
6. The protection circuit of claim 1, wherein the controller further comprises a second control port electrically connected to the second output terminal, and configured to receive the third level-reversal signal to trigger the controller to start counting once and start timing at the same time, and after the timing reaches a preset time, the first control port of the controller sends out an unlocking signal to release the latched state.
7. The protection circuit according to any one of claims 1 to 6, wherein the first level-flip signal is flipped from a high level to a low level, the second level-flip signal is flipped from a low level to a high level, and the third level-flip signal is flipped from a high level to a low level.
8. The protection circuit of claim 1, further comprising: and the sampling circuit is configured to sample the voltage of the load, and the output end of the sampling circuit is connected to the input ends of the first comparison circuit and the second comparison circuit.
9. The protection circuit of claim 8, further comprising: and the amplifying circuit is configured to amplify and output the voltage signal of the sampling circuit as an input voltage, and is connected between the output end of the sampling circuit and the input ends of the first comparison circuit and the second comparison circuit.
10. A circuit protection device comprising: the protection circuit of any one of claims 1-9.
11. A motor control system comprising: the circuit protection device of claim 10.
CN202011039157.7A 2020-09-28 2020-09-28 Protection circuit, circuit protection device and motor control system Active CN112134269B (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104600682A (en) * 2015-02-05 2015-05-06 湖北工业大学 Active power filter current protection circuit and method
CN109524941A (en) * 2018-12-29 2019-03-26 北京汇能精电科技股份有限公司 Phase current foldback circuit and photovoltaic controller
CN110474622A (en) * 2019-08-22 2019-11-19 海信（山东）空调有限公司 A kind of self-locking protective circuit and air conditioner
CN216355945U (en) * 2021-10-27 2022-04-19 深圳市京泉华智能电气有限公司 Dual overvoltage protection circuit

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104600682A (en) * 2015-02-05 2015-05-06 湖北工业大学 Active power filter current protection circuit and method
CN109524941A (en) * 2018-12-29 2019-03-26 北京汇能精电科技股份有限公司 Phase current foldback circuit and photovoltaic controller
CN110474622A (en) * 2019-08-22 2019-11-19 海信（山东）空调有限公司 A kind of self-locking protective circuit and air conditioner
CN216355945U (en) * 2021-10-27 2022-04-19 深圳市京泉华智能电气有限公司 Dual overvoltage protection circuit

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