Over-voltage and under-voltage protection circuit

Abstract

The utility model discloses an overvoltage and undervoltage protection circuit, and belongs to the technical field of protection circuits in analog circuits. In order to solve the technical problems that when the voltage of a power grid fluctuates frequently, a voltage division signal also controls the frequent switching of a field effect transistor, so that a circuit also enters frequent overvoltage and undervoltage protection, the circuit cannot work normally, and a motor is easy to damage. According to the technical scheme, a protection main circuit is powered by an ACDC power supply circuit and comprises an AND gate circuit, a relay circuit, a sampling circuit and a time delay circuit, the sampling circuit collects bus voltage and outputs a first signal, the time delay circuit receives the first signal and converts the first signal into a second signal in a delayed mode, and the second signal is connected with the AND gate circuit. Two input ends of the AND gate circuit are respectively connected with the sampling circuit and the time-delay circuit to obtain a first signal and a second signal, an output end of the AND gate circuit is connected with the relay circuit and sends an execution signal to the relay circuit, and the relay circuit carries out open-circuit protection on a power supply line at a motor end according to the execution signal. The circuit breaker has the effect of overvoltage and undervoltage circuit breaker protection.

Description

Technical Field

[0001] This application relates to the technical field of power supply protection circuits, and in particular, to an overvoltage undervoltage protection circuit. Background Art

[0002] There are situations of unstable voltage fluctuations in industrial electricity. Frequent power grid voltage fluctuations require the controller to have a reasonable and stable overvoltage undervoltage protection function. Unreasonable overvoltage undervoltage protection control logic will affect the normal and stable operation of the motor, or reduce the service life of the motor.

[0003] The protection methods used in the past mainly involved the controller dividing the voltage signal, and using the signal generated after voltage division to control the on-off of the field effect transistor to control the on-off of the loop, achieving the function of overvoltage undervoltage protection. However, this overvoltage undervoltage protection method has many problems. For example, when the power grid voltage fluctuates frequently, the divided voltage signal will also control the frequent on-off of the field effect transistor, which will cause the circuit to enter frequent overvoltage undervoltage protection. It cannot work properly and is prone to damaging the motor.

[0004] In the past, there were also cases where the controller transmitted the voltage signal to the single-chip microcomputer after voltage division, and the single-chip microcomputer output a control signal through an algorithm to control the on-off of the field effect transistor to control the on-off of the loop. However, this method still has problems. The single-chip microcomputer will freeze in a harsh working environment. When the single-chip microcomputer freezes, the controller no longer has the overvoltage undervoltage protection function. Summary of the Utility Model

[0005] In view of the above-mentioned disadvantages (problems) of the prior art, in order to be able to implement overvoltage undervoltage protection using a pure hardware circuit structure and avoid the single-chip microcomputer from freezing and being unable to work, this application provides an overvoltage undervoltage protection circuit.

[0006] To achieve the above object and other related objects, this application adopts the following technical solutions:

[0007] An overvoltage undervoltage protection circuit includes a power-taking end, a motor end, and an ACDC power supply circuit. The power-taking end has a live wire and a neutral wire. The power-taking end is connected to the ACDC power supply circuit. The ACDC power supply circuit outputs a bus voltage and a working voltage respectively. The power-taking end and the motor end are connected through a main protection circuit.

[0008] The main protection circuit is powered by the ACDC power supply circuit. The main protection circuit includes an AND gate circuit, a relay circuit, a sampling circuit, and a delay circuit.

[0009] The sampling circuit samples the bus voltage and outputs a first signal. The delay circuit receives the first signal and delays it to convert it into a second signal. Two input terminals of the "AND" gate circuit are respectively connected to the sampling circuit and the delay circuit to obtain the first signal and the second signal. The output terminal of the "AND" gate circuit is connected to the relay circuit and sends an execution signal to the relay circuit. The relay circuit performs open-circuit protection on the power supply line of the motor terminal according to the execution signal.

[0010] Preferably, the sampling circuit includes an overvoltage sampling circuit. The overvoltage sampling circuit includes a resistor R1, a resistor R2, a triode Q2, a resistor R3, and a resistor R4. One end of the resistor R1 is connected to the bus voltage, and the other end of the resistor R1 is connected to the base of the triode Q2 and one end of the resistor R2. The other end of the resistor R2 and the emitter of the triode Q2 are grounded. The working voltage is connected to one end of the resistor R4, the other end of the resistor R4 is connected to the resistor R3, and the other end of the resistor R3 is connected to the collector of the triode Q2 and outputs the first signal.

[0011] Preferably, the sampling circuit includes an undervoltage sampling circuit. The undervoltage sampling circuit includes a resistor R11, a resistor R12, a resistor R13, a triode Q5, and an inverter U3. One end of the resistor R12 is connected to the bus voltage, and the other end of the resistor R12 is connected to one end of the resistor R13 and the base of the triode Q5. The emitter of the triode Q5 and the other end of the resistor R13 are grounded. The working voltage is connected to one end of the resistor R11, and the other end of the resistor R11 is connected to the collector of the triode Q5 and the input terminal of the inverter U3. The output terminal of the inverter U3 is used to output the first signal.

[0012] Preferably, the delay circuit includes a resistor R5, a resistor R6, a resistor R7, a resistor R8, a triode Q1, a capacitor C1, a voltage regulator U1, and a triode Q3. The emitter of the triode Q1 is connected to the working voltage, the base of the triode Q1 is connected to the node between the resistor R3 and the resistor R4, and the collector of the triode Q1 is connected to one end of the resistor R5. The other end of the resistor R5 is connected to one end of the resistor R6, one end of the capacitor C1, and the first pin of the voltage regulator U1. The third pin of the voltage regulator U1 is connected to one end of the resistor R7 and the base of the triode Q3. The other end of the resistor R7 and one end of the resistor R8 are connected to the working voltage. The other end of the resistor R8 and the emitter of the triode Q3 are connected and output the second signal. The collector of the triode Q3, the second pin of the voltage regulator, the other end of the resistor R6, and the other end of the capacitor C1 are grounded.

[0013] Preferably, the relay circuit includes a coil K1, a normally open switch K1-1, a triode Q4, a resistor R9, and a resistor R10. One end of the operating voltage is connected to one end of the coil K1, the other end of the coil is connected to the collector of the triode Q4, the emitter of the triode Q4 and one end of the resistor R10 are grounded, the base of the triode Q4 and the other end of the resistor R10 and one end of the resistor R9 are connected, the other end of the resistor R9 is used to receive an execution signal, and the normally open switch K1-1 is connected in series on the live wire.

[0014] In summary, the present application includes at least one of the following beneficial technical effects:

[0015] A first signal sampled from the DC voltage rectified from the grid voltage, and the first signal can obtain a delayed second signal through a delay circuit. The first signal and the second signal are used as the inputs of an "AND" gate circuit, and the output signal of the "AND" gate circuit controls the opening and closing of the relay to achieve the purpose of overvoltage and undervoltage delay protection, which can avoid frequent starting and stopping of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the main circuit diagram of Embodiment 1 of the present application;

[0017] Figure 2 is the circuit diagram of the control part of Embodiment 1 of the present application;

[0018] Figure 3 is the circuit schematic diagram of Embodiment 2 of the present application.

[0019] Main reference numeral descriptions:

[0020] 100, power-taking end; 200, motor end; 300, ACDC power supply circuit; 400, "AND" gate circuit; 500, relay circuit; 600, overvoltage sampling circuit; 700, undervoltage sampling circuit; 800, delay circuit. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The following specific examples illustrate the implementation manners of the present application. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0022] It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present application in a schematic manner. The diagrams only show the components related to the present application and are not drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in actual implementation can be changed arbitrarily, and the component layout type may also be more complex.

[0023] The following further describes the specific implementation manner of the present application with reference to the accompanying drawings.

[0024] Embodiment 1 (Optimal Example):

[0025] An overvoltage and undervoltage protection circuit is disclosed in an embodiment of the present application. Referring to Figure 1 and Figure 2 as shown, it includes a power-taking end 100, a motor end 200, and an ACDC power circuit 300. The power-taking end 100 has a live wire (L) and a neutral wire (N). The power-taking end 100 is connected to the ACDC power circuit 300. The ACDC power circuit 300 outputs a bus voltage (VBUS) and a working voltage (VCC) respectively. The power-taking end 100 and the motor end 200 are connected through a protection main circuit. The motor end 200 includes a motor live wire and a motor neutral wire, which are used to supply power to the motor here.

[0026] The protection main circuit is powered by the ACDC power circuit 300. The protection main circuit includes an AND gate circuit 400, a relay circuit 500, a sampling circuit, and a delay circuit 800. The ACDC power circuit 300 is used to convert alternating current into direct current.

[0027] The sampling circuit samples the bus voltage and outputs a first signal (VA). The delay circuit 800 receives the first signal and performs a delay conversion to obtain a second signal (VB). Two input ends of the AND gate circuit 400 are respectively connected to the sampling circuit and the delay circuit 800 to obtain the first signal and the second signal. The output end of the AND gate circuit 400 is connected to the relay circuit 500 and sends an execution signal (S1) to the relay circuit 500. The relay circuit 500 performs open-circuit protection on the power supply line of the motor end 200 according to the execution signal.

[0028] In Figure 1 it can be seen that preferably, the relay circuit 500 includes a coil K1, a normally open switch K1-1, a triode Q4 (P-type), a resistor R9, and a resistor R10. The working voltage is connected to one end of the coil K1. The other end of the coil is connected to the collector of the triode Q4. The emitter of the triode Q4 and one end of the resistor R10 are grounded. The base of the triode Q4, the other end of the resistor R10, and one end of the resistor R9 are connected. The other end of the resistor R9 is used to receive the execution signal. The normally open switch K1-1 is connected in series on the live wire. When the execution signal S1 is at a high level, the relay normally open switch K1-1 closes, otherwise it is in an open state.

[0029] In Figure 2 it, the sampling circuit includes an overvoltage sampling circuit 600. The overvoltage sampling circuit 600 includes a resistor R1, a resistor R2, a triode Q2, a resistor R3, and a resistor R4. One end of the resistor R1 is connected to the bus voltage, the other end of the resistor R1 is connected to the base of the triode Q2 and one end of the resistor R2. The other end of the resistor R2 and the emitter of the triode Q2 are grounded. The working voltage is connected to one end of the resistor R4. The other end of the resistor R4 is connected to the resistor R3. The other end of the resistor R3 is connected to the collector of the triode Q2 and outputs a first signal.

[0030] In addition, the sampling circuit includes an undervoltage sampling circuit 700. The undervoltage sampling circuit 700 includes a resistor R11, a resistor R12, a resistor R13, a triode Q5, and an inverter U3. One end of the resistor R12 is connected to the bus voltage. The other end of the resistor R12 is connected to one end of the resistor R13 and the base of the triode Q5. The emitter of the triode Q5 and the other end of the resistor R13 are grounded. The working voltage is connected to one end of the resistor R11. The other end of the resistor R11 is connected to the collector of the triode Q5 and the input end of the inverter U3. The output end of the inverter U3 is used to output a first signal.

[0031] The delay circuit 800 includes a resistor R5, a resistor R6, a resistor R7, a resistor R8, a triode Q1, a capacitor C1, a voltage regulator U1, and a triode Q3. The emitter of the triode Q1 is connected to the working voltage. The base of the triode Q1 is connected to the node between the resistor R3 and the resistor R4. The collector of the triode Q1 is connected to one end of the resistor R5. The other end of the resistor R5 is connected to one end of the resistor R6, one end of the capacitor C1, and the first pin of the voltage regulator U1. The third pin of the voltage regulator U1 is connected to one end of the resistor R7 and the base of the triode Q3. The other end of the resistor R7 and one end of the resistor R8 are connected to the working voltage. The other end of the resistor R8 and the emitter of the triode Q3 are connected and output a second signal. The collector of the triode Q3, the second pin of the voltage regulator, the other end of the resistor R6, and the other end of the capacitor C1 are grounded.

[0032] The voltage regulator U1 is a 431 controllable precision voltage regulator. The capacitor C1 is an electrolytic capacitor.

[0033] The working principle is as follows:

[0034] After power-on, the working voltage VCC makes the first signal VA high level through the resistor R4 and the resistor R3. The working voltage VCC makes the second signal VB high level through the resistor R8.

[0035] At the same time, the bus voltage VBUS is divided by the resistors R12 and R13 to obtain a signal to drive the triode Q5 to conduct, making its collector VD low level. VD is connected to keep the first signal VA high level after passing through the inverter U3.

[0036] That is, the initial states of the first signal VA and the second signal VB are high levels after power-on. The "AND" gate circuit 400 outputs a high level to drive the triode Q4 to conduct, and the relay is energized and conducts, ensuring that the motor is energized and operates.

[0037] Situation 1: When the grid voltage is too high, the signal after voltage division of VBUS by resistors R1 and R2 drives the triode Q2 to conduct, the first signal VA becomes a low level, the "AND" gate circuit 400 outputs a low level, controls the triode Q4 to turn off, the relay K1 disconnects, and the motor stops operating. Record the time when the first signal VA is continuously at a low level as T1.

[0038] Meanwhile, because the first signal VA is at a low level, the triode Q1 conducts, VCC charges the capacitor C1 through the resistor R5. When the voltage VR on the capacitor C1 is higher than the reference voltage of the adjustable precision voltage regulator U1, the second pin and the third pin of U1 conduct, causing the triode Q3 to conduct, the second signal VB becomes a low level, U2 keeps outputting a low level, the triode Q4 keeps turning off, and the normally open switch of the relay keeps disconnecting.

[0039] After the grid voltage returns to normal, the voltage of VBUS drops, Q2 turns off, VA becomes a high level, Q1 turns off, the capacitor C1 discharges through R6. After a time T2, the voltage VR on C1 is lower than the reference voltage of the adjustable precision voltage regulator U1, the second pin and the third pin of U1 are not connected, Q3 disconnects, and the collector of Q3 outputs a high level.

[0040] That is, after a time T1 + T2, both VA and VB return to high levels. The "AND" gate circuit 400 (U2) outputs a high level, Q4 conducts, and the collector of Q4 is at a low level. The normally open switch of the relay closes, and the motor resumes operation. Thus, an overvoltage protection cycle ends. The motor is in overvoltage protection during the T1 + T2 time period and will not start and stop frequently.

[0041] Situation 2: When the grid voltage is too low, the signal after voltage division of VBUS by R12 and R13 cannot drive Q5, Q5 disconnects, VCC makes VD become a high level through R11. VD outputs VA as a low level through the inverter U3. Record the time when VA is continuously at a low level as T3.

[0042] Meanwhile, because VA is at a low level, the triode Q1 conducts, VCC charges C1 through R5. When the voltage VR on C1 is higher than the reference voltage of the adjustable precision voltage regulator U1, the second pin and the third pin of U1 conduct, causing Q3 to conduct, VB becomes a low level, U2 keeps outputting a low level, Q4 keeps turning off, and the normally open switch of the relay keeps disconnecting.

[0043] After the grid voltage returns to normal, the VBUS voltage rises, Q5 conducts, VD becomes low level, VA becomes high level, Q1 turns off, and the capacitor C1 discharges through R6. After a time T4, the voltage VR on C1 is lower than the reference voltage of the precision voltage regulator U1. The second and third pins of U1 are not connected, Q3 disconnects, and the VB output at the collector of Q3 is high.

[0044] After a time T3 + T4, both VA and VB return to high level. The AND gate U2 outputs high level, Q4 conducts, and the collector of Q4 is at low level. The normally open switch of the relay closes, and the motor resumes operation. Thus, an undervoltage protection cycle ends. The motor is under undervoltage protection during the T3 + T4 time period and will not start and stop frequently.

[0045] In summary, only when the grid voltage is normal, the signals VA and VB both output high level, U2 outputs high level, Q4 conducts, and K1 - 1 closes, can the motor operate stably. If the grid voltage fluctuates, is overvoltage or undervoltage, and one of the signals VA and VB is at low level, U2 outputs low level, Q4 disconnects, and K1 - 1 disconnects, and the motor will enter protection and stop working. This can extend the overvoltage and undervoltage protection time when the grid voltage fluctuates frequently, so that the motor will not start and stop frequently.

[0046] Embodiment 2:

[0047] Based on the above embodiment, the structure can be weakened. For example, as shown in Figure Figure 3 it can be seen that the undervoltage sampling circuit 700 can be removed, and thus it can be changed into an overvoltage protection circuit.

[0048] Similarly, an overvoltage protection circuit, an undervoltage protection circuit, and an overvoltage and undervoltage protection circuit can be implemented.

[0049] The above embodiments are only illustrative of the principles and effects of the present application and are not used to limit the present application. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent changes made according to the structure, shape, and principle of the present application should be covered within the protection scope of the present application.

Claims

1. An overvoltage and undervoltage protection circuit, comprising a power supply end (100), a motor end (200), and an ACDC power supply circuit (300), wherein the power supply end (100) has a live wire and a neutral wire, the power supply end (100) is connected to the ACDC power supply circuit (300), and the ACDC power supply circuit (300) outputs a bus voltage and an operating voltage respectively, characterized in that: The power supply end (100) and the motor end (200) are connected via a protective main circuit. The protection main circuit is powered by an ACDC power supply circuit (300), and comprises an AND gate circuit (400), a relay circuit (500), a sampling circuit, and a delay circuit (800). The sampling circuit collects the bus voltage and outputs a first signal; the delay circuit (800) receives the first signal and performs delay conversion into a second signal; two input ends of the AND gate circuit (400) are respectively connected to the sampling circuit and the delay circuit (800) to obtain the first signal and the second signal; the output end of the AND gate circuit (400) is connected to the relay circuit (500) and sends an execution signal to the relay circuit (500); the relay circuit (500) performs circuit breaker protection on the power supply line of the motor end (200) according to the execution signal.

2. The overvoltage and undervoltage protection circuit according to claim 1, characterized in that: The sampling circuit comprises an overvoltage sampling circuit (600), the overvoltage sampling circuit (600) comprising a resistor R1, a resistor R2, a transistor Q2, a resistor R3, and a resistor R4, one end of the resistor R1 is connected to a bus voltage, the other end of the resistor R1 is connected to a base of the transistor Q2 and one end of the resistor R2, the other end of the resistor R2 and the emitter of the transistor Q2 are grounded, the working voltage is connected to one end of the resistor R4, the other end of the resistor R4 is connected to the resistor R3, and the other end of the resistor R3 is connected to the collector of the transistor Q2 and outputs a first signal.

3. The overvoltage and undervoltage protection circuit according to claim 1, characterized in that: The sampling circuit comprises an undervoltage sampling circuit (700), the undervoltage sampling circuit (700) comprising a resistor R11, a resistor R12, a resistor R13, a transistor Q5 and an inverter U3, one end of the resistor R12 is connected to a bus voltage, the other end of the resistor R12 is connected to one end of the resistor R13 and the base of the transistor Q5, the emitter of the transistor Q5 and the other end of the resistor R13 are grounded, the working voltage is connected to one end of the resistor R11, the other end of the resistor R11 is connected to the collector of the transistor Q5 and the input end of the inverter U3, and the output end of the inverter U3 is used to output a first signal.

4. The overvoltage and undervoltage protection circuit according to claim 2, characterized in that: The delay circuit (800) comprises a resistor R5, a resistor R6, a resistor R7, a resistor R8, a transistor Q1, a capacitor C1, a voltage regulator U1, and a transistor Q3, wherein the emitter of the transistor Q1 is connected to the working voltage, the base of the transistor Q1 is connected to the node between the resistor R3 and the resistor R4, the collector of the transistor Q1 is connected to one end of the resistor R5, the other end of the resistor R5 is connected to the resistor R6, one end of the capacitor C1, and the first pin of the voltage regulator U1, the third pin of the voltage regulator U1 is connected to one end of the resistor R7 and the base of the transistor Q3, the other end of the resistor R7 and one end of the resistor R8 are connected to the working voltage, the other end of the resistor R8 is connected to the emitter of the transistor Q3 and outputs a second signal, and the collector of the transistor Q3, the second pin of the voltage regulator, the other end of the resistor R6, and the other end of the capacitor C1 are grounded.

5. The overvoltage and undervoltage protection circuit according to claim 1, characterized in that: The relay circuit (500) comprises a coil K1, a normally open switch K1-1, a transistor Q4, a resistor R9 and a resistor R10, wherein the working voltage is connected to one end of the coil K1, the other end of the coil is connected to the collector of the transistor Q4, the emitter of the transistor Q4 and one end of the resistor R10 are grounded, the base of the transistor Q4 and the other end of the resistor R10 and one end of the resistor R9 are connected, the other end of the resistor R9 is used to receive an execution signal, and the normally open switch K1-1 is connected in series to the live wire.

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