CN204992525U - Undervoltage protection circuit of delaying of switch electrical apparatus - Google Patents

Abstract

The time-delayed overvoltage and undervoltage protection circuit of the switching device includes a surge absorbing circuit, a half-wave rectification circuit, a detection circuit, a trigger isolation circuit and an execution circuit coupled in sequence. The overvoltage detection delay circuit is composed of DC output sampling and charging a capacitor. When the sampling result is greater than its overvoltage setting value, the circuit has an overvoltage delay process and can be coupled to the overvoltage delay process after the overvoltage delay process is over. The connected trigger isolation circuit outputs an overvoltage control signal. It also includes an undervoltage detection delay circuit. The emitter of its triode obtains the reference voltage from the DC output terminal. The base of the triode is sampled from the DC output terminal through two voltage dividing resistors. When the sampling result is less than the undervoltage set value , the triode is turned on, the undervoltage detection delay circuit has an undervoltage delay process and can output an undervoltage control signal to the coupled trigger isolation circuit after the undervoltage delay process ends. The structure is simple and the cost is low.

Description

Time-delayed overvoltage and undervoltage protection circuit for switching appliances

technical field

The utility model belongs to the field of low-voltage electrical appliances, in particular to an electronic circuit for switching electrical appliances, in particular to a circuit for voltage detection, overvoltage protection and undervoltage protection with delay functions.

Background technique

Due to the instability of the grid voltage or human-induced wiring errors (such as applying 380V voltage to a 230V circuit), the voltage on the power side of the circuit breaker often appears overvoltage (exceeding the rated voltage of the circuit breaker) or undervoltage ( lower than the rated voltage of the circuit breaker), these abnormal conditions often lead to the problem of burning out the electrical equipment on the load side of the lower end of the circuit breaker. For this reason, people urgently need an overvoltage and undervoltage (referred to as "overvoltage and undervoltage") protection circuit. When the voltage on the power supply side appears overvoltage or undervoltage, the tripping of the circuit breaker is automatically controlled by this overvoltage and undervoltage protection circuit. Trip and cut off the power output, thereby preventing adverse consequences caused by overvoltage and undervoltage on the load side of the lower end of the circuit breaker.

At present, the overvoltage and undervoltage protection circuits used in traditional switching appliances mainly include three categories: one is only overvoltage protection, no undervoltage protection and surge protection, and the protection function is not complete. The second is that although the overvoltage and undervoltage full protection circuit is adopted, the circuit structure is complicated, not only the manufacturing cost is high, it is difficult to apply to the small circuit breaker, and because the same resistance is used as both the detection element of the overvoltage and the detection element of the undervoltage Partly, over-voltage and under-voltage debugging interact with each other during the production process, and the pass rate is low; moreover, only using varistors to absorb surge voltage requires the use of large-volume and high-cost varistors. The third is that the circuit work lacks stability and reliability. It is known that the destructiveness of overvoltage or undervoltage is closely related to the length of time it acts on the load equipment. However, instantaneous overvoltage or undervoltage, such as less than 0.3 seconds, is very destructive to commonly used load equipment, even It can be ignored. When the power supply voltage has a common instantaneous overvoltage or undervoltage that does not pose a threat to the load equipment, the overvoltage and undervoltage protection circuit will not work reliably, which may cause unnecessary tripping and misoperation, seriously affecting normal power consumption. , and most of the overvoltage or undervoltage fluctuations of the power grid are instantaneous fluctuations. Therefore, if the false tripping caused by instantaneous overvoltage and undervoltage can be reasonably avoided, it is very necessary and beneficial to ensure the normal order of power consumption. Some overvoltage and undervoltage protection circuits do not consider this safety measure. Although there are circuits using filter capacitors, they can only filter out the interference of high-order harmonics to the circuit, but it cannot effectively improve the problem of unnecessary tripping of circuit breakers caused by instantaneous overvoltage or undervoltage.

Utility model content

The technical problem to be solved by the utility model is to provide a time-delayed overvoltage and undervoltage protection circuit for switching appliances with simple circuit, low cost, strong anti-interference ability and certain delay function.

The technical scheme that the utility model adopts for realizing the above object is:

A time-delayed overvoltage and undervoltage protection circuit for switching appliances, including a sequentially coupled surge absorbing circuit, a half-wave rectification circuit, a detection circuit, a trigger isolation circuit, and an execution circuit, characterized in that the detection circuit includes: Overvoltage detection delay circuit and undervoltage detection delay circuit. The overvoltage detection delay circuit is composed of two voltage divider resistors sampling from the DC output terminal of the half-wave rectifier circuit and charging a capacitor. When the sampling result is greater than its overvoltage When the overvoltage setting value is set, the overvoltage detection delay circuit has an overvoltage delay process, and can output an overvoltage control signal to the coupled trigger isolation circuit after the overvoltage delay process is over, so that the trigger isolation circuit controls execution The circuit performs a trip action. Undervoltage detection delay circuit, the emitter of its transistor Q1 obtains the reference voltage from the DC output terminal of the half-wave rectification circuit, and the base of the transistor Q1 is sampled from the DC output terminal of the half-wave rectification circuit through two voltage dividing resistors, When the sampling result is less than the undervoltage setting value, the triode Q1 is turned on, and the undervoltage detection delay circuit has an undervoltage delay process, and can only output to the coupled trigger isolation circuit after the undervoltage delay process ends. The undervoltage control signal enables the trigger isolation circuit to control the execution circuit to perform a tripping action.

The half-wave rectification circuit includes a rectification diode VD1, the anode of the rectification diode VD1 is an AC input terminal connected to the electromagnetic tripping coil KA of the executive circuit, and the AC power supply passes through the electromagnetic tripping coil KA and then the diode VD1 Perform half-wave rectification; the cathode of the rectifier diode VD1 is a DC output terminal, which is used to provide a DC power supply for the circuit and a sampling voltage for the circuit at the same time.

Further: the surge absorbing circuit includes a piezoresistor RV1 and a current-limiting coil KA1 of an electromagnetic tripping coil KA, one end of the current-limiting coil KA1 is connected to the live wire L of the AC power supply, and the other end of the current-limiting coil KA1 It is connected with one end of the varistor RV1, and the other end of the varistor RV1 is connected with the neutral phase N of the AC power supply. The above-mentioned electromagnetic tripping coil KA includes a current-limiting coil KA1 and a coil KA2, which are used to perform the tripping action described in the circuit. At the same time, the current-limiting coil KA1 is used to absorb the instantaneous surge voltage. One end of the coil KA2 is connected to The AC input end of the half-wave rectification circuit is connected, and the other end of the coil KA2 is connected in parallel with one end of the varistor RV1 of the surge absorbing circuit.

The overvoltage delay circuit is provided with an overvoltage delay capacitor C1, and the overvoltage delay process is formed by the charging time of the overvoltage delay capacitor C1; the end of the overvoltage delay process means that the half-wave The voltage at the DC output end of the rectifier circuit is higher than the overvoltage setting value for a duration greater than or equal to the charging time of the overvoltage delay capacitor C1.

Further: one end of the voltage dividing resistor R1 in the overvoltage detection delay circuit is connected to the DC output end of the half-wave rectifier circuit, one end of the voltage dividing resistor R2, and one end of the overvoltage delay capacitor C1 are connected in parallel to the ground , the other end of the voltage dividing resistor R1, the other end of the voltage dividing resistor R2, and the other end of the delay capacitor C1 are connected in parallel with the overvoltage control input end of the trigger isolation circuit.

The undervoltage delay capacitor C3 is provided in the undervoltage detection delay circuit, and the undervoltage delay process is formed by the charging time of the undervoltage delay capacitor C3; the end of the undervoltage delay process means that the half-wave The voltage at the DC output end of the rectifier circuit is lower than the undervoltage set value for a duration greater than or equal to the charging time of the undervoltage delay capacitor C3. Further: the above-mentioned undervoltage detection delay circuit also includes a resistor R3, a resistor R4, a resistor R5, a resistor R7, a resistor R8, a voltage regulator tube VZ1, and a capacitor C2, wherein one end of the resistor R3, one end of the resistor R4 and the half-wave The DC output terminals of the rectifier circuit are connected in parallel, the E pole of the transistor Q1, the negative pole of the voltage regulator VZ1, one end of the capacitor C2 and the other end of the resistor R3 are connected in parallel, the B pole of the transistor Q1 is connected with one end of the resistor R7, and the transistor Q1’s The C pole is connected to one end of the resistor R8, the other end of the resistor R8, one end of the undervoltage delay capacitor C3 are connected in parallel with the undervoltage control input end of the trigger isolation circuit, the other end of the undervoltage delay capacitor C3 is connected to the positive pole of the voltage regulator tube VZ1 1. One end of the resistor R5 is connected in parallel with the ground electrode, and the other end of the capacitor C2, the other end of the resistor R4, and the other end of the resistor R5 are connected in parallel with the other end of the resistor R7.

The trigger isolation circuit includes a voltage regulator VZ2 and a diode VD2, the negative pole of the voltage regulator VZ2 is an input terminal for overvoltage control, the anode of the diode VD2 is an input terminal for undervoltage control, the positive pole of the voltage regulator VZ2 and the negative pole of the diode VD2 It is connected in parallel with the tripping control input end of the executive circuit.

The executive circuit includes an electromagnetic tripping coil KA, a thyristor SCR and a capacitor C4, and the electromagnetic tripping coil KA is connected in series between the live wire phase L of the AC power supply and the AC input end of the half-wave rectification circuit , the control electrode of the thyristor SCR is connected in parallel with one end of the capacitor C4 to form a trip control input end, the anode of the thyristor SCR is connected to the DC output end of the half-wave rectifier circuit, the cathode of the thyristor SCR, and the other end of the capacitor C4 One end is connected in parallel with ground.

The utility model has the advantage that it adopts a simple circuit structure, which not only realizes the functions of overvoltage protection, undervoltage protection and anti-surge impact, but also expands the functions of overvoltage detection delay and undervoltage detection delay, Therefore, unnecessary tripping caused by instantaneous overvoltage and instantaneous undervoltage can be effectively avoided, the safety and reliability of the tripping action are comprehensively improved, and the performance of the circuit breaker is improved. The overvoltage and undervoltage protection circuit of the circuit breaker of the present invention also effectively solves the problems of overvoltage protection and undervoltage protection in existing product circuits, which are difficult to debug and have poor anti-interference ability, and can further optimize the miniaturization design and Low cost manufacturing.

Description of drawings

Fig. 1 is a structural block diagram of a time-delayed overvoltage and undervoltage protection circuit of a switching device of the present invention.

Fig. 2 is a circuit structure schematic diagram of an embodiment of a time-delayed overvoltage and undervoltage protection circuit of a switching device of the present invention.

detailed description

The specific implementation of the time-delayed overvoltage and undervoltage protection circuit of the switching device of the present invention will be further described below in conjunction with the embodiments given in Figures 1 and 2 .

Referring to Figures 1 and 2, a time-delayed overvoltage and undervoltage protection circuit for use in conjunction with circuit breakers and other switching devices includes sequentially coupled surge absorbing circuits, half-wave rectification circuits, detection circuits, trigger isolation circuits and The execution circuit, the detection circuit further includes: an overvoltage detection delay circuit and an undervoltage detection delay circuit, and the overvoltage detection delay circuit is sampled from the DC output terminal of the half-wave rectification circuit by two voltage dividing resistors and A capacitor is charged, and when the sampling result is greater than its overvoltage set value, the overvoltage detection delay circuit has an overvoltage delay process, and the coupled trigger isolation circuit can only be sent to the coupled trigger isolation circuit after the overvoltage delay process ends. Output the overvoltage control signal, so that the trigger isolation circuit controls the execution circuit to perform the tripping action. Undervoltage detection delay circuit, the emitter of its transistor Q1 obtains the reference voltage from the DC output terminal of the half-wave rectification circuit, and the base of the transistor Q1 is sampled from the DC output terminal of the half-wave rectification circuit through two voltage dividing resistors, When the sampling result is less than the undervoltage setting value, the triode Q1 is turned on, and the undervoltage detection delay circuit has an undervoltage delay process, and can only output to the coupled trigger isolation circuit after the undervoltage delay process ends. The undervoltage control signal enables the trigger isolation circuit to control the execution circuit to perform a tripping action.

In the embodiment of Fig. 2, the described rectification circuit is a half-wave rectification circuit, which includes a rectification diode VD1. The two input terminals are respectively connected to the live wire phase L and the neutral wire N in the power grid, and the live wire phase L and the neutral wire N on the load side are connected to the electric equipment (load equipment). The half-wave rectifier circuit has an AC input terminal and a DC output terminal, the anode of the rectifier diode VD1 is connected to the AC input terminal of the electromagnetic tripping coil KA of the surge absorbing circuit, and the surge absorbing circuit is connected to Between the live wire phase L and the neutral wire N of the AC power supply, the AC power supply takes the AC power from the live wire phase L through the electromagnetic tripping coil KA, and then conducts half-wave rectification by the diode VD1; the negative pole of the rectifier diode VD1 is DC The output terminal, the DC output terminal is the positive pole of the DC output of the half-wave rectification circuit, and the negative pole of the DC output of the half-wave rectification circuit is connected to the neutral line N to form a common ground pole. Specifically, the surge absorbing circuit is composed of a current-limiting coil KA1 of a two-stage electromagnetic trip coil KA and a piezoresistor RV1. One end of the current-limiting coil KA1 is connected to the live wire L of the AC power supply, and the current-limiting coil KA1 The other end of the varistor RV1 is connected to one end of the varistor RV1, and the other end of the varistor RV1 is connected to the neutral phase N of the AC power supply. The electromagnetic trip coil KA of the executive circuit includes a current-limiting coil KA1 and a coil KA2, one end of the current-limiting coil KA1 is connected to the live line L of the AC power supply, and one end of the coil KA2 is connected to the AC input end of the half-wave rectifier circuit , the other end of the current limiting coil KA1 and the other end of the coil KA2 are connected in parallel with one end of the varistor RV1 of the surge absorbing circuit, and the other end of the varistor RV1 is connected with the neutral phase N of the AC power supply. The anode of the rectifier diode VD1 is an AC input terminal, which is connected to one end of the electromagnetic tripping coil KA of the executive circuit, and the other end of the electromagnetic tripping coil KA is connected to the phase L of the live wire to obtain AC power from the phase L of the live wire. The cathode of the rectifier diode VD1 is the DC output terminal, because the fluctuation of the DC voltage (voltage to ground) at the DC output terminal is consistent with the fluctuation of the AC voltage (voltage to the neutral line N) at the AC input terminal. Therefore, the DC output terminal of the utility model is not only used to provide DC power for the circuit, but also used as a sampling node for overvoltage or undervoltage. The advantage of using the above-mentioned half-wave rectifier circuit combined with the current-limiting coil KA1 in the electromagnetic tripping coil KA of the executive circuit to form a surge absorbing circuit structure is that: since the surge is buffered by the current-limiting coil KA1 first, it is buffered by the varistor RV1 absorbs, thus greatly reducing the impact on the varistor RV1, not only can effectively improve the ability of the surge absorbing circuit, but also can effectively reduce the energy level and volume of the varistor RV1, which is conducive to the miniaturization of the product ; Since the surge only passes through the current-limiting coil KA1 and not through the coil KA2 in the electromagnetic tripping coil KA, it can effectively prevent the tripping action caused by the surge, which is beneficial to improve the performance of ensuring normal power supply. At the same time, the rectifier diode VD1 not only has the function of rectification, but also has the function of reducing the DC output voltage (the DC voltage at the DC output terminal is about 0.45 times the AC voltage at the AC input terminal), so the drop-down resistor can be omitted, which is not only beneficial to reduce the volume, Reduce costs, but also help reduce temperature rise.

The executive circuit includes an electromagnetic tripping coil KA, a thyristor SCR and a capacitor C4. The electromagnetic tripping coil KA is connected in series between the live wire phase L of the AC power supply and the AC input end of the half-wave rectifier circuit, and is controllable The control electrode of the silicon SCR is connected in parallel with one end of the capacitor C4 to form a trip control input end, the anode of the silicon controlled silicon SCR is connected to the DC output end of the half-wave rectifier circuit, the cathode of the silicon controlled silicon SCR, the other end of the capacitor C4 are connected to the ground connected in parallel. When the overvoltage detection delay circuit or undervoltage detection delay circuit outputs a trigger signal through the trigger isolation circuit, the thyristor SCR is triggered, and the thyristor SCR is turned on, so that the electromagnetic tripping coil KA operates, and the capacitor C4 acts as an anti-interference effect. The advantage of the execution circuit with the above structure is that the structure is simple, especially the electromagnetic tripping coil KA with tripping function and surge absorption function is used, which can not only effectively reduce the number of electronic components used, but also effectively ensure and improve tripping performance and surge absorption performance.

The detection circuit of the delayed overvoltage and undervoltage protection circuit of the utility model includes an overvoltage detection delay circuit, which samples from the DC output terminal of the half-wave rectifier circuit, and outputs to the isolation circuit when the sampling result is greater than the set value of the overvoltage Overvoltage control signal. The over-voltage detection delay circuit is provided with an over-voltage delay capacitor C1, and the over-voltage delay process is formed by the charging time of the over-voltage delay capacitor C1; When the time is greater than or equal to the charging time of the overvoltage delay capacitor C1, the overvoltage detection delay circuit can output the overvoltage control signal; otherwise, the overvoltage control signal cannot be output. The specific structure of overvoltage detection time delay circuit can have multiple, and a kind of preferred structure is as shown in Figure 2, and described overvoltage detection time delay circuit comprises voltage divider R1, voltage divider resistor R2 and overvoltage time delay capacitor C1 , one end of the voltage dividing resistor R1 is connected to the DC output terminal of the half-wave rectifier circuit, one end of the voltage dividing resistor R2 and one end of the overvoltage delay capacitor C1 are connected in parallel with the ground electrode, the other end of the voltage dividing resistor R1 is connected to the voltage dividing resistor R2 The other end of the overvoltage delay capacitor C1 is connected in parallel with the overvoltage control input end of the trigger isolation circuit.

The working principle of the overvoltage detection delay circuit is as follows: After the grid AC power is half-wave rectified, the resistor R1 and the resistor R2 divide the voltage and charge the capacitor C1. When the grid voltage is greater than the set voltage, after the capacitor C1 is charged for a certain period of time, the voltage rises to be greater than the voltage regulation value of the voltage regulator tube VZ2, and the voltage regulator tube is turned on to form a trigger signal. The specific process is: when the voltage (i.e. the sampling result) of the DC output terminal of the half-wave rectifier circuit (i.e. one end of the voltage dividing resistor R1) is less than or equal to the overvoltage setting value, the voltage at the other end of the voltage dividing resistor R1 is less than the trigger The regulated value of the voltage regulator tube VZ2 of the isolation circuit, the voltage regulator tube VZ2 is not turned on, so the overvoltage detection delay circuit cannot output a voltage signal to the isolation circuit; when the voltage of the DC output terminal of the half-wave rectifier circuit is greater than the overvoltage setting value, the other end of the voltage dividing resistor R1 first charges the overvoltage delay capacitor C1 (that is, enters the delay process). During this charging delay process, the voltage at the other end of the voltage dividing resistor R1 is always lower than the stable voltage regulator VZ2, the voltage regulator VZ2 is not conducting, so the overvoltage detection delay circuit cannot output a voltage signal to the isolation circuit; during the charging delay process, if the DC output of the half-wave rectifier circuit When the voltage recovers to be less than or equal to the set value of the overvoltage, the voltage at the other end of the voltage dividing resistor R1 remains in a state less than the voltage regulation value of the voltage regulator VZ2 that triggers the isolation circuit, that is, the voltage regulator VZ2 does not conduct Therefore, the overvoltage detection delay circuit still cannot output a voltage signal to the isolation circuit; Overvoltage setting value, the voltage at the other end of the voltage dividing resistor R1 rises to the regulated value of the voltage regulator tube VZ2, and the voltage regulator tube VZ2 is turned on. Only in this case, the overvoltage detection delay circuit can Triggering the output voltage signal of the isolation circuit triggers the conduction of the thyristor SCR, causing the electromagnetic tripping coil KA of the execution circuit to perform a tripping action.

The detection circuit of the time-delayed overvoltage and undervoltage protection circuit of the present invention also includes an undervoltage detection delay circuit, which samples from the DC output terminal of the half-wave rectifier circuit. When the sampling result is less than the undervoltage setting value, the The undervoltage detection delay circuit first enters the undervoltage delay process, and can output the undervoltage control signal to the isolation circuit after the undervoltage delay process ends. The undervoltage detection delay circuit is provided with an undervoltage delay capacitor C3, and the undervoltage delay process is formed by the charging time of the undervoltage delay capacitor C3; When the time is greater than or equal to the charging time of the undervoltage delay capacitor C3, the undervoltage detection delay circuit can output the undervoltage control signal; otherwise, the undervoltage control signal cannot be output. The specific structure of undervoltage detection delay circuit can have multiple, a kind of preferred structure as shown in Figure 2, described undervoltage detection delay circuit comprises resistance R3, resistance R4, resistance R5, resistance R7, resistance R8, Voltage regulator VZ1, triode Q1, capacitor C2 and undervoltage delay capacitor C3, one end of resistor R3, one end of resistor R4 are connected in parallel with the DC output end of the half-wave rectifier circuit, the E pole (emitter) of transistor Q1, voltage regulator The negative pole of the tube VZ1, one end of the capacitor C2 and the other end of the resistor R3 are connected in parallel, the B pole (base) of the transistor Q1 is connected to one end of the resistor R7, and the C pole (collector) of the transistor Q1 is connected to one end of the resistor R8. The other end of the resistor R8, one end of the undervoltage delay capacitor C3 are connected in parallel with the undervoltage control input end of the trigger isolation circuit, the other end of the undervoltage delay capacitor C3, the positive pole of the voltage regulator tube VZ1, and one end of the resistor R5 are connected in parallel with the ground The other end of the capacitor C2, the other end of the resistor R4, the other end of the resistor R5 and the other end of the resistor R7 are connected in parallel.

The working principle of the undervoltage detection delay circuit is as follows: After the grid AC power is half-wave rectified, a reference voltage is provided to the emitter of the triode Q1 through the resistor R3 and the voltage regulator tube VZ1; after the grid AC power is half-wave rectified , through the resistor R4 and the resistor R5 to divide the voltage, a control voltage is provided to the base of the triode Q1. When the grid voltage is lower than the set value, the control voltage of the base of the transistor Q1 is lower than the reference voltage of the emitter of the transistor Q1, the transistor Q1 is turned on, and the reference voltage charges the capacitor C3 through the transistor Q1 and the resistor R8. After charging for a period of time, after the voltage rises to the set value, a trigger signal is formed through the diode VD2. The specific process is: after the DC voltage at the DC output terminal of the half-wave rectifier circuit passes through the resistor R3 and the voltage regulator VZ1, it provides a reference voltage to the E pole of the triode Q1, and the reference voltage is modulated by the voltage regulation value of the voltage regulator VZ1; Q1 adopts PNP tube, the DC voltage of the DC output end of the half-wave rectifier circuit is connected in parallel with the other end of the resistor R4 and the control voltage node (that is, the other end of the capacitor C2, the other end of the resistor R4, the other end of the resistor R5, and the other end of the resistor R7 The node formed), the resistor R7 is loaded to the B pole of the transistor Q1, when the DC voltage at the DC output terminal is greater than the undervoltage setting value, the voltage of the B pole of the transistor Q1 is higher than the reference voltage, the transistor Q1 is cut off, and the other side of the resistor R8 There is no voltage output at one end; when the DC voltage at the DC output terminal is lower than the undervoltage setting value, the B-pole voltage of the transistor Q1 is lower than the reference voltage, the transistor Q1 is turned on, and the other end of the resistor R8 is first charged to the undervoltage delay capacitor C3 (ie enter the delay process), the charging of the undervoltage delay capacitor C3 makes the undervoltage control signal unable to output to the trigger isolation circuit; during the charging delay process, if the voltage at the DC output terminal of the half-wave rectifier circuit recovers to be greater than or equal to Undervoltage setting value, the transistor Q1 is switched from on to off, and the other end of the resistor R8 is switched to no voltage output; if the charging delay process is completed and the half-wave rectifier circuit The voltage at the DC output terminal (that is, the sampling result) is always kept below the undervoltage set value, and the voltage at the other end of the resistor R8 increases with the end of the charging delay process to form an undervoltage control signal. The undervoltage control signal Output to the undervoltage control input terminal of the trigger isolation circuit, and trigger the conduction of the thyristor SCR, causing the electromagnetic tripping coil KA to perform tripping.

Because the utility model adopts the detection circuit of the delay overvoltage and undervoltage protection circuit, it has a very beneficial advantage: the trigger isolation circuit can be controlled according to the overvoltage control signal input by the overvoltage detection delay circuit or the undervoltage detection delay The undervoltage control signal input by the circuit controls the execution circuit to perform the tripping action, and when the grid voltage is higher than the set value, the overvoltage detection delay circuit outputs a trigger signal, and the voltage regulator VZ2 is turned on, but the diode VD2 is reversed. , not affected by the undervoltage detection delay circuit. When the grid voltage is lower than the set value, the undervoltage detection delay circuit outputs a trigger signal, but the trigger signal is less than the divided voltage of resistor R1 and resistor R2, and the voltage regulator VZ2 is not turned on, which is not affected by the overvoltage detection delay circuit influences. The specific structure of the trigger isolation circuit of the present utility model can have many kinds, and a kind of preferred structure is shown in Figure 2, and described trigger isolation circuit comprises voltage regulator VZ2 and diode VD2, and the negative pole of voltage regulator VZ2 is overvoltage As for the control input terminal, the anode of the diode VD2 is the undervoltage control input terminal, and the anode of the voltage regulator VZ2 and the cathode of the diode VD2 are connected in parallel with the trip control input terminal of the execution circuit. Since the trigger isolation circuit has two control input terminals (namely: the undervoltage control input terminal formed by the positive pole of the diode VD2; the overvoltage control input terminal formed by the positive pole of the diode VD2) and one control output node (the voltage regulator tube VZ2 The positive pole and the negative pole of the diode VD2 are connected in parallel), so it can output the overvoltage control signal output by the overvoltage detection delay circuit and the undervoltage control signal output by the undervoltage detection delay circuit in parallel to the tripping control of the execution circuit The input terminal (that is, the control pole of the silicon controlled rectifier SCR), that is to say, the trigger isolation circuit is controlled according to the overvoltage control signal input by the overvoltage detection delay circuit or the undervoltage control signal input by the undervoltage detection delay circuit. The executive circuit executes the tripping action, and realizes that the overvoltage control signal and the undervoltage control signal are parallel and do not interfere with each other to control the tripping action of the executive circuit, and the circuit is very simple and reliable, which is conducive to the miniaturization and low cost of the product.

The above content is a further detailed description of the utility model in combination with specific preferred embodiments, and it cannot be assumed that the specific implementation of the utility model is only limited to these descriptions. For those of ordinary skill in the technical field to which the utility model belongs, on the premise of not departing from the concept of the utility model, some simple deduction or replacement can also be made, which should be regarded as belonging to the protection scope of the utility model.

Claims (10)

1. A time-delayed overvoltage and undervoltage protection circuit for switching appliances, comprising a sequentially coupled surge absorbing circuit, a half-wave rectifier circuit, a detection circuit, a trigger isolation circuit and an execution circuit, characterized in that the detection circuit include: The overvoltage detection delay circuit is composed of two voltage dividing resistors sampling from the DC output terminal of the half-wave rectifier circuit and charging a capacitor. When the sampling result is greater than its overvoltage setting value, the overvoltage detection delay The timing circuit has an overvoltage delay process, and can only output an overvoltage control signal to the coupled trigger isolation circuit after the overvoltage delay process ends, so that the trigger isolation circuit controls the execution circuit to perform a tripping action; Undervoltage detection delay circuit, the emitter of its transistor Q1 obtains the reference voltage from the DC output terminal of the half-wave rectification circuit, and the base of the transistor Q1 is sampled from the DC output terminal of the half-wave rectification circuit through two voltage dividing resistors, When the sampling result is less than the undervoltage setting value, the triode Q1 is turned on, and the undervoltage detection delay circuit has an undervoltage delay process, and can only output to the coupled trigger isolation circuit after the undervoltage delay process ends. The undervoltage control signal enables the trigger isolation circuit to control the execution circuit to perform a tripping action. 2. The delayable overvoltage and undervoltage protection circuit for switching appliances according to claim 1, characterized in that: the half-wave rectifier circuit includes a rectifier diode VD1, and the anode of the rectifier diode VD1 is electromagnetically decoupled from the executive circuit. The AC input terminal connected to the buckle coil KA, the AC power supply is half-wave rectified by the diode VD1 through the electromagnetic trip coil KA; the cathode of the rectifier diode VD1 is a DC output terminal, and the DC output terminal is used to provide DC for the circuit The power supply provides sampling voltage for the circuit at the same time. 3. The time-delayable overvoltage and undervoltage protection circuit for switching appliances according to claim 1, characterized in that: the surge absorbing circuit includes a piezoresistor RV1 and a current-limiting coil KA1 of an electromagnetic tripping coil KA, One end of the current limiting coil KA1 is connected to the live wire L of the AC power supply, the other end of the current limiting coil KA1 is connected to one end of the varistor RV1, and the other end of the varistor RV1 is connected to the neutral phase N of the AC power supply. 4. The time-delayable overvoltage and undervoltage protection circuit for switching appliances according to claim 3, characterized in that: the electromagnetic tripping coil KA includes a current limiting coil KA1 and a coil KA2, which are used to execute the circuit described in the circuit. The tripping action is performed, and the current-limiting coil KA1 is used to absorb the instantaneous surge voltage. One end of the coil KA2 is connected to the AC input end of the half-wave rectifier circuit, and the other end of the coil KA2 is connected to the varistor of the surge absorption circuit. One end of RV1 is connected in parallel. 5. The delayable overvoltage and undervoltage protection circuit for switching appliances according to claim 1, characterized in that: the overvoltage detection delay circuit is provided with an overvoltage delay capacitor C1, and the overvoltage delay process It is formed by the charging time of the overvoltage delay capacitor C1; the end of the overvoltage delay process means that the voltage at the DC output terminal of the half-wave rectifier circuit is higher than the overvoltage set value for a duration greater than or equal to the overvoltage The state of the charging time of capacitor C1 during the delay. 6. The delayable overvoltage and undervoltage protection circuit for switching appliances according to claim 1 or 5, characterized in that: one end of the voltage dividing resistor R1 in the overvoltage detection delay circuit is connected to the half-wave rectifier circuit DC output terminal connection, one end of the voltage dividing resistor R2, one end of the overvoltage delay capacitor C1 are connected in parallel with the ground electrode, the other end of the voltage dividing resistor R1, the other end of the voltage dividing resistor R2, and the other end of the delay capacitor C1 are connected to the trigger The overvoltage control input terminals of the isolation circuit are connected in parallel. 7. The delayable overvoltage and undervoltage protection circuit for switching appliances according to claim 1, characterized in that: an undervoltage delay capacitor C3 is provided in the undervoltage detection delay circuit, and the undervoltage delay process It is formed by the charging time of the undervoltage delay capacitor C3; the end of the undervoltage delay process means that the voltage at the DC output terminal of the half-wave rectifier circuit is lower than the undervoltage set value for a duration greater than or equal to the undervoltage The state of the charging time of capacitor C3 during the delay. 8. The delayable overvoltage and undervoltage protection circuit for switching appliances according to claim 1 or 7, characterized in that: the undervoltage detection delay circuit also includes a resistor R3, a resistor R4, a resistor R5, a resistor R7, Resistor R8, voltage regulator tube VZ1, and capacitor C2, wherein one end of resistor R3 and one end of resistor R4 are connected in parallel with the DC output end of the half-wave rectifier circuit, the E pole of transistor Q1, the negative pole of voltage regulator tube VZ1, and the capacitor C2 One end is connected in parallel with the other end of the resistor R3, the B pole of the triode Q1 is connected with one end of the resistor R7, the C pole of the triode Q1 is connected with one end of the resistor R8, the other end of the resistor R8, and one end of the undervoltage delay capacitor C3 are isolated from the trigger The undervoltage control input terminal of the circuit is connected in parallel, the other end of the undervoltage delay capacitor C3, the positive pole of the voltage regulator tube VZ1, one end of the resistor R5 are connected in parallel with the ground, the other end of the capacitor C2, the other end of the resistor R4, and the resistor R5 The other end of the resistor R7 is connected in parallel with the other end of the resistor R7. 9. The delayable overvoltage and undervoltage protection circuit for switching appliances according to claim 1, characterized in that: the trigger isolation circuit includes a voltage regulator tube VZ2 and a diode VD2, and the negative pole of the voltage regulator tube VZ2 is used for overvoltage control At the input end, the anode of the diode VD2 is an undervoltage control input end, and the anode of the voltage regulator VZ2 and the cathode of the diode VD2 are connected in parallel with the tripping control input end of the executive circuit. 10. The delayable overvoltage and undervoltage protection circuit for switching appliances according to claim 1, characterized in that: the executive circuit includes an electromagnetic tripping coil KA, a thyristor SCR and a capacitor C4, and the electromagnetic The type tripping coil KA is connected in series between the live wire phase L of the AC power supply and the AC input end of the half-wave rectifier circuit, the control pole of the thyristor SCR is connected in parallel with one end of the capacitor C4 to form a tripping control input end, and the thyristor The anode of the SCR is connected to the DC output terminal of the half-wave rectifier circuit, and the cathode of the thyristor SCR and the other end of the capacitor C4 are connected in parallel to the ground.