CN219268479U - Overvoltage and undervoltage protection circuit - Google Patents
Overvoltage and undervoltage protection circuit Download PDFInfo
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- CN219268479U CN219268479U CN202223470554.7U CN202223470554U CN219268479U CN 219268479 U CN219268479 U CN 219268479U CN 202223470554 U CN202223470554 U CN 202223470554U CN 219268479 U CN219268479 U CN 219268479U
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Abstract
The utility model discloses an over-under voltage protection circuit in the field of protection circuits, which comprises an alternating current-direct current conversion circuit, wherein the alternating current-direct current conversion circuit is connected with a voltage dividing circuit, and the voltage dividing circuit is respectively connected with an upper limit voltage control circuit and a lower limit voltage control circuit; the alternating current is converted into direct current through an alternating current-direct current conversion circuit, then the direct current is divided by a voltage dividing circuit, the voltage output by the power supply is supplied to an upper limit voltage control circuit and a lower line voltage control circuit, the circuit is cut off when overvoltage and front voltage are respectively carried out through the upper limit voltage control circuit and the lower line voltage control circuit, and the power supply is restarted to restore after the power supply voltage is restored to be normal.
Description
Technical Field
The utility model relates to a current limiting protection circuit in the field of protection circuits.
Background
The voltage above the nominal value is called overvoltage and below the nominal value is called undervoltage. The rated value is a value which is counted in a normal fluctuation range, various electric equipment has different nominal (rated) voltages and allowable voltage fluctuation ranges, and over (or under) voltages occur when the allowable fluctuation ranges are exceeded. Overvoltage is caused by power frequency, resonance, operation and lightning, and can cause accidents such as power supply and distribution, breakdown of electric equipment, burning out, personal injury and death and the like. Under-voltage can cause accidents such as reduced production efficiency, influence on normal life, even motor burnout (when the time is longer), large-area power failure and the like. In the prior art, although the voltage protection is performed by over (or under), the precision is insufficient, the reaction is not rapid, and misoperation is easy to occur.
Disclosure of Invention
The utility model aims to provide an over-under voltage protection circuit which has high precision, quick response and no misoperation.
In order to achieve the above objective, the present utility model provides an over-under voltage protection circuit, which includes an ac-dc conversion circuit connected to a voltage dividing circuit, the voltage dividing circuit being connected to an upper limit voltage control circuit and a lower limit voltage control circuit, respectively.
Compared with the prior art, the utility model has the beneficial effects that the alternating current is converted into the direct current through the alternating current-direct current conversion circuit, the voltage is divided by the voltage dividing circuit, the voltage output by the power supply is supplied to the upper limit voltage control circuit and the lower line voltage control circuit to change the sampling voltage, the circuits are cut off respectively when the overvoltage and the front voltage are generated through the upper limit voltage control circuit and the lower line voltage control circuit, and the power supply is restarted to restore after the power supply voltage is restored to be normal.
As a further improvement of the utility model, the AC-DC conversion circuit comprises a step-down transformer, a primary side power supply of the step-down transformer, a No. 1 pin and a No. 2 pin of a secondary side rectifier bridge of the transformer, and a No. 3 pin and a No. 4 pin of the rectifier bridge are connected with a voltage dividing circuit; therefore, the alternating current output by the power supply can be changed into direct current through the rectifier bridge after being reduced by the transformer, and the direct current is provided for a subsequent circuit.
As a further improvement of the utility model, the voltage dividing circuit comprises a voltage dividing resistor R1 and a voltage dividing resistor R2, wherein one end of the voltage dividing resistor R1 is respectively connected with the upper limit voltage control circuit and the pin 4 of the rectifier bridge, the other end of the voltage dividing resistor R1 is respectively connected with the upper limit voltage control circuit and one end of the voltage dividing resistor R2, and the other end of the voltage dividing resistor R2 is respectively connected with the pin 3 of the rectifier bridge and the upper limit voltage control circuit.
Therefore, after the direct current is subjected to voltage division treatment through the two voltage dividing resistors, the direct current is connected into the upper limit voltage control circuit and the lower limit voltage control circuit, and the damage of components caused by overlarge voltage is avoided.
As a further improvement of the present utility model, the upper limit voltage control circuit includes a variable resistor R3, a relay K1, and a thyristor D2, one end of the variable resistor R3 is connected to the other end of the voltage dividing resistor R1 and the lower limit voltage control circuit, respectively, the other end of the variable resistor R3 is connected to the gate of the thyristor D2, the cathode of the thyristor D2 is connected to the other end of the voltage dividing resistor R2 and the lower limit voltage control circuit, respectively, the anode of the thyristor D2 is connected to one end of the coil of the relay K1, the other end of the coil of the relay K1 is connected to one end of the voltage dividing resistor, the normally closed contact of the relay K1 is connected to the lower limit voltage control circuit, and the movable contact of the relay K1 is connected to one end of the primary side of the transformer.
In this way, once overvoltage occurs, the responsibility thyristor D2 is conducted, the coil of the relay K1 is electrified, and the movable contact is attracted with the normally open contact, so that the voltage output by the power supply is cut off, and the damage of the electric equipment due to overvoltage is avoided.
As a further improvement of the utility model, the lower limit voltage control circuit comprises a variable resistor R4, a relay K2 and a thyristor D3, wherein one end of the variable resistor R4 is connected with one end of the variable resistor R3, the other end of the variable resistor R4 is connected with the gate of the thyristor D3, the cathode of the thyristor D3 is connected with the cathode of the thyristor D2, the anode of the thyristor D3 is connected with one end of a coil of the relay K2, the other end of the coil of the relay K2 is connected with one end of a voltage dividing resistor R1, the movable contact of the relay K2 is connected with the normally-closed contact of the relay K1, and the normally-closed contact of the relay K2 is connected with the output end.
When the voltage is too low, the thyristor D3 is cut off, so that the coil of the relay K2 is powered off, and the movable contact and the normally closed contact are attracted, so that the power supply output voltage is cut off, and the equipment cannot be normally used or damaged due to the too low voltage is avoided.
As a further improvement of the utility model, the coil of the relay K1 is connected in parallel with the freewheel diode D1, and the coil of the relay K2 is connected in parallel with the freewheel diode D4; the thyristor is protected from damage by the freewheeling diodes D1 and D4.
Drawings
Fig. 1 is a circuit diagram of the present utility model.
Detailed Description
The utility model is further described below with reference to the accompanying drawings:
the overvoltage and undervoltage protection circuit shown in fig. 1 comprises an alternating current-direct current conversion circuit, wherein the alternating current-direct current conversion circuit is connected with a voltage dividing circuit, and the voltage dividing circuit is respectively connected with an upper limit voltage control circuit and a lower limit voltage control circuit; the AC-DC conversion circuit comprises a step-down transformer, a primary side power supply of the step-down transformer, a No. 1 pin and a No. 2 pin of a secondary side rectifier bridge of the transformer, and a No. 3 pin and a No. 4 pin of the rectifier bridge are connected with the voltage dividing circuit.
The voltage dividing circuit comprises a voltage dividing resistor R1 and a voltage dividing resistor R2, one end of the voltage dividing resistor R1 is connected with the upper limit voltage control circuit and the No. 4 pin of the rectifier bridge respectively, the other end of the voltage dividing resistor R1 is connected with the upper limit voltage control circuit and one end of the voltage dividing resistor R2 respectively, and the other end of the voltage dividing resistor R2 is connected with the No. 3 pin of the rectifier bridge and the upper limit voltage control circuit respectively.
The upper limit voltage control circuit comprises a variable resistor R3, a relay K1 and a thyristor D2, one end of the variable resistor R3 is respectively connected with the other end of the voltage dividing resistor R1 and the lower limit voltage control circuit, the other end of the variable resistor R3 is connected with the gate electrode of the thyristor D2, the cathode of the thyristor D2 is respectively connected with the other end of the voltage dividing resistor R2 and the lower limit voltage control circuit, the anode of the thyristor D2 is connected with one end of a coil of the relay K1, the other end of the coil of the relay K1 is connected with one end of the voltage dividing resistor, the normally closed contact of the relay K1 is connected with the lower limit voltage control circuit, and the movable contact of the relay K1 is connected with one end of the primary side of the transformer.
The lower limit voltage control circuit comprises a variable resistor R4, a relay K2 and a thyristor D3, wherein one end of the variable resistor R4 is connected with one end of the variable resistor R3, the other end of the variable resistor R4 is connected with the gate electrode of the thyristor D3, the cathode of the thyristor D3 is connected with the cathode of the thyristor D2, the anode of the thyristor D3 is connected with one end of a coil of the relay K2, the other end of the coil of the relay K2 is connected with one end of a voltage dividing resistor R1, the movable contact of the relay K2 is connected with the normally-closed contact of the relay K1, and the normally-closed contact of the relay K2 is connected with the output end. The coil of the relay K1 is connected in parallel with the freewheel diode D1, and the coil of the relay K2 is connected in parallel with the freewheel diode D4.
The voltage of the alternating current power supply is reduced by a step-down transformer, is converted into low-voltage direct current voltage after full-wave rectification by a rectifier bridge, and is output to be sampled after voltage division by voltage dividing resistors R1 and R2, the voltage changes along with the change of the alternating current power supply voltage, the upper limit voltage and the lower line voltage value are regulated by regulating the sizes of variable resistors R3 and R4, and the relay is driven to cut off and conduct the alternating current power supply by triggering the thyristor to conduct and cut off, so that the protection of a circuit is realized.
When the voltage of the alternating current power supply is in a normal range, the thyristor D2 is cut off, the movable contact of the relay K1 is connected with the normally closed contact, and the thyristor D3 is in a conducting state, so that the coil of the relay K2 is electrified, and then the contact point of the relay K2 is attracted with the normally open contact, so that the output voltage of the alternating current power supply can be loaded on the output end, and power is supplied to a subsequent circuit or equipment.
When the voltage of the alternating current power supply is in an overvoltage state, namely the voltage is higher than a set upper limit voltage, the gate electrode of the thyristor D2 passes forward voltage, and the anode of the thyristor D2 bears forward voltage, so that the thyristor D2 is conducted, the coil of the relay K1 is electrified, the movable contact and the normally open contact are attracted, and the connection between the voltage of the alternating current power supply and the output end is cut off, so that the alternating current power supply is rapidly cut off by the relay K1 under the overvoltage state, and the safety of a subsequent circuit or equipment is protected.
When the voltage of the alternating current power supply is in an undervoltage state, namely the voltage is lower than a set lower limit voltage, the gate electrode of the thyristor D2 does not pass forward voltage, although the anode of the thyristor D2 bears forward voltage, the thyristor is still in a cut-off state, so that the coil of the relay K1 is deenergized, the movable contact and the normally closed contact are attracted, the output voltage of the alternating current power supply is loaded on the movable contact of the relay K2, meanwhile, the gate electrode of the thyristor D3 does not have forward current although the anode of the thyristor D3 passes forward current, so that the thyristor D3 is in a cut-off state, so that the coil of the relay K2 is deenergized, and the movable contact and the normally closed contact are attracted, so that the voltage is not loaded at the output end despite the voltage of the alternating current power supply on the movable contact of the relay K2, and therefore, the alternating current power supply is rapidly cut off by the relay K2 in the undervoltage state, and the subsequent circuits or equipment safety is protected.
When the power supply voltage is recovered to the normal range, the normally closed contact of the relay K1 is attracted, and the normally open contact of the relay K2 is attracted, so that the power supply voltage is continuously loaded at the output end, and the normal power supply is automatically recovered.
The utility model can automatically cut off the power supply of the electric equipment, thereby playing a role in protecting the electric equipment, and can automatically recover the power supply after the power supply voltage is recovered to be normal, and the switching speed is high by utilizing the unidirectional conduction characteristic of the thyristor, so that misoperation can not occur.
In the present utility model, the present utility model is not limited to the above embodiments, and based on the technical solution of the present disclosure, those skilled in the art may make some substitutions and modifications to some technical features thereof without creative effort according to the technical disclosure, and all the substitutions and modifications are within the scope of the present utility model.
Claims (3)
1. The overvoltage and undervoltage protection circuit is characterized by comprising an alternating current-direct current conversion circuit, wherein the alternating current-direct current conversion circuit is connected with a voltage dividing circuit, and the voltage dividing circuit is respectively connected with an upper limit voltage control circuit and a lower limit voltage control circuit;
the AC-DC conversion circuit comprises a step-down transformer, a primary side power supply of the step-down transformer, a No. 1 pin and a No. 2 pin of a secondary side rectifier bridge of the transformer, and a No. 3 pin and a No. 4 pin of the rectifier bridge are connected with a voltage dividing circuit;
the voltage dividing circuit comprises a voltage dividing resistor R1 and a voltage dividing resistor R2, one end of the voltage dividing resistor R1 is respectively connected with the upper limit voltage control circuit and the No. 4 pin of the rectifier bridge, the other end of the voltage dividing resistor R1 is respectively connected with the upper limit voltage control circuit and one end of the voltage dividing resistor R2, and the other end of the voltage dividing resistor R2 is respectively connected with the No. 3 pin of the rectifier bridge and the upper limit voltage control circuit;
the upper limit voltage control circuit comprises a variable resistor R3, a relay K1 and a thyristor D2, one end of the variable resistor R3 is respectively connected with the other end of the voltage dividing resistor R1 and the lower limit voltage control circuit, the other end of the variable resistor R3 is connected with the gate electrode of the thyristor D2, the cathode of the thyristor D2 is respectively connected with the other end of the voltage dividing resistor R2 and the lower limit voltage control circuit, the anode of the thyristor D2 is connected with one end of a coil of the relay K1, the other end of the coil of the relay K1 is connected with one end of the voltage dividing resistor, the normally closed contact of the relay K1 is connected with the lower limit voltage control circuit, and the movable contact of the relay K1 is connected with one end of the primary side of the transformer.
2. An over-under-voltage protection circuit according to claim 1, wherein: the lower limit voltage control circuit comprises a variable resistor R4, a relay K2 and a thyristor D3, wherein one end of the variable resistor R4 is connected with one end of the variable resistor R3, the other end of the variable resistor R4 is connected with the gate electrode of the thyristor D3, the cathode of the thyristor D3 is connected with the cathode of the thyristor D2, the anode of the thyristor D3 is connected with one end of a coil of the relay K2, the other end of the coil of the relay K2 is connected with one end of a voltage dividing resistor R1, the movable contact of the relay K2 is connected with the normally-closed contact of the relay K1, and the normally-closed contact of the relay K2 is connected with the output end.
3. An over-under-voltage protection circuit according to claim 2, characterized in that: the coil of the relay K1 is connected in parallel with the freewheel diode D1, and the coil of the relay K2 is connected in parallel with the freewheel diode D4.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202223470554.7U CN219268479U (en) | 2022-12-26 | 2022-12-26 | Overvoltage and undervoltage protection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202223470554.7U CN219268479U (en) | 2022-12-26 | 2022-12-26 | Overvoltage and undervoltage protection circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN219268479U true CN219268479U (en) | 2023-06-27 |
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ID=86855816
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202223470554.7U Active CN219268479U (en) | 2022-12-26 | 2022-12-26 | Overvoltage and undervoltage protection circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN219268479U (en) |
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2022
- 2022-12-26 CN CN202223470554.7U patent/CN219268479U/en active Active
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