Single-phase alternating current overcurrent protection circuit

Abstract

The utility model relates to the technical field of circuit protection, in particular to a single-phase alternating current over-current protection circuit, which comprises a current transformer, a voltage sensing element, a driving module and a switching element, and is characterized in that a primary coil of the current transformer and the switching element are mutually connected in series and are connected in a power supply loop of alternating current and a load together; the current transformer is used for inducing current in a power supply loop and generating induced voltage in a secondary coil, the output end of the voltage induction element is connected with the relay, the induction end of the voltage induction element is connected with the secondary coil of the current transformer, and the voltage induction element is used for controlling the driving part to output a driving signal when the induced voltage is larger than a set value; the control end of the switch piece is connected with the driving piece, and the control end of the switch piece is turned off after receiving the driving signal. The power supply is automatically cut off when the current short circuit condition occurs in the circuit, so that the circuit safety is protected, and fire disasters are prevented.

Description

Technical Field

[0001] The present application relates to the field of circuit protection technology, and in particular to a single-phase alternating current overcurrent protection circuit. Background Art

[0002] With the rapid development of modern power electronics technology, the importance of circuit protection technology has become increasingly prominent. In power supply or charging systems, due to various unpredictable factors, such as overload or line short circuit, the current in the main circuit may increase abnormally, causing damage to the circuit system or even causing safety accidents.

[0003] In traditional power supply or charging systems, loads are generally unattended when being charged or used (for example, when using household appliances such as rice cookers and refrigerators, or charging electric vehicles). If the load is too heavy or the line is short-circuited, the current may increase abnormally. If the circuit is not cut off in time, it may cause a fire and property loss. Utility Model Content

[0004] In order to automatically cut off the power supply when a current short circuit occurs in the circuit, thereby protecting the circuit safety and preventing fire, the present application provides a single-phase AC overcurrent protection circuit.

[0005] The present application provides a single-phase AC overcurrent protection circuit, which adopts the following technical solution:

[0006] A single-phase AC overcurrent protection circuit comprises a current transformer, a voltage sensing element, a driving module and a switch element, wherein the primary coil of the current transformer and the switch element are connected in series and connected together in a power supply circuit of the AC current and a load, the current transformer is used to sense the current in the power supply circuit and generate an induced voltage in the secondary coil, the output end of the voltage sensing element is connected to a relay, the induction end of the voltage sensing element is connected to the secondary coil of the current transformer, and is used to control the driving element to output a driving signal when the induced voltage is greater than a set value, the control end of the switch element is connected to the driving element, and the switch element is turned off after receiving the driving signal at its control end.

[0007] By adopting the above technical solution, when the current in the main circuit is too large due to excessive load or line short circuit, the voltage induced on the secondary side of the current transformer increases. At this time, the voltage sensing element controls the driver to output a drive signal, and the switch element is turned off after receiving the drive signal at its control end, thereby automatically cutting off the power supply when a current short circuit occurs in the circuit, thereby protecting the circuit safety and preventing fire.

[0008] Preferably, it also includes a rectifier module for converting AC power into DC power, the driving component includes a relay, pin 1 of the rectifier module is used to connect to the live wire of the AC power, pin 2 of the rectifier module is used to connect to the neutral wire of the AC power, pin 3 of the rectifier module is connected to one end of the relay coil, and pin 4 of the rectifier module is connected to the secondary coil of the current transformer.

[0009] By adopting the above technical solution, the rectifier module converts AC power into DC power to drive the relay coil, wherein the relay is a time-tested electrical switching device with a high operating life and stability, and the rectifier module provides the required DC power for the relay.

[0010] Preferably, the voltage sensing element includes a crystal triode, and also includes a second crystal diode, a second resistor, a third capacitor, a second voltage-stabilizing diode and a sliding rheostat. The anode of the second crystal diode is connected to one end of the secondary coil of the current transformer, the cathode of the second crystal diode is connected to one end of the second resistor, the other end of the second resistor is connected to a fixed end of the sliding rheostat and one end of the third capacitor, the other fixed end of the sliding rheostat is connected to the other end of the secondary coil of the current transformer, the third capacitor is connected in parallel with the sliding rheostat, the active end of the sliding rheostat is connected to the cathode of the second voltage-stabilizing diode, the anode of the second voltage-stabilizing diode is connected to the base of the crystal triode, one end of the relay coil is connected to the collector of the crystal triode, the other end of the relay coil is used to be connected to pin 3 of the rectifier module, the crystal triode is used to be turned on when the induced voltage is greater than the set value, and the relay is electrically attracted when the crystal triode is turned on.

[0011] By adopting the above technical solution, when the current exceeds the set value, the induced voltage generated in the secondary coil of the current transformer is divided by the sliding rheostat and breaks down the second voltage regulator tube. At this time, the base of the transistor is turned on. In addition, the role of the second crystal diode is to play a rectifying function in the circuit to ensure that the signal in the circuit can only flow in a certain direction to ensure the stability of the circuit and correct signal processing. The second resistor is used to limit the flow of current, and the third capacitor helps to store and release charges in the circuit to smooth the changes in the circuit.

[0012] Preferably, the switch element comprises a bidirectional thyristor, a first anode of the bidirectional thyristor is connected to a primary coil of a current transformer, and a second anode of the bidirectional thyristor is connected to a load.

[0013] By adopting the above technical solution, the bidirectional thyristor responds to the voltage control signal very quickly and can be turned on or off within microseconds. This fast response ensures that the overcurrent protection circuit can respond to current abnormalities in a timely manner to protect the load equipment.

[0014] Preferably, the relay also includes a first contact and a second contact, the first contact is closed and the second contact is opened when the relay coil is energized and attracted, the first contact is connected between the collector and the emitter of the transistor, and the second contact is connected between the first anode of the bidirectional thyristor and the control electrode of the bidirectional thyristor.

[0015] By adopting the above technical solution, when the current of the main circuit is too large due to excessive load or line short circuit, the voltage induced on the secondary side of the current transformer increases, which can make the base of the transistor conduct, so that the relay coil is energized and pulled in. At the same time, the first contact is closed and self-locked, and the second contact in the trigger circuit is disconnected, cutting off the trigger power supply of the bidirectional thyristor control electrode, thereby disconnecting the bidirectional thyristor.

[0016] Preferably, it further comprises a third resistor and a fourth capacitor, the third resistor and the fourth capacitor are connected in series with each other, and the fourth capacitor and the third resistor connected in series in sequence are connected between the first anode and the second anode of the bidirectional thyristor.

[0017] By adopting the above technical solution, the third resistor and the fourth capacitor are connected in series between the first anode and the second anode of the bidirectional thyristor (Triac). This connection method can help suppress voltage peaks in the circuit, effectively smooth these peaks, and improve the stability and reliability of the circuit.

[0018] Preferably, it also includes a first capacitor, a second capacitor, a first voltage-stabilizing diode and a first crystal diode, the first capacitor is connected between pin 1 of the rectifier module and the live wire, the second capacitor is connected between pin 3 of the rectifier module and pin 4 of the rectifier module, one end of the first voltage-stabilizing diode is connected to pin 3 of the rectifier module, the other end of the first voltage-stabilizing diode is simultaneously connected to pin 4 of the rectifier module and one end of the secondary coil of the current transformer, the anode of the first crystal diode is connected to the collector of the crystal triode, the cathode of the first crystal diode is connected to pin 3 of the rectifier module, and the first crystal diode is connected in parallel with the relay coil.

[0019] By adopting the above technical solution, the first capacitor and the second capacitor play the role of smoothing the DC voltage at the output end of the rectifier module, reducing the impact of voltage fluctuations and noise, and helping to maintain the stability and reliability of the circuit. The role of the first voltage regulator diode (which may be a Zener diode) is to provide protection against overvoltage. The first crystal diode is usually used in parallel with the relay coil, and its role is to prevent the reverse voltage in the relay coil from damaging the circuit.

[0020] Preferably, it also includes an indicator light, wherein the indicator light anode is connected to pin 3 of the rectifier module, the indicator light cathode is connected to the collector of the transistor, and the indicator light is connected in parallel with the coil of the relay.

[0021] By adopting the above technical solution, when the current in the main circuit is too large due to excessive load or line short circuit, the voltage induced on the secondary side of the current transformer increases, which can make the base of the transistor conductive, so that the relay coil is energized and activated, and the indicator light lights up to show that the line is overcurrent, so that it is easy to intuitively understand whether the circuit is operating normally or whether a fault has occurred.

[0022] Preferably, it also includes a button, which is connected between the first contact and the collector of the transistor.

[0023] By adopting the above technical solution, after the line fault is eliminated, the button is pressed, the relay loses power, its first contact is disconnected, and the second contact is closed and reset, the bidirectional thyristor is triggered and turned on again, and power is supplied to the load again, thereby realizing the reset function.

[0024] In summary, the present application includes at least one of the following beneficial technical effects:

[0025] 1. When the current in the main circuit is too large due to excessive load or line short circuit, the voltage induced on the secondary side of the current transformer increases. At this time, the voltage sensing element controls the driver to output a drive signal, and the switch is turned off after receiving the drive signal at its control end, thereby automatically cutting off the power supply when a current short circuit occurs in the circuit, thereby protecting the circuit safety and preventing fire;

[0026] 2. When the current exceeds the set value, the induced voltage generated in the secondary coil of the current transformer is divided by the sliding rheostat and breaks down the second voltage regulator tube. At this time, the base of the crystal triode is turned on. In addition, the role of the second crystal diode is to play a rectifying function in the circuit, ensuring that the signal in the circuit can only flow in a certain direction to ensure the stability of the circuit and correct signal processing. The second resistor is used to limit the flow of current, and the third capacitor helps to store and release charges in the circuit to smooth the changes of the circuit.

[0027] 3. When the current in the main circuit is too large due to excessive load or short circuit, the voltage induced on the secondary side of the current transformer increases, which can make the base of the transistor conduct, so that the relay coil is energized and activated. At the same time, the first contact closes and self-locks, and the second contact in the trigger circuit is disconnected, cutting off the trigger power supply of the bidirectional thyristor control electrode, thereby disconnecting the bidirectional thyristor. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a circuit schematic diagram of a single-phase AC overcurrent protection circuit according to an embodiment of the present application. DETAILED DESCRIPTION

[0029] The present application is further described in detail below in conjunction with all the accompanying drawings.

[0030] The present application embodiment discloses a single-phase alternating current overcurrent protection circuit. Figure 1 A single-phase AC overcurrent protection circuit includes a rectifier module for converting AC into DC, a current transformer TA, a voltage sensing element, a drive module and a switch.

[0031] The voltage sensing element includes an NPN crystal transistor VT, the driving element includes a relay KA, the relay KA includes a first contact KA1 and a second contact KA2, the first contact KA1 is a normally open contact, and the second contact KA2 is a normally closed contact, the switch element adopts a bidirectional thyristor VS, the rectifier module adopts a rectifier bridge stack DB307S, and also includes a first crystal diode VD1, a second crystal diode VD2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first capacitor C1, a second capacitor C2, a third capacitor C3, a first voltage regulator diode VZ1, a second voltage regulator diode VZ2, a sliding rheostat RP1, an indicator light VL and a button SB, and the indicator light adopts a light-emitting diode.

[0032] The control gate trigger signal of the bidirectional thyristor can be an AC signal or a DC signal. Figure 1 The trigger signal of the G pole of VS is an AC signal, and the strong triggering mode of the same phase is adopted. After the bidirectional thyristor is triggered and turned on, if the DC voltage is applied between the main electrodes T1 and T2, the thyristor will still be turned on when the control electrode voltage is removed; if the voltage between the main electrodes T1 and T2 is an AC voltage, after the control electrode voltage is removed, the bidirectional thyristor will be turned off when the AC passes zero. In the above figure, the AC voltage is applied between the thyristors T2 and T1. When there is no trigger signal at the control electrode, VS will be turned off when the AC passes zero.

[0033] Pin 1 of the rectifier module is used to connect to the live wire of the AC power, pin 2 of the rectifier module is used to connect to the neutral wire of the AC power, pin 3 of the rectifier module, i.e. the positive output, is connected to one end of the relay coil, and pin 4 of the rectifier module, i.e. the negative output, is connected to the secondary coil of the current transformer.

[0034] The neutral line N is connected to pin 2 of the load, one end of the primary coil of the current transformer is connected to the live line L, the first anode of the bidirectional thyristor is connected to the other end of the primary coil of the current transformer, the second anode of the bidirectional thyristor is connected to pin 1 of the load, the third resistor and the fourth capacitor are connected in series with each other, the fourth capacitor and the third resistor connected in series in sequence are connected between the first anode and the second anode of the bidirectional thyristor, and the second contact and the fourth resistor are connected in series with each other between the first anode of the bidirectional thyristor and the control electrode of the bidirectional thyristor.

[0035] The anode of the second crystal diode is connected to one end of the secondary coil of the current transformer, the cathode of the second crystal diode is connected to one end of the second resistor, the other end of the second resistor is connected to a fixed end of the sliding rheostat and one end of the third capacitor, the other fixed end of the sliding rheostat is connected to the other end of the secondary coil of the current transformer, the third capacitor is connected in parallel with the sliding rheostat, the movable end of the sliding rheostat is connected to the cathode of the second voltage-stabilizing diode, the anode of the second voltage-stabilizing diode is connected to the base of the crystal transistor, one end of the relay coil is connected to the collector of the crystal transistor, the first contact and the button are connected in series between the collector and the emitter of the crystal transistor, the other end of the relay coil is used to be connected to pin 3 of the rectifier module, the crystal transistor is used to be turned on when the induced voltage is greater than the set value, and the relay is electrically attracted when the crystal transistor is turned on.

[0036] The first capacitor is connected between pin 1 of the rectifier module and the live wire, the second capacitor is connected between pin 3 of the rectifier module and pin 4 of the rectifier module, one end of the first voltage regulator diode is connected to pin 3 of the rectifier module, the other end of the first voltage regulator diode is simultaneously connected to pin 4 of the rectifier module and one end of the secondary coil of the current transformer, the anode of the first crystal diode is connected to the collector of the crystal triode, the cathode of the first crystal diode is connected to pin 3 of the rectifier module, the first crystal diode is connected in parallel with the relay coil, the anode of the indicator light is connected to the first resistor, the other end of the first resistor is connected to pin 3 of the rectifier module, the cathode of the indicator light is connected to the collector of the crystal triode, and the indicator light is connected in parallel with the coil of the relay.

[0037] The implementation principle of a single-phase AC overcurrent protection circuit in the embodiment of the present application is: when the load is not overloaded or the line is not short-circuited, the voltage induced on the secondary side of the current transformer TA cannot make VT conduct, the relay KA coil must not be electrically attracted, and its contact KA2 does not disconnect the control electrode trigger circuit of the bidirectional thyristor VS. The thyristor VS is triggered to conduct, and AC 220V supplies power to the load normally. When the current of the main circuit is too large due to excessive load or line short circuit, the voltage induced on the secondary side of the current transformer TA is large, which can make the VT base conduct, so that the relay KA coil is electrically attracted, and VL lights up to indicate that the line is overcurrent. At the same time, the contact KA1 is closed and self-locked, the KA2 contact in the trigger circuit is disconnected, the VS control electrode trigger power supply is cut off, the thyristor VS is turned off when the AC passes through zero, and AC220V stops supplying power to the load, which protects the circuit. After the line fault is cleared, press the button SB, KA loses power and its contact KA2 is closed and reset, VS is triggered and turned on again, and power is supplied to the load again.

[0038] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A single-phase AC overcurrent protection circuit, characterized in that: The invention comprises a current transformer, a voltage sensing element, a driving module and a switch element. The primary coil of the current transformer and the switch element are connected in series and connected together in a power supply circuit of an alternating current and a load. The current transformer is used to sense the current in the power supply circuit and generate an induced voltage in the secondary coil. The output end of the voltage sensing element is connected to a relay. The induction end of the voltage sensing element is connected to the secondary coil of the current transformer. The voltage sensing element is used to control the driving element to output a driving signal when the induced voltage is greater than a set value. The control end of the switch element is connected to the driving element, and the switch element is turned off after receiving the driving signal at its control end.

2. A single-phase AC overcurrent protection circuit according to claim 1, characterized in that: It also includes a rectifier module for converting AC power into DC power, the driving component includes a relay, pin 1 of the rectifier module is used to connect to the live wire of the AC power, pin 2 of the rectifier module is used to connect to the neutral wire of the AC power, pin 3 of the rectifier module is connected to one end of the relay coil, and pin 4 of the rectifier module is connected to the secondary coil of the current transformer.

3. A single-phase AC overcurrent protection circuit according to claim 2, characterized in that: The voltage sensing element includes a crystal triode, and also includes a second crystal diode, a second resistor, a third capacitor, a second voltage regulator diode and a sliding rheostat. The anode of the second crystal diode is connected to one end of the secondary coil of the current transformer, the cathode of the second crystal diode is connected to one end of the second resistor, the other end of the second resistor is connected to a fixed end of the sliding rheostat and one end of the third capacitor, the other fixed end of the sliding rheostat is connected to the other end of the secondary coil of the current transformer, the third capacitor is connected in parallel with the sliding rheostat, the active end of the sliding rheostat is connected to the cathode of the second voltage regulator diode, the anode of the second voltage regulator diode is connected to the base of the crystal triode, one end of the relay coil is connected to the collector of the crystal triode, the other end of the relay coil is used to be connected to pin 3 of the rectifier module, the crystal triode is used to be turned on when the induced voltage is greater than the set value, and the relay is electrically attracted when the crystal triode is turned on.

4. A single-phase AC overcurrent protection circuit according to claim 3, characterized in that: The switch element comprises a bidirectional thyristor, a first anode of the bidirectional thyristor is connected to a primary coil of a current transformer, and a second anode of the bidirectional thyristor is connected to a load.

5. A single-phase AC overcurrent protection circuit according to claim 4, characterized in that: The relay also includes a first contact and a second contact. When the relay coil is energized and attracted, the first contact is closed and the second contact is opened. The first contact is connected between the collector and the emitter of the transistor, and the second contact is connected between the first anode of the bidirectional thyristor and the control electrode of the bidirectional thyristor.

6. A single-phase AC overcurrent protection circuit according to claim 4, characterized in that: It also includes a third resistor and a fourth capacitor, which are connected in series with each other, and the fourth capacitor and the third resistor connected in series in sequence are connected between the first anode and the second anode of the bidirectional thyristor.

7. A single-phase AC overcurrent protection circuit according to claim 3, characterized in that: It also includes a first capacitor, a second capacitor, a first voltage-stabilizing diode and a first crystal diode. The first capacitor is connected between pin 1 of the rectifier module and the live wire, the second capacitor is connected between pin 3 of the rectifier module and pin 4 of the rectifier module, one end of the first voltage-stabilizing diode is connected to pin 3 of the rectifier module, the other end of the first voltage-stabilizing diode is simultaneously connected to pin 4 of the rectifier module and one end of the secondary coil of the current transformer, the anode of the first crystal diode is connected to the collector of the crystal triode, the cathode of the first crystal diode is connected to pin 3 of the rectifier module, and the first crystal diode is connected in parallel with the relay coil.

8. A single-phase AC overcurrent protection circuit according to claim 3, characterized in that: It also includes an indicator light, wherein the indicator light anode is connected to the 3rd pin of the rectifier module, the indicator light cathode is connected to the collector of the transistor, and the indicator light is connected in parallel with the coil of the relay.

9. A single-phase AC overcurrent protection circuit according to claim 5, characterized in that: The utility model also comprises a button, wherein the button is connected between the first contact and the collector of the transistor.

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