CN217115611U - Overvoltage protection circuit and electrical equipment - Google Patents
Overvoltage protection circuit and electrical equipment Download PDFInfo
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- CN217115611U CN217115611U CN202220404558.6U CN202220404558U CN217115611U CN 217115611 U CN217115611 U CN 217115611U CN 202220404558 U CN202220404558 U CN 202220404558U CN 217115611 U CN217115611 U CN 217115611U
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Abstract
The application discloses overvoltage crowbar and electrical equipment, overvoltage crowbar, first switch branch road and second switch branch road are triggered including the overvoltage crowbar. The trigger branch is respectively connected with the input power supply and the first switch branch, the first switch branch is respectively connected with the input power supply and the second switch branch, and the second switch branch is connected with the input power supply. The triggering branch circuit is configured to be triggered to be conducted when the voltage of the input power supply is greater than a first preset voltage threshold value, so as to output a low-level signal to the first end of the first switching branch circuit. The first switching leg is configured to open in response to a low level signal to disconnect the input power source from the first end of the second switching leg. The second switching leg is configured to open when the connection between the first end of the second switching leg and the input power source is broken to disconnect the input power source from the first output terminal. Through the mode, the cost can be reduced while the overvoltage protection function is realized.
Description
Technical Field
The application relates to the technical field of electronic circuits, in particular to an overvoltage protection circuit and electrical equipment.
Background
For electrical equipment, when a power supply of the electrical equipment is subjected to external interference (such as high-voltage static electricity, lightning strike and the like), a condition of power supply voltage rise easily occurs, which easily causes damage to some electrical components in the electrical equipment, thereby adversely affecting stable operation of the electrical equipment.
In view of the situation, a specific power supply chip is required to be adopted at present so as to realize overvoltage protection when the power supply voltage is too high.
However, the cost of the power supply chip is high, which results in high cost of the whole electrical equipment.
SUMMERY OF THE UTILITY MODEL
The application aims at providing an overvoltage protection circuit and electrical equipment, and cost can be reduced while the overvoltage protection function is achieved.
To achieve the above object, in a first aspect, the present application provides an overvoltage protection circuit comprising:
the trigger branch circuit, the first switch branch circuit and the second switch branch circuit;
the first end of the trigger branch is connected with the first end of the input power supply, the second end of the trigger branch is connected with the first end of the first switch branch, the second end of the first switch branch is connected with the first end of the input power supply, the third end of the first switch branch is connected with the first end of the second switch branch, the second end of the second switch branch is respectively connected with the third end of the trigger branch and the second end of the input power supply, the third end of the second switch branch is a first output end, and the fourth end of the second switch branch is connected with the first end of the input power supply;
the triggering branch circuit is configured to be triggered to be conducted when the voltage of the input power supply is greater than a first preset voltage threshold value so as to output a low-level signal to the first end of the first switching branch circuit;
the first switching leg is configured to open in response to the low level signal to disconnect the connection between the first terminal of the input power source and the first terminal of the second switching leg;
the second switching leg is configured to open when the connection between the first end of the second switching leg and the first end of the input power source is broken to disconnect the first end of the input power source from the first output terminal.
In an optional manner, the overvoltage protection circuit further includes a voltage reduction branch, a rectification branch, and a voltage stabilization branch;
the first end of the voltage reduction branch circuit is connected with the first end of the input power supply, the second end of the voltage reduction branch circuit is connected with the first end of the rectification branch circuit, the second end of the rectification branch circuit is connected with the first end of the trigger branch circuit, the third end of the rectification branch circuit is respectively connected with the first end of the voltage stabilization branch circuit and the second end of the first switch branch circuit, the fourth end of the trigger branch circuit is connected with the fourth end of the first switch branch circuit, and the second end of the voltage stabilization branch circuit is connected with the second end of the input power supply;
the voltage reduction branch is configured to reduce a voltage of the input power supply and output a first voltage;
the rectifying branch is configured to rectify the first voltage to output a second voltage at a second end of the rectifying branch and output a third voltage at a third end of the rectifying branch;
the triggering branch circuit is further configured to open when the second voltage is not greater than a second preset voltage threshold value, so as to output a high-level signal to the fourth terminal of the first switching branch circuit according to the second voltage, wherein the second voltage is not greater than the second preset voltage threshold value when the input power supply is not greater than the first preset voltage threshold value;
the voltage stabilizing branch is configured to stabilize the third voltage and output a fourth voltage at a first end of the voltage stabilizing branch;
the first switching branch is further configured to conduct in response to the high level signal to establish a connection between the first end of the voltage stabilizing branch and the first end of the second switching branch;
the second switching branch is further configured to conduct in response to the fourth voltage to establish a connection between the first output terminal and the first terminal of the input power supply when the first terminal of the second switching branch is connected with the first terminal of the voltage stabilization branch.
In an optional mode, the voltage reduction branch comprises a first capacitor and a first resistor;
the first capacitor is connected with the first resistor in parallel, a first end of the first capacitor is connected with a first end of the input power supply, and a second end of the first capacitor is connected with a first end of the rectifying branch.
In an alternative mode, the rectifying branch comprises a first diode and a second diode;
the anode of the first diode is connected with the anode of the second diode and the second end of the voltage reduction branch circuit respectively, the cathode of the first diode is connected with the first end of the voltage stabilization branch circuit, and the cathode of the second diode is connected with the first end of the trigger branch circuit.
In an optional mode, the trigger branch comprises a second resistor, a second capacitor and an adjustable voltage diode;
the first end of the second resistor is connected with the fourth end of the first switch branch circuit, the second end of the second resistor is respectively connected with the first end of the second capacitor and the reference end of the adjustable voltage diode, the anode of the adjustable voltage diode is grounded with the second end of the second capacitor, and the cathode of the adjustable voltage diode is connected with the first end of the first switch branch circuit
In an optional manner, the trigger branch includes a third resistor, a fourth resistor, and a third capacitor;
the first end of the third resistor is connected with the second end of the rectifying branch circuit, the second end of the third resistor is connected with the first end of the fourth resistor, the second end of the fourth resistor is grounded, and the third capacitor is connected with the fourth resistor in parallel.
In an optional mode, the voltage stabilizing branch comprises a first voltage stabilizing diode and a fourth capacitor;
the anode of the first voltage-stabilizing diode and the first end of the fourth capacitor are both grounded, and the cathode of the first voltage-stabilizing diode is respectively connected with the second end of the fourth capacitor and the third end of the rectifying branch.
In an optional mode, the first switching branch includes a fifth resistor, a sixth resistor, a seventh resistor, and a first switching tube;
the first end of the fifth resistor is connected with the fourth end of the trigger branch, the second end of the fifth resistor is respectively connected with the second end of the trigger branch and the first end of the sixth resistor, the second end of the sixth resistor is respectively connected with the first end of the seventh resistor and the first end of the first switch tube, the second end of the seventh resistor is respectively connected with the third end of the first switch tube, the third end of the rectifying branch and the first end of the voltage stabilizing branch, and the second end of the first switch tube is connected with the first end of the second switch branch.
In an alternative mode, the second switching branch comprises a relay and a third diode, and the relay comprises a coil and a pair of normally open contacts;
the first end of the coil is respectively connected with the cathode of the third diode and the third end of the first switch branch circuit, the second end of the coil and the anode of the third diode are both grounded, the first contact of the pair of normally open contacts is connected with the first end of the input power supply, and the second contact of the pair of normally open contacts is the first output end.
In a second aspect, the present application provides an electrical device comprising an overvoltage protection circuit as described above.
The beneficial effect of this application is: the application provides an overvoltage protection circuit, including triggering branch road, first switch branch road and second switch branch road. The trigger branch is respectively connected with the input power supply and the first switch branch, the first switch branch is respectively connected with the input power supply and the second switch branch, and the second switch branch is connected with the input power supply. When the overvoltage phenomenon occurs, the voltage of the input power supply is larger than a first preset voltage threshold value. At this time, the triggering branch is triggered to be conducted, and a low level signal is output to the first end of the first switching branch, so that the first switching branch is disconnected. And when the first switch branch is disconnected, the connection between the input power supply and the first end of the second switch branch is disconnected, and the second switch branch is also disconnected. And when the second switch branch is disconnected, the connection between the first end of the input power supply and the first output end is disconnected. Therefore, even if the first output end is connected with the electric load, the electric load cannot obtain the working voltage due to the fact that the connection between the first end of the input power supply and the first output end is disconnected, namely when an overvoltage phenomenon occurs, the power supply source of the electric load is timely disconnected, and the overvoltage protection function is achieved. Meanwhile, a specific power supply chip is not needed to be adopted as in the related technology, and cost reduction is facilitated.
Drawings
One or more embodiments are illustrated by way of example in the accompanying drawings, which correspond to the figures in which like reference numerals refer to similar elements and which are not to scale unless otherwise specified.
Fig. 1 is a schematic structural diagram of an overvoltage protection circuit provided in an embodiment of the present application;
fig. 2 is a schematic structural diagram of an overvoltage protection circuit according to another embodiment of the present application;
fig. 3 is a schematic circuit structure diagram of an overvoltage protection circuit according to an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application.
Referring to fig. 1, fig. 1 is a schematic structural diagram of an overvoltage protection circuit according to an embodiment of the present disclosure. As shown in fig. 1, the overvoltage protection circuit 100 includes a first switching branch 10, a second switching branch 20 and a triggering branch 30. The first end of the trigger branch 30 is connected to the first end of the input power supply 200, the second end of the trigger branch 30 is connected to the first end of the first switch branch 10, the second end of the first switch branch 10 is connected to the first end of the input power supply 200, the third end of the first switch branch 10 is connected to the first end of the second switch branch 20, the second end of the second switch branch 20 is connected to the third end of the trigger branch 30 and the second end of the input power supply 200, the third end of the second switch branch 20 is the first output end OUT1, and the fourth end of the second switch branch 20 is connected to the first end of the input power supply 200.
In one embodiment, the input power source 200 may be 110v, 220v (i.e., mains), or the like.
Specifically, the triggering branch 30 is configured to be triggered to be turned on when the voltage of the input power source 200 is greater than a first preset voltage threshold, so as to output a low level signal to the first end of the first switching branch 10. The first switching branch 10 is configured to be opened in response to a low level signal to disconnect the first terminal of the input power source 200 from the first terminal of the second switching branch 20. The second switching leg 20 is configured to open when the connection between the first terminal of the second switching leg 20 and the first terminal of the input power supply 200 is broken to break the connection between the first terminal of the input power supply 200 and the first output terminal OUT 1.
The first preset voltage threshold may be set according to an actual application, and this is not specifically limited in the embodiment of the present application. For example, in an embodiment, under a normal condition, the input power 200 is 220v, and the first preset voltage threshold may be set to 220v, so that when the voltage of the input power 200 is greater than 220v, it is considered that an overvoltage phenomenon occurs, and the overvoltage protection circuit 100 can implement an overvoltage protection function.
In practical applications, when the overvoltage occurs, the voltage of the input power 200 is greater than the first predetermined voltage threshold. At this time, the triggering branch 30 is triggered to be turned on, and outputs a low level signal to the first end of the first switching branch 10. Then, the first switching branch 10 is disconnected by receiving the low level signal, and the connection between the first terminal of the input power source 200 and the first terminal of the second switching branch 20 is disconnected. The second switching leg 20 is disconnected due to the disconnection between its first terminal and the first terminal of the input power source 200. And the connection between the first terminal of the input power source 200 and the first output terminal OUT1 is also broken due to the opening of the second switching leg 20. Therefore, in this case, even if the first output terminal OUT1 is connected to the electric load, the electric load cannot obtain the operating voltage. That is, when an overvoltage occurs, the overvoltage protection circuit 100 can disconnect the first terminal of the input power source 200 from the first output terminal OUT1, and disconnect the power source of the electrical load, so as to implement an overvoltage protection function. Meanwhile, a specific power supply chip is not needed to be adopted as in the related technology, and cost reduction is facilitated.
In one embodiment, as shown in fig. 2, the overvoltage protection circuit 100 further includes a voltage-reducing branch 40, a rectifying branch 50 and a voltage-stabilizing branch 60. Wherein, the first end of step-down branch road 40 is connected with the first end of input power 200, the second end of step-down branch road 40 is connected with the first end of rectification branch road 50, the second end of rectification branch road 50 is connected with the first end of triggering branch road 30, the third end of rectification branch road 50 is connected with the first end of steady voltage branch road 60 and the second end of first switch branch road 10 respectively, the fourth end of triggering branch road 30 is connected with the fourth end of first switch branch road 10, the second end of steady voltage branch road 60 is connected with the second end of input power 200.
Specifically, the voltage dropping branch 40 is configured to drop a voltage input to the power supply 200 and output a first voltage. The rectifying branch 50 is configured to rectify the first voltage to output a second voltage at a second terminal of the rectifying branch 50, and output a third voltage at a third terminal of the rectifying branch 50. The triggering branch circuit 30 is further configured to open when a second voltage is not greater than a second preset voltage threshold, so as to output a high level signal to the fourth terminal of the first switching branch circuit 10 according to the second voltage, wherein the second voltage is not greater than the second preset voltage threshold when the input power is not greater than the first preset voltage threshold. The voltage stabilizing branch 60 is configured to stabilize the third voltage and output a fourth voltage at a first end of the voltage stabilizing branch 60. The first switching branch 10 is further configured to conduct in response to a high level signal to establish a connection between the first terminal of the voltage regulation branch 70 and the first terminal of the second switching branch 20. The second switching leg 20 is further configured to conduct in response to the fourth voltage to establish a connection between the first output terminal OUT1 and the first terminal of the input power source 200 when the first terminal of the second switching leg 20 is connected with the first terminal of the voltage stabilizing leg 70.
The second preset voltage threshold may be set according to an actual application, which is not specifically limited in the embodiment of the present application, but the second preset voltage threshold should satisfy that when the voltage of the input power source 200 is greater than the first preset voltage threshold, the second voltage is greater than the second preset voltage threshold, and when the voltage of the input power source 200 is not greater than the first preset voltage threshold, the second voltage is not greater than the second preset voltage threshold.
In practical applications, when the overvoltage occurs, the voltage of the input power 200 is greater than the first predetermined voltage threshold. At this time, the triggering branch 30 is triggered to be turned on, and outputs a low level signal to the first end of the first switching branch 10. Then, the first switching branch 10 is disconnected due to the first terminal thereof receiving the low level signal, and the connection between the first terminal of the input power source 200 and the first terminal of the second switching branch 20 is disconnected. The second switching leg 20 is also open. And the connection between the first terminal of the input power source 200 and the first output terminal OUT1 is also broken due to the disconnection of the second switching leg 20. Therefore, when an overvoltage phenomenon occurs, the overvoltage protection circuit 100 can disconnect the first terminal of the input power supply 200 from the first output terminal OUT1, and disconnect the power supply source of the electric load, so that an overvoltage protection function is realized. Meanwhile, a specific power supply chip is not needed to be adopted as in the related technology, and cost reduction is facilitated.
Under normal conditions, no overvoltage occurs, and when the voltage of the input power 200 is greater than the first preset voltage threshold, the triggering branch 30 is turned off and outputs a high level signal to the fourth terminal of the first switching branch 10, so that the first switching branch 10 is turned on. Meanwhile, the voltage stabilizing branch 60 outputs the fourth voltage at the first terminal thereof after stabilizing the third voltage output from the rectifying branch 50. Then, after the first switching branch 10 is turned on, the first end of the voltage stabilizing branch 70 is communicated with the first end of the second switching branch 20, and the voltage of the first end of the second switching branch 20 is also the fourth voltage. In turn, the second switching leg 20 is turned on in response to the fourth voltage. Then, after the second switching branch 20 is turned on, the first terminal of the input power source 200 is connected to the first output terminal OUT1, and if the first output terminal OUT1 is connected to the electric load, the electric load can be normally powered.
Fig. 3 illustrates an example of a structure of the first switching branch 10, and as shown in fig. 2, the first switching branch 10 includes a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, and a first switching tube Q1. The first end of the fifth resistor R5 is connected to the fourth end of the trigger branch 30, the second end of the fifth resistor R5 is connected to the second end of the trigger branch 30 and the first end of the sixth resistor R6, the second end of the sixth resistor R6 is connected to the first end of the seventh resistor R7 and the first end of the first switch Q1, the second end of the seventh resistor R7 is connected to the third end of the first switch Q1, the third end of the rectifying branch 50 and the first end of the voltage stabilizing branch 60, and the second end of the first switch Q1 is connected to the first end of the second switch branch 20.
In this embodiment, the first switch transistor Q1 is an NMOS transistor for example (hereinafter referred to as NMOS transistor). The first end of the first switch tube Q1 is a gate of the NMOS tube, the second end of the first switch tube Q1 is a source of the NMOS tube, and the third end of the first switch tube Q1 is a drain of the NMOS tube.
Besides, in other embodiments, the first switching tube Q1 may also be a P-type metal oxide semiconductor field effect transistor, and the first switching tube Q1 may also be at least one of a triode, an insulated gate bipolar transistor, an integrated gate commutated thyristor, a gate breakable thyristor, a junction gate field effect transistor, a MOS controlled thyristor, a gallium nitride-based power device, a silicon carbide-based power device, a silicon controlled thyristor, and a signal relay.
In this embodiment, when the triggering branch 30 is turned on, the first terminal of the first switch transistor Q1 is grounded AGND, the first terminal of the first switch transistor Q1 is forced to be pulled low, and the first switch transistor Q1 is turned off. At this time, the first switching tube Q1 is turned off upon receiving the low level signal corresponding to the low level signal being output when the trigger branch 30 is turned on.
When the trigger branch 30 is turned off, a high level signal is outputted according to the second voltage, and the high level signal is inputted to the first end of the first switch transistor Q1 through the fifth resistor R5 and the sixth resistor R6, so that the first switch transistor Q1 is turned on. At this time, the first switching tube Q1 is turned off when receiving the high level signal corresponding to the high level signal outputted when the trigger branch 30 is turned off.
Fig. 3 also illustrates an example of the structure of the second switching branch 20, and as shown in fig. 3, the second switching branch 20 includes a relay KA and a third diode D3, and the relay KA includes a coil KM and a pair of normally open contacts S1. The first end of the coil KM is connected to the cathode of the third diode D3 and the third end of the first switch branch 10, the second end of the coil KM and the anode of the third diode D3 are both grounded AGND, the first contact of the pair of normally open contacts S1 is connected to the first end of the input power source 200, and the second contact of the pair of normally open contacts S1 is the first output end OUT 1.
In this embodiment, the magnetic field generated by the induced current will permanently hinder the original magnetic field from changing according to the law of electromagnetic induction. That is, when the coil KM is powered off, the induced current and voltage are in the same direction as the original current and voltage. Therefore, by connecting the third diode D3 in parallel with the coil KM, the unidirectional conduction characteristic of the third diode D3 can be utilized, and when the coil KM is suddenly powered off, the third diode D3 obtains a forward voltage to conduct, and plays a role of continuing the current in the coil KM. In addition, the third diode D3 is always in a reverse cut-off state in the process of electrifying the coil KM, and no electric energy is consumed.
Meanwhile, when the first end of the coil KM is connected to the fourth voltage, the coil KM is powered on, the pair of normally open contacts S1 is closed, the first end of the input power source 200 is connected to the first output end OUT1, and the electrical load connected to the first input end OUT1 is also powered on. When the first end of the coil KM is not connected to the fourth voltage, the coil KM is powered off, the pair of normally open contacts S1 is opened, the connection between the first output end OUT1 and the first end of the input power source 200 is broken, and the electrical load connected to the first input end OUT1 is also powered off.
Fig. 3 also illustrates an example of a structure of the trigger branch 30, and as shown in fig. 3, the trigger branch 30 includes a second resistor R2, a second capacitor C2, and an adjustable voltage diode U1. A first end of the second resistor R2 is connected to the fourth end of the first switching branch 10, a second end of the second resistor R2 is connected to a first end of the second capacitor C2 and a reference end of the adjustable voltage diode U1, an anode of the adjustable voltage diode U1 and a second end of the second capacitor C2 are both grounded AGND, and a cathode of the adjustable voltage diode U1 is connected to the first end of the first switching branch 10.
In this embodiment, the fourth resistor R4 is a current limiting resistor, and the fourth capacitor C4 is a filter capacitor. After power-up, the adjustable voltage diode U1 internally generates a reference voltage that varies with the voltage of its connected reference terminal. When the voltage at its reference terminal becomes larger than its internal reference voltage, the adjustable voltage diode U1 conducts from its anode to ground to its cathode. When the voltage at its reference terminal becomes small and smaller than its internal reference voltage, the adjustable voltage diode U1 is not conducted between its anode and cathode. In one embodiment, the adjustable voltage diode U1 can be a three-terminal adjustable shunt reference source of the type LM431, where the reference voltage between the anode of the LM431 and the reference terminal is constant at 2.5 v.
In one embodiment, the triggering branch 30 further includes a third resistor R3, a fourth resistor R4, and a third capacitor C3. The first end of the third resistor R3 is connected to the second end of the rectifying branch 50, the second end of the third resistor R3 is connected to the first end of the fourth resistor R4, the second end of the fourth resistor R4 is grounded AGND, and the third capacitor C3 is connected in parallel to the fourth resistor R4.
The third capacitor C3 is a filter capacitor or a charging capacitor. The third resistor R3 and the fourth resistor R4 are used for dividing the second voltage output by the rectifying branch 50, and the divided voltage of the third resistor R3 is used as the voltage input to the reference terminal of the adjustable voltage diode U1.
Fig. 3 also illustrates an example of a structure of the voltage-reducing branch 40, and as shown in fig. 3, the voltage-reducing branch 40 includes a first capacitor C1 and a first resistor R1. The first capacitor C1 is connected in parallel with the first resistor R1, and a first end of the first capacitor C1 is connected to a first end of the input power source 200, and a second end of the first capacitor C1 is connected to a first end of the rectifying branch 50.
In this embodiment, the capacitance generated by the ac signal of a certain frequency of the first capacitor C1 can be used to limit the maximum operating current for the purpose of voltage reduction. The magnitude of the current passing through the voltage-reducing branch 40 depends on the magnitude of the first capacitor C1. The first resistor R1 is used as a bleeder resistor to quickly dissipate the energy stored in the first capacitor C1 and to reduce the voltage to a safe value after the overvoltage protection circuit 100 is disconnected from the input power source 200.
Fig. 3 also illustrates an example of a structure of the rectifying branch 50, and as shown in fig. 3, the rectifying branch 50 includes a first diode D1 and a second diode D2. An anode of the first diode D1 is connected to an anode of the second diode D2 and a second end of the voltage-decreasing branch 40, a cathode of the first diode D1 is connected to a first end of the voltage-stabilizing branch 60, and a cathode of the second diode D2 is connected to a first end of the triggering branch 30.
In this embodiment, the rectification of the input power 200 can be achieved by utilizing the unidirectional conduction characteristics of the first diode D1 and the second diode D2. In one embodiment, the input power source 200 is a commercial power source, and the alternating current in the commercial power source is supplied in a sine wave form, specifically, a positive half-wave form is provided above the abscissa, a negative half-wave form is provided below the abscissa, and the two waveforms form a complete frequency waveform. Due to the unidirectional conduction characteristic of the diode, the diode turns on when the anode voltage of the diode D1 is greater than the cathode voltage, and turns off if the cathode voltage is greater than the anode voltage. Therefore, half the mains waveform can be used to power the system: in the case of the positive half-wave of the mains supply, the anode voltage of the first diode D1 (or the second diode D2) is greater than the cathode, the first diode D1 (or the second diode D2) is turned on, and the cathode of the first diode D1 (or the second diode D2) outputs a forward voltage; on the contrary, the first diode D1 (or the second diode D2) is turned off, and the system stops operating.
One configuration of the voltage regulation branch 60 is also illustrated in fig. 3, and as shown in fig. 3, the voltage regulation branch 60 includes a first voltage regulation diode DW1 and a third capacitor C3. An anode of the first zener diode DW1 and the first end of the third capacitor C3 are both grounded AGND, and a cathode of the first zener diode DW1 is respectively connected to the second end of the third capacitor C3 and the third end of the rectifying branch 50.
In this embodiment, the third capacitor C3 is a filter capacitor or a charging capacitor. When the reverse voltage of the first zener diode DW1 approaches a critical value of the reverse voltage, the reverse current increases abruptly, i.e., the first zener diode DW1 is broken down. At this critical breakdown point, the reverse resistance of the first zener diode DW1 abruptly drops to a very small value. At this time, although the current varies in a wide range, the voltage across the first zener diode DW1 is substantially stabilized around the breakdown voltage, thereby implementing the voltage stabilization function of the first zener diode DW 1.
In an embodiment, the overvoltage protection circuit 100 further includes an eighth resistor R8 and a first light emitting diode LE 1. A first end of the eighth resistor R8 is connected to the third end of the first switching tube Q1, a second end of the eighth resistor R8 is connected to an anode of the first light emitting diode LE1, and a cathode of the first light emitting diode LE1 is grounded AGND.
Specifically, when the first switch tube Q1 is turned on, the first end of the eighth resistor R8 is connected to the fifth voltage, and the first light emitting diode LE1 is turned on, whereas when the first switch tube Q1 is turned off, the first light emitting diode LE1 is turned off. It can be seen that, when the first light emitting diode LE1 is turned on, corresponding to a normal operation condition, when the first light emitting diode LE1 is turned off, an overvoltage phenomenon occurs, that is, whether the overvoltage phenomenon occurs can be determined by the on or off state of the first light emitting diode LE 1.
In one embodiment, the overvoltage protection circuit 100 further includes a fourth diode D4, wherein the cathode of the fourth diode D4 is connected to the cathode of the second diode D2, and the cathode of the fourth diode D4 is grounded AGND.
In this embodiment, the fourth diode D4 is used to prevent power from flowing backward through ground AGND to the circuit connected to the cathode of the fourth diode D4, avoiding a circuit loop with a bad condition.
The operating principle of the circuit arrangement shown in fig. 3 is explained below.
Under normal conditions, the second voltage output by the voltage stabilizing branch 50 is not greater than the second preset voltage threshold, the voltage of the reference terminal of the adjustable voltage diode U1 is less than the reference voltage thereof, and the anode and the cathode of the adjustable voltage diode U1 are not conducted. The first terminal of the first switch Q1 is turned on by the input of the high level signal. After going through the step-down of the step-down branch 40, the rectification of the first diode D1, and the voltage stabilization of the first zener diode DW1, the input power 200 obtains a fourth voltage at the cathode of the first zener diode DW1, and the fourth voltage is input to the first end of the eighth resistor R8 and the first end of the coil KM respectively after passing through the first switching tube Q1, so that the first light emitting diode LE1 is lit, and the coil KM is powered. Then, the pair of normally open contacts S1 is turned on, the first output terminal OUT1 is connected to the first terminal of the input power source 200, and the electrical load connected to the first output terminal OUT1 is also powered.
When the overvoltage occurs, the second voltage is greater than the second preset voltage threshold, the voltage of the reference terminal of the adjustable voltage diode U1 is greater than the reference voltage thereof, and the anode and the cathode of the adjustable voltage diode U1 are conducted. The first terminal of the first switch Q1 is grounded AGND, and the first switch Q1 is turned off. Although the input power source 200 obtains the fourth voltage at the cathode of the first zener diode DW1 after the step-down of the step-down branch 40, the rectification of the first diode D1 and the voltage stabilization of the first zener diode DW1, since the first switching tube Q1 is disconnected, the connection between the first light emitting diode LE1 and the coil KM is disconnected, the first light emitting diode LE1 and the coil KM are both de-energized, the first light emitting diode LE1 is extinguished, and the coil KM is de-energized. Then, the pair of normally open contacts S1 is opened, the connection between the first output terminal OUT1 and the first end of the input power supply 200 is disconnected, and the electrical load connected to the first output terminal OUT1 is also powered off, so that when an overvoltage phenomenon occurs, the power supply of the electrical load is timely disconnected to protect the electrical load, that is, an overvoltage protection function is realized. Meanwhile, a power supply chip having characteristics as in the related art is not employed, thereby reducing the cost.
The embodiment of the application further provides electrical equipment which comprises the overvoltage protection circuit in any embodiment of the application.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; within the context of the present application, where technical features in the above embodiments or in different embodiments can also be combined, the steps can be implemented in any order and there are many other variations of the different aspects of the present application as described above, which are not provided in detail for the sake of brevity; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present application.
Claims (10)
1. An overvoltage protection circuit, comprising:
the trigger branch circuit, the first switch branch circuit and the second switch branch circuit;
the first end of the trigger branch is connected with the first end of an input power supply, the second end of the trigger branch is connected with the first end of the first switch branch, the second end of the first switch branch is connected with the first end of the input power supply, the third end of the first switch branch is connected with the first end of the second switch branch, the second end of the second switch branch is respectively connected with the third end of the trigger branch and the second end of the input power supply, the third end of the second switch branch is a first output end, and the fourth end of the second switch branch is connected with the first end of the input power supply;
the triggering branch circuit is configured to be triggered to be conducted when the voltage of the input power supply is greater than a first preset voltage threshold value so as to output a low-level signal to the first end of the first switching branch circuit;
the first switching leg is configured to open in response to the low level signal to disconnect the connection between the first terminal of the input power source and the first terminal of the second switching leg;
the second switching leg is configured to open when the connection between the first end of the second switching leg and the first end of the input power source is broken to disconnect the first end of the input power source from the first output terminal.
2. The overvoltage protection circuit of claim 1, further comprising a voltage reduction branch, a rectification branch, and a voltage regulation branch;
the first end of the voltage reduction branch circuit is connected with the first end of the input power supply, the second end of the voltage reduction branch circuit is connected with the first end of the rectification branch circuit, the second end of the rectification branch circuit is connected with the first end of the trigger branch circuit, the third end of the rectification branch circuit is respectively connected with the first end of the voltage stabilization branch circuit and the second end of the first switch branch circuit, the fourth end of the trigger branch circuit is connected with the fourth end of the first switch branch circuit, and the second end of the voltage stabilization branch circuit is connected with the second end of the input power supply;
the voltage reduction branch is configured to reduce a voltage of the input power supply and output a first voltage;
the rectifying branch is configured to rectify the first voltage to output a second voltage at a second end of the rectifying branch and output a third voltage at a third end of the rectifying branch;
the triggering branch circuit is further configured to open when the second voltage is not greater than a second preset voltage threshold value, so as to output a high-level signal to the fourth terminal of the first switching branch circuit according to the second voltage, wherein the second voltage is not greater than the second preset voltage threshold value when the input power supply is not greater than the first preset voltage threshold value;
the voltage stabilizing branch is configured to stabilize the third voltage and output a fourth voltage at a first end of the voltage stabilizing branch;
the first switching branch is further configured to conduct in response to the high level signal to establish a connection between the first end of the voltage stabilizing branch and the first end of the second switching branch;
the second switching branch is further configured to conduct in response to the fourth voltage to establish a connection between the first output terminal and the first terminal of the input power supply when the first terminal of the second switching branch is connected with the first terminal of the voltage stabilization branch.
3. The overvoltage protection circuit of claim 2, wherein the voltage dropping branch comprises a first capacitor and a first resistor;
the first capacitor is connected with the first resistor in parallel, a first end of the first capacitor is connected with a first end of the input power supply, and a second end of the first capacitor is connected with a first end of the rectifying branch.
4. The overvoltage protection circuit of claim 2, wherein the rectifying branch comprises a first diode and a second diode;
the anode of the first diode is connected with the anode of the second diode and the second end of the voltage reduction branch circuit respectively, the cathode of the first diode is connected with the first end of the voltage stabilization branch circuit, and the cathode of the second diode is connected with the first end of the trigger branch circuit.
5. The overvoltage protection circuit of claim 2, wherein the trigger branch comprises a second resistor, a second capacitor and an adjustable voltage diode;
the first end of the second resistor is connected with the fourth end of the first switch branch circuit, the second end of the second resistor is respectively connected with the first end of the second capacitor and the reference end of the adjustable voltage diode, the anode of the adjustable voltage diode is grounded with the second end of the second capacitor, and the cathode of the adjustable voltage diode is connected with the first end of the first switch branch circuit.
6. The overvoltage protection circuit of claim 5, wherein the trigger branch further comprises a third resistor, a fourth resistor and a third capacitor;
the first end of the third resistor is connected with the second end of the rectifying branch circuit, the second end of the third resistor is connected with the first end of the fourth resistor, the second end of the fourth resistor is grounded, and the third capacitor is connected with the fourth resistor in parallel.
7. The overvoltage protection circuit of claim 2, wherein the voltage regulation branch comprises a first voltage regulation diode and a fourth capacitor;
the anode of the first voltage-stabilizing diode and the first end of the fourth capacitor are both grounded, and the cathode of the first voltage-stabilizing diode is respectively connected with the second end of the fourth capacitor and the third end of the rectifying branch.
8. The overvoltage protection circuit of claim 1, wherein the first switching leg comprises a fifth resistor, a sixth resistor, a seventh resistor and a first switching tube;
the first end of the fifth resistor is connected with the fourth end of the trigger branch, the second end of the fifth resistor is connected with the second end of the trigger branch and the first end of the sixth resistor, the second end of the sixth resistor is connected with the first end of the seventh resistor and the first end of the first switch tube, the second end of the seventh resistor is connected with the third end of the first switch tube, and the second end of the first switch tube is connected with the first end of the second switch branch.
9. The overvoltage protection circuit of claim 1, wherein the second switching leg comprises a relay and a third diode, the relay comprising a coil and a pair of normally open contacts;
the first end of the coil is respectively connected with the cathode of the third diode and the third end of the first switch branch circuit, the second end of the coil and the anode of the third diode are both grounded, the first contact of the pair of normally open contacts is connected with the first end of the input power supply, and the second contact of the pair of normally open contacts is the first output end.
10. An electrical apparatus, characterized in that it comprises an overvoltage protection circuit according to any one of claims 1 to 9.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202220404558.6U CN217115611U (en) | 2022-02-25 | 2022-02-25 | Overvoltage protection circuit and electrical equipment |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202220404558.6U CN217115611U (en) | 2022-02-25 | 2022-02-25 | Overvoltage protection circuit and electrical equipment |
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| CN217115611U true CN217115611U (en) | 2022-08-02 |
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| CN202220404558.6U Active CN217115611U (en) | 2022-02-25 | 2022-02-25 | Overvoltage protection circuit and electrical equipment |
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