A simple current and voltage limiting protection switch circuit

Abstract

The utility model discloses a simple and easy current -limiting voltage -limiting protection switch circuit, PNP output circuit includes first NPN pipe, first PNP pipe, PNP voltage limiting module and PNP current -limiting module, and the base of first NPN pipe connects input, and the emitter connects ground, and the collector connects the base of first PNP pipe, and the emitter of first PNP pipe connects PNP current -limiting module, and the collector connects switch output signal end, and PNP voltage limiting module is connected with first PNP pipe, NPN output circuit includes second NPN pipe, NPN voltage limiting module and NPN current -limiting module, and the base of second NPN pipe connects input, and the emitter connects NPN current -limiting module, and the collector connects switch output signal end, and NPN voltage limiting module is connected with second NPN pipe, reduces switch drive signal, and will output current be limited in the safe range, realizes short circuit protection, provides a freewheeling loop simultaneously, avoids generating overvoltage.

Description

Technical Field

[0001] This utility model relates to the field of switching circuits, and in particular to a simple current-limiting and voltage-limiting protection switching circuit. Background Technology

[0002] Traditional sensor switching output circuits are classified into two types based on their topology: NPN and PNP. The output directly drives the load, and to achieve a high driving capability, they have low internal resistance. However, during wiring and testing, if a short circuit occurs accidentally, the short-circuit current will be very large. Even a short short circuit can cause the output to burn out, resulting in loss of output function. Furthermore, if the output directly drives inductive loads such as relays, an overvoltage will occur when the output is cut off, breaking down the output stage and causing output malfunction. Utility Model Content

[0003] In view of the above-mentioned shortcomings in the current field of switching circuits, this utility model provides a simple current-limiting and voltage-limiting protection switching circuit, which reduces the switching drive signal, limits the output current within a safe range, realizes short-circuit protection, and provides a freewheeling loop to avoid overvoltage.

[0004] To achieve the above objectives, the embodiments of this utility model adopt the following technical solutions:

[0005] A simple current-limiting and voltage-limiting protection switch circuit, connected to a positive voltage, includes a PNP output line and an NPN output line connected thereto. The PNP output line includes a first NPN transistor, a first PNP transistor, a PNP voltage-limiting module, and a PNP current-limiting module. The base of the first NPN transistor is connected to the input terminal, the emitter is grounded, and the collector is connected to the base of the first PNP transistor. The emitter of the first PNP transistor is connected to the PNP current-limiting module, and the collector is connected to the switch output signal terminal. The PNP voltage-limiting module is connected to the first PNP transistor. The NPN output line includes a second NPN transistor, an NPN voltage-limiting module, and an NPN current-limiting module. The base of the second NPN transistor is connected to the input terminal, the emitter is connected to the NPN current-limiting module, and the collector is connected to the switch output signal terminal. The NPN voltage-limiting module is connected to the second NPN transistor.

[0006] According to one aspect of the present invention, the PNP voltage limiting module includes a first diode, the positive terminal of the first diode is grounded, and the negative terminal of the first diode is connected to the switch output signal terminal.

[0007] According to one aspect of the present invention, the PNP current limiting module includes a second PNP transistor and a first resistor. The collector of the second PNP transistor is connected to the collector of the first NPN transistor and the base of the first PNP transistor. The base of the second PNP transistor is connected to the emitter of the first PNP transistor and one end of the first resistor. The emitter of the second PNP transistor is connected to the other end of the first resistor and connected to a positive voltage.

[0008] According to one aspect of this utility model, if the magnitude of the output current is within a set range, the voltage drop generated by the output current across the second resistor decreases, and the second PNP transistor is turned off.

[0009] According to one aspect of this utility model, if the magnitude of the output current exceeds the set range, the voltage drop generated by the output current across the first resistor increases, causing the second PNP transistor to conduct and driving the current of the first PNP transistor to decrease.

[0010] According to one aspect of the present invention, the NPN voltage limiting module includes a second diode, the positive terminal of the second diode being connected to the switch output signal terminal, and the negative terminal of the second diode being connected to the positive voltage.

[0011] According to one aspect of the present invention, the NPN current limiting module includes a third NPN transistor and a second resistor. The collector of the third NPN transistor is connected to the base of the second NPN transistor. The emitter of the third NPN transistor is grounded, and the base is connected to one end of the second resistor and the emitter of the second NPN transistor. The other end of the second resistor is grounded.

[0012] According to one aspect of this utility model, if the magnitude of the output current is within a set range, the voltage drop generated by the output current across the second resistor decreases, and the third NPN transistor is turned off.

[0013] According to one aspect of this utility model, if the magnitude of the output current exceeds the set range, the voltage drop generated by the output current across the second resistor increases, causing the third NPN transistor to conduct and driving the current of the second NPN transistor to decrease.

[0014] According to one aspect of this utility model, it further includes a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor. One end of the third resistor is connected to the input terminal and the base of the first NPN transistor, and the other end of the third resistor is grounded. One end of the fourth resistor is connected to the input terminal and the base of the second NPN transistor, and the other end of the fourth resistor is grounded. The third and fourth resistors pull down the control signal at the input terminal to a low level. One end of the fifth resistor is connected to the positive voltage, and the other end is connected to the sixth resistor. The other end of the sixth resistor is connected to the collector of the first NPN transistor.

[0015] The advantages of this utility model are as follows: It includes a PNP output line and an NPN output line connected thereto. The PNP output line includes a first NPN transistor, a first PNP transistor, a PNP voltage limiting module, and a PNP current limiting module. The base of the first NPN transistor is connected to the input terminal, the emitter is grounded, and the collector is connected to the base of the first PNP transistor. The emitter of the first PNP transistor is connected to the PNP current limiting module, and the collector is connected to the switch output signal terminal. The PNP voltage limiting module is connected to the first PNP transistor. The NPN output line also includes a second NPN transistor, an NPN voltage limiting module, and an NPN current limiting module. The base of the second NPN transistor is connected to the input terminal, the emitter is connected to the NPN current limiting module, and the collector is connected to the switch output signal terminal. The NPN voltage limiting module is connected to the second NPN transistor. This reduces the switch drive signal, limits the output current to a safe range, achieves short-circuit protection, and provides a freewheeling loop to avoid overvoltage. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the circuit structure of a simplified current-limiting and voltage-limiting protection switch circuit according to the present invention.

[0018] Figure 2 This is a schematic diagram of the PNP circuit structure of a simple current-limiting and voltage-limiting protection switch circuit according to the present invention.

[0019] Figure 3 This is a schematic diagram of the NPN circuit structure of a simple current-limiting and voltage-limiting protection switch circuit according to the present invention. Detailed Implementation

[0020] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0021] Example 1:

[0022] like Figure 1As shown, a simple current-limiting and voltage-limiting protection switch circuit includes a PNP output line and an NPN output line connected thereto, which is connected to the positive voltage and the input terminal, and output to the switch output signal terminal.

[0023] The PNP circuit includes an NPN transistor Q1, a PNP transistor Q4, resistors R1, R4, and R3, a PNP voltage limiting module, and a PNP current limiting module. The PNP voltage limiting module includes a diode D2, and the PNP current limiting module includes a resistor R5 and a PNP transistor Q2. One end of resistor R1 is connected to the input terminal and the base of NPN transistor Q1, and the other end of resistor R1 is grounded. Resistor R1 pulls the control signal input to a low level, providing anti-interference capability. The emitter of NPN transistor Q1 is grounded, and its collector is connected to resistor R4. The other end of resistor R4 is connected to resistor R3, the collector of PNP transistor Q2, and the base of PNP transistor Q4. Resistor E3 and the emitter of PNP transistor Q2 are connected to the input voltage. The base of PNP transistor Q2 and the emitter of PNP transistor Q4 are connected together and connected to resistor R5. The emitter of PNP transistor Q4 is connected to the switch output signal terminal. The anode of diode D2 is connected to the switch output signal terminal, and its cathode and resistor R5 are connected to the positive voltage.

[0024] like Figure 2 The diagram shows the circuit structure of a PNP transistor. PNP transistor Q2 and resistor R5 constitute a PNP current-limiting module, providing current-limiting protection. The current-limiting value can be adjusted by changing the resistance of R5. During normal operation, when the output current is within the set range, the voltage drop across resistor R5 is reduced, insufficient to turn on PNP transistor Q2, and has no effect on the output. When the output current exceeds the set range, the voltage drop across resistor R5 increases to approximately 0.6V. This voltage turns on PNP transistor Q2, reducing the current driving PNP transistor Q4, thus reducing the output current and achieving the current-limiting effect.

[0025] Diode D2 provides a freewheeling path for the inductive load, achieving voltage limiting protection. When the PNP transistor Q4 is turned off, if there is no diode D2 in the circuit, the coil current of the inductive load changes, and the magnetic field around the coil also changes accordingly. This changing magnetic field will generate an induced electromotive force in the coil, and its direction is opposite to the direction of current change, thus hindering the change of current. That is, the induced electromotive force will prevent the PNP transistor Q4 from turning off. This voltage is high enough to break down the PNP transistor Q4, thereby maintaining a constant current. When diode D2 is present in the circuit, under normal conduction of the PNP transistor Q4, diode D2 bears the reverse voltage and enters the cutoff state, which has no impact on normal operation. When the PNP transistor Q4 is turned off, diode D2 provides a freewheeling path, and diode D2 conducts, achieving the voltage limiting effect.

[0026] The NPN circuit includes an NPN transistor Q5, a resistor R2, an NPN voltage limiting module, and an NPN current limiting module. The NPN voltage limiting module includes a diode D1, and the NPN current limiting module includes a resistor R6 and an NPN transistor Q3. One end of resistor R2 is connected to the input terminal, the collector of NPN transistor Q3, and the base of NPN transistor Q5. The other end of resistor R2 is grounded. Resistor R2 pulls the control signal input to the input terminal down to a low level, providing anti-interference capability. The base of NPN transistor Q3 is connected to the emitter of NPN transistor Q5 and resistor R6. The emitter of NPN transistor Q3 and the other end of resistor R6 are grounded. The collector of NPN transistor Q5 is connected to the switch output signal terminal. The anode of diode D1 is grounded, and the cathode is connected to the switch output signal terminal.

[0027] like Figure 3 The diagram shows the NPN circuit structure. NPN transistor Q3 and resistor R6 form an NPN current-limiting module to achieve current-limiting protection. The current-limiting value can be adjusted by changing the resistance of R6. During normal operation, when the output current is within the set range, the voltage drop across resistor R6 is reduced and insufficient to turn on NPN transistor Q3, thus having no effect on the output. When the output current exceeds the set range, the voltage drop across resistor R6 increases to approximately 0.6V. This voltage turns on NPN transistor Q3. After Q3 turns on, the current driving NPN transistor Q5 decreases, thereby reducing the output current and achieving the current-limiting effect.

[0028] Diode D1 provides a freewheeling path for the inductive load, achieving voltage limiting protection. When NPN transistor Q5 is turned off, if diode D1 is not in the circuit, the coil current of the inductive load changes, and the magnetic field around the coil also changes accordingly. This changing magnetic field will generate an induced electromotive force in the coil, and its direction is opposite to the direction of current change, thus hindering the change of current. That is, the induced electromotive force will prevent NPN transistor Q5 from turning off. This voltage is high enough to break down NPN transistor Q5, thus maintaining a constant current. When diode D1 is present in the circuit, under normal conduction of NPN transistor Q5, diode D1 bears the reverse voltage and enters the cutoff state, which has no impact on normal operation. When NPN transistor Q5 is turned off, diode D1 provides a freewheeling path. When diode D1 is on, the voltage at the upper end of NPN transistor Q5 is only one diode voltage drop higher than the positive voltage, about 0.7V, achieving the voltage limiting effect.

[0029] The advantages of this utility model are as follows: It includes a PNP output line and an NPN output line connected thereto. The PNP output line includes a first NPN transistor, a first PNP transistor, a PNP voltage limiting module, and a PNP current limiting module. The base of the first NPN transistor is connected to the input terminal, the emitter is grounded, and the collector is connected to the base of the first PNP transistor. The emitter of the first PNP transistor is connected to the PNP current limiting module, and the collector is connected to the switch output signal terminal. The PNP voltage limiting module is connected to the first PNP transistor. The NPN output line also includes a second NPN transistor, an NPN voltage limiting module, and an NPN current limiting module. The base of the second NPN transistor is connected to the input terminal, the emitter is connected to the NPN current limiting module, and the collector is connected to the switch output signal terminal. The NPN voltage limiting module is connected to the second NPN transistor. This reduces the switch drive signal, limits the output current to a safe range, achieves short-circuit protection, and provides a freewheeling loop to avoid overvoltage.

[0030] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the protection scope of the claims.

Claims

1. A simple current-limiting and voltage-limiting protection switch circuit, connected to a positive voltage, characterized in that, The system includes a PNP output line and an NPN output line connected thereto. The PNP output line includes a first NPN transistor, a first PNP transistor, a PNP voltage limiting module, and a PNP current limiting module. The base of the first NPN transistor is connected to the input terminal, the emitter is grounded, and the collector is connected to the base of the first PNP transistor. The emitter of the first PNP transistor is connected to the PNP current limiting module, and the collector is connected to the switch output signal terminal. The PNP voltage limiting module is connected to the first PNP transistor. The NPN output line also includes a second NPN transistor, an NPN voltage limiting module, and an NPN current limiting module. The base of the second NPN transistor is connected to the input terminal, the emitter is connected to the NPN current limiting module, and the collector is connected to the switch output signal terminal. The NPN voltage limiting module is connected to the second NPN transistor.

2. The simplified current-limiting and voltage-limiting protection switch circuit according to claim 1, characterized in that, The PNP voltage limiting module includes a first diode, the positive terminal of which is grounded, and the negative terminal of which is connected to the switch output signal terminal.

3. The simplified current-limiting and voltage-limiting protection switch circuit according to claim 2, characterized in that, The PNP current limiting module includes a second PNP transistor and a first resistor. The collector of the second PNP transistor is connected to the collector of the first NPN transistor and the base of the first PNP transistor. The base of the second PNP transistor is connected to the emitter of the first PNP transistor and one end of the first resistor. The emitter of the second PNP transistor is connected to the other end of the first resistor and connected to a positive voltage.

4. The simplified current-limiting and voltage-limiting protection switch circuit according to claim 3, characterized in that, If the output current is within the set range, the voltage drop across the second resistor decreases, and the second PNP transistor turns off.

5. The simplified current-limiting and voltage-limiting protection switch circuit according to claim 3, characterized in that, If the output current exceeds the set range, the voltage drop across the first resistor increases, causing the second PNP transistor to conduct and driving the current of the first PNP transistor to decrease.

6. The simplified current-limiting and voltage-limiting protection switch circuit according to claim 1, characterized in that, The NPN voltage limiting module includes a second diode, the positive terminal of which is connected to the switch output signal terminal, and the negative terminal of which is connected to the positive voltage.

7. The simplified current-limiting and voltage-limiting protection switch circuit according to claim 6, characterized in that, The NPN current limiting module includes a third NPN transistor and a second resistor. The collector of the third NPN transistor is connected to the base of the second NPN transistor. The emitter of the third NPN transistor is grounded, and the base is connected to one end of the second resistor and the emitter of the second NPN transistor. The other end of the second resistor is grounded.

8. The simplified current-limiting and voltage-limiting protection switch circuit according to claim 7, characterized in that, If the output current is within the set range, the voltage drop across the second resistor decreases, and the third NPN transistor is turned off.

9. The simplified current-limiting and voltage-limiting protection switch circuit according to claim 7, characterized in that, If the output current exceeds the set range, the voltage drop across the second resistor increases, causing the third NPN transistor to conduct and reducing the current of the second NPN transistor.

10. The simplified current-limiting and voltage-limiting protection switch circuit according to claim 1, characterized in that, It also includes a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor. One end of the third resistor is connected to the input terminal and the base of the first NPN transistor, and the other end of the third resistor is grounded. One end of the fourth resistor is connected to the input terminal and the base of the second NPN transistor, and the other end of the fourth resistor is grounded. The third and fourth resistors pull down the control signal at the input terminal to a low level. One end of the fifth resistor is connected to the positive voltage, and the other end is connected to the sixth resistor. The other end of the sixth resistor is connected to the collector of the first NPN transistor.

Images