Low-cost protection circuit

Abstract

The utility model relates to a low-cost protection circuit which comprises an input circuit, the output end of the input circuit is electrically connected with the power supply ends of a first control circuit, a second control circuit and an output control circuit at the same time, and the output end of the first control circuit is electrically connected with the grounding ends of the second control circuit and the output control circuit at the same time. The output end of the second control circuit is electrically connected with the control end of the output control circuit, and the input circuit, the first control circuit, the second control circuit and the output control circuit are all composed of discrete components. According to the scheme, the low-cost protection circuit is only composed of the two MOS tubes, the two voltage stabilizing diodes, the triode, the resistor, the capacitor and the switch, has the advantages of being simple in circuit and low in cost, and can achieve multiple protection functions of power supply overvoltage, undervoltage, reverse connection and surge current impact at the same time. The performance is reliable, an IC or an optocoupler or a single-chip microcomputer chip does not need to be arranged, programming codes are not needed, production is convenient, and the production efficiency is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to power protection circuit technical field especially relates to a low cost protection circuit. BACKGROUND

[0002] Common power protection circuit has overvoltage protection circuit, under voltage protection, reverse connection protection, surge current protection, and the existing power protection circuit is through protection IC or singlechip, or complex circuit to realize, and the cost is higher, and the chip still needs programming code, and the complexity is high.

[0003] In order to overcome above-mentioned insufficient, the scheme proposes a low cost protection circuit. INVENTION CONTENTS

[0004] The utility model discloses a kind of low cost protection circuits, including input circuit, the output end of the input circuit is simultaneously connected with the power supply end of first control circuit, second control circuit, output control circuit, the output end of the first control circuit is simultaneously connected with the ground terminal of second control circuit, output control circuit, the output end of the second control circuit is connected with the control end of output control circuit, and the input circuit, first control circuit, second control circuit and output control circuit are all by discrete component composition.

[0005] Low cost protection circuit, including input circuit, the output end of the input circuit is simultaneously connected with the power supply end of first control circuit, second control circuit, output control circuit, the output end of the first control circuit is simultaneously connected with the ground terminal of second control circuit, output control circuit, the output end of the second control circuit is connected with the control end of output control circuit, and the input circuit, first control circuit, second control circuit and output control circuit are all by discrete component composition.

[0006] Further, the protection circuit further includes indicator lamp circuit, the power supply end of the indicator lamp circuit is connected with the output end of the output control circuit, and the ground terminal of the indicator lamp circuit is connected with the output end of the first control circuit.

[0007] Further, the indicator lamp circuit includes resistance R21, R22 simultaneously connected with its power supply end, the other end of resistance R21 is connected with the anode of light emitting diode D15, the other end of resistance R22 is connected with the anode of light emitting diode D16, and the cathode of light emitting diode D15 and D16 is connected and is connected as the ground terminal of indicator lamp circuit.

[0008] Further, the input circuit includes input power positive terminal B+, switch SW1 input pin connected with input power positive terminal B+, and switch SW1 output pin is as the output end of input circuit.

[0009] Further, the first control circuit comprises a resistor R8 having one end electrically connected to the power supply end thereof, and the other end of the resistor R8 being electrically connected to the gate of the first MOS Q5 and the negative electrode of the voltage stabilizing diode ZD5, the drain of the first MOS Q5 being electrically connected to the input power supply ground GND, and the source of the first MOS Q5 and the positive electrode of the voltage stabilizing diode ZD5 being electrically connected and serving as the output end of the first control circuit.

[0010] Further, the first MOS Q5 is an N-channel MOS.

[0011] Further, the second control circuit comprises a resistor R3 and the emitter of a triode Q7, both of which are electrically connected to the power supply end thereof, the other end of the resistor R3 being electrically connected to the negative electrode of the voltage stabilizing diode ZD3 and one end of a resistor R5, the other end of the resistor R5 being electrically connected to one end of a capacitor C5 and the base of the triode Q7, the other end of the capacitor C5 being electrically connected to one end of a resistor R7 and the collector of the triode Q7 and serving as the output end of the second control circuit, the other end of the resistor R7 being electrically connected to the positive electrode of the voltage stabilizing diode ZD3 and serving as the ground end of the second control circuit.

[0012] Further, the triode Q7 is a PNP triode.

[0013] Further, the output control circuit comprises the source of a second MOS Q8 electrically connected to the power supply end thereof, the gate of the second MOS Q8 being electrically connected to one end of a resistor R11, the other end of the resistor R11 serving as the control end of the output control circuit, and the drain of the second MOS Q8 serving as the output end of the output control circuit.

[0014] Further, the second MOS Q8 is a P-channel MOS.

[0015] The present scheme has the following advantages:

[0016] The low-cost protection circuit of the present scheme is composed of two MOS, two voltage stabilizing diodes, one triode, resistors, capacitors and one switch, has the advantages of simple circuit and low cost, and can realize multiple protection functions of overvoltage, undervoltage, reverse connection and surge current impact. The performance is reliable, and no IC or optocoupler or single-chip microcomputer is needed, and no programming code is needed, which is convenient for production and improves the production efficiency. Optionally, an indicator lamp circuit can be added according to needs to facilitate timely understanding of the working state. The circuit of the present scheme has universality and can be applied to various power supply occasions: only by replacing the types of voltage stabilizing diodes and MOS and adjusting the parameters of resistors and capacitors, different high-voltage circuits and large-current circuits can be matched, so the circuit of the present scheme has the function of protecting personal safety. BRIEF DESCRIPTION OF DRAWINGS

[0017] Fig. 1 The structural diagram of the low-cost protection circuit of the utility model;

[0018] Fig. 2 The circuit diagram of the low-cost protection circuit of the utility model. DETAILED DESCRIPTION

[0019] The embodiments are given only for the purpose of illustration and should not be understood as limiting the utility model, including the drawings for reference and illustration only, and do not constitute the limitation of the utility model patent protection scope, because many changes can be made to the utility model without departing from the spirit and scope of the utility model.

[0020] As shown in the figure, Figs. 1-2 The low-cost protection circuit comprises an input circuit, the output end of the input circuit is electrically connected with the power supply end of a first control circuit, a second control circuit and an output control circuit at the same time, the output end of the first control circuit is electrically connected with the ground end of the second control circuit and the output control circuit at the same time, the output end of the second control circuit is electrically connected with the control end of the output control circuit, and the input circuit, the first control circuit, the second control circuit and the output control circuit are all composed of discrete components.

[0021] Optionally, the protection circuit further comprises an indicator lamp circuit, the power supply end of the indicator lamp circuit is electrically connected with the output end of the output control circuit, and the ground end of the indicator lamp circuit is electrically connected with the output end of the first control circuit.

[0022] Specifically, the indicator lamp circuit comprises resistors R21 and R22 which are electrically connected with the power supply end at the same time, the other end of the resistor R21 is electrically connected with the anode of a light-emitting diode D15, the other end of the resistor R22 is electrically connected with the anode of a light-emitting diode D16, and the cathodes of the light-emitting diodes D15 and D16 are electrically connected and serve as the ground end of the indicator lamp circuit. According to the specific use, one indicator lamp circuit (for example, one road of the resistor R21 and the light-emitting diode D15 in series, and no resistor R22 and light-emitting diode D16) can be selected to further save the cost.

[0023] Specifically, the input circuit comprises an input power positive terminal B+, a switch SW1 input pin which is electrically connected with the input power positive terminal B+, and a switch SW1 output pin which serves as the output end of the input circuit. The switch SW1 can adopt various mechanical switches, and the model thereof can be selected according to the specific needs. As one of the embodiments, the input power positive terminal B+ of the embodiment is 18V, and 24V or 12V or the like can also be selected according to the needs.

[0024] Specifically, the first control circuit comprises a resistor R8 having one end electrically connected to the power supply end thereof, the other end of the resistor R8 being electrically connected to the gate of a first MOS tube Q5 and the negative electrode of a Zener diode ZD5, the drain of the first MOS tube Q5 being electrically connected to the input power supply ground end GND, the source of the first MOS tube Q5 and the positive electrode of the Zener diode ZD5 being electrically connected and serving as the output end of the first control circuit. The first MOS tube Q5 is an N-channel MOS tube. As one of the embodiments, the power supply end of the first control circuit of the embodiment is electrically connected to the 18V input power supply positive end B+, and the Zener diode ZD5 is a 19V Zener diode. The function and working principle of the first control circuit are as follows: (1) when the input power supply voltage is greater than or equal to 18V, the gate voltage of the first MOS tube Q5 is higher than the Vgs threshold voltage thereof through the resistor R8 and the Zener diode ZD5, the first MOS tube Q5 is turned on, the source S of the first MOS tube Q5 is electrically connected to the drain D thereof, and the output end of the first control circuit is electrically connected to the ground end of the second control circuit, the output control circuit and the indicator lamp circuit. (2) when the input power supply voltage is less than 18V or the power supply is reversely connected, the gate voltage of the first MOS tube Q5 is lower than the Vgs threshold voltage thereof through the resistor R8 and the Zener diode ZD5, the first MOS tube Q5 is turned off, the source S of the first MOS tube Q5 is disconnected from the drain D thereof, and the output end of the first control circuit has no output, so that the ground end of the second control circuit, the output control circuit and the indicator lamp circuit has no loop and cannot work. Therefore, the first control circuit has the dual functions of under-voltage protection and reverse connection protection.

[0025] Specifically, the second control circuit comprises a resistor R3 and the emitter of a triode Q7, both of which are electrically connected to the power supply end thereof, the other end of the resistor R3 being electrically connected to the negative electrode of a Zener diode ZD3 and one end of a resistor R5, the other end of the resistor R5 being electrically connected to one end of a capacitor C5 and the base of the triode Q7, the other end of the capacitor C5 being electrically connected to one end of a resistor R7 and the collector of the triode Q7 and serving as the output end of the second control circuit, the other end of the resistor R7 being electrically connected to the positive electrode of the Zener diode ZD3 and serving as the ground end of the second control circuit. The triode Q7 is a PNP triode. As one of the embodiments, the power supply end of the second control circuit of the embodiment is electrically connected to the 18V input power supply positive end B+, and the Zener diode ZD3 is a 19V Zener diode. The second control circuit is used for automatically controlling the output control circuit under three conditions of normal voltage, overvoltage and inrush current, which will be described in detail in the following.

[0026] Specifically, the output control circuit includes the source of the second MOS tube Q8 electrically connected to the power supply end thereof, the gate of the second MOS tube Q8 electrically connected to one end of the resistor R11, the other end of the resistor R11 electrically connected to the output end of the second control circuit (i.e. the collector of the transistor Q7) as the control end of the output control circuit, and the drain of the second MOS tube Q8 as the output end VOUT of the output control circuit. The second MOS tube Q8 is a P-channel MOS tube. As one of the embodiments, the source of the second MOS tube Q8 is electrically connected to 18V of the positive end B+ of the input power supply. The functions and working principles of the second control circuit, the output control circuit and the indicator lamp circuit are as follows:

[0027] (3) When the input power supply is 18V, 18V passes through the switch SW1, one way from the resistor R3 to the negative end of the voltage stabilizing diode ZD3. Since the 19V voltage stabilizing condition is not reached, the voltage stabilizing diode ZD3 is not turned on. The 18V voltage reaches the base of the transistor Q7 through the resistor R5, and is as high as the 18V voltage reaching the emitter of the transistor Q7 through the other way of the switch SW1, and is not enough to form the starting voltage difference of the transistor Q7. The transistor Q7 is cut off and not turned on. At this time, the source S voltage of the second MOS tube Q8 is 18V, the voltage between the source S and the gate G is 18V, and the gate G voltage of the second MOS tube Q8 to the ground (i.e. the ground end GND of the input power supply) is 0V. Therefore, the second MOS tube Q8 reaches the P-channel MOS tube turn-on condition, the source S and the drain D of the second MOS tube Q8 are turned on, the output end VOUT of the output control circuit outputs 18V power supply (for the load), and the light emitting diodes D15 and D16 of the indicator lamp circuit as one of the loads are turned on and emit light, indicating that the circuit works in the normal state.

[0028] (4) When the input power supply is greater than 18V, such as 20V, which belongs to the overvoltage state. The overvoltage 20V passes through the resistor R3 to the negative end of the voltage stabilizing diode ZD3, which exceeds the 19V voltage stabilizing value. The voltage stabilizing diode ZD3 is turned on and the constant voltage is 19V. The 19V voltage reaches the base of the transistor Q7 through the resistor R5, and forms the starting voltage difference of the transistor Q7 with the 20V voltage reaching the emitter of the transistor Q7 through the other way of the switch SW1. The transistor Q7 is turned on, and the collector voltage of the transistor Q7 is raised. At this time, the output end of the second control circuit is high, and the high level reaches the gate G of the second MOS tube Q8 through the resistor R11, which does not meet the P-channel MOS tube turn-on condition. The second MOS tube Q8 is in the off state, the drain D and the source S of the second MOS tube Q8 are disconnected, i.e. the output end VOUT of the output control circuit has no voltage output, the light emitting diodes D15 and D16 are not turned on and emit light, and the circuit is in the overvoltage automatic protection state.

[0029] (5) still take input power supply 18V for example, when the switch SW1 is just on, will produce a momentary surge current impact, the following two stages to describe the circuit working process: the first stage, the moment (PNP) transistor Q7 is turned on, the collector of the transistor Q7 is high, the gate of the second MOS tube Q8 through the resistor R11 and the transistor Q7 quickly to 18V voltage, the second MOS tube Q8 does not meet the conduction condition, off state, the output of the output control circuit VOUT no voltage output, light emitting diode D15, D16 is not conductive not light, the circuit is in the surge current automatic protection state. The second stage, then 18V voltage through resistor R3 and R5 to the base of the transistor Q7, (the same as the previous analysis) the transistor Q7 is off, at the same time, the voltage across the capacitor C5 cannot be changed suddenly, so 18V voltage through R3, R5, R7 loop to charge capacitor C5, during the charging period, the capacitor is equivalent to an internal resistance with increasing resistance, the internal resistance and R7 series voltage division, the voltage on the internal resistance increases gradually, through the resistor R11 to the gate of the second MOS tube Q8 G level thus gradually reduced until the gate of the second MOS tube Q8 (P channel MOS tube) G- source S voltage difference: Vgs < Vgs threshold, the second MOS tube Q8 (P channel MOS tube) is opened, so as to realize the circuit slow start. This has realized the two functions of surge current automatic protection and slow start of the circuit of the scheme.

[0030] Description: the ground of the second control circuit, output control circuit and indicator light circuit of the scheme is electrically connected and marked as GND1. When the first MOS tube Q5 is turned on, GND1 is electrically connected with the input power supply ground GND.

[0031] The circuit of the scheme has universality and can be applied to various power supply occasions: when applied, only need to replace the type of ZD3, ZD5 and Q5, Q8, adjust the resistance and capacitance parameters to match different high voltage circuits and large current circuits, so the circuit of the scheme also has the important role of protecting personal safety.

[0032] The scheme has the following beneficial effects:

[0033] The low-cost protection circuit of the scheme is composed of two MOS transistors, two voltage stabilizing diodes, a transistor, resistors, capacitors and a switch, has the advantages of simple circuit and low cost, and can simultaneously realize multiple protection functions of power overvoltage, power undervoltage, reverse connection and surge current impact. The performance is reliable, does not need to be equipped with IC or optocoupler or single-chip microcomputer chip, does not need to be programmed, is convenient for production, and improves production efficiency. Optionally, an indicating lamp circuit can be added according to needs, so that the working state can be understood in time. The circuit of the scheme has universality and can be applied to occasions of power supply of various powers: only by replacing the types of the voltage stabilizing diodes and the MOS transistors and adjusting the parameters of the resistors and the capacitors, different high-voltage circuits and large-current circuits can be matched, so that the circuit of the scheme has the effect of protecting personal safety.

[0034] The above embodiment is a preferred embodiment of the utility model, but the embodiment of the utility model is not limited by the above embodiment, and any change, modification, replacement, combination, simplification, which does not deviate from the spirit and principle of the utility model, should be an equivalent replacement mode, and all are included in the protection scope of the utility model.

Claims

1. A low-cost protection circuit, characterized in that: It includes an input circuit, the output end of the input circuit is electrically connected to the power supply end of the first control circuit, the second control circuit, and the output control circuit at the same time, the output end of the first control circuit is electrically connected to the ground end of the second control circuit and the output control circuit at the same time, the output end of the second control circuit is electrically connected to the control end of the output control circuit, and the input circuit, the first control circuit, the second control circuit, and the output control circuit are all composed of discrete components.

2. The low-cost protection circuit according to claim 1, characterized in that: The protection circuit further includes an indicator light circuit, wherein a power supply terminal of the indicator light circuit is electrically connected to an output terminal of the output control circuit, and a ground terminal of the indicator light circuit is electrically connected to an output terminal of the first control circuit.

3. The low-cost protection circuit according to claim 2, characterized in that: The indicator light circuit includes resistors R21 and R22 electrically connected to its power supply end at the same time. The other end of the resistor R21 is electrically connected to the positive electrode of the light-emitting diode D15, and the other end of the resistor R22 is electrically connected to the positive electrode of the light-emitting diode D16. The cathodes of the light-emitting diodes D15 and D16 are electrically connected and serve as the ground end of the indicator light circuit.

4. The low-cost protection circuit according to claim 1, characterized in that: The input circuit includes an input power positive terminal B+, an input pin of a switch SW1 electrically connected to the input power positive terminal B+, and an output pin of the switch SW1 serving as an output terminal of the input circuit.

5. The low-cost protection circuit according to claim 1, characterized in that: The first control circuit includes a resistor R8 having one end electrically connected to its power supply terminal, the other end of the resistor R8 being electrically connected to both the gate of the first MOS transistor Q5 and the cathode of the Zener diode ZD5, the drain of the first MOS transistor Q5 being electrically connected to the input power ground GND, and the source of the first MOS transistor Q5 being electrically connected to the anode of the Zener diode ZD5 and serving as the output terminal of the first control circuit.

6. The low-cost protection circuit according to claim 5, characterized in that: The first MOS transistor Q5 is an N-channel MOS transistor.

7. The low-cost protection circuit according to claim 1, characterized in that: The second control circuit includes a resistor R3 and an emitter of a transistor Q7 electrically connected to its power supply terminal at the same time. The other end of the resistor R3 is electrically connected to the cathode of the voltage-stabilizing diode ZD3 and one end of the resistor R5 at the same time. The other end of the resistor R5 is electrically connected to one end of the capacitor C5 and the base of the transistor Q7 at the same time. The other end of the capacitor C5 is electrically connected to one end of the resistor R7 and the collector of the transistor Q7 and serves as the output end of the second control circuit. The other end of the resistor R7 is electrically connected to the anode of the voltage-stabilizing diode ZD3 and serves as the ground end of the second control circuit.

8. The low-cost protection circuit according to claim 7, characterized in that: The transistor Q7 is a PNP transistor.

9. The low-cost protection circuit according to claim 1, characterized in that: The output control circuit includes a source of a second MOS transistor Q8 electrically connected to its power supply terminal, a gate of the second MOS transistor Q8 electrically connected to one end of a resistor R11, the other end of the resistor R11 serving as a control terminal of the output control circuit, and a drain of the second MOS transistor Q8 serving as an output terminal of the output control circuit.

10. The low-cost protection circuit according to claim 9, characterized in that: The second MOS transistor Q8 is a P-channel MOS transistor.

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