CN102739235B - Switching value acquisition insulating circuit - Google Patents

Abstract

The invention discloses a switch quantity acquisition isolation circuit, comprising: a reverse protection unit, a current constant unit, a voltage measurement unit and a photoelectric isolation unit, the switch signal is input to the reverse protection unit, and the reverse protection unit is connected with the current constant unit , the reverse protection unit protects the circuit from being damaged after the switching value signal input is reversely connected to the ground, and the current constant unit keeps the input current in the constant circuit after the voltage opening condition is met. The voltage measuring unit is connected with the current constant unit, and the voltage measuring unit controls the threshold voltage to achieve the voltage signal condition for opening the circuit. The photoelectric isolation unit is connected with the voltage measurement unit, and the photoelectric isolation unit isolates the external input signal and the internal control signal, so as to avoid the internal circuit damage caused by external input signal interference and external fault. The invention can ensure the constant input current in the process of collecting the switch input signal, ensure the reliable operation of the photoelectric coupler, the circuit calculation is simple, the power is low, and the calorific value is small.

Description

A switching value acquisition isolation circuit

technical field

The invention relates to a switch quantity acquisition isolation circuit, in particular to a switch quantity acquisition isolation circuit with constant front-end input current.

Background technique

As a basic input circuit, the switching value input acquisition circuit is to complete the state information acquisition and processing of the on-site switching value, convert the external electrical signal into a low-voltage digital signal used by the internal circuit, and cooperate with the field equipment to complete the corresponding control. The physical layout is closest to the on-site actuator, the working environment is harsh, and the reliability requirements are high.

The existing circuit of this type adopts the form of resistive voltage division, the input current changes with the change of the input voltage, the parameter calculation process is more complicated, and it is not conducive to the stable operation of related devices, and the circuit consumes power when the input voltage is large It is also large, which will cause the circuit to heat up and affect the normal operation of the surrounding circuits.

A prior art was applied by Nanjing Nanrui Jibao Electric Co., Ltd. and Nanjing Nanrui Jibao Engineering Technology Co., Ltd. on July 24, 2009, and was published on February 2, 2011. The publication number is CN 101964653A. Invention patent application "switch input circuit". The circuit divides the voltage through R4 and R5 resistors. After the voltage on R5 reaches the breakdown voltage value of the Zener diode Z1, the circuit meets the voltage conduction condition. With the increase of the input voltage, the current of the circuit gradually increases. Increase, after satisfying the current conduction condition of the optocoupler, the input result will feed back a high level to the actuator, indicating that the input circuit is conduction.

Technical disadvantages of previous circuits:

(1) In the past, the input circuit used the method of resistor division to collect the voltage on the divider resistor to complete the conduction of the circuit. The current of the circuit changes with the change of the external switch voltage, and the calculation is complicated, the accuracy is low, and the power consumption is low. Larger, which is not conducive to the long-term stable operation of the optocoupler;

(2) The calculation of the circuit is complicated. It is necessary to calculate the voltage to meet the conditions, and then to calculate the current to meet the conditions. It is also necessary to calculate the conditions to be satisfied by the current transmission ratio of the photocoupler, and the circuit derating should also be considered;

(3) The power consumption of the circuit is relatively high.

Contents of the invention

The purpose of the present invention is to provide a switching value acquisition isolation circuit, which can ensure the constant input current and ensure the reliable and stable operation of the photocoupler during the process of switching value input signal acquisition. The circuit calculation is simple, the power is low, and the circuit generates heat. Small quantity.

In order to achieve the purpose of the above invention, the present invention specifically provides a technical realization scheme of a switch value acquisition isolation circuit, a switch value acquisition isolation circuit, including: a reverse protection unit, a current constant unit, a voltage measurement unit and a photoelectric isolation unit. The switching value signal is input to the reverse protection unit, and the reverse protection unit is connected to the current constant unit, and the reverse protection unit protects the circuit from being damaged after the switching value signal input is reversely connected to the ground. After the current constant unit meets the voltage turn-on condition, the input current in the constant circuit. The voltage measuring unit is connected with the current constant unit, and the voltage measuring unit controls the threshold voltage to achieve the voltage signal condition for opening the circuit. The photoelectric isolation unit is connected with the voltage measurement unit, and the photoelectric isolation unit isolates the external input signal and the internal control signal to avoid internal circuit damage caused by external input signal interference and external faults.

As a further improvement of the technical solution of the switching value acquisition isolation circuit of the present invention, the current constant unit includes a second transistor and a second resistor, the second resistor is connected between the gate and the emitter of the second transistor, and the second resistor is connected between the gate and the emitter of the second transistor. The emitter of the second triode is connected with the cathode of the anti-reverse diode, and the gate and collector of the second triode are connected with the voltage measuring unit.

As a further improvement of the technical solution of the switching value acquisition isolation circuit of the present invention, the voltage measurement unit includes a first triode, a Zener diode and a first resistor, and the first resistor is connected to the gate and collector of the first triode In between, the cathode of the Zener diode is connected to the collector of the first triode, the anode of the Zener diode is connected to the photoelectric isolation unit, the emitter of the first triode is connected to the gate of the second triode, and the first triode is connected to the gate of the second transistor. The gate of one transistor is connected to the collector of the second transistor.

As another improvement of the technical solution of a switching value acquisition isolation circuit in the present invention, the voltage measurement unit includes a first triode, a Zener diode and a first resistor, and the first resistor and the Zener diode are connected in series in the first triode Between the gate and the collector of the Zener diode, the cathode of the Zener diode is connected to the first resistor, the anode of the Zener diode is connected to the photoelectric isolation unit, and the anode of the Zener diode is also connected to the collector of the first transistor. The emitter of one triode is connected with the gate of the second triode, and the gate of the first triode is connected with the collector of the second triode.

As a further improvement of the technical solution of a switching value acquisition isolation circuit in the present invention, the photoelectric isolation unit includes an optocoupler module and a third resistor, the optocoupler module includes a transmitting end and a receiving end, the anode of the light emitting diode at the transmitting end and the anode of the Zener diode The cathode of the light-emitting diode at the transmitting end is connected to the input grounding end, the third resistor is connected between the receiving end of the optocoupler module and the ground, and the receiving end of the optocoupler module is connected to the result output end.

As a further improvement of another technical solution of the switching value acquisition isolation circuit of the present invention, the photoelectric isolation unit includes an optocoupler module and a third resistor, the optocoupler module includes a transmitting end and a receiving end, and the anode of the light emitting diode at the transmitting end is connected to the second resistor. The gate of the triode is connected, the cathode of the light-emitting diode at the transmitting end is connected to the emitter of the first triode, the third resistor is connected between the receiving end of the optocoupler module and the ground, the receiving end of the optocoupler module is connected to the result output end connected.

As a further improvement of the technical solution of the switching value acquisition isolation circuit of the present invention, the reverse protection unit includes an anti-reverse diode, the anode of the anti-reverse diode is connected to the switching value input signal, and the cathode of the anti-reverse diode is connected to the current constant unit.

As another improvement of the technical solution of the switching value acquisition isolation circuit of the present invention, the reverse protection unit includes an anti-reverse diode, the cathode of the anti-reverse diode is connected to the ground, and the anode of the anti-reverse diode is connected to the photoelectric isolation unit.

As a further improvement of the technical solution of the switching value acquisition isolation circuit of the present invention, the voltage V _BC between the gate and the collector of the first triode is between 0V and the difference between the input voltage and the threshold voltage of the switching value acquisition isolation circuit between.

As a further improvement of the technical solution of the switching value acquisition isolation circuit of the present invention, the threshold voltage of the switching value acquisition isolation circuit is the conduction voltage drop of the anti-reverse diode, the voltage between the emitter and the collector of the second triode, and the stable voltage. The sum of the breakdown voltage of the voltage diode and the conduction voltage of the light-emitting diode at the emitting end of the optocoupler module.

By implementing the technical scheme of the above-mentioned switch quantity acquisition isolation circuit of the present invention, it has the following technical effects:

(1) The circuit structure of the present invention is simple, and the characteristics of constant voltage across the diode collector and emitter are used to ensure that the circuit current remains unchanged, and the input current can be calculated quickly and easily;

(2) The input current of the circuit of the present invention all passes through the optocoupler, and no other circuit separates the current, ensuring that the optocoupler works in a stable state;

(3) The overall current of the circuit in the present invention is reduced, reducing power consumption.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is the circuit principle diagram of a kind of switching quantity input circuit of prior art;

Fig. 2 is a structural composition block diagram of a specific embodiment of the switching value acquisition isolation circuit of the present invention;

Fig. 3 is the circuit schematic diagram of Embodiment 1 of the switching value acquisition isolation circuit of the present invention;

Fig. 4 is the circuit schematic diagram of Embodiment 2 of the switching value acquisition isolation circuit of the present invention;

Fig. 5 is the circuit schematic diagram of Embodiment 3 of the switching value acquisition isolation circuit of the present invention;

Fig. 6 is the circuit schematic diagram of embodiment 4 of the switching value acquisition isolation circuit of the present invention;

In the figure: 1-reverse protection unit, 2-current constant unit, 3-voltage measurement unit, 4-photoelectric isolation unit, Q1-first triode, Q2-second triode, V1-optocoupler module, V2-zener diode, V3-anti-reverse diode, R1-first resistor, R2-second resistor, R3-third resistor.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

As shown in accompanying drawings 2 to 6, a specific embodiment of a switching value acquisition isolation circuit of the present invention is given, and the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

A specific implementation of a switching value acquisition isolation circuit as shown in Figure 2 includes: a reverse protection unit 1, a current constant unit 2, a voltage measurement unit 3 and a photoelectric isolation unit 4, and the switching value signal is input to the reverse protection Unit 1, the reverse protection unit 1 is connected to the current constant unit 2, the reverse protection unit 1 protects the circuit from being damaged after the switching value signal input is reversely connected to the ground, and the current constant unit 2 satisfies the voltage opening condition, and the constant current in the circuit will not be damaged. Input Current. The voltage measurement unit 3 is connected with the current constant unit 2, and the voltage measurement unit 3 controls the threshold voltage to achieve the voltage signal condition for opening the circuit. The photoelectric isolation unit 4 is connected with the voltage measurement unit 3, and the photoelectric isolation unit 4 isolates the external input signal and the internal control signal, so as to avoid the internal circuit damage caused by external input signal interference and external fault.

As shown in Embodiment 1 of FIG. 3 , the current constant unit 2 further includes a second transistor Q2 and a second resistor R2, and the second resistor R2 is connected between the gate and the emitter of the second transistor Q2, The emitter of the second triode Q2 is connected to the cathode of the anti-reverse diode V3 , and the gate and collector of the second triode Q2 are connected to the voltage measuring unit 3 . The voltage measurement unit 3 further includes a first triode Q1, a Zener diode V2 and a first resistor R1, the first resistor R1 is connected between the gate and the collector of the first triode Q1, and the cathode of the Zener diode V2 It is connected to the collector of the first triode Q1, the anode of the Zener diode V2 is connected to the photoelectric isolation unit 4, the emitter of the first triode Q1 is connected to the gate of the second triode Q2, and the first triode The gate of the transistor Q1 is connected to the collector of the second transistor Q2. The photoelectric isolation unit 4 further includes an optocoupler module V1 and a third resistor R3. The optocoupler module V1 includes a transmitter and a receiver. The anode of the light-emitting diode at the transmitter is connected to the anode of the Zener diode V2. The ground terminal of the optocoupler module V1 is connected to the ground, the third resistor R3 is connected between the receiving terminal of the optocoupler module V1 and the ground, and the receiving terminal of the optocoupler module V1 is connected to the result output terminal. The reverse protection unit 1 further includes an anti-reverse diode V3, the anode of the anti-reverse diode V3 is connected to the switching input signal, and the cathode of the anti-reverse diode V3 is connected to the current constant unit 2 .

As shown in Embodiment 2 of accompanying drawing 4, on the basis of Embodiment 1, the position of the Zener diode V2 is changed, and the voltage measurement unit 3 further includes a first triode Q1, a Zener diode V2 and a first resistor R1, and the first A resistor R1 and a Zener diode V2 are connected in series between the gate and collector of the first triode Q1, the cathode of the Zener diode V2 is connected to the first resistor R1, and the anode of the Zener diode V2 is connected to the photoelectric isolation unit 4 , the anode of the Zener diode V2 is also connected to the collector of the first transistor Q1, the emitter of the first transistor Q1 is connected to the gate of the second transistor Q2, and the gate of the first transistor Q1 The pole is connected with the collector of the second triode Q2.

As shown in Embodiment 3 of accompanying drawing 5, on the basis of Embodiment 2, the position of the photoisolation unit 4 is changed, the photoisolation unit 4 further includes an optocoupler module V1 and a third resistor R3, and the optocoupler module V1 includes a transmitting terminal and a third resistor R3. The anode of the light-emitting diode at the receiving end and the transmitting end are connected to the gate of the second transistor Q2, the cathode of the light-emitting diode at the transmitting end is connected to the emitter of the first transistor Q1, and the third resistor R3 is connected to the optocoupler module V1. Between the receiving end and the ground, the receiving end of the optocoupler module V1 is connected to the result output end.

As shown in Embodiment 4 of accompanying drawing 6, on the basis of Embodiment 1, the position of the anti-reverse diode V3 is changed, and the reverse protection unit 1 further includes an anti-reverse diode V3, the cathode of the anti-reverse diode V3 is connected to the ground, and the anti-reverse diode V3 is connected to the ground. The anode of V3 is connected to the photoelectric isolation unit 4 .

The voltage V _BC between the gate and the collector of the first triode Q1 is between the input voltage and the threshold voltage of the switching value acquisition isolation circuit. The threshold voltage of the switching value acquisition isolation circuit is the conduction voltage drop of the anti-reverse diode V3, the voltage between the emitter and collector of the second triode Q2, the breakdown voltage of the Zener diode V2 and the light emission of the emitter of the optocoupler module V1 The sum of the conduction voltages of the diodes.

Taking Embodiment 1 as an example, the circuit principle is analyzed as follows: the voltage threshold condition that the switching value acquisition isolation circuit needs to meet: the conduction voltage drop of the anti-reverse diode V3 is 1.0V, and the voltage V between the two points AB _AB =2*V _be =2*0.6=1.2V, the breakdown voltage of Zener diode V2 is 5.6V, and the conduction voltage V _F of the light-emitting diode at the transmitter end of optocoupler module V1 is 1.2V, then the threshold voltage of conduction V _sat =1.0+1.2+5.6+1.2=9V. After the circuit satisfies the voltage condition, the current remains basically constant as the input voltage increases. Since the resistance value of the first resistor R1 is relatively large, the current generated on the first resistor R1 can be ignored, and I=V _be /R2=0.6V/120Ω=5mA. When both the voltage and current conditions are satisfied, the circuit is turned on, and the output result is a high level, and the other changing voltages in the input circuit part of the switching value acquisition isolation circuit are all added to the base of the first triode Q1 and The voltage V _BC between the two ends of the collector, that is, between point B and point C in Figure 3, has a voltage range of about 0V to the difference between the input voltage and the threshold voltage.

The present invention utilizes the characteristic of constant voltage of PNP triode V _be , and connects the second resistance R2 in parallel to generate a fixed current of the circuit, I=V _be /R2=0.6/120=5mA, wherein the current can be adjusted according to the actual situation, and the adjustment is simple easy. Utilizing the feature that the PNP transistor V _bc can withstand a large voltage, load all other voltages in the circuit except the voltage drop of the anti-reverse diode V3, the second transistor Q2, the voltage regulator diode V2 and the light-emitting diode at the emitting end of the optocoupler module V1 The two ends of the base and the collector of the first triode Q1 ensure the stability of the circuit. Utilizing the characteristics of the stable voltage of the Zener diode V2, the threshold value of the input voltage of the switching value acquisition isolation circuit is basically determined, and the voltage threshold value can be determined by adjusting the voltage stabilization value, and the adjustment is simple and easy. The circuit has the function of anti-reverse connection, using the characteristics of anti-reverse diode V3 to ensure that the device will not be damaged after the input voltage is reversed. The circuit has anti-interference ability. Using the characteristics of the optocoupler module V1 in the photoelectric isolation unit, the optical signal is converted into an electrical signal to realize the electrical isolation of the external electrical circuit and the internal signal circuit. At the same time, there are no high-power devices in the circuit, the package is small, the space occupied is small, and the power consumption is low, which is conducive to intensive multi-channel use. This circuit has a wide range of applications, and can be used in various systems such as 24V, 36V, and 48V used in the industrial field and 55V, 110V used in the rail locomotive field.

The present invention has the following technical effects:

(1) Adopt the characteristic of constant V _be voltage of PNP transistor to stabilize the input current of the circuit;

(2) Adopting the characteristic that PNP triode V _bc can withstand a large voltage, the voltage exceeding the circuit threshold value is loaded on both ends of it, which has a wide range of applications and can be applied to multi-voltage level design;

(3) Use optocoupler for signal isolation;

(4) Use rectifier diodes for reverse protection;

(5) Use Zener diodes to set the input voltage threshold;

(6) If the input current is constant, the input current will not change when the input voltage changes, then the optocoupler can work stably, and the calculation is relatively simple compared to the circuit;

(7) The present invention has the characteristics of novel structure, simple circuit, practicality and reliability, and low cost, and can meet the needs of industrial field control within a certain range, and belongs to an economical, practical, stable and reliable switching input acquisition circuit.

The above descriptions are only preferred embodiments of the present invention, and do not limit the present invention in any form. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person familiar with the art, without departing from the scope of the technical solution of the present invention, can use the methods and technical content disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent of equivalent change Example. Therefore, any simple modifications, equivalent replacements, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention, which do not deviate from the technical solutions of the present invention, still fall within the protection scope of the technical solutions of the present invention.

Claims (11)

1. a switch acquisition buffer circuit, it is characterized in that, comprise: reverse protection unit (1), current constant unit (2), voltage measurement unit (3) and Phototube Coupling unit (4), on-off model inputs to reverse protection unit (1), described reverse protection unit (1) is connected with current constant unit (2), the input of reverse protection unit (1) protection switch amount signal connects instead can not damage circuit with ground, the input voltage of current constant unit (2) is after meeting the threshold voltage condition that switch acquisition buffer circuit opens, along with the increase of input voltage, input current in switch acquisition buffer circuit is constant, described voltage measurement unit (3) is connected with current constant unit (2), and voltage measurement unit (3) controls threshold voltage, to reach the voltage conditions that switch acquisition buffer circuit is opened, described Phototube Coupling unit (4) is connected with voltage measurement unit (3), and Phototube Coupling unit (4) carries out the isolation of external input signal and internal control signal, avoids the internal circuit that external input signal disturbs and external fault causes to damage, described current constant unit (2) comprises the second triode (Q2) and the second resistance (R2), between the gate pole that second resistance (R2) is connected to the second triode (Q2) and emitter, the emitter of the second triode (Q2) is connected with the negative electrode of counnter attack diode (V3), and the gate pole of the second triode (Q2) is connected with voltage measurement unit (3) with collector electrode, when described input voltage and input current meet switch acquisition buffer circuit open condition time, switch acquisition buffer circuit conducting, and by described Phototube Coupling unit (4) externally outputs level signals, the threshold voltage that described switch acquisition buffer circuit is opened is determined by described reverse protection unit (1), current constant unit (2), voltage measurement unit (3) and Phototube Coupling unit (4).

2. a kind of switch acquisition buffer circuit according to claim 1, it is characterized in that: described voltage measurement unit (3) comprises the first triode (Q1), voltage stabilizing didoe (V2) and the first resistance (R1), between the gate pole that first resistance (R1) is connected to the first triode (Q1) and collector electrode, the negative electrode of voltage stabilizing didoe (V2) is connected with the collector electrode of the first triode (Q1), the anode of voltage stabilizing didoe (V2) is connected with Phototube Coupling unit (4), the emitter of the first triode (Q1) is connected with the gate pole of the second triode (Q2), the gate pole of the first triode (Q1) is connected with the collector electrode of the second triode (Q2).

3. a kind of switch acquisition buffer circuit according to claim 1, it is characterized in that: described voltage measurement unit (3) comprises the first triode (Q1), voltage stabilizing didoe (V2) and the first resistance (R1), between the gate pole that first resistance (R1) and voltage stabilizing didoe (V2) are connected on the first triode (Q1) and collector electrode, the negative electrode of voltage stabilizing didoe (V2) is connected with the first resistance (R1), the anode of voltage stabilizing didoe (V2) is connected with Phototube Coupling unit (4), the anode of voltage stabilizing didoe (V2) is also connected with the collector electrode of the first triode (Q1) simultaneously, the emitter of the first triode (Q1) is connected with the gate pole of the second triode (Q2), the gate pole of the first triode (Q1) is connected with the collector electrode of the second triode (Q2).

4. a kind of switch acquisition buffer circuit according to Claims 2 or 3, it is characterized in that: described Phototube Coupling unit (4) comprises optical coupling module (V1) and the 3rd resistance (R3), optical coupling module (V1) comprises transmitting terminal and receiving terminal, the anode of the light-emitting diode of transmitting terminal is connected with the anode of voltage stabilizing didoe (V2), the negative electrode of the light-emitting diode of transmitting terminal is connected with the earth terminal of input, between the receiving terminal that 3rd resistance (R3) is connected to optical coupling module (V1) and ground, the receiving terminal of optical coupling module (V1) is connected with result output.

5. a kind of switch acquisition buffer circuit according to Claims 2 or 3, it is characterized in that: described Phototube Coupling unit (4) comprises optical coupling module (V1) and the 3rd resistance (R3), optical coupling module (V1) comprises transmitting terminal and receiving terminal, the anode of the light-emitting diode of transmitting terminal is connected with the gate pole of the second triode (Q2), the negative electrode of the light-emitting diode of transmitting terminal is connected with the emitter of the first triode (Q1), between the receiving terminal that 3rd resistance (R3) is connected to optical coupling module (V1) and ground, the receiving terminal of optical coupling module (V1) is connected with result output.

6. a kind of switch acquisition buffer circuit according to claim 4; it is characterized in that: described reverse protection unit (1) comprises counnter attack diode (V3); the anode connecting valve amount input signal of counnter attack diode (V3), the negative electrode of counnter attack diode (V3) connects current constant unit (2).

7. a kind of switch acquisition buffer circuit according to claim 4; it is characterized in that: described reverse protection unit (1) comprises counnter attack diode (V3); the negative electrode of counnter attack diode (V3) connects ground, and the anode of counnter attack diode (V3) connects Phototube Coupling unit (4).

8. a kind of switch acquisition buffer circuit according to claim 5; it is characterized in that: described reverse protection unit (1) comprises counnter attack diode (V3); the anode connecting valve amount input signal of counnter attack diode (V3), the negative electrode of counnter attack diode (V3) connects current constant unit (2).

9. a kind of switch acquisition buffer circuit according to claim 5; it is characterized in that: described reverse protection unit (1) comprises counnter attack diode (V3); the negative electrode of counnter attack diode (V3) connects ground, and the anode of counnter attack diode (V3) connects Phototube Coupling unit (4).

10. according to claim 2,3, a kind of switch acquisition buffer circuit in 6-9 described in arbitrary claim, it is characterized in that: the voltage V between the gate pole of described first triode (Q1) and collector electrode _bCbetween 0V to the input voltage and the difference of threshold voltage of switch acquisition buffer circuit.

11. a kind of switch acquisition buffer circuits according to claim 10, is characterized in that: the threshold voltage of described switch acquisition buffer circuit is the conducting voltage sum of the conduction voltage drop of counnter attack diode (V3), the second triode (Q2) voltage between emitter and collector electrode, the puncture voltage of voltage stabilizing didoe (V2) and the light-emitting diode of optical coupling module (V1) transmitting terminal.