CN106706993B - Optocoupler current detection circuit - Google Patents
Optocoupler current detection circuit Download PDFInfo
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- CN106706993B CN106706993B CN201710051109.1A CN201710051109A CN106706993B CN 106706993 B CN106706993 B CN 106706993B CN 201710051109 A CN201710051109 A CN 201710051109A CN 106706993 B CN106706993 B CN 106706993B
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/24—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using light-modulating devices
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Abstract
The invention discloses an optocoupler current detection circuit, which comprises: the device comprises a current detection unit, an optocoupler negative feedback unit and an inverting amplification unit, wherein the input end of the current detection unit is used as the input end of an optocoupler current detection circuit, and the output end of the inverting amplification unit is used as the output end of the optocoupler current detection circuit; the current detection unit, the optocoupler negative feedback unit and the inverting amplification unit are sequentially connected. The technical scheme uses the photoelectric coupler in the current detection unit, avoids using a high-resistance resistor, and ensures that the circuit cannot influence the accuracy of circuit detection due to the instability of the high-resistance resistor in a high-temperature and high-humidity severe environment. In addition, a negative feedback circuit is formed by utilizing the photoelectric coupler, and the automatic adjustment function is started, so that the detection result is stable and balanced.
Description
Technical Field
The invention relates to the field of current detection, in particular to an optocoupler current detection circuit.
Background
In laser printer systems it is often necessary to detect the output current level of the high voltage power supply to adjust the analog signal that it requires. Because the output current in the high-voltage circuit is detected, if a differential current detection circuit is used, the positive and negative output ends of the differential operational amplifier can not use resistors with high resistance to limit the input current of the positive and negative output ends and obtain smaller output voltage signals, and the higher the voltage of the circuit connected to the detection point is, the larger the resistance value of the resistor is needed. However, the resistance of the resistor with a high resistance value changes after a long time under a high-temperature and high-humidity environment. If the temperature characteristics of the positive and negative resistors are inconsistent, the detected analog signal results will be changed when the change degrees are different, and the printer is likely to malfunction; the change is irreversible, that is, when the resistance with high resistance changes, the resistance is transferred from the environment with high temperature and high humidity to the environment with normal temperature and high humidity, and the changed resistance cannot be restored to the original resistance. The high-resistance resistor is particularly easy to be influenced by high-temperature and humid environments due to process reasons, so that the resistance is changed.
As shown in FIG. 1, the conventional current detection circuit schematic diagram is shown, the sampling resistors R1, R2, R3 and R4 are sampled and input into the operational amplifier, and the voltage at the current detection position is negative high voltage signal-1350V, and meanwhile, the positive input end of the operational amplifier is connected with the bias voltage of +0.39V, so that the sampling resistors R1, R2, R3 and R4 need to have large values, otherwise, the circuit cannot work normally, and the larger the value of the negative high voltage signal is, the corresponding sampling resistors R1, R2, R3 and R4 are correspondingly increased. However, because of the high-resistance resistor, when the power supply works for a long time and is in a high-temperature and high-humidity environment, the resistance of the high-resistance resistor is poor in stability in a severe environment due to a process, and if the variation amplitude of the sampling resistors R1 and R2 is inconsistent with the amplitude of the sampling resistors R3 and R4, the voltage of the detection result Vout output by the operational amplifier is easy to drift on the original basis.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides an optocoupler current detection circuit.
The aim of the invention is realized by the following technical scheme:
an optocoupler current detection circuit comprising: the device comprises a current detection unit, an optocoupler negative feedback unit and an inverting amplification unit, wherein the input end of the current detection unit is used as the input end of the optocoupler current detection circuit, and the output end of the inverting amplification unit is used as the output end of the optocoupler current detection circuit;
the current detection unit, the optocoupler negative feedback unit and the inverting amplification unit are sequentially connected.
In one embodiment, the current detection unit includes: the LED current detection circuit comprises a first photoelectric coupler ISO1, a first diode D1, a first resistor R1, a first sampling resistor R2 and a second sampling resistor R3, wherein the anode of a light emitting diode of the first photoelectric coupler ISO1 is used as the input end of the current detection unit, one end of the first sampling resistor R2 is used as the first output end of the current detection unit, and the second sampling resistor R3 is used as the second output end of the current detection unit;
the cathode of the light-emitting diode of the first photoelectric coupler ISO1 is connected with one end of the first resistor R1;
the first diode D1 is reversely connected in parallel with the light emitting diode of the first photoelectric coupler ISO 1;
the collector of the phototriode of the first photoelectric coupler ISO1 is connected with a power supply Vcc, and the emitter is connected with one end of the first sampling resistor R2;
the other end of the first sampling resistor R2 is connected to the ground GND;
one end of the second sampling resistor R3 is connected to the ground GND.
In one embodiment, the current detection unit further includes: and one end of the first capacitor C1 is connected with the cathode of the first diode D1, and the other end of the first capacitor C1 is connected with one end of the first resistor R1.
In one embodiment, the current detection unit further includes: and the second capacitor C2 is connected in parallel with the first sampling resistor R2.
In one embodiment, the optocoupler negative feedback unit includes: the system comprises a first operational amplifier U1A and a second photoelectric coupler ISO2, wherein the positive phase input end of the first operational amplifier U1A is used as a first input end of the optical coupler negative feedback unit, the reverse phase input end of the first operational amplifier U1A is used as a second input end of the optical coupler negative feedback unit, and the cathode of a light emitting diode of the second photoelectric coupler ISO2 is used as an output end of the optical coupler negative feedback unit;
the non-inverting input end of the first operational amplifier U1A is connected with one end of the first sampling resistor R2, and the inverting input end of the first operational amplifier U1A is connected with one end of the second sampling resistor R3;
the output end of the first operational amplifier U1A is connected with the anode of the light-emitting diode of the second photoelectric coupler ISO 2;
the power end of the first operational amplifier is connected with a power supply Vcc, and the ground end of the first operational amplifier is connected with a ground GND;
the collector of the phototriode of the second photoelectric coupler ISO2 is connected with the power supply Vcc, and the emitter is connected with the inverting input end of the first operational amplifier U1A.
In one embodiment, the optocoupler negative feedback unit further includes: and one end of the third capacitor C3 is connected with the inverting input end of the first operational amplifier U1A, and the other end of the third capacitor C3 is connected with the output end of the first operational amplifier.
In one embodiment, the optocoupler negative feedback unit further includes: and one end of the fourth capacitor C4 is connected to the power end of the first operational amplifier U1A, and the other end of the fourth capacitor C4 is connected to the ground GND.
In one embodiment, the inverting amplification unit includes: a fourth resistor R4, a fifth resistor R5, a sixth resistor R6 and a second operational amplifier U1B, wherein one end of the fourth resistor R4 is used as a first input end of the inverting amplifying unit, one end of the fifth resistor R5 is used as a second input end of the inverting amplifying unit, and an output end of the second operational amplifier U1B is used as an output end of the inverting amplifying unit;
one end of the fourth resistor R4 is connected to the cathode of the light emitting diode of the second photoelectric coupler ISO2, and the other end of the fourth resistor R is connected to the inverting input end of the second operational amplifier U1B;
one end of the fifth resistor R5 is connected with a bias power supply, and the other end of the fifth resistor R5 is connected with the positive end input end of the second operational amplifier U1B;
one end of the sixth resistor R6 is connected to the inverting input end of the second operational amplifier U1B, and the other end is connected to the output end of the second operational amplifier U1B.
Compared with the prior art, the technical scheme of the application has the following beneficial effects:
1. the use of the high-resistance resistor is avoided, the precision is easy to control, the detection result is accurate, the stability is stronger under the high-temperature and humid environment temperature, and the circuit is more reliable.
2. The photoelectric coupling device is used for forming a negative feedback circuit, so that the stability of detection voltage can be well maintained, and meanwhile, the influence on the photoelectric coupling device by a humid environment is small.
Drawings
FIG. 1 is a schematic diagram of a conventional current sense circuit;
fig. 2 is a schematic diagram of an optocoupler current detection circuit according to the present embodiment;
fig. 3 is a schematic diagram of an optocoupler current detection circuit in the present embodiment.
Detailed Description
In order that the invention may be readily understood, a more complete description of the invention will be rendered by reference to the appended drawings. The drawings illustrate preferred embodiments of the invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It will be understood that when an element is referred to as being "fixed to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only and are not meant to be the only embodiment.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
Referring to fig. 2, which is a circuit for detecting an optocoupler current, referring to fig. 3, the circuit includes: the current detection unit 100, the optocoupler negative feedback unit 200 and the inverting amplification unit 300, wherein the input end of the current detection unit 100 is used as the input end of the optocoupler current detection circuit, and the output end of the inverting amplification unit 300 is used as the output end of the optocoupler current detection circuit;
the current detection unit 100, the optocoupler negative feedback unit 200 and the inverting amplification unit 300 are sequentially connected.
The negative high voltage input is a reference negative high voltage input, and the detected current is input from the input end of the current detection unit to provide a detection signal.
It should be further noted that the current detection unit 100 is further connected to the high voltage output terminal, i.e., the a terminal in fig. 2.
Specifically, the current detection unit 100 includes: the LED current detection device comprises a first photoelectric coupler ISO1, a first diode D1, a first resistor R1, a first sampling resistor R2 and a second sampling resistor R3, wherein the anode of a light emitting diode of the first photoelectric coupler ISO1 is used as the input end of the current detection unit 100, one end of the first sampling resistor R2 is used as the first output end of the current detection unit 100, and the second sampling resistor R3 is used as the second output end of the current detection unit 100;
the cathode of the light-emitting diode of the first photoelectric coupler ISO1 is connected with one end of the first resistor R1;
the first diode D1 is reversely connected in parallel with the light emitting diode of the first photoelectric coupler ISO 1;
the collector of the phototriode of the first photoelectric coupler ISO1 is connected with a power supply Vcc, and the emitter is connected with one end of the first sampling resistor R2;
the other end of the first sampling resistor R2 is connected to the ground GND;
one end of the second sampling resistor R3 is connected to the ground GND.
The first diode D1 is provided to protect the first photo coupler ISO1.
The first resistor R1 is a voltage dividing resistor, which prevents the light emitting diode of the first photocoupler ISO1 from being damaged due to excessive voltage, and protects the light emitting diode.
Further, the current detection unit 100 further includes: and one end of the first capacitor C1 is connected with the cathode of the first diode D1, and the other end of the first capacitor C1 is connected with one end of the first resistor R1.
Further, the current detection unit 100 further includes: and the second capacitor C2 is connected in parallel with the first sampling resistor R2.
It should be noted that, the first capacitor C1 and the second capacitor C2 are filter capacitors, so as to eliminate clutter interference.
Specifically, the optocoupler negative feedback unit 200 includes: a first operational amplifier U1A and a second optocoupler ISO2, wherein a positive phase input end of the first operational amplifier U1A is used as a first input end of the optocoupler negative feedback unit 200, an opposite phase input end is used as a second input end of the optocoupler negative feedback unit 200, and a cathode of a light emitting diode of the second optocoupler ISO2 is used as an output end of the optocoupler negative feedback unit 200;
the non-inverting input end of the first operational amplifier U1A is connected with one end of the first sampling resistor R2, and the inverting input end of the first operational amplifier U1A is connected with one end of the second sampling resistor R3;
the output end of the first operational amplifier U1A is connected with the anode of the light-emitting diode of the second photoelectric coupler ISO 2;
the power end of the first operational amplifier is connected with a power supply Vcc, and the ground end of the first operational amplifier is connected with a ground GND;
the collector of the phototriode of the second photoelectric coupler ISO2 is connected with the power supply Vcc, and the emitter is connected with the inverting input end of the first operational amplifier U1A.
It should be noted that, the emitter of the phototransistor of the second optocoupler ISO2 is connected to the inverting input terminal of the first operational amplifier U1A, which plays a role in negative feedback of current, and a voltage drop is generated in the second sampling resistor R3, and the voltage of the output terminal of the first operational amplifier U1A follows the voltage of the positive input terminal through the negative feedback, so as to play a role in automatic adjustment, thereby restraining the voltage change of the output terminal and stabilizing the voltage of the output terminal.
Further, the optocoupler negative feedback unit 200 further includes: and one end of the third capacitor C3 is connected with the inverting input end of the first operational amplifier U1A, and the other end of the third capacitor C3 is connected with the output end of the first operational amplifier.
Further, the optocoupler negative feedback unit 200 further includes: and one end of the fourth capacitor C4 is connected to the power end of the first operational amplifier U1A, and the other end of the fourth capacitor C4 is connected to the ground GND.
The third capacitor C3 is a deep negative feedback function and can stabilize the output characteristic of the circuit, and the fourth capacitor C4 is a filtering function.
The power supply Vcc is a 25V power supply.
Specifically, the inverting amplification unit 300 includes: a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a second operational amplifier U1B, wherein one end of the fourth resistor R4 is used as a first input end of the inverting amplifying unit 300, one end of the fifth resistor R5 is used as a second input end of the inverting amplifying unit 300, and an output end of the second operational amplifier U1B is used as an output end of the inverting amplifying unit 300;
one end of the fourth resistor R4 is connected to the cathode of the light emitting diode of the second photoelectric coupler ISO2, and the other end of the fourth resistor R is connected to the inverting input end of the second operational amplifier U1B;
one end of the fifth resistor R5 is connected with a bias power supply, and the other end of the fifth resistor R5 is connected with the positive end input end of the second operational amplifier U1B;
one end of the sixth resistor R6 is connected to the inverting input end of the second operational amplifier U1B, and the other end is connected to the output end of the second operational amplifier U1B.
The bias power supply is a 0.39V power supply, and provides a bias voltage for the second operational amplifier U1B.
It should be further noted that, in the optocoupler current detection circuit, the first optocoupler ISO1 and the second optocoupler ISO2 should be close to each other as far as possible in layout, so that the first optocoupler ISO1 and the second optocoupler ISO2 can maintain a consistent ambient temperature in a high-temperature and high-humidity environment, so that no obvious difference occurs between the characteristics of the first optocoupler ISO1 and the second optocoupler ISO2, and in addition, due to the negative feedback, the output detection result can maintain stable balance, and the stability and reliability of the circuit are improved.
The above embodiments represent only a few embodiments of the present invention, which are described in more detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (6)
1. An optocoupler current detection circuit, comprising: the device comprises a current detection unit, an optocoupler negative feedback unit and an inverting amplification unit, wherein the input end of the current detection unit is used as the input end of the optocoupler current detection circuit, and the output end of the inverting amplification unit is used as the output end of the optocoupler current detection circuit;
the current detection unit, the optocoupler negative feedback unit and the inverting amplification unit are sequentially connected, a power supply is electrically connected with the current detection unit and the optocoupler negative feedback unit, and the power supply Vcc is a 25V power supply;
the current detection unit includes: the LED current detection circuit comprises a first photoelectric coupler ISO1, a first diode D1, a first resistor R1, a first sampling resistor R2 and a second sampling resistor R3, wherein the anode of a light emitting diode of the first photoelectric coupler ISO1 is used as the input end of the current detection unit, one end of the first sampling resistor R2 is used as the first output end of the current detection unit, and the second sampling resistor R3 is used as the second output end of the current detection unit;
the cathode of the light-emitting diode of the first photoelectric coupler ISO1 is connected with one end of the first resistor R1;
the first diode D1 is reversely connected in parallel with the light emitting diode of the first photoelectric coupler ISO 1;
the collector of the phototriode of the first photoelectric coupler ISO1 is connected with a power supply Vcc, and the emitter is connected with one end of the first sampling resistor R2;
the other end of the first sampling resistor R2 is connected to the ground GND;
one end of the second sampling resistor R3 is connected to the ground GND;
the optocoupler negative feedback unit comprises: the system comprises a first operational amplifier U1A and a second photoelectric coupler ISO2, wherein the positive phase input end of the first operational amplifier U1A is used as a first input end of the optical coupler negative feedback unit, the reverse phase input end of the first operational amplifier U1A is used as a second input end of the optical coupler negative feedback unit, and the cathode of a light emitting diode of the second photoelectric coupler ISO2 is used as an output end of the optical coupler negative feedback unit;
the non-inverting input end of the first operational amplifier U1A is connected with one end of the first sampling resistor R2, and the inverting input end of the first operational amplifier U1A is connected with one end of the second sampling resistor R3;
the output end of the first operational amplifier U1A is connected with the anode of the light-emitting diode of the second photoelectric coupler ISO 2;
the power end of the first operational amplifier is connected with a power supply Vcc, and the ground end of the first operational amplifier is connected with a ground GND;
the collector of the phototriode of the second photoelectric coupler ISO2 is connected with the power supply Vcc, and the emitter is connected with the inverting input end of the first operational amplifier U1A.
2. The optocoupler current detection circuit of claim 1, wherein the current detection unit further comprises: and one end of the first capacitor C1 is connected with the cathode of the first diode D1, and the other end of the first capacitor C1 is connected with one end of the first resistor R1.
3. The optocoupler current detection circuit of claim 2, wherein the current detection unit further comprises: and the second capacitor C2 is connected in parallel with the first sampling resistor R2.
4. The optocoupler current detection circuit of claim 1, wherein the optocoupler negative feedback unit further comprises: and one end of the third capacitor C3 is connected with the inverting input end of the first operational amplifier U1A, and the other end of the third capacitor C3 is connected with the output end of the first operational amplifier.
5. The optocoupler current detection circuit of claim 4, wherein the optocoupler negative feedback unit further comprises: and one end of the fourth capacitor C4 is connected to the power end of the first operational amplifier U1A, and the other end of the fourth capacitor C4 is connected to the ground GND.
6. The optocoupler current detection circuit of claim 5, wherein the inverting amplification unit comprises: a fourth resistor R4, a fifth resistor R5, a sixth resistor R6 and a second operational amplifier U1B, wherein one end of the fourth resistor R4 is used as a first input end of the inverting amplifying unit, one end of the fifth resistor R5 is used as a second input end of the inverting amplifying unit, and an output end of the second operational amplifier U1B is used as an output end of the inverting amplifying unit;
one end of the fourth resistor R4 is connected to the cathode of the light emitting diode of the second photoelectric coupler ISO2, and the other end of the fourth resistor R is connected to the inverting input end of the second operational amplifier U1B;
one end of the fifth resistor R5 is connected with a bias power supply, and the other end of the fifth resistor R5 is connected with the positive end input end of the second operational amplifier U1B;
one end of the sixth resistor R6 is connected to the inverting input end of the second operational amplifier U1B, and the other end is connected to the output end of the second operational amplifier U1B.
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CN108152557A (en) * | 2017-12-26 | 2018-06-12 | 常州三立精图光电有限公司 | Sample circuit is isolated in a kind of feedback current |
CN110967540B (en) * | 2019-12-12 | 2022-03-25 | 中国电子科技集团公司第四十四研究所 | Isolated linear detection circuit with adjustable transmission coefficient and module comprising same |
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CN101923111A (en) * | 2009-06-11 | 2010-12-22 | 北京中纺锐力机电有限公司 | Isolation detection circuit of DC bus voltage |
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