阅读说明：本技术 一种基于光耦的模拟信号隔离电路 (Analog signal isolation circuit based on optocoupler ) 是由 杨培 仲启亮 张翔 于 2019-10-25 设计创作，主要内容包括：本发明涉及一种基于光耦的模拟信号隔离电路,属于电子线路技术领域,解决包括负电压的交直流模拟信号的隔离传递问题,电路包括用于滤波和电压幅度压缩的滤波与压缩电路,用于将压缩后的模拟信号升压到正电压的升压电路,基于光耦的隔离电路,用于将隔离电路输出信号进行放大滤波后进行的模拟信号恢复的放大滤波电路。本发明实现了包括正、负电压的交、直流模拟信号的隔离传递；电路线性度较好,带宽较高；并且电路简单,组成器件均为常用器件,成本低,便于推广,经济价值高。(The invention relates to an analog signal isolation circuit based on an optical coupler, which belongs to the technical field of electronic circuits and solves the problem of isolated transmission of alternating current and direct current analog signals including negative voltage. The invention realizes the isolated transmission of AC and DC analog signals including positive and negative voltages; the circuit linearity is good, and the bandwidth is high; and the circuit is simple, the components are common devices, the cost is low, the popularization is convenient, and the economic value is high.)

1. An optical coupler-based analog signal isolation circuit is characterized by comprising a filtering and compressing circuit, a booster circuit, an isolation circuit and an amplifying and filtering circuit;

the filtering and compressing circuit is used for inputting an analog signal V_iAfter filtering, amplitude compression is carried out according to a set compression ratio, and an analog signal V after amplitude compression is output_1i；

The booster circuit is used for compressing the amplitude-compressed analog signal V_1iBoosting to obtain positive voltage signal V_2i；

The isolation circuit adopts an optical coupler for signal isolation and is used for carrying out signal isolation on an input positive voltage signal V according to a set transmission ratio_2iCarrying out isolated transmission and outputting an isolated positive voltage signal V_3i；

The amplifying and filtering circuit is used for amplifying the isolated positive voltage signal V_3iAfter voltage reduction, amplification and filtering, the isolated analog signal V is output_o。

2. The analog signal isolation circuit of claim 1, wherein the input analog signal V_iThe alternating current signal with the amplitude within a set range and containing negative voltage is included.

3. The analog signal isolation circuit of claim 1 or 2, wherein the set compression ratio is used to match the input analog signal V_iThe amplitude range of a working linear region of an optical coupler in the isolation circuit; making the amplitude-compressed analog signal V_1iThe amplitude range of the optical coupler is not more than the amplitude range of the optical coupler working linear region.

4. The analog signal isolation circuit of claim 3, wherein the filtering and compressing circuit comprises resistors R1, R2, R3, R4, a capacitor C1 and an operational amplifier chip U1;

the resistor R1 and the capacitor C1 are connected in series and then are connected in parallel with the resistor R2 on the analog signal V_iAnd ground GND 1;

the connecting end of the resistor R1 and the capacitor C1 is connected with the pin 5 of the non-inverting input end of the operational amplifier chip U1, and the pin 6 of the inverting input end of the operational amplifier chip U1 is connected with the pin 7 of the output end;

resistors R3 and R4 are connected in series between the pin 7 at the output end of the operational amplifier chip U1 and the ground wire GND 1;

the connection end of the resistor R3 and the resistor R4 outputs an analog signal V after amplitude compression_1i；

The set compression ratio is R4: (R3+ R4).

5. The analog signal isolation circuit of claim 3, wherein the boost circuit comprises an operational amplifier AD620AR, the operational amplifier AD620AR has a 2-pin connected to ground through a resistor R5 and a 3-pin connected to the amplitude-compressed analog signal V_1iA 4-pin is connected with a power supply Vss, and a 5-pin is connected with a reference positive voltage V_ref1The pin 7 is connected with a power supply Vcc, and the pin 6 outputs a positive voltage signal V_2i(ii) a Implementing the same-direction addition operation V_2i＝V_1i+V_ref1。

6. The analog signal isolation circuit of claim 3, wherein the isolation circuit comprises an operational amplifier chip U3, an optical coupler chip U4, resistors R7, R8, R9, and R10; the optocoupler chip U4 is HCNR 201-300;

the non-inverting input end of the operational amplifier chip U3 is connected with a positive voltage signal V through a resistor R7_2iThe reverse input end is connected with a ground wire GND1 through a resistor R9, and the output end of the operational amplifier chip U3 is connected with a pin 2 of the optocoupler chip U4 through a resistor R8;

a pin 1 of the optocoupler chip U4 is connected with a ground wire GND1, a pin 3 is connected with a power supply Vcc1 of the operational amplifier chip U3, a pin 4 is connected with a ground wire GND1 through a resistor R9, a pin 6 is connected with a power supply Vcc2, and a pin 5 is connected with a ground wire GND2 through a resistor R10; the connection end of the 5 pin and the resistor R10 outputs the isolated positive voltage signal V_3i；

The power supply Vcc1 and the ground GND1 are isolated from the power supply Vcc2 and the ground GND 2;

the set transmission ratio is R9: and R10.

7. The analog signal isolation circuit of claim 6, wherein the R9 and R10 have equal resistance values, the error of the resistance values is controlled within 1%, and the power sources Vcc1 and Vcc2 are equal, so that the transmission ratio of the isolation circuit is 1: 1.

8. The analog signal isolation circuit of claim 3, wherein the amplifying and filtering circuit comprises operational amplifier chips U5, U6, resistors R11, R12, R13, R14, R15, R16, a capacitor C4;

the inverting input end of the operational amplifier chip U5 is connected with the isolated positive voltage signal V through a resistor R11_3iA reference voltage V connected via a resistor R12_ref2The output end of the operational amplifier chip U5 is connected through a resistor R13;

the resistor R14 and the capacitor C4 are connected between the output end of the operational amplifier chip U5 and a ground wire GND2 in series;

the inverting input end of the operational amplifier chip U6 is connected with the connecting end of a resistor R14 and a capacitor C4 through a resistor R15, and a resistor R16 is connected between the non-inverting input end and the output end of the operational amplifier chip U6;

the output end of the operational amplifier chip U6 outputs an isolated analog signal V_o。

9. The analog signal isolation circuit of claims 4-8,

transmission ratio of the circuit

10. The analog signal isolation circuit of claim 9,

by setting R11 ═ R12, V_ref1＝V_ref2R15 ═ R16, R13/R11 ═ R3/R4+1, and R11 ═ R12, and the transmission ratio K of the circuit was made to be 1, resulting in an analog signal isolation circuit with equal-ratio transmission.

Technical Field

The invention relates to the technical field of electronic circuits, in particular to an optical coupler-based analog signal isolation circuit.

Background

The isolation scheme of analog signals commonly used in the current circuit generally adopts the forms of an isolation transformer chip and an optical coupler chip. However, the isolation circuit for simulating signals by adopting the isolation transformer has the defects of low resolution, low bandwidth and large volume, and has larger zero offset; however, the existing isolation circuit for analog signals by using the optocoupler chip can only isolate positive voltage signals generally, i.e. the voltages before and after isolation are both positive signals, which limits the application of isolated transmission of alternating current and direct current analog signals including negative voltage.

Disclosure of Invention

In view of the above analysis, the present invention aims to provide an optical coupler-based analog signal isolation circuit, which solves the problem of isolated transmission of ac and dc analog signals including negative voltage.

The purpose of the invention is mainly realized by the following technical scheme:

the invention discloses an analog signal isolation circuit based on an optocoupler, which comprises a filtering and compressing circuit, a booster circuit, an isolation circuit and an amplifying and filtering circuit;

the filtering and compressing circuit is used for inputting an analog signal V_iAfter filtering, amplitude compression is carried out according to a set compression ratio, and an analog signal V after amplitude compression is output_1i；

The booster circuit is used for compressing the amplitude-compressed analog signal V_1iBoosting to obtain positive voltage signal V_2i；

The isolation circuit adopts an optical coupler for signal isolation and is used for carrying out signal isolation on an input positive voltage signal V according to a set transmission ratio_2iCarrying out isolated transmission and outputting an isolated positive voltage signal V_3i；

The amplifying and filtering circuit is used for amplifying the isolated positive voltage signal V_3iAfter voltage reduction, amplification and filtering, the isolated analog signal V is output_o。

Further, the input analog signal V_iThe alternating current signal with the amplitude within a set range and containing negative voltage is included.

Further, the set compression ratio is used for matching the input analog signal V_iThe amplitude range of a working linear region of an optical coupler in the isolation circuit; making the amplitude-compressed analog signal V_1iThe amplitude range of the optical coupler is not more than the amplitude range of the optical coupler working linear region.

Further, the filtering and compressing circuit comprises resistors R1, R2, R3, R4, a capacitor C1 and an operational amplifier chip U1;

the resistor R1 and the capacitor C1 are connected in series and then are connected with the resistorR2 is connected in parallel to the analog signal V_iAnd ground GND 1;

the connecting end of the resistor R1 and the capacitor C1 is connected with the pin 5 of the non-inverting input end of the operational amplifier chip U1, and the pin 6 of the inverting input end of the operational amplifier chip U1 is connected with the pin 7 of the output end;

resistors R3 and R4 are connected in series between the pin 7 at the output end of the operational amplifier chip U1 and the ground wire GND 1;

the connection end of the resistor R3 and the resistor R4 outputs an analog signal V after amplitude compression_1i；

The set compression ratio is R4: (R3+ R4).

Furthermore, the boost circuit comprises an operational amplifier AD620AR, wherein 2 pins of the operational amplifier AD620AR are grounded through a resistor R5, and 3 pins are connected with an analog signal V after amplitude compression_1iA 4-pin is connected with a power supply Vss, and a 5-pin is connected with a reference positive voltage V_ref1The pin 7 is connected with a power supply Vcc, and the pin 6 outputs a positive voltage signal V_2i(ii) a Implementing the same-direction addition operation V_2i＝V_1i+V_ref1。

Further, the isolation circuit comprises an operational amplifier chip U3, an optical coupler chip U4, a resistor R7, a resistor R8, a resistor R9 and a resistor R10; the optocoupler chip U4 is HCNR 201-300;

the non-inverting input end of the operational amplifier chip U3 is connected with a positive voltage signal V through a resistor R7_2iThe reverse input end is connected with a ground wire GND1 through a resistor R9, and the output end of the operational amplifier chip U3 is connected with a pin 2 of the optocoupler chip U4 through a resistor R8;

a pin 1 of the optocoupler chip U4 is connected with a ground wire GND1, a pin 3 is connected with a power supply Vcc1 of the operational amplifier chip U3, a pin 4 is connected with a ground wire GND1 through a resistor R9, a pin 6 is connected with a power supply Vcc2, and a pin 5 is connected with a ground wire GND2 through a resistor R10; the connection end of the 5 pin and the resistor R10 outputs the isolated positive voltage signal V_3i；

The power supply Vcc1 and the ground GND1 are isolated from the power supply Vcc2 and the ground GND 2;

the set transmission ratio is R9: and R10.

Furthermore, the resistance values of the R9 and the R10 are equal, the resistance value error is controlled within 1%, and power supplies Vcc1 and Vcc2 are equal, so that the transmission ratio of the isolation circuit is 1: 1.

Further, the amplifying and filtering circuit comprises operational amplifier chips U5, U6, resistors R11, R12, R13, R14, R15, R16 and a capacitor C4;

the inverting input end of the operational amplifier chip U5 is connected with the isolated positive voltage signal V through a resistor R11_3iA reference voltage V connected via a resistor R12_ref2The output end of the operational amplifier chip U5 is connected through a resistor R13;

the resistor R14 and the capacitor C4 are connected between the output end of the operational amplifier chip U5 and a ground wire GND2 in series;

the inverting input end of the operational amplifier chip U6 is connected with the connecting end of a resistor R14 and a capacitor C4 through a resistor R15, and a resistor R16 is connected between the non-inverting input end and the output end of the operational amplifier chip U6;

the output end of the operational amplifier chip U6 outputs an isolated analog signal V_o。

Further, the transmission ratio of the circuit

Further, by setting R11 ═ R12, V_ref1＝V_ref2R15 ═ R16, R13/R11 ═ R3/R4+1, and R11 ═ R12, and the transmission ratio K of the circuit was made to be 1, resulting in an analog signal isolation circuit with equal-ratio transmission.

The invention has the following beneficial effects:

1. the invention realizes the isolated transmission of AC and DC analog signals including positive and negative voltages;

2. the method has the advantages that the input analog signal is subjected to amplitude compression, so that an optical coupler used for isolation transmission works in a linear region, the signal transmission linearity is good, and the bandwidth is high;

3. the transmission proportion of the circuit is adjustable;

4. the circuit is simple, the components are common devices, the cost is low, the popularization is convenient, and the economic value is high.

Drawings

The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.

FIG. 1 is a schematic block diagram of an analog signal isolation circuit in an embodiment of the invention;

FIG. 2 is a schematic diagram of the filtering and compressing circuit according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a boost circuit according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of an isolation circuit connection according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of the connection of the amplifying and filtering circuit according to the embodiment of the present invention;

fig. 6 is a general connection diagram of an analog signal isolation circuit according to an embodiment of the present invention.

Detailed Description

The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form a part hereof, and which together with the embodiments of the invention serve to explain the principles of the invention.

The embodiment discloses an optical coupler-based analog signal isolation circuit, which comprises a filtering and compressing circuit, a booster circuit, an isolation circuit and an amplifying and filtering circuit which are sequentially connected as shown in fig. 1;

the filtering and compressing circuit is used for inputting an analog signal V_iAfter filtering, amplitude compression is carried out according to a set compression ratio, and an analog signal V after amplitude compression is output_1iTo the boost circuit;

the booster circuit is used for boosting the amplitude-compressed alternating current analog signal V_1iBoosting to obtain positive voltage signal V_2iOutputting to an isolation circuit;

the isolation circuit adopts an optical coupler for signal isolation and is used for carrying out signal isolation on an input positive voltage signal V according to a set transmission ratio_2iCarrying out isolated transmission and outputting an isolated positive voltage signal V_3iTo an amplifying and filtering circuit;

the amplifying and filteringA wave circuit for applying an isolated positive voltage signal V_3iAfter voltage reduction, amplification and filtering, the isolated analog signal V is output_o。

Specifically, the input analog signal V of the present embodiment_iThe signal is not limited to a direct current positive voltage signal, and can be an alternating current analog signal and a direct current analog signal which have the amplitude within a set range and comprise positive voltage and negative voltage.

Due to the input analogue signal V_iMay exceed the linear working range of the optical coupler in the isolating circuit, thus affecting the normal operation of the isolating circuit, and therefore, the filtering and compressing circuit will couple the input analog signal V_iIs compressed according to a set compression ratio for matching the input analog signal V_iThe amplitude range of a working linear region of an optical coupler in the isolation circuit; making the amplitude-compressed analog signal V_1iThe amplitude range of the optical coupler is not more than the amplitude range of the optical coupler working linear region.

As shown in fig. 2, the filtering and compressing circuit includes resistors R1, R2, R3, R4, a capacitor C1 and an operational amplifier chip U1;

the resistors R1 and R2 and the capacitor C1 form an RC low-pass filter circuit for filtering an input analog signal V_iOf the noise signal. The specific circuit connection includes:

the resistor R1 and the capacitor C1 are connected in series and then are connected in parallel with the resistor R2 on the analog signal V_iAnd ground GND 1; the connection end of the resistor R1 and the capacitor C1 is used as a filtering output end to output a filtered analog signal; the low-pass filters with different bandwidths can be set by setting the resistance-capacitance parameters of the resistors R1 and R2 and the capacitor C1.

The operational amplifier chip U1 is connected into a voltage follower circuit for improving the driving capability of the circuit. The specific circuit connection is that the connecting end of the resistor R1 and the capacitor C1 is connected with the pin 5 of the non-inverting input end of the operational amplifier chip U1, and the pin 6 of the inverting input end of the operational amplifier chip U1 is connected with the pin 7 of the output end; the pin 7 of the output end is the output end of the voltage follower circuit;

and the resistor R3 and the resistor R4 are connected to form a proportional circuit, and are used for carrying out proportional extraction on the voltage output by the voltage follower circuit so as to realize voltage amplitude compression. The specific circuit connection includes:

resistors R3 and R4 are connected in series between the pin 7 at the output end of the operational amplifier chip U1 and the ground wire GND 1; the connection end of the resistor R3 and the resistor R4 outputs an analog signal V after amplitude compression_1i；

By setting the resistance parameters of R3 and R4, the compression ratio of the circuit is set to be R4: (R3+ R4).

Due to input of analogue signal V_iPossibly an ac signal comprising a negative voltage, the analog signal V being filtered and compressed_1iThe negative voltage is also included, and the circuit at the later stage can only isolate the positive voltage signal, so that a boosting circuit is added in the circuit to eliminate the negative voltage. The booster circuit realizes the homodromous addition operation V_2i＝V_1i+V_ref1By addition in the same direction of V_2iIs a positive voltage signal, wherein V_ref1For reference to positive voltage, greater than V_1iOf the first and second electrodes.

As shown in fig. 3, the boost circuit includes an operational amplifier AD620AR, where the 2 pin of the operational amplifier AD620AR is grounded through a resistor R5, and the 3 pin is connected to the analog signal V after amplitude compression_1iA 4-pin is connected with a power supply Vss, and a 5-pin is connected with a reference positive voltage V_ref1The pin 7 is connected with a power supply Vcc, and the pin 6 outputs a positive voltage signal V_2iTo implement the homodromous addition operation V_2i＝V_1i+V_ref1。

As shown in fig. 4, the isolation circuit includes an operational amplifier chip U3, an optical coupler chip U4, resistors R7, R8, R9, and R10; the optocoupler chip U4 is HCNR 201-300;

the non-inverting input end of the operational amplifier chip U3 is connected with a positive voltage signal V through a resistor R7_2iThe reverse input end is connected with a ground wire GND1 through a resistor R9, and the output end of the operational amplifier chip U3 is connected with a pin 2 of the optocoupler chip U4 through a resistor R8;

a pin 1 of the optocoupler chip U4 is connected with a ground wire GND1, a pin 3 is connected with a power supply Vcc1 of the operational amplifier chip U3, a pin 4 is connected with a ground wire GND1 through a resistor R9, a pin 6 is connected with a power supply Vcc2, and a pin 5 is connected with a ground wire GND2 through a resistor R10; the connection end of the 5 pin and the resistor R10 outputs the isolated positive voltage signal V_3i

The power supply Vcc1 and the ground GND1 are isolated from the power supply Vcc2 and the ground GND 2;

the set transmission ratio is R9: and R10.

Switching in a positive voltage signal V at the isolating circuit_2iThen, the output end of the operational amplifier chip U3 outputs positive voltage to pin 2 of the optical coupling chip U4 through a resistor R8, and a light emitting diode connected with pin 2 and pin 1 in the forward direction in the optical coupling chip U4 is connected to a ground wire GND1 to form a path, so that the light emitting diode emits light; the light-emitting diode of the optical coupling chip U4 emits light, so that the light-receiving diodes connected with the 4 pin and the 3 pin in the forward direction and the light-receiving diodes connected with the 5 pin and the 6 pin in the forward direction in the optical coupling chip U4 are conducted, and a power supply Vcc1 is connected with the light-receiving diodes connected with the 4 pin and the 3 pin in the forward direction through the optical coupling chip U4, and a resistor R9 to a ground wire GND1 to form a passage; a power supply Vcc2 is connected with 5-pin and 6-pin light-receiving diodes, a resistor R10 and a ground wire GND2 in a forward direction through the interior of an optocoupler chip U4 to form a passage; the voltage drop of the resistor R9 and the accessed positive voltage signal V_2iIn a consistent manner, the voltage drop across resistor R10 is determined by the ratio of the resistances of resistors R9 and R10 and the size of power supplies Vcc1 and Vcc 2.

When the isolation circuit is used for carrying out isolation transmission on input signals in a ratio of 1:1, power supplies Vcc1 and Vcc2 are equal, the resistance values of R9 and R10 are equal, and the resistance value error is controlled within 1%.

As shown in fig. 5, the amplifying and filtering circuit includes operational amplifier chips U5, U6, resistors R11, R12, R13, R14, R15, R16, and a capacitor C4;

the resistors R11, R12, R13 and the operational amplifier chip U5 form an inverse adder circuit for adding the isolated positive voltage signal V_3iAnd carrying out inversion, proportional amplification and voltage reduction operation, and outputting an inverted voltage signal. The specific circuit connection includes: the inverting input end of the operational amplifier chip U5 is connected with the isolated positive voltage signal V through a resistor R11_3iA reference voltage V connected via a resistor R12_ref2The output end of the operational amplifier chip U5 is connected through a resistor R13; the inverse addition operation is realized as

The resistor R14 and the capacitor C4 form an RC filter circuit, and the resistance-capacitance parameters of the resistor R14 and the capacitor C4 for filtering noise in the signal can be set into low-pass filters with different bandwidths. The specific circuit connection includes: the resistor R14 and the capacitor C4 are connected in series between the output end of the operational amplifier chip U5 and the ground GND 2.

The R15, the R16 and the operational amplifier chip U6 form an inverter circuit, and the inverter circuit is used for inverting the reverse voltage signal output by the reverse adder circuit again to obtain an analog signal V_iEquidirectional, isolated and transmission ratio-adjustable analog signal V_o. The specific circuit connection includes: the inverting input end of the operational amplifier chip U6 is connected with the connecting end of a resistor R14 and a capacitor C4 through a resistor R15, and a resistor R16 is connected between the non-inverting input end and the output end of the operational amplifier chip U6; the output end of the operational amplifier chip U6 outputs an isolated analog signal V_o。

The circuit also comprises some common circuit connections, for example, the non-inverting input ends of the operational amplifier chips U5 and U6 are connected with pull-down resistors, and a filter capacitor is connected between the chip power supply and the ground wire, which does not affect the protection scope of the invention and is not described herein.

As shown in fig. 6, the circuit realizes isolated transmission of an alternating current analog signal including a negative voltage by filtering, compressing, boosting, isolating, amplifying and filtering, and the transmission ratio of the circuit is as follows:

the transmission proportion of the circuit can be changed by setting the resistance value of the resistor and the voltage value of the reference voltage.

Specifically, R11 ═ R12, V in the formula_ref1＝V_ref2R15 ═ R16, R13/R11 ═ R3/R4+1, and R11 ═ R12, resulting in an analog signal isolation circuit with a transmission ratio K of 1.

The specific parameters of each device in fig. 6 are: r1 is 510 Ω, R2 is 100K Ω, R3 is 20K Ω, R4 is 1% at 5K Ω precision, R5 is 4.99K Ω, R7 is 1K Ω, R8 is 1% at 220 Ω precision, R9 is 100K Ω essenceThe degree is 0.1%, the precision of R10 is 100K omega is 0.1%, R11 and R12 are 100K omega, R13 is 500K omega, R14 is 510 omega, R15 is 100K omega, R16 is 100K omega, and C1 and C4 are 0.01 muF; AC analog signal V with input in the range of +/-12V_iThe transmission ratio is 1, and the isolated alternating current analog signal V within the range of +/-12V is output_o。

Compared with the prior art, the optical coupler-based analog signal isolation circuit realizes the isolated transmission of alternating current and direct current analog signals including positive and negative voltages, so that the linearity of signal transmission is good, the bandwidth is high, and the transmission proportion of the circuit is adjustable; the circuit is simple, the components are common devices, the cost is low, the popularization is convenient, and the economic value is high.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.