CN1874160B - Analog signal conversion isolating device - Google Patents

Abstract

An analog signal conversion isolation device includes: a filtering circuit, an amplifying circuit, an isolation circuit and a voltage follower circuit. It can use a switch component to switch and select according to the voltage or current signal of the input end, or convert a large current input signal into a voltage source signal by a precision resistor, generate a same-level signal source output through the amplifier, and isolate external noise by the isolation circuit, and output the signal to the control end through the voltage follower circuit to realize analog signal conversion of voltage, current source signal and large current signal source, as well as ground isolation.

Description

Analog Signal Conversion Isolation Device

technical field

The present invention relates to an analog signal conversion and isolation device, in particular to an analog signal conversion and isolation device with an independent input power supply and a linear optical coupling signal isolation design, which can be applied to the simulation of voltage, current source signals and large current signal sources Signal conversion and ground isolation.

Background technique

It is very common to apply analog signal conversion to the signal control of electronic products. The traditional analog signal conversion is shown in Figure 1. It is mainly divided into voltage and current input signal sources, which are output to the control terminal (such as CPU, etc.) , the acquisition of the input signal is usually limited to 0-10V or 0-20mA, and because of the difference in input impedance, different signals need to be input separately, so that the line is limited to a single signal mode, which is not very practical.

At present, in order to realize the analog signal conversion input line can input both current signal and voltage signal, it is mainly to use the switch to select, cooperate with the OP amplifier as the amplifying circuit, and determine the input impedance according to the different signal sources to obtain the signal corresponding to the control terminal. bit. Although this can solve the problem that the line is limited to a single signal mode, the available input current signal is still very small, all in the range of several mA.

In addition, due to the common ground design of the line, there is no isolation between it and the control terminal (such as the CPU), so it will cause external noise to couple to the control terminal, and when it is applied to a large current signal input, it will fail to obtain the signal and generate The selection of R4' parts in the circuit in Figure 1, etc., so the conversion mode is usually configured through a conversion module (such as a current comparator) to form a pre-stage isolation, and convert a large signal into a smaller signal, or a current signal that can be obtained , convert the voltage to the input terminal through the resistance to achieve the isolation effect and solve the current signal input problem, but this will relatively increase the complexity and cost of the circuit design, and at the same time, the current and voltage signal input terminals cannot be shared and need to be independent configuration, it cannot be applied to both voltage and current signals.

Contents of the invention

The main purpose of the present invention is to solve the problems existing in the above-mentioned prior art. The present invention utilizes the independent and simple selection of the input source to switch the input source, and the design structure of the rear pole linear optical coupling signal isolation to improve the interference of the analog signal conversion device. Signal isolation efficiency, applicability of large current signal sources, and avoiding the need to add high-cost and complex circuits with conversion modules, thus providing an analog signal conversion isolation with simpler circuit wiring and smaller space occupation, low price but high practicability device.

In order to achieve the above object, the analog signal conversion and isolation device of the present invention is connected to the signal input terminal, and is used for analog signal conversion and grounding isolation of voltage, current and high current signal sources. The device includes:

A filter circuit, the input end of which is connected to the signal input end, and the filter circuit has a shunt resistor (R1), and the shunt resistor (R1) is a precision low-resistance high-power resistance component;

An amplifying circuit, the amplifying circuit includes an OP amplifier, a switch assembly and a plurality of resistance assemblies, the non-inverting input end of the OP amplifier is electrically connected to the output end of the filter circuit to receive the output signal of the filter circuit, and the switch assembly switch and select according to different input voltage or current signals, and output different signal source levels uniformly; the inverting input terminal and output terminal of the OP amplifier are electrically connected to the switch component, wherein the switch component can be selected is selectively connected to one of the multiple resistance components to determine the signal input-output level amplification;

An isolation circuit, which is electrically connected to the output terminal of the amplifying circuit to receive the signal of the amplifying circuit for signal conversion, and isolate the interference noise in the signal;

The voltage follower circuit outputs the isolated voltage signal in phase to the control terminal.

Description of drawings

FIG. 1 is a schematic diagram of a conventional conversion circuit.

Fig. 2 is a circuit block diagram of a specific embodiment of the present invention.

Fig. 3 is a schematic circuit diagram of a specific embodiment of the present invention.

Fig. 4 is a schematic circuit diagram of another specific embodiment of the present invention.

In the accompanying drawings, the list of parts represented by each label is as follows:

Filter circuit 1 Amplifier circuit 2

Isolation circuit 3 Voltage follower circuit 4

OP amplifier 21 switch assembly 22

Comparator 31 Analog Optocoupler 41

Divider resistor R1 Variable resistor component R7

Resistor components R2, R3, R4, R5, R6

Detailed ways

About technical content of the present invention and detailed description, now in conjunction with accompanying drawing, explain as follows:

2 and 3 are schematic diagrams of the circuit structure of the analog signal conversion and isolation device of the present invention. As shown in the figure, the analog signal conversion and isolation device of the present invention includes: a filter circuit 1, an amplifier circuit 2, an isolation circuit 3 and a voltage follower circuit 4 to form a signal that can be applied to voltage, current source signals and large current signals. Source analog signal conversion and ground isolation analog signal conversion isolation device, the device has a simpler circuit and reduces wiring space, its price is low but its practicability is high.

The filter circuit 1 is connected to an independent input power supply signal to reduce the output ripple. The filter circuit 1 has a shunt resistor R1. The shunt resistor R1 is a precision low-resistance high-power resistor component. When a large current signal source is input, Most of the high-current signal sources can be shunted away, so that the present invention can be applied to the analog signal conversion of several ampere (A) currents, thus solving the problem that the available input current signal is limited to several mA.

The amplifying circuit 2 is connected to the output end of the filter circuit 1, and has an OP amplifier 21 and a switch assembly 22 for generating the same-level signal source output, and the OP amplifier 21 is connected to the filter circuit 1 to receive the output signal V2 of the filter circuit 1, And the switch component (Switch) 22 performs switching selection according to the input terminal voltage and current signal, cooperates with the resistance component R2, R3, R4 to generate a voltage signal output that matches the voltage and current source signal, wherein the switch Switch 1-2 terminal and Switch The signal input-output level amplification rate of terminal 2-3 is:

Switch 1-2 side V2＝V3

Switch 2-3 side V2＝(1+R3/R4)V3

The isolation circuit 3 is connected to the output terminal of the amplifying circuit 2, which includes a comparator 31 and an optical coupler 32. The comparator 31 receives the same-level signal source V3 output by the amplifying circuit 2, and after analog signal processing, the optical coupler Resistive components R5 and R6 connected to the input and output terminals of the device 32 perform voltage division processing to output the V4 signal source, thereby realizing ground isolation between the input terminal and the output terminal. in:

$\mathrm{<span\; class="notranslate">\; V</span>}\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 6</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; V</span>}\mathrm{<span\; class="notranslate">\; 3</span>}$

The signal isolated and processed by the isolation circuit 3 is input by the positive end of the voltage follower circuit 4, and the signal is converted to output the signal V5, and the signal V5 is output from the output end to the control end, so V5=V4.

Since the above circuit is designed for the independent power supply of the input end, it can reduce the interference to the output end signal, and the signal isolation process can be generated through the voltage division configuration of the optocoupler 32 and the resistor components R5, R6, thereby avoiding the interference of the control end by the ground end (such as CPU, etc.), and when the external input is short-circuited, it can protect the control terminal.

At the same time, combining the same input terminal with the circuit can improve the practicability for voltage and current source signal input, and can also simplify and reduce the circuit wiring and the space occupied by the input port on the circuit board.

Fig. 4 is a schematic diagram of another embodiment of the analog signal conversion and isolation device of the present invention. As shown in the figure, this embodiment is basically the same as the embodiments shown in Fig. 2 and Fig. 3, the difference is that the resistance component R6 of the isolation circuit 3 in Fig. 3 is replaced by the variable resistance component in this embodiment R7 can be adjusted to an optimal resistance value by using the variable resistance component R7, and the voltage division process is performed with the resistance component R5, so that the isolation circuit 3 can effectively isolate the interference of foreign object noise on the control terminal.

The above is only a description of preferred embodiments of the present invention, and is not intended to limit the implementation scope of the present invention. All changes and modifications made without departing from the scope and spirit of the present invention should fall within the scope defined by the claims of the present invention.

Claims (5)

1. An analog signal conversion isolation device, which is connected to a signal input terminal, is used for analog signal conversion and grounding isolation of voltage, current and high current signal sources, wherein the device includes: A filter circuit, the input end of which is connected to the signal input end, and the filter circuit has a shunt resistor (R1), and the shunt resistor (R1) is a precision low-resistance high-power resistance component; An amplifying circuit, the amplifying circuit includes an OP amplifier, a switch component and a plurality of resistance components, the non-inverting input terminal of the OP amplifier is electrically connected to the output terminal of the filter circuit to receive the output signal of the filter circuit, and generate the same level Signal amplified output; the inverting input terminal and output terminal of the OP amplifier are electrically connected to the switch assembly, wherein the switch assembly can be selectively connected to one of a plurality of resistance assemblies to determine the signal input-output level bit magnification; and The isolation circuit is electrically connected to the output terminal of the amplifying circuit to receive the output signal of the amplifying circuit and perform signal conversion, and isolate the interference noise in the signal. 2. The analog signal conversion isolation device according to claim 1, wherein the isolation circuit comprises a comparator and an optocoupler. 3. The analog signal conversion isolation device according to claim 2, wherein the input end of the optocoupler is coupled to a resistance component (R5), and the output end is coupled to another resistance component (R6) to form a voltage division configuration. 4. The analog signal conversion isolation device according to claim 3, wherein the resistance component (R6) coupled to the output end of the optocoupler is a variable resistance component. 5. The analog signal conversion isolation device according to claim 1, wherein the analog signal conversion isolation device further comprises a voltage follower circuit connected to the output terminal of the isolation circuit, and the voltage follower circuit comprises an OP amplifier.

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