CN101867365B - Circuit for converting direct-current positive and negative bipolar signal into unipolar signal through isolation - Google Patents

Abstract

The invention relates to a circuit for converting direct-current positive and negative bipolar signal into unipolar signal through isolation, which comprises a signal input processing circuit, a MOSFET modulation circuit, a signal transformer, a driving transformer, a MOSFET demodulation circuit and a current addition circuit. In the circuit, the isolation of magnetism and electricity is performed by adopting the modulation-demodulation technology, and a polarity reversal current adder adopts a constant current signal outputted by a constant current source as an input reference signal of the inverted input end of an operational amplifier. The circuit improves the reliability of products and the conversion accuracy of the signal, and simultaneously, has a few components, reduces the cost of the products and reduces the volume of the products.

Description

A kind of circuit of converting direct-current positive and negative bipolar signal into unipolar signal through isolation

Technical field

The present invention relates to a kind of signal processing circuit, relate in particular to a kind of circuit of converting direct-current positive and negative bipolar signal into unipolar signal through isolation.

Background technology

At industrial control field, the utilization of direct-current positive/negative signal is very general, for example PLC, transmitter, Electric Machine Control etc.In practical application; In order effectively to suppress common-mode noise between control appliance and the actuating equipment, public Signal Matching and the impedance matching of disturbing and realize control appliance interface and actuating equipment interface, usually signal is carried out effective isolation and convert unipolar signal to be complementary with other devices.

In the prior art direct-current positive/negative signal isolate convert the direct current unipolar signal to implementation method normally linear optical coupling isolate change-over circuit; Its theory diagram is as shown in Figure 1, is made up of 1 add circuit or subtraction circuit, two photoelectrical couplers (1) and (2), two biasing input circuits (1) and (2) and a differential amplifier circuit.Add circuit or subtraction circuit are to be used for converting the positive/negative signal of input into the single-stage signal.Because photoelectrical coupler has its distinctive work linear zone, the biasing input is the input current that is used for regulating photoelectrical coupler (1), makes it be operated in linear zone.And photoelectrical coupler (2) and biasing input (2) come the drift of coupling light electric coupling (1) and non-linear through differential amplifier circuit.Differential amplifier circuit also is used for the analog signal that obtains amplifying.

Add circuit commonly used in this circuit is as shown in Figure 2, and according to the characteristics of amplifier " empty short " and " empty breaking ", 2 voltages of locating of N and P are 0, and the electric current that flows through 2 of N and P is 0, according to the current equation of node N, can draw:

$\frac{V_{\mathrm{<figure-callout\; id="5"\; label="ref\; R"\; filenames="HSA00000104623500021.png"\; state="\{\{state\}\}">ref</figure-callout>}}}{R_{}}+\frac{V_{\mathrm{in}}}{{\mathrm{<figure-callout\; id="4"\; label="R"\; filenames="HSA00000104623500012.png,HSA00000104623500013.png"\; state="\{\{state\}\}">R</figure-callout>}}_4}=-\frac{(-\mathrm{Vo})}{{\mathrm{<figure-callout\; id="6"\; label="R"\; filenames="HSA00000104623500012.png,HSA00000104623500013.png"\; state="\{\{state\}\}">R</figure-callout>}}_6}\&DoubleRightArrow;\mathrm{Vo}=(\frac{{\mathrm{<figure-callout\; id="5"\; label="V\; ref\; R"\; filenames="HSA00000104623500021.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\mathrm{ref}}}{R_{}}+\frac{V_{\mathrm{in}}}{R_4})\&times;{\mathrm{<figure-callout\; id="6"\; label="R"\; filenames="HSA00000104623500012.png,HSA00000104623500013.png"\; state="\{\{state\}\}">R</figure-callout>}}_6$

As Vin=-5V～5V, get R ₄=R ₅=R ₆, getting Vref is 5V, Vo=0～10V then, thus convert bipolar signal into unipolar signal.This circuit needs strict apolegamy resistance, both need consider promptly that all resistances reached unanimity, and makes the outer meeting resistance balance again, just can obtain above-mentioned computing formula.

This circuit subtraction circuit commonly used is as shown in Figure 3, according to the characteristics of amplifier " empty short " and " empty disconnected ", utilizes superposition law, can draw:

$V_o=\frac{\frac{R_5}{{\mathrm{<figure-callout\; id="5"\; label="R"\; filenames="HSA00000104623500021.png"\; state="\{\{state\}\}">R</figure-callout>}}_5+{\mathrm{<figure-callout\; id="6"\; label="R"\; filenames="HSA00000104623500012.png,HSA00000104623500013.png"\; state="\{\{state\}\}">R</figure-callout>}}_6}\&times;V_{\mathrm{in}}+{\mathrm{<figure-callout\; id="4"\; label="V\; ref\; R"\; filenames="HSA00000104623500012.png,HSA00000104623500013.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\mathrm{ref}}}{R_{}}\&times;R_f+\frac{R_5}{{\mathrm{<figure-callout\; id="5"\; label="R"\; filenames="HSA00000104623500021.png"\; state="\{\{state\}\}">R</figure-callout>}}_5+{\mathrm{<figure-callout\; id="6"\; label="R"\; filenames="HSA00000104623500012.png,HSA00000104623500013.png"\; state="\{\{state\}\}">R</figure-callout>}}_6}\&times;V_{\mathrm{in}}$

As Vin=-5V～5V, get R ₄=R ₅=R _f=R ₆, getting Vref is 5V, Vo=0～10V then, thus convert bipolar signal into unipolar signal.This circuit is the same with add circuit, also needs strict apolegamy resistance, both need consider promptly that all resistances reached unanimity, and makes the outer meeting resistance balance again, just can obtain above-mentioned computing formula.

The late-class circuit of this circuit add circuit or subtraction circuit partly is used to realize input signal and the isolation of exporting signal, and circuit common is as shown in Figure 4, and photoelectrical coupler is made up of a light-emitting diode and a light-sensitive device; The luminosity of light-emitting diode is directly proportional with electric current; When electric current increases to when causing that junction temperature raises, light-emitting diode is saturation condition, no longer in the linear work district; The biasing input circuit of photoelectrical coupler can determine to import the scope of its electric current; If but the biasing circuit design is bad, will make that photoelectrical coupler still was operated in linear zone when input current can not in very large range change; The output of two photoelectrical couplers is input to the in-phase end and the end of oppisite phase of amplifier (4) respectively through amplifier (2) and (3), difference is amplified to output again; Amplifier (5) mainly is to be used for zeroing; Wherein, The biasing input circuit of photoelectrical coupler (2) compensates the drift and the non-linear partial of photoelectrical coupler (1) through amplifying circuit; Compensation proves effective, and the output of circuit is just only relevant with the input of photoelectrical coupler (1), therefore requires the characteristic of two photoelectrical couplers to reach unanimity.

Summary of the invention

The object of the invention is to provide a kind of direct-current positive/negative signal to isolate the circuit that converts the direct current unipolar signal to, and this circuit has not only improved reliability of products and conversion of signals precision greatly; Components and parts have still less reduced product cost, have dwindled small product size simultaneously.

The object of the invention can be realized through following scheme: a kind of circuit of converting direct-current positive and negative bipolar signal into unipolar signal through isolation; Comprise the input signal processing unit, be used for converting the direct-current positive/negative voltage input signal to the direct-current positive/negative current signal; The main signal transformer is used for the isolation coupling direct-current positive/negative signal; Driving transformer is used for output and isolates the lock-out pulse drive control signal; MOS FET modulation circuit; The MOSFET demodulator circuit;

Described direct-current positive/negative signal connects the input of input signal processing unit; The output of input signal processing unit connects the centre tap of main signal primary winding, and the reference edge of input signal processing unit connects the common port of MOSFET modulation circuit;

Two outputs of MOSFETT modulation circuit connect the two ends of main signal primary winding respectively;

MOSFETT separates the two ends that two outputs making circuit connect main signal transformer secondary output winding respectively;

Elementary winding of driving transformer and secondary winding respectively have the output of two-way drive signal, connect the drive controlling end of MOSFET modulation and demodulation circuit respectively;

It is characterized in that; Also comprise current adder circuit; The centre tap of said main signal transformer secondary output winding connects the input of current adder circuit, and the output of current adder circuit is a direct current unipolar signal output, and the reference edge of current adder circuit connects the common port of MOSFET demodulator circuit;

Through two groups of lock-out pulse drive signals; Control respectively MOSFET modulation and demodulation circuit by or the synchronous switching of conducting; Copped wave inversion with this direct-current positive/negative current signal of realizing the signal input processing circuit is converted to through voltage-to-current; Direct-current positive/negative current signal after the copped wave inversion is converted into direct current monopolar current signal through current adder with the direct-current positive/negative current signal again through transformer isolation coupling output.

Current adder circuit according to the invention comprises an operational amplifier and a constant-current source; The inverting input of operational amplifier connects the output of constant-current source simultaneously as the input of current adder circuit; The in-phase input end of operational amplifier is as the reference edge of current adder circuit; The output of operational amplifier is the output of current adder circuit.Current adder circuit adopts the input reference signal of the constant current signal of constant-current source output as the operational amplifier reverse input end; Utilize superposition law to convert the positive negative bipolar current signal of the isolation of MOSFET demodulator circuit output into the single-stage current signal, for current signal in the long Distance Transmission than the voltage signal antijamming capability strong and good stability.

Be connected sample resistance between the inverting input of operational amplifier according to the invention and its output, the direct current monopolar current conversion of signals that is used for output is a direct current unipolar voltage signal.

Constant-current source of the present invention is formed by connecting three terminal integrated voltage stabilizer and resistance R 3, and resistance R 3 two ends connect the adjustment end and the voltage output end of three terminal integrated voltage stabilizer respectively, and the adjustment end also connects negative supply; The constant current output concatenation operation amplifier's inverting input of three terminal integrated voltage stabilizer.

Constant-current source of the present invention is formed by connecting the adjustable voltage-stabiliser tube of three ends, NPN triode and two resistance; Resistance R 4 is connected between the anode and reference edge of adjustable voltage-stabiliser tube; The anode of adjustable voltage-stabiliser tube connects negative supply simultaneously; The reference edge of adjustable voltage-stabiliser tube connects the emitter of triode T1 simultaneously; The negative electrode of adjustable voltage-stabiliser tube links to each other with the base stage of triode T1; Negative electrode is the feeder ear of three end programmable precision references, provides control signal to link to each other with the base stage of triode T1 at the same time triode T1; The base stage of triode T1 is through resistance R 3 ground connection, and the collection utmost point of triode T1 is connected to the reverse input end of operational amplifier.

Beneficial effect of the present invention is: the current adder of this circuit adopts the input reference signal of the constant current signal of constant-current source output as the operational amplifier reverse input end; Carry out converting current signal into voltage signal through sample resistance after the current add computing; More traditional add circuit or subtraction circuit structure are more simplified, and product reliability improves greatly when reducing cost; This present invention has simultaneously saved the photoelectrical coupler transmission circuit that causes transmission precision to reduce, and directly adopts two groups of metal-oxide-semiconductor circuit to realize the isolation conversion of signal, and more traditional add circuit or subtraction circuit carry out passing through the circuit implementation that photoelectric coupler isolation is amplified after the reversal; Conversion accuracy improves greatly; And components and parts are also greatly simplified, thereby have further improved reliability of products, have reduced product cost; Reduced small product size; Correspondingly, the production technology of product has also been simplified, and the production difficulty reduces.

Description of drawings

Fig. 1 is the theory diagram of prior art;

Fig. 2 is the physical circuit figure of prior art with add circuit;

Fig. 3 is the physical circuit figure of prior art with subtraction circuit;

Fig. 4 is the physical circuit figure of prior art photoelectric coupler isolation amplifying circuit;

Fig. 5 is an isolation change-over circuit theory diagram of the present invention;

Fig. 6 is the physical circuit figure of the preferred embodiment of the present invention;

Fig. 7 is the physical circuit figure of another embodiment of the present invention;

Fig. 8 is the voltage oscillogram at driving transformer coiling N21, N23 two ends;

Fig. 9 is the voltage oscillogram at driving transformer coiling N22, N24 two ends;

Embodiment

The present invention can be through following preferred practical implementation circuit:

As shown in Figure 5, comprise an input signal processing unit, a MOSFET modulating unit; A MOSFET demodulating unit; An isolation drive unit, signal transformer T1, and current adder circuit; Signal transformer T1 is the main signal isolating transformer of former secondary equal turn numbers; Through two groups of lock-out pulse drive signals, control respectively MOSFET modulation and demodulation circuit by or the synchronous switching of conducting, with the copped wave inversion of this direct-current positive/negative current signal of realizing the signal input processing circuit is converted to through voltage-to-current; Direct-current positive/negative current signal after the copped wave inversion is converted into direct current monopolar current signal through current adder with the direct-current positive/negative current signal again through transformer isolation coupling output.

As shown in Figure 6, above-mentioned modulating unit and demodulating unit all are made up of two metal-oxide-semiconductors, and the drain electrode of two metal-oxide-semiconductors links to each other as the common reference end, and two grids are as the drive controlling end, and two source electrodes are as the output of its connection winding.Above-mentioned input signal processing unit mainly is made up of operational amplifier U1A and resistance R 1, realizes the voltage-to-current conversion of input direct-current positive/negative signal.The in-phase input end of direct-current positive/negative voltage signal Vin input operational amplifier U1A; The inverting input of operational amplifier U1A is leaded up to resistance R 1 and is connected to ground GND1, and another road is connected to the common port of metal-oxide-semiconductor Q1 in the MOSFET modulating unit, Q2 drain electrode; The direct-current positive/negative current signal of operational amplifier U1A output output is connected to the centre tap of the elementary winding of transformer T1.The input terminal voltage of operational amplifier U1A is Vin; Characteristic according to operational amplifier " empty short "; The voltage of operational amplifier reverse input end equals the voltage Vin of input in the same way, and the electric current that then flows through resistance R 1 is Vin/R1, according to the characteristic of operational amplifier " empty disconnected "; Be that the operational amplifier input is the high resistant characteristic; Flow through the electric current of R1 all from the output of the operational amplifier U1A public point through the elementary winding of transformer T1 and metal-oxide-semiconductor Q1, Q2 drain electrode, thus be Vin/R1 through the electric current I 1 of the elementary winding of signal transformer, thus realized the voltage-to-current conversion of direct-current positive/negative signal.

Above-mentioned current adder circuit can be made up of constant-current source and operational amplifier; Present embodiment is made up of operational amplifier U2A, resistance R 2, resistance R 3 and three terminal integrated voltage stabilizer LM317; The resistance two ends connect the adjustment of three terminal integrated voltage stabilizer respectively and hold 1 pin and voltage output end 2 pin; Because the voltage between three terminal integrated voltage stabilizer LM317 voltage output end 2 pin and adjustment end 1 pin remains unchanged, and selects the size of resistance R 3 can reach the purpose of exporting a constant current; The constant current output of three terminal integrated voltage stabilizer connect 3 connect operational amplifier inverting input.Realize conversion and the current-voltage restoring transformation of the positive negative bipolar current signal of signal to the monopolar current signal.After the direct-current positive/negative current signal is isolated through transformer T1, be connected to the inverting input of operational amplifier U2A through the centre tap of transformer T1 secondary winding; Metal-oxide-semiconductor Q3 in the in-phase input end of operational amplifier U2A and the MOSFET demodulating unit, the source electrode common port of Q4 are connected and ground connection; The inverting input of operational amplifier U2A links to each other with three terminal integrated voltage stabilizer LM317 input, and passes through the output of sample resistance R2 concatenation operation amplifier U2A, operational amplifier U2A output direct current unipolar voltage signal.

Above-mentioned isolation drive unit mainly is made up of driving transformer T2; Adopting auto-excitation type is that the Royer circuit is controlled; Its operation principle produces vibration for utilizing the magnetic core saturation characteristic; Mode through self-excitation makes the voltage among driving transformer primary coil N21, N22 and secondary coil N23, the N24 form pulse square wave voltage signal alternately synchronously, is illustrated in figure 8 as the voltage waveform at coil N21, N23 two ends; Fig. 9 is the voltage waveform at coil N23, N24 two ends.The two ends of transformer T2 primary coil N21, N22 connect the metal-oxide-semiconductor Q1 in the MOSFET modulating unit, the grid of Q2 respectively, and centre tap is connected to the source electrode common port of metal-oxide-semiconductor Q1, Q2 in the modulating unit; The two ends of transformer T2 secondary coil N23, N24 connect the metal-oxide-semiconductor Q3 in the MOSFET demodulating unit, the grid of Q4 respectively; Centre tap is connected to the source electrode common port of metal-oxide-semiconductor Q3, Q4 in the modulating unit, thereby for the pulse square wave voltage signal metal-oxide-semiconductor Q3 in metal-oxide-semiconductor Q1, Q2 and the demodulator circuit in the modulation circuit, Q4 is synchronously carried out alternation switch control through the timed delivery that driving transformer primary coil N21, N22 and secondary coil N23, N24 self-excitation produce.

The purpose that adds modulation circuit and demodulator circuit is to realize that signal transformer isolates transmission to the direct current signal of input; Hand at a distance from straight characteristic according to transformer is logical; Therefore, need convert the direct current signal of input into the pulse ac signal earlier, promptly modulate; Through after the transformer isolation conversion, restore and be promptly to carry out demodulation by original direct current signal.

The circuit working principle: the scope of input direct-current positive/negative signal Vin is-Vi～+ Vi, according to the characteristic of operational amplifier, 6 pin of operational amplifier U1A can be exported an electric current I 1 that changes with Vin, I1=Vin/R1; Then the excursion of I1 be-Vi/R1～+ Vi/R1.

When input signal is correct time: suppose that Q1, Q3 are earlier open-minded simultaneously; The current signal I1=Vin/R1 of the 6 pin output of operational amplifier U1A is through the centre tap of the elementary winding of signal transformer T1, through signal transformer T1 primary winding coil N11; Through metal-oxide-semiconductor Q1; Through the centre tap of the elementary winding of driving transformer T2 primary coil, through the coil N22 of the elementary winding of driving transformer T2, GND1 finishes to input ground through resistance R 1; Because the primary and secondary umber of turn of transformer T1 equates, according to transformer characteristic, transformer T1 secondary winding can respond to one with the big or small identical electric current I 2 of I1., Q1, Q3 have no progeny Q2, Q4 conducting simultaneously, the current signal I1=Vin/R1 of the 6 pin output of operational amplifier U1A when closing simultaneously; Centre tap through the elementary winding of signal transformer T1; Through signal transformer T1 primary winding coil N12, through metal-oxide-semiconductor Q2, through the centre tap of the elementary winding of driving transformer T2 primary coil; Through the coil N21 of the elementary winding of driving transformer T2, GND1 finishes to input ground through resistance R 1; Because the primary and secondary umber of turn of transformer T1 equates, according to transformer characteristic, transformer T1 secondary winding can respond to one with the big or small identical electric current I 2 of I1.

When input current when negative: suppose that Q1, Q3 are first open-minded simultaneously; I1 GND1 output from input ground is through resistance R 1, through the centre tap of the elementary winding of driving transformer T2 primary coil; Coil N22 through the elementary winding of driving transformer T2; Through metal-oxide-semiconductor Q1, through signal transformer T1 primary winding coil N11, through the centre tap end of the elementary winding of signal transformer T1; Because the primary and secondary umber of turn of transformer T1 equates, according to transformer characteristic, transformer T1 secondary winding can respond to one with the big or small identical electric current I 2 of I1., Q1, Q3 have no progeny Q2, Q4 conducting simultaneously, the cathodal current signal I1=Vin/R1 of the 6 pin output of operational amplifier U1A when closing simultaneously; I1 GND1 output from input ground is through resistance R 1, through the centre tap of the elementary winding of driving transformer T2 primary coil; Coil N21 through the elementary winding of driving transformer T2; Through metal-oxide-semiconductor Q2, through signal transformer T1 primary winding coil N12, through the centre tap end of the elementary winding of signal transformer T1; Because the primary and secondary umber of turn of transformer T1 equates, according to transformer characteristic, transformer T1 secondary winding can respond to one with the big or small identical electric current I 2 of I1.

So far, the voltage-to-current conversion and the isolation transmission of positive/negative signal have been accomplished.

According to the characteristic of operational amplifier " empty short ", the voltage at operational amplifier 2 pin and 3 pin places is 0; According to the characteristic of operational amplifier " empty disconnected ", can know that the electric current that flows into operational amplifier 2 pin and 3 pin is 0 again, therefore, the output current of operational amplifier 6 pin is:

$\frac{V_{\mathrm{out}}-0}{{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000104623500013.png,HSA00000104623500021.png"\; state="\{\{state\}\}">R</figure-callout>}}_2}=({\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HSA00000104623500013.png,HSA00000104623500021.png"\; state="\{\{state\}\}">I</figure-callout>}}_2+I_{\mathrm{ref}})\&DoubleRightArrow;V_{\mathrm{out}}=({\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HSA00000104623500013.png,HSA00000104623500021.png"\; state="\{\{state\}\}">I</figure-callout>}}_2+I_{\mathrm{ref}})\&times;{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000104623500013.png,HSA00000104623500021.png"\; state="\{\{state\}\}">R</figure-callout>}}_2$

Because of I2=I1=Vin/R1, then have:

$V_{\mathrm{out}}=(\frac{V_{\mathrm{in}}}{{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HSA00000104623500021.png,HSA00000104623500023.png"\; state="\{\{state\}\}">R</figure-callout>}}_1}+I_{\mathrm{ref}})\&times;{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000104623500013.png,HSA00000104623500021.png"\; state="\{\{state\}\}">R</figure-callout>}}_2$

Characteristic according to three terminal integrated voltage stabilizer LM317 can know that the voltage between its 1 pin and 2 pin is constant, and therefore, the electric current I ref of the resistance R of flowing through 3 is a constant current.

For example, need convert Vin=-5V～5V into 0～5V, power taking resistance R1 is that 1000 Ω, Iref are that 5mA, resistance R 2 are that 500 Ω get final product; Convert 0～10V into like need, R2 is taken as 100 Ω; And the like, change the size of R2, can change the size of output area.

If there is not the also exportable current signal of this circuit of sample resistance R2, for current signal in the transmission of long line than the voltage signal antijamming capability strong and good stability.

Be illustrated in figure 7 as another execution mode of the present invention, concrete principle is same as the previously described embodiments with composition, and difference is the constant-current source in the current adder circuit, and this constant-current source is formed by connecting three end programmable precision reference AZ431, NPN triode and two resistance; Resistance R 4 is connected between anode (ANODE) the A pin and reference edge (REF) R pin of AZ431; Because the voltage between the adjustable shunting a reference source of three ends AZ431 anode (A pin) and the reference edge (R pin) remains unchanged, select the size of resistance R 4 can reach the purpose of exporting a constant current; The A pin of AZ431 connects negative supply simultaneously; The R pin of AZ431 connects the emitter of triode T1 simultaneously; AZ431 negative electrode (CATHODE) C pin links to each other with the base stage of triode T1, and negative electrode C pin is the feeder ear of three end programmable precision reference AZ431, control signal is provided at the same time triode T1; The base stage of triode T1 is through resistance R 3 ground connection, and the collection utmost point of triode T1 is connected to the reverse input end of operational amplifier.

In like manner, the output current of operational amplifier 6 pin is:

$\frac{V_{\mathrm{out}}-0}{{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000104623500013.png,HSA00000104623500021.png"\; state="\{\{state\}\}">R</figure-callout>}}_2}=({\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HSA00000104623500013.png,HSA00000104623500021.png"\; state="\{\{state\}\}">I</figure-callout>}}_2+I_{\mathrm{ref}})\&DoubleRightArrow;V_{\mathrm{out}}=({\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HSA00000104623500013.png,HSA00000104623500021.png"\; state="\{\{state\}\}">I</figure-callout>}}_2+I_{\mathrm{ref}})\&times;{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000104623500013.png,HSA00000104623500021.png"\; state="\{\{state\}\}">R</figure-callout>}}_2$

Because of I2=I1=Vin/R1, then have:

$V_{\mathrm{out}}=(\frac{V_{\mathrm{in}}}{{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HSA00000104623500021.png,HSA00000104623500023.png"\; state="\{\{state\}\}">R</figure-callout>}}_1}+I_{\mathrm{ref}})\&times;{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000104623500013.png,HSA00000104623500021.png"\; state="\{\{state\}\}">R</figure-callout>}}_2$

Characteristic according to voltage reference AZ431 can know that the voltage at its resistance R 4 two ends is constant, and therefore, the electric current I ref of the R4 that flows through is a constant current.

For example, need convert Vin=-5V～5V into 0～5V, getting R1 is that 1000 Ω, Iref are that 5mA, R2 are that 500 Ω get final product; Convert 0～10V into like need, R2 is taken as 100 Ω; And the like, change the size of R2, can change the size of output area.

Execution mode of the present invention is not limited thereto; According to foregoing of the present invention; Ordinary skill knowledge and customary means according to this area; Do not breaking away under the above-mentioned basic fundamental thought of the present invention prerequisite, the present invention can also make equivalent modifications, replacement or the change of other various ways, all can realize the object of the invention.

Claims (6)

1. the circuit of a converting direct-current positive and negative bipolar signal into unipolar signal through isolation comprises the input signal processing unit, is used for converting the direct-current positive/negative voltage input signal to the direct-current positive/negative current signal; The main signal transformer is used for the isolation coupling direct-current positive/negative signal; Driving transformer is used for output and isolates the lock-out pulse drive control signal; The MOSFET modulation circuit; The MOSFET demodulator circuit;

Described direct-current positive/negative signal connects the input of input signal processing unit; The output of input signal processing unit connects the centre tap of main signal primary winding, and the reference edge of input signal processing unit connects the common port of MOSFET modulation circuit;

Two outputs of MOSFET modulation circuit connect the two ends of main signal primary winding respectively;

Two outputs of MOSFET demodulator circuit connect the two ends of main signal transformer secondary output winding respectively;

Elementary winding of driving transformer and secondary winding respectively have the output of two-way drive signal, connect the drive controlling end of MOSFET modulation and demodulation circuit respectively;

It is characterized in that; The circuit of said converting direct-current positive and negative bipolar signal into unipolar signal through isolation also comprises current adder circuit; The centre tap of said main signal transformer secondary output winding connects the input of current adder circuit; The output of current adder circuit is a direct current unipolar signal output, and the reference edge of current adder circuit connects the common port of MOSFET demodulator circuit;

Through two groups of lock-out pulse drive signals; Control respectively MOSFET modulation and demodulation circuit by or the synchronous switching of conducting; Realize the copped wave inversion of direct-current positive/negative input signal with this; Signal after the copped wave inversion is converted into the output of direct current monopolar current signal through current adder with the direct-current positive/negative current signal again through main signal transformer isolation coupling output direct-current positive/negative signal.

2. according to the circuit of the said converting direct-current positive and negative bipolar signal into unipolar signal through isolation of claim 1, it is characterized in that: said current adder circuit comprises an operational amplifier and a constant-current source; The inverting input of operational amplifier connects the output of constant-current source simultaneously as the input of current adder circuit; The in-phase input end of operational amplifier is as the reference edge of current adder circuit; The output of operational amplifier is the output of current adder circuit.

3. according to the circuit of the said converting direct-current positive and negative bipolar signal into unipolar signal through isolation of claim 2; It is characterized in that: be connected sample resistance between the inverting input of said operational amplifier and its output, the direct current monopolar current conversion of signals that is used for output is a direct current unipolar voltage signal.

4. according to the circuit of the said converting direct-current positive and negative bipolar signal into unipolar signal through isolation of claim 2; It is characterized in that: described constant-current source is formed by connecting three terminal integrated voltage stabilizer and resistance R 3; Resistance R 3 two ends connect the adjustment end and the voltage output end of three terminal integrated voltage stabilizer respectively, and the adjustment end also connects negative supply; The constant current output concatenation operation amplifier's inverting input of three terminal integrated voltage stabilizer.

5. according to the circuit of the said converting direct-current positive and negative bipolar signal into unipolar signal through isolation of claim 2, it is characterized in that: described constant-current source is formed by connecting the adjustable voltage-stabiliser tube of three ends, NPN triode and two resistance; Resistance R 4 is connected between the anode and reference edge of adjustable voltage-stabiliser tube; The anode of adjustable voltage-stabiliser tube connects negative supply simultaneously; The reference edge of adjustable voltage-stabiliser tube connects the emitter of triode T1 simultaneously; The negative electrode of adjustable voltage-stabiliser tube links to each other with the base stage of triode T1; Negative electrode is the feeder ear of three end programmable precision references, provides control signal to link to each other with the base stage of triode T1 at the same time triode T1; The base stage of triode T1 is through resistance R 3 ground connection, and the collection utmost point of triode T1 is connected to the reverse input end of operational amplifier.

6. the circuit of converting direct-current positive and negative bipolar signal into unipolar signal through isolation according to claim 1 is characterized in that, the primary and secondary of said main signal transformer such as is at number of turn coiling.

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