CN208226862U - A kind of PWM voltage signal isolation is transformed into the circuit of 4~20mA current signal - Google Patents
A kind of PWM voltage signal isolation is transformed into the circuit of 4~20mA current signal Download PDFInfo
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- CN208226862U CN208226862U CN201820422789.3U CN201820422789U CN208226862U CN 208226862 U CN208226862 U CN 208226862U CN 201820422789 U CN201820422789 U CN 201820422789U CN 208226862 U CN208226862 U CN 208226862U
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- optocoupler
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- stablizer
- isolation
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Abstract
The purpose of the utility model is to provide the circuits that a kind of isolation of PWM voltage signal is transformed into 4~20mA current signal, it realizes low cost and accurately current transducer based on pulsewidth modulation.Under the premise of guaranteeing fan-out capability, the linearity and output accuracy of signal conversion are improved, cost is reduced.In order to achieve the above object, there is provided the circuits that a kind of isolation of PWM voltage signal is transformed into 4~20mA current signal for the technical solution of the utility model, which is characterized in that including the adjustable voltage-stablizer of optocoupler U1, optocoupler U2 and three ends.The utility model realizes inexpensive and accurate current transducer based on pulsewidth modulation.Two-way optocoupler provides the PWM signal isolation of input, by the pwm signal after isolation come the 1.25V reference voltage of the adjustable voltage-stablizer in three end of copped wave, so that the adjustable voltage-stablizer in three ends of control exports electric current.
Description
Technical field
The utility model relates to the electricity that a kind of isolation of PWM duty cycle variable voltage signal is transformed into 4~20mA current signal
Road.
Background technique
When general industrial field control signal is by longer cable transmission, 4 Dao 20mA current loops of isolation can be with
It is effective against the adaptability of interference and impedance.But the isolation of analog signal implement it is relative complex, in addition to needing signal isolation
Outside device, it is also necessary to which the devices such as additional independent current source and DAC, circuit implement higher cost.
Summary of the invention
The circuit for being transformed into 4~20mA current signal is isolated the purpose of the utility model is to provide a kind of PWM voltage signal,
It realizes low cost and accurately current transducer based on pulsewidth modulation.Under the premise of guaranteeing fan-out capability, letter is improved
Number conversion the linearity and output accuracy, reduce cost.
In order to achieve the above object, there is provided a kind of isolation of PWM voltage signal to convert for the technical solution of the utility model
To the circuit of 4~20mA current signal, which is characterized in that including the adjustable voltage-stablizer of optocoupler U1, optocoupler U2 and three ends, optocoupler U1
The anode of light emitting diode be connected to the anode of power supply one, cathode is connected to one end of resistance R1, and the other end of resistance R1 connects
It is connected to one end of resistance R2 and the input terminal of pwm signal；The other end of resistance R2 is being connected to the light emitting diode of optocoupler U2 just
Pole, the cathode of the light emitting diode of optocoupler U2 are connected to the cathode of power supply one；
The input terminal of the adjustable voltage-stablizer in three ends is connected to the anode of power supply two, the output end point of the adjustable voltage-stablizer in three ends
It is not connected to one end of the collector of phototriode Q1 of optocoupler U1, one end of resistance R3, adjustable resistance R4, three ends are adjustable
The adjustment end of voltage-stablizer is connected respectively to one end of the output end of integrated transporting discharging, one end of resistance R6, capacitor C2；
The emitter of the phototriode Q1 of optocoupler U1 is connected to the collector and resistance of the phototriode Q2 of optocoupler U2
One end of R5；The emitter connection of the phototriode Q1 of optocoupler U2 is connected respectively to the other end, the adjustable resistance R4 of resistance R3
The other end, the power positive end of integrated transporting discharging, one end of capacitor C1, the non-inverting input terminal of integrated transporting discharging, Zener diode D1
Cathode；
The anode of Zener diode D1 is connected to one end of the power supply negative terminal of integrated transporting discharging, load, and the other end of load connects
It is connected to the cathode of power supply two, one end of resistance R7 is connected respectively to the other end of capacitor C1, the other end of resistance R6, resistance R5
The other end；The other end of resistance R7 is connected to the inverting input terminal of integrated transporting discharging and the other end of capacitor C2.
The utility model realizes inexpensive and accurate current transducer based on pulsewidth modulation.Two-way optocoupler provides PWM
The signal isolation of input, by the pwm signal after isolation come the 1.25V reference voltage of the adjustable voltage-stablizer in three end of copped wave, thus
Control the adjustable voltage-stablizer output electric current in three ends.The phototriode of optocoupler U1 and U2 are on the top of resistance R3 and adjustable resistance R4
The switching connection resistance R5 between bottom end.When the pulse duty cycle of PWM input changes between 0% and 100%.Integrated transporting discharging
A1 and peripheral components constitute unlimited gain multiterminal and feed back low-pass filter, and the direct current of the PWM after isolation is extracted by the filter
Component and the adjustment pin for being entered into the adjustable voltage-stablizer in three ends, so as to cause the output electric current of the adjustable voltage-stablizer in three ends
Change 4 between 20mA.Gamut 20mA output is adjusted by adjustable resistance R4.It is limited simultaneously using zener diode
Integrated transporting discharging A1 supply voltage, reduces the demand of one group of power supply.
Detailed description of the invention
Fig. 1 is the circuit that a kind of PWM voltage signal isolation provided by the utility model is transformed into 4~20mA current signal
Schematic diagram；
Fig. 2 is calculating schematic diagram provided by the utility model.
Specific embodiment
To be clearer and more comprehensible the utility model, hereby with preferred embodiment, and attached drawing is cooperated to be described in detail below.
In conjunction with Fig. 1, the purpose of the utility model is to provide a kind of isolation of PWM voltage signal to be transformed into 4~20mA electric current letter
Number circuit, it realizes low cost and accurately isolation pick-up of the pwm signal to current signal based on pulsewidth modulation.Guaranteeing
Under the premise of signal isolation, the linearity and output accuracy of signal conversion are improved, and cost is greatly lowered.Specific implementation are as follows:
The anode of the light emitting diode of optocoupler U1 is connected to the anode of 5V power supply, and cathode is connected to one end of resistance R1, electricity
The other end of resistance R1 is connected to one end of resistance R2 and the input terminal of pwm signal；The other end of resistance R2 is connected to optocoupler U2's
The anode of light emitting diode, the cathode of the light emitting diode of optocoupler U2 are connected to the cathode of 5V power supply；
The input terminal IN of the adjustable voltage-stablizer VR1 in three ends is connected to the anode of 12V power supply, the adjustable voltage-stablizer VR1 in three ends
Output end OUT be connected respectively to the collector of phototriode Q1 of optocoupler U1, one end of resistance R3, adjustable resistance R4 one
End, the adjustment end Adj of the adjustable voltage-stablizer VR1 in three ends are connected respectively to the output end of integrated transporting discharging A1, one end of resistance R6, electricity
Hold one end of C2；
The emitter of the phototriode Q1 of optocoupler U1 is connected to the collector and resistance of the phototriode Q2 of optocoupler U2
One end of R5；The emitter connection of the phototriode Q1 of optocoupler U2 is connected respectively to the other end, the adjustable resistance R4 of resistance R3
The other end, the power positive end of integrated transporting discharging A1, one end of capacitor C1, the non-inverting input terminal of integrated transporting discharging A1, Zener diode
The cathode of D1；
The anode of Zener diode D1 is connected to the power supply negative terminal of integrated transporting discharging A1, loads one end of RL, loads the another of RL
One end is connected to the cathode of 12V power supply, one end of resistance R7 be connected respectively to the other end of capacitor C1, resistance R6 the other end,
The other end of resistance R5；The other end of resistance R7 is connected to the inverting input terminal of integrated transporting discharging A1 and the other end of capacitor C2.
R1=2K7 is taken in the present embodiment, and R2=2K7, U1, U2 TLP521, R3=100R, R4=200R is adjustable, R5
=549K, R6=2.2M, R7=1M, C1=100NF, C2=33NF, VR1 LM317, A1 are rail-to-rail single integrated transporting discharging, every
From input signal be amplitude 5V 1~2KHz accounting sky can from 0 be adjusted to 100% pwm signal.
In conjunction with Fig. 2, when PWM duty cycle is 100%；Q2 conducting, since integrated transporting discharging A1 and its peripheral components constitute mark
Quasi- unlimited gain multiterminal feedback low-pass filter network impedance is in 3M Ω or so, and the electric current for flowing through Q1 emitter is very small, then
So that saturation voltage is in 1mV or so event Ua such as formula (1) between Q1 emitter and collector are as follows:
Ua=Uc (1)
According to the output end of the adjustable voltage-stablizer LM317 in three ends and the horizontal device property equal to 1.25V of adjustment end.
Available formula (2):
Ue-Ud=1.25V (2)
According to the empty short characteristic Ub=Uc of integrated transporting discharging, then the electric current id such as formula (3) of R5 is flowed through
Then Ua=Uc=Ub=Ud
Flow through the electric current ia+ib such as formula (5) of R3 Yu R4 parallel resistance
According to single integrated transporting discharging electrical characteristic, ib <=0.1mA.
Adjustment R4 resistance value is 164.5 Ω, available to (5) formula by (1)
Ia=20.098-0.1=19.999mA
Because of ic=ib
Then flow through the electric current iL=ia+ic=ia+ib=20.098mA of load
Output design deviation is 0.49% at full capacity
When PWM duty cycle is 0%；Q1 conducting, due to the unlimited increasing of integrated transporting discharging A1 and its peripheral components composition standard
In 3M Ω or so, the electric current for flowing through Q1 emitter is very small, then Q1 is saturated for beneficial multiterminal feedback low-pass filter network impedance
Voltage is in 1mV or so event Ua such as formula (6) are as follows:
Ua=Ue (6)
According to the output end of the adjustable voltage-stablizer LM317 in three ends and the horizontal device property equal to 1.25V of adjustment end.
Available formula (7):
Ue-Ud=1.25V (7)
Flow through the electric current id such as formula (8) of R5
According to the empty short characteristic of integrated transporting discharging, R3 and R4 parallel resistance both end voltage such as formula (9)
Ue-Uc=Ue-Ub=id*R5 (9)
Flow through the electric current ia+ib such as formula (10) of R3 Yu R4 parallel resistance
According to single integrated transporting discharging electrical characteristic, ib <=0.1mA.
Ia=4.0199-0.1=3.920mA can be obtained by (6) to (10) formula
Because of ic=ib
Then flow through the electric current iL=ia+ic=ia+ib=4.0199mA of load
It is 0.48% that zero load, which exports design deviation,.
Therefore when the PWM of Ui input under fixed frequency fed back in 0~100% variation by unlimited gain multiterminal by duty ratio
For the amplitude-frequency characteristic of low-pass filter circuit it is found that when input frequency is fixed, the transmission function of low-pass filter network is to fix and be
Linear.When the DC component of the isolation PWM waveform by R5 is changed to relative to integrated transporting discharging A1 non-inverting input terminal from 0.25V
0.0V.The unlimited gain multiterminal feedback low-pass filter that integrated transporting discharging A1 and peripheral components are constituted extracts this DC component, and
The adjustment pin of the adjustable voltage-stablizer LM317 in three ends is applied it to, so as to cause the adjustment of the adjustable voltage-stablizer LM317 in three ends
Voltage between pin and integrated transporting discharging A1 non-inverting input terminal is from 1.0 fluctuations to 0.0V.Then make the electricity of R3 Yu R4 resistance both ends
Pressure becomes 1.25V (duty ratio 100%) from 0.25V (duty ratio 0).Therefore, from the output of the adjustable voltage-stablizer LM317 in three ends
4 to 20mA electric currents of end output recycle in output loop.According to the electrical characteristic of integrated transporting discharging, can be adjusted by adjusting R4
Export the precision of electric current.
Claims (1)
1. the circuit that a kind of PWM voltage signal isolation is transformed into 4~20mA current signal, which is characterized in that including optocoupler U1, light
The adjustable voltage-stablizer of coupling U2 and three ends (VR1), the anode of the light emitting diode of optocoupler U1 are connected to the anode of power supply one, and cathode connects
It is connected to one end of resistance R1, the other end of resistance R1 is connected to one end of resistance R2 and the input terminal of pwm signal；Resistance R2's is another
One end is connected to the anode of the light emitting diode of optocoupler U2, and the cathode of the light emitting diode of optocoupler U2 is connected to the negative of power supply one
Pole；
The input terminal (IN) of the adjustable voltage-stablizer in three ends (VR1) is connected to the anode of power supply two, the adjustable voltage-stablizer in three ends (VR1)
Output end (OUT) be connected respectively to the collector of phototriode Q1 of optocoupler U1, one end of resistance R3, adjustable resistance R4
The adjustment end (Adj) of one end, the adjustable voltage-stablizer in three ends (VR1) is connected respectively to the output end of integrated transporting discharging (A1), resistance R6
One end, capacitor C2 one end；
The emitter of the phototriode Q1 of optocoupler U1 is connected to the collector and resistance R5 of the phototriode Q2 of optocoupler U2
One end；The emitter of the phototriode Q1 of optocoupler U2 connects the another of the other end, adjustable resistance R4 for being connected respectively to resistance R3
One end, the power positive end of integrated transporting discharging (A1), one end of capacitor C1, the non-inverting input terminal of integrated transporting discharging (A1), Zener diode
The cathode of D1；
The anode of Zener diode D1 is connected to the power supply negative terminal of integrated transporting discharging (A1), loads the one end of (RL), load (RL)
The other end is connected to the cathode of power supply two, one end of resistance R7 be connected respectively to the other end of capacitor C1, resistance R6 the other end,
The other end of resistance R5；The other end of resistance R7 is connected to the inverting input terminal of integrated transporting discharging (A1) and the other end of capacitor C2.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201820422789.3U CN208226862U (en) | 2018-03-27 | 2018-03-27 | A kind of PWM voltage signal isolation is transformed into the circuit of 4~20mA current signal |
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|---|---|---|---|
| CN201820422789.3U CN208226862U (en) | 2018-03-27 | 2018-03-27 | A kind of PWM voltage signal isolation is transformed into the circuit of 4~20mA current signal |
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| CN208226862U true CN208226862U (en) | 2018-12-11 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110413035A (en) * | 2019-09-02 | 2019-11-05 | 武汉松野智能仪表有限公司 | A kind of intelligent signal isolator circuit |
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2018
- 2018-03-27 CN CN201820422789.3U patent/CN208226862U/en active Active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110413035A (en) * | 2019-09-02 | 2019-11-05 | 武汉松野智能仪表有限公司 | A kind of intelligent signal isolator circuit |
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