CN106094954A - A kind of current output circuit and the electric current way of output thereof - Google Patents
A kind of current output circuit and the electric current way of output thereof Download PDFInfo
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- CN106094954A CN106094954A CN201610452559.7A CN201610452559A CN106094954A CN 106094954 A CN106094954 A CN 106094954A CN 201610452559 A CN201610452559 A CN 201610452559A CN 106094954 A CN106094954 A CN 106094954A
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- output
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- reference voltage
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
- G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
- G05F1/561—Voltage to current converters
Abstract
The invention discloses a kind of current output circuit and the electric current way of output thereof, this circuit includes: reference cell, signal switch unit and current output unit, the reference voltage signal that reference cell produces is input to signal switch unit, and the output signal of controller also enters into signal switch unit；Signal switch unit is used for the output signal of reference voltage signal and controller by being displaced to common-battery source altogether；The output of signal switch unit is input to current output unit；Current output unit, for the output that the output of signal switch unit carries out feedback and signal switch unit by precision resistance being compared, then exports the electric current in final common-battery source.Which includes: by the output signal of reference voltage and controller by being displaced to common-battery source altogether；Signal feedback and the output of common-battery source of electric current is realized by precision resistance.The present invention only needs a precision resistance to can be realized as the output requirement of high-precision signal, and circuit structure is simple, low cost.
Description
Technical field
The present invention relates to a kind of current output circuit and the electric current way of output thereof.
Background technology
Current output circuit is applicable to the scene such as Industry Control, building control, and its main application is to control industry or building
The objects such as the on-the-spot converter of space, valve, it is achieved automatically controlling of the various parameter of industry spot and building environment.
Presently, 4-20mA/0-20mA current signal is applying in work of specifying of a kind of IEC (International Electrotechnical Commission)
Analogue signal standard in industry scene and building control, for input and the output of signal, for the output of control system, electric current
Signal is mainly used in controlling the aperture of valve or the speed controlling of motor it is achieved thereby that automatically controlling of system.Along with frequency conversion
The continuous application of technology, due to heavy-duty motor speed change, start and stop, switch closed pair control system equipment interference the most increasingly
Greatly, the impact also having control system, so general output circuit all uses the mode of isolation to suppress external noise jamming.
In current output circuit current source common-battery source and current source altogether two kinds most commonly seen, as depicted in figs. 1 and 2.
Fig. 1 is current source power current signal output altogether, and electric current returns to ground through overload RL after power supply to constant-current source I1 flows out；Figure
2 is current source earth-current signal output altogether, and for the electric current output on common ground, electric current flows out from power supply and returns constant current through overload RL
Source circuit I2 and I3, finally arrive ground.Arrange owing to the electric current of control valve, converter accepts the general the most particularly isolation of circuit
The when of executing so control system controls multi-way control valve or converter at the same time, if each current output signal does not has
Having an isolation (isolation can increase the biggest cost), the signal ground of each signal output likely links together, cause loading RL2 and
The equal flow phenomenon of the upper signal of RL3, causes control system fault, so current output circuit the most all uses the side in current source common-battery source
Formula exports.When using current source power mode altogether to carry out current signal output, the feedback resistance of electric current is common-battery source,
Connecting together with power supply signal, conventional design is accomplished by being transferred to current feedback signal by resistance ratio the level on common ground
Signal could compare with the voltage output signal of DAC, and this circuit at least needs 3-5 high-precision precision resistance ability
Reaching the requirement of the electric current transmission precision of more than 0.2%, circuit structure is complicated, and cost is high.
The scheme that existing most of analog output circuit uses Fig. 3 to be similar to, in this scheme, MCU produces PWM1, PWM1
Digital pulse signal represents, by the adjustment of dutycycle, the electric current that output is different, and digital signal is by becoming after second-order filter circuit
For analog voltage signal ADC1.ADC1 voltage is converted into signal by current output circuit and exports, due to output current signal just
End and power supply connect together in (i.e. common-battery source), so the voltage on current feedback resistor R10 needs to consist of R4, R5, R6, R7
Ratio circuit adjust after just equal to the voltage signal of ADC1, the value of ultimate current output signal is equal to ADC1/R10.This circuit
Require that resistance R4, R5, R6, R7, R10 are the precision resistance of high stability, otherwise feedback circuit and the resistance ratio of sample circuit
Value differs, and can cause load regulation that electric current exports, voltage regulation factor all can be very poor, does not reaches the required precision of 0.1%.
Summary of the invention
The present invention is directed to above-mentioned problems of the prior art, propose a kind of current source common-battery source current output circuit and
Its electric current way of output, only needs a precision resistance just perfect can realize signal feedback and the output of electric current, it is achieved in high precision
Signal output requirement, circuit structure is simple, low cost, and signal output accuracy is high.
For solving above-mentioned technical problem, the present invention is achieved through the following technical solutions:
The present invention provides a kind of current output circuit, comprising: reference cell, signal switch unit and electric current output are single
Unit, wherein,
Described reference cell is used for producing reference voltage signal；
The described reference voltage signal that described reference cell produces is input to described signal switch unit, described controller
Output signal also enters into described signal switch unit；Described signal switch unit is for by described reference voltage signal and described
The output signal of controller is by being displaced to common-battery source altogether；
The output of described signal switch unit is input to described current output unit；Described current output unit is for by institute
The output that the output stating signal switch unit carries out feedback and described signal switch unit by precision resistance compares, then
Export the electric current in final common-battery source.
It is preferred that described reference cell includes: fiducial chip and peripheral circuit thereof, described fiducial chip is used for producing benchmark
Voltage signal, further,
Described reference cell is output as negative reference voltage signal.
It is preferred that described fiducial chip is controllable accurate source of stable pressure.
It is preferred that signal switch unit includes: interconnective isolated location and filter unit；
Described isolated location is connected with described reference cell, and is connected with the outfan of described controller, and described isolation is single
The noise that unit introduces for suppressing the outfan of described current output unit, is additionally operable to the output signal of described controller by right
The low and high level on ground is converted into the switching between described reference voltage signal and power supply, and then by the output signal of described controller
Dutycycle and the dutycycle of the output of described isolated location the most corresponding；
Described filter unit is connected with described current output unit, defeated for by described isolated location of described filter unit
The dutycycle gone out is converted into corresponding voltage signal.
It is preferred that described isolated location includes: interconnective optocoupler and switch switching chip, described reference cell
Exporting the input with described switch switching chip to be connected, the output signal of described controller is input to described optocoupler；Described switch
The output of switching chip is connected with described filter unit.
It is preferred that described filter unit is second-order filter unit.
The present invention also provides for a kind of electric current way of output, and it comprises the following steps:
S11: by the output signal of reference voltage and controller by being displaced to common-battery source altogether；
S12: realized signal feedback and the output of common-battery source of electric current by precision resistance.
It is preferred that described step S11 is particularly as follows: pass through signal switch unit by reference voltage and the output signal of controller
It is common-battery source by offseting altogether.
It is preferred that described step S11 is further: by the interconnective isolated location of light and filter unit by benchmark
The output signal of voltage and controller is common-battery source by offseting altogether.
Compared to prior art, the invention have the advantages that
(1) present invention provides current output circuit and the electric current way of output thereof, switch single by isolated location and signal
Unit by reference voltage and output signal by being displaced to common-battery source altogether, thus reached only to need a precision resistance just can perfect in fact
The signal feedback of existing electric current and the common-battery source output of current signal, it is achieved the output requirement of high-precision signal, required accurate electricity
Hindering the fewest, its precision is the highest；
(2) present invention only needs a precision resistance to achieve that the output requirement of high-precision signal, due to only one of which essence
Cipher telegram hinders, it is not necessary to carry out the coupling between precision resistance, so the high accuracy of electric current output can be guaranteed, it is easy to reach
To the precision of 0.1%, it is achieved easily, circuit design is simple, low cost, and product reliability is high.
Certainly, the arbitrary product implementing the present invention it is not absolutely required to reach all the above advantage simultaneously.
Accompanying drawing explanation
Below in conjunction with the accompanying drawings embodiments of the present invention are described further:
Fig. 1 is existing current source power current signal output circuit altogether；
Fig. 2 is existing current source earth-current signal output apparatus altogether；
Fig. 3 is the schematic diagram of existing current output circuit altogether；
Fig. 4 is the schematic diagram of the current output circuit of the present invention.
Detailed description of the invention
Elaborating embodiments of the invention below, the present embodiment is carried out under premised on technical solution of the present invention
Implement, give detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following enforcement
Example.
Embodiment 1:
In conjunction with Fig. 4, the current output circuit of the present invention is described in detail by the present embodiment, its schematic diagram as shown in Figure 4,
Comprising: reference cell, signal switch unit and current output unit, in the present embodiment, signal switch unit includes isolation
Unit and filter unit, reference cell, isolated location, filter unit and current output unit are sequentially connected with.Several by this
The circuit of individual unit makes to export electric current AO (being exported by AO+ and AO-terminal)=Duty (PWM_CPU dutycycle) * 2.5V (base
Quasi-voltage)/R9 (load feedback resistance), composition and principle thereof to each unit are described in detail below.
Reference cell is for producing a negative reference voltage signal with VDA power supply as reference, the base that the present embodiment relates to
Quasi-chip uses conventional TL431 fiducial chip, and (benchmark that can also use other higher precision is steady to reach higher output
Qualitative), the reference voltage of 2.5V can be produced, join on the basis of reference voltage output end (VDA) in designing due to the present embodiment
To examine ground, export on the basis of the ground DAREF of benchmark, DAREF-VDA=-2.5V, therefore be output as negative benchmark, reference voltage is-
2.5V, reference signal is connected with DAREF level, is input to switch switching chip U2.
Isolated location possesses two effects, is on the one hand provided the isolation of digital signal by OPT1 optocoupler, will be from control
The pwm signal PWM_CPU of device (MCU) is isolated by optocoupler, thus the on-the-spot noise that suppression introduces from current output terminal, carry
High control system capacity of resisting disturbance；On the one hand for the shaping of digital signal, the low and high level of MCU output signal is converted into base
Switching between quasi-DAREF (-2.5V) and ground (VDA), when MCU output PWM_CPU is 3.3V, and optocoupler output cut-off, optocoupler is defeated
Go out to hold PWM1 to be pulled upward to VDA level (relative VDA is 0V) by resistance R3, the B2 of switch switching chip U2 and output S conducting,
PWMOUT exports-2.5V level；When MCU output PWM_CPU is 0V, and optocoupler output conducting, outfan PWM1 is pulled down and bears base
The B1 of quasi-voltage DAREF (relative VDA is-2.5V), switch switching chip U2 and output S conducting, PWMOUT output 0V is (relatively
VDA) level.The dutycycle of the high level of so MCU output exports the-2.5V of PWMOUT respectively to inductive switch switching chip U2
The dutycycle of level.
In the present embodiment, filter unit is second-order filter unit: R4, R5, C5, C6 form a second order passive filtering electricity
Road, is responsible for being converted into corresponding with dutycycle by filter circuit by the digital signal PWMOUT of switch switching chip U2 output
Voltage signal Vout.When the output PWM_CPU high level dutycycle of MCU is 100%, the outfan of switch switching chip U2 is all the time
Output-2.5V reference signal, filter circuit output Vout=-2.5V (relative VDA)；When dutycycle is 0, filter circuit outfan
Vout=0V (relative VDA), during dutycycle Duty=50%, filtered rear Vout output signal is output as-2.5*Duty=-
2.5*50%=-1.25V (relative VDA)；
The major function of current output unit is that Vout is carried out VI change, this unit mainly include operational amplifier U3,
Metal-oxide-semiconductor Q1, audion Q3, feedback precision resistance R9, backward diode D3 and corresponding auxiliary resistance electric capacity composition.Reverse two poles
Pipe D3 makes electric current can only flow outwardly from inside, and protection internal circuit is not affected by exterior overvoltage and damages.U3、Q1、Q3、
R6, R7, R8, R9 form constant-current source circuit, enter with Vout owing to the output voltage constant-current source electric current of Vout carries out feedback by R9
Row compares so that final AO exports with Vout linearly, AO=Vout/R9, the duty of the PWM_CPU also exported with MCU
Ratio is directly proportional completely: AO=-2.5*Duty ÷ R9=Duty*2.5V/100 ohm=-Duty*25mA, and symbol is negative indication electricity
Stream is flowed to R9 by VDA；When PWM_CPU dutycycle is 100%, and AO is output as 25mA, when dutycycle is 0%, and AO is output as 0mA；
The output of electric current is relevant with feedback resistance stability with the precision of the precision of Duty, benchmark.With other existing current output circuit
Compare, due to only one of which feedback resistance, it is not necessary to carry out the coupling between precision resistance, so the high accuracy of AO output can
It is guaranteed, it is easy to reach the precision of 0.1%.
Embodiment 2:
The electric current way of output of the present invention is described in detail by the present embodiment, and it comprises the following steps:
S11: by the output signal of reference voltage and controller by being displaced to common-battery source altogether；
S12: realized signal feedback and the output of common-battery source of electric current by precision resistance.
Current output circuit the most all uses current signal mode altogether to export, and enters using electric current mode altogether
During the output of row current signal, the feedback resistance of electric current is common-battery source, and power supply signal connects together, and existing design is by electricity
The level signal that stream feedback signal transfers to common ground by resistance ratio could compare with the voltage output signal of DAC, this
Individual circuit at least needs 3-5 high-precision precision resistance to can be only achieved the requirement of electric current transmission precision of more than 0.2%, circuit
Structure is complicated, and cost is high, and electric current transmission precision is low；The present invention is by the output signal of reference voltage and controller by common ground partially
Moving on to common-battery source, the feedback resistance of electric current is common-battery source, and the feedback resistance of such electric current just can directly and the electricity of controller
Pressure output signal compares, and so changes to the voltage offset circuits originally needing multiple precision resistance have only to an electricity
Stream feedback resistance, simplifies design, reduces cost, improves the reliability of product, and easily reaches the electric current biography of 0.1%
Semen deposition degree.
In preferred embodiment, step S11 is particularly as follows: believe the output of reference voltage and controller by signal switch unit
Number it is common-battery source by offseting altogether.Further, step S11 is: will by interconnective isolated location and switch unit
The output signal of reference voltage and controller is common-battery source by offseting altogether.
Disclosed herein is only the preferred embodiments of the present invention, and this specification is chosen and specifically described these embodiments, is
In order to preferably explain the principle of the present invention and actual application, it it is not limitation of the invention.Any those skilled in the art
The modifications and variations done in the range of description, all should fall in the range of the present invention is protected.
Claims (10)
1. a current output circuit, it is characterised in that for the current output circuit of controller, including: reference cell, signal are cut
Change unit and current output unit, wherein,
Described reference cell is used for producing reference voltage signal；
The described reference voltage signal that described reference cell produces is input to described signal switch unit, the output of described controller
Signal also enters into described signal switch unit；Described signal switch unit is for by described reference voltage signal and described control
The output signal of device is by being displaced to common-battery source altogether；
The output of described signal switch unit is input to described current output unit；Described current output unit is for by described letter
The output that the output of number switch unit carries out feedback and described signal switch unit by precision resistance compares, and then exports
The electric current in final common-battery source.
Current output circuit the most according to claim 1, it is characterised in that described reference cell includes: fiducial chip and
Its peripheral circuit, described fiducial chip is used for producing reference voltage signal, further,
Described reference cell is output as negative reference voltage signal.
Current output circuit the most according to claim 2, it is characterised in that described fiducial chip is controllable accurate voltage stabilizing
Source.
Current output circuit the most according to claim 1, it is characterised in that signal switch unit includes: interconnective
Isolated location and filter unit；
Described isolated location is connected with described reference cell, and is connected with the outfan of described controller, and described isolated location is used
In the noise suppressing the outfan of described current output unit to introduce, it is additionally operable to the output signal of described controller by height electricity
Flat turn turns to the switching between described reference voltage signal and ground, and then by the dutycycle of the output signal of described controller and institute
State the dutycycle correspondence respectively of the output of isolated location；
Described filter unit is connected with described current output unit, and described filter unit is for by the output of described isolated location
Dutycycle is converted into corresponding voltage signal.
Current output circuit the most according to claim 4, it is characterised in that described isolated location includes: interconnective
Optocoupler and switch switching chip, the output of described reference cell is connected with the input of described switch switching chip, described control
The output signal of device is input to described optocoupler；The output of described switch switching chip is connected with described filter unit.
Current output circuit the most according to claim 4, it is characterised in that described filter unit is second-order filter unit.
Current output circuit the most according to claim 1, it is characterised in that described current output unit is constant-current source list
Unit, further, including a precision resistance, the output of described signal switch unit by described precision resistance carry out feedback and
The output of described signal switch unit compares, and then exports ultimate current.
8. an electric current way of output, it is characterised in that comprise the following steps:
S11: by the output signal of reference voltage and controller by being displaced to common-battery source altogether；
S12: realized signal feedback and the output of common-battery source of electric current by precision resistance.
The electric current way of output the most according to claim 8, it is characterised in that described step S11 is particularly as follows: cut by signal
Changing unit by the output signal of reference voltage and controller is common-battery source by offseting altogether.
The electric current way of output the most according to claim 8, it is characterised in that described step S11 is further: by light
The output signal of reference voltage and controller is common-battery source by offseting altogether by interconnective isolated location and filter unit.
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| CN201610452559.7A CN106094954B (en) | 2016-06-21 | 2016-06-21 | A kind of current output circuit and its electric current way of output |
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| CN201610452559.7A CN106094954B (en) | 2016-06-21 | 2016-06-21 | A kind of current output circuit and its electric current way of output |
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| CN106094954B CN106094954B (en) | 2018-04-17 |
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| CN102207740A (en) * | 2011-03-30 | 2011-10-05 | 河海大学常州校区 | Isolated multipath 4-20mA-current signal output circuit |
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| CN202083975U (en) * | 2011-05-16 | 2011-12-21 | 上海华建电力设备股份有限公司 | PWM-controlled 4-20mA current output device |
| CN103905033A (en) * | 2014-04-17 | 2014-07-02 | 赵庆松 | 4-20-mA signal output circuit |
| CN204465501U (en) * | 2014-12-31 | 2015-07-08 | 上海自动化仪表有限公司 | A kind of based on PWM analog quantity channel change-over circuit |
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2016
- 2016-06-21 CN CN201610452559.7A patent/CN106094954B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US6639433B1 (en) * | 2002-04-18 | 2003-10-28 | Johnson Controls Technology Company | Self-configuring output circuit and method |
| US20050094341A1 (en) * | 2003-10-29 | 2005-05-05 | Matsushita Electric Industrial Co., Ltd. | Switching power supply apparatus |
| CN102207740A (en) * | 2011-03-30 | 2011-10-05 | 河海大学常州校区 | Isolated multipath 4-20mA-current signal output circuit |
| CN102243503A (en) * | 2011-04-06 | 2011-11-16 | 河海大学常州校区 | Co-grounded multi-path circuit for outputting 4-20mA of current signals |
| CN202083975U (en) * | 2011-05-16 | 2011-12-21 | 上海华建电力设备股份有限公司 | PWM-controlled 4-20mA current output device |
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