CN203376374U - Voltage sensing module based on photoelectric couplers - Google Patents

Abstract

The utility model discloses a voltage sensing module based on photoelectric couplers, which aims to expand the working frequency of a voltage sensor. The voltage sensing module which adopts the photoelectric couplers as isolation transmission devices and cooperates with an operational amplifier to form a double-closed-loop feedback network achieves active non-linear correction and phase compensation. The voltage sensing module thus has great linearity and relatively small phase distortion in a transmission signal high frequency band. The working frequency can reach 50k Hz. The voltage sensing module can serve as a current type voltage sensor and detect high and low-frequency sinusoidal alternating current voltage value.

Description

Voltage sensor module based on photoelectrical coupler

One. technical field

The content that the utility model relates to belongs to the electric parameter measurement technical field, is, by photoelectrical coupler, DC current or alternating current flow valuve are carried out to isolated measurement, as a kind of current sensor, uses, relevant to the production of electrical control equipment.

Two. background technology

Often to use electric current in the production of electrical control equipment, voltage sensor is done isolated detection.At present, the mode that need to carry out the isolated detection voltage of circuit mainly contains two kinds: the one, adopt the ferromagnetism transformer device structure, and directly utilize the mode of transformation ratio to realize voltage transitions; The 2nd, the current mode voltage transformer (VT), adopting current-limiting resistance is electric current by voltage transitions, the mode output current of recycling Current Mutual Inductance, then convert voltage to by resistance.The perception accuracy of the voltage transformer (VT) of transformer device structure is higher, and the linearity is good, and phase distortion is little, but volume is larger, common voltage transformer (VT) and the volume of fist are similar, and the high voltage environment lower volume is larger, seem very heavy, in some control circuit, inconvenience is used.Current mode voltage transformer (VT) small volume, more satisfactory for the detection of low frequency voltage, but, for the detection of high-frequency voltage, have serious phase distortion problem.The voltage measurement that can only reach the 5kHz left and right as high-end as the ZMPT101B frequency of operation, under 5kHz, phase place has lagged behind 7.2 °; Under 10kHz, phase place lags behind 21.6 °, and its amplitude has also descended 7.5%.So, although the volume of current mode voltage transformer (VT) is small and exquisite, in high frequency or the measurement that has strict phase place to require, such as the high-frequency electric power measurement for tens of KHz etc. can not be used.

Need to carry out the voltage, current coupling mode of circuit isolation except transformer, can also adopt photoelectrical coupler, Hall element etc., wherein Hall element is used in the detection of large electric current, and photoelectrical coupler is applied wider in the transfer overvoltage signal.Photoelectrical coupler has many advantages such as little, low in energy consumption, the electric isolation performance of volume is good, anti-electromagnetic interference capability is strong, for between circuit-under-test and metering circuit, needing isolation environment, especially the measurement of high voltage network, the advantage of photoelectrical coupler can find full expression.But photoelectrical coupler is nonlinear device, some is called as the obvious non-line characteristic of also having of precision photoelectric coupler, adopt photoelectrical coupler direct-detection voltage to exist phase place to lag behind and waveform distortion, no matter be can reflect the two situation of change from the Full wave shape coupled circuit or from the rectifier type coupled circuit, as shown in Figure 5.Therefore, for phase place and harmonic distortion, require can not directly with photoelectrical coupler, measure in stricter measurement environment.

Present invention is directed at the bad situation of common voltage sensor high frequency characteristics, the photoelectrical coupler of take goes out the voltage sensor that frequency is higher as foundational development, the linearity test and the sensing that can be used for the internal circuit HF voltage such as inverter, heating generator, form the higher feedback system of accuracy.Therefore, method involved in the present invention has certain application prospect.

Three. summary of the invention

The present invention is based on the voltage sensor module of photoelectrical coupler, the frequency of operation of voltage sensor can be expanded to the higher frequency scope, from technological layer, there is following content characteristic:

Adopt the operational amplifier that is applicable to high-frequency operation, the photoelectric coupling integrator of Cheng Shuan etc., form degree of depth Current Negative Three-Point Capacitance by a pair of photoelectrical coupler wherein, form degree of depth voltage negative feedback by resistance capacitor device, the whole deep negative feedback voltage-current conversion circuit with double circle structure that forms, method is eliminated the nonlinear distortion that photoelectrical coupler brings thus, by another, identical photoelectrical coupler of current transmission characteristic is exported with the current forms isolation; Set scale differentiating circuit in operational amplifier output current branch road, capacitance-resistance proportion differential circuit in parallel again between the output terminal of operational amplifier and end of oppisite phase, method reach photoelectrical coupler drive current thus, make up the signal transmission phase lag problem of high band, as shown in Figure 1.

Realize the linear voltage transmission circuit structure of phase correction as shown in Figure 1, below be called " the voltage sensor module based on photoelectrical coupler ", be called for short the voltage sensor module.

The effect of circuit is the input voltage size variation to be converted linearly to the variation of output current, and when the characteristics of this circuit are the input potential rise, it is large that output current becomes, and shows as same facies relationship, facilitates the processing of output signal.Tested voltage by current-limiting resistance to voltage sensor module input current, in resistance R ₇sampled voltage of upper acquisition, input is by operational amplifier IC ₁what form closes voltage-current converting circuit.IC in the voltage sensor module ₁operational amplifier, IC ₂photoelectrical coupler, DZ ₁be the Parallel Voltage Regulator Circuit device, stablize the operating voltage of whole modular circuit.In modular circuit, amplifier pours into electric current to photoelectrical coupler, and the photoelectric device output current be coupled is in order to promote amplifier end of oppisite phase current potential.By the equipotential work characteristics of two input ends of operational amplifier, determined, input voltage must with the proportional relation of feedback current.The output current signal feedback of translation circuit adopts two photoelectrical coupler IC that characteristic is consistent with output ₂, make output current equal feedback current, be exactly and the proportional relation of tested voltage, as shown in curve in accompanying drawing 2.In order to meet this requirement as far as possible, preferably adopt integrated two photoelectrical couplers, the TLP521-2 adopted in accompanying drawing 1 is exactly a the most frequently used two optocouplers.

In circuit diagram, operational amplifier has adopted NE5532, mainly considers that its frequency of operation is high, and its weak point is that self working current is larger.If adopt LM358 can reduce working current, and the dynamic range of input end is large, the characteristic that the potential minimum of output is lower, can increase measurement range as far as possible.But the time delay of LM358 is longer, add the delay of photoelectrical coupler, cause the amplifier feedback system very long time delay, make circuit produce self-sustained oscillation, can't normal transmission voltage.Certainly, as long as meet the needs of circuit working speed and dynamic range, also can adopt the operational amplifier of other models, as high speed amplifier AD524, AD827, LM833, LF353, CA3240 etc.But do not use low speed devices, as low-power consumption amplifier LM358, micro-power consumption amplifier LMV358 etc.

The output resistance R of operational amplifier ₂for the restriction to photocurrent, resistance R ₂resistance is less, and the output current of optocoupler is larger.If reduce the fluctuation amplitude of operational amplifier output voltage, make operational amplifier can be operated under the low-voltage condition, R ₂value should be smaller, so also can be so that circuit gain be higher.If but R ₂resistance is too small, can make the input current fluctuating range of optocoupler can become greatly, is unfavorable for the stable of sensing circuit, can produce self-sustained oscillation.So, R ₂should coordinate R ₁₂facilities, effectively limit the size of current of photoelectrical coupler, be unlikely to cause the feedback of photoelectrical coupler excessively strong.R ₂value principle be that optocoupler feedback causes the current potential of amplifier end of oppisite phase to approximate amplifier output terminal current potential under static state, coordinate R ₁resistance make it that suitable photocurrent be arranged, as the 1mA current value.With photoelectrical coupler drive current I under static state _dgetting 1mA is example, R ₂and R ₁value is determined by following formula.

$I_{\mathrm{<figure-callout\; id="2"\; label="D\; R"\; filenames="HSA00000865124100022.png"\; state="\{\{state\}\}">D</figure-callout>}}{R}_{}{}_2+2.0\&ap;{\mathrm{<figure-callout\; id="1"\; label="kI\; D\; R"\; filenames="HSA00000865124100021.png,HSA00000865124100022.png"\; state="\{\{state\}\}">kI</figure-callout>}}_D{R}_{}{}_1\&ap;\frac{1}{2}{V}_{\mathrm{CC}}$

Wherein 2.0 is total forward voltage of light emitting diode in two optocouplers, and unit is volt; K is the current transfer ratio of optocoupler, V _cCthe/2nd, the Static Electro place value of operational amplifier input end, photoelectrical coupler drive current I _dartificially given.

Although circuit has adopted the operational amplifier NE5532 that frequency of operation is higher, if current-limiting resistance R ₂value is little, also must connect feedback resistance R ₁₂, to eliminate the circuit self-sustained oscillation caused by the optocoupler feedback separately.Add negative feedback resistor R ₁₂after, making the operational amplifier output potential fluctuate can be too inviolent, and actual is to have limited computing amplifier output voltage when the effect not yet in effect of optocoupler feedback, has prevented that the voltage of photoelectrical coupler feedback is excessive.Feedback resistance R ₁₂the value standard be: separately by R ₁₂the output voltage dynamic amplitude determined is in the dynamic range of amplifying circuit, but the output voltage under will normally acting on separately higher than optocoupler.Also can think R ₁₂formed instant voltage negative feedback, photoelectrical coupler has formed the delayed current negative feedback.Postponing degeneration factor is unsettled system, and two feedback systems make working stability.R ₁₂occurrence will be adjusted by experiment, take to eliminate self-sustained oscillation and determine R as target ₁₂.

The current transfer ratio of voltage sensor module is by the following formula approximate treatment:

$\frac{i_o}{i_i}\&ap;\frac{1}{2}\frac{k(R_1+R_{12})}{({\mathrm{kR}}_{12}+R_2+{2r}_D)}$

Wherein k is the current transfer ratio of photoelectrical coupler, r _dit is the AC resistance of light emitting diode in photoelectrical coupler.R ₁, R ₂and R ₁₂resistance is less, and current transfer ratio is larger.R ₂the impact that resistance passes ratio to electric current is closer.

Be directed to nonlinear distortion and the phase lag problem of photoelectrical coupler, designed the closed-loop amplifying circuit containing the phase correction circuit, utilize the deep negative feedback to carry out nonlinear compensation, realize linear transfer.Capacitor C ₄and C ₅for phase compensation and gain compensation, make up photoelectrical coupler and postpone the output current phase deviation caused, as shown in Figure 4, make the phase place of optocoupler output current and input voltage be consistent, make up the defect that causes high band gain reduction because of the operating rate restriction simultaneously.Accompanying drawing 3 is to have made up input voltage after circuit output current phase delay problem and the squiggle of output current.Feedback capacity C ₄there is the effect of Mid Frequency output current phase place, the gain of raising Mid Frequency, hysteresis high band output current phase place, reduction high-frequency gain in advance, C ₄the larger phase-shift phase of capacity larger; Simultaneously, feedback capacity C ₄also there is the self-oscillatory effect of the circuit of elimination.Differential capacitance C ₅there is output current phase place and the effect that increases the high band gain in advance, but will note C ₅capacity is crossed conference and is caused circuit self-sustained oscillation.C ₄and C ₅occurrence to adjust by experiment, at rear definite R ₁₂resistance, then take and correct phase place and amplitude and comprehensively determine C as target ₄and C ₅value.Phase compensation amount is mainly by R ₂, R ₃, C ₅the network parameter formed determines, can analyze from this network impedance.

$Z=\frac{R_2(R_3-\mathrm{<figure-callout\; id="1"\; label="j"\; filenames="HSA00000865124100021.png,HSA00000865124100022.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{1}{\mathrm{\&omega;}{C}_5})}{{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000865124100022.png"\; state="\{\{state\}\}">R</figure-callout>}}_2+R_3-\mathrm{<figure-callout\; id="1"\; label="j"\; filenames="HSA00000865124100021.png,HSA00000865124100022.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{1}{\mathrm{\&omega;}{C}_5}}=R_2\frac{(R_3\mathrm{\&omega;}{C}_5-j)}{({\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000865124100022.png"\; state="\{\{state\}\}">R</figure-callout>}}_2+R_3)\mathrm{\&omega;}{C}_5-j}={\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000865124100022.png"\; state="\{\{state\}\}">R</figure-callout>}}_2\frac{1+R_3({\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000865124100022.png"\; state="\{\{state\}\}">R</figure-callout>}}_2+R_3){\mathrm{\&omega;}}^2{C}_5^2-\mathrm{<figure-callout\; id="2"\; label="j\; R"\; filenames="HSA00000865124100022.png"\; state="\{\{state\}\}">j</figure-callout>}{R}_{}{}_2\mathrm{\&omega;}{C}_5}{1+{({\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000865124100022.png"\; state="\{\{state\}\}">R</figure-callout>}}_2+R_3)}^2{\mathrm{\&omega;}}^2{C}_5^2}$

Angle of phase displacement is: $\mathrm{\&theta;}=-\mathrm{<figure-callout\; id="2"\; label="arctg\; R"\; filenames="HSA00000865124100022.png"\; state="\{\{state\}\}">arctg</figure-callout>}\frac{R_{}}{}\frac{{}_2{\mathrm{\&omega;C}}_5}{1+R_3(R_2+R_3){\mathrm{\&omega;}}^2{C}_5^2}$

Impedance magnitude is: $Z=\frac{R_2}{1+{(R_2+R_3)}^2{\mathrm{\&omega;}}^2{C}_5^2}\sqrt{{[1+R_3(R_2+R_3){\mathrm{\&omega;}}^2{C}_5^2]}^2+{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000865124100022.png"\; state="\{\{state\}\}">R</figure-callout>}}_2^2{\mathrm{\&omega;}}^2{C}_5^2}$

The phase compensation ability is with R ₃increase and reduce.Impedance Z affects the current delivery gain, and Z is larger, and current gain is less.

In accompanying drawing 1, the supply voltage of closed-loop amplifying circuit is defined as the 5V left and right, in practical application, also can be decided to be other numerical value.The input mode of supply voltage can be other direct supplys, as 12V direct supply etc., and also can be by obtaining after the resistance current limliting from tested high voltage.If obtain power supply from tested high voltage, its current limliting branch road provides the ability of electric current should be greater than the working current of closed-loop amplifying circuit, and too much electric current is by voltage stabilizing diode D ₂shunting, guarantee the stable of circuit voltage.R in figure ₁, C ₁, C ₂, C ₃form π type RC filter network, namely for level and smooth supply voltage, during particularly by tested high voltage current limliting power supply, must adopt this network.This voltage sensor module is when the 5V power voltage supply, and working current is about 9mA.

In the work of voltage sensor modular circuit, guarantee on the photoelectrical coupler interior light emitting diodes to exist all the time electric current.

Voltage sensor modular circuit current transfer ratio and phase relation:

The invention has the beneficial effects as follows, the sinusoidal voltage frequency, when 50kHz is following, not only has good voltage-to-current linear transformation relation, also has less phase pushing figure.Can be for the ac voltage measurement of the current unapproachable high-frequency environment of voltage sensor product.

Four. the accompanying drawing explanation

Fig. 1 is the voltage sensor module circuit diagram of realizing the electric current and voltage linear transformation.I wherein _itested voltage input end, V _cCthe required input voltage of modular circuit work, V ₊-V _-voltage sensor blocks current delivery outlet, IC ₁the operational amplifier of realizing voltage-current transformation, IC ₂photoelectrical coupler, DZ ₁it is the Parallel Voltage Regulator Circuit device.

Fig. 2 is the squiggle of voltage sensor module input voltage and output current.Reflect the linear relationship that they are good.

Fig. 3 is the squiggle of voltage sensor module input voltage and output current under the 50kHz frequency.Reflect and only have small phase deviation between the two.

Fig. 4 is input voltage when under the 50kHz frequency, circuit is not done phase correction and the squiggle of output current.Reflect larger phase deviation is arranged between the two.

Fig. 5 is the directly input voltage when the voltage transmission and the squiggle of output current of photoelectrical coupler.The nonlinear relationship that reflects both.

Five. embodiment

" the voltage sensor module based on photoelectrical coupler " in the present invention can be made into to the standalone module structure, reserve three input ports, two output ports, be convenient to actual use.Also the voltage sensor modular circuit in the present invention and other control circuits can be combined, layout on the same pcb board.Wherein the selection of operational amplifier and photoelectrical coupler model with operating rate soon for well.

Tested voltage is connected with the voltage sensor module: tested voltage need to be by being connected to the I of voltage sensor module after the resistance current limliting _ibetween end and ground wire, the cut-off current peak value is no more than 1.5mA.

Voltage sensor module operating voltage: apply the 10-15V DC voltage between Vcc end and ground wire, the Vcc end is for anodal.Perhaps by the current limliting network, from tested voltage, obtain the working current more than 10mA.

This voltage sensor module is current mode output, but output terminal can not initiatively provide electric current, need to add in addition DC voltage and could form output current.The size of impressed DC voltage gets final product between 1.0-12V to guarantee voltage sensor module output port voltage, and polarity of voltage is as accompanying drawing 1.Comprise quiescent current in output current, the information of measured parameter, with dynamically (variation) form appearance, need to be exported after DC-isolation, as adopted capacitive coupling output.Its dynamic peak value is less than 1.5mA.

This voltage sensor module application detects in the voltage signal of sine wave or near sinusoidal, can not detect for pulse voltage.

Claims (1)

1. the voltage sensor module based on photoelectrical coupler, it is characterized in that: adopt operational amplifier, the photoelectric coupling integrator of Cheng Shuan, form degree of depth Current Negative Three-Point Capacitance by a pair of photoelectrical coupler wherein, form degree of depth voltage negative feedback by resistance capacitor device, the whole deep negative feedback voltage-current conversion circuit with double circle structure that forms, exported with the current forms isolation the identical photoelectrical coupler of current transmission characteristic by another; Set scale differentiating circuit in operational amplifier output current branch road, capacitance-resistance proportion differential circuit in parallel again between the output terminal of operational amplifier and end of oppisite phase.

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