CN103543411A - Lithium battery voltage detection device - Google Patents

Abstract

The invention relates to a lithium battery voltage detection device. The device comprises a first operational amplifier, a linear optocoupler and a second operational amplifier, wherein a normal phase input end of the first operational amplifier is connected with a lithium battery, an output end of the first operational amplifier is connected with the linear optocoupler through a resistor, a first output end of the linear optocouper is connected with a non-inverting input end of the second operational amplifier, and a second output end of the linear optocouper is connected with an inverted input end of the first operational amplifier. The device solves the pressure sharing problem existing in an existing voltage detection circuit through little resistor matching, the voltage detection circuit is low in complexity and can be miniaturized easily, meanwhile, cost is low because the low-cost operational amplifiers and the low-cost optocoupler barrier device are adopted, and high reliability is achieved.

Description

A kind of lithium battery voltage pick-up unit

Technical field

Invention relates to lithium battery management system, particularly relates to a kind of lithium battery voltage pick-up unit.

Background technology

In lithium-ion battery pack managing system, be all that state by electric battery judges, comprise electric current, temperature, voltage and the internal resistance etc. of electric battery, so the measurement of voltage become the key in management system.

Current monomer battery voltage measuring method has many, mainly can be summarized as the several methods such as divider resistance step-down, floating ground measurement, analog switch gating.Electric resistance partial pressure method is mainly by electric resistance partial pressure, virtual voltage to be decayed to and measures the acceptable voltage range of chip, then carries out analog to digital conversion.This method measurement aspect, cost is low, and the life-span is long, but has cumulative errors, and cannot eliminate.Along with increasing of cell number, monomer battery voltage measuring error can increase along with the increase of common mode voltage.During floating ground commercial measurement battery terminal voltage, whether the current electronegative potential of window comparator meeting automatic decision is suitable.If suitable direct startup analog to digital conversion is measured; If Tai Gao or too low, carries out floating control through digital-to-analogue to electronegative potential by microcontroller and makes electronegative potential under suitable state.This scheme changes because electronegative potential is often subject to on-the-spot interference, can not accurately control electronegative potential, affects the measurement effect of whole system.Adopt the scheme of analog switch by analog switch State selective measurements passage, each passage adopts operational amplifier to form line sampling circuit.After the passage that needs to measure in elected, the output of analog switch is sent into analog to digital converter through voltage follower and is carried out analog to digital conversion.The method, according to the size of series battery total voltage, is selected suitable enlargement factor, needn't resistance pressure-dividing network or change electronegative potential and just can directly measure the voltage of any battery, and measure and facilitate.But the method needs amplifier and the precision-matched resistance of One's name is legion, and cost is high, and the dispersiveness of resistance can cause measurement result dispersiveness higher.

Summary of the invention

For above the deficiencies in the prior art, the present invention proposes a kind of lithium battery voltage pick-up unit, by less resistors match, solve the dividing potential drop problem in current voltage detecting circuit, the complexity of voltage detecting circuit is low, be easy to miniaturization, adopt low-cost operational amplifier and light lotus root isolating device to make low cost, high reliability simultaneously.

Object of the present invention is achieved through the following technical solutions:

A kind of lithium battery voltage pick-up unit, this device comprises the first operational amplifier, linear optical coupling and the second operational amplifier, the normal phase input end of described the first operational amplifier is connected with lithium battery, the output terminal of the first operational amplifier is connected with described linear optical coupling by resistance, the in-phase input end of described linear optical coupling the first output terminal and the second operational amplifier, the second output terminal of described linear optical coupling is connected with the inverting input of described the first operational amplifier.

Between the second output terminal of the output terminal of described the first operational amplifier and described linear optical coupling, be connected with an electric capacity.

Between the in-phase input end of described the first operational amplifier and described lithium battery, by the first resistance, be connected, and be connected with the second resistance between the in-phase input end of described the first operational amplifier and ground.

In described linear optical coupling, be provided with a temperature compensation means.

Described temperature compensation means adopts the resistance of positive temperature coefficient (PTC).

The invention has the advantages that:

1 less resistors match can solve the problem that mostly exists resistors match in current voltage detecting circuit.

The complexity of 2 voltage detecting circuits of inventing is low, is easy to miniaturization.

3 low costs, high reliability, the design cost fluctuation of voltage detecting circuit is larger, and the design adopts low-cost operational amplifier and light lotus root isolating device, to realize testing circuit mode cheaply.

4 voltage detecting circuits can be used for the detection of many Battery packs cascade state, and voltage detecting circuit self can cascade, is suitable for modular development.

Accompanying drawing explanation

Fig. 1: cell voltage test philosophy figure;

Fig. 2: cell voltage test implementation illustration of the present invention.

Embodiment

If Fig. 1 is cell voltage test philosophy figure, test macro is connected and is tested with electric battery.Fig. 2 is cell voltage test implementation illustration of the present invention.In figure, lithium battery voltage pick-up unit comprises the first operational amplifier TLE2022, linear optical coupling TIL300 and the second operational amplifier TLE2022, the normal phase input end of described the first operational amplifier TLE2022 is connected with lithium battery E, the output terminal of the first operational amplifier is connected with described linear optical coupling TIL300 by resistance R 6, the in-phase input end of described linear optical coupling TIL300 the first output terminal and the second operational amplifier TLE2022, the second output terminal of described linear optical coupling is connected with the inverting input of described the first operational amplifier.This pick-up unit adopts integrated transporting discharging and opto-coupler chip, and system has higher precision and security.

Described lithium battery E, for each monomer battery voltage input, enters TLE2022 operational amplifier by R3, and operational amplifier output connects R6, enters linear optical coupling TIL300, and output signal enters detection system by TLE2022 operational amplifier and detects.

Between the output terminal of the first operational amplifier and an output terminal of linear optical coupling, be connected with a capacitor C, this capacitor C can prevent that circuit from producing concussion.The inner D0 of TIL300 is light emitting diode, and its working current electricity If is chosen as 10mA.D1, D2 is photodiode, and they are subject to generation current Ip1 and the Ip2 respectively of exciting of D0, and its size is relevant with If:

I _p1=K ₁·I _f

I _p2=K ₂·I _f

K wherein ₁i _f, K ₂i _fshow I _p1, I _p2with I _fvariation, can be described as optically-coupled function.Due to D1, D2 makes by identical technique and is packaged together with D0, and therefore, their optically-coupled function rule is consistent, therefore can establish:

$K=\frac{I_{p2}}{I_{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="HDA0000410607700000011.png"\; state="\{\{state\}\}">p</figure-callout>}1}}=\frac{K_2\&CenterDot;I_{\mathrm{<figure-callout\; id="1"\; label="f\; K"\; filenames="HDA0000410607700000011.png"\; state="\{\{state\}\}">f</figure-callout>}}}{K_{}}---\left(1\right)$

In fact K can be regarded as to constant, the value of K is the electrical parameter of TIL300, and representative value is 1.Parameter value scope is 0.75～1.25..

U1 forms a negative-feedback amplifier, and the voltage of its in-phase input end and inverting input should be similar to phase

V _i>>I _p1·R ₁

Deng, meet:

（2）

U2 is a voltage follower, and output voltage V 0 equals input terminal voltage:

V _i>>I _p2·R ₂ （3）

So the gain of circuit can be by

$\frac{V_0}{V_i}=\frac{I_{P2}}{I_{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="HDA0000410607700000011.png"\; state="\{\{state\}\}">P</figure-callout>}1}}\&CenterDot;\frac{R_2}{{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HDA0000410607700000011.png"\; state="\{\{state\}\}">R</figure-callout>}}_1}=K\frac{R_2}{R_1}---\left(4\right)$

Due to V _ivoltage be to hold in the same way by inputting U1 after R3, R5 dividing potential drop, so:

$V_i=E\&CenterDot;\frac{R5}{R3+R5}---\left(5\right)$

So $V_0=\mathrm{KE}\frac{R_2}{R_1}\frac{R5}{R3+R5}---\left(6\right)$

Can find out output V ₀with E be linear relationship.The V0 of output can send in single-chip microcomputer and detect and process, the corresponding E value of each ac high voltage, the corresponding output voltage V 0 of each E value.The proportionate relationship of whole circuit output voltage and input current can realize by regulating resistance R1, R2, R3, R5.

The present invention is also applicable to DC high-voltage circuit, when E is high direct voltage, just needs to adjust the value of R2, R1, at output terminal, can obtain being applicable to the voltage that single-chip microcomputer detects.

According to actual measurement, the ratio of precision that this type of optocoupler is exported under-10～+ 50 ℃ of operating ambient temperatures is higher, Performance Ratio is more reliable and more stable, therefore for improving accuracy of detection, add temperature compensation link in system, temperature compensation link adopts the resistance of positive temperature coefficient (PTC), resistance raises with temperature, by obtaining the situation of resistance judgement temperature, and by the measurement to temperature, compensation output effect.

Vt=m(T-20)/T, when-10<t<50, m=0, when t<-10 or-during t>50, between m=0.01～0.05, regulate, final required monomer battery voltage is Vfo=Vo+Vt.

Should be appreciated that the above detailed description of technical scheme of the present invention being carried out by preferred embodiment is illustrative and not restrictive.Those of ordinary skill in the art modifies reading the technical scheme that can record each embodiment on the basis of instructions of the present invention, or part technical characterictic is wherein equal to replacement; And these modifications or replacement do not make the essence of appropriate technical solution depart from the spirit and scope of various embodiments of the present invention technical scheme.

Claims (5)

1. a lithium battery voltage pick-up unit, it is characterized in that, this device comprises the first operational amplifier, linear optical coupling and the second operational amplifier, the normal phase input end of described the first operational amplifier is connected with lithium battery, the output terminal of the first operational amplifier is connected with described linear optical coupling by resistance, the in-phase input end of described linear optical coupling the first output terminal and the second operational amplifier, the second output terminal of described linear optical coupling is connected with the inverting input of described the first operational amplifier.

2. a kind of lithium battery voltage pick-up unit according to claim 1, is characterized in that, between the second output terminal of the output terminal of described the first operational amplifier and described linear optical coupling, is connected with an electric capacity.

3. a kind of lithium battery voltage pick-up unit according to claim 1, it is characterized in that, between the in-phase input end of described the first operational amplifier and described lithium battery, by the first resistance, be connected, and be connected with the second resistance between the in-phase input end of described the first operational amplifier and ground.

4. a kind of lithium battery voltage pick-up unit according to claim 1, is characterized in that, is provided with a temperature compensation means in described linear optical coupling.

5. a kind of lithium battery voltage pick-up unit according to claim 4, is characterized in that, described temperature compensation means adopts the resistance of positive temperature coefficient (PTC).

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