CN102495274A - Current acquisition circuit for electric automobile power batteries - Google Patents

Abstract

The invention provides a current acquisition circuit for electric automobile power batteries, which comprises a current sensor, a power supply and an analog to digital converter. The current sensor is used for detecting current of the batteries and outputting voltage signals corresponding to current values of the batteries. The power supply is connected with the current sensor and used for providing working voltage for the current sensor. A signal input end of the analog to digital converter is connected with a voltage signal output end of the current sensor and is used for converting analog signals output by the current sensor into digital signals. The power supply is further connected with the analog to digital converter to serve as a reference power supply of the analog to digital converter and provides reference voltage for the analog to digital converter, the reference voltage is equal to the working voltage provided by the power supply, and output voltage of the current sensor is equal to input voltage of the analog to digital converter. The current acquisition circuit for the electric automobile power batteries is simple and achieves high-accuracy current acquisition.

Description

The current acquisition circuit that is used for electric automobile power battery

Technical field

The present invention relates to a kind of current acquisition circuit, be particularly useful for the current acquisition circuit of electric automobile power battery.

Background technology

At present, along with electric vehicle engineering reaches its maturity, electric automobile has begun to popularize.As the important component part of electric automobile development, the development of electrokinetic cell has decisive role, and therefore, the battery management system of electrokinetic cell (BATTERY MANAGEMENT SYSTEM is called for short BMS) also is the key of electric automobile safe and reliable operation.

Battery management system needs accurately to measure the electrokinetic cell electric current; Present current acquisition circuit generally adopts automobile current sensor senses electrokinetic cell electric current; This current sensor adopts the 5V DC power supply usually, and its output characteristics is subject to the influence of power supply voltage fluctuation.Given this, adopt high-precision regulated power supply that current sensor is supplied power, to reduce the influence of power supply to output more; Adopt analog to digital converter (Analog-to-Digital Converter then; Be called for short ADC) realization analog quantity converting digital amount; Certainly analog to digital converter also needs another high precision source of stable pressure that reference voltage is provided; Need altogether two high-precision regulated power supplies at least, can know by inference thus, there is complicated circuit in present current acquisition circuit, cost is higher and software calibration is loaded down with trivial details, can not offset power supply and fiducial error to the influence of sampling precision, the problem that restriction current acquisition precision improves.

Summary of the invention

The object of the present invention is to provide a kind of current acquisition circuit that is used for electric automobile power battery, have complicated circuit, cost height, complex operation, problem that current detection accuracy is lower to solve prior art.

In order to realize the object of the invention, the invention provides a kind of current acquisition circuit that is used for electric automobile power battery, comprising: current sensor is used to detect the electric current of battery and the output voltage signal corresponding with the current value of battery; Power supply is connected with said current sensor, is used for to said current sensor WV being provided; And analog to digital converter, the signal input part of said analog to digital converter is connected with the voltage signal output end of said current sensor, and the analog signal conversion that is used for said current sensor output is a digital signal.Wherein, Said power supply also is connected with said analog to digital converter; Said power supply provides reference voltage as the reference power supply of said analog to digital converter and to said analog to digital converter, and the output voltage that said reference voltage equals WV that said power supply provides and said current sensor equals the input voltage of said analog to digital converter.

The input-output characteristic of said current sensor is following:

$I_P=(V_{\mathrm{out}}-\frac{V_c}{2})\×\frac{1}{G}\×\frac{A}{V_c}$

Wherein, I _PBe primary current, V _OutBe the voltage of said current sensor output, V _cBe the WV that said power supply provides, G is the sensitivity coefficient of said current sensor, and A is the rated operational voltage of current sensor.

The input-output characteristic of said analog to digital converter is following:

$\mathrm{AD}=B\×\frac{\mathrm{Vin}-V_{\mathrm{ADCLO}}}{V_{\mathrm{ref}}}$

Wherein, AD is the collection numerical value of said analog to digital converter, and B is the full width of cloth numerical value of said analog to digital converter, and Vin is the input voltage of said analog to digital converter, V _ADCLOFor the datum of said analog to digital converter and equal 0, V _RefReference voltage for said analog to digital converter.

Input-output characteristic according to current sensor and analog to digital converter; The present invention directly provides reference voltage with the power supply of current sensor as the reference power supply of analog to digital converter and to said analog to digital converter; When adopting the analog to digital converter sampling; Can eliminate the influence of current sensor supply voltage to the current sample precision fully, not only circuit structure is simple, and has realized the high-precision current collection.

Description of drawings

Fig. 1 is the theory diagram of the embodiment of the invention.

Wherein, description of reference numerals is following:

1 current sensor, 2 analog to digital converters, 3 power supplies

Embodiment

Below in conjunction with accompanying drawing and embodiment the present invention is explained further details.

Fig. 1 schematically shows the theory structure of the embodiment of the invention.

As shown in Figure 1, the current acquisition circuit that is used for electric automobile power battery according to the present invention comprises current sensor 1, analog to digital converter 2, power supply 3.

Current sensor 1 is used to detect the electric current and the output voltage signal corresponding with the current value of battery of battery.

Power supply 3 is connected with current sensor 1, analog to digital converter 2, and being used for provides WV, to analog to digital converter 2 reference voltage is provided to current sensor 1.

The voltage signal input end of analog to digital converter 2 is connected with the voltage signal output end of current sensor 1, and the analog signal conversion that analog to digital converter 2 is used for current sensor 1 output is a digital signal.

During operation, the input-output characteristic of current sensor 1 is following:

$I_P=(V_{\mathrm{out}}-\frac{V_c}{2})\×\frac{1}{G}\×\frac{A}{V_c}$

Formula (1)

Wherein, I _PBe primary current; V _OutOutput voltage for current sensor 1; V _cThe WV that provides for power supply 3; G is the sensitivity coefficient of current sensor 1, and G changes according to the input and output range ability of current sensor 1, the sensitivity coefficient G relative fixed of the current sensor of different range abilities, so it can be regarded as a constant; A is the rated operational voltage of current sensor 1.

During operation, the input/output relation of analog to digital converter 2 is:

$\mathrm{AD}=B\×\frac{\mathrm{Vin}-V_{\mathrm{ADCLO}}}{V_{\mathrm{ref}}}$

Formula (2)

Wherein, AD is the collection numerical value of analog to digital converter 2, and B is the full width of cloth numerical value of analog to digital converter 2, and Vin is the input voltage of analog to digital converter 2, V _ADCLOBe the datum (being 0 because of ground connection usually) of analog to digital converter 2, V _RefBe the reference voltage of analog to digital converter 2, this moment, the reference voltage of analog to digital converter 2 (was V _Ref) WV that equals power supply 3 and provide (is V _c).

The output voltage that equals current sensor 1 because of the input voltage (being Vin) of analog to digital converter 2 (is V _Out), V _ADCLO=0 and V _Ref=V _c, formula this moment (2) is transformed to:

$\mathrm{Vout}=V_c\×\frac{\mathrm{AD}}{B}$

Formula (3)

Bring formula (3) into formula (1), then be transformed to:

$I_P=(V_c\×\frac{\mathrm{AD}}{B}-\frac{V_c}{2})\×\frac{1}{G}\×\frac{A}{V_c}=(\frac{\mathrm{AD}}{B}-\frac{1}{2})\×\frac{1}{G}\×A$

Formula (4)

Can find out from formula (4), because the circuit design that the present invention adopts, make the primary current I of current sensor _PThe voltage V that not provided by power supply 3 _cThe influence of fluctuation.

Below lifting an instance explains.

The voltage V of power supply 3 _cAs the reference power supply of current sensor 1, the rated operational voltage A of current sensor 1 is 5V, and the sampling reference voltage of analog to digital converter 2 also is 5V, and analog to digital converter 2 is 12 bit resolutions, and full width of cloth numerical value B is 4095 (to be 4095=2 ¹²-1), sensitivity coefficient G is 10, then in this example:

$I_P=(\frac{\mathrm{AD}}{4095}-\frac{1}{2})\×\frac{1}{2}$

It is thus clear that, in this example, primary current I _PThe collection voltage V that not provided by power supply 3 _cThe influence of fluctuation.

Can find out from testing circuit according to the present invention; The present invention provides reference voltage through adopting the power supply 3 with current sensor 1 as the reference power supply of analog to digital converter 2 and to analog to digital converter 2; Not only omit independent voltage of voltage regulation and the mu balanced circuit of analog to digital converter of the prior art, the voltage reference circuit (promptly having simplified circuit greatly) of analog to digital converter, and eliminated the error that the variation of the voltage of power supply is floated the deviation of the influence of current sensor sampling precision and voltage reference and temperature fully.

At the current acquisition circuit that is used for electric automobile power battery according to the present invention, the analog to digital converter that analog to digital converter 2 can carry for independent analog to digital converter or microcontroller (Micro-Controller Unit is abbreviated as MCU).

To sum up, the current acquisition in the electric automobile power battery management system accurately and reliably, and implementation structure is simple, cost significantly reduces.

Can know that by technological general knowledge the present invention can realize through other the embodiment that does not break away from its spirit or essential feature.Therefore, above-mentioned disclosed embodiment with regard to each side, all just illustrates, and is not only.All within the scope of the present invention or the change in being equal to scope of the present invention all comprised by the present invention.

Claims (3)

1. current acquisition circuit that is used for electric automobile power battery comprises:

Current sensor is used to detect the electric current of battery and the output voltage signal corresponding with the current value of battery;

Power supply is connected with said current sensor, is used for to said current sensor WV being provided; And

Analog to digital converter, the signal input part of said analog to digital converter is connected with the voltage signal output end of said current sensor, and the analog signal conversion that is used for said current sensor output is a digital signal;

And the input-output characteristic of said current sensor is following:

$I_P=(V_{\mathrm{out}}-\frac{V_c}{2})\×\frac{1}{G}\×\frac{A}{V_c}$

Wherein, I _PBe primary current, V _OutBe the output voltage of said current sensor, V _cBe the WV that said power supply provides, G is the sensitivity coefficient of said current sensor, and A is the rated operational voltage of said current sensor;

The input-output characteristic of said analog to digital converter is following:

$\mathrm{AD}=B\×\frac{\mathrm{Vin}-V_{\mathrm{ADCLO}}}{V_{\mathrm{ref}}}$

Wherein, AD is the collection numerical value of said analog to digital converter, and B is the full width of cloth numerical value of said analog to digital converter, and Vin is the input voltage of said analog to digital converter, V _ADCLOFor the datum of said analog to digital converter and equal 0, V _RefReference voltage for said analog to digital converter;

It is characterized in that,

Said power supply also is connected with said analog to digital converter; Said power supply provides reference voltage as the reference power supply of said analog to digital converter and to said analog to digital converter, and the output voltage that said reference voltage equals WV that said power supply provides and said current sensor equals the input voltage of said analog to digital converter.

2. the current acquisition circuit that is used for electric automobile power battery according to claim 1 is characterized in that said analog to digital converter is independent analog to digital converter.

3. the current acquisition circuit that is used for electric automobile power battery according to claim 1 is characterized in that said analog to digital converter is the analog to digital converter that microcontroller carries.

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