CN104897953A - Accurate lithium battery BMS system charging and discharging current sampling and calculation circuit and control method - Google Patents

Abstract

The invention provides an accurate lithium battery BMS system charging and discharging current sampling and calculation circuit, which comprises a lithium battery pack charging and discharging circuit composed of a lithium battery pack, a sampling resistor, an MOS transistor and a load as a main body, an accurate amplifying and summing circuit, an AD acquisition circuit, and an MCU processing circuit, wherein the accurate amplifying and summing circuit, the AD acquisition circuit, the MCU processing circuit and the sampling resistor are sequentially in serial connection. In the lithium battery BMS system charging and discharging current acquisition circuit, an instrument amplifier circuit is adopted, noise and linear errors are reduced, and the acquisition accuracy and the common-mode rejection ability are greatly improved. The in-phase summing circuit provides certain reference voltage, acquisition voltage after processing is controlled in a certain range, and later acquisition and processing are more facilitated. Discrete components are adopted for forming the instrument amplifier circuit, and on the premise of ensuring high accuracy and high common-mode rejection ability, the cost is greatly reduced.

Description

The accurate sample-taking calculating circuit of lithium battery BMS system charging and discharging currents and control method

Technical field

The present invention relates to lithium battery BMS system regions, particularly relate to the accurate sample-taking calculating circuit of a kind of lithium battery BMS system charging and discharging currents and control method.

Background technology

For implementing the strategy of sustainable development, promote the development of new forms of energy.New Green Battery becomes the problem that people pay close attention to just day by day.In conventional batteries field, there is series of problems in actual use in lead-acid battery and nickel-cadmium battery: as containing pollution source such as poisonous heavy metal and strong acid-base corrosivity, and specific volume is little, be not suitable with rapid charge and heavy-current discharge or the nickel-cadmium battery problem of management when series battery many.On the contrary, lithium battery is environmental protection not only, and specific volume is also better than lead-acid battery and nickel-cadmium battery far away, but also has memory-less effect, long service life and single-unit battery core voltage advantages of higher.

But the time of the short only more than ten years of the developing history due to lithium battery; so when overcharge, overdischarge, excess current may there is safety issue in battery; and need accurate electricity when being applied to new forms of energy car and calculate, therefore need good protection and electricity counting circuit come with the use of.Lithium battery BMS system and battery are closely linked, and carry out moment detection, Control protection switch on and off to the voltage of battery, electric current, temperature, well the safety of the whole lithium battery system of protection; Lithium battery BMS system also carries out heat management, battery balanced management, warning reminding simultaneously, calculates residual capacity, discharge power, report SOC & SOH state etc.; Real-time communication is carried out by the interfaces such as RS485/232, serial ports, CAN and system host computer, device controller, energy management system, display system etc.

Charging and discharging currents detects an important indicator as systems axiol-ogy; accurate sampling and calculate particularly important; not only can improve acquisition precision, circuit anti-interference ability, more calculation of capacity and overcurrent protection provide guarantee, improve the security of system, reliability.

Summary of the invention

For solving the problem, the invention provides the technical scheme of the problem of or integrated chip selling at exorbitant prices not high for current lithium battery BMS system power acquisition precision:

The accurate sample-taking calculating circuit of a kind of lithium battery BMS system charging and discharging currents, main body is the lithium battery group charging and discharging circuit be made up of lithium battery group, sampling resistor, metal-oxide-semiconductor and load, also comprise and accurately to amplify and adding circuit, AD gather, MCU process, accurately amplify and adding circuit, AD collection, MCU process and sampling resistor connected in series successively.

Further, accurately amplification and adding circuit adopt magnifier and homophase adding circuit, reversal value are carried out the forward level that accurate transformation becomes unified.

Further, accurate amplification and adding circuit comprise: sampling resistor two ends pressure reduction input end, first order differential amplifier circuit, second level differential amplifier circuit, homophase adding circuit, amplification summation output terminal, reference voltage input and operational amplifier, and sampling resistor two ends pressure reduction input end, first order differential amplifier circuit, second level differential amplifier circuit, homophase adding circuit, amplification summation output terminal, reference voltage input and operational amplifier connect successively in a serial fashion.

Further, operational amplifier adopts 4 channel operation amplifiers, operational amplifier a, operational amplifier b, operational amplifier c, and operational amplifier d uses a passage of 4 channel operation amplifiers respectively.

Further, sampling resistor selects high-accuracy inspection leakage resistance.

The operation steps of the control method of the accurate sample-taking calculating circuit of lithium battery BMS system charging and discharging currents is:

(1) sampling resistor converts the charging and discharging currents in lithium battery group charging and discharging circuit to micro voltage signal;

(2) accurate amplification and adding circuit are by sampling resistor two ends discharge and recharge reversal accurate transformation, voltage amplification is processed into the voltage range 0-3.3v being applicable to AD and gathering, wherein pressure reduction input end in sampling resistor two ends gathers sampling resistor both end voltage, be used for realizing the first order by first order differential amplifier circuit to amplify, and increase substantially the input impedance of circuit, reduce circuit to the decay of faint input signal, rear employing second level differential amplifier circuit is used for realizing the second level and amplifies, and reduce the requirement of resistance precision coupling, improve common mode inhibition capacity, with the differential amplifier circuit that operational amplifier composition is corresponding, be used for providing reference voltage with homophase adding circuit afterwards, guarantee magnitude of voltage that BMS charge-discharge system gathers when discharge and recharge be on the occasion of, and in 0-3.3v, finally amplify summation output terminal and export the collection magnitude of voltage after accurately amplifying process, reference voltage input is used for input reference voltage,

(3) gathering with AD can by the digital signal of MCU processing and identification by accurately amplifying that the analog voltage OK range value processed is converted to;

(4) digital signal after AD Collect conversion processes by MCU process, thus calculates accurate charging and discharging currents value.

Beneficial effect of the present invention is:

(1) in lithium battery BMS system charging and discharging currents Acquisition Circuit, utilize magnifier, while reducing noise and linear error, greatly improve acquisition precision and common mode inhibition capacity.

(2) homophase adding circuit provides certain reference voltage, by the collection Control of Voltage after process in certain scope, and the collection of more convenient rear class, process.

(3) adopt discrete component composition magnifier, under the prerequisite ensureing high precision, high common mode inhibition capacity, greatly reduce costs.

Accompanying drawing explanation

Fig. 1 is structural representation of the present invention;

Fig. 2 accurately amplifies and homophase adding circuit structural representation.

Embodiment

For making goal of the invention of the present invention, technical scheme and advantage clearly, below in conjunction with accompanying drawing, embodiments of the present invention are described in further detail.

As shown in Figure 1, lithium battery group charging and discharging circuit comprises: lithium battery group 1, sampling resistor 2, metal-oxide-semiconductor 6, load or charger 7.Lithium battery BMS system charging and discharging currents is accurately sampled and counting circuit comprises: sampling resistor 2, accurately to amplify and adding circuit 3, AD gather 4, MCU process 5, and wherein sampling resistor 2 selects high-accuracy inspection leakage resistance.

Wherein, as shown in Figure 2, accurately amplification and adding circuit comprise: sampling resistor two ends pressure reduction input end 8, first order differential amplifier circuit 9, second level differential amplifier circuit 10, homophase adding circuit 11, amplification summation output terminal 12, reference voltage input 13.Operational amplifier 14 adopts 4 channel operation amplifiers, operational amplifier a A1, operational amplifier b A2, and operational amplifier c A3, operational amplifier d A4 uses a passage of 4 channel operation amplifiers respectively.

Lithium battery BMS system charge and discharge process and electric current of the present invention accurately sample and evaluation work process as follows:

Lithium battery group 1 is carried out in the process of discharge and recharge between load 7, metal-oxide-semiconductor 6 is normally opened, electric current is through sampling resistor 2, sampling resistor 2 two ends produce voltage difference, be amplified to certain voltage scope 0-3.3v through accurate amplification and adding circuit 3 process, gather 4 through AD, being converted to by analog voltage signal can by the digital signal of MCU process 5 identification, eventually pass MCU algorithm process, obtain accurate charging and discharging currents value.

Accurately amplify in the present invention and adding circuit 3 design proposal as follows:

As shown in Figure 2, first order differential amplifier circuit 9 and second level differential amplifier circuit 10 form magnifier, are produced at sampling resistor 2 two ends after pressure reduction amplifies several times and output to rear class.When R2=R3, R4=R5, R6=R7, this amplifying circuit can obtain algorithmic formula:

$Vo1=\frac{R1+R2+R3}{R1}\×\frac{R6}{R4}\×\mathrm{\Δ}V$

The output voltage of first order differential amplifier circuit 9 and second level differential amplifier circuit 10 is represented in above-mentioned formula,,, be first order differential amplifier circuit 9 resistance value corresponding with second level differential amplifier circuit 10, see Fig. 2, for sampling resistor 2 two ends produce voltage difference.

Sampling resistor 2 two ends produce voltage difference, output voltage is obtained after first order differential amplifier circuit 9 with second level differential amplifier circuit 10, because lithium battery BMS system charge and discharge process electric current exists both direction, therefore rear class needs to add homophase adding circuit 11 provides reference voltage, output voltage is adjusted to certain voltage range, facilitates the normal work of the AD of rear class collection and MCU.This adding circuit for condition, can obtain algorithmic formula with R8=R9, R10=R11:

$Vo=\frac{R10}{R8}\×Vref+Vo1$

Represent homophase adding circuit 11 output voltage in above-mentioned formula, be resistance value corresponding in homophase adding circuit 11, see Fig. 2, represent the reference voltage that reference voltage input 13 inputs.

In conjunction with above-mentioned two formula, can draw and accurately amplify and algorithmic formula that adding circuit 3 is final:

$Vo=\frac{R10}{R8}\×Vref+\frac{R1+R2+R3}{R1}\×\frac{R6}{R4}\×\mathrm{\Δ}V$

Accurate amplification and adding circuit 3 output voltage gather 4 and MCU process 5 through AD, calculate final charging and discharging currents value.

Patent sampling discrete component composition magnifier of the present invention, add bias voltage adjustment, acquisition precision is in turn ensure that under cost-effective prerequisite, and reduce noise, improve common mode inhibition capacity, significantly solve the problem of current lithium battery BMS system charging and discharging currents acquisition precision, expense.

The operation steps of the control method of the accurate sample-taking calculating circuit of this lithium battery BMS system charging and discharging currents is as follows:

(1) sampling resistor 2 converts the charging and discharging currents in lithium battery group charging and discharging circuit to micro voltage signal;

(2) accurate amplification and adding circuit 3 are by sampling resistor 2 two ends discharge and recharge reversal accurate transformation, voltage amplification is processed into and is applicable to the voltage range 0-3.3v that AD gathers 4, wherein sampling resistor two ends pressure reduction input end 8 gathers sampling resistor 2 both end voltage, amplified for realizing the first order by first order differential amplifier circuit 9, and increase substantially the input impedance of circuit, reduce circuit to the decay of faint input signal, rear employing second level differential amplifier circuit 10 amplifies for realizing the second level, and reduce the requirement of resistance precision coupling, improve common mode inhibition capacity, corresponding differential amplifier circuit is formed with operational amplifier 14, afterwards with homophase adding circuit 11 for providing reference voltage, guarantee magnitude of voltage that BMS charge-discharge system gathers when discharge and recharge be on the occasion of, and in 0-3.3v, finally amplify summation output terminal 12 and export the collection magnitude of voltage after accurately amplifying process, reference voltage input 13 is for input reference voltage,

(3) gathering 4 with AD can by the digital signal of MCU process 5 identification by accurately amplifying that the analog voltage OK range value processed is converted to;

(4) digital signal after AD is gathered 4 conversions by MCU process 5 processes, thus calculates accurate charging and discharging currents value.

Above-described embodiment is preferred embodiment of the present invention; it is not the restriction to technical solution of the present invention; as long as without the technical scheme that creative work can realize on the basis of above-described embodiment, all should be considered as falling within the scope of the rights protection of patent of the present invention.

Claims (6)

1. the accurate sample-taking calculating circuit of lithium battery BMS system charging and discharging currents, the lithium battery group charging and discharging circuit of main body for being made up of lithium battery group (1), sampling resistor (2), metal-oxide-semiconductor (6) and load (7), it is characterized in that: also comprise and accurately to amplify and adding circuit (3), AD gather (4), MCU process (5), described accurate amplification and adding circuit (3), AD collection (4), MCU process (5) and sampling resistor (2) connected in series successively.

2. the accurate sample-taking calculating circuit of a kind of lithium battery BMS system charging and discharging currents according to claim 1, it is characterized in that: described accurate amplification and adding circuit (3) adopt magnifier and homophase adding circuit, reversal value are carried out the forward level that accurate transformation becomes unified.

3. the accurate sample-taking calculating circuit of a kind of lithium battery BMS system charging and discharging currents according to claim 2, it is characterized in that: described accurate amplification and adding circuit (3) comprising: sampling resistor two ends pressure reduction input end (8), first order differential amplifier circuit (9), second level differential amplifier circuit (10), homophase adding circuit (11), amplify summation output terminal (12), reference voltage input (13) and operational amplifier (14), described sampling resistor two ends pressure reduction input end (8), first order differential amplifier circuit (9), second level differential amplifier circuit (10), homophase adding circuit (11), amplify summation output terminal (12), reference voltage input (13) and operational amplifier (14) connect successively in a serial fashion.

4. the accurate sample-taking calculating circuit of a kind of lithium battery BMS system charging and discharging currents according to claim 3, it is characterized in that: described operational amplifier (14) adopts 4 channel operation amplifiers, operational amplifier a (A1), operational amplifier b (A2), operational amplifier c (A3), operational amplifier d (A4) use a passage of 4 channel operation amplifiers respectively.

5. a kind of lithium battery BMS system charging and discharging currents is accurately sampled and counting circuit according to claim 1, it is characterized in that: described sampling resistor (2) selects high-accuracy inspection leakage resistance.

6. realize a control method for the accurate sample-taking calculating circuit of lithium battery BMS system charging and discharging currents according to claim 1, it is characterized in that: the operation steps of described control method is:

Sampling resistor (2) converts the charging and discharging currents in lithium battery group charging and discharging circuit to micro voltage signal;

Accurate amplification and adding circuit (3) are by sampling resistor (2) two ends discharge and recharge reversal accurate transformation, voltage amplification is processed into and is applicable to the voltage range 0-3.3v that AD gathers (4), wherein sampling resistor two ends pressure reduction input end (8) gathers sampling resistor (2) both end voltage, amplified for realizing the first order by first order differential amplifier circuit (9), and increase substantially the input impedance of circuit, reduce circuit to the decay of faint input signal, rear employing second level differential amplifier circuit (10) is amplified for realizing the second level, and reduce the requirement of resistance precision coupling, improve common mode inhibition capacity, with the differential amplifier circuit that operational amplifier (14) composition is corresponding, afterwards with homophase adding circuit (11) for providing reference voltage, guarantee magnitude of voltage that BMS charge-discharge system gathers when discharge and recharge be on the occasion of, and in 0-3.3v, finally amplify summation output terminal (12) and export the collection magnitude of voltage after accurately amplifying process, reference voltage input (13) is for input reference voltage,

Gather (4) with AD and be converted to the digital signal that can be identified by MCU process (5) by accurately amplifying the analog voltage OK range value processed;

Digital signal after AD is gathered (4) conversion by MCU process (5) processes, thus calculates accurate charging and discharging currents value.