Background technology
Chargeable lithium ion battery (is called for short down: lithium battery) in the charge and discharge course of work, need press and key parameters such as charging restriction electric current, discharge restriction electric current monitor and control its overcharged voltage, overdischarge, with prevent battery damage in advance and guarantee to use in safety.
At present; the protective circuit of single lithium battery is very ripe; be illustrated in figure 5 as the theory diagram of common single lithium battery protective circuit; this protective circuit comprises the voltage detecting circuit of being made up of comparator a and comparator b 51; charging control switch 54, discharge control switch 55, current detection circuit 52 and logic determines control circuit 53.The take a sample both positive and negative polarity current potential of detected battery of comparator a, b, the reference voltage that the potential difference of both positive and negative polarity and comparator a, b is built-in is relatively exported to comparative result logic determines control circuit 53 then; Simultaneously, current detection circuit 52 sampling charging current or discharging currents, after comparing the result exported to logic determines control circuit 53, logic determines control circuit 53 is according to the break-make of prior preset program control charging control switch 54 and discharge control switch 55, thereby realize voltage, charging current, the discharging current of battery are monitored and controlled, reach prevent battery damage in advance and guarantee to use in purpose of safety.
Wherein, cell voltage VB equals the poor of anode current potential UB+ and negative pole current potential UB-, as shown in the formula:
VB=(UB+)-(UB-)………………………………………①
In the protective circuit of cell, voltage detecting circuit, current detection circuit, logic determines control circuit all have a reference potential, and foregoing circuit is that negative pole current potential UB-with battery is as reference potential.
After multiple batteries was connected into battery pack, its voltage detecting circuit, current detection circuit, logic determines control circuit still needed a reference potential, usually with the anodal current potential USB+ of series battery or negative pole current potential USB-as reference potential.As shown in Figure 6, suppose we with the negative pole current potential USB-of series battery as reference potential, according to formula 1., the voltage VBn of any batteries Bn and the relation of reference potential USB-are as follows:
VBn=(UBn+)-(UBn-)
=(UBn+)-(UBn-)+(USB-)-(USB-)
=[(UBn+)-(USB-)]-[(UBn-)-(USB-)]…………②
That is: the voltage VBn of any batteries poor [(UBn+)-(USB-)] that equal the anodal current potential of this battery and reference potential deducts poor [(UBn-)-(USB-)] of the negative pole current potential and the reference potential of this battery.
The voltage detection method of some series battery protective circuits commonly used utilizes formula principle 2. to make at present.Below we are example with one 3 joint series battery protective circuit; its operation principle is described: as shown in Figure 7, this protective circuit comprises voltage detecting circuit 71, charging control switch 74, discharge control switch 75, current detection circuit 72 and logic determines control circuit 73.This protective circuit with the negative pole current potential UB3-of series battery as reference potential; the internal reference of described each voltage comparator all links to each other with the negative pole end of series battery; the take a sample anodal current potential UB+ of corresponding cell of an input of comparator; obtain the anodal current potential UB+ of battery and the difference data [(UB+)-(UB3-)] of reference potential UB3-; the negative pole current potential UB-of another input sampling battery of described comparator; obtain the negative pole current potential UB-of battery and the difference data [(UB-)-(UB3-)] of reference potential UB3-; described data [(UB+)-(UB3-)] and [(UB-)-(UB3-)] compare in comparator inside; and with control threshold ratio after; the level signal of each monomer battery voltage situation of the corresponding reflection of output; with reference potential UB3-is that the logic judging circuit 73 of reference point can be accepted these level signals easily; and after logic determines the break-make of control charging control switch 74 and discharge control switch 75, thereby reach the effect that every batteries in the series battery is all protected.
As shown in Figure 7 in the protective circuit; the level signal of voltage detecting circuit 71 outputs all adopts same reference potential UB3-; made things convenient for the use that is connected with the logic determines control circuit; but; since the voltage detecting circuit of every batteries all with reference potential UB3-as the reference current potential, along with increasing of series-connected cell, the potential difference of cell current potential and reference potential UB3-is increasing; just produced some shortcomings, mainly contained:
1, along with the increasing of series-connected cell quantity, potential difference is increasing between cell current potential and the reference potential, and is more and more higher to the requirement of withstand voltage of circuit;
2, along with potential difference between cell current potential and the reference potential increases, the voltage range that comparator detects is more and more wider, thereby guarantees that accuracy of detection also becomes more and more difficult;
3, circuit also becomes increasingly complex simultaneously.
Owing to above shortcoming, be subjected to the process technology limit of integrated circuit, present commercial series battery protection integrated circuit only can accomplish to manage 4 joint series-connected cell levels.
Embodiment
The present invention has done important breakthrough to the mentality of designing of available circuit, has designed multisection lithium battery series battery protective circuit with a kind of method of complete novelty.
In the present invention, each joint cell connects a voltage monitoring module, and the working power of described voltage monitoring module is provided by monitored cell, and all voltage monitoring modules are relatively independent voltage monitoring unit.During the structure series battery, want according to the cell number needs of series battery, some voltage monitoring modules of connecting form the electric voltage observation circuit of series battery.During battery pack work, each voltage monitoring module is to the both positive and negative polarity current potential sampling of corresponding cell, relatively, output is charging voltage detection signal A and discharge voltage detection signal B with reference to current potential with the electrode potential of tested cell, because the output signal A of each voltage monitoring module and B all with the electrode potential of tested cell as the reference current potential, thereby the current potential of these charge and discharge voltage detection signal A and B disperses.The signal that is converted to unified reference potential for charge and discharge voltage detection signal A that described current potential is disperseed and B, the present invention has introduced change-over circuit, by change-over circuit with all charge and discharge voltage detection signal A and B combination, to be converted to electrode potential with battery pack be charge and discharge voltage detection signal A ', B ' with reference to current potential.
Further specify below in conjunction with accompanying drawing.
As shown in Figure 1; this multisection lithium battery series battery protective circuit comprises single-chip microcomputer 14; be connected in the electric voltage observation circuit and the current monitoring module 17 of single-chip microcomputer 14 inputs; and control by single-chip microcomputer 14; charging control switch 15 of connecting and discharge control switch 16 with battery pack; described electric voltage observation circuit contains some voltage monitoring modules 12 and a change-over circuit 13; it is filling with reference to current potential that described change-over circuit 13 is used for the electrode potential that the output signal with some voltage monitoring modules 12 is converted to battery pack; the discharge voltage detection signal; the input of each voltage monitoring module 12 is connected with the positive and negative electrode of corresponding cell; two outputs of all voltage monitoring modules 12 connect two inputs of conversion circuit 13 respectively, and 13 liang of outputs of described change-over circuit connect the respective input of single-chip microcomputer 14 respectively.
Wherein, described change-over circuit 13 comprises a charging signals change-over circuit, this charging signals change-over circuit comprises series arm of being made up of some electronic switches 131 and the output circuit 132 that is connected with described series arm 131, and described series arm 131 cross-over connections are between the battery pack positive and negative electrode.
Described change-over circuit 13 also comprises a discharge signal change-over circuit, this discharge signal change-over circuit comprises series arm of being made up of some electronic switches 133 and the output circuit 134 that is connected with described series arm 133, and described series arm 133 cross-over connections are between the battery pack positive and negative electrode.
With reference to Fig. 2, in the present embodiment, U1, U2, U3 ... U7, U8, U9 are respectively cell b1, b2, b3 ... the voltage monitoring module of b7, b8, b9,1 pin of each voltage monitoring module and 2 pin are input, be connected with the positive and negative electrode of corresponding cell respectively, 3 pin of each voltage monitoring module and 5 pin are output, export the charge and discharge voltage detection signal A and the B of corresponding cell respectively.
Electronic switch in described series arm 131 and the series arm 133 all adopts the multiple tube of being made up of two triodes, be that example illustrates its composition with the electronic switch that is connected to voltage monitoring module U1 output (3 pin) below, as shown in Figure 2, the electronic switch that is connected to voltage monitoring module U1 output (3 pin) is formed multiple tube by triode Q3 and Q5, wherein, the base stage of Q3 is the control end of this electronic switch, this control end is connected with the output (3 pin) of U1, the negative pole of the emitter order body battery b1 of Q3, the collector electrode of Q3 is connected with the base stage of Q5, and the emitter and collector of Q5 is the input and the output of this electronic switch.
As shown in Figure 2, present embodiment is serially connected with divider resistance R1, R10, R20, R21 in described series arm 131 ... R56, R57, R65, divider resistance R1 one termination battery pack negative pole USB-wherein, the collector electrode of another termination triode of divider resistance R1 Q5, described output circuit 132 is made up of triode Q1, the emitter of triode Q1 meets battery pack negative pole USB-, the base stage of triode Q1 (being the input of output circuit 132) connecting resistance R2 is to the common port of divider resistance R1 and Q5, and the current collection of triode Q1 is the OVC output very; Be serially connected with divider resistance R3, R12, R24, R25 in the described series arm 133 ... R59, R60, R67, divider resistance R3 one termination battery pack negative pole USB-wherein, the collector electrode of another termination triode of divider resistance R3 Q8, described output circuit 134 is made up of triode Q2, the emitter of triode Q2 meets battery pack negative pole USB-, the base stage of triode Q2 (being the input of output circuit 134) connecting resistance R4 is to the common port of divider resistance R3 and Q8, and the current collection of triode Q2 is the OVD output very.
During battery pack work, if the voltage of all cells is all normal, the OVC output and the OVD output of change-over circuit 13 are all exported high level signal; Voltage as any joint cell exceeds when overcharging threshold voltage, and the output signal of correspondent voltage monitoring modular 12 is closed corresponding electronic switch in the change-over circuit 13, the OVC output output low level signal (being high limited signal) of change-over circuit 13; When the voltage of any joint cell exceeded the overdischarge threshold voltage, the output signal of correspondent voltage monitoring modular 12 was closed corresponding electronic switch in the change-over circuit 13, the OVD output output low level signal of change-over circuit 13 (promptly low limited signal).
In actual applications, the electronic switch in the change-over circuit 13 of the present invention can also adopt triode or field effect transistor.Described output circuit 132 and output circuit 134 can also adopt the field effect transistor inverter.
With reference to Fig. 3, in this battery pack protective circuit, U2 is a single-chip microcomputer, and current monitoring module 17 contains comparator U3A, U3B, and wherein the inverting input connecting resistance R23 of comparator U3A is to ground, and the in-phase end series resistor R24 of U3A, R18, R17, R3 are to ground; The inverting input series resistor R21 of comparator U3B, R17, R3 are to ground, the in-phase end connecting resistance R22 of U3B and the common port of R16; The public termination output Bout-of resistance R 18, R17, R21; Charging control switch 15 adopts field effect transistor MOC, and discharge control switch 16 adopts field effect transistor MOD.As the current sample element, because the resistance of the pipe of switching tube MOSFET is a constant, so the voltage drop on this pipe can reflect the size of the electric current that flows through to present embodiment with charging control switch MOC and discharge control switch MOD.During work; 7 pin of single-chip microcomputer U2 and 9 pin receive filling from OVC input and OVD input respectively; discharge voltage detection signal A '; (described OVC input is connected with OVC output among Fig. 2 B '; described OVD input is connected with OVD output among Fig. 2); 1 pin of single-chip microcomputer U2 and 3 pin receive charging current detection signal C and the discharging current detection signal D from current monitoring module 17 simultaneously; filling of single-chip microcomputer U2 analysis-by-synthesis battery pack; normally whether discharge condition; and then the break-make by its 10 pin and 11 foot control system charging control switch MOC and discharge control switch MOD, thereby reach the purpose of protecting battery pack.
This battery pack protective circuit also comprises a load detecting circuit; with reference to Fig. 3; described load detecting circuit is made of resistance R 3, the R17 of series connection; one termination output Bout-of resistance R 17; the negative pole USB-(promptly) of one termination battery pack of resistance R 3, the common port of resistance R 3, R17 (being output) connects 4 pin of single-chip microcomputer U2.After discharge control switch MOD ends, the load that is connected in the circuit will be moved 4 pin of U2 to high potential by resistance R 17, and after load removes, do not had extraneous high potential on draw, inner pull down resistor R3 will move 4 pin of U2 to electronegative potential, single-chip microcomputer U2 is by to the judgement of its 4 pin current potential, the access of promptly knowing load with shift out.
This battery pack protective circuit also comprises a charger testing circuit; with reference to Fig. 3; described charger testing circuit is made of resistance R 4, R19 and the R18 of series connection successively; one termination output Bout-of resistance R 18; one termination power Vcc of resistance R 4, the common port of resistance R 4, R19 (being output) connects 2 pin of single-chip microcomputer U2.After charging control switch MOC ends, the charger negative terminal voltage that is connected in the circuit will be moved 2 pin of U2 to electronegative potential by resistance R 18, R19, and after charger is removed, there be not the drop-down of extraneous negative voltage, internal pull-up resistor R4 pulls to a high potential to 2 pin of U2, single-chip microcomputer U2 is by to the judgement of its 2 pin current potential, the access of promptly knowing charger with shift out.
Fig. 4 is the control flow chart of this protective circuit; as shown in FIG.; single-chip microcomputer is according to the break-make of key parameter situations of change such as the charge and discharge current detection signal control charging and discharging circuit of the charge and discharge voltage detection signal of each cell in the battery pack and battery pack; simultaneously according to the access of load and charger with remove situation, whether decision recovers operate as normal.
Its concrete guard method is as follows:
1., each voltage monitoring module 12 butts up against the both positive and negative polarity current potential sampling of the cell Bn of its input, relatively, output is charging voltage detection signal A and discharge voltage detection signal B with reference to current potential with the electrode potential of tested cell Bn;
By change-over circuit 13 with all charge and discharge voltage detection signal A and B combination, to be converted to electrode potential USB-with battery pack be charge and discharge voltage detection signal A ', B ' with reference to current potential;
By current monitoring module 17 sampling battery pack loop currents, obtain electrode potential USB-with battery pack and be charging current detection signal C and discharging current detection signal D with reference to current potential;
2., single-chip microcomputer 14 receives above-mentioned charge and discharge voltage detection signal A ' and B '; and charge and discharge current detection signal C and D; normally whether the charge and discharge state of analysis-by-synthesis battery pack; and then the break-make of control charging control switch 15 or discharge control switch 16, reach the purpose of protecting battery pack.
Above-mentioned steps 2. in, the method that described single-chip microcomputer 14 carries out analysis-by-synthesis is as follows:
A, after charging voltage detection signal A ' surpasses normal value (threshold voltage overcharges) and turn-offs charging control switch, whether single-chip microcomputer judgement charger is removed, if charger is removed, after charging voltage is recovered normally, the conducting of Single-chip Controlling charging control switch is opened charge circuit again and is recovered charging;
B, after discharge voltage detection signal B ' is lower than normal value (overdischarge threshold voltage) and turn-offs discharge control switch, single-chip microcomputer judges that whether charger inserts, if charger inserts, after voltage recovers normally, the conducting of Single-chip Controlling discharge control switch recloses discharge loop;
C, after load short circuits is turn-offed discharge control switch, single-chip microcomputer detects load resistance, if load resistance is removed, the conducting of Single-chip Controlling discharge control switch recloses discharge loop;
D, after discharging current detection signal D surpasses normal value and turn-offs discharge control switch, single-chip microcomputer detects load resistance, if load resistance is removed, then controls the discharge control switch conducting, recloses discharge loop;
E, after charging current detection signal C surpasses normal value and turn-offs charging control switch, whether single-chip microcomputer judgement charger is removed, and removes as if charger, after charging voltage is recovered normally, the conducting of Single-chip Controlling charging control switch is opened charge circuit again and is recovered charging.
The present invention adopts the method that detects separately to the voltage of each cell in the series battery, voltage monitoring module 12 is worked in this section battery voltage range, therefore no matter how much save the cell series connection, for the comparator that constitutes the voltage monitoring module, only need bear the voltage of a batteries forever.Because all voltage monitoring modules are an identical independent circuits, irrelevant with the quantity of series-connected cell, therefore the very standardization of voltage comparator circuit of described voltage monitoring inside modules, lower and the high conformity of requirement of withstand voltage, be convenient to make, be convenient to control precision, also be convenient to mass and produce cheaply.
The present invention adopts the change-over circuit 13 of particular design; solved in the series battery protective circuit each voltage monitoring module 12 output charge and discharge voltage detection signal A, B with reference to the inconsistent problem of current potential; finally make all charge and discharge voltage detection signal A, B be converted to level signal A ', the B ' of the electrode potential USB-of unified relative battery pack, offer single-chip microcomputer.Electronic switch in the change-over circuit 13 all adopts triode to constitute, and is easily manufactured, thinks in theory, as long as the device withstand voltage of this part circuit is enough, just can construct the protective circuit of any multiple batteries series battery.
Because protective circuit is to be articulated in for a long time on the battery of battery pack; no matter battery when; protective circuit is all at the electric energy of consuming cells; this is a burden to battery; especially battery is because after the overdischarge, if in time do not charge, and protective circuit is also at consumed power; this is very unfavorable to battery, also can therefore cause battery complete failure when serious.Therefore, how reducing the secondary power loss of protective circuit, is that can protective circuit reach one of practical important indicator.The present invention is different with the conventional design thinking, the method of work of this circuit design is: no matter whether battery pack is in work, under the common situation, single-chip microcomputer always enters the low-power consumption sleep with circuit control, but at this moment the charging control switch of battery pack and discharge control switch are in opening state, allow the user to use arbitrarily.When the moment of the electric current generation ANOMALOUS VARIATIONS of any joint voltage of cell or battery pack; single-chip microcomputer is waken up; carry out entering low power consumpting state again after of short duration control upset is handled; design significantly reduces the secondary power loss of protective circuit like this, make the normal power consumption of entire circuit only be with the circuit power consumption of conventional method design 1/10th in addition also low.In addition along with the reduction of cell voltage; after entering the state of putting; control circuit enters not power consumption state fully to single-chip microcomputer under the prerequisite that charge circuit opens having kept; make the power consumption of protective circuit trend towards zero; this guard method meets the actual operating position of battery fully, makes protective circuit reach commercial requirement veritably.
According to the present invention, be easy to adopt commercially available components and parts structure, also be very easy to make special-purpose integrated circuit (ASIC).We adopt commercially available components and parts usually at present, can construct series battery protective circuit within 20 batteries easily.