CN1391717A - Method for charging battery - Google Patents

Abstract

In order to accurately balance the charge and discharge of the battery, an arbitrary load located in the battery circuit is used as a measuring shunt. For this purpose, the reduced voltage on the measuring branch is detected by a capacity counter and integrated over a period of time in such a way that an integrated signal is generated, wherein switching on or off is based on this integrated signal Controlled charging switch.

Description

Method for battery charging

The invention relates to a method for charging a battery of an electrical device, in particular a mobile phone, by means of a charging circuit according to the preamble of claim 1 .

For many electronic and electrical appliances to be operated without, at least temporarily, a direct connection to the grid, especially mobile or cordless telephones, mainly rechargeable accumulators are arranged. For reuse in mobile operation, such accumulators are charged either in the stationary part of the respective device or in a separate charging station, also called a charging case. In this case, via a charging energy source, usually via a charging device connected to the grid, a charging current adjusted to the accumulator used is generated and transmitted to the accumulator. In this case, on the one hand, particular care must be taken not to overcharge the accumulators, which can lead to power losses especially in the case of relatively frequent overcharging, while on the other hand the accumulators should always provide their maximum capacity as far as possible.

In order to meet the last-mentioned requirement, supplementary charging must be carried out in accordance with the own consumption of the device, for example a mobile phone, taking into account the charging efficiency of the accumulator. The charging efficiency of a battery cell corresponds to an efficiency of less than 1, so more energy must always be supplied to the battery than has been withdrawn. The coefficient that should be multiplied by the consumed capacity in order to obtain the amount of current that should be supplemented by charging is called the charging coefficient. This charge factor is usually set fixed so that smaller cells with less capacity cannot be overcharged and damaged.

The charging current is usually measured with a measuring resistor located in the charging circuit. Such a shunt resistance is also called a measuring shunt [shunt (English) = shunt]. The current in the load circuit, the discharge or the load current, is known for certain operating conditions of the load and is therefore usually not measured but determined according to the operating conditions of the load. For example, after the analog/digital conversion, the two variables are fed to a control unit and balanced there by a software.

Due to the determination of the discharge current or the load current, errors often occur in the balancing. Unaccounted-for boundary conditions by which the load current is limited are the cause of these errors, but these boundary conditions are not taken into account in the balance when determining the load current using the operating state or operating state of the load. Examples of these boundary conditions are the dispersion of the electronic components, the different voltage states of the battery, and the dynamic current consumption.

But now with the necessary accuracy and taking into account changing boundary conditions - different voltage states of the battery, dynamic current consumption - and taking into account the dispersion of electrical components determined by the deviation, the charging and discharging current curves Accurate measurements are often difficult and only possible with great effort.

The object underlying the invention is to achieve a very precise balancing of the battery charge with simple and inexpensive equipment.

Proceeding from the method specified in the preamble of claim 1 , this object is solved by the features specified in the characterizing features of claim 1 .

For this purpose, according to claim 1, a load located in the battery circuit is used as the measuring branch, wherein this functional load must have a voltage drop that is proportional to the charging or discharging current. The voltage proportional to the voltage drop in the measuring branch is integrated over a time by a means for volume counting, so that a signal representing the integration of the voltage drop is generated. Based on this integrated signal, a control signal is again generated which controls the controlled charging switch in such a way that both charging and discharging are detected by the capacity counter device without knowledge of the charging and discharging currents of the accumulator.

This method allows the use of any loads already contained in the battery circuit which have the stated properties. If an additional load, for example a resistor, is still provided for the function of the measuring branch, inexpensive electrical components can be used, since possible deviations of the measuring branch used are eliminated in the method according to the invention.

Furthermore, the advantage of selecting the measuring branch within the battery circuit is that both the charging current and the discharging current (load current) are detected, so that possible variations of the boundary conditions, which are reflected in the measured values, can be monitored when balancing the charge capacity. compensate.

A fuse in the battery circuit has the advantage that it has a voltage drop and protects the battery circuit against damage, for example due to short-circuit currents.

Resistors, first of all certain resistors with large deviations in their resistance values, are very advantageous in terms of procurement and also allow a dimensioning of the battery circuit.

If the resistance of a conductor section of the circuit located in the battery circuit is used as the measuring shunt, the acquisition costs for the measuring shunt are completely dispensed with.

To increase the charging efficiency of the charging circuit - the battery discharges less than it charges - the charge and discharge currents are multiplied by different coefficients before balancing the charge and discharge currents.

A more accurate balance is achieved by amplifying the voltage drop across the measuring branch.

The use of comparators allows the adjustment of a threshold value from which the charging switch should be switched over. This results in an additional flexibility in the control of the charging switch in order to compensate, for example, errors in the detection of the switching condition, or to implement an adjustable hysteresis which prevents the charging switch from being switched continuously.

The development according to claim 8 has the advantage of saving devices for generating the control signals and thus of further simplification and cost reduction.

An exemplary embodiment of the invention is explained with reference to FIGS. 1 to 2 . Shown here:

FIG. 1 shows a model of a circuit arrangement for carrying out the method according to the invention.

FIG. 2 shows the distribution and relationship of several important circuit-technical variables when carrying out the method according to the invention.

FIG. 1 shows a model of an electrical device EG that can be connected via a coupling device to a charging circuit _UL ,R.

In the coupled state, the charging circuit is closed at the closed controlled charging switch GLS and charges the accumulator AK located in the electrical system EG. Such a controlled charging switch GLS is designed, for example, as a transistor which has a corresponding wiring for its function as a switching transistor.

A control signal ST for switching the controlled charging switch GLS is generated by a comparator V2 located in the charging circuit, for example realized by a correspondingly wired operational amplifier.

For this purpose, the wiring of the comparator V2 is dimensioned in such a way that a desired reference voltage, in particular with a value of 0 volts, is present, which is compared with an integral signal KP, wherein after the integral signal KP When the value of the reference voltage is reached, the control signal ST is generated with a value such that the controlled charging switch GLS interrupts the charging circuit.

It is also possible to implement a hysteresis which prevents the controlled charging switch GLS from switching continuously by means of a suitable wiring.

As an alternative thereto, the integral signal KP can also be used directly as control signal ST.

The integral signal KP is generated by a capacity counter KAP located in the charging circuit. For this purpose, the voltage U _S ' applied to the capacity counter KAP is integrated within the time specified by the timer ZG.

The voltage U _S ' is the result of multiplying the reduced voltage U _S on the measuring shunt MS by a first or a second coefficient, wherein the reduced voltage U _S is multiplied by the first coefficient in negative sign and Multiplied by the second coefficient when positive sign. The multiplication is carried out by an amplifier V1 , in which case such an amplifier V2 is realized, for example, by at least one operational amplifier with corresponding wiring which is dimensioned such that they guarantee the first and the second amplification factor. Different weightings of the charging current I _L and the discharging current I _E can be carried out by differential multiplication of the two coefficients in order to thus achieve a compensation for the charging efficiency—the accumulator AK is charged more than discharged.

In addition, both coefficients can be selected in such a way that they amplify the reduced voltage U _S on the measuring shunt MS if, for example, the reduced voltage U _S can only have very small values that cannot be used for the capacity counter KAP.

Alternatively, amplification and/or differential multiplication can also be dispensed with, so that the proportional voltage U _S ′ corresponds to the reduced voltage U _S in terms of absolute value and/or sign.

A fuse SI which is itself part of the battery circuit is selected as measuring shunt MS. The resistance value of fuse SI is responsible for the drop in voltage U _S at measuring shunt MS designed as fuse SI during charging and discharging of accumulator AK. This reduced voltage U _S is proportional to the charging current I _L or the discharging current I _E depending on its position in the battery circuit, so that the analysis for balancing the charging current I L and the discharging current I _E can be performed without knowing these parameters. The voltage U _S of the discharge current I _E .

Instead of fuse SI, a resistor in the battery circuit can also be used as measuring shunt MS. It is also possible to use a line section in the battery circuit as measuring shunt MS in order to reduce costs, for example, since a line section has a - even a small - resistance value and thus likewise reduces the voltage U _S .

There is also the possibility of designing a circuit implementing the method according to the invention as an integrated circuit, the values to be detected being digitized so that they are used, for example, by a control unit for balancing.

For this purpose, integration can be performed, in particular in certain discrete time intervals specified by a timer.

In this case, for example, a microprocessor already present in the electrical device can be used as the control unit, wherein the software must be adapted to the method.

FIG. 2 shows the distribution and the relationship of several important circuit-technical parameters when implementing the balancing method according to the invention for battery charging with unknown charging current I _L and discharging current I _E. The illustrated distribution of the reduced voltages has been chosen arbitrarily here and should only be used to illustrate the correlation. By balancing based on the reduced voltage U _S on the measuring shunt MS, the following conditions should be met here:

Q _L = Q _E

Q _L represents the charge input (charge) and is derived from:

Q _L ＝I _L *t＝(U _S *t)/R _S , U _S is positive,

_QE represents the charge acquired (discharge) and is derived from:

Q _E ＝I _E *t＝(U _S *t)/ _RS , U _S is negative,

In the formula, R _S represents the resistance value of the measuring shunt MS adopted, and t represents time.

For a selected time interval (0;τ), the reduced voltage U _S is integrated so that an integral signal KP is obtained as follows: $\mathrm{KP}=\underset{0}{\overset{\mathrm{\τ}}{\∫}}-u_S*\mathrm{dt}$

It follows from these correlations that the accumulator AK is not fully charged when the integral signal KP is not equal to a value of zero. The controlled charging switch GLS is therefore closed (switched on) when integrating these values of the signal KP.

The stated values and conditions relate to ideal values which may deviate in practice, eg for circuit-technical reasons, or to approach them.

The described exemplary embodiments represent only some of the possible embodiments of the invention. Therefore, a person skilled in the art has the ability to create many other embodiments through advantageous variants without changing the characteristic (essence) of the invention - accurate balancing of the charging of the accumulators without knowledge of the charging and discharging currents and discharge. These embodiments are likewise included by the invention.

Claims (8)

1. be used for by means of a kind of charging circuit (U _L, R) give electric equipment (EG), especially the method for at least a storage battery (AK) of mobile phone charging is characterized in that,

A) adopt a kind of load that is arranged in storage battery (AK) circuit as measurement shunt (MS), a kind of and charging current I _LOr discharging current I _EVoltage (the U of proportional distribution _S) in this load, reduce,

B) by a kind of device (KAP) that is used for capacity counting so to (MS) goes up the voltage (U that reduces measuring along separate routes _S) proportional voltage (U _S') carry out integration through the time, make to generate a kind of integrated signal (KP),

C) depend on the control signal (ST) that integrated signal (KP) generates a kind of switch controlled charging switch (GLS),

D) by control signal (ST) switch controlled charging switch (GLS) like this, make volumeter counting apparatus (KAP) both survey the charging of storage battery (AK), also survey the discharge of storage battery (AK).

2. by the method for claim 1, it is characterized in that, adopt a kind of safeties (SI) of storage battery (AK) circuit that are arranged in as measuring (MS) along separate routes.

3. by the method for claim 1, it is characterized in that, adopt a kind of resistance of storage battery (AK) circuit that is arranged in as measuring (MS) along separate routes.

4. by the method for claim 1, it is characterized in that the resistance that adopts a kind of lead that is arranged in storage battery (AK) circuit is as measuring (MS) along separate routes.

5. by the method for one of above claim, it is characterized in that will measuring along separate routes, (MS) goes up the voltage (U that reduces _S) by amplifier stage (V1) when the negative sign and a kind of first multiplication, and when positive sign and a kind of second multiplication, make it as proportional voltage (U _S') be sent on the volumeter counting apparatus (KAP).

6. by the method for one of above claim, it is characterized in that, will make and measure the voltage (U that reduction is gone up in shunt (MS) by amplifier stage (V1) _S) absolute value of a kind of coefficient of multiplying each other is chosen as greater than 1, makes and will measure the voltage (U that goes up reduction along separate routes _S) as proportional voltage (U _S') be sent on the volumeter counting apparatus (KAP).

7. by the method for one of above claim, it is characterized in that, generate control signal (ST), as the comparative result of integrated signal (KP) with a kind of adjustable threshold by a kind of comparator stage (V2).

8. by the method for one of claim 1 to 6, it is characterized in that, adopt integrated signal (KP) as control signal (ST).

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