JPH1098837A - Full charging detection of secondary battery and charging control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect change of charging current per unit time at the time of charging at a predetermined voltage of the second battery, forecast a charging time until the full charging depending on such amount of change to detect the full charging depending on the forecasting time. SOLUTION: A calculating section (CAL) 12d calculates [tfull] depending on the detected current received from a current detecting section (C-DET) 12b and a passage of time received from a clock section (TIM) 12c and sends [tfull] obtained by calculation to a full charge detecting section (FC-DET) 12e. The full charge detecting section (FC-DET) 12e recognizes, upon reception of [tfull] from the calculating section (CAL) 12d, the passage of time [tnow] in this timing from the measured data received from the clock section (TIM) 12c and compares [tfull] and [tnow] for detection of full charging.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting full charge of a secondary battery such as a lithium ion battery which requires constant voltage charge control, and a charge control device.

[0002]

2. Description of the Related Art Many information processing apparatuses, such as portable personal computers, which are easily carried, incorporate a secondary battery as an operating power source. In charge control of this type of secondary battery, when it reaches full charge,
Since charging is stopped immediately, a full charge detection function is indispensable.

Conventionally, lithium ion batteries have been widely used as secondary batteries in this kind of equipment. In the charge control of this lithium ion battery, it is necessary to perform charge control within a range not exceeding an allowable upper limit voltage due to inherent characteristics of the battery, and therefore, charge control by a constant voltage is required.

[0004] A conventional charge control technique for the above-described lithium ion battery and its problems will be described with reference to FIGS. 7 to 10. First, referring to FIGS. 7 and 8 and FIG.
The prior art will be described.

FIG. 7 is a diagram showing an example of a charging voltage / current characteristic of a lithium ion battery. As shown in FIG.
In the latter half of charging, the charging current (I) gradually decreases by constant voltage control. Here, it is determined that the battery is fully charged when the charging current reaches the current value [Ifull] at the time of full charge.

FIG. 8 is a block diagram showing an example of a circuit configuration of a conventional charging circuit for controlling charging of the above-mentioned lithium ion battery. In FIG. 8, the charging circuit (C
HG) 121 supplies charging power to a secondary battery (BATT) 120 composed of a lithium ion battery cell. The charge control unit (CHG-CONT) 122 controls the switch 123 to output a charge from the charging circuit (CHG) 121 to the secondary battery (BAT).
T) Turn on / off the power supply to 125.

A charge control unit (CHG-CONT) 1
Numeral 22 sequentially monitors a charging current [Inow] from the charging circuit (CHG) 121 to the secondary battery (BATT) 125 by an ammeter (C-MET) 124.

At the start of charging, a charge control unit (CHG-CON
T) 122 controls the switch 123 to charge the charging circuit (C
HG) 121 to the secondary battery (BATT) 125.

Charge control unit (CHG-CONT) 122
Stores the above current value [Iful] in advance,
Full charge is detected when [Inow ≦ Ifull] is reached. When full charge is detected, the charge control unit (CHG-CO
NT) 122 controls the switch 123 to control the charging circuit (C
HG) Stop charging from 121.

However, the above-mentioned prior art has the following problems. Ammeter (C-MET)
An example of the current value read at 124 is shown in FIG. Here, the actual current value changes continuously as shown in the graph (1) in the figure, but the current value read by the ammeter (C-MET) 124 is converted into a digital value as shown in the graph (2). Therefore, even if the read value of the ammeter (C-MET) 124 is [I1], the actual current value is [I1].
~ I2].

[0011] The maximum of this reading error is [Idigi
Assuming that the time from the start of charging to the end of charging due to full charge is [tfull], [tfull] is maximum [tdigit] due to the current error [Idit].
Will occur.

As described above, in the above-described prior art, there is a problem that a relatively large error may occur in the detection of the full charge. In addition, when such an error in the full charge time occurs, the current characteristic near the full charge has a small current change with respect to the time change, so that [tdigit] increases even with a small current error. . Further, in the vicinity of the full charge, the current capacity charged during [tdigit] is very small with respect to the entire charge current capacity, so that time is wasted.

As described above, in the above-mentioned prior art, there is a problem that a large waste of time is likely to be caused in the detection of the full charge at the time of charging. Next, a second prior art will be described with reference to FIGS. 9 and 10. FIG.

FIG. 9 is a block diagram showing a circuit configuration of the second prior art. In FIG. 9, a charging circuit (CHG) 1
31 supplies charging power to a secondary battery (BATT) 130. The switch 132 turns on / off charging. The ammeter (C-MET) 133 outputs a voltage value [V
now].

The comparing unit (COMP) 134 is connected to the [Vno
w] and the internal reference voltage, and the above [Vno
When [w] falls below the reference voltage, the switch 132 is turned off. Here, according to the full-charge detection current [Ifull],
The full charge detection voltage in the ammeter (C-MET) 133 is [Vfull], and the reference voltage in the comparison unit (COMP) 134 is [Vfull].

At the start of charging, the switch 132 is turned on, and the charging circuit (CHG) 131 supplies the secondary battery (BAT).
Power supply to the T) 130 is started. Comparison section (COM
P) 134 compares [Vnow] with [Vfull], turns off the switch 132 when [Vnow ≦ Vfull] is reached, and stops charging from the charging circuit (CHG) 131.

However, the above-mentioned prior art has the following problems. Ammeter (C-MET)
133 has a reading accuracy and a reading value has an error. [Iful]
1], an error occurs in the time for detecting full charge. Further, even if [Ifull] is set in consideration of the error, there is a variation in the error among the ammeters, and when the error is corrected uniformly, a difference in the full charge time occurs between the devices. Further, when the above error is corrected for each device, much time and labor is required for inspection and adjustment, and it is not practically used in consideration of the influence on manufacturing costs and the like.

When such an error in the full charge time occurs, the current characteristic near the full charge has a small current change with respect to the time change, so that even a small current error is [tdigit]. Becomes larger. Further, in the vicinity of the full charge, the current capacity charged during [tdigit] is very small with respect to the entire charge current capacity, so that time is wasted.

As described above, in the above-described prior art, there is a problem that a relatively large time variation occurs in the detection of the full charge and a large amount of time is wasted when charging.

[0020]

As described above, in the charging control of the secondary battery which requires the constant voltage charging control, conventionally, the detection of the full charge has a relatively large variation in time, and the charging is not performed. There has been a problem that a large amount of time is often wasted.

The present invention has been made in view of the above circumstances,
In charging control of a secondary battery that requires constant-voltage charging control, an error in charging time due to a reading error of a current value can be reduced to improve charging performance and shorten charging time. It is an object of the present invention to provide a method for detecting a full charge of a secondary battery and a charge control device.

[0022]

SUMMARY OF THE INVENTION In the present invention, when detecting the full charge of a secondary battery requiring constant voltage charge control, the charge current characteristic of the secondary battery (current characteristic during constant voltage charge) is determined. At the time of charging (characteristically, a relatively large portion of the current change) at the time of charging, the magnitude of the current change (gradient on the characteristic) is recognized, and the recognized magnitude of the current change is recognized by the battery. The full charge time (time until full charge) is predicted by applying a predetermined formula according to the characteristic. Full charge detection is performed based on the information on the predicted full charge time.
The above battery characteristics are uniform when the battery temperature is within a predetermined range.Therefore, by calculating the full charge time from the point where the change in the charge current per unit time is large, the influence of the time error can be minimized, Since the measured value is highly accurate, extremely accurate full charge detection can be performed.

That is, the present invention relates to a method for detecting a full charge of a secondary battery which requires constant voltage charge control, and detects a change amount of a charge current per unit time at a constant voltage charge of the secondary battery. The charging time until the battery is fully charged is predicted based on the change amount, and the full charging is detected based on the predicted time.

As described above, the charging time up to the full charge is predicted and detected based on the change in the charging current per unit time, and the full charge is detected based on the predicted time. The charging performance can be improved by eliminating the variation in time, and the charging time can be shortened. In particular, by calculating and predicting the full charge time at the point where the change in the charge current per unit time during constant voltage charging is large, the effect of the error in the full charge detection time can be minimized and the measured value can be highly accurate. As a result, the full charge detection can be accurately performed, and the charge can be completed promptly without intervening useless charging time immediately before the full charge detection.

The present invention also relates to a method for detecting full charge of a secondary battery requiring constant voltage charge control, wherein the battery temperature (battery solid temperature or ambient temperature of the battery) is determined when the secondary battery is charged at a constant voltage. , And the amount of change in charge current per unit time is detected, the charge time until full charge is estimated based on the battery temperature and the amount of change in current, and full charge detection is performed based on the estimated time. It is characterized by the following.

As described above, the amount of change in the charging current per unit time is detected, and the charging time until the battery is fully charged is predicted based on the battery temperature and the amount of current change. By having the function of performing full charge detection, it is possible to improve the charging performance and to shorten the charging time while compensating for the characteristic change due to the temperature change of the battery and eliminating the variation in the charging end time due to the current detection error. In particular, at points where the change in charging current per unit time during constant-voltage charging is large, the effect of errors in the full-charge detection time is minimized by calculating and predicting the full-charge time that compensates for changes in characteristics due to battery temperature. Since the measured value can be reduced and the measured value becomes highly accurate, the full charge detection can be accurately performed, and thereby the highly accurate charge can be completed promptly without intervening a wasteful charging time immediately before the full charge detection. .

According to another aspect of the present invention, there is provided a charging control apparatus for a secondary battery requiring constant voltage charging control, wherein a means for measuring a charging current and a charging time during the constant voltage charging of the secondary battery. Means for calculating the amount of change in charge current per unit time at the time of constant voltage charging of the secondary battery based on each of the measured values, and based on the amount of change in charge current per unit time Means for estimating the charging time until full charge according to a predetermined calculation formula, and monitoring the elapsed charging time based on the estimated charging time, and when the elapsed charging time reaches the estimated full charging time, the secondary battery becomes full. Means for detecting a state of charge.

As described above, the charging time until the battery is fully charged is predicted and detected by the change in the charging current per unit time, and the full charging is detected based on the predicted time. The charging performance can be improved by eliminating the variation in time, and the charging time can be shortened.

According to the present invention, there is provided a charge control device for a secondary battery requiring constant voltage charge control, wherein a charge current, a charge time, and a battery temperature during the constant voltage charge of the secondary battery are measured. Means for calculating a change amount of the charging current per unit time at the time of constant voltage charging of the secondary battery based on the measured charging current and charging time; and Means for predicting the charging time until full charge according to a predetermined calculation formula based on the amount of change and the measured battery temperature, and charging elapsed time by monitoring the charging elapsed time with the predicted charging time. Means for detecting a state of full charge of the secondary battery when the estimated full charge time has been reached.

As described above, the amount of change in the charging current per unit time is detected, the charging time until the battery is fully charged is estimated based on the battery temperature and the amount of change in the current, and based on the estimated time. By having the function of performing full charge detection, it is possible to improve the charging performance and to shorten the charging time while compensating for the characteristic change due to the temperature change of the battery and eliminating the variation in the charging end time due to the current detection error.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment of the present invention will be described with reference to FIGS. The first embodiment of the present invention detects the amount of change in charging current per unit time during constant voltage charging of a secondary battery, and predicts the charging time until full charge based on the amount of change. The full charge detection is performed based on the predicted time.

FIG. 1 is a diagram showing a charging current characteristic of a secondary battery for describing a method of detecting a full charge of the secondary battery according to the first embodiment of the present invention, where I is a charging current, and t is a constant. This is the charging elapsed time during voltage charging.

Since the secondary battery has an allowable upper limit voltage, its charging requires constant voltage charging. As shown in FIG. 1, the charging current I during the constant voltage charging gradually decreases as the charging progresses.

Here, the charging current when the battery is fully charged is [Ifull], the charging elapsed time during the constant voltage charging until the battery is fully charged is [tfull], and the charging time is arbitrary during the constant voltage charging. The charging current at the time is [Inow],
The elapsed charging time at this point is [tnow].

The charging current when the charging current starts to decrease further is [I1], the charging elapsed time at that time is [t1],
The charging current having a slightly smaller value is [I2],
The charging elapsed time at that time is defined as [t2].

Now, (t1, I1) is plotted on the graph shown in FIG.
And a straight line passing through (t2, I2) and an intersection with the t-axis being (ta, 0), the value of [ta] is [tful
l]. That is, [ta] and [tf
ul], there is a relational expression (for example, tfull
= M × ta + n (where m and n are constants).

Therefore, at the time of constant voltage charging before full charging, the full charging time can be obtained from the charging current and the elapsed time. That is, the magnitude of the change in the charging current per unit time is determined by a certain charging current at the time of constant voltage charging, and the magnitude of the change is applied to a predetermined relational expression to obtain the full charging time (the full charging state). Charging time to reach)
Can be predicted.

By detecting such a full charge, the full charge time is calculated and predicted at a point where the change of the charging current per unit time at the time of constant voltage charging is large, thereby minimizing the influence of the error of the full charge detection time. Since the size can be reduced and the measured value becomes highly accurate, extremely accurate full charge detection can be performed. Further, charging can be completed quickly without intervening useless charging time immediately before the detection of full charge.

FIG. 2 is a block diagram showing the configuration of the charge control device according to the first embodiment of the present invention to which the above-described full-charge detecting method of the present invention is applied. In FIG. 2, reference numeral 10 denotes a secondary battery (B) requiring charging at a constant voltage to be charged.
ATT) and 11 are for supplying a constant current to the secondary battery (BATT) 10.
A charging circuit (CHG) 12 for performing constant voltage charging includes a charging control unit (CHG-) that controls charging of the secondary battery (BATT) 10.
CONT).

Reference numeral 13 denotes a charge control unit (CHG-CONT) 1 interposed in a charging current path of the secondary battery (BATT) 10.
Reference numeral 14 denotes a charge control switch which is turned on / off by the reference numeral 2, and 14 denotes an ammeter (C-MET) for measuring a charging current.

Reference numerals 12a to 12f each constitute an internal component of the charge control unit (CHG-CONT) 12. Reference numeral 12a denotes an A / D converter for converting an analog measurement current of an ammeter (C-MET) 14 into a digital value. (A /
D).

Reference numeral 12b denotes an A / D converter (A / D) 12.
A current detection unit (C-DET) for detecting the current value digitally converted in a. 12c is a secondary battery (BATT)
10 is a timing unit (TIM) for measuring the elapsed charging time at the time of constant voltage charging of No. 10.

12d is a current detector (C-DET) 12b
The calculation unit (CA) calculates the above-described full charge time (the charge time [tfull] to reach the full charge state) as described above from the detected current and the elapsed time measured by the timer unit (TIM) 12c.
L).

Reference numeral 12e denotes the full charge time [tfull] calculated by the calculation unit (CAL) 12d and the time counting unit (TI).
M) A full charge detection unit (FC-DET) that detects the full charge of the secondary battery (BATT) 10 by comparing the elapsed time [tnow] measured at 12c.

12f is a full charge detection unit (FC-DET) 1
A switch control unit (SWC) that controls on / off of a charge control switch 13 interposed in a charging current path between the charging circuit (CHG) 11 and the secondary battery (BATT) 10 under the control of 2e. .

FIG. 3 is a flow chart for explaining the operation in the first embodiment. Here, the operation in the first embodiment of the present invention will be described with reference to FIGS.

Secondary battery (BATT) 10 to be charged
Is attached to a predetermined charging device, the charging control unit (CH
G-CONT) 12, a switch control unit (SW)
C) 12f switches on the charge control switch 13 to start charging the secondary battery (BATT) 10. At the time of this charging, the charging circuit (CHG) 11 controls the secondary battery (BA) by constant current / constant voltage control as shown in FIG.
TT) 10 is supplied with a charging current.

At the time of charging the secondary battery (BATT) 10, an ammeter (C-MET) 14 measures a charging current, and uses the measured current value as a charging control unit (CHG-CON).
T) 12 to the A / D converter (A / D) 12a (step S1 in FIG. 3).

The timer (TIM) 12c in the charge controller (CHG-CONT) 12 includes a secondary battery (BATT) 10c.
Is measured, and the measured time is sent to the calculation unit (CAL) 12d and sent to the full charge detection unit (FC-DET) 12e (step S2 in FIG. 3).

The A / D converter (A / D) 12a converts the current value measured by the ammeter (C-MET) 14 into a digital signal and sends it to the current detector (C-DET) 12b. Further, the current detection unit (C-DET) 12b has an A / D
A current value received from the converter (A / D) 12a is detected and sent to a calculation unit (CAL) 12d.

The calculation unit (CAL) 12d calculates [tfu based on the detected current received from the current detection unit (C-DET) 12b and the elapsed time received from the timer unit (TIM) 12c.
ll] is calculated, and [tfull] obtained by the calculation is sent to the full charge detection unit (FC-DET) 12e (step S3 in FIG. 3).

The full charge detection unit (FC-DET) 12e
When [tfull] is received from the calculation unit (CAL) 12d, the elapsed time [tnow] at that time is counted by the clock unit (TI
M) Recognize from the measurement data received from 12c, compare [tfull] and [tnow], and detect full charge (steps S4 and S5 in FIG. 3).

In the comparison between [tfull] and [tnow], if [tnow] has not reached [tfull], the above comparison is performed again after a predetermined time has elapsed. Also,
When [tnow] reaches [tfull], that is, [tn]
ow ≧ tfull], the secondary battery (BATT)
The switch control unit (SWC) 1 detects that the battery 10 is fully charged.
A full-charge detection signal is sent to 2f (FIG. 3, step S6).
).

When the switch control section (SWC) 12f receives the full charge detection signal from the full charge detection section (FC-DET) 12e, the switch control section 13 switches off the charge control switch 13 to terminate the charging of the secondary battery (BATT) 10. I do.

As described above, the amount of change in the charging current per unit time is detected, the charging time until the battery is fully charged is estimated based on the amount of change, and the full charge detection is performed based on the estimated time. By performing the above, the variation in the charging end time due to the current detection error can be eliminated, the charging performance can be improved, and the charging time can be shortened.

Next, a second embodiment of the present invention will be described with reference to FIGS.
An embodiment will be described. The second embodiment of the present invention detects the amount of change in the charging current per unit time, and determines whether the battery reaches a full charge based on the battery temperature (solid battery temperature or battery ambient temperature) and the amount of change in current. It is characterized in that a charging time is predicted and a full charge detection is performed based on the predicted time.

FIG. 4 is a diagram showing a charging current characteristic of the secondary battery for describing a method of detecting a full charge of the secondary battery according to the second embodiment of the present invention, where I is a charging current, and t is a constant. This is the charging elapsed time during voltage charging.

The secondary battery (BATT) has an allowable upper limit voltage, and requires constant voltage charging for charging. The charging current characteristic of this secondary battery (BATT) is as shown in FIG.
When the battery temperature is T1 ° C., the graph changes as shown in graph (A), and at T2 ° C., it changes as graph (B).

Here, the charging current when the battery is fully charged at the battery temperature T1 ° C. is [Ifull1], the elapsed time is [tfull1], and the battery is fully charged at the battery temperature T2 ° C. [Ifull2], the elapsed time thereof is [tfull2], and the charging current at a certain point in time at the battery temperature T1 ° C. is [Inow1].
The elapsed time is [tnow1], the charging current at a certain point in time at the battery temperature T2 ° C. is [Inow2], and the elapsed time is [tnow2].

Further, at the battery temperature T1 ° C., the charging current when the charging current starts to decrease is [I1], the elapsed time is [t1], and the charging current having a slightly smaller value is [I1]. I2], and the elapsed time is [t2].

Now, (t1, I1) and (t2,
A straight line passing through I2) is drawn, and the intersection with the t axis is (ta, 0)
Then, the value of [ta] is determined by the value of [tfull1]. That is, a certain relational expression (for example, tfull1 = m1 × ta) exists between [ta] and [tfull1].
+ N1 (m1, n1 are constants) holds.

Similarly, at the battery temperature T2 ° C., the charging current when the charging current starts to decrease is [I1], the elapsed time is [t3], and the charging current having a slightly smaller value is [I1]. I2], and the elapsed time is [t4].

Now, (t3, I1) and (t4,
A straight line passing through I2) is drawn, and the intersection with the t axis is (tb, 0)
Then, the value of [tb] is determined by the value of [tfull2]. That is, a certain relational expression (for example, tfull2 = m2 × tb) exists between [tb] and [tfull2].
+ N2 (m2, n2 are constants) holds.

Therefore, even if the battery temperature of the secondary battery changes during charging, it is possible to obtain a highly accurate full charging time from the charging current and the elapsed time before the secondary battery is fully charged. That is, the magnitude of the change in the charging current per unit time is determined by a certain charging current during constant voltage charging, and the magnitude of the change is applied to a relational expression determined by the battery temperature to obtain the full charging time (full charging time). Charging time to reach a state) can be predicted.

By detecting such a full charge, at a point where the change of the charging current per unit time at the time of constant voltage charging is large, the full charge time which compensates for the characteristic change due to the battery temperature is calculated and predicted. Since the influence of the error in the charge detection time can be minimized and the measurement value can be made highly accurate, extremely accurate full charge detection can be performed. Furthermore, highly accurate charging can be completed quickly without intervening useless charging time immediately before the detection of full charge.

FIG. 5 is a block diagram showing the configuration of the device according to the second embodiment of the present invention. In the figure, reference numeral 20 denotes a secondary battery (BAT) requiring constant voltage charging, which is to be charged.
T) and 21 are a charging circuit (CHG) for charging the secondary battery (BATT) 20 with a constant current and a constant voltage, and 22 is a secondary battery (BA)
Charge control unit (CHG-CON) that controls charging of the TT) 20
T).

Reference numeral 23 denotes a charge control unit (CHG-CONT) 2 interposed in a charging current path of the secondary battery (BATT) 20.
2 is a charge control switch whose on / off control is performed by the switch 2. Reference numeral 24 denotes an ammeter (C-MET) for measuring a charging current interposed in the charging current path.

Reference numeral 25 denotes a temperature sensor (TH) for measuring the battery temperature of the secondary battery (BATT) 20. The temperature sensor (TH) measures the measured temperature data in the charge control unit (CHG-CONT) 12 as described later. DET) 22e.

Reference numerals 22a to 22g each constitute an internal component of the charge control unit (CHG-CONT) 22. Reference numeral 22a denotes an A / D converter for converting an analog measurement current of an ammeter (C-MET) 24 into a digital value. (A /
D).

Reference numeral 22b denotes an A / D converter (A / D) 22
A current detection unit (C-DET) for detecting the current value digitally converted in a. 22c is a secondary battery (BATT)
This is a timekeeping unit (TIM) for measuring the elapsed time during the constant voltage charging of No. 20.

A temperature detector (T-DE) 22d detects the battery temperature [Tbat] of the secondary battery (BATT) 20 from the temperature data obtained from the temperature sensor (TH) 25.
T), and sends the detected battery temperature [Tbat] to a calculation unit (CAL) 22e described later.

22e is a current detection unit (C-DET) 22b
The full charge time [tfull] using a predetermined formula according to the detected current received, the measurement time received from the timer (TIM) 22c, and the battery temperature [Tbat] received from the temperature detector (T-DET) 22d. Calculation unit (CAL) that calculates
It is. Here, as shown in FIG. 4, the temperature detector (T
-DET) 22d, a calculation formula is selected according to the battery temperature [Tbat] received from the current detection unit (C-DET) 22b.
A full charge time [tfull] of the rechargeable battery (BATT) 20 is calculated from the detected current received and the measurement time received from the timer (TIM) 22c.

Reference numeral 22f denotes the full charge time [tfull] calculated by the calculation unit (CAL) 22e and the time counting unit (TIM) 2
A full charge detection unit (FC-DET) that detects the full charge of the secondary battery (BATT) 20 by comparing the elapsed time [tnow] measured in 2c.

22g is a full charge detection section (FC-DET) 2
A switch control unit (SWC) that controls ON / OFF of a charge control switch 23 interposed in a charging current path between the charging circuit (CHG) 21 and the secondary battery (BATT) 20 under the control of 2f. .

FIG. 6 is a flowchart for explaining the operation in the second embodiment. Here, the operation in the second embodiment of the present invention will be described with reference to FIGS.

A secondary battery (BATT) 20 to be charged
Is attached to a predetermined charging device, the charging control unit (CH
G-CONT) 22, a switch control unit (SW)
C) 22g switches on the charge control switch 23 to start charging the secondary battery (BATT) 20. At the time of this charging, the charging circuit (CHG) 21 has a constant current
The charging current is supplied to the secondary battery (BATT) 20 by the constant voltage control.

At the time of charging the secondary battery (BATT) 20, an ammeter (C-MET) 24 measures a charging current and uses the measured current value as a charging control unit (CHG-CON).
T) 22 to the A / D converter (A / D) 22a (step S11 in FIG. 6).

A timer (TIM) 22c in the charge controller (CHG-CONT) 22 measures the elapsed time when the secondary battery (BATT) 20 is charged at a constant voltage, and calculates the measured elapsed time in the calculator (CAL). 22d (step S12 in FIG. 6).

The A / D converter (A / D) 22a converts the current value measured by the ammeter (C-MET) 24 into a digital signal, and sends it to the current detector (C-DET) 22b. The current detector (C-DET) 22b detects the current value received from the A / D converter (A / D) 22a and sends it to the calculator (CAL) 22e.

The temperature sensor (TH) 25 measures the battery temperature of the secondary battery (BATT) 20 and transmits the measured temperature data to a temperature detector (T-DET) in the charge controller (CHG-CONT) 22. ) 22d.

The temperature detector (T-DET) 22d detects the battery temperature [Tbat] of the secondary battery (BATT) 20 from the temperature data obtained from the temperature sensor (TH) 25,
Calculator (CAL) 22 calculates the detected battery temperature [Tbat].
e (step S13 in FIG. 6).

The calculation unit (CAL) 22e is a current detection unit (C
-DET) 22b and the timer (TI)
M) Measurement time received from 22c and temperature detector (T-DE)
T) The full charge time [tfull] is calculated using a predetermined formula according to the battery temperature [Tbat] received from the 22d. Here, as shown in FIG. 4, the temperature detector (T-D
ET) The calculation formula is selected according to the battery temperature [Tbat] received from the secondary battery (Tbat), and the secondary battery ( The full charge time [tfull] of the BATT) 20 is calculated, and this [tfull] is sent to the full charge detection unit (FC-DET) 22f (step S14 in FIG. 6).

The full charge detector (FC-DET) 22f
When [tfull] is received from the calculator (CAL) 22e, the elapsed time [tnow] at that time is counted by the timer (TI).
M) Recognize from the measurement data received from 22c, compare [tfull] and [tnow], and detect full charge (steps S15 and S16 in FIG. 6).

In the comparison between [tfull] and [tnow], if [tnow] has not reached [tfull], the above comparison is performed again after a predetermined time has elapsed. Also,
When [tnow] reaches [tfull], that is, [tn]
ow ≧ tfull], the secondary battery (BATT)
The switch control unit (SWC) 2 detects that the battery 20 is fully charged.
A full charge detection signal is transmitted to 2g (step S1 in FIG. 6).
7).

When the switch control section (SWC) 22g receives the full charge detection signal from the full charge detection section (FC-DET) 22f, the switch control section 23 switches off the charge control switch 23 to terminate the charging of the secondary battery (BATT) 20. I do.

As described above, at the point where the change of the charging current per unit time during the constant voltage charging is large, the full charging time compensating for the characteristic change due to the battery temperature is calculated and predicted, whereby the full charging detection time is calculated. Since the influence of the error can be minimized and the measured value becomes highly accurate, extremely accurate full charge detection can be performed. As a result, correct charging can be completed quickly without intervening useless charging time immediately before full charge detection.

In each of the embodiments described above, only one time (t1) per unit time is set so that the present invention can be easily understood.
−t2, or t3-t4), the full charge time [tfull] is calculated from the change in the charging current. [Tfull] is calculated at each of a plurality of different points, and the calculation is performed by a plurality of calculations. Taking the average of [tfull] makes it possible to detect the full charge time with higher accuracy.

The predicted full charge time [tfull]
, It is also possible to display the full charge completion time at the present time. In addition, when detecting the amount of change in the charging current per unit time, the sampling period for current detection is made different, and current detection is performed with a plurality of sampling periods, so that a periodic external signal such as an external clock can be detected. Stable and reliable full charge time detection can be performed even with respect to noise.

In the above embodiment, after calculating the full charge time [tfull], [tfull] is calculated at a predetermined cycle.
Although full charge detection is performed by comparing [full] with [tnow], for example, it is also possible to provide a hardware timer, set [tfull] in the timer, execute a time count, and perform full charge detection. It is.

In each of the above embodiments, [tno
w] reaches [tfull], that is, [tnow ≧ t
[full], it is also possible to add means for checking whether or not the charge current value of the secondary battery (BATT) is equal to or less than a preset full charge current value.

[0091]

As described above, according to the present invention, in the charging control of a secondary battery requiring constant voltage charging control, the error in the charging time due to the error in reading the current value is eliminated, and the charging performance is reduced. And a method for detecting a full charge of a secondary battery and a charge control device capable of shortening the charge time.

That is, according to the present invention, in the method of detecting full charge of a secondary battery that requires constant voltage charge control, the amount of change in charge current per unit time is detected during constant voltage charge of the secondary battery. Then, the charging time until the battery is fully charged is predicted based on the amount of change, and the full charging is detected based on the predicted time. The performance can be improved and the charging time can be shortened. In particular, by calculating and predicting the full charge time at the point where the change in the charge current per unit time during constant voltage charging is large, the effect of the error in the full charge detection time can be minimized and the measured value can be highly accurate. From
Full charge detection can be accurately performed, and furthermore, the charge can be completed promptly without intervening useless charging time immediately before the full charge detection.

Further, according to the present invention, in the method for detecting full charge of a secondary battery that requires constant voltage charge control, the battery temperature (battery solid temperature or ambient temperature of the battery) may be detected when the secondary battery is charged at a constant voltage. Temperature) and the amount of change in charging current per unit time, and predicts the charging time to full charge based on the battery temperature and the amount of change in current, and detects full charge based on the predicted time. By performing the above, it is possible to improve the charging performance by eliminating the variation of the charging end time due to the current detection error while compensating the characteristic change due to the temperature change of the battery,
The charging time can be reduced. In particular, at the point where the change in charging current per unit time during constant voltage charging is large, the effect of the error in the full charge detection time is minimized by calculating and predicting the full charge time that compensates for the characteristic change due to battery temperature. Since the measurement can be made smaller and the measurement value becomes more accurate, the full charge detection can be accurately performed, and the highly accurate charge can be completed quickly without intervening the useless charging time immediately before the full charge detection.

Further, according to the present invention, in a charging control apparatus for a secondary battery requiring constant voltage charging control, a charging current and a charging time at the time of constant voltage charging of the secondary battery are measured. Means, means for calculating the amount of change in charging current per unit time at the time of constant voltage charging of the secondary battery based on the measured values, and means for calculating the amount of change in charging current per unit time. Means for predicting the charging time until full charge according to a predetermined calculation formula, and monitoring the elapsed charging time based on the predicted charging time, and when the elapsed charging time reaches the estimated full charging time, the secondary battery is charged. With the configuration including the means for detecting the fully charged state, it is possible to eliminate the variation of the charging end time due to the current detection error, thereby improving the charging performance and shortening the charging time.

According to the present invention, in a secondary battery charge control device requiring constant voltage charge control, the charge current, charge time, and battery temperature during constant voltage charge of the secondary battery are determined. Means for measuring, means for calculating the amount of change in charging current per unit time during constant voltage charging of the secondary battery based on the measured charging current and charging time, and charging current per unit time Means for predicting the charging time until full charge according to a predetermined formula based on the amount of change of the measured battery temperature and the elapsed charging time by monitoring the elapsed charging time based on the estimated charging time. Means for detecting a full charge state of the secondary battery when the battery reaches a predicted full charge time. End time roses By eliminating the yellow, it is possible to improve the charging performance, can shorten the charging time.

[Brief description of the drawings]

FIG. 1 is a diagram showing charging current characteristics of a secondary battery for describing a method of detecting a full charge of the secondary battery according to the first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a charge control device according to the first embodiment of the present invention.

FIG. 3 is a flowchart for explaining an operation in the device of the first embodiment.

FIG. 4 is a view showing a charging current characteristic of the secondary battery for describing a method of detecting a full charge of the secondary battery in the first embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a charge control device according to the first embodiment of the present invention.

FIG. 6 is a flowchart for explaining an operation in the device of the first embodiment.

FIG. 7 is a diagram showing an example of a charging voltage / current characteristic of a lithium ion battery.

FIG. 8 is a block diagram showing a configuration example of a charge control circuit according to a first conventional technique.

FIG. 9 is a block diagram showing a configuration example of a charge control circuit according to a second conventional technique.

FIG. 10 is a diagram showing an example of a current value for explaining an operation of a charge control circuit according to a conventional technique.

[Explanation of symbols]

 10, 20 ... secondary battery (BATT), 11, 21 ... charging circuit (CHG), 12, 22 ... charging control unit (CHG-CONT), 12a, 22a ... A / D converter (A / D), 12b, 22b: current detector (C-DET), 12c, 22c: timer (TIM), 12d, 22e: calculator (CAL), 12e, 22f: full charge detector (FC-DET), 12f, 22g: switch Control part (SWC), 13,23 ... Charge control switch, 14,24 ... Ammeter (C-MET), 22d ... Temperature detection part (T-DET), 25 ... Temperature sensor (TH).

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Katsuo Ozawa 1381-1 Shinmachi, Ome-shi, Tokyo Toshiba Computer Engineering Co., Ltd. (72) Inventor Takayuki Shiono 1381-1 Shinmachi, Ome-shi, Tokyo Toshiba Computer TA Engineering Co., Ltd.

Claims (4)

[Claims] In a charge control of a secondary battery requiring constant voltage charge control, a change amount of a charge current per unit time is detected at the time of constant voltage charge of the secondary battery, and the change amount is detected. A method for detecting a full charge of a secondary battery, wherein a charge time until a full charge is estimated based on the estimated charge time and a full charge is detected based on the estimated time. 2. In the charging control of a secondary battery requiring constant voltage charging control, a battery temperature and a change amount of a charging current per unit time are detected during the constant voltage charging of the secondary battery, A method for detecting a full charge of a secondary battery, comprising predicting a charge time until a full charge based on the battery temperature and the amount of change in current, and performing a full charge detection based on the predicted time. 3. A charge control device for a secondary battery that requires constant voltage charge control, comprising: means for measuring a charge current and a charge time during constant voltage charge of the secondary battery; Means for calculating the amount of change in charge current per unit time during constant voltage charging of the secondary battery based on the measured value; and a predetermined calculation formula based on the amount of change in charge current per unit time. Means for estimating the charging time until the battery is fully charged, and monitoring the elapsed charging time based on the estimated charging time, and detecting the fully charged state of the secondary battery when the elapsed charging time reaches the estimated full charging time. A charging control device, comprising: 4. A charge control device for a secondary battery requiring constant voltage charge control, comprising: means for measuring a charge current, a charge time, and a battery temperature during constant voltage charge of the secondary battery; Means for calculating the amount of change in charging current per unit time during constant voltage charging of the secondary battery based on the measured charging current and charging time; and Means for estimating the charging time until full charge according to a predetermined formula based on the measured battery temperature; and And a means for detecting a full charge state of the secondary battery when the charge control time has been reached.