JPH0865910A - Battery charger - Google Patents

Abstract

PURPOSE: To accurately detect the full charge of a secondary battery from a temperature differential value by setting the threshold at the time of judging the temperature differential value, according to the temperature region of a battery, and making the threshold in a region where nonlinearity appears in temperature detection smaller than that in a linear region. CONSTITUTION: A microcontroller 20 inputs thermistor voltage Vt and a battery voltage partial voltage value Vb into a battery temperature detector 43 and a battery voltage detector 44 through ADD converters 41 and 42, respectively. A charge controller 50 outputs a temperature differential threshold value table 55 corresponding to the temperature region, based on the information of the temperature region where the battery temperature judged by the battery temperature judger 45 exists. A temperature differential value judging part 54 judges the temperature differential value by contrast with this temperature differential threshold value. On the other hand, a battery condition judger 47 judges whether the batter is normal or not from the battery voltage, and the charge controller 50 generates a quick charge control signal 51, a trickle control signal 52, and a charge start signal 53, based on this information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for secondary batteries, and more particularly to a charging device suitable for rapid charging of alkaline secondary batteries such as nickel-hydrogen secondary batteries and nickel-cadmium secondary batteries.

[0002]

2. Description of the Related Art In a quick charger for charging a secondary battery in a short time, it is judged that the battery is fully charged, and the rapid charging is terminated. Various methods for determining full charge have been considered, one of which is the temperature differential detection method.
This utilizes the temperature differential of the battery, that is, the amount of temperature rise per unit time rapidly increases at the end of charging, and when this temperature differential reaches a certain threshold value, for example, 1 ° C / min, full charge is performed. It is a method of determining.

FIG. 5 shows changes in battery temperature TB and battery voltage VB with respect to time when a nickel-hydrogen secondary battery is rapidly charged at a constant current. As shown in the figure, since the battery temperature TB rises rapidly at the end of charging, the temperature rise amount per unit time, that is, the temperature differential is detected, and the temperature differential value (dT
By detecting that / dt) has reached the threshold value, full charge can be detected.

To detect the battery temperature TB, a thermistor is usually used, and the phenomenon that its resistance value changes with temperature is used. Here, since the resistance value of the thermistor with respect to temperature change shows non-linearity as shown in FIG. 6, the resistance value change is not detected as it is, but the fixed resistor R and the thermistor are connected in series as shown in FIG. A method is adopted in which a constant DC voltage is applied across the series circuit to detect the terminal voltage (hereinafter referred to as the thermistor voltage) Vt of the thermistor. The change in the thermistor voltage Vt with respect to the battery temperature TB at this time can be approximated to a straight line as shown in FIG.
In this case, in the region b of FIG. 8, the relationship between the battery temperature TB and the thermistor voltage Vt shows a straight line, and the temperature differential value dT / dt is proportional to the differential value dVt / dt of the thermistor voltage, so the thermistor voltage Vt is differentiated. Thus, the temperature differential value dT / dt can be accurately detected.

However, in the regions a and c on both sides of the region b in FIG. 8, the thermistor voltage V with respect to the change of the battery temperature TB.
The change in t becomes non-linear, and the change in the thermistor voltage Vt with respect to the same change in battery temperature TB is smaller than that in the region b. That is, since the temperature differential value dT / dt is not proportional to dVt / dt in the regions a and c, the temperature differential value dT / dt cannot be accurately obtained even if the thermistor voltage Vt is differentiated. I cannot capture the changes in TB correctly.

This means that unless the temperature change per unit time is larger in the regions a and c, the temperature differential value does not become the same value as that of the region b, so that the detection of full charge is detected by detecting the temperature differential value. Means to be delayed. As a result, the battery is overcharged, which shortens the battery life and causes liquid leakage.

[0007]

As described above, in the conventional rapid charging apparatus using the temperature differential detection method, the full charge can be accurately detected by the temperature differential detection due to the non-linearity of the temperature detecting element. However, there is a problem that it may cause overcharge.

The present invention has been made in order to solve the problems of the conventional quick charging device using the temperature differential detection method, and it is necessary to more accurately judge the full charge so as not to cause the overcharge. It is an object of the present invention to provide a charging device for a secondary battery as described above.

[0009]

In order to solve the above-mentioned problems, the present invention relates to a charging device having a function of rapidly charging a secondary battery by a temperature differential detection method, depending on the detected temperature range of the battery temperature. This is characterized in that the threshold value for determining the temperature differential value is changed.

That is, the rechargeable battery charging device according to the present invention includes a temperature detecting means for detecting the temperature of the rechargeable battery, and a temperature which is a temperature rise amount per unit time of the temperature detected by the temperature detecting means. Temperature differential detection means for obtaining a differential value, charge control means for terminating the rapid charging when the temperature differential value obtained by the temperature differential detection means reaches a predetermined threshold value, and detected by the temperature detection means. And a threshold value setting means for setting the threshold value based on the determination result of the determination means. Is characterized by.

The secondary battery charging device according to the present invention has a linear region in which the detected value linearly changes with respect to the temperature of the secondary battery and a nonlinear region in which the detected value changes nonlinearly. A temperature detecting means for detecting the temperature, a temperature differential detecting means for obtaining a temperature differential value which is an amount of temperature rise per unit time of the temperature detected by the temperature detecting means, and a temperature differential value obtained by the temperature differential detecting means. Charging control means for terminating the rapid charging when the value reaches a predetermined threshold value, and a temperature detected by the temperature detecting means in a first temperature region corresponding to the linear region or in the non-linear region. A determination unit that determines whether the temperature is in the corresponding second temperature region, and the threshold value is set when the determination unit determines that the temperature detected by the temperature detection unit is in the first temperature region. First And a threshold value setting means for setting the threshold value to a second value smaller than the first value when it is determined to be in the second temperature range. .

[0012]

As described above, in the present invention, the threshold value for determining the temperature differential value is set according to the temperature range of the detected battery temperature, and in the region where the nonlinearity of the temperature detection appears, the linearity region is set. Also, by reducing the threshold value, the full charge of the secondary battery can be accurately detected from the temperature differential value. As a result, the possibility of overcharging due to detection error of full charge is reduced, and the problems of battery life shortening and liquid leakage are solved.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit configuration diagram of a secondary battery charging device showing an embodiment according to the present invention. In FIG. 1, a battery pack 1 includes a secondary battery (hereinafter, simply referred to as a battery) 2 such as an alkaline secondary battery and a thermistor 3 for temperature measurement arranged near the battery 2 in a housing. is there. FIG.
Shows a state in which the battery pack 1 is set in the charging device 4. A mobile phone or other device in which the battery pack 1 is incorporated may be set in the charging device 4.

The charging device 4 is constructed as follows. The charging device 4 has a commercial AC power source 5 (for example, 100V)
Power from is input and filter 6 for noise removal
After being converted into a direct current by the rectifying / smoothing circuit 7 via, the signal is supplied to the primary side of the transformer 8. On the primary side of the transformer 8,
A switching transistor 9 composed of a power MOS transistor is connected via a resistor 10. The switching transistor 9 is a PWM (pulse width modulation) circuit 1
It is switched by the output of 1. As a result, a pulse current flows in the primary side of the transformer 8 and energy is transmitted to the secondary side of the transformer 8. The output generated on the secondary side of the transformer 8 is converted into a direct current by the rectifying and smoothing circuit 12,
It is supplied as a charging current to the battery 2 through the quick charging transistor 13 or the series circuit of the trickle charging transistor 14 and the resistor 15 and further through the backflow prevention diode 16. The output of the rectifying / smoothing circuit 12 is also supplied to the light emitting element 18 of the photocoupler 17, and the output of the light receiving element 19 of the photocoupler 17 is input to the PWM circuit 11.

The microcontroller 20 is mainly composed of a microcomputer, and controls the quick charging transistor 13, the trickle charging transistor 14, the photocoupler 17 and the LED 31. This microcontroller 20 has a voltage at the connection point between the resistor 21 and the thermistor 3 (hereinafter referred to as the thermistor voltage).
Vt and a voltage Vb obtained by dividing the voltage VB of the battery 2 by the resistors 22 and 23 (hereinafter, referred to as a battery voltage division value) Vb are input.

The resistors 24-29 and the operational amplifier 30 are
It is provided for controlling the charging current to be constant. The inverting input terminal of the operational amplifier 30 receives the terminal voltage of the resistor 24 that is inserted in series in the charging path and detects the charging current via the resistor 27, and the non-inverting input terminal of + 5V.
A voltage (reference voltage) obtained by dividing the power supply voltage of 2 by the resistors 25 and 26 is input via the resistor 28. Operational amplifier 30
A resistor 29 is connected between the inverting input terminal and the output terminal, and the gain of the operational amplifier 30 is determined by the resistors 27 and 29. The output terminal of the operational amplifier 30 is connected to the side of the light emitting element 18 of the photocoupler 17 opposite to the side connected to the output terminal of the rectifying / smoothing circuit 12. With such a configuration, feedback control is performed so that the inverting input terminal and the non-inverting input terminal of the operational amplifier 30 have the same potential.

For example, when the charging current of the battery 2 is large and the terminal voltage of the current detecting resistor 24 is large, the inverting input terminal of the operational amplifier 30 has a higher potential than the non-inverting input terminal thereof, so that the operational amplifier 30 has a higher potential. Output voltage decreases, and the current flowing through the light emitting element 18 increases. As a result, the output pulse width of the PWM circuit 11, that is, the on-time width of the switching transistor 9 is shortened, the energy transmitted to the secondary side of the transformer 8 is reduced, and the charging current is reduced.

On the contrary, when the charging current of the battery 2 is small,
Since the inverting input terminal of the operational amplifier 30 has a lower potential than the non-inverting input terminal thereof, the output voltage of the operational amplifier 30 increases and the current flowing through the light emitting element 18 decreases, so that the PWM
The output pulse width of the circuit 11, that is, the on-time width of the switching transistor 9 increases, and the energy transmitted to the secondary side of the transformer 8 increases, so that the charging current increases.

In this way, the resistance 2 depending on the charging current
Feedback control is performed so that the terminal voltage of No. 4 and the reference voltage obtained by the resistors 25 and 26 become equal to each other, and the charging current is subjected to constant current control.

The microcontroller 20 controls by software processing using a microcomputer. FIG. 2 shows a functional block diagram of the microcontroller 20.

In FIG. 2, the thermistor voltage Vt and the battery voltage division value Vb are converted into digital values by the A / D converters 41 and 42, respectively, and then the battery temperature detection unit 4
3 and the battery voltage detector 44, respectively, to obtain the battery temperature TB and the battery voltage VB. The output of the battery temperature detection unit 43 is input to the battery temperature determination unit 45 and the temperature differential calculation unit 46. The battery temperature determination unit 45 determines what temperature range (temperature range) the battery temperature is in. Specifically, it determines whether the battery temperature is in a normal range and It is determined which of a plurality of predetermined temperature regions is in. The temperature differential calculation unit 46 calculates the temperature differential of the battery, that is, the amount of temperature rise per unit time.

The output of the temperature differential calculation unit 46 is input to the temperature differential value determination unit 54. The temperature differential value determination unit 54 compares the temperature differential value obtained by the temperature differential calculation unit 46 with the temperature differential threshold value read from the temperature differential threshold value table 55 to determine the magnitude relationship between the two. . The temperature differential threshold value table 55 stores the relationship between the temperature region of the battery temperature and the temperature differential threshold value in a memory such as a ROM.

On the other hand, the output of the battery voltage detection unit 44 is input to the battery state determination unit 47. The battery state determination unit 47
It is determined from the battery voltage whether or not the battery 2 is normal. The output of the A / D converter 41 is also input to the battery pack set detection unit 48. Battery pack set detector 48
Is for detecting whether or not the battery pack 1 is set in the charging device 4.

A / D converter 41, battery temperature determination unit 45,
The outputs of the battery state determination unit 47, the battery pack set detection unit 48, and the temperature differential value determination unit 54 are input to the charging control unit 50, and the charging control unit 50 uses the outputs to rapidly charge the rapid charging transistor 13. A charge control signal 51, a trickle charge control signal 52 for the trickle charging transistor 14, and a charge start signal 53 are generated. The charge start signal 53 is supplied to one end of the resistor 28 in FIG.

Further, the charging control unit 50 differentiates the temperature corresponding to the temperature region from the temperature differential threshold value table 55 based on the determination result of the battery temperature determining unit 45, that is, the information of the temperature region in which the battery temperature exists. The control of reading the threshold value and giving it to the temperature differential value determination unit 54 is also performed.

Next, the operation of this embodiment will be described with reference to the flowcharts shown in FIGS. 3 to 4 and FIG. First, the thermistor voltage Vt is read via the A / D converter 41 (step 101). When the battery pack 1 is set in the charging device 4, the thermistor voltage Vt is +5 up to then.
It decreases from V due to the partial pressure of the thermistor 3 and the resistor 21. Here, the thermistor voltage Vt is a predetermined value (for example,
4.8 V) or less, the battery pack set detection unit 48
Thus, it is detected that the battery pack 1 is set in the charging device 4 (step 102).

When the set of the battery pack 1 is detected in step 102, the battery temperature calculator 43 converts the thermistor voltage Vt into temperature data to calculate the battery temperature TB (step 103), and then the battery temperature determiner 4
According to 5, it is determined whether the battery temperature TB is in the range of 0 ° C. or higher and 40 ° C. or lower (step 104). When the battery temperature TB falls within the range of 0 ° C. ≦ TB ≦ 40 ° C., the battery voltage divided value Vb is subsequently read via the A / D converter 42 and the battery voltage VB is obtained by the battery voltage detection unit 44. (Step 105), and further battery state determination unit 4
Based on the battery voltage VB, it is determined by 7 whether the battery 2 is normal (step 106). Specifically, when the battery voltage VB per unit cell is within the range of 1.0V≤VB≤1.7V, the battery 2 is determined to be normal. Here, if the battery 2 is not normal, the process ends and rapid charging is not performed.

If the result of determination in step 106 is that the battery 2 is normal, the process proceeds to step 107 in FIG. 4 and rapid charging is performed. That is, when the quick charge control signal 51 output from the charge control unit 50 becomes “L” level,
When the quick charge transistor 13 is turned on and the charge start signal 53 becomes "L" level, quick charge is performed. During this period, the LED 31 is controlled by the microcontroller 20 and lights up to indicate that the rapid charging is being performed. Further, during this rapid charging, the charging current is kept constant by the above-mentioned feedback control.

During this rapid charging, step 10
8 to 112, the battery temperature determination unit 4 in the charging control unit 50
5 and the temperature differential threshold value table 55, the temperature differential threshold value is set (changed), and the temperature differential value determination unit 54 determines the temperature differential value.

That is, assuming that the battery temperature at the boundary between the area a and the area b in FIG. 8 is Ta and the battery temperature at the boundary between the area b and the area c is Tb, first, the battery temperature detecting unit 45 in the battery temperature detecting unit 45. The battery temperature TB detected at 43 is in the region b
That is, it is determined whether or not it is in the region of Ta <TB <Tb (step 108). If the result of this determination is YES, the temperature differential value threshold is set to THb, and the temperature differential value determination unit 54 determines whether dT / dt ≧ THb (step 109). Here, if YES in step 109, it is determined that the battery is fully charged and the rapid charging is stopped, and if NO, the process returns to step 107 to continue the rapid charging.

On the other hand, if NO in step 108, the battery temperature determination unit 45 subsequently determines whether TB≤Ta (step 110). As a result of this judgment,
If YES, the temperature differential threshold value is set to THa, and the temperature differential value determination unit 54 determines whether dT / dt ≧ THa (step 111). Here, if YES in step 111, it is determined that the battery is fully charged and the rapid charging is stopped, and if NO, the process returns to step 107 to continue the rapid charging.

Further, if NO in step 110, the temperature differential threshold value is set to THc, and the temperature differential value determination section 54 determines whether dT / dt ≧ THc (step 112). Here, in step 112, YE
If it is S, it is determined that the battery is fully charged and the quick charge is stopped.
If it is O, the process returns to step 107 to continue the rapid charging.

If YES in steps 109, 111 and 112 and full charge is detected, both the rapid charge control signal 51 and the charge start signal 53 are "H".
When the level is reached, quick charging is stopped.

Here, three temperature differential threshold values THa,
The relationship between THb and THc is selected as THb> THa, THc. However, THa and THc may be different or equal. As described in the related art, in FIG. 8, the thermistor voltage Vt changes linearly with respect to the battery temperature TB in the region b, while the region a,
Since it changes non-linearly in c, the change in the thermistor voltage Vt with respect to the same battery temperature TB is smaller than that in the region b, and the temperature differential value dT / dt is also small. Therefore, when the full charge is detected by comparing the temperature differential value dT / dt in the regions b and the regions a and c with the same temperature differential threshold value, when the full charge is detected in the regions a and c, the full charge is detected. There is a time delay in the detection of.

On the other hand, according to the present invention, the temperature differential thresholds THa and THc in the regions a and c are set to be smaller than the temperature differential threshold THb in the region b, so that the time delay of such full charge detection is delayed. The battery 2 can be prevented from being overcharged.

The present invention is not limited to the above embodiment, but can be implemented with various modifications. For example, in the above-described embodiment, the temperature region is divided into three regions a, b, and c in FIG. 8 for determination, but region a is a temperature region corresponding to immediately after rapid charging, and in this region a, full charge detection is performed. Does not necessarily have to be done.

That is, for example, (1) when the battery is brought from a low ambient temperature environment to a high temperature environment for rapid charging, or (2) when there is an overheated heat due to the heat generation of the charger itself, or ( 3) In the case of rapid charging of an over-discharged battery, a full charge may be erroneously detected immediately after the start of charging, which may cause insufficient charging. May not determine the full charge by temperature differential detection. In FIG. 2, the timer 49 measures the elapsed time from the start time of the rapid charge, and the charge control unit 50 does not detect the full charge based on the determination result of the temperature differential value determination unit 54 until, for example, 5 minutes have elapsed. Can be realized by doing so.

In this case, since the battery temperature TB passes through the area a in FIG. 8 before the timer 49 times out, it is judged whether the detected battery temperature TB is in the area a or not. The control for setting the differential threshold is unnecessary. Further, the determination of the temperature region of the detected battery temperature TB and the change of the temperature differential threshold value based on the determination may be performed in more regions.

[0039]

As described above, according to the present invention, in the charging device of the type in which the full charge is determined by the temperature differential detection of the secondary battery to stop the rapid charging, the temperature range of the detected battery temperature is detected. The threshold value for determining the temperature differential value is changed according to the temperature differential value, and for example, in the region where the nonlinearity of the temperature detection appears, the threshold value is made smaller than that of the linear region, so that the temperature differential value of the secondary battery It is possible to accurately detect the full charge, prevent overcharging due to detection error of the full charge, and solve the problems of battery life shortening and liquid leakage.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a secondary battery charging device according to an embodiment of the present invention.

FIG. 2 is a functional block diagram of the microcontroller in FIG.

FIG. 3 is a diagram showing a part of a flowchart for explaining the operation of the embodiment.

FIG. 4 is a view showing another part of the flowchart for explaining the operation of the embodiment.

FIG. 5 is a diagram showing changes over time in battery temperature and battery voltage during rapid charging.

FIG. 6 is a diagram showing characteristics of resistance value change with temperature change of the thermistor.

FIG. 7 is a diagram showing a configuration of a temperature detection unit in which a thermistor and a fixed resistor are combined.

8 is a diagram showing changes in the terminal voltage of the thermistor in FIG. 7 with respect to changes in temperature.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Battery pack 2 ... Secondary battery 3 ... Thermistor 4 ... Charging device 5 ... Commercial AC power supply 6 ... Filter 7 ... Rectification smoothing circuit 8 ... Transformer 9 ... Switching transistor 11 ... Pulse width modulation circuit 12 ... Rectification smoothing circuit 13 ... Rapid Charge transistor 14 ... Trickle charge transistor 16 ... Backflow prevention diode 17 ... Photocoupler 20 ... Microcontroller 30 ... Operational amplifier 32 ... Discharge transistor 41 ... A / D converter 42 ... A / D converter 43 ... Battery temperature Calculation unit 44 ... Battery voltage detection unit 45 ... Battery temperature determination unit 46 ... Temperature differential calculation unit 47 ... Battery state determination unit 48 ... Battery pack set detection unit 49 ... Timer 50 ... Charge control unit 51 ... Rapid charge control signal 52 ... Trickle Charge control signal 53 ... Charge start signal 54 ... Temperature differential value determination unit 55 ... Temperature differential Threshold table

Claims (2)

[Claims] 1. A charging device having a function of rapidly charging a secondary battery, comprising temperature detecting means for detecting the temperature of the secondary battery, and a temperature rise per unit time of the temperature detected by the temperature detecting means. Temperature differential detecting means for obtaining a temperature differential value which is an amount; charge control means for terminating the rapid charging when the temperature differential value obtained by the temperature differential detecting means reaches a predetermined threshold value; Determination means for determining which of a plurality of predetermined temperature regions the temperature detected by the means is, and threshold setting means for setting the threshold value based on the determination result of the determination means. A charging device for a secondary battery, comprising: 2. A charging device having a function of rapidly charging a secondary battery, having a linear region in which a detected value linearly changes with respect to a temperature of the secondary battery and a nonlinear region in which the detected value nonlinearly changes. A temperature detecting means for detecting the temperature of the secondary battery, a temperature differential detecting means for obtaining a temperature differential value which is a temperature increase amount per unit time of the temperature detected by the temperature detecting means, and a temperature differential detecting means for obtaining the temperature differential value. Charging control means for terminating the rapid charging when the obtained temperature differential value reaches a predetermined threshold value, and whether the temperature detected by the temperature detecting means is in a first temperature region corresponding to the linear region. Determination means for determining whether the temperature is in a second temperature region corresponding to the non-linear region, and the determination unit determines that the temperature detected by the temperature detection device is in the first temperature region. Threshold setting means for setting the threshold to a first value and setting the threshold to a second value smaller than the first value when it is determined that the temperature is in the second temperature range. A rechargeable battery charging device, comprising: