JPH0898423A - Charger for secondary battery - Google Patents

Abstract

PURPOSE: To prevent undercharge and overcharge by ending the boosting charge if a voltage detected by a voltage detecting means, at a point in time when a temperature derivative detected through a temperature derivative detecting means reaches a set value, exceeds a predetermined value. CONSTITUTION: A thermistor voltage Vt and a divided battery voltage Vb are converted through A/D converters 41, 42 into digital values which are then fed to a battery temperature calculating section 43 and a battery voltage detecting section 44, respectively. Output from the battery temperature calculating section 43 is fed to a battery temperature deciding section 45 and a temperature derivative calculating section 46. Output from the battery voltage detecting section 44 is fed to a battery state deciding section 47 and a charge control section 50. When a decision is made, at the deciding section 54, that the temperature derivative calculated at the calculating section 46 has reached a set value and the battery voltage detected at the detecting section 44 is higher than a predetermined value, the charge control section 50 decides that the battery is fully charged to end the boosting charge otherwise continue the boosting charge. This circuitry can prevent undercharge and overcharge.

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 a secondary battery, and more particularly to a charging device suitable for rapid charging of an alkaline secondary battery such as a nickel-cadmium secondary battery or a nickel-hydrogen secondary battery.

[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 temperature rise amount per unit time rapidly increases at the end of charging, and it is determined that the battery is fully charged when the temperature differential reaches a predetermined value, for example, 1 ° C / min. It is a method to do.

By the way, in this temperature differential detection type quick charger, it is usual that the determination of full charge by temperature differential detection is not performed for a fixed time (for example, 5 minutes) from the start of the rapid charge. For example, when a battery used outdoors (eg, 0 ° C.) is brought indoors (eg, 25 ° C.) for quick charging in a cold area such as a ski resort, the battery temperature and the ambient temperature are initially different from each other. Because the temperature difference is large, the amount of temperature rise per minute exceeds 1 ° C. even immediately after the start of charging, and it may be determined that the battery is fully charged even though it is not fully charged. In such a case, the battery is naturally insufficiently charged.

Therefore, for example, a time of 5 minutes is set as the time for the temperature rise of the battery to settle due to the ambient temperature,
During this period, the full charge determination is not performed by the temperature differential detection, and 5
A method of performing temperature differential detection after a lapse of minutes has been considered. In this way, the temperature rise due to charging can be reliably captured, and full charge can be correctly determined.

However, in this method, when the battery is brought into the room from a low temperature outdoors and charged, the full charge is not erroneously determined, but the fully charged battery which has already been charged is recharged. If it does, the full charge is not judged for 5 minutes after the start of charging, so 5 minutes + 1 minute = 6 minutes will be recharged even if the battery is fully charged. It may be charged. Also, the temperature differential detection is not 1 ° C./min, but is 4 ° C./min.
In the case of 4 minutes, rapid charging will be stopped after 5 minutes of temperature differential non-detection time + 9 minutes of 4 minutes of temperature differential detection unit time, so overcharging will be performed for 9 minutes. The battery temperature rises, for example, 25 ° C. or more, and the deterioration of the battery progresses.

Further, as a possibility of erroneous determination of full charge due to a temperature differential value other than the case described above, there is a case where the temperature of the battery pack rises due to the heat generated by the charger, causing the temperature to rise. That is, when the amount of heat generated by the charger increases immediately after the start of charging, the amount of temperature rise per minute exceeds 1 ° C. due to flapping heat, and it may be determined that the battery is fully charged even though it is not fully charged. In such a case, the charge will still be insufficient.

[0007]

As described above, in the conventional quick charger using the temperature differential detection method, when the battery is brought from an environment having a low ambient temperature to a high environment for quick charging, or when the charger generates heat. If the temperature of the battery rises due to flapping heat, full charge may be erroneously detected immediately after the start of charging, resulting in insufficient charging. If the determination of full charge based on detection is not performed, there is a problem in that when a battery that has already been charged is recharged, overcharge occurs and the battery deteriorates.

The present invention has been made in order to solve the above-mentioned problems of the quick charger by the conventional temperature differential detection method, and there is no shortage of charge due to erroneous determination of full charge. It is an object of the present invention to provide a charging device for a secondary battery, which is free from the risk of being overcharged by rapidly charging the battery.

[0009]

A charging device for a secondary battery according to the present invention comprises a 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, voltage detecting means for detecting the voltage of the secondary battery, and the voltage when the temperature differential value obtained by the temperature differential detecting means reaches a set value. Charging control means for terminating the rapid charging when the voltage detected by the detection means is equal to or higher than a predetermined value.

More specifically, it has a means for detecting the voltage of the secondary battery, reads the battery voltage when the temperature differential value reaches a set value, and if the battery voltage VB is a predetermined value VBC, for example, full charge. If the battery voltage is higher than the value corresponding to the battery voltage during charging, the battery is considered to be fully charged and the rapid charging is terminated, and if the battery voltage is VBC or less, it is determined that the battery is not yet fully charged and the rapid charging is continued. To do so.

Here, when the battery voltage has temperature characteristics during rapid charging, it is desirable to perform temperature correction of VBC or the detected battery voltage from the current battery temperature.

[0012]

As described above, according to the present invention, the temperature differential value of the battery is calculated in order to determine whether the secondary battery is set in the charging device, the rapid charging is started, and the battery is fully charged. When the battery voltage VB is reached, the battery voltage VB is read, and when it is VB or more than the set value VBC prepared for comparison in advance, it is regarded as full charge, and the quick charge is terminated. Conversely, VBC is VB
When the temperature differential value does not reach the full charge, it is determined that the full charge has not been reached, and even if the temperature differential value reaches the set value, it is ignored and the rapid charge continues as before. During rapid charging, the temperature differential value is constantly calculated, this value reaches the set value again, and VBC ≤ VB
When it becomes, make sure to terminate the quick charge.

That is, in the present invention, it is noted that even if the temperature differential value of the battery reaches the set value, the battery voltage that is not fully charged is low, and the battery voltage that is fully charged is high. The full charge is accurately determined in consideration of both the battery voltage and the battery voltage.

By correcting the temperature of VBC or VB, the battery voltage VB close to the full charge can be grasped without being affected by the temperature change, so that the full charge can be detected more accurately.

In this way, according to the present invention, a battery that is not in a fully charged state is not erroneously determined to be fully charged, and insufficient charging is prevented. When a fully charged battery is set and rapid charging is performed, the temperature differential value reaches the set value due to a rapid increase in the battery temperature in a short time (for example, 2 minutes), but the battery voltage VB at that time is V because it is fully charged
Since it is larger than BC, the rapid charging is immediately completed in, for example, 2 minutes, so that the overcharge amount can be suppressed to a minimum.

[0016]

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. 1 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 a microcomputer, and controls the quick charging transistor 13, the trickle charging transistor 14, the photocoupler 17, and the LED 31. The microcontroller 20 has a voltage Vt (hereinafter referred to as the thermistor voltage) Vt at a connection point between the resistor 21 and the thermistor 3, and a resistor 2
The voltage Vb obtained by dividing the voltage VB of the battery 2 by 2 and 23 (hereinafter referred to as the battery voltage division value) Vb is 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, 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 divided value Vb are converted into digital values by the A / D converters 41 and 42, respectively, and then the battery temperature calculation 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 calculation unit 43 is input to the battery temperature determination unit 45, the temperature differential calculation unit 46, and the charge control unit 5.

The battery temperature determination unit 45 determines the temperature range of the battery voltage. The temperature differential calculation unit 46 calculates the temperature differential of the battery, that is, the amount of temperature rise per unit time. The unit time information required in this case is transmitted to the temperature differential calculation unit 46 via the timer value transmission line 55.

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 sets the temperature differential value obtained by the temperature differential calculation unit 46 to a set value,
For example, the magnitude is judged by comparing with 1.0 (° C./min).

On the other hand, the output of the battery voltage detection unit 44 is input to the battery state determination unit 47 and the charging control unit 50. The battery state determination unit 47 determines whether the battery 2 is normal based on the battery voltage. The output of the A / D converter 41 is also input to the battery pack set detection unit 48. The battery pack set detection unit 48 detects whether or not the battery pack 1 is set in the charging device 4.

The temperature correction ROM 56 is used when temperature-correcting a predetermined value to be compared with the battery voltage or the battery voltage itself, as will be described later, and a table showing the relationship between the battery temperature and the battery voltage / temperature correction value. Is described as.

A / D converter 41, battery temperature calculation unit 43,
The outputs of the battery temperature determination unit 45, the battery state determination unit 47, the battery pack set detection unit 48, the temperature differential value determination unit 54, and the temperature correction ROM 56 are input to the charging control unit 50, and the charging control unit 50 outputs these outputs. On the basis of the quick charge control signal 51 to the quick charge transistor 13, the trickle charge control signal 52 to the trickle charge transistor 14,
And a charge start signal 53 is generated. The charge start signal 53 is supplied to one end of the resistor 28 in FIG.

Further, the charging control unit 50 sends unit time information to the temperature differential calculation unit 46 via the timer value transmission line 55 based on the output (timer value) of the timer 49 for measuring the elapsed time from the start of the rapid charging. give. Further, the timer 49 is also used as a timer for the rapid charging time and a timer for the trickle charging time, and the charging control unit 50 monitors by the timer 49 whether or not the rapid charging time and the trickle charging time have reached predetermined times.

The charging control by the charging control unit 50 is characteristic of the present invention in that the temperature differential value judging unit 54
It is determined that the temperature differential value obtained by the temperature differential calculating unit 46 has reached a set value, for example, 1.0 (° C./min), and the battery voltage detected by the battery voltage detecting unit 44 is the predetermined value VBC.
In the above case, the battery 1 is considered to be fully charged and the quick charge is terminated. Even if it is determined that the temperature differential value has reached the set value, if the battery voltage does not reach the predetermined value, the quick charge is continued. is there.

Next, the operation of the charging device of this embodiment will be described with reference to the flow charts shown in FIGS.

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 decreases from + 5V until then due to the partial pressure of the thermistor 3 and the resistor 21. Here, the thermistor voltage Vt
Is less than a predetermined value (for example, 4.8V), the battery pack 1 is detected by the battery pack set detection unit 48.
Is set (step 102).

When the set of the battery pack 1 is detected in step 102, the battery temperature calculation unit 43 converts the thermistor voltage Vt into temperature data to calculate the battery temperature TB (step 103), and then the battery temperature determination unit 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 trickle charge control signal 52 subsequently output from the charge control unit 50 becomes “L” level, and the trickle charge transistor 14 is turned on. Then, trickle charging is performed (step 105). Thereafter, the battery voltage division value Vb is read via the A / D converter 42 (step 106), the battery voltage VB is obtained by the battery voltage detecting unit 44, and the battery voltage VB is further obtained by the battery state determining unit 47.
It is determined from B that the battery 2 is normal (step 1
07). Specifically, the battery voltage VB per unit cell is 1.
When 0V ≦ VB ≦ 1.7V, the battery 2 is judged to be normal. Here, if the battery 2 is not normal, the process ends and rapid charging is not performed.

When the battery 2 is normal, the timer 49 is started (step 108), the elapsed time from the charging start time is measured, and the timer value of this timer 49 (the elapsed time from the charging start time) is set. The temperature differential amount is input to the temperature differential calculating unit 46 via the timer value transmission line 55, and the temperature increase amount per unit time (for example, 1 minute), that is, the temperature differential value is calculated (step 109). Then, the charging control unit 5
When the quick charge control signal 51 output from 0 goes to "L" level, the quick charge transistor 13 turns on, and the charge start signal 53 goes to "L" level to perform quick charge ( Step 11
0). During this time, the LED 31 turns the microcontroller 20
It lights up under the control of and indicates that quick charging is being performed. Further, during this rapid charging, the charging current is kept constant by the above-mentioned feedback control.

Next, in steps 111 and 112, the battery voltage VB per unit cell is the same as in steps 106 and 107.
Is in the range of 1.0V≤VB≤1.7V, and in steps 113 and 114, the battery temperature during rapid charging is checked. If any of the battery voltage VB and the battery temperature is abnormal, the process proceeds to step 117, and the quick charging is stopped to ensure safety.

Further, during this rapid charging, if the temperature differential value calculated in step 109 in the temperature differential value determining section 54 is 1.0 ° C./min or more, it is temporarily determined to be full charge, and the process proceeds to step 116. If so, it is determined that the battery is not fully charged, and the process returns to step 109 (step 115). Step 15
If it is provisionally determined that the battery is fully charged, the current battery voltage VB is further read to check whether VB is equal to or higher than a predetermined value VBC. If VB ≧ VBC, the process proceeds to step 117. If not, the process proceeds to step 109. Return (step 116).

Here, the meaning of the processing of step 116 will be described with reference to FIG. FIG. 5 shows that I =
The time change of the battery voltage VB and the battery temperature TB when flowing 1.0 C amperage is shown. Trickle charging is performed 50 minutes after the start of charging. 40 of FIG.
Reference numeral 1,402 indicates the time when the temperature differential value becomes 1.0 ° C./minute or more, which is the predetermined value, in step 115 of FIG.

Here, the battery voltage at the time of 401 is about 1.2 V, and the predetermined value VBC (here, VBC = 1.45).
V), the determination result of step 16 in FIG. 4 is N.
When it becomes O, the process returns to step 109, and the rapid charging is continued. That is, for example, when the battery temperature suddenly rises because a battery pack that has been placed outdoors and is cold is brought into a high-temperature room and rapid charging is started, or when the battery temperature suddenly rises due to the flapping heat generated by the heat generated by the charger. As described above, even if the temperature differential value reaches the set value and it is determined that the battery is fully charged, if the battery temperature does not reach the predetermined value VBC, the full charge determination is regarded as an error and the rapid charging is continued. By doing so, it is possible to solve the problem of uncharging (insufficient charging capacity) due to an erroneous determination of full charge.

Next, as shown in FIG.
At time 402 after the minute, the temperature differential value becomes the set value of 1.0 ° C./min or more, but the battery voltage VB at this time is about 1.5 V, which is higher than the predetermined value VBC, so steps 115 and 116 are executed.
After that, it is determined that the battery is fully charged, and the quick charging is ended. In addition,
As a characteristic of the alkaline secondary battery, since the battery voltage VB rises as shown in FIG. 5 when fully charged, a voltage close to VB in the fully charged state is set as the predetermined value VBC.

As described above, when the answer is YES in step 116, the full charge is true, so that the rapid charge is stopped in step 117. In this case, the microcontroller 2 of FIG.
At 0, the quick charge control signal 51 is set to "H" level, and the quick charge transistor 13 is turned off. At the same time, the charge start signal 53 is set to "H" level to stop the feedback to the PWM circuit 11 for constant current control of the quick charge current.

In the next step 118, the microcontroller 20 starts the trickle charge timer (for example, 10 hours), sets the trickle charge control signal 52 to "L" level, and turns on the trickle charge transistor 14. After 10 hours, the trickle charge timer times out and the charging ends. Although omitted in FIG. 1, it is assumed that the PWM circuit 11 functions so that the output voltage of the rectifying / smoothing 12 becomes a constant voltage when the quick charge start signal becomes “H” level. The constant voltage output of the rectifying / smoothing circuit 12 is used as trickle charging energy and energy supplied from the microcontroller 20 to the LED 31.

FIG. 6 shows the relationship between the ambient temperature during charging and the battery voltage. That is, the horizontal axis represents the amount of charge and the vertical axis represents the battery voltage VB, and the relationship between them is shown with the ambient temperature as a parameter. As shown in the figure, when the battery temperature is high, the battery voltage at the time of rapid charging has a lower characteristic. On the contrary, when the battery temperature is low, the battery voltage at the time of rapid charging becomes high. In the above description, step 116 of FIG. 4 and FIG.
Although the predetermined value VBC of the battery voltage has been set to a constant value as shown in FIG. 6, since the battery voltage has temperature dependency as shown in FIG. 6, in order to determine the full charge more accurately, this battery voltage determination It is desirable to correct the predetermined value VBC for temperature correction. An example of the temperature correction is shown below.

Now, it is assumed that the temperature characteristic of the charging voltage of the alkaline secondary battery is the characteristic shown in FIG. That is, VB1, V
Points B2 and VB3 have a temperature differential value of 1 ° C./min when rapid charging is started when the battery temperature is 0 ° C., 20 ° C. and 45 ° C., respectively. Also, A, B, C
The battery temperatures near 15 ° C., that is, near full charge are 15 ° C., 35 ° C., and 60 ° C., respectively. A near full charge,
Voltages slightly lower than the voltages of B and C are VBC1 =
1.5V, VBC2 = 1.45V, VBC3 = 1.4V.

FIG. 7 is a table summarizing this relationship. That is, the change amount of the battery voltage per 1 ° C is
2.5 mV / ° C, 35 ° C in the temperature range of 15 ° C to 35 ° C
It is 2.0 mV / ° C in the temperature range of -60 ° C, and these may be used as temperature correction values of VBC per 1 ° C depending on the temperature range.

FIG. 8 shows an example of a concrete procedure for temperature correction of VBC, and the processing of step 116 of FIG. 4 is replaced with the processing of FIG. In FIG. 8, when YES is determined in step 115 of FIG. 4,
First, the current battery temperature TB is read (step 20
1) and then read the battery voltage VB (step 20)
2). In the examples shown in FIGS. 6 and 7, the temperature correction value of VBC differs depending on whether it is 35 ° C. or higher, so after step 202, it is determined in step 203 whether the battery temperature is 35 ° C. or higher.

Here, if YES in step 203, that is, if it is determined that the battery temperature is 35 ° C. or higher, step 20
Go to 4 and calculate n = TB -35 ° C, and
Calculate the temperature correction value of. Now, for example, the battery temperature is TB = 4
When 0 ° C., n = 40 ° C.-35 ° C. = 5 ° C., and the temperature correction value of VBC per 1 ° C. at 40 ° C. is shown in FIG.
Since it is 2.0 mV / ° C, VBC after temperature correction is V
BC = 1.45V-n (0.002) V = 1.45V-5
(0.002) V = 1.44V. Then, in the next step 206, the battery voltage VB ≧ VBC = 1.44V is determined.

On the other hand, if NO in step 203, that is, if the battery temperature TB is determined to be less than 35 ° C., step 20
In step 5, as in step 204, n = TB-35 ° C. is calculated and the temperature correction value of VBC is obtained. Now, for example, if TB = 25 ° C., n = 35 ° C.-25 ° C. = 10
In addition, since the temperature correction value of VBC per 1 ° C. in the case of 25 ° C. is 2.5 mV / ° C. from FIG. 7, VBC after temperature correction is VBC = 1.45V + n (0.0025) V =
1.45V + 10 (0.0025) V = 1.475V. In this case, in step 206, VB ≧ VBC = 1.
The determination of 475V will be performed.

The above processing will be described with reference to FIG. 3. The charging control unit 50 reads the battery temperature obtained by the battery temperature calculation unit 43, executes the processing of steps 203 to 205, and obtains the temperature-corrected VBC. At this time, the temperature differential value determination unit 54 determines that the temperature differential value is equal to or higher than a predetermined value (for example, 1.0 ° C./min) (step 115), so the charge control unit 50 detects the temperature-corrected VBC and the battery voltage. The current battery voltage VB detected by the unit 44 is compared, and the process of step 206 of FIG. 8 is executed.

The processing of FIG. 8 is performed by the microcontroller 20.
This is an example of a case where it is realized by software processing of
Steps 203 to 205 are not performed, and this portion is previously stored in the ROM in the microcontroller 20, that is, the temperature correction ROM 56 in FIG.
It is also possible to store BC in the form of the table in FIG. 77, for example, and refer to this to obtain VBC from the current battery temperature by interpolation. Figure 7 shows three temperatures (15 ℃, 35 ℃, 60 ℃).
Although the temperature correction value in (° C.) is shown, the number of temperatures for which the temperature correction value is taken may be further increased for accuracy.

The process of FIG. 2 in this case will be described. The charge control unit 50 reads the battery voltage calculated by the battery voltage calculation unit 46 and the battery temperature calculated by the battery temperature calculation unit 43 and corresponds to the battery temperature. The temperature correction value information is read from the temperature correction ROM 56 to calculate the temperature-corrected VBC. Then, this VBC is compared with the current battery voltage VB detected by the battery voltage detector 44, and the process of step 206 is executed.

Instead of correcting the temperature of VBC,
VBC is the battery voltage at 35 ° C (constant), and the current battery voltage VB is 35 ° C from the current battery temperature.
The temperature may be corrected to the voltage at that time and the corrected battery voltages VB and VBC may be compared.

Further, in the above embodiment, when the temperature differential value reaches the set value, when the battery voltage is equal to or higher than the predetermined value, the battery voltage at the time of ending the rapid charging is the charging voltage. That is, the battery voltage to be compared with the predetermined value when the temperature differential value reaches the set value is not limited to the battery voltage at the time of charging, but may be, for example, the open voltage (battery voltage when the charging current is cut off) or the discharge voltage (battery voltage). Battery voltage when the battery is being discharged).

Further, in FIG. 4, the temperature differential value is calculated in step 109, and if YES in step 115, the battery voltage ≧ VBC is checked in step 116. On the contrary, the check in step 116 is performed first, and if YES, step In step 109, the temperature differential value is calculated, and in step 115 it is checked whether the battery is fully charged. If YES, step 117
The processing may be performed in a flow that contributes to quick charging at low cost.

In addition, the present invention can be variously modified and implemented without departing from the spirit of the invention.

[0057]

As described above, according to the present invention, the temperature differential value reaches the set value 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. Control to determine whether the battery voltage has reached a predetermined value at the point of time when the battery voltage has reached the predetermined value, to terminate the rapid charge, and to continue the rapid charge if the battery voltage has not reached the predetermined value. By doing so, when the battery pack is brought into the room from a low temperature environment for quick charging, or when the temperature of the battery rises due to flapping heat due to the heat generated by the charger, the fully charged state immediately after the start of charging. There is no shortage of charge due to erroneous determination of a non-full battery as full charge, and it is possible to prevent overcharging due to accidental rapid charging of a fully charged battery.

Further, by correcting the temperature of the predetermined value used for determining the battery voltage or the detected battery voltage itself, it is possible to determine the full charge more accurately without being affected by the change in ambient temperature.

[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 a change over time in the battery voltage, the battery temperature, the set value of the battery voltage, and the charging current at the time of rapid charging for explaining the operation of the embodiment.

FIG. 6 is a diagram showing the voltage rise characteristics of a battery under various battery temperature conditions.

FIG. 7 is a diagram showing a relationship between a battery temperature, a battery voltage set value, and a temperature correction value.

FIG. 8 is a diagram showing a flowchart of processing relating to temperature correction in the embodiment.

[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 Charging transistor 14 ... Trickle charging transistor 16 ... Backflow prevention diode 17 ... Photocoupler 20 ... Microcontroller 30 ... Operational amplifier 31 ... LED 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 ... Quick charge control signal 52 ... Trickle charge control Signal 53 ... Charging start signal 54 ... Temperature differential value determination unit 55 ... Timer value transmission line 5 ... temperature correction for ROM

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Teruo Oda 1-1-1, Showa-cho, Kariya city, Aichi Prefecture Nihondenso Co., Ltd.

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 a quantity, voltage detecting means for detecting the voltage of the secondary battery, and the voltage when the temperature differential value obtained by the temperature differential detecting means reaches a set value. A charging device for a secondary battery, comprising: a charging control unit that terminates the rapid charging when the voltage detected by the detection unit is equal to or higher than a predetermined value. 2. The charging control means corrects the voltage or the predetermined value detected by the voltage detection means according to the temperature detected by the temperature detection means, and uses the corrected voltage or the predetermined value. The secondary battery according to claim 1, further comprising: determining whether or not to terminate the rapid charging when the temperature differential value obtained by the temperature differential detection means reaches a set value. Charging device.