JP2002075463A - Charge control device of secondary cell, and charging method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the life of a secondary cell by reducing charging frequency. SOLUTION: When it is detected that a portable device 11 is connected to a charging device 12, a CPU 18 reads the digital data indicating an output voltage of a battery 13 from an AD converter 16, and judges whether the output voltage is lower than the prescribed voltage or not. When the output voltage of the battery 13 is lower than the prescribed voltage, a switch 15 is turned on and charging of the battery 13 is started. On the other hand, when the output voltage is higher than the prescribed voltage, the switch 15 is kept in the state of turned off, and charging is not carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery charging control device and a secondary battery charging method.

[0002]

2. Description of the Related Art Portable devices such as portable telephones and portable personal computers use a battery or a rechargeable secondary battery as a power source. Since the capacity of the secondary battery is reduced by using the device, the device driven by the secondary battery needs to be connected to the charging device and charged.

[0003]

A secondary battery such as a lithium ion battery or a nickel cadmium battery is required to reduce the number of times of charging since the charging capacity is reduced by repeating charging and the life of the battery is shortened.

[0004] However, a portable device or the like having a built-in secondary battery connected to a charging device for charging is charged automatically when the device is connected to the charging device. There is a problem that the number of times of charging is increased and the life of the secondary battery is shortened.

An object of the present invention is to extend the life of a secondary battery by reducing the number of times of charging.

[0006]

According to a first aspect of the present invention, there is provided a charge control apparatus for a secondary battery, comprising: a voltage detecting means for detecting a voltage of the secondary battery; and a voltage of the secondary battery detected by the voltage detecting means. When the voltage becomes equal to or less than a predetermined charging start voltage, the voltage is supplied from the charging device to the secondary battery, and when the voltage of the secondary battery is higher than the charging starting voltage, the voltage is not supplied from the charging device to the secondary battery. Switch means for controlling the

According to the present invention, charging is performed only when the voltage of the secondary battery becomes equal to or lower than a predetermined charging start voltage, and charging is not performed at other times. The life of the secondary battery can be extended.

According to a second aspect of the present invention, there is provided a charging control apparatus for a secondary battery, comprising: a calculating means for calculating a remaining capacity of the secondary battery; and when the remaining capacity calculated by the calculating means becomes a predetermined value or less. Charging control means for starting charging of the secondary battery and prohibiting charging of the secondary battery when the remaining capacity exceeds a predetermined value.

According to the present invention, charging is performed only when the remaining capacity of the secondary battery is equal to or less than a predetermined value, and charging is not performed at other times. The life of the secondary battery can be extended.

[0010] In the above invention, the calculating means may calculate the remaining capacity of the secondary battery from a temporal change in the voltage of the secondary battery when a constant current flows. With this configuration, for example, the remaining capacity can be calculated more accurately from the temporal change in the voltage of the secondary battery when a constant load is connected to a pseudo load to the secondary battery. .

According to a fourth aspect of the present invention, there is provided a charging control apparatus for a secondary battery, comprising: measuring means for measuring a charging current supplied from the charging apparatus to the secondary battery and a discharging current supplied from the secondary battery to a load. Storage means for storing the cumulative value of the charging current and the cumulative value of the discharging current measured by the measuring means; and the storage of the secondary battery based on the cumulative value of the charging current and the cumulative value of the discharging current stored in the storing means. Calculating means for calculating the remaining capacity; charging the secondary battery when the remaining capacity of the secondary battery calculated by the calculating means is equal to or less than a predetermined value; Charging control means for prohibiting charging of the battery.

According to the present invention, since charging is performed according to the remaining capacity of the secondary battery, the number of times of charging can be reduced and the life of the secondary battery can be extended. In addition, since the remaining capacity of the secondary battery is calculated from the cumulative value of the charging current of the secondary battery and the cumulative value of the discharging current supplied to the load by the secondary battery, the remaining capacity of the secondary battery is accurately calculated. Then, charging can be performed at an appropriate time.

According to a sixth aspect of the present invention, there is provided a secondary battery charge control device, wherein first storage means for storing a charge start voltage corresponding to a predetermined number of times of use or a use time; Or counting means for counting the usage time, second storage means for storing the number of times of charging of the secondary battery or the cumulative value of the usage time counted by the counting means, and voltage detection means for detecting the voltage of the secondary battery. Acquiring from the first storage means a charging start voltage corresponding to the number of times of charging of the secondary battery or the cumulative value of the usage time stored in the second storage means,
When the voltage of the secondary battery detected by the voltage detection means has become equal to or less than the charging start voltage, charging of the secondary battery is started,
Charge control means for prohibiting the charging of the secondary battery when the voltage of the secondary battery exceeds the charging start voltage.

According to the present invention, since the charging is performed based on the charging start voltage stored in advance corresponding to the number of times of charging or the usage time of the secondary battery, it is possible to perform charging at an appropriate voltage or timing. Thus, the number of times of charging can be reduced, and the life of the secondary battery can be extended.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit configuration diagram of the charge control device according to the first embodiment of the present invention. This embodiment is directed to a mobile device 1 such as a mobile phone or a handy terminal.
1 is provided with a charge control device for controlling charging of a secondary battery (battery). As the battery 13 of the portable device 11, a lithium ion battery, a nickel cadmium battery, or the like can be used.

The portable device 11 has two charging terminals 14 connected to a charging device 12 for charging the battery 13.
a and 14b are provided. A switch 15 is connected between the positive power supply terminal 13a of the battery 13 and the positive charging terminal 14a. The switch 15 is connected to a C
It is a semiconductor switch or the like that is turned on and off by the PU 18.

The power supply terminal 13 on the positive side of the battery 13
A switch 17 composed of a semiconductor switch or the like is provided between a and the input terminal of the AD converter 16. The switch 17 is turned on and off by the CPU 18. The negative power supply terminal 13b of the battery 13 is a charging terminal 1
4b.

The A / D converter 16 has at least three A / D conversion circuits for converting an analog signal into digital data, and has three input and output terminals corresponding thereto.

The first input terminal 16a is a charging terminal 14a
The second input terminal 16b is connected to the positive power supply terminal 13a of the battery 13 via the switch 17 described above, and the third input terminal 16c is directly connected to the positive power supply terminal 13a of the battery 13 Have been.

The three input terminals 16 of the AD converter 16
The analog signals input from a to 16c are respectively converted into digital data by an internal AD conversion circuit, and output to the CPU 18 from three output terminals 16d, 16e and 16f.

As shown in FIG. 1, the output side of the switch 17 (the output side when the side connected to the battery 13 is the input side) and the input terminal 16b of the AD converter 16
The pseudo load 19 is connected to the connection point 23 of the pseudo-load 19.

This is because the remaining capacity of the battery 13 is calculated by detecting a change in the output voltage of the battery 13 when the switch 17 is turned on and a constant current flows through the dummy load 19 by the AD converter 16. is there. In FIG. 1, the pseudo load 19 is shown surrounded by a broken line because it is not necessary to perform both the detection of the output voltage of the battery 13 and the calculation of the remaining capacity using the pseudo load 19.

The CPU 18 reads the digital data output from the AD converter 16, and outputs the output voltage of the charging device 12, the output voltage of the battery 13, or the pseudo load 1
A change in the voltage of the battery 13 when a constant current flows through 9 is detected.

The power terminal 13a of the battery 13 and DCDC
The switch 21 is connected to the converter 20. This switch 21 is composed of a semiconductor switch, etc.
On / off control is performed by the PU 18.

Charging terminal 14a and DCDC converter 20
Is connected to the switch 22. The switch 22 is also formed of a semiconductor switch or the like, and is turned on and off by the CPU 18.

Next, the operation of the charging control device having the above configuration will be described. The CPU 18 reads the digital data output from the output terminal 16 d of the AD converter 16 and, when detecting that the portable device 11 is connected to the charging device 12, outputs the output of the battery 13 output from the output terminal 16 f of the AD converter 16. The digital data indicating the voltage is read, and it is determined whether or not the output voltage of the battery 13 is equal to or lower than a predetermined value.

When the output voltage of the battery 13 is lower than a predetermined value, the CPU 18 turns on the switch 15 to start charging the battery 13. While the battery 13 is being charged, the switch 22 is turned on and the switch 21 is set to the off state, power is supplied from the charging device 12 to the internal circuit via the DCDC converter 20, and power is not supplied from the battery 13. To do. Then, when the output voltage of the battery 13 reaches the rated voltage, the switch 15 is turned off to terminate charging.

On the other hand, when the output voltage of the battery 13 is higher than the predetermined value, the switches 15 and 21 are turned off and the switch 22 is turned on, and charging is not performed. Simulated load 19
When calculating the remaining capacity of the battery 13 using
The PU 18 turns on the switch 17 to flow a constant current from the battery 13 to the dummy load 19. Then, the amount of voltage drop of the battery 13 when a constant current flows is measured, and based on the measured voltage drop amount and data indicating the relationship between the remaining capacity of the battery 13 and the voltage drop amount stored in advance in a ROM or the like. To estimate the remaining capacity of the battery 13.

When the remaining capacity of the battery 13 is less than the predetermined value, the switch 15 is turned on to start charging the battery 13. When the remaining capacity of the battery 13 exceeds a predetermined value, charging is not performed.

The charging of the battery 13 by the charging control device may be performed only in a specific time zone. For example, if the charging time is set from 21:00 to 7:00 the next morning as charging is permitted and charging is prohibited in other time periods, the mobile device 11 connects to the charging device 12 before 21:00. CPU 18 switches switches 15 and 2
1 is turned off, and the switch 22 is turned on. When the switch 15 is off, the portable device 11
Even when the battery 13 is connected, no current flows from the charging device 12 to the battery 13, so that the battery 13 is not charged.

With the portable device 11 connected to the charging device 12, the time measured by the CPU 18 has passed 21:00,
When the voltage of the battery 13 is detected to be equal to or lower than the predetermined value as described above,
The switches 5 and 22 are turned on and the switch 21 is turned off to start charging.

When the charge capacity of the battery 13 decreases depending on the number of times of charging, a suitable charging start voltage corresponding to the number of times of charging is obtained, and data that associates the number of times of charging with the charging start voltage is obtained. May be stored in a ROM or the like in advance.

The CPU 18 counts the number of times the battery 13 has been charged and stores the accumulated value.
The output voltage of the battery 13 detected in 6 is compared with a charging start voltage determined by the cumulative value of the number of times of charging, and when the output voltage of the battery 13 becomes equal to or lower than the charging start voltage, charging is started.

With this configuration, an appropriate charging start voltage can be set according to the number of times of charging.
3 can be performed at an appropriate time to reduce the number of times the battery 13 is charged, thereby extending the life of the battery 13.

Further, in the charge control device of FIG. 1, the cumulative value of the use time (discharge time) when power is supplied from the battery 13 to the internal circuit of the portable device 11 is measured, and when the cumulative value of the use time is equal to or more than a predetermined value. Then, the switch 15 may be turned on to charge the battery 13.

With this configuration, the portable device 11
Even when the battery is connected to the charging device 12, it is possible to determine whether or not to perform charging in accordance with the usage time of the battery 13, so that the number of times of charging the battery 13 can be reduced and the life can be extended.

According to the above-described first embodiment, when the voltage of the battery 13 falls below a predetermined value, when the voltage falls below a charging start voltage determined by the number of times of charging, or when the battery 13 is used, charging is performed. Since charging is not performed at other times, the number of times of charging can be reduced and the life of the battery 13 can be extended.

Further, by controlling the charging so as to be performed only during the time when the portable device 11 is not used, the charging is interrupted in the middle to use the portable device 11, and as a result, the number of times of charging is increased. Avoid problems.

Next, a second embodiment of the present invention in which the remaining capacity of the battery 13 is calculated from the charge current and the consumed current (discharge current) of the battery 13 to control the charge will be described with reference to FIG. .

A switch 32 is connected between the charging terminal 14 a of the charging device 12 and the current monitoring unit 31. The positive power supply terminal of the battery 13 is connected to the current monitoring unit 31. Battery 1 monitored by current monitor 31
Data indicating the charge current and the discharge current of No. 3 is output to the CPU 35.

A switch 34 is connected between the output terminal of the current monitoring unit 31 and the DCDC converter 33.
Further, a switch 37 is connected between a connection point 36 between the switch 34 and the DCDC converter 33 and the charging terminal 14a.

An A / D converter 38 is connected to the power supply terminal 14a.
The digital data is converted into digital data by 8 and output to the CPU 35.

Next, the operation of the charging control device having the above configuration will be described. The current monitoring unit 31 measures a charging current and a charging time every time charging is performed, and outputs the measurement result to the CPU 35.
Output to The CPU 35 calculates the charging capacity from the charging current and the charging time, and stores the calculation result in a memory or the like.

When power is supplied from the battery 13 to the internal circuit after charging is completed, the current monitoring unit 31 measures the discharge current and the discharge time of the battery 13 and reports the measurement result to the CP.
Output to U35. The CPU 35 stores the discharge current and the discharge time in a memory or the like, and calculates the capacity consumed by the discharge from the values. Then, the remaining capacity of the battery 13 is calculated by subtracting the discharging capacity from the charging capacity, and stored in a memory or the like.

The portable device 11 is used for charging
Is connected, the CPU 35 determines whether or not the remaining capacity of the battery 13 stored in the memory or the like is equal to or less than a predetermined value. When the remaining capacity of the battery 13 is equal to or less than the predetermined value, the switch 32 is turned on and the output voltage of the charging device 12 is applied to the battery 13 to charge the battery 13. Further, the switch 37 is turned on so that the output voltage of the charging device 12 is supplied to the DCDC converter 33. At this time, the switch 34 is turned off, and the output voltage of the battery 13 becomes DCD.
It is not supplied to the C converter 33.

When the CPU 35 determines that the remaining capacity of the battery 13 is larger than the predetermined value, the switch 3
2 and 34 are turned off, and the switch 37 is turned on to prevent charging.

Also in the second embodiment, charging may be prohibited depending on the time zone. If the time measured by the CPU 35 is a time period in which charging is prohibited, the switches 32 and 34 are turned off and the switch 37 is turned on to charge the battery 13 even if the remaining capacity of the battery 13 is less than or equal to a predetermined value. Is not performed.

On the other hand, when the time measured by the CPU 35 is a time zone in which charging is permitted and the remaining capacity of the battery 13 is equal to or less than a predetermined value, the switches 32 and 37 are turned on, and the switch 34 is turned off to turn off the battery. 13 is charged.

According to the second embodiment described above, charging is performed when the remaining capacity of the battery 13 is equal to or less than a predetermined value, and charging is not performed when the remaining capacity exceeds the predetermined value. And the life of the battery 13 can be extended.

In the embodiment described above, the switches 15 and
Although 17 and the like are constituted by semiconductor switches and the like, the invention is not limited thereto, and switches having mechanical contacts, electromagnetic relays, and the like may be used.

In the above-described embodiment, the charging control device is provided in the portable device 11, but the charging control device may be provided in the charging device 12. In this case, only circuits that cannot be measured on the portable device 11 side, such as the usage time of the battery 13 and the discharge current, are provided in the portable device 11, and data is transmitted and received between the portable device 11 and the charging device 12 in a contact or non-contact manner. You may do it.

[0052]

According to the present invention, the number of times of charging the secondary battery can be reduced, and the life of the secondary battery can be extended. For example, the remaining capacity is calculated from a voltage change when a constant current is applied to the secondary battery, and the secondary battery is charged only when the remaining capacity becomes a predetermined value or less, thereby reducing the number of times of charging the secondary battery. In addition, the life of the secondary battery can be extended. In addition, the remaining capacity can be obtained more accurately by measuring the charge capacity and the discharge capacity of the secondary battery and calculating the remaining capacity. Thereby, charging can be performed at an appropriate time, so that the number of times of charging can be reduced and the life of the secondary battery can be extended.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a charge control device according to a first embodiment.

FIG. 2 is a circuit configuration diagram of a charge control device according to a second embodiment.

[Explanation of symbols]

 13 Battery 15, 17, 21 Switch 16, 38 AD converter 18, 35 CPU

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kenji Yamafuji 1776 Yanoguchi, Inagi-shi, Tokyo Inside Fujitsu Kiden Co., Ltd. (72) Inventor Takefumi Mame 1776 Yanoguchi, Inagi-shi, Tokyo 5G003 AA01 BA01 CA11 CC02 EA05 GC05 5H030 AS18 BB01 BB21 BB26 FF42 FF43 FF44

Claims (7)

[Claims] 1. A voltage detecting means for detecting a voltage of a secondary battery, and when the voltage of the secondary battery detected by the voltage detecting means falls below a predetermined charging start voltage, the charging device detects the voltage of the secondary battery. Switch means for controlling the supply of a voltage from the charging device to the secondary battery when the voltage of the secondary battery is higher than the charging start voltage. Control device. Calculating means for calculating the remaining capacity of the secondary battery; charging the secondary battery when the remaining capacity calculated by the calculating means is equal to or less than a predetermined value; Charging control means for prohibiting the charging of the secondary battery when the charging time exceeds the threshold value. 3. The rechargeable battery according to claim 2, wherein said calculating means obtains a remaining capacity of the rechargeable battery from a temporal change of a voltage of the rechargeable battery when a constant current flows. Control device. And measuring means for measuring a charging current supplied to the secondary battery from the charging device and a discharging current supplied to the load from the secondary battery; and a cumulative value of the discharging current measured by the measuring means and charging. Storage means for storing the accumulated value of the current; calculating means for calculating the remaining capacity of the secondary battery based on the accumulated value of the charging current and the accumulated value of the discharging current stored in the storing means; Charge control means for starting charging of the secondary battery when the remaining capacity of the secondary battery calculated by the method is equal to or less than a predetermined value, and prohibiting charging of the secondary battery when the remaining capacity exceeds the predetermined value. A charge control device for a secondary battery, comprising: 5. A switch device for supplying current from the charging device to the load and stopping supply of current from the secondary battery to the load when the charging device is charging the secondary battery. The charging control device for a secondary battery according to claim 2, 3 or 4. 6. A first storage means for storing a charging start voltage corresponding to a predetermined number of times of charging or a use time; a counting means for counting the number of times of charging or a use time of a secondary battery; A second storage unit for storing the counted number of times of charging the secondary battery or a cumulative value of the usage time; a voltage detection unit for detecting a voltage of the secondary battery; A charging start voltage corresponding to the number of times of charging of the secondary battery or a cumulative value of the usage time is obtained from the first storage unit, and the voltage of the secondary battery detected by the voltage detecting unit is equal to or lower than the charging start voltage. A charging control unit for starting charging of the secondary battery and prohibiting charging when the voltage of the secondary battery exceeds the charging start voltage. 7. When the voltage of the secondary battery is detected, and when the detected voltage of the secondary battery becomes equal to or lower than a predetermined charging start voltage, the output voltage of the charging device is supplied to the secondary battery. When the battery voltage exceeds the charging start voltage,
A method for charging a secondary battery, wherein the output voltage of the charging device is controlled so as not to be supplied to the secondary battery.