JPH08149708A - Charger for secondary battery - Google Patents

Abstract

PURPOSE: To obtain a charger for a secondary battery in which the cycle life can be prolonged by charging a secondary battery by an appropriate amount corresponding to the reduced battery capacity thereby preventing deterioration of the battery. CONSTITUTION: The charger for a secondary battery comprises a section 41 for deciding whether a secondary battery is set in a charger or not, a timer section 43 for receiving decision results from the section 41 and measuring the length of time when the secondary battery is removed from the charger, a section 44 for determining the charging time of the secondary battery when it is set again in the charger based on the time length measured at the timer section 43, and a section 42 for controlling the charging of the secondary battery over the charging time determined at the section 44.

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 for charging a device such as a mobile phone having a built-in secondary battery when not in use.

[0002]

2. Description of the Related Art Generally, a mobile phone incorporates a pack type secondary battery (called a battery pack) and operates by using this as a power source. When using a mobile phone in a company or other office, it is often the case that the mobile phone is always set in a charger placed in a specific place in a standby state.
When the mobile phone receives an incoming call and the user wants to make a call, the mobile phone is removed from the charger, and after the call ends, it is set again in the charger.

The charger automatically starts charging when the mobile phone is set. In this case, in consideration of the charging efficiency, the charger charges the empty battery with a timer for a period of time corresponding to the amount of charge to fully charge the battery, for example, 130% of the charging capacity (battery capacity). Therefore, when the mobile phone is set in the charger, the battery that is close to full charge even after the call has ended due to the short talk time is overcharged by about 130%. For example, if the average talk time is 3 minutes and the current consumption of the mobile phone during the call is 200 mA, energy of 200 mA × 3 minutes / 60 minutes = 10 mAh is consumed. In this case, for a battery with a capacity of 600 mAh, 10 mAh / 600 mAh × 100% = 1.7%
600mAh x 130 despite being consumed only
A charge amount of% = 780 mAh is charged. Moreover, the mobile phone is removed from the charger for a call each time there is an incoming call, and 130% of the charge is performed every time the mobile phone is reset to the charger after the call ends. If charging is done in this way, if the talk time is relatively long, for example, about 30%
Even if the battery capacity is consumed, 130% of the battery capacity
A charge amount of -30% = 100% results in overcharge.

[0004]

As described above, in a conventional charger for charging a secondary battery built in a device such as a mobile phone, the battery is charged more than the battery capacity each time the device is set. However, the battery is always exposed to the overcharged state, and the deterioration progresses. Therefore, the cycle life of the battery is shortened, and as a result, the battery capacity is reduced in a short period of time.

According to the present invention, when the secondary battery is set, the battery can be charged by an appropriate amount of charge corresponding to the decrease in the battery capacity, thereby preventing the deterioration of the battery and prolonging the cycle life. An object is to provide a battery charging device.

[0006]

In order to solve the above problems, the present invention provides a charging device for charging a secondary battery when the secondary battery is set, in which the secondary battery is set in the charging device. Detecting means for detecting whether the secondary battery is in the state of being detached from the charging device in response to the detection result of this detecting means, and the measuring means. Charging time determining means for determining a charging time when the secondary battery is reset in the charging device based on the determined time length.

Further, the charging time determining means divides the time length measured by the measuring means into a plurality of predetermined unit time areas, and determines using a different weighting coefficient for each unit time area. The charging time is determined by allocating the unit charging time.

[0008]

As described above, according to the present invention, the length of time during which the secondary battery is removed from the charging device is measured, and when the battery is set in the charging device, the battery is charged based on the length of time. The charging time is determined when the device is reset.

In other words, the amount of decrease in battery capacity can be estimated to some extent from the length of time that the battery has been removed from the charging device, so charging is performed so that the amount of charge sufficient to supplement the amount of decrease in battery capacity is obtained. Determine the time, set the timer, and charge only for that time. As a result, the degree of overcharging is mitigated and deterioration of the battery is reduced compared to the conventional method in which a timer charges the battery until the empty battery is fully charged each time the battery is set in the charging device. Is minimized.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit configuration diagram of a charging device for a secondary battery according to an exemplary embodiment of the present invention. An example of a charging device for charging a battery 31 is shown.

In FIG. 1, for example, A from the commercial power source 1
The voltage of C100V is stepped down by the transformer 2, and is made a DC voltage of, for example, DC + 12V by the rectifying bridge 3 formed of a diode and the smoothing capacitor 4. This DC + 12
For example, + 5V DC power supply V from V to regulator 5
dd is created. The capacitor 6 is a smoothing capacitor for Vdd. Vdd is used as a power source for the microcomputer 7.

On the other hand, the DC + 12V power supply terminal is connected to one end of the resistor 9 and the emitter of the PNP transistor 10 via the current limiting resistor 8, and the other end of the resistor 9 and the transistor 10 are connected.
The collector of is connected to the + side power input terminal of the mobile phone 30 via the backflow prevention diode 11. Between the + side power input terminal of the mobile phone 30 and the ground terminal, for example, +
A series circuit of a Zener diode 12 having a Zener voltage of 5V and resistors 13 and 14 is connected. Resistance 1
Reference numerals 3 and 14 are for dividing the terminal voltage of the battery 31 (hereinafter, referred to as battery voltage), and the voltage dividing point is connected to the input port P1 of the microcomputer 7.

The DC + 12V power source terminal is further connected to the base of the transistor 10 and one end of the resistor 17 via diodes 15 and 16 in series, and the other end of the resistor 17 is N.
It is connected to the collector of the PN transistor 18. The emitter of the transistor 18 is connected to the ground terminal. The base of the transistor 18 is connected to one end of the resistor 20 and is also connected to the ground end via the resistor 21. Resistance 2
The other end of 0 is connected to the output port P2 of the microcomputer 7 and also connected to Vdd via the resistor 19. The-side power input terminal of the mobile phone 30 is connected to the ground terminal.

Next, the operation of the charging device shown in FIG. 1 will be described.
The microcomputer 7 sets the output port P2 to the "H" level during normal charging. This turns on the transistor 18 and turns the diode 1 from DC + 12V.
A current flows through the transistors 5, 16, the resistor 17 and the transistor 18, and the base potential of the transistor 10 falls below + 12V, so that the transistor 10 is turned on. Here, when the mobile phone 30 is set in the charging device,
A charging current flows from DC + 12V to the battery 31 via the resistor 8, the transistor 10 and the diode 11. At this time, the resistance value of the current limiting resistor 8 is determined so that the charging current has a specified value, for example, 110 mA.

On the other hand, when the output port P2 of the microcomputer 7 becomes "L" level, the transistor 18 is turned off contrary to the above, and almost no current flows through the diodes 15 and 16 and the resistor 17, so that the transistor 10 has its base. It turns off when the potential becomes approximately + 12V. Therefore, a minute current, for example, 12 mA flows from the DC + 12V into the mobile phone 30 through the resistor 8, the resistor 9, and the diode 11. At this time, since the mobile phone is set in the charging device and is in a standby state, 2 mA flows to the battery 31 and 10 mA flows to the load 32, respectively.

Here, when the mobile phone 30 (battery 31) is not set in the charging device, that is, when the battery 31 is not connected to the charging device, the current passing through the diode 11 is applied to the resistors 13 and 14. It flows in, but resistance 1
If the values of 3 and 14 are set sufficiently large, the diode 11
About + 12V appears on the cathode side of. Where resistance 1
Since the Zener diode 12 is inserted between 3 and the cathode of the diode 11, 12V-5V = 7V is applied to both ends of the series circuit of the resistors 13 and 14. In this case, if the resistors 13 and 14 have the same value, the resistor 1
The divided voltage value by 3, 14 is 3.5V, which is given to the input port P1 of the microcomputer 7 as an "H" level signal.

Further, the charging device includes a mobile phone 30 (battery 3
When 1) is set, that is, when the battery 31 is connected to the charging device, the battery voltage is 4.2 V or less.
No voltage appears across the series circuit of 4. Therefore, the input port P1 of the microcomputer 7 becomes "L" level. In this way, the microcomputer 7 can determine whether or not the battery 31 is set from the level state of the input port P1.

FIG. 2 is a block diagram showing the functional structure of the portion of the microcomputer 7 related to the present invention.
The microcomputer 7 includes a battery set detection unit 4
1, charging control unit 42, timer unit 43, charging time determination unit 4
4 and a charging current on / off control unit 45. The battery set detection unit 41 detects whether the battery 31 is set in the charging device or removed from the level state of the input port P1, and the detection result is given to the charging control unit 42. When the battery 31 is set in the charging device, the charging control unit 42 receives a signal indicating that from the battery set detection unit 41 and activates the first timer of the timer unit 43, and the battery 31 is removed from the charging device. Then, the second timer of the timer unit 43 is started upon receiving a signal indicating that from the battery set detection unit 41. The first timer is for measuring whether or not the time corresponding to the set timer value has elapsed when the battery 31 was set, and the second timer is the length of time during which the battery 31 is removed. ,
That is, it is for measuring the time length from the removal of the battery 31 to the resetting. The charging time calculation unit 44 calculates and determines the charging time when the battery 31 is reset in the charging device, based on the time length measured by the second timer. The charging control unit 42 outputs a charging current on / off control signal to the output port P2 based on the outputs from the battery set detection unit 41, the timer unit 43, and the charging time determination unit 44.

Next, the operation of this embodiment will be described with reference to the flow chart shown in FIG. The battery set detection unit 41 detects whether or not the battery 31 is set in the charging device (step S11). When it is detected that the battery 31 is set, the charging control unit 42 sets 100% charging as a target. A charging timer value corresponding to a charging amount of 133% is set in consideration of charging efficiency (step S12), and the timer unit 4
The first timer of No. 3 is started (step S13).
When the first timer is started, the charging current on / off control signal output from the charging control unit 42 to the output port P2 becomes "H" level, and charging is started (step S1).
4). That is, when the charge current on / off control signal becomes “H” level, the transistor 18 is turned on and the transistor 10 is also turned on. Therefore, the normal charge current is supplied to the battery 31 from the DC + 12V power source end through the resistor 8, the transistor 10 and the diode 11. (For example, 110 mA) flows.

When the first timer of the timer section 43 times out (step S15), the charging current on / off control signal output from the charging control section 42 to the output port P2 becomes "L" level and the charging is completed (step S1).
6). That is, when the charge current on / off control signal becomes “L” level, the transistor 18 is turned off and the transistor 10 is also turned off.
Only a very small current (for example, 12 mA) flows in 1 as compared with the normal charging current.

By the way, during charging in step S14,
The battery set detection unit 41 always detects whether or not the battery 31 is removed from the charging device (step S18). When it is detected that the battery 31 is removed, the charging control unit 42 causes the timer unit 43 to operate. Second timer is started and the time length T1 in the state where the battery 31 shown in FIG. 4A is removed is measured (step S1).
9). That is, when it is detected in step S18 that the battery is removed, the battery set detection unit 41 detects the battery 31.
It is detected whether or not the battery is reset in the charging device (step S20), and if the battery 31 is not reset, the measurement in step S19 is continuously performed.

When the battery 31 is reset, the charging time determining unit 44 calculates the charging time T2 of the battery 31 shown in FIG. 4 (b) based on the time length measured in step S19 at that time. (Step S21). Then, based on the calculated charging time, the timer unit 43
The charge timer value of the first timer is reset (step S
22) and then the process returns to step S13.

As described above, in this embodiment, the length of time during which the battery 31 is removed from the charging device (see FIG. 4).
While the battery 31 is removed from the charging device, the charging time (T2 in FIG. 4B) when the battery 31 is reset in the charging device is determined based on T1) in (a). By determining the charging time T2 so that a charging amount sufficient to supplement the decrease in battery capacity can be obtained, the degree of overcharging can be mitigated.
It is possible to minimize the deterioration of 1.

Next, a specific example of a method of determining the charging time T2 at the time of resetting in the charging time determining unit 44 from the time length T1 in which the battery 31 is removed from the charging device will be described. . Table 1 shows the relationship between the time length T1 and the charging time T2. The current consumption of the mobile phone 30 (current consumption of the load 32) is 200 mA during a call,
The standby condition is 10 mA, and the charging condition is normal charging current I1 =
It is assumed that the current I2 after normal charging is 110 mA, 12 mA, and the normal charging time is 8 hours. The battery 31 is 600
It is assumed that three mAh unit batteries are connected in series.

[0025]

[Table 1]

As shown in Table 1, the charging time T2 is not determined in proportion to the time length T1. That is, in the range where the time length T1 is relatively short such as T1a = 0 to 60 minutes, the charging time T2 is T2a as shown in T2a based on the assumption that a call is made over the entire period.
It is calculated as 1a multiplied by the current consumption (200mA) / normal charging current (110mA) during a call, and then multiplied by the charging efficiency (1.2 in this case).

When the time length T1 is in the range of T1b = 60 to 120 minutes, the charging time T2 is obtained in the same manner as T2a for the first 60 minutes (0 to 60 minutes) time region as shown in T2b. In the remaining 60 to 120 minutes, the call is made over half the period, and in the other period, the call is in the standby state (the current consumption in this standby state is as small as 10 mA, and the call time is estimated a lot). Since the value is set to a value, the current consumption during the standby period is neglected in the calculation here.) Based on the assumption that the current consumption during the waiting period was T1b-60, the current consumption during the call (200 m
A) / normal charging current (110 mA) is multiplied by a weighting factor of 1/2 to obtain the time. That is,
The charging time T2 = T2b in this case is T2b = T2a + (T1b
-60) Calculated as 200 / (110 x 2).

The time length T1 is T1c = 120 to 480.
In the range of minutes, the charging time T2 is as shown by T2c,
The first 120 minutes (0 to 120 minutes) time domain is obtained in the same manner as T2b, the remaining 120 to 480 minutes time domain is used for 1/3 of the call, and the other periods are in standby. Based on the assumption that it was in the state, the current consumption (2
00 mA) / normal charging current (110 mA) and multiplied by a weighting factor of 1/3. That is, the charging time T2 = T2c in this case is T2c = T2b +
It is calculated as (T1b-120) 200 / (110 × 3).

Further, in the range where the time length T1 is T1d = 480 minutes or more, the charging time T2 is set in order to charge 133%.
Is uniformly set to T2d = 480 minutes. In addition, Table 1 also shows the value of the discharge capacity D estimated with respect to the time length T1. That is, Da, Db, Dc, Dd are the discharge capacities corresponding to the time lengths T1a, T1b, T1c, T1d, respectively, and the above-mentioned T2a, T2b, T2c, T2d are the discharge capacities Da, Db, Dc. , Dd is the charging time.

As described above, in this embodiment, the time length T1 during which the battery 21 is removed is set to a plurality of unit time regions, that is, 0 to 60 minutes, 60 to 120 minutes, and 120 to 480 minutes.
The time length T is obtained by dividing the unit time region into one unit time region and allocating the unit charging time determined by using different weighting factors (1, 1/2, 1/3) for each unit time region.
The charging time corresponding to 1 is determined.

The charging time determining unit 44 in FIG. 2 has a time length T1 (T1a, T1a, measured by the second timer of the timer unit 43).
The charging time T2 (T2a, T2b, T2c, T2 is calculated by performing the calculation shown in Table 1 based on T1b, T1c, T1d).
d) is decided and it is given to the charging control unit 42.

FIG. 5 is a diagram showing the relationship between the time pattern of setting / removing the battery 31 with respect to the charging device and the charging time when the battery 31 is reset. This shows an example in which the battery 31 is intermittently removed after the time T6, T7 by the time length T3, T4, T5.

First, since the battery 31 had been removed for the time length T3, it should be charged only for the time T9.
After the time T6 (T6 <T9), the battery 31 was removed again for the time length T4. Therefore, the charging is postponed for the time T9-T6, and the charging is restarted at the end of T4. Then, when the time T10 has elapsed, the time T9 corresponding to the time length of T3 when the battery 31 is removed for the first time
The charging for the time is completed.

The charging time corresponding to the time length of T4 when the battery 31 is removed for the second time is originally T11,
Since there is a time length of T5 when the battery 31 is removed for the third time on the way, as a result, the charging corresponding to T4 is performed for the time of T12-T5 equal to T11.

Similarly, the charging time corresponding to the time length of T5 is originally T13, but the charging time corresponding to T4 is T1.
Since it is performed in the latter half of 2, the charging corresponding to T5 is performed by additionally performing the charging for the time of T14 after the end of T12.

Here, the time length T when the battery 31 is removed
Charging time T9, T1 corresponding to 3, T4, T5
1, T13 is T3, T according to the calculation formula shown in Table 1.
4, T5 is calculated according to which of T1a, T1b, T1c and T1d belongs.

The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the charging time T2 when the battery is removed from the charging device and then set in the charging device is calculated based on the time length T1 when the battery is removed from the charging device according to the calculation formula shown in Table 1. However, this calculation formula is merely an example, and the charging time can be determined using another calculation formula. Further, instead of calculating the charging time T2 from the time length T1 each time, for example, the data of the charging time T2 corresponding to the time length T1 is stored in the ROM, and the data of the charging time T2 is read from this ROM. May be. In that case, it is difficult to obtain and store the charging time T2 corresponding to all the time lengths T1 in advance due to the limitation of the ROM capacity.
The data of the charging time T2 corresponding to 1 may be stored in the ROM, and the charging time T2 corresponding to the actual time length T1 may be obtained by interpolation.

[0038]

As described above, according to the present invention, the charging time when the battery is reset in the charging device is determined according to the length of time that the battery is removed from the charging device. Compared to the conventional method in which an empty battery is fully charged each time the battery is set in the charging device, the battery is not overcharged more than necessary and It is possible to minimize deterioration of the battery due to charging.

[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 block diagram showing a functional configuration of a portion of the microcomputer shown in FIG. 1 related to the present invention.

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

FIG. 4 is a diagram showing a relationship between a charging / discharging state of a battery with respect to a charging device and a charging time and a charging current at the time of resetting in the same embodiment.

FIG. 5 is a diagram showing a relationship between a time pattern of setting / removing a battery with respect to the charging device and a charging time at the time of resetting the battery in the same embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Commercial power supply 2 ... Transformer 3 ... Rectifying bridge 4 ... Smoothing capacitor 5 ... Regulator 6 ... Smoothing capacitor 7 ... Microcomputer 8 ... Current limiting resistor 9, 13, 14, 17, 19-21 ... Resistor 10, 18
... Transistor 11 ... Backflow prevention diode 12 ... Zener diode 30 ... Mobile phone 31 ... Secondary battery 32 ... Load 41 ... Battery set detection unit 42 ... Charge control unit 43 ... Timer unit 44 ... Charge time determination unit 45 ... Charge current on / off Control unit

Claims (2)

[Claims] 1. A charging device for charging a secondary battery when the secondary battery is set, wherein a detecting means for detecting whether the secondary battery is set or removed from the charging device, Measuring means for measuring the length of time that the secondary battery is in a state of being detached from the charging device in response to the detection result of the detecting means, and the secondary battery based on the length of time measured by the measuring means. And a charging time determining means for determining a charging time when the battery is reset in the charging device. 2. The charging time determining means divides the time length measured by the measuring means into a plurality of predetermined unit time areas, and is determined by using a different weighting coefficient for each unit time area. The charging time is determined by assigning different unit charging times.
The rechargeable battery charging device according to.