JP2707163B2 - Rechargeable battery charger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic apparatus, and more particularly, to an apparatus for charging a secondary battery such as a nickel / cadmium (nickel) battery which is incorporated in an AC (alternating current) adapter.

FIG. 3 is a system block diagram of a conventional AC adapter having a function as a charging device for a NiCd battery. Referring to FIG. 3, a conventional AC adapter 1
a converts an alternating current supplied from an external power supply through the AC plug 3 and the fuse 4 into a constant voltage direct current (DC), and converts the alternating current into a DC output terminal 29; A switching regulator circuit 5 that operates as an AC / DC converter for supplying the battery terminal 9 as a terminal; a DC output switch 12 and a diode 13 provided between the switching regulator circuit 5 and the DC output terminal 29; It includes a quick charge switch circuit 6, a constant current correction resistor 7, and a diode 8 connected in series between the switching regulator circuit 5 and the battery terminal 9. A trickle charge switch 10 and a trickle charge limiting resistor 11 are connected between the switching regulator circuit 5 and the diode 8 in parallel with the quick charge switch circuit 6 and the constant current correction resistor 7. The functions of the quick charge switch circuit 6, trickle charge switch circuit 10, and DC output switch 12 will be described later.

The quick charge switch circuit 6, trickle charge switch circuit 10, and DC output switch 12 are controlled by a microcomputer (microcomputer) 20. A connection line from the switching regulator circuit 5 to the DC output switch 12 branches on the way and is connected to a switching regulator circuit 24 that operates as a DC / DC converter. Switching regulator circuit 24
Is 1 output from the switching regulator circuit 5.
This is for converting a constant voltage of 5 to 6 V into a DC voltage of about 5 V. The switching regulator circuit 24 has a charging LED for indicating that it is in a charged state.
(Light Emitting Diode) 27 and a switch 28 connected between the charging LED 27 and the ground potential and controlled by the microcomputer 20 are connected.

The AC adapter 1 a further has an input connected to the battery terminal 9, detects that the battery 2 is mounted on the battery terminal 9, and transmits the input to the microcomputer 20. A charge completion detection circuit 15 connected to the battery terminal 9 for detecting that the charging of the battery 2 has been completed and transmitting it to the microcomputer 20 is provided. Both the battery mounting detection circuit 14 and the charging completion detection circuit 15 operate by receiving power supply from the switching regulator circuit 24.

The microcomputer 20 further includes a timer 19 provided to prevent damage to the battery 2 due to full charge when the charge completion detection circuit 15 cannot detect the completion of charging of the battery 2 for some reason. ,
When the output of the battery mounting detection circuit 14 becomes unstable due to rattling (chattering) or mischief when the battery 2 is mounted on the battery terminal 9, the operation mode of the AC adapter 1a becomes unstable. There is provided a memory circuit 23 for preventing such a situation from occurring, and a power switch 22 connected to the microcomputer 20.

The microcomputer 20 includes a battery mounting detection circuit 14
And in response to the output of the charge completion detection circuit 15, when the battery 2 is not mounted on the battery terminal 9,
An AC adapter mode for performing DC output to the output terminal 29, a charging mode for charging the battery 2 when the battery 2 is mounted on the battery terminal 9, and further detecting that the charging of the battery 2 has been completed. And a trickle charge mode in which a small amount of current is supplied to the battery 2 to cover the self-discharge of the battery and to fully charge (fully charge) the battery 2 in accordance with the selected mode. Switch 6, 1
0 and 12 are controlled.

Referring to FIG. 3, A including a conventional charging device
The C adapter operates as follows.

AC Adapter Mode When DC power is supplied to a portable device or the like, the following connection is made. The AC plug 3 is connected to an outlet of a commercial AC power supply. The portable device is connected to the DC output terminal 29 by a DC cable or the like.

The AC adapter mode is selected when the battery 2 is not mounted on the battery terminal 9. Whether or not the battery 2 is mounted on the battery terminal 9 is detected by the battery mounting detection circuit 14.

When the battery 2 is not mounted on the battery terminal 9, the microcomputer 20 turns on the DC output switch 12 and the quick charge switch circuit 6, and turns off the trickle charge switch 10. The switching regulator circuit 5 converts the AC voltage supplied from the AC plug 3 into a constant DC constant voltage B2,
Give to 2. This constant voltage turns on the DC output switch 12.
Therefore, it is supplied to a portable device or the like via the diode 13 and the DC output terminal 29. Since the quick charge switch circuit 6 is ON, the battery 2 is connected to the battery terminal 9.
Can be easily detected by the battery mounting detection circuit 14.

Charge Mode In the following description, a battery that requires constant current charging, such as a nickel-cadmium (NiCd) battery, to which the present invention is particularly concerned, will be described. The battery attachment detection circuit 14 detects that the battery 2 has been attached to the battery terminal 9, and sends the information to the microcomputer 20. Microcomputer 2
0 turns off the DC output switch 12 in response to the output of the battery attachment detection circuit 14. The quick charge switch circuit 6 is kept ON, and the trickle charge switch 10 is kept OFF.

The switching regulator circuit 5 converts an AC voltage supplied from the plug 3 into a DC constant current of a voltage B1 and supplies the DC constant current to the quick charge switch circuit 6. The magnitude of the constant current is determined by the rapid charging switch circuit 6 and the diode 8
, And the internal impedance of the battery 2 and the resistance value r1 of the constant current correction resistor 7. The charging current is supplied from the switching regulator circuit 5 to the battery 2 via the rapid charging switch circuit 6, the constant current correcting resistor 7, the diode 8, and the battery terminal 9.
Then, the battery 2 is charged by this current.

In the charging mode, the microcomputer 20 turns on the switch 28. The switching regulator circuit 24 converts the voltage of 15 to 6 V output from the switch regulator circuit 5 to 5 to 6 V to charge the LED 27.
Has given to. When the switch 28 is turned on, the charging LED 27 is turned on to indicate that charging is in progress.

Trickle charge mode When charging of the battery 2 is completed, the operation mode shifts to the trickle charge mode. Completion of charging is performed by the charging completion detection circuit 15. This detection is performed as follows. The terminal voltage of the battery 2 gradually increases during charging as shown in the graph of FIG. However, near the completion of the charging, the terminal voltage of the battery 2 has a point where the voltage decreases as indicated by the charging time t1 in FIG. The point in time when the drop amount becomes ΔV is detected, and it is determined that charging is completed. Such a method is called a -ΔV method.

The charging completion detecting circuit 15 detects the completion of charging of the battery 2 by the above-mentioned -ΔV method,
A signal indicating the completion of charging is given to 0. When the microcomputer 20 receives the signal indicating the completion of charging, the microcomputer 20
0 is turned on, and the quick charge switch circuit 6 is turned off.
The charging current output from the switching regulator circuit 5 is applied to the battery 2 via the trickle charge switch 10, trickle charge limiting resistor 11 (resistance value r2), diode 8, and battery terminal 9, and the current causes the battery 2 to trickle. Charged.

As described above, trickle charging is performed for the purpose of completely charging the NiCd battery and for the purpose of covering self-discharge of the battery 2. The current used in trickle charging is about 1/30 of the normal charging current,
It is a small current. In the case of a nickel-cadmium battery, the activation in the battery is weak, so that even if trickle charge is continuously supplied, a problem such as liquid leakage due to full charge does not occur. The microcomputer 20 turns off the switch 28 when the charging completion detection circuit 15 detects the completion of charging. Thereby, the charging LED 27 is turned off.

For some reason, the charging completion detecting circuit 15
There is a possibility that a case where the above-mentioned -ΔV drop voltage cannot be detected may occur. In such a case, the charging is continued, and the battery 2 may be damaged by the full charge, that is, the liquid may leak due to the overcharge. In order to prevent such inconvenience, the charging time may be limited by the timer 19 in some cases.

The memory circuit 23 is for preventing the operation of the charging circuit of the AC adapter 1a from becoming unstable due to rattling of the charging terminal 9 or the like. That is, the rattling of the battery terminal 9 may cause the output of the battery mounting detection circuit 14 to change finely between a value indicating the battery mounting and a value indicating the state in which the battery is removed. This is not only the rattling of the battery terminal 9 but also the operator intentionally disconnecting the battery 2 from the battery terminal 9.
It can also occur by attaching and detaching to the Memory circuit 23
Is provided so that mode switching does not occur until a certain time has elapsed.

FIG. 4 is a diagram showing a flow of a charging operation of the battery 2 by the AC adapter 1a. In FIG.
Each block is operated by an operator or AC adapter 1a
The line connecting each block represents a path through which the state of the AC adapter 1a changes depending on conditions.

Referring to FIG. 4, AC adapter 1a
By plugging the C plug 3 into the outlet (AC cord 41), when the battery is removed, the P-O
N-way, P-ON via path B when the battery arrives
The state moves to 43 respectively. Battery removal (PO)
After the power switch 22 is turned on in N42),
If the battery has just been removed, the state shifts to the AC adapter mode 49 via the path A1. In the AC adapter mode 49, a DC voltage is applied to the outside from the DC output terminal 29 as described above. When the power switch 22 is turned off in this state, the state changes to P via the path G.
Return to -ON42.

When the battery 2 is attached to the battery terminal 9 after the power switch 22 is turned on in the battery removal state (P-ON 42), the state of the AC adapter 1a shifts to the rapid charging mode 45 via the path B '. I do. In the quick charge mode 45, the charging current is supplied to the battery 2 via the battery terminal 9 as described above,
Is charged with the current. When the battery is removed in the operation mode of the quick charge mode 45, the state of the AC adapter shifts to the AC adapter mode 49 via the path A2. When charging is completed in the quick charge mode 45, the AC adapter shifts to the trickle charge mode 46 via the path H. When the battery is removed in the trickle charging mode 46, the state shifts to the AC adapter mode 49 via the path A3, and when the power is turned off, the state returns to the P-ON 43 via the path G1.

When the power switch 22 is turned on while the battery is loaded (P-ON 34), the operation of the AC adapter 1a shifts to the quick charge mode 45. The subsequent operation is P-
Since this is the same as the case where the state has shifted from the ON 42 to the quick charge mode 45, the details are omitted here.

[0023]

However, the above-described secondary battery charger has the following problems. In the case of a nickel-cadmium battery, there is a user's psychology that the user wants to charge the battery even after using it for a short time and always keep the battery fully charged. That is, short charging and discharging may be repeated as shown in FIG. However, in such a case, the memory effect (Memory) is added to the battery.
It is known that a phenomenon called Effect is caused.

Referring to FIG. 7, when the memory effect occurs,
The discharge curve of the battery (dotted line in FIG. 7) is lower than the normal discharge curve (solid line in FIG. 7). Therefore, even when the battery is fully charged, the usable time is shortened. In FIG. 7, the voltage of the battery is the final voltage (1.0 V).
The time of falling from t1 moves to t2. In other words, similarly, when the use of the battery is started from the fully charged state, the usable time is shorter than that in which the memory effect is caused but not used.

It is known that this memory effect can be eliminated by using up the battery once. This phenomenon is called a memory effect because the battery behaves as if it stores a partial discharge.

Although a unified theory has not been established as a cause of this phenomenon, one of the ideas is as follows. Referring to FIG. 8, the circles shown in FIGS. 8 (a) to 8 (e) represent the total amount of the active material (source for actually storing and discharging electric charge) in the battery.

FIG. 8A shows the battery before use. This battery has no memory effect. After the battery is fully charged as shown in FIG. 8B, the battery is partially discharged as shown in FIG. 8C. 8 (b) and 8 (c), hatched portions indicate active materials storing electricity, and white portions indicate discharged active materials.

It is assumed that such partial discharge and charge are repeated many times. Since the reaction of the active material is easily performed in a fixed portion, the electricity stored in the active material in the inner circle in FIG. 8C continues to be used without being used. As a result, as shown in FIG. 8 (d), when the battery is fully charged, the active material in the inner circle has passed for a long time after charging, whereas the active material on the outer circle has just been charged. May occur.

A process of completely discharging the battery as shown in FIG. In this case, first, the active material in the region outside the inner circle is discharged first. The battery voltage at this time is almost the same as a normal battery voltage.
After the discharge in the outer region is completed, discharge from the active material in the inner circle is started. As described above, this part has passed a long time after charging. Therefore, the battery voltage is low when discharging is being performed from this portion. As a result, it is considered that the above-described memory effect is caused.

Such a memory effect can be caused not only by discharge during use but also by repeating spontaneous discharge from a fully charged state. However, this is limited to repeated charging within one month. If left for 3 months or more, the voltage will be 1.0 V / cell or less.

The phenomenon of the use time due to the memory effect is about 1 to 1.5% in one short charge / discharge. It is known that the use time is reduced by about 20% after 20 charge / discharge cycles, and is reduced by up to about 30 to 50% when the charge / discharge cycle is repeated more.

As can be seen from the above description, in order to improve the memory effect, it is necessary to use up the battery once. In the case of a nickel-cadmium battery, the standard setting voltage of a single cell is 1.2 V. This is the voltage (final voltage) at which discharge is considered to be almost complete, that is, 1.0 V
The battery may be used until it drops below.

In order to solve such a problem, there is a so-called discharger for forcibly discharging the battery, and a charging device incorporating the discharger and forcibly discharging the battery before charging. .

However, if the battery is forcibly discharged in a state near full charge, the discharge time becomes longer. An apparatus in which the forced discharge is performed manually is not commercially desirable. Further, if the forced discharge is repeated many times, the life of the battery may be shortened.

Therefore, an object of the present invention is to provide a charging device for a secondary battery which can automatically suppress the occurrence of a memory effect and does not unduly increase the charging time of the secondary battery. It is.

[0036]

According to the present invention, there is provided a charging apparatus for a secondary battery in which a secondary battery can be attached and detached and a DC current for charging is supplied to the mounted secondary battery. Of the charging terminal and the attachment / detachment of the secondary battery to the charging terminal,
A predetermined first value is set when the secondary battery is attached to the charging terminal, and a predetermined second value is set when the secondary battery is removed.
And a battery attachment / detachment detecting means for outputting a battery attachment / detachment detection signal which takes a value of each of the following values: a secondary battery attached to the charging terminal in response to a change in the battery attachment / detachment detection signal from the second value to the first value. Detecting a terminal voltage of the battery and detecting whether or not the detected terminal voltage is within a voltage range between a predetermined upper limit and a predetermined lower limit equal to or higher than the end voltage of the secondary battery; Terminal voltage detecting means for responding, and if the detected terminal voltage is within the above voltage range, the secondary battery is forcibly discharged until the terminal voltage becomes equal to or lower than the end voltage. In response to the forced discharge means for causing the power supply, the terminal voltage detection means and the forced discharge means to detect that the detected terminal voltage is out of the voltage range or that the forced discharge by the forced discharge means has ended. And charge the secondary battery via the charging terminal. And a charging means for charging until the charging state to define the eye.

The charging device for a secondary battery according to claim 2 is
2. A manually operable forced discharge start signal output for outputting a forced discharge start signal for starting forced discharge of a secondary battery mounted on a charging terminal in addition to the device according to claim 1. Means for forcibly discharging the secondary battery in response to a forced discharge start signal, in addition to the case where the detected terminal voltage is within the above voltage range. .

[0038]

In the charging device for a secondary battery according to the first aspect, when the secondary battery is mounted on the charging terminal, the terminal voltage of the secondary battery is measured first. When the terminal voltage is out of the predetermined range, charging is started immediately. In other cases, the secondary battery is forcibly discharged by the forcible discharging means until the terminal voltage falls below the end voltage. Thereafter, charging is performed.

In the charging device for a secondary battery according to the second aspect, the forced discharge can be started manually by using the forced discharge start signal output means. Discharging is performed by the same forced discharging means that performs forced discharging by detecting a terminal voltage.

[0040]

FIG. 1 is a system block diagram of an AC adapter 1 equipped with a nickel-cadmium battery charging device according to the present invention. The AC adapter 1 shown in FIG. 1 is different from the conventional AC adapter 1a shown in FIG. 3 in that one terminal is connected to the output of a diode 8 and the other terminal is connected to a ground potential via a discharge resistor 17 and a microcomputer. On by 20 /
By being turned off, a discharge switch 16 serving as a discharging means for controlling the forcible discharge of the battery connected to the battery terminal 9 and a voltage at a connection point between the discharge control switch 16 and the discharge resistor 17 are detected. And a voltage detecting circuit 18 which is a terminal voltage detecting means for giving the information to the microcomputer 20. The charging device 1 further includes a refresh LED 25 for indicating that forced discharging is being performed and a switch 26 controlled by the microcomputer 20 connected in series between the switching regulator circuit 24 and the ground potential. In addition to the power switch 22, the microcomputer 20 is connected with a refresh switch 21 which is a forced discharge start signal output means used when an operator wants to forcibly discharge the battery 2.

1 and 3, the same parts are given the same reference numerals and names. Their functions are the same. Therefore, detailed description thereof will not be repeated here.

Since the resistance of the discharge resistor 17 may not shorten the life of the battery and cause problems such as heat generation, the load of the portable device connected to the AC adapter 1 is about 1/3 to about 1/3. It is good to set to 1/4.

Referring to FIG. 1, AC adapter 1 including the charging device according to one embodiment of the present invention operates as follows. The operation of the AC adapter 1 in the AC adapter mode is the same as that of the conventional one already described with reference to FIG. Therefore, the description is omitted here.

The charging of the NiCd battery 2 is performed as follows. When the NiCd battery 2 is mounted on the charging terminal 9, the battery mounting detection circuit 14 detects this and sends a signal indicating the battery mounting to the microcomputer 20. The microcomputer 20 turns on the forced discharge switch 16 in response to the output change of the battery attachment detection circuit 14. The quick charge switch circuit 6 and the DC output switch 12 are turned off. Voltage detection circuit 18 detects a terminal voltage of battery 2 and provides a signal representing the value to microcomputer 20.

The microcomputer 20 operates as follows in response to the output of the voltage detection circuit 18. The microcomputer 20 determines that the detected terminal voltage is about 0.8 V / cell of the battery 2.
If the voltage is 1.1 V, the switch 16 is kept on. Quick charge switch circuit 6, trickle charge switch circuit 1
0, the DC output switch 12 is kept off. As a result, the battery 2 is forcibly discharged through the switch 16 and the discharge resistor 17. The terminal voltage of the battery 2 decreases with the discharge.

When the terminal voltage of the battery 2 detected by the voltage detection circuit 18 becomes 0.8 V, the microcomputer 20 turns off the discharge control switch 16. The microcomputer 20 turns on the quick charge switch circuit 6. As a result, the rapid charging of the battery 2 is started as in the conventional device.

If the terminal voltage detected by the voltage detection circuit 18 when the battery 2 is mounted is 0.8 V or less per cell or 1.1 V or more, the microcomputer 2
0 immediately turns off the discharge control switch 16 and turns on the quick charge switch circuit 6. That is, in this case, charging is started immediately.

The reason why the terminal voltage of the battery 2 is detected once and the battery 2 is forcibly discharged in accordance with the value is as follows. As described above, the memory effect occurs when the partial discharge / charge of the battery is repeated. In order to eliminate the memory effect, it is necessary to almost use up the battery. By the way, even a user who uses the battery in such a manner as to repeat the partial discharge and charge as described above may use the battery for a longer time than usual and may be almost in a state of exhaustion. In such a case, the terminal voltage of the battery 2 approaches about 1.0 V per cell. At this time, by automatically discharging the terminal voltage to 1.0 V or less per cell, the memory effect is surely eliminated. The frequency of forced discharge does not increase, and the problem that the life of the battery is shortened is less likely to occur.
Also, as shown by the solid curve in FIG. 7, when the terminal voltage is 1.1 V or less per cell, the slope of the discharge curve is large. Therefore, in this portion, the time t required for discharge is t
0 can be shortened.

That is, a discharge control switch 16, a discharge resistor 17, and a voltage detection circuit 18 are newly provided,
To detect the terminal voltage when the battery 2 is attached to the
When the terminal voltage is within a predetermined range, the battery 2 is forcibly discharged, so that the memory effect of the battery 2 is automatically eliminated or its occurrence is suppressed.

In this case, there is a problem in which range of the terminal voltage the forced discharge is automatically performed. Generally, when designing a portable device, the number of cells of the battery used and the nominal voltage are about 1 to the minimum operating voltage of the device.
The voltage is selected so as to increase the voltage by 0%. This is to make the weight of the battery as small as possible.

For example, if the minimum operating voltage of the device is 5.3 V
In the case of the above, a battery having a nominal voltage of 6 V using five cells is used, and a battery having a nominal voltage of 9.6 V using eight cells is used when the minimum operating voltage of the device is about 8.8 V. Is designed to drive the device. Judging from this numerical value, the voltage per cell of the NiCd battery required for normal operation of the device is about 1.1.
It can be seen that it is about V. However, if the NiCd battery is charged when the terminal voltage per cell becomes about 1.1 V, a memory effect may be generated. Therefore, in order to eliminate the memory effect, the terminal voltage must be 1.0
It is desirable that the battery be discharged until the voltage falls below V. In the case of the present embodiment, this voltage was set to about 0.8 V in order to ensure discharge.

Even when the battery is automatically discharged as described above, the charging LED 27 is turned on in the same manner as during normal charging. This is to avoid user confusion.

The refresh switch 21 is connected to the charging terminal 9
Is provided for instructing the microcomputer 20 to forcibly discharge the battery attached to the microcomputer 20 irrespective of its terminal voltage. Such forced discharge of the battery is called "refresh". The refresh is performed according to the user's intention, for example, when it is felt that a memory effect has occurred in the battery 2.

Refresh is useful for those who frequently use a portable device powered by a battery (the person who uses the portable device shown in FIG. 6). In such a state of use, discharging / charging is repeated while the terminal voltage of the battery 2 is kept at 1.1 V or more per cell. When charge / discharge is repeated many times as described above, the memory effect may be clearly felt even when the terminal voltage is 1.1 V or more. In such a case, the automatic discharge by the voltage detection circuit 18 cannot cope. Refresh should be performed in such a case. Therefore, this refresh is not performed so frequently.

In the refresh mode, the AC adapter 1 operates as follows. Refresh switch 2
When 1 is pressed, the microcomputer 20 turns off the quick charge switch circuit 6 and the trickle charge switch circuit 10.
The discharge control switch 16 is turned on. The battery 2 mounted on the battery terminal 9 is forcibly discharged via the discharge control switch 16 and the discharge resistor 17. At this time,
The microcomputer 20 turns on the switch 26 and turns on the switch 28
FF. The refresh LED 25 lights up, and the user can know that the forced discharge is being performed. When the terminal voltage output from the voltage detection circuit 18 becomes sufficiently low, for example, about 0.8 V or less, the microcomputer 20 turns off the forced discharge switch 16 and also turns off the switch 26. Further, since the battery 2 should normally be charged, the microcomputer 20 turns on the quick charge switch circuit 6 and turns on the switch 28.
Is also turned on. As a result, the battery 2 is charged, and the charging LED 27 lights up to indicate that charging is in progress. The operation of the AC adapter 1 after the completion of charging is the same as that of the conventional device. Therefore, detailed description thereof will not be repeated here.

In the AC adapter shown in FIG.
A forced discharge circuit for refreshing and a discharge circuit for automatically discharging by detecting a terminal voltage are also used. Therefore, an increase in cost can be suppressed as compared with a charging device with a refresh function incorporated in a conventional AC adapter.

FIG. 2 is a flowchart showing a flow of the operation of the AC adapter shown in FIG. FIG. 2 differs from the flowchart showing the operation of the conventional AC adapter shown in FIG. 4 in that when the power is turned on with the battery 2 attached to the battery terminal 9, the terminal voltage of the battery is detected. (Voltage detection 44), processing of automatic discharge 47 automatically performed when the detected terminal voltage is within a predetermined range, and forced discharge processing 48 performed when the refresh switch 21 is pressed. Are newly provided.

In FIGS. 2 and 4, the same processes or corresponding processes are given the same reference numerals and names. The processing performed in them is the same.
Therefore, the description thereof is omitted here.

Automatic discharge processing 47 and forced discharge processing 48
Is executed according to the following flow. When the battery 2 is mounted after the process of the P-ON 42 is performed on the battery terminal 9, the state of the AC adapter shifts to the process of the voltage detection 44 via the path B1. In the voltage detection 44,
As described above, the terminal voltage of the battery 2 is measured, and it is determined what range the value is. When the voltage per battery cell is about 0.8 V or less or about 1.1 V or more, the state of the AC adapter 1 shifts to the process of the quick charge 45 via the path C. On the other hand, when the voltage per battery cell is about 0.8 V to 1.1 V,
The state of the adapter 1 shifts to the processing of the automatic discharge 47 via the path D.

When the terminal voltage of the battery 2 drops to about 0.8 V per cell during the execution of the automatic discharge 47, A
The state of the C adapter 1 shifts to the process of the quick charge 45 via the path E. When the refresh switch 21 is turned on during the processing of the automatic discharge 47, the state of the AC adapter 1 shifts to the state of the forced discharge 48 via the path F. Quick charge 4
The same applies when the refresh switch is pressed during the execution of the trickle charge mode 46 or the trickle charge mode 46.

When the forced discharge of the battery 2 is completed by the process of the forced discharge 48, the state of the AC adapter shifts to the state of the quick charge 45 via the path I.

That is, the memory effect of the battery 2 can be automatically eliminated by providing a path in which the process of the quick charge 45 is performed after the process of the automatic discharge 47. Further, in any of the automatic discharge 47, the quick charge 45, and the trickle charge mode 46, when the refresh switch 21 is pressed, the operation of the AC adapter shifts to the process of the forced discharge 48 (F, F1, F).
2). Thus, a memory effect that cannot be dealt with by the automatic discharge 47 can be eliminated according to the user's intention.

In the above-described embodiment, the voltage per cell of the battery to be forcibly discharged is 0.8 to 1.1 V
Was set in the range. However, the present invention is not limited to this, and this range may be slightly changed.

[0064]

As described above, in the secondary battery charging device according to the first aspect, the terminal voltage of the secondary battery is checked before starting charging. When the terminal voltage is out of the predetermined range, charging is started immediately. In other cases, forcible discharging of the secondary battery is automatically performed prior to charging. As compared with the case where there is no forced discharge, the chances of completely discharging the secondary battery are increased, and the memory effect can be eliminated. The frequency of forced discharge is lower than the case where forced discharge is performed unconditionally, and the life of the secondary battery is not unduly shortened. Furthermore, since forced discharge is performed only when the terminal voltage is close to the terminal voltage of the secondary battery, the discharge can be completed in a short time, and the time required for charging is not unduly lengthened.

The secondary battery charging device according to the second aspect has the following effects in addition to the effects of the device according to the first aspect. In this device, the discharge by the forced discharge means can be started manually by the user. Therefore, the memory effect that cannot be dealt with by the automatic forced discharge by the device according to the first aspect can be effectively eliminated. In addition, the means described in claim 1 can be used as it is as the forced discharge means itself, and the apparatus does not need to be unduly complicated.

[Brief description of the drawings]

FIG. 1 shows an AC having a charging device according to an embodiment of the present invention.
It is a system block diagram of an adapter.

FIG. 2 is a flowchart showing a flow of operation of the device shown in FIG. 1;

FIG. 3 is a system block diagram of an AC adapter incorporating a conventional charging device.

FIG. 4 is a flowchart showing an operation flow of a conventional AC adapter.

FIG. 5 is a graph showing a relationship between a charging time and a voltage per cell of a battery.

FIG. 6 is a graph showing a relationship between time and voltage per battery cell when short charge / discharge is performed.

FIG. 7 is a graph showing the relationship between the operating time and the voltage per cell of the battery, showing the effect of the memory effect of the battery.

FIG. 8 is a schematic diagram for explaining the cause of the memory effect.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 AC adapter 2 NiCd battery 6 Quick charge switch circuit 9 Battery terminal 10 Trickle charge switch 12 DC output switch 14 Battery mounting detection circuit 15 Charge completion detection circuit 16 Discharge control switch 17 Discharge resistor 18 Voltage detection circuit 20 Microcomputer 21 Refresh switch

Claims (2)

(57) [Claims] A charging terminal for supplying a DC current for charging to the mounted secondary battery, and detecting attachment / detachment of the secondary battery to / from the charging terminal. When a secondary battery is attached to the charging terminal, a first predetermined
Battery detachment detection means for outputting a battery detachment detection signal that takes a predetermined second value when the battery is detached, and the first value from the second value of the battery detachment detection signal. In response to the change to the value, the terminal voltage of the secondary battery attached to the charging terminal is detected, and the detected terminal voltage is equal to or higher than a predetermined upper limit and the terminal voltage of the secondary battery. A terminal voltage detecting means for detecting whether or not the voltage falls within a voltage range between a predetermined lower limit, and a response to the terminal voltage detecting means, wherein the detected terminal voltage is within the voltage range. In the case, the terminal voltage responds to the forced discharge means for forcibly discharging the secondary battery until the terminal voltage becomes equal to or lower than the end voltage, and the terminal voltage detection means and the forced discharge means,
Detecting that the detected terminal voltage is out of the voltage range or that the forcible discharging by the forcible discharging means has ended, charging the secondary battery to a predetermined charging state via the charging terminal. And a charging unit for charging the secondary battery. 2. A secondary battery charging apparatus according to claim 1, wherein said secondary battery is connected to said charging terminal and outputs a forced discharge start signal for starting a forced discharge of said secondary battery. Further comprising a manually operable forced discharge start signal output means, wherein the forced discharge means responds to the forced discharge start signal in addition to the case where the detected terminal voltage is within the voltage range. A charging device for a secondary battery, wherein the secondary battery is forcibly discharged.