JP2836677B2 - Rechargeable battery charger with charging completion time display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging apparatus for charging a secondary battery by a constant voltage and constant current control method, and more particularly, to a charging apparatus having a means for displaying a time until charging is completed.

[0002]

2. Description of the Related Art At present, demand for cordless devices such as video movies and laptop personal computers has increased, and rechargeable secondary batteries (storage batteries) such as Ni-Cd (nickel cadmium) batteries have been developed and improved as power sources. It is being actively performed.

[0003] As a conventional charging method of a secondary battery, a timer is operated from the time when a battery is set in a charger,
Timer control method that completes charging when charging is performed at a constant current of about 1/5 of the battery capacity for 6 to 8 hours, and characteristics of Ni-Cd and Ni-MH secondary batteries in which the battery voltage decreases when the charge amount is saturated A -dV control method is generally known in which the voltage of a battery terminal is monitored during charging and charging is completed when a voltage drop is detected.

On the other hand, in recent years, lithium ion secondary batteries smaller in size and higher in performance than Ni-Cd batteries have been developed and have attracted attention. This lithium-ion secondary battery does not use harmful substances such as cadmium, can have a much higher energy density than Ni-Cd batteries, and has no memory effect, so refresh the battery when charging. There is an advantage that there is no need.

As a charging method for the lithium ion secondary battery, a constant voltage / constant current control method, which is not suitable for Ni-Cd and Ni-MH secondary batteries, is used. FIG. 5 shows an example of a conventional charging device employing a constant voltage / current control method.
Shown in

The charging apparatus shown in FIG. 5 includes a constant current circuit 1, a constant voltage circuit 2, a switch circuit 3, a control circuit 4, a timer circuit 5, and a display 6 such as an LED. In this charging device, when the secondary battery 8 is connected to the output terminal 7 with the power supply connected to the input terminal, the switch circuit 3 is turned on to start charging. At this time, the constant current circuit 1 supplies a charging current not exceeding a predetermined current value to the secondary battery, and the constant voltage circuit 2 supplies a charging voltage not exceeding a predetermined voltage value to the secondary battery. .

On the other hand, the switch circuit 3
Outputs an ON signal to the control circuit 4. When the ON signal is input, the control circuit 4 activates the timer circuit 5 and causes the display 6 to indicate that the battery is being charged. The display on the display 6 is performed by, for example, turning on an LED.

When a predetermined time set in the timer circuit 5 has elapsed, the timer circuit 5 notifies the control circuit 4 of the time-up. When the control circuit 4 receives the notification of the time-up, the control circuit 4 turns off the switch circuit 3 to terminate the charging.
At the same time, the control circuit 4 stops the display indicating that the display 6 is charging, or displays the end of charging. The display of the end of charging is performed by, for example, turning off an LED indicating that charging is being performed, or turning on an LED of a different color (for example, lighting from green to red).

[0009]

As described above, lithium-ion secondary batteries include Ni-Cd batteries and Ni-MH batteries.
Unlike secondary batteries, there is no need to refresh when charging. For this reason, charging of the lithium ion secondary battery is performed in a state where the amount of remaining electricity differs for each battery. That is, in the case of a lithium ion secondary battery, the time required for charging differs for each battery.

However, the conventional charging device of the constant-voltage / constant-current control method has a problem that the time required for the completion of the charging is not known because the charging time is only displayed during the charging and the completion of the charging.

Further, there are various means for detecting the heat generation of the battery at the time of completion of charging and notifying the completion of charging (for example, Japanese Unexamined Patent Publication No. 60-13376 discloses a temperature indicator which changes color depending on temperature. However, in any of these cases, it is impossible to know the time required to complete charging.

If it is possible to know the time required to complete charging while charging a lithium ion secondary battery, it is possible to charge batteries having different amounts of remaining electricity only for a time suitable for each. Not only will it not be frustrating to wait for charging to be completed,
Since the remaining amount of electricity can be known from the required time, the charging can be stopped when the required amount of electricity is accumulated without waiting for the completion of charging, and the convenience is improved.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a charging device for a secondary battery with a charging completion time display, which can solve the above-mentioned conventional drawbacks and allows the user to know the time required to complete charging during charging.

[0014]

According to the present invention, in a charging apparatus for charging a secondary battery by a constant voltage / constant current control method, storage for storing a charging voltage characteristic curve and a charging current characteristic curve of the secondary battery. Circuit, a voltage detection circuit and a current detection circuit for detecting a charging voltage and a charging current supplied to the secondary battery, the charging voltage characteristic curve and the charging current characteristic curve, the voltage detection circuit and the current detection circuit Based on the charging voltage and the charging current detected by
Charging voltage characteristic curve and charging current stored in the storage circuit
A control circuit that determines a time until the completion of charging from the characteristic curve and generates a time signal indicating the time until the completion of charging, and a display that receives the time signal and displays the time until the completion of charging. Thus, a charging device for a secondary battery with a charging completion time display is obtained.

Here, when the charging voltage is smaller than a predetermined constant voltage control voltage value, the control circuit specifies the position of the charging voltage on the charging voltage characteristic curve, and determines the position of the charging voltage on the specified curve. The time signal is generated based on the position of. Further, when the charging current is smaller than a predetermined constant current control current value, the control circuit specifies a position of the charging voltage on the charging voltage characteristic curve, and based on the specified position on the curve. To generate the time signal.

Alternatively, the control circuit specifies a position of the charging current on the charging current characteristic curve when the charging voltage matches a predetermined constant voltage control voltage value, and The time signal is generated based on a position. Further, the control circuit specifies a position of the charging voltage on the charging voltage characteristic curve when the charging current matches a predetermined constant current control current value, and determines a position on the specified curve. To generate the time signal.

Further, according to the present invention, the storage circuit includes:
Selection means for storing a plurality of storage areas for storing a charging voltage characteristic curve and a charging current characteristic curve of a plurality of different types of secondary batteries, and selecting the storage area according to the type of the secondary battery to be charged Is provided, a charging device for a secondary battery with a charging completion time display is obtained.

Further, according to the present invention, there is provided a switch circuit which is turned off in response to a control signal, and causes the control circuit to output the control signal when the time signal indicates zero, thereby automatically charging the battery. A charging device for a secondary battery with a charging completion time display, characterized by being stopped.

[0019]

With the above arrangement, the charging device for a secondary battery with a charging completion time display of the present invention detects the current and voltage of the secondary battery during charging, and stores the charging voltage characteristic curve and the charging voltage stored in the storage circuit. By comparing the current characteristic curve with the current characteristic curve and calculating the time until the completion of charging, and displaying the result on a display such as an LCD, the secondary charging during charging can be performed at any time including charging. It is possible to know the remaining time required to complete the charging of the battery.

In the constant voltage / constant current control method of the secondary battery, as shown in the charge voltage characteristic diagram of FIG. 2A, the charge voltage increases in the first half of the entire charge time and becomes a constant voltage control voltage value Vc. Once reached, it is kept constant in the second half.

On the other hand, as shown in FIG. 2B, the charging current is maintained at the constant current control current Ic in the first half of the total charging time, and decreases in the second half. Therefore, when the charging voltage of the secondary battery being charged is lower than Vc (for example, the voltage V
0) specifies a point (point P0 with respect to voltage V0) on the charging voltage characteristic curve shown in FIG. 7A, and thereby, a time t0 until charging is completed is obtained.

The charging current of the secondary battery being charged is Ic
(For example, current I1), a point (point P1 with respect to current I1) on the charging current characteristic curve shown in FIG. Desired.

[0023]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a charging apparatus for a secondary battery with a charging completion time display according to the present invention. FIG. 1 shows an embodiment of the present invention.
Here, the same components as those in the related art are denoted by the same reference numerals.

The rechargeable battery charger with a charge completion time display shown in FIG. 1 has a constant current circuit 1, a constant voltage circuit 2,
And a switch circuit 3, a current detection circuit 9, a voltage detection circuit 10, a control circuit 11 different from the conventional one, and a storage circuit 1.
2 and a display 13 different from the conventional one.

This charging device basically has an input terminal 14
The constant current circuit 1 and the constant current circuit 2 limit the current and voltage from the power supply connected to the power supply so as not to exceed the predetermined current and voltage, and charge the lithium ion secondary battery 15 connected to the output terminal 7. Is what you do.

The current detection circuit 9 and the voltage detection circuit 10
These are for detecting a charging current and a charging voltage for the lithium ion secondary battery 15, respectively, and the detected charging current value and charging voltage value are sent to the control circuit 11.

The storage circuit 12 stores in advance a charging voltage characteristic curve and a charging current characteristic curve of the lithium ion secondary battery 15 by the present charging device, and stores the charging current values from the current detection circuit 9 and the voltage detection circuit 10 and When the charging voltage value is input to the control circuit 11, it is read by the control circuit 11.

The control circuit 11 calculates the time until the completion of charging based on the charging voltage characteristic curve and the charging current characteristic curve read from the storage circuit 12 and the input charging current value and charging voltage value.

Here, when the input charging voltage value is equal to or lower than the predetermined constant voltage control voltage, the control circuit 11 specifies the position of the charging voltage value on the charging voltage characteristic curve and determines the time until the charging is completed. When the charging current value is equal to or less than the predetermined constant current control current value, the position of the charging current value on the charging current characteristic curve is specified, and the time until charging is calculated.

More specifically, the charging voltage characteristic curve and the charging current characteristic curve are as shown in FIGS. 2A and 2B, respectively. That is, the lithium ion battery 15
Is smaller than the predetermined value, the constant current circuit 1 operates to set the charging current It as the constant current control current value I
A current equal to c flows. At this time, the terminal voltage Vt is
In accordance with the remaining amount of electricity, the voltage is required to flow the charging current It equal to the constant current control current value Ic. That is, the terminal voltage Vt increases as the amount of remaining electricity increases. If the remaining amount of electricity is larger than a predetermined value, the terminal voltage Vt
Is a constant voltage control voltage value Vc
Is kept. At this time, the charging current It decreases as the amount of remaining electricity increases. Here, assuming that the remaining amount of electricity is a function of the charging time, the charging voltage characteristic curve and the charging current characteristic curve are as shown in FIGS. 2A and 2B, respectively. Therefore, the time until the charging is completed can be obtained as follows.

For example, when the charging voltage detected by the voltage detecting circuit 10 is V0, as shown in FIG.
The point P0 on the charging voltage curve can be specified. Thereby, the time t0 until the completion of charging is obtained.

When the detected charging voltage is the constant voltage control voltage value Vc, the charging completion time cannot be obtained from the charging voltage characteristic curve. In this case, the time is calculated by comparing the charging current detected by the current detection circuit 9 with the charging current characteristic curve. For example, when the detected charging current is I1, the point P1 on the charging current characteristic curve is specified as shown in FIG. 2B, and the time t1 until the charging is completed can be obtained from this.

The operation of the charging device shown in FIG. 1 will be described below with reference to FIG. First, when the lithium ion secondary battery 15 is mounted on the output terminal 7, the switch circuit 3 detects this and turns off, and charging is started. The current detection circuit 9 and the voltage detection circuit 10 detect a charging current and a charging voltage, respectively.

The control circuit 11 first receives a current detection value It from the current detection circuit 9 in step S11. Then, in step S12, the detected current value It
And the constant current control current value Ic. As a result of the comparison, when the detected current value It is equal to the constant current control current value Ic,
Proceeding to step S13, the voltage detection value Vt from the voltage detection circuit 10 is received. Then, in step S14, the charging time Tt corresponding to the voltage detection value Vt is called from the storage circuit 12. As a result of the comparison, the detected current value It
Is not equal to the constant current control current value Ic, step S
15 and the time Tt corresponding to It from the storage circuit 12
Call.

Next, the control circuit 11 determines in step S16 the time Tc required to charge the completely discharged battery.
And the time Tt called from the storage circuit 12 to determine the time t required for charging. That is, t = Tc−Tt is calculated. Then, in step S17, the time t required for charging is displayed on the display unit 13.

Thereafter, the control means 11 proceeds to step S18.
It is determined whether the time t required for charging is "0". t =
In the case of 0, the process proceeds to step S19 and the switch circuit 3
Is output, and the operation is terminated. If t ≠ 0, the process returns to step S11 to repeat the above operation.

In the above example, first, at step S11
Receives the current detection value It and compares it with the constant current control current value Ic at step S12. However, as shown in FIG. 4, the voltage detection value Vt is received at step S22, and the constant voltage control voltage value is received at step S23. You may make it compare with Vc. In this case, if Vt = Vc, the current detection value It is received in step S23, and the process proceeds to step S24.
Then, the charging time Tt corresponding to the current detection value It is read from the storage circuit 12, and if Vt ≠ Vc, the charging time Tt corresponding to the voltage detection value Vt may be read from the storage circuit 12.

In the above embodiment, the relationship between the charging time and the charging current and the charging voltage is stored in the memory. However, the relationship between the time until the charging is completed and the charging current and the charging voltage is stored. Otherwise, the time calculation step S1
6 can be omitted.

Furthermore, in the above embodiment, the charging device is configured to correspond to one type of lithium ion secondary battery 15, but a plurality of types of secondary batteries (for example, those having different voltages, chemical devices, Components having different components).

That is, an area for storing the charging voltage characteristics and the charging current characteristics of a plurality of types of secondary batteries is provided in the storage circuit, these are stored, and the types of the secondary batteries attached to the output terminals are stored. According to the control circuit, select an appropriate charging voltage characteristic and charging current characteristic from the storage circuit.
What is necessary is just to compare with the detected current value and voltage value. Here, in order to read out appropriate charging voltage characteristics and charging current characteristics from the storage circuit, the storage area read by the control circuit may be manually switched according to the type of the secondary battery, or an identifier may be assigned to the secondary battery. May be provided, an identifier detector may be provided in the charging device, and the storage area may be automatically selected according to a detection signal from the identifier detector. As the identifier, for example, a resistor or a change in shape can be used. When a resistor is used, the identifier detector detects the terminal voltage or terminal current of the resistor to detect the type of the secondary battery. When a change in shape is used, the type of secondary battery is detected using a mechanical switch as an identifier detector.

Further, in the above-described embodiment, the case where the time from the start of charging to the completion of charging is continuously displayed is described. However, the display only at the start of charging or a request from the user has been made. There may be various forms such as a display only at the time or a display at a predetermined time interval.

As described above, the present invention has been described with reference to the preferred embodiments. However, the present invention is not necessarily limited to the above-described embodiments, and various improvements and modifications may be made based on the description in the claims. It is possible to apply as a charging device for another secondary battery instead of the lithium ion secondary battery.

[0043]

As described above, in the charging device for a secondary battery according to the present invention, the charging characteristic curve of the secondary battery is stored in the storage circuit in advance, and the voltage at the time of charging detected by the voltage detection circuit and the current detection circuit. The control circuit compares the current with the contents stored in the storage circuit, calculates the time until the charging is completed, and can display the calculated time on the display, thereby improving the convenience.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIGS. 2A and 2B are graphs showing charging characteristics of a secondary battery according to a constant voltage / constant current control method, wherein FIG. 2A is a charging voltage characteristic diagram and FIG. 2B is a charging current characteristic diagram.

FIG. 3 is a flowchart illustrating an example of an operation of the control circuit of FIG. 1;

FIG. 4 is a flowchart illustrating another example of the operation of the control circuit of FIG. 1;

FIG. 5 is a block diagram showing a configuration of a conventional secondary battery charger.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Constant current circuit 2 Constant voltage circuit 3 Switch circuit 4 Control circuit 5 Timer circuit 6 Display 7 Output terminal 8 Secondary battery 9 Current detection circuit 10 Voltage detection circuit 11 Control circuit 12 Storage circuit 13 Display 14 Input terminal 15 Lithium ion Rechargeable battery

Claims (7)

(57) [Claims] 1. A charging device for charging a secondary battery by a constant voltage / constant current control method, a storage circuit for storing a charging voltage characteristic curve and a charging current characteristic curve of the secondary battery, A voltage detection circuit and a current detection circuit for detecting a charging voltage and a charging current, a charging voltage characteristic curve and a charging current characteristic curve, and the charging voltage and the charging detected by the voltage detection circuit and the current detection circuit. Based on the current , the charging voltage characteristic stored in the storage circuit is stored.
Time from charging curve and charging current characteristic curve
And a control circuit for generating a time signal representing the time until the completion of the charging, and a display for receiving the time signal and displaying a time until the charging is completed. Rechargeable battery charger. 2. The control circuit specifies a position of the charging voltage on the charging voltage characteristic curve when the charging voltage is smaller than a predetermined constant voltage control voltage value,
The charging device for a secondary battery with a charging completion time display according to claim 1, wherein the time signal is generated based on the specified position on the curve. 3. The control circuit specifies a position of the charging voltage on the charging voltage characteristic curve when the charging current is smaller than a predetermined constant current control current value,
The charging device for a secondary battery with a charging completion time display according to claim 1, wherein the time signal is generated based on the specified position on the curve. 4. The control circuit specifies a position on the charging current characteristic curve of the charging current when the charging voltage matches a predetermined constant voltage control voltage value, and determines a position on the specified curve. The charging device for a secondary battery with a charging completion time display according to claim 1, wherein the time signal is generated based on a position. 5. The control circuit specifies a position of the charging voltage on the charging voltage characteristic curve when the charging current matches a predetermined constant current control current value, and determines a position on the specified curve. The charging device for a secondary battery with a charging completion time display according to claim 1, wherein the time signal is generated based on a position. 6. The storage circuit has a plurality of storage areas for storing a charging voltage characteristic curve and a charging current characteristic curve of a plurality of secondary batteries of different types. 6. The charging device for a secondary battery with a charging completion time display according to claim 1, further comprising a selection means for selecting the storage area in accordance with the information. 7. A switch circuit for receiving a control signal to turn off the charging circuit, wherein the control circuit outputs the control signal when the time signal indicates zero, thereby automatically stopping charging. Claim 1, characterized in that:
A charging device for a secondary battery with 2, 3, 4, 5, or 6 charging completion time displays.