JPH0819190A - Charger for lithium ion battery - Google Patents

Abstract

PURPOSE:To obtain a charger which eliminates a trouble to wait up to the stop of a charging operation irrespective of the charging residual capacity of a battery, to be charged, by a method wherein the charging residual capacity prior to a point of time in which the battery to be charged is charged fully is set in advance and the battery to be charged is charged for a prescribed time from a point of time in which the charging residual capacity is detected. CONSTITUTION:A charging current prior to a point of time when a battery 6 to be charged is charged fully is set. The charging current is detected by a charging-current detection circuit 7 so as to be monitored by a control circuit 11. Then, when the charging current becomes a set current, the control circuit 11 turns off a transistor, and a timer time is changed over to a timer time in which the transistor is turned off in 30 minutes from a timer time of four hours. That is to say, the total number of clocks is changed over to a setting operation to count in 30 minutes from an initial setting operation to count in four hours. Thereby, the timer time is forwarded fast, and it is possible to eliminate a trouble to wait for many hours up to the stop of a charging operation irrespective of the residual capacity of the battery 6 to be charged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium ion battery charger, and more particularly to a lithium ion battery charger for controlling charging time.

[0002]

2. Description of the Related Art For charging a battery that can be repeatedly charged and discharged, a constant current charging method or a constant voltage charging method that utilizes the charging characteristics of the battery to be charged is generally used. For example, a constant current charging method is used for nickel-cadmium batteries and nickel-hydrogen batteries, and a constant-current charging method is used for lithium-ion batteries at the beginning. Not to
Switch to constant voltage charging method.

Now, when a charger for a lithium ion battery which is preset so as to stop charging at a time (charging stop time T) at which an uncharged battery (empty battery) can be fully charged, the remaining charge capacity is It is suitable for charging a battery with a low (remaining capacity after charging) or an uncharged battery, but it is relatively quick to charge a battery with a high remaining charging capacity (battery close to full charge). Charging continues despite reaching the state of charge.

FIG. 6 is a diagram showing charge characteristics when a battery having a large remaining charge capacity is charged using the above-mentioned lithium ion battery charger.

In FIG. 6, the horizontal axis represents the charging time [H]. The vertical axis represents charging current [I] and charging voltage [V]
Is. 0 is the origin. The charge stop time T is a time during which an uncharged battery can be fully charged.

The charging current of the battery to be charged has a characteristic that it converges to 0 as it approaches full charge. Further, the charging voltage of the battery to be charged has a characteristic of converging to a constant voltage as it approaches full charge. Almost 0 (generally 10 to 20 [mA]) in most lithium ion battery chargers
When the charging current that has reached is detected, the target battery has reached the fully charged state.

From FIG. 6, it can be seen that the battery to be charged has already reached the fully charged state before the charging stop time T.

Japanese Patent Laid-Open Publication No. 6-38392 proposes some means for controlling the charging time of a charger for a lithium-ion battery using the characteristics of the charging current at the time of full charge, and particularly for controlling the time for stopping charging. Has been done.

One of the means is to set the charge stop time by using the battery voltage before the charging of the battery to be charged. That is, the charging voltage before the start of charging is detected, first, the remaining charge capacity is calculated from the detected charging voltage, and then, from the remaining charge capacity, the charged battery is fully charged,
Alternatively, the charging time required for almost full charge (inversely proportional to the remaining charge capacity) is calculated, and the charging stop time is set based on the calculated charging time. Since the voltage to be charged has various values depending on the battery to be charged, all of these calculations are executed by a calculation circuit such as a microcomputer installed in the charger for the lithium-ion battery each time. It was

Further, in the charger for a lithium ion battery disclosed in Japanese Patent Laid-Open No. 62-100139, when a full charge is detected, the timer time is made to be extremely fast and counted up to stop the charging. Had control.

[0011]

However, the charging voltage of the battery to be charged before the start of charging is detected, and the charging device for the lithium ion battery is equipped with the detected charging voltage according to the detected various charging voltage values. Since it was necessary to calculate the charging time using an arithmetic circuit such as a microcomputer, and to set the charging stop time according to the charging time, the size of the lithium ion battery charger is large for that microcomputer. ,
There is a problem that the weight becomes heavy and causes a cost increase.

Further, in order to detect the full charge, a very small charging current converged to 0 at the time of full charge (generally 10 to 10).
20 [mA]) is difficult to detect, and
There is also a problem that the detection circuit may malfunction due to noise or the like.

The present invention has been made in order to solve the above problems, and does not have to bother waiting for a long time until charging is stopped, regardless of the remaining charge capacity of the battery to be charged.
An object of the present invention is to obtain a lithium-ion battery charger that is compact, lightweight, and cost-effective.

[0014]

The lithium-ion battery charger according to claim 1 of the present invention comprises a setting means for presetting the remaining charge capacity of the charged battery before the charged battery is fully charged. Detection means for detecting the remaining charge capacity set by the setting means, and charging means for charging the battery to be charged for a predetermined time from the time when the remaining charge capacity is detected by the detection means are provided. .

A lithium ion battery charger according to a second aspect of the present invention is provided with control means for controlling the predetermined time of the lithium ion battery charger according to the first aspect at the time when the remaining charge capacity is detected. It is a thing.

[0016]

In the lithium ion battery charger according to claim 1, the charge remaining capacity of the battery to be charged before being fully charged is preset, and the chargeable battery is charged for a predetermined time from the time when the charge remaining capacity is detected. Since the battery is charged, the charging is quickly stopped when the battery to be charged is fully charged without using a computing device such as a microcomputer.

In the lithium ion battery charger according to the second aspect of the present invention, the predetermined time is controlled when the remaining charge capacity is detected. Therefore, the predetermined time is switched to an appropriate time required for full charge. It is possible.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a lithium ion battery charger according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of a lithium ion battery charger.

In FIG. 1, a lithium ion battery charger includes a power supply circuit 1, a power conversion circuit 3, and an output circuit 5.
The charging target battery 6, a charging current detection circuit 7, a charging voltage detection circuit 9, a control circuit 11, a timer control circuit 13, and a timer IC 15.

The power supply circuit 1 is A when it is an AC input power supply.
C input power is rectified and smoothed, converted to DC, and output. In the case of a DC input power source, it is output as it is. The power conversion circuit 3 is connected to the power supply circuit 1 and the control circuit 11,
The DC power input from the power supply circuit 1 is converted into necessary electric power (voltage and current) in accordance with the charging method based on the charging information obtained from the control circuit 11.

The charging information obtained from the control circuit 11 includes
The charging current detection circuit 7, the charging voltage detection circuit 9, and various information given from the timer control circuit 13 described below, and the charging method and the timer time set by the control circuit 11 based on the information are included.

The output circuit 5 is connected to the power conversion circuit 3 and outputs a stable charging voltage and charging current by rectifying and smoothing the power input from the power conversion circuit 3. The battery 6 to be charged is connected to the output circuit 5 and is charged by the charging voltage and the charging current output from the output circuit 5. The charging current detection circuit 7 is connected to the output circuit 5 and detects the charging current output from the output circuit 5. The charging voltage detection circuit 9 is also connected to the output circuit 5 and detects the charging voltage output from the output circuit 5.

The control circuit 11 includes a charge completion display section,
It is connected to the charging current detection circuit 7 and the charging voltage detection circuit 9, and based on the charging current detected by the charging current detection circuit 7 and the charging voltage detected by the charging voltage detection circuit 9, The charging status is determined, and the timer time of the timer IC 15 and the charging method are switched.

The timer control circuit 13 is connected to the control circuit 11 and has elements (switches and resistors and capacitors) for changing the oscillation frequency of the timer IC 15. The timer IC 15 is the timer control circuit 1
3 and oscillates at an oscillation frequency determined by the time constants of the elements (switches, resistors and capacitors) in the timer control circuit 13. Then, the timer time is counted by the clock of the oscillation frequency, and when the counted number of clocks reaches the preset total number of clocks, a signal to stop charging and a charge stop display if necessary are displayed. To output to the control circuit 11.

When the charging time information is given, the control circuit 11 sends out the above-mentioned various charging information to the power conversion circuit 3 if it is not fully charged. If the battery is fully charged, the charging completion is displayed. In this embodiment, the control circuit 11 includes the charging completion display unit, but the charging completion display unit may be connected to the outside of the control circuit 11. Further, if the charging completion display is unnecessary, the charging completion display unit may be omitted.

Below, a concrete example of the timer control circuit 13 and a timer function at the time of charging by the lithium ion battery charger using the timer control circuit will be described.

FIG. 2 is a circuit diagram showing a first specific example of the timer control circuit 13. In FIG. 2, the timer control circuit 13 includes a transistor Q1, capacitors C1 and C2, and resistors R1, R2 and R3. Transistors are used as switches, and if they act as switches (for example, relays),
Of course, it is not limited to transistors.

The transistor Q1 has a base connected to the control circuit 11 at the terminal a, an emitter connected to the capacitor C2, and a collector connected to the capacitor C1 at the node A. The capacitors C1 and C2 are connected to the resistors R1 and R2 at the node B. The resistor R2 is connected to the resistor R3 at the node C. The resistor R1 is a terminal g, the resistor R3 is a terminal f,
It is connected to the timer IC 15 of FIG. Node A is
The terminal h is connected to the timer IC 15 of FIG. 1 and is grounded. The node C has a terminal e at the timer IC 15 of FIG.
It is connected to the.

When the transistor Q1 is ON, the charge stop time (timer time) is 4 hours, and the transistor Q1 is OFF.
So that the timer time becomes 30 minutes when
The time constant is adjusted in advance by 1, C2 and resistors R1, R2, R3. Transistor Q1 is ON at the start of charging
Then, the timer time is set to 4 hours.

In advance, the charging current before the battery to be charged is fully charged (set charging current; generally one hundred to several hundred [mA]) i1
Is set. However, the battery to be charged when the set charging current i1 is detected is fully charged within the adjusted timer time of 30 minutes. The charging current is detected by the charging current detection circuit 7 of FIG. 1 and monitored by the control circuit 11 of FIG. Here, when the charging current reaches the set charging current i1, the control circuit 11 turns off the transistor Q1 and switches the timer time from 4 hours to 30 minutes. In other words, the setting for starting counting the total number of clocks in 4 hours is switched to the setting for counting in 30 minutes. If it takes 1 hour from the start of charging until the charging current reaches the set charging current i1, it is already 1 of the total number of clocks at that time.
/ 4 is being counted. When the remaining 3/4 clocks are set to count the total number of clocks in 30 minutes, the counting speed is 8 times as fast as when the timer time is set to 4 hours. Therefore, the remaining 3 hours are counted in 22.5 minutes.

When the fast-forwarding function of the timer time is used to charge (recharge) a charged battery having a relatively large remaining charge capacity, a simple timer function takes 4 hours until the charging is stopped (until the charging stop display is displayed). Wait for an hour 2
Charging stops in 2.5 minutes.

FIG. 3 shows charge characteristics when a battery having a large remaining charge capacity is charged using the lithium ion battery charger to which the first specific example of the timer control circuit 13 of FIG. 2 of the present invention is applied. FIG.

In FIG. 3, the horizontal axis represents charging time [H], and the vertical axis represents charging voltage [V] and charging current [I].
Represents 0 is the origin. The charge stop time T is the time during which an uncharged battery (empty battery) can be fully charged. The charge stop time t is a charge stop time that has been advanced by the timer time fast forward function of the present invention.

FIG. 4 is a circuit diagram showing a second specific example of the timer control circuit 13. In FIG. 4, the timer control circuit 13 includes transistors Q2 and Q3,
Capacitors C1, C3, C4 and resistors R1, R2, R3
And As in the case of the first specific example, the transistors Q2 and Q3 are not limited to the transistors as long as they function as switches.

The base of the transistor Q2 is the control circuit 1
1, the emitter is connected to the capacitor C3, and the collector is connected to the node A. The transistor Q3 has a base connected to the control circuit 11, an emitter connected to the capacitor C4, and a collector connected to the node A. Capacitor C3 is connected to capacitor C4 at node D. Node D is
It is connected to node E. The capacitor C1 is connected to the node A and is connected to the resistors R1 and R2 at the node E. The node A is connected to the timer IC 15 at the terminal h and is also grounded. The resistor R1 is connected to the timer control circuit 13 at the terminal g. Resistance R
2 is connected to the resistor R3 at the node C. Resistance R3
Is connected to the timer IC 15 at a terminal f. The node C is connected to the timer IC 15 at the terminal e.

When the transistors Q3 and Q4 are ON, the timer time is 4 hours, and when the transistor Q3 is OFF, 6
0 minutes, 30 minutes when the transistors Q3, Q4 are OFF, the resistors R1, R2, R3, the capacitor C1,
The time constant is adjusted in advance by C3 and C4. Also,
Set the charging voltage (set charging voltage) for switching from the constant current charging method to the constant voltage charging method.

In the constant current charging area after the start of charging, up to the set charging voltage that can be switched to the constant voltage charging method,
The transistor Q3 is turned off, the timer time is set to 60 minutes, and is used as the protection timer time. This protection timer time prevents an abnormally large current from continuing to flow to the battery to be charged for a long time. If it takes 30 minutes from the start of charging until the charging voltage reaches the set charging voltage, the timer IC 15 in FIG.
/ 2 is counted, and the transistor Q3 is turned on from the remaining 1/2 number of clocks (transistor Q4 becomes O
Remains N), the timer time is set to 4 hours and the clock is counted. Thereafter, as in the case of the first specific example, when the set charging current i1 is detected, the transistor Q4 is turned off, the timer time is switched from 4 hours to 30 minutes, and the timer time is fast-forwarded. Be done.

Therefore, the timer control circuit 13 of the second specific example has the function of fast-forwarding the timer time when the timer control circuit 13 of the first specific example is used, and the charged battery is charged after the start of charging. While the capacity is small, it is possible to efficiently charge by the constant current charging method, and it is possible to add the protection timer function in the constant current charging area after the start of charging as described above.

FIG. 5 is a diagram showing charge characteristics when a battery having a small remaining charge capacity is charged using the lithium ion battery charger to which the second specific example of the timer control circuit 13 is applied. When the voltage reaches the set charging voltage, it is assumed that the battery has the same charge remaining capacity as in the case of the first specific example.

In FIG. 5, the horizontal axis represents charging time [H] and the vertical axis represents charging voltage [V] and charging current [I].
Represents 0 is the origin. The charge stop time T is a time during which an uncharged battery (empty battery) can be fully charged. The charge stop time t is a charge stop time that has been advanced by the timer time fast forward function of the present invention. i1 is the set charging current. v1 is a set charging voltage.

In the circuit diagram of the first specific example shown in FIG. 2 and the circuit diagram of the second specific example shown in FIG. 4, the elements constituting the circuit are elements for which the time constant of the timer IC 15 of FIG. 1 can be determined. If it is, it is not limited to the three types of switch, capacitor, and resistor. Further, the number of the elements is not limited to this as long as the control circuit 11 of FIG. 1 does not need an arithmetic circuit such as a microcomputer for the control.

[0043]

As described above, according to the present invention, the charge remaining capacity of the battery to be charged before it is fully charged is preset, and the battery to be charged is charged for a predetermined time from the time when the charge remaining capacity is detected. Is charged, the charging is quickly stopped when the battery to be charged is fully charged without using an arithmetic circuit such as a microcomputer.

As a result, it is possible to obtain a compact, lightweight, and cost-effective lithium-ion battery charger that does not depend on the remaining charge capacity of the battery to be charged and waits for a long time before stopping charging.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a lithium ion battery charger according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a first specific example of the timer control circuit 13 of the embodiment of the lithium-ion battery charger of the present invention.

FIG. 3 is a diagram showing charge characteristics when the battery is charged by the lithium ion battery charger using the timer control circuit 13 of the first specific example of the present invention.

FIG. 4 is a circuit diagram showing a second specific example of the timer control circuit 13 of the embodiment of the lithium-ion battery charger of the present invention.

FIG. 5 is a diagram showing charge characteristics when the battery is charged by a lithium ion battery charger using the timer control circuit 13 of the second specific example of the present invention.

FIG. 6 is a diagram showing charging characteristics when the battery is charged by a conventional lithium-ion battery charger.

[Explanation of symbols]

 1 power supply circuit 3 power conversion circuit 5 output circuit 6 battery to be charged 7 charging current detection circuit 9 charging voltage detection circuit 11 control circuit 13 timer control circuit 15 timer IC i1 set charging current v1 set charging voltage t charging stop time

Claims (2)

[Claims] 1. A setting means for presetting a remaining charge capacity of the charged battery before the charged battery is fully charged, a detecting means for detecting the remaining charge capacity set by the setting means, A charger for a lithium ion battery, comprising: a charging unit that charges the battery to be charged for a predetermined time from the time when the remaining charge capacity is detected by the detection unit. 2. When the charge remaining capacity is detected,
The lithium-ion battery charger according to claim 1, further comprising control means for controlling the predetermined time.