JPH08308134A - Device and method for charging lithium ion battery - Google Patents

Abstract

PURPOSE: To provide a device and method for charging a lithium ion battery by using an adapter used for the nickel-cadmium battery, nickel-hydrogen battery, etc. CONSTITUTION: A lithium ion battery charging device is provided with a voltage detecting circuit 8 which detects the voltage of a lithium ion battery and control circuit 10 which controls the charging of the battery to intermittent charging after the circuit 8 detects a prescribed voltage during the course of charging. At the time of performing intermittent charging, the control circuit 10 charges the battery when the voltage of the battery is higher than a prescribed value and, at the same time, stops the charging when a voltage lower than the prescribe value is detected and, moreover, detects the voltage of the battery a prescribed period after the charging is stopped and, when the charging stopping time reaches a preset value, terminates the charging.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In recent years, along with the miniaturization and weight reduction of portable information devices, miniaturization of secondary batteries and reduction of mass have become issues. Under such circumstances, nickel-cadmium ( Ni-Cd) battery, nickel hydrogen (Ni-M)
The lithium (Li) ion battery, which can reduce the size by about half and the mass by 20 to 40% compared to the H) battery, has been attracting attention.

[0003]

However, in order to prevent heat generation due to overcharge or overcurrent, this lithium ion battery is charged with a constant voltage constant current method with an accuracy of 1% with respect to the full charge voltage. , It was necessary to converge to the full charge voltage.

Therefore, the AC adapter needs to be designed differently from those of the nickel-cadmium battery and the nickel-hydrogen battery, which do not require the above-mentioned accuracy, and cannot be used for charging these batteries.

[0005]

In view of the above points, a lithium ion battery charging device of the present invention has a voltage detecting means for detecting a battery voltage of a lithium ion battery, and a detecting means for detecting a predetermined voltage during charging. After detecting, it has a control means for intermittently charging the lithium-ion battery, and the control means, in the intermittent charging process, charge at a predetermined voltage or more, and charge based on the detection of less than the predetermined voltage. Then, the battery voltage after the charging is stopped is detected after a predetermined time, and the charging is ended when the charging stop time reaches a predetermined time.

The lithium ion battery charging method of the present invention is a lithium ion battery charging method in which the lithium ion battery is intermittently charged after the battery voltage of the lithium ion battery reaches a predetermined voltage. Along with charging when the voltage is higher than or equal to, the charging is stopped based on the detection of a voltage lower than a predetermined voltage, and the detection of the battery voltage after the stop of the charging is performed after a predetermined time, and when the charge stop time reaches a predetermined time, It is designed to end charging.

[0007]

Since the present invention is configured as described above, it is determined that the battery is fully charged when charging is performed by a so-called pulse charging method and the charging stop period is a predetermined time or more. is there.

[0008]

Embodiments of the present invention will be described with reference to the drawings.

In the block diagram of FIG. 1, (1) is a so-called notebook type personal computer, which has a power supply section (2) for supplying power to each circuit. (3)
Is an AC adapter that converts commercial power to DC power,
(4) is a battery pack having a lithium-ion battery (5), a battery voltage detection circuit (8) consisting of a resistance voltage dividing circuit (6) and an A / D conversion circuit (7), and the fact that it has reached full charge. It has an LED lamp (9) for notifying and a control circuit (10) composed of a microcomputer.

The AC adapter (3) and the battery pack (4) are connected to the personal computer (1) via the connectors (11) and (12).

The AC adapter (3) has a DC power supply terminal (DC), a charging terminal (CHG), a control input terminal (EN) for controlling the start and stop of charging, and a control circuit (4). Receives power from the DC power supply terminal (DC) of the AC adapter (3) and also provides a control signal to the control input terminal (EN) of the AC adapter (3).

Thus, in the above configuration, when only the battery pack (4) is connected to the personal computer (1), the power source section (2) of this personal computer (1) is connected to the lithium ion battery (5). Power supply of the personal computer (1) is selected and the AC adapter (3) is connected in this state.
Will select the power supply from the DC power supply terminal (DC) of the AC adapter (3). At this time, since the control circuit (10) is also supplied with power and the charging voltage is applied to the lithium ion battery (5), charging of the lithium ion battery (5) is started.

The method of charging the lithium ion battery (5) will be described below with reference to FIG.

First, when power is supplied, the control circuit (10) activates the timer 1 for measuring the charging processing time (S1). Then, an H level signal is applied to the control input terminal (EN) of the AC adapter (3) to start charging (S
2) It is monitored whether or not the battery voltage has reached 12.3 V or higher (S3). Here, the reason why the voltage is set to 12.3 V is that the full-charge voltage of the lithium ion battery is 4.1 V and three lithium ion batteries are connected in series. When it reaches 12.3V,
Proceeding to step S4, the timer 2 for timing the next voltage detection timing is activated. Next, after waiting for 5 to 15 ms, an L level signal is given to the control input terminal (EN) of the AC adapter (3) to stop charging (S5, 6). Here, the waiting time is provided because if charging is stopped immediately after reaching 12.3V, it takes a long time to complete charging, so there is a margin for the time of overcharging. This is to extend the charging within the time taken into consideration and shorten the charging completion time. By the way, this waiting time is
A control circuit (10) corresponding to the time measured by the timer 1 in advance.
It is defined in the internal ROM, and the time is selected according to this definition. The standby time is set to increase as the time measured by the timer 1 increases. That is, at the beginning of charging, the ON time of the switching FET in the AC adapter (3) that controls the start and stop of charging is long and the temperature thereof is high, so the waiting time is shortened, and when the charging is almost completed, Since the ON time of the FET is shortened and it is not necessary to consider the temperature rise, the waiting time is set to be long.

After the charging is stopped, the process proceeds to step S7, the timer 3 for measuring the charging stop time is activated, and then it is determined whether or not the timer 2 measures 16 ms (S).
8). When the timer 2 measures 16 ms, step S
9, the timer 2 is reset and the timer is restarted (restart), and it is determined in step S10 whether the battery voltage is 12.3 V or higher. At this timing, if the battery voltage is less than 12.3 V, the control input terminal (EN) of the AC adapter (3) is again given an H level signal to start charging, and the timer 3 is reset, so that the battery voltage becomes It is monitored whether or not the voltage has reached 12.3 V or higher (S1
1-13). If it is determined to be 12.3 V or higher, the process returns to step S5 described above. When the process of steps S5 to S13 progresses and the lithium-ion battery (5) approaches full charge, the battery voltage becomes longer than 12.3 V, so that the interval is 16 ms as described above. When the battery voltage is determined, the rate of being 12.3 V or higher at the time of the determination increases, and as a result, the charging stop time becomes longer.
According to experimental data, this charging stop time is 320ms
Then, since it is fully charged, if it is determined in step S10 that the voltage is 12.3 V or higher, it is determined in step S14 whether or not the timer S3 has clocked 320 ms, and if 320 ms is clocked. In step S15, the LED lamp (9) is turned on to notify the completion of charging.

[0016]

As described above, according to the present invention, the battery is charged by the so-called pulse charging method, and when the charging stop period becomes a predetermined time or more, it is determined that the battery is fully charged. Since it does not need to supply a highly accurate constant voltage, it can also be used as an AC adapter for nickel-cadmium batteries, nickel-hydrogen batteries, etc., and it can detect full charge without detecting the charging current, so its detection circuit , A
The / D conversion circuit and the like are unnecessary, and the circuit can be simplified.

[Brief description of drawings]

FIG. 1 is a block diagram using a battery pack of the present invention.

FIG. 2 is a flowchart of a program of a main part relating to a charging process written in a control circuit of the present invention.

[Explanation of symbols]

 1 Personal Computer 3 AC Adapter 4 Battery Pack 5 Lithium Ion Battery 8 Battery Voltage Detection Circuit 10 Control Circuit

Claims (2)

[Claims] 1. A device having voltage detection means for detecting a battery voltage of a lithium ion battery, and control means for intermittently charging the lithium ion battery after the detection means detects a predetermined voltage during charging. In the intermittent charging process, the control means performs charging when the voltage is equal to or higher than a predetermined voltage, stops charging based on detection of a voltage lower than the predetermined voltage, and detects the battery voltage after stopping the charging after a predetermined time. , When the charge stop time reaches a predetermined time,
A charging device for a lithium-ion battery, which is characterized by ending charging. 2. A method of charging a lithium ion battery, wherein the lithium ion battery is intermittently charged after the battery voltage of the lithium ion battery reaches a predetermined voltage,
When charging is performed when the voltage is equal to or higher than a predetermined voltage, the charging is stopped based on the detection of the voltage lower than the predetermined voltage, and the battery voltage after the stop of the charging is detected after a predetermined time, and when the charge stop time reaches a predetermined time. A method for charging a lithium-ion battery, characterized by terminating charging.