JPH104634A - Method for charging secondary battery, and charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To pulse-charge a secondary battery without malfunction. SOLUTION: This is a charging method to pulse-charge a secondary battery 11, using a charging circuit which charges a secondary batter 11 with constant voltage and controls the charge when the charging current becomes smaller than the threshold value, and in this method, the magnitude of the charging current is made larger than the threshold value by bypassing the charging current at the time of interruption of charge during pulse charge period of the secondary battery 11, and after detection of full charge of the secondary battery 11, the magnitude of the charging current is made smaller than the threshold value by bypassing the charging current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging method and a charging apparatus for charging a rechargeable battery in a pulsed manner by using a charging circuit for charging the rechargeable battery at a constant voltage and controlling the charging when the charging current becomes smaller than a threshold value. About.

[0002]

2. Description of the Related Art As one of non-aqueous secondary batteries that can be repeatedly charged and discharged, a small and high-capacity lithium-ion secondary battery has attracted attention. Such a battery charger for a secondary battery is configured to charge the secondary battery at a constant voltage, and to control the charging when the charging current falls below a certain threshold (see, for example,
-192670).

On the other hand, a technique for rapidly charging a lithium ion secondary battery is disclosed in Japanese Patent Application Laid-Open No. 7-183051. The contents disclosed in this publication are for pulse charging of a secondary battery. For example, the output voltage of a charging power supply is set to be higher than the full charge voltage of the secondary battery, and the battery voltage of the secondary battery becomes full. Charging for a predetermined time after reaching the charging voltage,
The secondary battery is pulse-charged while repeatedly interrupting charging until the battery voltage falls below the full charge voltage.

[0004]

By the way, when the secondary battery is pulse-charged by using a charger for controlling the charging when the charging current falls below a certain threshold value, the battery voltage becomes full charge voltage. The charging of the secondary battery is interrupted until the value falls below 0, and the charging current becomes zero. Therefore, the charger
Since this is erroneously detected as being fully charged and charging is controlled, there has been a problem that pulse charging as described above cannot be performed normally.

Therefore, the present invention solves such a problem,
A charging circuit for charging a secondary battery at a constant voltage and controlling the charging when the charging current becomes smaller than a threshold value enables a normal pulse charging of the secondary battery.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a charging method for charging a rechargeable battery in a pulsed manner by using a charging circuit for charging the rechargeable battery at a constant voltage and controlling the charging when the charging current becomes smaller than a threshold value. When charging is suspended during the pulse charging period of the secondary battery, the charging current is bypassed to make the magnitude of the charging current larger than the threshold, and after the secondary battery is fully charged, the charging current is reduced. The magnitude of the charging current is made smaller than the threshold value by bypassing.

Further, the present invention relates to a charging device for charging a secondary battery in a pulsed manner by using a charging circuit for charging the secondary battery at a constant voltage and controlling the charging when the charging current becomes smaller than a threshold value. A pulse charge control unit that controls pulse charge of the secondary battery, a full charge detection unit that detects full charge of the secondary battery, and is connected in parallel with the secondary battery and bypasses a charge current from the charging circuit. A detour circuit unit that, when charging is interrupted during the pulse charging period of the secondary battery, diverts the charging current to make the magnitude of the charging current larger than the threshold value, After detecting the full charge of the battery, the charge current is bypassed to make the magnitude of the charge current smaller than the threshold value.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram schematically showing a charging apparatus according to the present invention. The charging circuit includes a constant voltage / constant current power supply unit 1 for outputting a constant voltage of 4.20 V and a predetermined constant current.
A charge control switch unit 2 for controlling on / off of a charge current to a battery pack P detachably attached to a charging circuit;
A current detector 3 for detecting a charging current flowing in the charging circuit;
When the charging current becomes equal to or smaller than the threshold value Io, the charging control unit 4 controls charging of the battery pack P.

Here, the charge control by the charge control unit 4 means that the charge control switch unit 2 is turned off immediately after the charging current becomes equal to or less than the threshold value Io or after a predetermined time elapses.
Or, it indicates that the battery is fully charged.

FIG. 2 is a circuit diagram showing details of the battery pack P in FIG. The battery pack has a pair of charge / discharge terminals T
1 and T2, and a lithium ion secondary battery (hereinafter referred to as a secondary battery) 11 and M are provided between the terminals T1 and T2.
A pulse charge switch Q1 composed of an OSFET is connected in series. Note that a parasitic diode D is connected in parallel to the pulse charging switch Q1.

The pulse charge control unit 12 detects the battery voltage of the secondary battery 11, and when the battery voltage reaches 4.10V,
After the elapse of the time Ta of the time constant determined by the capacitor C1, a low-level signal is output from the output terminal OUT to turn off the pulse charging switch Q1. When a low level signal is output from the output terminal OUT, the transistors Q2 and Q3 are turned on, and as a result, the pulse charging switch Q1 is turned off, and the charging of the secondary battery B is interrupted.

When the battery voltage of the secondary battery 11 falls below 4.10 V, the pulse charge control unit 12 immediately outputs a high-level signal from the output terminal OUT to turn off the transistors Q2 and Q3. As a result, the pulse charging switch Q1 is turned on, and charging of the secondary battery B is restarted.

As described above, the pulse charge control unit 12
The secondary battery 11 is pulse-charged while repeatedly charging for a predetermined time Ta after the battery voltage of the secondary battery 11 reaches 4.10 V and suspending charging until the battery voltage falls below 4.10 V.

The full charge detection circuit unit 13 detects that the time during which the charging of the secondary battery 11 has been interrupted by the pulse charge control unit 12 has become equal to or longer than a predetermined time Tb. Is detected. That is, when the rechargeable battery 11 is being charged, the voltage of the gate of the pulse charge switch Q1 is at a high level, so that the transistor Q4 is in the ON state and the capacitor C2 is in the discharged state. Therefore, the transistors Q5 and Q6 maintain the off state.

On the other hand, when charging of the secondary battery 11 is interrupted,
Since the voltage at the gate of the pulse charging switch Q1 is at a low level, the transistor Q4 is turned off and the capacitor C2 is charged. When the charging time becomes equal to or longer than the predetermined time Tb, the transistors Q5 and Q6 are turned on by the charging voltage of the capacitor C2, and a high-level full charge signal is output. By this full charge signal,
The transistor Q3 is turned on, the pulse charging switch Q1 is turned off, and the charging of the secondary battery 11 is cut off. Thereafter, this state is continued.

If the interruption time of the charging of the secondary battery 11 does not exceed the predetermined time Tb (that is, if the charging of the secondary battery 11 is restarted within the predetermined time Tb), the transistor Q5 is turned on. Previously, the transistor Q4 is turned on to discharge the capacitor C2, so that the transistor Q6 does not output a full charge signal.

As described above, the full charge detection circuit 13 detects the interruption time in the pulse charging of the secondary battery 11, and outputs a full charge signal when the interruption time exceeds a predetermined time Tb.

The current bypass circuit section 14 includes a charge / discharge terminal T1,
A first bypass circuit 14A that is connected between T2 and bypasses the charging current at the time of charging interruption during the pulse charging of the secondary battery 11 and a second bypass circuit that bypasses the charging current after the secondary battery 11 is detected to be fully charged. And a bypass circuit 14B.

The first bypass circuit 14A includes a transistor Q7 that is kept on until a full charge of the secondary battery 11 is detected, and a charge current for the charge control unit 4 (see FIG. 1) to control the charge. When the first limiting resistor R1 for limiting the charging current to the first set value Ia slightly higher than the threshold value Io, and when the pulse charging control unit 12 interrupts the charging of the secondary battery 11 (that is, the transistor Q2 is turned on) The transistor Q8 which is turned on is connected in series.

On the other hand, the second detour circuit 14B includes a second limiter for limiting the charging current to a second set value Ib slightly lower than the charging current threshold Io for the charging controller 4 (see FIG. 1) to control charging. The resistor R2 and the full charge detection circuit 13
Transistor Q that turns on when full charge of 1 is detected
9 in series.

The above-described current bypass circuit section 14 operates as follows. During the pulse charging period of the secondary battery 11, while the secondary battery 11 is being charged, the transistor Q8 is also in the off state because the transistor Q2 is in the off state.
Therefore, the charging current does not flow through the first bypass circuit 14A.

When the charging of the secondary battery 11 is interrupted, the transistor Q8 is turned on, and the charging current flowing through the secondary battery 11 flows through the first bypass circuit 14A. The charging current at this time is set to the first set value Ia by the first limiting resistor R1.
Becomes

When the full charge of the secondary battery 11 is detected, the transistor Q6 is turned on, so that the first bypass circuit 1
4A, the transistor Q7 is turned off, and the bypass operation of the charging current is stopped. On the other hand, since the transistor Q9 of the second bypass circuit 14B is turned on, the charging current flows through the second bypass circuit 14B, and its magnitude becomes the second set value Ib by the second limiting resistor R2.

Further, in the circuit shown in FIG. 2, a charger off detecting section 15 is connected in parallel with the pulse charge switch Q1. The charger off detection section 15 is constituted by a comparator, and detects the presence or absence of a current in the parasitic diode D of the pulse charging switch Q1, thereby detecting that the battery pack P has been removed. After such detection,
The charger off detection unit 15 outputs a high-level signal to output the transistor Q1 connected in parallel to the capacitor C2.
0 is turned on to discharge the capacitor C2.

The operation of the present invention will now be described with reference to FIGS.
This will be described with reference to the waveform diagram of FIG. The charging of the secondary battery B is performed by connecting the charging / discharging terminals T1 and T2 of the battery pack P to a charging circuit, and the charging control unit 4 turning on the charging control switch unit 2. That is, the charging of the secondary battery 11 is pulse-charged under the control of the pulse charging control unit 12. Specifically, the pulse charge control unit 12 controls the rechargeable battery 1
The pulse charging of the secondary battery 11 is performed while repeatedly charging the battery 1 for a predetermined time Ta after the battery voltage reaches 4.10 V and suspending the charging until the battery voltage falls below 4.10 V (see FIG. 3 and FIG. 3). (See FIG. 4).

In this pulse charging period, when the pulse charging switch Q1 is turned off, the charging current flowing through the secondary battery 11 becomes 0 (see FIG. 4), but the charging current becomes the first.
It flows bypassing the bypass circuit 14A, and its value becomes the first set value Ia which is larger than the above-mentioned threshold value Io (see FIG. 5). Since the current detection unit 3 detects the charging current of the first set value Ia, even if the pulse charging switch Q1 is turned off during the pulse charging period of the secondary battery 11, the charging control unit 4 controls the charging control. No charge control such as turning off the switch unit 2 is performed.

Thereafter, the full charge detection circuit 13
When the full charge of 1 is detected, the pulse charge switch Q1 is turned off, and this state is maintained thereafter. At the same time, the second bypass circuit 14B operates, and the magnitude of the charging current becomes the second set value Ib smaller than the threshold value Io (see FIG. 5). Therefore, by detecting the second set value Ib, the current detection unit 3 detects the full charge of the secondary battery 11 and performs charge control such as turning off the charge control switch unit 2. Do.

When the battery pack P is removed from the charging circuit after the full charge of the secondary battery 11 is detected,
A current flows from the secondary battery 11 via the second bypass circuit 14B and the parasitic diode D. The charger off detection unit 15 detects the presence of this current, turns on the transistor Q10 connected in parallel with the capacitor C2, and discharges the capacitor C2. Accordingly, the full charge detection circuit 13 is reset, and the pulse charge switch Q1 returns to the on state.

[0029]

According to the present invention, there is provided a charging method for charging a rechargeable battery in a pulsed manner by using a charging circuit for charging the rechargeable battery at a constant voltage and controlling the charging when the charging current becomes smaller than a threshold value. When charging is interrupted during the pulse charging period of the secondary battery, the charging current is bypassed to make the magnitude of the charging current larger than the threshold, and after the secondary battery is fully charged, the charging current is bypassed. As a result, the magnitude of the charging current is made smaller than the threshold value, so that the secondary battery can be pulse-charged without malfunction.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram showing one embodiment of the present invention.

FIG. 3 is a waveform diagram showing a change in battery voltage according to the present invention.

FIG. 4 is a waveform diagram showing a change in a charging current of a secondary battery according to the present invention.

FIG. 5 is a waveform diagram showing a change in current of the charging circuit according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Constant voltage constant current power supply part 2 Charge control switch part 3 Current detection part 4 Charge control part 11 Secondary battery 12 Pulse charge control part 13 Full charge detection part 14 Current bypass circuit part

Claims (2)

[Claims] 1. A charging circuit for charging a secondary battery at a constant voltage and controlling charging when a charging current is smaller than a threshold value,
A charging method for pulse charging the secondary battery, wherein when charging is interrupted during a pulse charging period of the secondary battery, the charging current is bypassed to make the magnitude of the charging current larger than the threshold, and A method of charging a secondary battery, comprising, after detecting a full charge of a battery, diverting the charge current to make the magnitude of the charge current smaller than the threshold value. 2. A charging circuit that charges a secondary battery at a constant voltage and controls charging when a charging current is smaller than a threshold value.
A charging device that performs pulse charging of the secondary battery, and a pulse charging control unit that controls pulse charging of the secondary battery,
A full charge detection unit that detects full charge of the secondary battery, and a current bypass circuit unit that is connected in parallel with the secondary battery and bypasses a charging current from the charging circuit, and the bypass circuit unit includes: When the charging is interrupted during the pulse charging period of the secondary battery, the charging current is bypassed to make the magnitude of the charging current larger than the threshold, and after the secondary battery is fully charged, the charging current is bypassed. A charging device, wherein the magnitude of the charging current is smaller than the threshold value.