JPH05122860A - Charging circuit for secondary cell - Google Patents

Abstract

PURPOSE:To prevent overcharging of a secondary cell when an apparatus having a mounted secondary cell is connected through a connector. CONSTITUTION:A charging circuit 23 controls to charge a secondary cell 1 through a constant-current circuit 11 by the cell 1 used by connecting and disconnecting the circuit 23 of the cell 1 to and from an apparatus having the mounted cell 1 through connectors 9a, 9b, 9c, a charge starting voltage detector 13 of the cell 1 and a fully-charged state detector 12. The connection of the connector 9c is detected by a ground signal from a contact (e), detected by a differentiator of resistors R1, R12, a capacitor C1 and a level converter 15, and a charging time is so suppressed that the cell 1 is not overcharged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging circuit for a secondary battery, and more particularly to a charging circuit for a secondary battery of a device in which the charging circuit and a device equipped with the secondary battery can be separated and used via a connector. ..

[0002]

2. Description of the Related Art Conventionally, this type of secondary battery charging circuit is
As shown in FIG. 3, when the secondary battery 1 is attached to an electronic device, that is, when the disconnection state is changed to the contact state, it is detected that the disconnection state is changed to the contact state. It does not have a function to perform processing related to charging the secondary battery 1,
Charging was performed based on the result of simply measuring the voltage of the secondary battery 1.

[0003]

This conventional rechargeable battery charging circuit, as shown in FIG. 3, when the rechargeable battery 1 is attached to an electronic device, that is, when the rechargeable battery is switched from a disconnected state to a contact state, Based on the result of simply measuring the voltage of the secondary battery 1 without the function of detecting the change from the disconnected state to the contact state and performing the process related to the charging of the secondary battery 1 corresponding to the change of this state. Since the rechargeable battery is configured to be charged, the rechargeable battery is overcharged too much, and when it is overcharged, there is a problem that the electrolyte separation of the rechargeable battery is increased and the life of the rechargeable battery is shortened.

For this reason, in order to extend the life of the secondary battery and increase the reliability, the charging circuit is designed so that the transient charging that occurs when the connector between the charging circuit and the secondary battery is joined is not overcharged. Had to reduce the charging time.

[0005]

The charging circuit for a secondary battery according to the present invention has a gate means for charging the secondary battery and stopping the charging, and the voltage of the secondary battery has reached a predetermined voltage. From the constant current circuit after a preset time delay operation by means of a full charge state detection means for detecting that the full charge state is detected, and a delay circuit for fully charging after detecting the full charge state and preventing overcharging. In a charging circuit of a secondary battery having a function of turning off the gate means for stopping charging of a battery, a connector for connecting or disconnecting the charging circuit and the secondary battery, and the connector is A connection detection unit that detects that the disconnection state with the secondary battery is switched to a connection state, and after the delay time due to the detection of the connection state, collates with the output of the full charge state detection unit, and is in a fully charged state. If the delay times And a delay operation stopping means for forcibly setting the time delay operation of the power supply, and the connection detecting means detects that the power supply to the charging circuit has risen from an off state to an on state. Includes detection means.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a case where a power source having a charging circuit according to the present embodiment and an electronic device with a built-in secondary battery are joined through a connector. It is a figure.

Generally, a secondary battery such as a lithium battery is a method of converting electric energy into chemical energy at the time of charging and storing it. Conversely, a secondary battery is used by converting chemical energy into electric energy at the time of discharging.

Gas and heat generated from the electrolyte of the secondary battery are generated by the energy conversion performed during the charge and discharge. As the charge and discharge are repeated, the charge and discharge capacity of the secondary battery decreases, and the secondary battery reaches the end of its life.

That is, repeated rapid charging / discharging or overcharging may shorten the life of the secondary battery. Therefore, in order to extend the life of the secondary battery, it is only necessary to take measures against the above-mentioned factors that shorten the life.

Next, the structure of this embodiment will be described.

Referring to FIG. 1, the charging circuit 23 of the present embodiment.
Is a constant current circuit 11 including a charge control circuit 22 that receives the DC voltage from the voltage conversion circuit 2 and repeatedly charges the secondary battery 1 for charging and stops charging, and the resistance of the secondary battery 1. A full charge state detection circuit 12 for detecting the full charge state of the secondary battery 1 and a charge start voltage for detecting the charge start voltage of the secondary battery 1 by comparison with the reference voltage P20 by the voltage division by R1, R2, R3. An S-R flip-flop (hereinafter referred to as S-RF / F) 14 which is set by the output signal of the detection circuit 13, the full charge state detection circuit 12, and is reset by the output signal of the charge start detection circuit 13, and an S-RF / F.
When the set output signal of 14 is input, the output signal delayed by a preset period is output and the inverter (hereinafter referred to as IN
V) 15, the delay circuit 15 that controls the charging control circuit 22 to stop charging, and the charging circuit 2 of this embodiment.
3 is connected to the other device by the connector 9C, detects the ground through the connector 9C, and generates a differential signal.
R12 and capacitor C1, level conversion circuit 16 for converting the level of the differential signal, R-SF / F17 set by the output signal of level conversion circuit 16, and R-SF / F1
The delay circuit 18 that outputs a delay signal for a predetermined period according to the set output signal of 7 and the delay circuit 15 that outputs the output signal of the delay circuit 18 when the secondary battery 1 is fully charged.
It has a one-shot monostable (hereinafter referred to as MS) 19 for outputting a signal for terminating the delay operation of.

In FIG. 1, in the charging circuit 23 of the secondary battery 1 of the present embodiment, in order to suppress the charging time at the time of joining the connectors 9a, 9b, 9c, first, the connectors 9a, 9b,
The change in the junction of 9c is detected. After a predetermined time elapses after the detection of this junction, the charging is stopped when the voltage of the secondary battery 1 is in the fully charged state, and otherwise the normal charging is continued.

Next, the operation of this embodiment will be described with reference to FIGS.

Electronic circuit 4 in which the voltage of the secondary battery 1 is a load
When the charging start voltage detection circuit 13 detects the charging start voltage, which is a low level voltage at which the electronic device 6 with a built-in secondary battery operates, by comparison with the reference voltage P20, S-RF / F1
4 is reset and the delay circuit 15 is reset. At this time, the output of the delay circuit 15 turns on the gate of the charge control circuit 22 of the constant current circuit 11 via the INV 25 and turns on the gate TR1 to start the charging of the secondary battery 1 while performing the constant current control.

When the voltage of the secondary battery 1 further rises due to charging and reaches the fully charged state, the fully charged state detection circuit 12 detects this and sets S-RF / F14. At this time, the output of the charge start voltage detection circuit 13 is off, the output Q of the S-RF / F 14 becomes "1", and the delay operation of the delay circuit 15 is started.

After the lapse of the set time of the delay circuit 15, that is, after the time when the secondary battery 1 is sufficiently charged, the delay circuit 1
The output of 5 turns off the gate of the charge control circuit 22 of the constant current circuit 11 via the INV 25 and closes the gate TR1 to stop the charging of the secondary battery 1.

In the detection of the voltage at which charging is started by the charging start voltage detection circuit 13 described above, the charging circuit 23 of this embodiment once charges the battery sufficiently until it reaches the charging start voltage by discharging. Although the charging is not started, when the power supply 5 including the charging circuit 23 and the electronic device 6 with a built-in secondary battery are switched from the "disconnected" state to the "contact" state by the connectors 9a, 9b, 9c, the secondary The circuit for measuring the voltage of the battery 1 is temporarily charged with the charging start voltage detection circuit 1 due to the transient state.
3 works, the secondary battery 1 through TR1 of the constant current circuit 1
Start charging.

At this time, when the voltage of the secondary battery 1 is fully charged and fully charged, the charging is further performed for the set delay time of the delay circuit 15, and the secondary battery 1 is overcharged. It will be charged.

Therefore, when the splicer 9c is spliced to the secondary battery built-in electronic device 6, the contact e of the splicer 9c causes the charging circuit 23 to receive a ground signal, and the resistors R11, R12,
After the ground is detected by the differentiating circuit including the capacitor C1 and the level converting circuit 16 and S-RF / F17 is set, the secondary battery 1 is fully charged after a delay of several seconds set in advance by the delay circuit 18. It is confirmed by the output of the fully charged state detection circuit 12 that the delay circuit 15 is set so as to end the delay operation of the delay circuit 15.

Due to this setting for the delay circuit 15, the output of the delay circuit 15 is passed through the INV 25 and the constant current circuit 11
Turn off the gate of the charging control circuit 22 of the gate TR1
Is turned off to stop charging the secondary battery 1.

By the above-described junction detecting operation in the connector 9c and the subsequent processing, overcharge of the secondary battery 1 can be prevented, the life of the secondary battery 1 can be extended, and the reliability can be enhanced.

Similarly, when the supply of the input power source AC100V of the power source 5 is turned on from off, the resistor R1
0, R11, R12, the capacitor C1 and the level converting circuit 16 are used as an integrating circuit to input the rise of the power source 5 to the S-RF / F17 as a pulse corresponding to the charging time of the capacitor C1 and set it. Similarly, overcharge of the secondary battery 1 can be prevented.

[0024]

As described above, the present invention detects the junction of the connector by detecting the overcharge to the secondary battery which occurs when the charging circuit by the connector and the device having the secondary battery are attached and detached. Since the charging time can be prevented by suppressing the charging time, the life of the secondary battery can be extended and the reliability can be enhanced.

Similarly, even when the power is turned on, by stopping the charging for a preset delay time by the delay circuit after detecting the full charge state, it is possible to prevent overcharge of the secondary battery. ..

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a case where a power source having a built-in charging circuit of the present embodiment and an electronic device with a built-in secondary battery are joined via a connector.

FIG. 3 is a block diagram showing an example of a conventional charging circuit for a secondary battery.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Secondary battery 2 Voltage conversion circuit 3,23 Charging circuit 4 Electronic circuit 5 Power supply 6 Electronic device with built-in secondary battery 7 Ground 9a, 9b, 9c, 9d, 9e Connector 11 Constant current circuit 12 Full charge state detection circuit 13 Charge start voltage detection circuit 14,17 SR flip-flop (S-RF /
F) 15,18 Delay circuit 16 Level conversion circuit 19 One-shot monostable (MS) 20 Reference voltage (P) 21 Charging current control reference voltage 22 Charging control circuit 23 NAND circuit (NAND) 24 AND circuit (AND) 25 Inverter circuit (INV)

Claims (2)

[Claims] 1. A gate means for charging and stopping charging of a secondary battery, a fully charged state detecting means for detecting that the voltage of the secondary battery has reached a predetermined voltage, and a fully charged state detection. After that, the gate means for stopping the charging of the secondary battery from the constant current circuit is turned off after the preset time delay operation by the delay circuit for sufficiently charging and preventing overcharging. In a charging circuit for a secondary battery having a function, a connecting device that connects or disconnects the charging circuit and the secondary battery, and the connecting device has switched from a disconnection state to a contact state with the secondary battery. After the delay time due to the detection of the connection state and the connection state detecting means, the output of the full charge state detection means is collated, and in the case of the full charge state, the time delay operation of the delay circuit is forced. Delayed motion to set completion A charging circuit for a secondary battery, comprising: a stop device. 2. The secondary battery according to claim 1, wherein the connection detecting means includes a power supply rise detecting means for detecting that the power supplied to the charging circuit rises from an off state to an on state. Charging circuit.