JPH10290531A - Battery pack and charger for battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of terminals and realize a more compact, low- cost battery charger and battery pack by performing charging control for all battery packs only by two positive and negative terminals. SOLUTION: For the detection of battery voltage during pulse charging, the battery voltage is detected when charging is not operated for avoiding a voltage drop due to a protection circuit 2 or the like during charging current output. By doing this, an accurate battery voltage can be detected without being affected by the voltage effect by a protection circuit 2 or the like. And if the battery voltage exceeds a normal voltage, then the secondary battery 1 is judged to be fully charged and the charging is completed. Also, if the battery voltage has not reached the normal voltage, charging is performed for a certain period of time and this is repeated until the charging is completed beyond the normal voltage. Then, even after the completion of charging, the presence or absence of battery and the detection of battery voltage are continued by a voltage detection circuit 7 and a connection judging circuit 8, and accurate charging control of the secondary battery 1 by two terminals can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery charger, and more particularly, to a battery charger that performs pulse charging by detecting connection of a battery pack and a battery voltage.

[0002]

2. Description of the Related Art Conventionally, a charging method using constant current control and constant voltage control has been used for a charger of a battery pack such as a mobile phone. A conventional battery pack charger will be described with reference to FIGS.

In FIG. 4, reference numeral 31 denotes a secondary battery such as a lithium battery; 32, a protection circuit for the secondary battery 31; 33, a backflow prevention circuit for preventing a backflow of current; and 34, a voltage of the secondary battery 31 to be charged. Voltage detection circuit in the battery pack for detecting
Reference numeral 5 denotes a battery voltage detection terminal for transmitting a voltage output from the battery pack internal voltage detection circuit 34 to the charger 37. The secondary battery 31 to the battery voltage detection terminal 35 are formed in the battery pack 36. I have.

Reference numeral 38 denotes a connection detection circuit for detecting that the battery pack 36 has been connected, 39 a voltage detection circuit for detecting the voltage of the secondary battery 31, 40 a constant current / constant voltage control circuit for controlling charging, and 41 Is a constant voltage power supply, and the connection detection circuit 38 to the constant current / constant voltage control circuit 40 are configured in the charger 37.

In this configuration, when the voltage of the secondary battery 31 is lower than a predetermined set value V3 when the pulse charging is started, as shown in a state A in FIG. Works to make the output current constant, and performs constant current charging.

When the constant current charging proceeds and the battery voltage eventually increases, and the voltage VB detected by the voltage detection circuit 39 reaches the control voltage V3 of the battery, the detection voltage VB is controlled so as not to exceed the set value V3. Shift to voltage charging. Therefore, the charging current decreases as shown in state B of FIG.

Here, the charging current Ic is constantly monitored and detected by the constant current / constant voltage control circuit 40.
When c becomes smaller than the threshold current I1 for stopping charging, charging is terminated.

[0008] Thereafter, the charger 37 continues to detect the presence or absence of connection with the battery pack 36 by the connection detection circuit 38 through the battery voltage detection terminal 35, and to detect the battery voltage of the secondary battery 31 by the voltage detection circuit 39. I have.

[0009]

However, in the above-described secondary battery charger, a battery voltage detection terminal is required for the battery pack in order to accurately detect the battery voltage. There is a problem that hinders cost reduction. Another problem is that an accurate voltage may not be detected because a voltage drop occurs due to a charging current in the protection circuit in the battery pack.

The present invention has been made to solve the above-mentioned conventional problems, and the control performed by the two terminals for charging and for detecting the battery voltage can be shared by one terminal. It is an object of the present invention to provide a battery pack and a battery pack charger which can reduce the size and cost of the battery pack and the battery pack and can accurately detect the battery voltage.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a charger for charging a battery pack including a secondary battery and a voltage detecting circuit in the battery pack for detecting the voltage of the secondary battery. Yes, including a connection determination circuit for detecting the presence or absence of connection of a battery pack, a voltage detection circuit for detecting a voltage, and a constant current / constant voltage control circuit for receiving an output of the voltage detection circuit and switching a charging method, and has two positive and negative terminals. Is used to control all charging of the battery pack. As a result, the number of terminals can be reduced, so that the size of the charger and the battery pack can be reduced,
Cost reduction can be achieved.

A battery charger for performing pulse charging of a battery pack, wherein one voltage detection circuit detects the battery voltage when the charge output is OFF and detects whether or not the battery pack is connected when the charge output is ON, When the charge output is OFF, the battery voltage can be detected without being affected by the voltage drop by each circuit in the battery pack. When the charge output is ON, the connection of the battery can be detected using the same voltage detection circuit.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. In the present embodiment, a lithium secondary battery is used as a secondary battery.

In FIG. 1, 1 is a lithium secondary battery, 2
Is a protection circuit that protects the rechargeable battery 1 from overcurrent by controlling charging based on the detected current value, 3 is a backflow prevention circuit that prevents backflow of current, and 4 is the voltage of the rechargeable battery 1 that is charged. This is a battery pack internal voltage detection circuit, and the secondary battery 1 to the battery pack internal voltage detection circuit 4 are configured in the battery pack 5.

Reference numeral 6 denotes a charger for performing pulse charging. In the charger 6, when the charging output is OFF, the battery voltage can be detected without being affected by the voltage drop by each circuit in the battery pack 5, and when the charging output is ON, the charging voltage can be detected. Voltage detection circuit 7 for detecting battery connection, reference voltage generation circuit 11 and battery connection detection resistor 12
And a switch circuit 13, a connection determination circuit 8 for determining the presence or absence of a battery connection, and a constant current / constant voltage control circuit 9 which receives an output from the voltage detection circuit 7 and switches between constant current charging and constant voltage charging. . Reference numeral 10 denotes a constant voltage power supply.

In this configuration, while charging is being performed, the switch circuit 13 composed of elements such as a transistor, an FET, and a relay periodically repeats ON / OFF. As shown in FIG. 2, the battery connection and the battery voltage are detected by the voltage detection circuit 7 detecting the voltage in accordance with the ON / OFF timing.

When charging is started, the switch circuit 1
When 3 is ON, it is detected whether or not the battery pack is connected.

More specifically, a voltage detecting circuit 7 connected to the positive and negative terminals of the battery pack includes a battery voltage VB, an output voltage of the reference voltage generating circuit 11, a battery connection detecting resistor 12, and a battery pack internal voltage detecting circuit 4. And the voltage value determined by the load. Battery voltage VB as it is for battery connection determination
If the battery is not connected,
Since the input terminal of the voltage detection circuit may be in an open state to cause erroneous detection, a reference voltage generation circuit 11, a battery connection detection resistor 12, and a switch circuit 13 are configured as the connection determination circuit 8 to prevent this from occurring.

In this configuration, the reference voltage generation circuit 11
When the reference voltage VC is set so that the reference voltage VC output by the following equation is greater than the battery voltage VB, the voltage detection circuit 14 detects the reference voltage VC without being released when the battery is not connected. When a battery is connected, the reference voltage VC is also consumed by other circuits, so the voltage detection circuit 14 detects a value lower than VC. Accordingly, if the voltage detected by the voltage detection circuit 7 is the reference voltage VC, it can be determined that a battery is connected, and the battery pack is connected from the voltage detection circuit 7 to the constant current / constant voltage control circuit. Is sent and charging is continued.

When the switch circuit 13 is OFF, the voltage of the secondary battery 1 is detected. If the battery voltage VB does not exceed the specified value V1 as shown in a state D of FIG. Perform pulse charging with a long cycle.
When the battery voltage VB exceeds the specified value V1 or when the battery voltage VB exceeds the specified value V1 due to charging, the charging is switched to the pulse charging method having an appropriate charging cycle.

When switching to the pulse charging method, the charging / discharging circuit in the constant current / constant voltage control circuit 9 turns ON / O at a constant cycle.
The FF signal is issued, and the charging current is turned ON / OFF.

In detecting the battery voltage during pulse charging, the battery voltage VB is detected when the charging is OFF as shown in the state E of FIG. 3 in order to avoid a voltage drop caused by the protection circuit 2 or the like when the charging current is output. This makes it possible to accurately detect the battery voltage VB without being affected by the voltage effect of the protection circuit or the like. Then, when the battery voltage VB becomes equal to or higher than the specified voltage V2, it is determined that the secondary battery 1 has reached full charge, and charging is terminated. If VB has not reached V2, charging is performed for a certain period of time as shown in state F in FIG. 3 and then the state returns to state E, and the operation is repeated until the battery voltage VB exceeds the specified voltage V2 and charging is completed.

After the completion of charging, the detection of the presence or absence of the battery and the detection of the battery voltage are continued by the voltage detecting circuit 7 and the connection judging circuit 8, whereby accurate charging control of the secondary battery by the two terminals can be performed.

[0024]

As described in the above embodiment, according to the present invention, all charging control of the battery pack can be performed by two positive and negative terminals and the number of terminals can be reduced, so that the size of the charger and the battery pack can be reduced. Therefore, cost reduction can be achieved. Further, since the configuration is such that the battery voltage is detected when the pulse charging switch is turned off, it is possible to solve the problem that a voltage drop due to the charging current occurs in the protection circuit or the like in the battery pack and an accurate voltage may not be detected.

[Brief description of the drawings]

FIG. 1 is a block diagram of a secondary battery charging circuit according to the present embodiment.

FIG. 2 is a transition graph of a battery voltage and a charging current in the present embodiment.

FIG. 3 is a timing chart of voltage detection.

FIG. 4 is a block diagram of a conventional secondary battery charging circuit.

FIG. 5 is a transition graph of a battery voltage and a charging current in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Secondary battery 2 Protection circuit 3 Backflow prevention circuit 4 Battery pack internal voltage detection circuit 5 Battery pack 6 Charger 7 Voltage detection circuit 8 Connection judgment circuit 9 Constant current constant voltage control circuit

Claims (4)

[Claims] A secondary battery; a protection circuit for the secondary battery; a backflow prevention circuit for preventing a backflow of current; and a battery pack internal voltage detection circuit for detecting a voltage of the secondary battery. Wherein each control output is performed only by the two terminals. 2. A connection determination circuit for detecting the presence or absence of connection of a battery pack, a voltage detection circuit for detecting a voltage, and a constant current / constant voltage control circuit for receiving an output of the voltage detection circuit and switching a charging method, A battery pack charger characterized in that all charging control of the battery pack is performed only by two positive and negative terminals. 3. A battery charger for performing pulse charging of a battery pack, wherein a battery voltage is detected by a voltage detecting circuit when a charging output is turned off. 4. A battery charger for performing pulse charging of a battery pack, wherein one voltage detection circuit detects a battery voltage when charging output is OFF, and detects whether or not a battery pack is connected when charging output is ON. The battery pack charger according to claim 3, wherein: