JPH08182216A - Charging current bypass circuit of secondary battery - Google Patents

Abstract

PURPOSE: To prevent excessive bypassing of a charging current of the secondary battery. CONSTITUTION: A Zener diode 6 and a resistor 5 generate a reference voltage V1 and also input this voltage to an inverted input terminal of a comparator 4 via an input protection resistor 9. A variable resistor 7 divides to drop a terminal voltage of a single battery 1 and then inputs the voltage to a non- inverted input terminal of the comparator 4 via an input protection resistor 8. An NPN type transistor 2 connected to an output terminal of the comparator 4 bypasses a charging current depending on the voltage applied to the base. The comparator 4 is connected to the positive electrode of a single battery 1 in the positive power supply terminal and also connected to the negative electrode of the single battery 1 via a resistor 10 in the negative power supply terminal. The reference voltage V2 generated by the Zener diode 12 and resistor 13 is applied to the resistor 10 via the resistor 11. The comparator 4 is operated while the terminal voltage of the single battery 1 is higher than the setting voltage and thereby the charging current can be bypassed to the adequate value to prevent over-bypassing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rechargeable battery charge current bypass circuit for controlling the charge amount of a rechargeable battery by bypassing the rechargeable battery charge current.

[0002]

2. Description of the Related Art As a conventional charging current bypass circuit,
For example, there is a circuit as shown in FIG. This is a single battery 2
A transistor 22 for bypassing the charging current to 1,
The resistor 23 is connected in parallel, the comparator 24 compares the terminal voltage of the unit cell 21 with the reference voltage V0 generated by the zener diode 26 and the resistor 25, and the transistor 22 is controlled by the comparison difference to control the bypass amount of the charging current. To control.

[0003]

However, in such a conventional charging current bypass circuit, since the bypass generation amount is based on the generation accuracy of the reference voltage V0 and the comparison accuracy of the comparator 24, when they fail. Therefore, the desired charging current does not flow to the unit cell 21. In particular, when the transistor 22 in which the bypass current flows fails in a short circuit state, when the comparators 24 fail to compare the terminal voltages with a higher level, or when the transistor 22 fails to control a large amount of bypass. A single cell 2
There is a problem that the terminal voltage of 1 is discharged to a low voltage beyond the range that should be controlled, and the unit cell is over-discharged and deteriorated. In view of the above problems, it is an object of the present invention to provide a charging current bypass circuit that prevents the charging current from being excessively bypassed and prevents the terminal voltage from being discharged below a predetermined value. And

[0004]

Therefore, according to the present invention, the voltage detecting means for detecting the terminal voltage of the secondary battery and one of the charging currents connected to both ends of the secondary battery for charging the secondary battery are described. A secondary unit including a bypass unit that bypasses all or a part of the unit, and a bypass amount control unit that controls the bypass unit so that the terminal voltage of the secondary battery falls within a predetermined range based on the detection value of the voltage detection unit. In a battery charging current bypass circuit, when the terminal voltage of the secondary battery is lower than a predetermined value, the bypass means or the bypass amount control means is inoperably controlled to prevent the generation of the bypass current. Means were provided.

[0005]

In the present invention, the voltage detecting means detects the terminal voltage of the unit cell, and the bypass amount control means causes the bypass means to bypass the charging current based on the detected value of the terminal voltage.
The terminal voltage is controlled so that it falls within a predetermined range. At that time, the over-discharge prevention means causes the above control to be performed when the voltage exceeds a predetermined value according to the terminal voltage, and in the following cases, the bypass means or the bypass amount control means is controlled to be inoperative to prevent the generation of the bypass current. Therefore, the operation of the bypass means does not cause the unit cell to be over-discharged to a predetermined value or less, and the charging current can be bypassed without degrading the unit cell.

[0006]

1 is a circuit diagram showing a first embodiment of the present invention. The Zener diode 6 and the resistor 5 generate the reference voltage V1, and the reference voltage V1 is input to the inverting input terminal of the comparator 4 via the input protection resistor 9. The variable resistor 7 is a resistor that divides the terminal voltage of the unit cell 1 and is input to the non-inverting input terminal of the comparator 4 via the input protection resistor 8 to detect the potential difference between the terminal voltage of the battery and the reference voltage V1. Make up the circuit. The NPN transistor 2 whose base is connected to the output terminal of the comparator 4 controls the current flowing through the resistor 3 according to the voltage applied between the base and the emitter. The positive power supply terminal of the comparator 4 is connected to the positive electrode of the cell 1 and the negative power supply terminal is connected to the negative electrode of the cell 1 via the resistor 10. Zener diode 12 and resistor 1
3 generates a reference voltage V2, which is divided by the resistors 10 and 11 and applied to the negative power supply terminal of the comparator 4.

When the secondary battery 1 is charged, the terminal voltage rises as the charging time elapses. While the terminal voltage of the secondary battery is low, the voltage supplied to the comparator 4 is also low, so the comparator 4 does not operate and cannot output a high-potential ON signal. Absent. When the terminal voltage of the unit cell 1 reaches a certain voltage, the comparator 4 becomes operable. From the operating voltage of the comparator 4, the terminal voltage at which the bypass current can be generated in the unit cell 1 is determined by the reference voltage V2 and the voltage division ratio of the resistors 10 and 11. The terminal voltage is lower than the reference voltage V1. After that, the terminal voltage further rises and the NPN transistor 2
In the cutoff state, no charging current flows through the resistor 3. When the terminal voltage becomes higher than the reference voltage V1, the output of the comparator 4 becomes positive, the NPN transistor 2 becomes conductive, and a part of the charging current is bypassed to the resistor 3. In this case, if the terminal voltage is large, the voltage applied between the base and the emitter is also large, so that the current flowing through the resistor 3 is also large. As a result, the terminal voltage of the unit cell 1 is finally kept within a certain range.

This embodiment is constructed as described above, and 2
The comparator 4 that detects the terminal voltage of the secondary battery receives power from the secondary battery 1, and the supply voltage is the comparator 4.
Since the voltage of the negative power supply terminal is raised in accordance with the operating voltage of the variable voltage, the voltage applied to the positive terminal rises due to the fluctuation of the voltage dividing ratio of the variable resistor 7, and the short circuit failure of the Zener diode 6 occurs. In this case, the comparator 4 cannot operate because the terminal voltage drops. As a result, the bypass current is generated within the limited high terminal voltage range, and the overcurrent of the unit cell 1 due to the generation of the bypass current is prevented.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention. In the first embodiment, by using the operating voltage of the comparator 4 and raising the voltage of its negative power supply terminal, the bypass current can be generated only when the terminal voltage is a predetermined value or more. A resistor 16, a Zener diode 15 and a PNP transistor 14 are used instead of the resistors 10, 11, 13 and the Zener diode 12 of the first embodiment shown in FIG. Is. Other configurations are similar to those of the first embodiment.

The Zener diode 15 and the resistor 16 generate the reference voltage V3 and the PNP transistor 16
Applied to the base of. The emitter and collector of the PNP transistor 14 are connected to the positive power supply terminal of the comparator 4 and the positive electrode of the unit cell 1 in the forward current direction. When the terminal voltage is high, the PNP transistor 14 is in the conductive state because the voltage between the emitter and the base is high, and the comparator 4 is supplied with power. When it is low, the transistor 14 is cut off and the comparator 4 cannot operate. As a result, the comparator 4 operates in the same manner as in the first embodiment, and the entire circuit has the same effect as in the first embodiment without over-discharging the unit cell 1.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention. This embodiment is similar to the comparator 4 of the second embodiment.
A PNP transistor 17 is used instead of the PNP transistor 14 provided at the positive power supply terminal of the above, and the NPN transistor 2 is connected in series. The reference voltage V3 is applied to the base of the transistor 17. Although the comparator 4 can operate when the terminal voltage is low, P
Since the voltage between the emitter and the base of the NP transistor 17 is low, the NP transistor 17 is in the cutoff state, and no bypass current is generated.
When the terminal voltage becomes high, the PNP transistor 17 becomes conductive, and a bypass current can be generated. As a result, the entire circuit functions similarly to the first and second embodiments, and the same effect as that of the first embodiment can be obtained without over-discharging the unit cell 1.

[0012]

As described above, according to the present invention, the voltage detecting means detects the terminal voltage of the unit cell, and the bypass amount control means causes the bypass means to bypass the charging current based on the detected value of the terminal voltage. In a charging current bypass circuit for controlling a voltage within a predetermined range, an over-discharge preventing means is provided to perform the above control when the terminal voltage is a predetermined value or more, and in the following cases, the bypass means or the bypass amount control means is used. Since it is controlled to be inoperable to prevent the generation of bypass current, the operation of the bypass means does not discharge the unit cell to a predetermined value or less, and the charging current can be bypassed without degrading the unit cell. it can. As a result, when a plurality of cells are connected in series and used as an assembled battery, the cells can be uniformly charged and the number of times of charging and discharging can be extended.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment.

FIG. 2 is a circuit diagram showing a second embodiment.

FIG. 3 is a circuit diagram showing a third embodiment.

FIG. 4 is a circuit diagram showing a conventional example.

[Explanation of symbols]

 1, 21 Secondary battery 2, 22 NPN transistor 3, 5, 8, 9, 10, 11, 13 Resistor 4 Comparator 6, 15, 26 Zener diode 7 Variable resistor 14, 17 PNP transistor 16, 23, 25, 28, 29 Resistance

Claims (4)

[Claims] 1. A voltage detecting means for detecting a terminal voltage of a secondary battery, and a bypass means connected to both ends of the secondary battery for bypassing a part or all of a charging current to the secondary battery during charging. A bypass amount control means for controlling the bypass means so that the terminal voltage of the secondary battery falls within a predetermined range based on the detection value of the voltage detection means 2
In a charging current bypass circuit for a secondary battery, when the terminal voltage of the secondary battery is lower than a predetermined value, the bypass means or the bypass amount control means is inoperably controlled to prevent the generation of the bypass current. A charging current bypass circuit for a secondary battery, which is provided with a prevention means. 2. The bypass means is composed of a transistor connected in parallel with the secondary battery, the bypass amount control means includes a comparator supplied with power from the secondary battery, and the terminal voltage is a predetermined value. 2. The supply voltage to the comparator is set to be lower than its operating voltage when it is lower, and the generation of bypass current in the transistor is prevented by stopping the operation of the comparator. Secondary battery charging current bypass circuit. 3. The bypass means comprises a first transistor connected in parallel with the secondary battery, and the bypass amount control means has a comparator supplied with power from the secondary battery. The discharge prevention unit includes a second transistor that controls the power supply, and stops the power supply to the comparator when the terminal voltage is lower than a predetermined value to stop the operation of the comparator and generate a bypass current in the transistor. The charging current bypass circuit for the secondary battery according to claim 1, which prevents the charging current bypass circuit. 4. The bypass means is composed of a first transistor connected in parallel with the secondary battery, and the overdischarge prevention means is provided with a second transistor connected in series with the first transistor. 2. The charging current for a secondary battery according to claim 1, further comprising a transistor, wherein when the terminal voltage is lower than a predetermined value, the current path of the second transistor is cut off to prevent the generation of the bypass current. Bypass circuit.