JP3237462B2 - Charging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a charging device used for a small personal computer, a home video camera or the like.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to a charging device shown in FIG.

According to FIG. 1, an emitter of a first transistor 11 is connected to an input power supply terminal 1, and a collector of the first transistor 11 and a charging terminal 16 of a battery 18 are connected.
And the input power supply terminal 2 is connected to the charging terminal 17 to form a charging circuit. To control the charging voltage to the battery 18, the voltage of the battery 18 is divided by the resistors 5 and 6, and the amplifier 14 having the reference A power supply 15 as one input.
A voltage divided by the resistors 5 and 6 is input to the other, and the output of the amplifier 14 is current-amplified by the second transistor 12 and the resistor 4 to control the base of the first transistor 11. Further, a voltage obtained by dividing the voltage of the battery 18 by the resistors 8 and 9 is incorporated in the microcomputer 24 or input to an A / D converter 23 provided outside to monitor the state of charge of the battery 18. .

[0004] The operation of the charging device configured as described above will be described below. First, a power supply (for example, 15 V, with constant current control) from the input power supply terminals 1 and 2
, Is connected to the emitter of the first transistor 11, and is charged from the collector of the first transistor 11 via the positive terminal of the battery 18. The control of the maximum charging voltage (Bv, for example, 12.5 V) to the battery 18 is performed by dividing the voltage of the battery 18 with the resistors 5 and 6 and using the reference A power supply 15 (voltage: Vs) as one input. The voltage divided by the resistor 5 and the resistor 6 is input to the second transistor 12, the output of the amplifier 14 is current-amplified by the second transistor 12 and the resistor 4, and the base of the first transistor 11 is controlled. 11 by changing the impedance between the emitter and the collector. Assuming that the resistance value of the resistor 5 is R5 and the resistance value of the resistor 6 is R6, the following relational expression (1) is obtained.

Equation (1) Bv (12.5 V) / Vs = (R5 + R6) / R6 Note that the battery 18 has a maximum charging voltage (Bv: 12.5 V).
V), the charging current is limited by the internal resistance of the battery 18, but the maximum charging voltage (Bv: 1)
When the voltage is lower than 2.5 V), the charging current to the battery 18 is controlled by the constant current control function of the power supplied from the input power terminals 1 and 2.

[0006]

However, in the above-mentioned conventional configuration, the battery 18 is connected to the charging device in a state where there is no power supply from the input power supply terminals 1 and 2 (power is supplied from a household AC power supply). When the battery 18 is mounted, a current of several tens of μA continues to be discharged from the battery 18 to the resistor 5, the resistor 6, the resistor 8, and the resistor 9. If the resistances of the resistors 5 and 6 and the resistors 8 and 9 are too large in order to reduce the discharge current, the variations in the input currents of the amplifier 14 and the A / D converter 23 cannot be ignored. ) Greatly deteriorates accuracy.

Further, in the above circuit configuration, when the power supply from the input power supply terminals 1 and 2 (power is supplied from a household AC power supply) is stopped while the battery 18 is mounted on the charging device, When the battery 18 does not reach the maximum charging voltage (for example, 12.5 V), the voltage divided by the resistors 5 and 6 from the collector and the emitter of the first transistor 11 is lower than the voltage of the reference A power supply 15 so that the amplifier is not used. 14 is high, the second transistor 1
The collector current of 2 is an operation to increase the base current of the first transistor 11. At this time, if the voltage of the input power supply terminal 1 is lower than the voltage of the battery 18, the first transistor 11 causes a current to flow in from the collector side and flow out to the emitter side. The current is continuously supplied to the microcomputer 24, and the discharge current several mA continues to flow.

As a result, when the battery 18 is left attached to the charging device for a long time, the battery 18 is completely discharged, and the battery 18 is deteriorated or becomes unusable.

The present invention solves the above-mentioned conventional problems, and provides a charging device capable of greatly reducing the discharge current from a battery and greatly reducing the deterioration of the battery even when left for a long time. With the goal.

[0010]

SUMMARY OF THE INVENTION In order to solve this problem, a charging apparatus according to the present invention comprises a resistor connected to a charging terminal of a battery for supplying a divided voltage input to an amplifier and a charging terminal of the battery. A third transistor is provided between which the collector is connected to the charging terminal of the battery, the emitter is connected to the resistor, and the base is connected to the input power supply terminal.

[0011]

According to the present invention, when power is not supplied from the input power supply terminal (power is supplied from a household AC power supply) while the battery is attached to the charging device, the battery is connected to the battery. It is an object of the present invention to provide a charging device in which only a current of less than several hundred nA is discharged, and the deterioration of a battery can be significantly reduced even when left for a long time.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A charging device according to the present invention will be described with reference to FIG.

The same parts as in the prior art are denoted by the same reference numerals, and description thereof will be omitted. Reference numeral 13 denotes a third transistor. The collector is connected to the charging terminal 16, the emitter is connected to the resistor 5, and the base is connected to the input power supply terminal 1 via the resistor 3.

The maximum charge voltage (for example, 12.5 V) of the battery 18 is controlled by receiving the voltage of the battery 18 at the collector of the third transistor 13, dividing the voltage from the emitter by the resistors 5 and 6, and setting the (-) ) Add to input. In this case, if the collector-emitter saturation voltage of the third transistor 13 is large, an error occurs in controlling the maximum charging voltage (for example, 12.5 V) to the battery 18, but the base current of the third transistor 13 is Resistance 3
And a third transistor 13 having a low collector-emitter saturation voltage. The resistance of the resistor 5, the resistor 6, the resistor 8, and the resistor 9 is used. Since the resistance value is set high (to the extent that the input current of the amplifier 14 does not affect), the collector-emitter saturation voltage of the third transistor 13 can be set to several mV, and can be set to a level that does not cause any trouble.

According to the above configuration, when the battery 18 is mounted on the charging device in a state where there is no power supply from the input power supply terminals 1 and 2 (power is supplied from a household AC power supply), the resistance 3 , The base current of the third transistor 13 flowing through the third transistor 13 becomes zero, and the collector current of the third transistor 13 can be set to less than several tens nA, thereby preventing discharge from the battery 18. .

Further, since the power supply to the amplifier 14 is cut off and the input voltage is also cut off, the base voltage of the second transistor 12 becomes zero, and the collector current of the second transistor 12 does not flow. As a result, no diode current flows from the collector of the first transistor 11 to the base.

Next, an embodiment of the present invention will be described with reference to FIG.

[0018] Incidentally, the same parts as the embodiment of FIG. 1 are denoted by the same numbers and only the different parts will be described, the resistance from the input power source terminal 1 to the microcomputer 24 in the resistor 7 10
The in divided voltage converted by the A / D converter 23, means for determining a voltage, a voltage divided voltage of the battery 18 is converted by the A / D converter 23, microcomputer 24 determines means a voltage And a switch 21 for turning on and off the output of the amplifier 14 by the microcomputer 24.

In the figure, in the charging operation, the switch 21 is turned on by the control line 20 of the microcomputer 24, and the output of the amplifier 14 controls the second transistor 12. Here, a case where the voltage of the input power supply terminal 1 gradually decreases due to an abnormality of the input power supply and becomes lower than the chargeable voltage of the battery 18 will be described.
Does not reach the maximum charging voltage (for example, 12.5V), the voltage divided by the resistor 5 and the resistor 6 from the collector and the emitter of the third transistor 13 is lower than the voltage of the reference A power supply 15, so the output of the amplifier 14 Is high, and the collector current of the second transistor 12 is
This is an operation to increase the base current of one. At this time, if the voltage of the input power supply terminal 1 is lower than the voltage of the battery 18, the first transistor 11 causes a current to flow in from the collector side and flow out to the emitter side, so that a discharge current flows from the battery 18. In order to prevent the above phenomenon, the data C obtained by converting the voltage of the input power supply terminal 1 by the A / D converter 23 to the voltage detection line 25 obtained by dividing the voltage of the input power supply terminal 1 by the resistors 7 and 10 and the voltage of the battery 18 by the resistor 8 The microcomputer 24 compares the detection line 19 of the voltage divided by the resistor 9 with the data D converted by the A / D converter 23, and determines that the voltage of the input power supply terminal 1 is lower than a specified value. The switch 21 is turned off by 20. As a result, the second transistor 12
Is the battery 1 without driving the first transistor 11
No discharge current flows from 8.

When the voltage between the input power supply terminals 1 and 2 is lost and the power supply 27 supplied from the reference B power supply 26 to the microcomputer 24 does not supply power, the switch 21 controlled by the control line 20 is turned off. It has become.

FIG. 3 shows another embodiment of the charging device of the present invention.
Ri, when only be described differs from the embodiment of FIG. 2, the configuration of the diode 7 which prevents reverse flow of charging current to the collector of the first transistor 11 is connected, to connect the charging terminal 16 of the battery 18 to the output It was done.

Referring to FIG . 2, a case similar to the embodiment of FIG. 2 , that is, a case where the voltage of the input power supply terminal 1 gradually decreases due to an abnormality of the input power supply and the like and the battery 18 becomes less than the chargeable voltage will be described. In this state, when the battery 18 does not reach the maximum charging voltage (for example, 12.5 V), the voltage received by the collector of the third transistor 13 and divided from the emitter by the resistors 5 and 6 is applied to the reference A power supply 15. , The output of the amplifier 14 is high and the collector current of the second transistor 12 is
In order to perform the operation of increasing the base current of the transistor 11 of FIG. The voltage detection line 19 obtained by dividing the voltage of the voltage 18 by the resistors 8 and 9 is connected to the A / D converter 23.
The microcomputer 24 compares the converted data F with the microcomputer 24 and determines that the input terminal voltage is lower than the specified value.
Turn 1 off.

As a result, the second transistor 12 becomes the first transistor
Does not drive the transistor 11 and does not cause a discharge current to flow from the battery 18. However, even if the base current of the second transistor 12 is reduced to zero, the collector cutoff current is not zero. The first transistor 11 flows on the substrate due to ambient humidity and the like.
A small current also flows in the collector current of. However, the reverse voltage of the diode 7 is divided by the diode 7 from the collector voltage of the first transistor 11, and the reverse current of the diode 7 can be further reduced by the amount of the divided reverse voltage. It is.

[0024]

As described above, according to the present invention, the base is connected to the input power supply terminal, the collector is connected to the charging terminal of the battery, and the emitter is connected to the amplifier via the resistor. When the power supply from the input power supply terminal is stopped while the battery is mounted, only a current of less than several hundred nA is discharged from the battery, and the deterioration of the battery can be greatly reduced even if the battery is left for a long time. Things.

Further, A / A is added to the microcomputer.
Means for determining the battery voltage or the input power supply voltage based on the divided voltage of the battery or the input power supply converted by the D converter and switch means for turning on and off the output of the second transistor are provided. The second transistor is turned off, the first transistor is not driven, and the discharge current from the battery is further reduced.

Furthermore, in a device provided with means for preventing a backflow of charging current from the battery to the collector of the first transistor between the collector of the first transistor and the collector of the second transistor, It should be noted that the discharge current can be further prevented from decreasing.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a charging device according to an embodiment of the present invention.

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

FIG. 3 is a circuit diagram of another embodiment of the present invention .

FIG. 4 is a circuit diagram of a conventional charging device.

[Explanation of symbols]

 1, 2, input power supply terminal 3, 4, 5, 6, 7, 8, 9, 10, 22 resistor 11 first transistor 12 second transistor 13 third transistor 14 amplifier 15 reference A power supply 16, 17 charging terminal 18 Battery 19, 25 Detection line 20 Control line 21 Switch 23 A / D converter 24 Microcomputer 26 Reference B power supply

Claims (2)

(57) [Claims] A DC power supply is used as an input power supply. The input power supply is connected to an emitter of a first transistor, and a collector of the first transistor is connected to a plus terminal of a battery and a collector of a third transistor. , The third
And the other input of the amplifier having the reference power supply as one input from the emitter of the transistor via the first resistor, the second resistor is connected, and the other of the second resistors is connected to the negative terminal of the battery. And the negative terminal of the input power supply, and the output of the amplifier is connected to the base of the second transistor .
And the collector of this second transistor is
In the first connected to the base of the transistor, the charging device base connected to the emitter of the first transistor via a resistor of the third transistor, said input voltage
A / D converter converts the voltage divided by a resistor from the source
Means for determining this voltage with a microcomputer
And the voltage obtained by dividing the battery voltage into an A / D converter
Means for converting the voltage and determining the voltage with a microcomputer
And the output of the amplifier by this microcomputer
Or a switch for turning on and off the output of the second transistor.
A charging device provided with a switch means . 2. The charge charging device according to claim 1, wherein
Connect a means to prevent current backflow, and connect
Between the positive terminal of the transistor and the collector of the third transistor.
The charging device according to claim 1, which is continued .