JPH0937480A - Battery charging controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery charging controller capable of manufacture at low cost by enlarging the range of processable voltage of battery voltage without lowering the resolution of an analog-digital converter. SOLUTION: This controller is equipped with a charging current generator, which charges a battery, a battery's voltage converter 1, which converts the voltage of the voltage (VBAT) of the battery, an analog-digital converter 5, which converts the output analog voltage of the converter 1 into digital, and a controller 6 which controls the supply and stop of the output current of the charging current generator. And, the converter 1 consists of a variable potential divider circuit 15, which generates the partial potential offset voltage (VDOFF) by dividing the applied offset voltage (VOFF), and a voltage offset circuit 16 which supplies the converter 5 with voltage (VOFBAT) being offset from battery voltage (BBAT) to minus side by the amount of partial potential offset voltage (VDOFF), and for the variable potential divider circuit 15, the potential dividing ratio can be switched in stages, corresponding to the magnitude of the battery voltage (VBAT), by the control of the controller 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery charge control device, and more particularly, to analog-digital conversion when the battery voltage of a battery to be charged is analog-digital converted and the digital output controls the charging of the battery to be charged. The present invention relates to a battery charge control device in which the resolution at the time of conversion is not lowered and the voltage range of the battery voltage capable of analog-digital conversion is expanded.

[0002]

2. Description of the Related Art Generally, a battery charge control device supplies a charging current to a battery to be charged, such as a nickel-hydrogen battery or a nickel-cadmium (nicad) battery, to charge the battery, and the battery voltage of the battery to be charged is changed. When the battery is fully charged, it automatically stops the supply of the charging current to the battery to be charged. A known battery charge control device in which such an operation is performed includes a charging current generator that supplies a charging current to a battery to be charged, a battery voltage converter that converts the battery voltage detected by the battery to be charged, and a battery voltage. Supplying the charging current output from the charging current generator to the battery to be charged in response to the analog-to-digital converter that converts the battery voltage level-converted by the converter to analog-to-digital conversion and the digital output from the analog-to-digital converter. And a control unit that operates so as to start or stop.

By the way, in the known battery charge control device, the battery full charge detecting means may be, for example, an actual fair 3-40.
As disclosed in No. 060, it is determined that the battery is fully charged when it is detected that the battery voltage drops from the peak voltage value by a minute constant voltage ΔV after the battery voltage reaches the peak voltage value. However, it is known that the battery charging is stopped, and the battery charge control device of the present invention also detects the full charge of the battery by such means. Further, since the battery voltage during charging is higher than the power supply voltage of the analog-digital conversion unit in the battery charge control device, in the known battery charge control device, on the input side of the analog-digital conversion unit, By providing a battery voltage conversion unit that converts the battery voltage to a low voltage, the analog-digital conversion unit is prevented from being supplied with a battery voltage higher than the power supply voltage, and the active element such as a transistor constituting the analog-digital conversion unit is supplied with the power supply voltage. It prevents damage when supplying a higher battery voltage.

In this case, in the known battery charge control device, as the battery voltage converter provided on the input side of the analog-digital converter, a voltage divider is used to attenuate the input battery voltage, and a voltage offset. A circuit is used to offset the input battery voltage to the low voltage side, a voltage divider circuit and a voltage offset circuit are used together to attenuate the input battery voltage and to offset the input battery voltage to the low voltage side. What is known is.

FIG. 6 is a block diagram showing a configuration of a main part in a first example of a known battery charge control device, and shows an example in which a voltage dividing circuit is used in a battery voltage conversion unit.

As shown in FIG. 6, the battery charge control device of this embodiment includes a battery voltage conversion unit 60 including an inverse L-type voltage dividing circuit 61, an analog-digital conversion unit (A / D) 62,
And a control unit (CPU) 63. Inverse L type voltage dividing circuit 61
Is composed of a series resistor 64 and a shunt resistor 65, and
The battery voltage (V _BAT ) is supplied to 0i, and the input end of the analog-digital conversion unit 62 is connected to the output end 60o.
The series resistor 64 is connected between the input end 60i and the output end 60o, and the shunt resistor 65 is connected between the output end 60o and the ground. The output end of the analog-digital conversion unit 62 is connected to the input end of the control unit 63.

In the above configuration, the inverted L-type voltage dividing circuit 61
Is a battery to be charged supplied to the input end 60i (not shown)
Battery voltage (V _BAT ) from the series resistor 64 and shunt resistor 6
The voltage is divided by 5 and output from the output terminal 60o as a _divided battery voltage (V _DBAT ). Next, the analog-digital conversion unit 62 converts the _divided battery voltage (V _DBAT ) into analog-
Digitally convert and generate digital output. Control unit 63
When the digital output is supplied, controls the operation of the charging current generator (not shown) that supplies the charging current to the battery to be charged according to the digital value, and supplies the charging current to the battery to be charged. Or, stop the charging current to the current to be charged. In this case, the _divided battery voltage (V _DBAT ) is analog-
It is lower than the power supply voltage of the digital conversion unit 62.

Next, FIG. 7 is a block configuration diagram showing a configuration of a main part in a second example of a known battery charge control device, and shows an example in which a voltage offset circuit is used in a battery voltage conversion unit. .

As shown in FIG. 7, the battery charge control device of this embodiment has a battery voltage conversion unit 70 including a voltage offset circuit 71 and an analog-digital conversion unit (A / D) 72.
And a control unit (CPU) 73. The voltage offset circuit 71 includes an operational amplifier 74, a feedback resistor 75, a first
It is composed of a series resistor 76, a second series resistor 77, and a shunt resistor 78, and has an offset voltage (V
_OFF ), the battery voltage (V _BAT ) is supplied to the second input terminal 70i ″, and the input terminal of the analog-digital converter 72 is connected to the output terminal 70o. The feedback resistor 75 is an inverting input terminal of the operational amplifier 74. Is connected between the first input terminal 70i ′ and the operational amplifier 74.
Connected to the inverting input terminal of. The second series resistor 77 is connected between the second input 70i ″ and the non-inverting input of the operational amplifier 74, and the shunt resistor 78 is connected between the non-inverting input of the operational amplifier 74 and ground. The output end of the conversion unit 72 is connected to the input end of the control unit 73.

In the above configuration, the voltage offset circuit 7
If the resistance values of the feedback resistor 75, the first series resistor 76, the second series resistor 77, and the shunt resistor 78 that configure 1 are selected to be substantially equal to each other, the operational amplifier 74 operates as the second input terminal 70i ″.
The battery voltage (V _BAT ) from the battery to be charged (not shown) supplied to is offset to the negative side by the offset voltage (V _OFF ) supplied to the first input end 70i ′,
The offset battery voltage (V _OFFBAT ) is output from the output terminal 70o. Next, the analog-digital converter 72 performs analog-digital conversion on the offset battery voltage (V _OFFBAT ) to generate a digital output. When the digital output is supplied, the control unit 73 controls the operation of a charging current generation unit (not shown) that supplies the charging current to the battery to be charged according to the digital value, and the charging current to the battery to be charged is controlled. Or to stop the charging current to the current to be charged. Also in this case, the maximum positive voltage value of the offset battery voltage (V _OFFBAT ) is smaller than the power supply voltage of the analog-digital conversion unit 62.

Next, FIG. 8 is a block diagram showing a configuration of a main part in a third example of a known battery charge control device, in which an inverse L-type voltage dividing circuit and a voltage offset circuit are used together in a battery voltage converting section. It shows an example.

As shown in FIG. 8, the battery charge control device of this embodiment has a battery voltage conversion unit 80 including an inverse L-type voltage dividing circuit 81 and a voltage offset circuit 82, and an analog-digital conversion unit (A / D) 83 and a control unit (CPU) 84. The inverse L-type voltage dividing circuit 81 includes a series resistor 85 and a shunt resistor 86, and has its input end (first input end 80).
i ′) is supplied with the battery voltage (V _BAT ), and the output terminal (first output terminal 80o ′) thereof has the analog-digital conversion unit 8
The first input terminals of 3 are connected. Voltage offset circuit 82
Is composed of an operational amplifier 87, a feedback resistor 88, a first series resistor 89, a second series resistor 90, and a shunt resistor 91, and has an offset voltage (at the first input end (second input end 80i ″)). V _OFF ) is supplied, the battery voltage (V _BAT ) is supplied to the second input end (first input end 80i ′), and the output end (second output end 80o ″) of the analog-digital converter 82 is supplied. The second input end is connected. The feedback resistor 88 is connected between the inverting input terminal and the output terminal of the operational amplifier 87,
The first series resistor 89 is connected to the first input terminal 80i ″ and the operational amplifier 8
7 is connected to the inverting input terminal. Second series resistor 90
Is connected between the first input terminal 80i ′ and the non-inverting input terminal of the operational amplifier 87, and the shunt resistor 91 is connected between the non-inverting input terminal of the operational amplifier 87 and the ground. The output end of the analog-digital conversion unit 83 is connected to the input end of the control unit 84.

In the above configuration, the inverted L-type voltage dividing circuit 81
Divides the battery voltage (V _BAT ) from the battery to be charged (not shown) supplied to the first input end 80i ′ by the series resistor 85 and the shunt resistor 86, and divides it from the first output end 60o ′. Output as battery voltage (V _DBAT ). If the resistance values of the feedback resistance 88, the first series resistance 89, the second series resistance 90, and the shunt resistance 91 that form the voltage offset circuit 82 are selected to be substantially equal to each other, the operational amplifier 87 is
The battery voltage (V _BAT ) from the battery to be charged (not shown) supplied to the input end 80i ″ is offset to the negative side by the offset voltage (V _OFF ) supplied to the second input end 80i ″, and the second The voltage is output as an offset battery voltage (V _OFFBAT ) from the output end 80o ″. At this time, the analog-digital conversion unit 83 supplies the _divided battery voltage (V _DBAT ) supplied to the first input end and the second input end. The _divided battery voltage (V _DBAT ) or the offset battery voltage (V _OFFBAT ) according to the magnitude of the offset battery voltage (V _OFFBAT )
Is selectively analog-digital converted, and a digital output associated with the conversion is generated. When the digital output is supplied, the control unit 84 controls the operation of a charging current generating unit (not shown) that supplies the charging current to the battery to be charged according to the digital value, and the charging current is supplied to the battery to be charged. Or to stop the charging current to the current to be charged. In this case, the size of the _divided battery voltage (V _DBAT ) that is analog-digital converted in the analog-digital converter 83, or
The plus-side maximum voltage of the offset battery voltage (V _OFFBAT ) is smaller than the power supply voltage of the analog-digital conversion unit 84.

[0014]

The first example of the known battery charge control device described above is a battery voltage supplied to the battery voltage conversion unit 60 by an inverse L-type voltage dividing circuit 61 having a relatively simple circuit configuration. the V _BAT), analog - to convert the power supply voltage less the divided potential battery voltage than the digital converting section 62 (V _DBAT), analog - but those that are applied to digital conversion unit 62, the battery voltage (V _BAT ), It is apparent that the analog-digital conversion unit 6 is used.
There is a problem that the resolution of No. 2 is lowered and the conversion function of the analog-digital conversion unit 62 cannot be fully exerted.

The second of the known battery charge control devices is also provided.
In the example, the voltage-offset circuit 71 that offsets the voltage to the negative side converts the battery voltage (V _BAT ) supplied to the battery voltage converter 70 into an analog-digital converter 72.
The offset battery voltage (V _OFFBAT ) smaller than the power supply voltage of the analog-digital converter 72.
However, since the battery voltage (V _BAT ) is offset to the negative side as it is, all voltages below a certain voltage in the offset battery voltage (V _OFFBAT ) are 0V. Therefore, the battery voltage (V
There is a problem that the voltage range of _BAT ) is narrowed.

Further, a third example of the known battery charge control device uses a combination of the first example of the known battery charge control device and the second example of the known battery charge control device. Includes an inverse L-type voltage dividing circuit 81 and a voltage offset circuit 82.
Corresponding to the magnitude of the battery voltage (V _BAT ) supplied to the battery voltage conversion unit 80, the _divided battery voltage (V) smaller than the power supply voltage of the analog-digital conversion unit 83 is used.
_DBAT ) and apply it to one input terminal of the analog-to-digital converter 83, or the analog-to-digital converter 83
_Is converted to an offset battery voltage (V _OFFBAT ) smaller than the power supply voltage of the analog-digital conversion unit 83.
Although it is applied to the other one input terminal of the above, the problems occurring in the first example of the known battery charge control device and the second example of the known battery charge control device are temporarily solved,
An additional input terminal of the analog-to-digital converter 83 is required, and the analog-to-digital converter 83 becomes expensive accordingly, which in turn causes a new problem that the cost of the battery charge control device increases.

The present invention solves these problems, and an object thereof is to expand the voltage range in which the battery voltage can be processed without lowering the resolution of the analog-digital conversion section, and to manufacture at low cost. An object of the present invention is to provide a battery charge control device that can do so.

[0018]

In order to achieve the above object, the present invention provides a charging current generator for charging a battery to be charged, and a battery voltage converter for converting the battery voltage of the battery to be charged. An analog-to-digital converter that digitally converts the output analog voltage of the battery voltage converter, and a control that responds to the output digital signal of the analog-to-digital converter and controls supply and stop of the output current of the charging current generator. And a variable voltage divider circuit that divides the applied offset voltage to generate a divided voltage offset voltage, and receives the battery voltage and the divided voltage offset voltage, and outputs the battery voltage. A voltage offset circuit that supplies a voltage offset to the negative side by the voltage-division offset voltage to the analog-digital conversion unit, , In response to said magnitude of the battery voltage, and comprises means for switching stepwise partial pressure ratio by a control of the control unit.

[0019]

According to the above means, in the battery voltage converter,
The supplied offset voltage (V _OFF ) is _divided according to the voltage division ratio set in the variable voltage dividing circuit and converted into a _divided voltage offset voltage (V _DOFF ). This voltage- _divided offset voltage (V _DOFF ) is an offset battery in which the battery voltage (V _BAT ) supplied from the battery to be charged is offset to the negative side and the battery voltage (V _BAT ) is offset to the negative side in the voltage offset circuit. The voltage (V _OFFBAT ) is supplied to the analog-digital converter. In this case, in the variable voltage dividing circuit, the voltage dividing ratio is switched stepwise according to the magnitude of the supplied battery voltage (V _BAT ) under the control of the control unit, and the voltage dividing circuit is supplied with the voltage dividing ratio accordingly. Since the voltage value of the voltage offset voltage (V _DOFF ) can also be changed stepwise, the offset battery voltage (V _OFFBAT ) output from the voltage offset circuit is the voltage division offset voltage (V
_{Each time DOFF} ) changes in steps, the degree of offset to the minus side decreases in steps. That is, when the voltage value of the battery voltage (V _BAT ) is small, the voltage dividing ratio of the variable voltage dividing circuit is small, and the degree of offset of the battery voltage (V _BAT ) in the voltage offset circuit to the negative side is small, but As the voltage value of (V _BAT ) increases, the voltage division ratio of the variable voltage dividing circuit gradually increases, and the degree of offset of the battery voltage (V _BAT ) in the voltage offset circuit to the negative side also increases stepwise. .

As described above, according to the above means, the offset battery voltage (V
_OFFBAT ) is not a voltage obtained by dividing the battery voltage (V _BAT ) by the resistance voltage divider circuit, so that the function of the analog-digital converter can be fully exhibited without lowering the resolution of the analog-digital converter. it can.

According to the above-mentioned means, when the battery voltage (V _BAT ) is offset to the minus side by using the voltage offset circuit, the battery voltage (V _BAT ) has a relatively small voltage value. , Offset battery voltage (V _OFFBAT )
Becomes 0 V, and the battery voltage (V _BAT ) lower than that cannot be detected by the analog-digital conversion unit. Therefore, the battery voltage (V
The detection range of ( _BAT ) can be greatly expanded.

Further, according to the above-mentioned means, since the voltage offset circuit is substantially used, the analog-
Since the number of input terminals of the digital conversion unit can be set to one, an expensive analog-digital conversion unit is not required, and the manufacturing cost of the battery charge control device can be reduced.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing the outline of the overall configuration of the battery charge control device according to the present invention.

The battery charge control device according to the present invention charges a battery 10 to be charged, such as a nickel hydrogen battery or a nickel-cadmium (nickel cadmium) battery, and as shown in FIG. A battery voltage converter 1 for converting the battery voltage of 10, a constant current charging circuit 2 for selectively supplying a charging current to the battery 10 to be charged, a temperature sensor 3 for sensing the ambient temperature of the battery 10 to be charged, Temperature sensor 3
Temperature detecting unit 4 for detecting the sensed temperature of the battery as a corresponding electric signal, and an analog-digital converting unit (A / D) for converting each analog voltage from the battery voltage converting unit 1 and the battery temperature detecting unit 4 into a digital output. 5, and a control unit (CPU) that controls the battery voltage conversion unit 1, the constant current charging circuit 2, and the like in response to the digital output from the analog-digital conversion unit 5.
6, a constant voltage circuit 7 that supplies a power supply voltage to the analog-digital conversion unit 5 and the control unit 6, a reset circuit 8 that resets the state of the control unit 6, and a light emitting diode that displays the operating state of the control unit 6 ( LED) 9, and a battery 10 to be charged that is connected between the pair of terminals 10 _T1 and 10 _T2 during charging,
A pair of power supply terminals 1 to which a power supply voltage (Vcc) is supplied
1 _T1 and 11 _T2 , first and second buffer diodes 12 and 13, and a fuse 14.

The battery voltage converter 1 has an input end connected to one end (positive side) of the battery 10 to be charged through one terminal 10 _T1 , and an output end analog-digital converter 5.
Of the control signal is connected to the input terminal of the control signal output terminal of the control section 6. The constant current charging circuit 2 has an input end connected to one power supply terminal 11 _T1 via a fuse 14 and a first buffer diode 12, and an output end via a second buffer diode 13 and a terminal 10 _T1 . Is connected to one end (positive side) of the battery to be charged 10, and the control end is connected to the switching signal output unit of the control unit 6. Temperature sensor 3
Is disposed close to the battery 10 to be charged, one end of which is connected to the input end of the battery temperature detection unit 4 and the other end of which is grounded. The output end of the battery temperature detection unit 4 is connected to the second input end of the analog-digital conversion unit 5. The analog-digital conversion unit 5 is integrally formed in the control unit 6, and the output end thereof is connected to the input end of the control unit 6 although not shown in FIG. The constant voltage circuit 7 has an input end through the fuse 14 and the first buffer diode 12 and is connected to one power supply terminal 11 _T1.
And the output end is connected to the power supply end of the control unit 6. The reset circuit 8 has an input end connected to the output end of the constant voltage circuit 7, and an output end connected to the reset end of the control unit 6. The light emitting diode 9 has an anode side connected to the third control end of the control unit 6 via a resistor and a cathode side grounded. The other terminal 10 _T2 is connected to the other end (negative polarity side) of the battery 10 to be charged and grounded, and the other power supply terminal 11 _T2 is also grounded.

The battery charging control device of the present invention having the above-described structure operates generally as follows.

The battery 10 to be charged to be charged is connected between the pair of terminals 10 _T1 and 10 _T2 , and the pair of power supply terminals 11 _T1 and
Supply power between 11 and _T2 . Due to this power supply, both the constant current charging circuit 2 and the constant voltage circuit 7 are in the operating state, and the charging current having a constant current value output from the constant current charging circuit 2 is charged via the second buffer diode 13. While being supplied to the battery 10, a constant voltage (for example, 5 V) is output to the output of the constant voltage circuit 7, and the output constant voltage is used as a power supply voltage for the control unit 6 and the analog-digital conversion unit 5.
Is supplied to. In this case, the output constant voltage of the constant voltage circuit 7 is supplied to the reset circuit 8, and the state of each unit of the control unit 6 is reset by the reset signal of the reset circuit 8 generated at that time. Further, when the control unit 6 is activated, the light emitting diode 9 is turned on.

In this state, the battery 10 to be charged is sequentially charged by the charging current having a constant current value output from the constant current charging circuit 2, and the battery voltage (V _BAT ) of the battery 10 to be charged is increased.
Gradually rises. In this case, the battery voltage conversion unit 1 receives the battery voltage (V _BAT ) from the battery 10 to be charged and uses the _divided voltage offset voltage (V _DOFF ) to calculate the battery voltage (V
The _BAT) generates a partial pressure offset voltage (V _DOFF) component offset battery voltage offset to the negative side (V _OFFBAT), the offset battery voltage (V _OFFBAT) succeeding analog - to supply to the digital converter 5 . The analog-digital conversion unit 5 receives the supplied offset battery voltage (V
_OFFBAT ) is converted from analog to digital, and a digital signal is supplied to the control unit 6 in the next step. The control unit 6 appropriately supplies a control signal to the battery voltage conversion unit 1 via the control signal output unit according to the voltage value of the supplied digital signal, and the divided voltage offset voltage obtained by the battery voltage conversion unit 1 is supplied. By controlling (V _DOFF ) stepwise, the offset amount of the offset battery voltage (V _OFFBAT ) output from the battery voltage conversion unit 1 to the negative side is adjusted. Then, the control unit 6, advances the charging of the rechargeable battery 10, that the battery voltage supplied to the battery voltage converter 1 (V _{BA T)} is fully charged (100% charge), the battery voltage conversion When the offset battery voltage (V _OFFBAT ) output from the unit 1 is detected by a _slight constant voltage ΔV dropping from the peak voltage value, the switching signal generator immediately supplies the switching signal to the constant current charging circuit 2, The output of the charging current having a constant current value in the constant current charging circuit 2 is stopped, and the charging of the battery 10 to be charged is terminated.

On the other hand, the internal temperature of the battery 10 to be charged rises as charging proceeds. In this case, the temperature sensor 3 arranged close to the battery 10 to be charged detects an increase in the internal temperature of the battery 10 to be charged, and the battery temperature detection unit 4 generates a voltage corresponding to the temperature detected by the temperature sensor 3. . When the temperature sensor 3 senses that the charging of the battery 10 to be charged is completed by the rise of the internal temperature of the battery 10 to be charged, prior to the battery voltage conversion unit 1, the battery temperature detecting unit 4 indicates that the charging is completed. An analog voltage is obtained, and this analog voltage is supplied to the next analog-digital conversion unit 5. The analog-digital conversion unit 5 has
The supplied analog voltage is converted into a digital signal, and this digital output is supplied to the next control unit 6. Upon receiving the supplied digital output, the control unit 6 immediately supplies a switching signal from the switching signal generation unit to the constant current charging circuit 2 to stop the output of the charging current having a constant current value in the constant current charging circuit 2. The charging of the battery 10 to be charged is terminated.

As described above, in the battery charge control device according to the present invention, when the battery voltage (V _BAT ) of the battery 10 to be charged is supplied to the analog-digital converter 5 via the battery voltage converter 1, and Whether the voltage corresponding to the internal temperature of the rechargeable battery 10 is supplied to the analog-digital conversion unit 5 via the temperature sensor 3 or the battery temperature detection unit 4, it is automatically adjusted according to the value of the voltage. And the charged battery 10
Charging can be terminated.

Next, FIG. 2 is a circuit diagram showing one configuration of a main part of the battery charge control device shown in FIG. 1, that is, a circuit configuration diagram showing a first embodiment of the battery voltage conversion unit 1. -Digital conversion unit (A / D) 5 and control unit (CPU)
6 together with 6.

As shown in FIG. 2, the battery voltage conversion unit 1 according to the first embodiment includes a first input terminal 1i 'to which an offset voltage (V _OFF ) is supplied and a battery voltage from the battery 10 to be charged ( V _BAT ) is supplied to the second input terminal 1i ″, a battery voltage (V _OFFBAT ) offset to the negative side is output, and a control terminal 1c is supplied with a control signal from the control unit 6. , A variable voltage dividing circuit 15 and a voltage offset circuit 16. In this case, the variable voltage dividing circuit 1
5 includes a series resistor 17, a shunt resistor 18, and a controllable switch 19. The voltage offset circuit 16 includes an operational amplifier 20, a feedback resistor 21, and a first series resistor 22.
And a second series resistance 23 and a shunt resistance 24. In addition, in addition, in FIG. 2, the same components as the components illustrated in FIG. 1 are denoted by the same reference numerals.

Regarding the circuit configuration of the variable voltage dividing circuit 15, one end of the series resistor 17 is connected to the first input end 1i 'and the other end is one end of the first series resistor 22 of the next voltage offset circuit 16. Connected to. One end of the shunt resistor 18 is connected to one end of the first series resistor 22 similarly to the other end of the series resistor 17, and the other end is connected to one terminal of the controllable switch 19. The other terminal of the controllable switch 19 is grounded, and the control terminal is connected to the control end 1c. Regarding the circuit configuration of the voltage offset circuit 16, the feedback resistor 2
1 is connected between the inverting input and the output of the operational amplifier 20, and the other end of the first series resistor 22 is connected to the inverting input of the operational amplifier 20. The second series resistor 23 has one end connected to the second input end 1i ″ and the other end connected to the non-inverting input of the operational amplifier 20. One end of the shunt resistor 24 is the operational amplifier 2
0 connected to the non-inverting input and the other end connected to ground. The output of the operational amplifier 20 is connected to the output terminal 1o. Further, in the analog-digital converter (A / D) 5, the input end is connected to the output end 1o, and the output end is the control unit (CPU) 6
Is connected to the input terminal of The control unit 6 has a control signal generation unit connected to the control end 1c.

Here, FIG. 3 shows that the battery voltage (V _BAT ) supplied to the battery voltage converter 1 and the offset to the negative side output from the battery voltage converter 1 when the controllable switch 19 is opened and closed. It is a characteristic view which shows the relationship with the battery voltage ( _VOFFBAT ) which was carried out.

In FIG. 3, the vertical axis represents the battery voltage (V _OFFBAT ) offset to the negative side, and the horizontal axis represents the battery voltage (V
_BAT ), the straight line on the right is the characteristic when the controllable switch 19 is opened, and the straight line on the left is the characteristic when the controllable switch 19 is closed.

The operation of the battery voltage converter 1 of the first embodiment having the above-mentioned structure will be described with reference to the overall structure of FIG. 1 and the characteristic diagram of FIG.

A pair of terminals 10 _T1 , 1 of the battery charge control device
When the battery 10 to be charged is connected during 0 _T2, the battery voltage (V _BAT ) of the battery 10 to be charged becomes the second voltage of the battery voltage conversion unit 1.
It is supplied to the input terminal 1i ″, and at the same time, the offset voltage (V
_OFF ) is supplied to the first input terminal 1i ′ of the battery voltage converter 1. At this time, in the variable voltage dividing circuit 15, the offset voltage (V _OFF ) supplied to the first input terminal 1i ′ is _{divided according to the} set voltage dividing ratio, and the next voltage is _divided as the voltage dividing offset voltage (V _DOFF ). It is supplied to the offset circuit 16. Further, in the voltage offset circuit 16, the battery voltage (V _BAT ) supplied to the second input terminal 1i ″ is _{shifted to the} negative side by the _divided voltage offset voltage (V _DOFF ) by the operational amplifier 20 and various resistors 21 to 24. An offset battery voltage (V _OFFBAT ) is generated, and the offset battery voltage (V _OFFBAT ) is supplied to the next analog-digital conversion unit 5 through the output terminal 1o. The analog-digital conversion unit 5 supplies the input terminal. Offset battery voltage (V
_OFFBAT ) is converted from analog to digital, and a digital signal is supplied to the control unit 6 in the next step. The control unit 6 determines the magnitude of the digital signal supplied to the input terminal, generates a control signal for opening and closing the controllable switch 19 according to the magnitude, and operates the constant current charging circuit 2 to determine whether the digital signal is operated or not. A switching signal for switching the operation is generated.

In this case, when the battery voltage (V _BAT ) of the battery 10 to be charged is relatively low at the beginning when the battery 10 to be charged is connected between the pair of terminals 10 _T1 and 10 _{T2 of} the battery charge control device, control is performed. By the control of the section 6, the variable voltage dividing circuit 15
The controllable switch 19 is closed. At this time,
The variable voltage dividing circuit 15 has a form in which a series resistor 17 and a shunt resistor 18 are inserted and connected, and the voltage dividing ratio of the variable voltage dividing circuit 15 is set to a low state (hereinafter, referred to as a first state),
The relationship between the battery voltage (V _BAT ) and the offset battery voltage (V _OFFBAT ) in the battery voltage conversion unit 1 changes as shown by the straight line in FIG.

On the other hand, as the charging target battery 10 is charged and the battery voltage (V _BAT ) of the charging target battery 10 is gradually increased, the voltage value of the offset battery voltage (V _OFFBAT ) becomes a predetermined value (Vs). When it exceeds, the controllable switch 19 of the variable voltage dividing circuit 15 is switched to the open state by the control of the control unit 6. At this time, the variable voltage dividing circuit 15 includes the series resistor 17
Only, the voltage dividing ratio of the variable voltage dividing circuit 15 is set to a high state (hereinafter referred to as the second state), and the battery voltage (V _BAT ) in the battery voltage converting unit 1 is set.
And the offset battery voltage (V _OFFBAT ) change as shown by the straight line in FIG.

Now, when the battery voltage converter 1 is set to the first state, as the battery voltage (V _BAT ) supplied to the battery voltage converter 1 increases, the battery voltage converter 1 increases.
While the offset battery voltage (V _OFFBAT ) output from the controller sequentially increases along a straight line, the control unit 6 determines that the voltage value of the offset battery voltage (V _OFFBAT ) _changes according to the voltage value of the input digital signal. When it is detected that a predetermined value (Vs) slightly smaller than the maximum value (V _OFFBATMAX ) is reached, a control signal is supplied to the control end 1c of the battery voltage conversion unit 1 and the controllable switch 19 of the variable voltage dividing circuit 15 is supplied. Is switched from the closed state to the open state, and the battery voltage conversion unit 1 is switched from the first state to the second state. Offset battery voltage (V _OFFBAT ) output from the battery voltage converter 1 at the time of this switching
Rapidly decreases from a predetermined value (Vs) on the straight line to a corresponding low voltage value on the straight line, and thereafter, as the battery voltage (V _BAT ) supplied to the battery voltage conversion unit 1 increases, the battery voltage Offset battery voltage (V
_OFFBAT ) will gradually rise again along a straight line. Then, when the control unit 6 _detects that the offset battery voltage (V _OFFBAT ) has dropped from the peak voltage value by a very small constant voltage ΔV, based on the voltage value of the input digital signal, the control unit 6 sends the switching signal to the constant current charging circuit 2 To the control end of the constant current charging circuit 2 to switch the constant current charging circuit 2 from the operating state to the non-operating state to stop the charging of the battery 10 to be charged.

In the first embodiment, when the battery voltage converter 1 is switched from the first state to the second state, that is, when the straight line is switched to the straight line, the symbol l in FIG. 3 is used.
_The reason why the overlapping portion of the battery voltage (V _BAT ) as shown by ₀ is provided is that when the state of the controllable switch 19 is switched due to the variation of the component parts, etc., it is temporarily offset from the battery voltage conversion unit 1. This is to prevent the battery voltage (V _OFFBAT ) from being stopped.

As described above, according to the first embodiment, the voltage supplied to the analog-digital converter 5 is not the voltage obtained by dividing the battery voltage (V _BAT ) by the resistance voltage dividing circuit, but the offset battery voltage. Since it is (V _OFFBAT ), the resolution of the analog-digital conversion section 5 is not lowered and the function of the analog-digital conversion section 5 can be fully exerted.

[0044] Further, according to the first embodiment, despite the use of voltage offset circuit 16 in the battery voltage converting unit 1 are offset battery voltage (V _BAT) to the minus side, the battery voltage (V _BAT ) Is a relatively small voltage value, the offset battery voltage (V _OFFBAT ) becomes 0 V, and the analog-to-digital conversion unit 5 cannot detect a battery voltage (V _BAT ) smaller than that. The detection range of the battery voltage (V _BAT ) in the digital conversion unit 5 can be greatly expanded.

Further, according to the first embodiment, since the battery voltage conversion unit 1 substantially uses only the voltage offset circuit 16, the number of input terminals of the analog-digital conversion unit 5 is set to 1. Therefore, the manufacturing cost of the battery charge control device can be reduced without the need for the expensive analog-digital converter 5.

Next, FIG. 4 is a circuit configuration diagram showing another configuration of the main part of the battery charge control device shown in FIG. 1, that is, the second embodiment of the battery voltage conversion unit 1. Digital conversion unit (A / D) 5 and control unit (CPU) 6
It is shown together with.

In this case, the difference between the configuration of the second embodiment shown in FIG. 4 and the configuration of the first embodiment shown in FIG. 2 is that the configuration of the control end in the battery voltage converter 1 is the same as that of the first embodiment. Has a control end 1c to which a control signal is supplied from the control unit 6, whereas the second embodiment is similar to the first control end 1c 'to which the first control signal is supplied from the control unit 6. The second control terminal 1c ″ to which the second control signal is supplied from the control unit 6
The first embodiment includes a series resistor 17, a shunt resistor 18, and a controllable switch 19 with respect to the configuration of the variable voltage dividing circuit 15 in the battery voltage conversion unit 1. On the other hand, in the second embodiment,
Series resistor 17, shunt resistor 18, and controllable switch 19
In addition to this, a second circuit having a resistance value larger than that of the shunt resistor 18 is provided in parallel with the series circuit of the shunt resistor 18 and the controllable switch 19.
There are only two points in which a series circuit of the shunt resistor 25 and the second controllable switch 26 is provided.
There is no structural difference between the embodiment and the first embodiment.

Therefore, with respect to the configuration of the second embodiment, the same components as those shown in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

Further, FIG. 5 shows the battery voltage (V _BAT ) supplied to the battery voltage converter 1 and the output from the battery voltage converter 1 when the controllable switch 19 and the second controllable switch 26 are opened and closed. FIG. 7 is a characteristic diagram showing a relationship with a negatively offset battery voltage (V _OFFBAT ).

In FIG. 5, the vertical axis represents the battery voltage (V _OFFBAT ) offset to the negative side, and the horizontal axis represents the battery voltage (V
_BAT ), the rightmost straight line is the characteristic when both the controllable switch 19 and the second controllable switch 26 are opened, and the straight line next to it is the controllable switch 19
Is the characteristic when the second controllable switch 26 is opened and the second straight line opens the controllable switch 19,
This is the characteristic when the second controllable switch 26 is closed, and the leftmost straight line is the characteristic when both the controllable switch 19 and the second controllable switch 26 are closed.

The operation of the battery voltage conversion unit 1 of the second embodiment having the above structure will be described with reference to FIGS. 1 and 5.

A pair of terminals 10 _T1 , 1 of the battery charge control device
When the battery 10 to be charged is connected during 0 _T2, the battery voltage (V _BAT ) of the battery 10 to be charged is supplied to the second input terminal 1i ″ of the battery voltage converter 1, and at the same time, the offset voltage (V _OFF ) Is supplied to the first input terminal 1i ′ of the battery voltage converter 1. At this time, in the variable voltage dividing circuit 15, the offset voltage (V _OFF ) supplied to the first input terminal 1i ′ is supplied.
_{Is divided} by the set voltage division ratio and supplied to the next voltage offset circuit 16 as a _divided voltage offset voltage (V _DOFF ). In addition, in the voltage offset circuit 16, the second operational amplifier 20 and various resistors 21 to 24
It generates the supplied battery voltage to the input terminal 1i "(V _{BA T)} the partial pressure offset voltage (V _DOFF) component offset by battery voltage in the negative direction (V _OFFBAT), the offset battery voltage (V _OFFBAT) It is supplied to the next analog-digital conversion section 5 through the output terminal 1o.The analog-digital conversion section 5 performs analog-digital conversion of the offset battery voltage (V _OFFBAT ) supplied to the input terminal, and the digital signal is continuously supplied. The control unit 6 discriminates the magnitude of the digital signal supplied to the input terminal and generates a control signal for opening and closing the controllable switch 19 according to the magnitude, or sets the control signal. A switching signal for switching between operation and non-operation of the current charging circuit 2 is generated, etc. The above operation is almost the same as the operation of the first embodiment described above.

In the second embodiment, the battery voltage (V _BAT ) of the to-be-charged battery 10 when the to-be-charged battery 10 is initially connected between the pair of terminals 10 _T1 and 10 _T2 of the battery charge control device is relatively high. When it is low, the control unit 6 controls the variable voltage dividing circuit 15 and the controllable switch 1 of the second controllable switch 26.
9 is closed. At this time, the variable voltage dividing circuit 15 has a form in which the series resistor 17, the shunt resistor 18 and the second shunt resistor 25 are inserted and connected, and the voltage dividing ratio of the variable voltage divider circuit 15 is the lowest (hereinafter, _Is set to the first state), and the relationship between the battery voltage (V _BAT ) and the offset battery voltage (V _OFFBAT ) in the battery voltage converter 1 changes as shown by the straight line in FIG.

Here, as the charging target battery 10 is charged and the battery voltage (V _BAT ) of the charging target battery 10 is gradually increased, the voltage value of the offset battery voltage (V _OFFBAT ) is a predetermined value on a straight line. When (Vs) is exceeded, the controllable switch 19 of the variable voltage dividing circuit 15 opens under the control of the control unit 6,
The second controllable switch 26 is switched to the closed state.
At this time, the variable voltage dividing circuit 15 has a form in which the series resistor 17 and the second shunt resistor 25 are inserted and connected.
The voltage division ratio of 5 is set to a slightly low state (hereinafter referred to as the second state), and the relationship between the battery voltage (V _BAT ) and the offset battery voltage (V _OFFBAT ) in the battery voltage conversion unit 1 is shown in FIG. Changes as shown by the straight line.

Further, as the chargeable battery 10 is charged and the battery voltage (V _BAT ) of the charged battery 10 is gradually increased, the voltage value of the offset battery voltage (V _OFFBAT ) is a linear predetermined value. When it exceeds (Vs), the controllable switch 19 of the variable voltage dividing circuit 15 is controlled by the control unit 6 this time.
Is closed and the second controllable switch 26 is opened. At this time, the variable voltage dividing circuit 15 has a form in which the series resistor 17 and the shunt resistor 18 are inserted and connected, and the voltage dividing ratio of the variable voltage dividing circuit 15 is slightly high (hereinafter, this is referred to as the third state). And the relationship between the battery voltage (V _BAT ) and the offset battery voltage (V _OFFBAT ) in the battery voltage conversion unit 1 changes as shown by the straight line in FIG.

Further, the charging of the battery 10 to be charged progresses,
When the voltage value of the offset battery voltage (V _OFFBAT ) exceeds a predetermined linear value (Vs) as the battery voltage (V _BAT ) of the battery 10 to be charged is sequentially increased, the control unit 6 controls the variable voltage. The controllable switch 19 of the voltage dividing circuit 15 and the second
The controllable switch 26 is switched to the open state. At this time, the variable voltage dividing circuit 15 is in a form in which only the series resistor 17 is inserted and connected, and the voltage dividing ratio of the variable voltage dividing circuit 15 is set to the highest state (hereinafter, this is referred to as the fourth state).
The relationship between the battery voltage (V _BAT ) and the offset battery voltage (V _OFFBAT ) in the battery voltage conversion unit 1 changes as shown by the straight line in FIG.

Now, when the battery voltage conversion unit 1 is set to the first state, as the battery voltage (V _BAT ) supplied to the battery voltage conversion unit 1 increases, the battery voltage conversion unit 1
While the offset battery voltage (V _OFFBAT ) output from the controller sequentially increases along a straight line, the control unit 6 determines that the voltage value of the offset battery voltage (V _OFFBAT ) _changes according to the voltage value of the input digital signal. When it is detected that a predetermined value (Vs) slightly smaller than the maximum value (V _OFFBATMAX ) is reached, a control signal is supplied to the first and second control terminals 1c ′, 1c ″ of the battery voltage converter 1, respectively. With the controllable switch 19 of the variable voltage dividing circuit 15 maintained in the open state, the second controllable switch 26 is switched to the closed state, and the battery voltage conversion unit 1
Is switched from the first state to the second state. At the time of this switching, the offset battery voltage (V _OFFBAT ) output from the battery voltage conversion unit 1 suddenly decreases from a predetermined value (Vs) on the straight line to a corresponding low voltage value on the straight line. As the battery voltage (V _BAT ) supplied to the conversion unit 1 increases, the offset battery voltage (V _OFFBAT ) output from the battery voltage conversion unit 1 again gradually increases along the straight line.

Next, at the time of setting the second state, the output offset battery voltage (V _{OF FBAT} ) of the battery voltage conversion unit 1 increases as the battery voltage (V _BAT ) supplied to the battery voltage conversion unit 1 increases. While climbing sequentially along a straight line,
The control unit 6 changes the voltage value of the input digital signal to
When it is detected that the voltage value of the offset battery voltage (V _OFFBAT ) has reached a predetermined value (Vs) which is slightly smaller than the maximum value (V _OFFBATMAX ), a control signal is _sent to the battery voltage converter 1 for the first and second control. Supply to the ends 1c ', 1c ",
The controllable switch 19 of the variable voltage dividing circuit 15 is switched from the open state to the closed state, the second controllable switch 26 is switched from the closed state to the closed state, and the battery voltage conversion unit 1 is switched from the second state to the third state. Switch. Even during this switching, the offset battery voltage (V
_OFFBAT ) rapidly decreases from the predetermined value (Vs) on the straight line to the corresponding low voltage value on the straight line, and then the battery voltage conversion unit 1
Offset voltage (V _BAT ) output from the battery voltage conversion unit 1 as the battery voltage (V _BAT ) supplied to the
_OFFBAT ) will gradually rise again along a straight line.

Subsequently, when the third state is set, as the battery voltage (V _BAT ) supplied to the battery voltage conversion unit 1 increases, the output offset battery voltage (V
_OFFBAT ) sequentially increases along a straight line, the control unit 6 determines that the voltage value of the offset battery voltage (V _OFFBAT ) is the maximum value (V _OFFBAT ) according to the voltage value of the input digital signal.
_When it is detected that the predetermined value (Vs), which is slightly smaller than _{OF FBATMAX} ), is reached, the control signal is _{sent to the} first of the battery voltage converter 1.
And the second control terminals 1c ′, 1c ″, respectively, to switch the controllable switch 19 and the second controllable switch 26 of the variable voltage dividing circuit 15 to the open state, and to move the battery voltage converter 1 from the third state to the third state. 4. The offset battery voltage (V _OFFBAT ) output from the battery voltage conversion unit 1 also suddenly decreases from the predetermined value (Vs) on the straight line to the corresponding low voltage value on the straight line during this switching. After that, as the battery voltage (V _BAT ) supplied to the battery voltage conversion unit 1 increases,
The offset battery voltage (V _OFFBAT ) output from the battery voltage converter 1 again gradually increases along the straight line.

Further, when the fourth state is set, as the battery voltage (V _BAT ) supplied to the battery voltage conversion unit 1 increases, the output offset battery voltage (V
_OFFBAT ) gradually increases along a straight line, the control unit 6 decreases the offset battery voltage (V _OFFBAT ) from the peak voltage value by a small constant voltage ΔV based on the voltage value of the input digital signal. When this is detected, a switching signal is supplied to the control end of the constant current charging circuit 2, the constant current charging circuit 2 is switched from the operating state to the non-operating state, and the charged battery 10
Stop charging.

Also in the second embodiment, the battery voltage converter 1 is changed from the first state to the second state, from the second state to the third state, and from the third state to the fourth state. When switching from each other, that is, when switching from straight line to straight line, from straight line to straight line, and from straight line to straight line,
The reason why the overlapping portion of the battery voltage (V _BAT ) as shown by the symbol l ₀ in FIG. 5 is provided is that the controllable switch 19 and / or the second controllable switch 26 are switched depending on the variation of the components. This is to prevent the offset battery voltage (V _OFFBAT ) from being temporarily not output from the battery voltage conversion unit 1 when the battery voltage is applied.

As described above, according to the second embodiment, the voltage supplied to the analog-digital converter 5 is not the voltage obtained by dividing the battery voltage (V _BAT ) by the resistance voltage dividing circuit, but the offset battery voltage. Since it is (V _OFFBAT ), the resolution of the analog-digital conversion section 5 is not lowered and the function of the analog-digital conversion section 5 can be fully exerted.

[0063] Further, according to the second embodiment, despite the use of voltage offset circuit 16 in the battery voltage converting unit 1 are offset battery voltage (V _BAT) to the minus side, the battery voltage (V _BAT ) Is a relatively small voltage value, the offset battery voltage (V _OFFBAT ) becomes 0 V, and the analog-to-digital conversion unit 5 cannot detect a battery voltage (V _BAT ) smaller than that. The detection range of the battery voltage (V _BAT ) in the digital conversion unit 5 can be greatly expanded.

Further, according to the second embodiment, since the battery voltage converter 1 substantially uses only the voltage offset circuit 16, the number of input terminals of the analog-digital converter 5 is set to 1. Therefore, the manufacturing cost of the battery charge control device can be reduced without the need for the expensive analog-digital converter 5.

In the first and second embodiments, the shunt resistance 18, the second shunt resistance 25, the controllable switch 19 and the second shunt resistance constituting the variable voltage dividing circuit 15 of the battery voltage converting section 1 are used.
The case where the number of controllable switches 26 is one or two has been described as an example, but the number of these components in the present invention is not limited to one or two, respectively. You can choose one or more.

[0066]

As described in detail above, according to the present invention, the voltage supplied to the analog-digital converter is
Since it is not the voltage obtained by dividing the battery voltage (V _BAT ) by the resistance voltage dividing circuit but the offset battery voltage (V _OFFBAT ), the function of the analog-digital conversion unit is not reduced without lowering the resolution of the analog-digital conversion unit. The effect is that it can be fully exerted.

Further, according to the present invention, the battery voltage (V _BAT ) is converted by using the voltage offset circuit in the battery voltage converter.
Even though the battery voltage (V _BAT ) is a relatively small voltage value, the offset battery voltage (V _OFFBAT ) becomes 0 V, which is smaller than that in the analog-digital conversion unit Since the detection of the battery voltage (V _BAT ) does not become impossible, there is an effect that the detection range of the battery voltage (V _BAT ) in the analog-digital conversion unit can be greatly expanded.

Furthermore, according to the present invention, since the battery voltage conversion unit substantially uses only the voltage offset circuit, the number of input terminals of the analog-digital conversion unit can be set to one. There is also an effect that the manufacturing cost of the battery charge control device can be reduced without requiring an expensive analog-digital conversion unit.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing an overall configuration of a battery charge control device according to the present invention.

FIG. 2 is a circuit configuration diagram showing a first embodiment of a battery voltage conversion unit in the battery charge control device shown in FIG.

FIG. 3 is a battery voltage (V _BAT ) when the voltage dividing ratio of the variable voltage dividing circuit is set to two levels in the first embodiment shown in FIG.
FIG. 6 is a characteristic diagram showing a relationship between the offset voltage and the offset battery voltage (V _OFFBAT ).

4 is a circuit configuration diagram showing a second embodiment of the battery voltage conversion unit in the battery charge control device shown in FIG.

FIG. 5 is a battery voltage (V _BAT ) when the voltage dividing ratio of the variable voltage dividing circuit is set to four levels in the second embodiment shown in FIG.
FIG. 6 is a characteristic diagram showing the relationship between the offset battery voltage (V _OFFBAT ).

FIG. 6 is a block configuration diagram showing a configuration of main parts in a first example of a known battery charge control device.

FIG. 7 is a block configuration diagram showing a configuration of main parts in a second example of a known battery charge control device.

FIG. 8 is a block configuration diagram showing a configuration of main parts in a third example of a known battery charge control device.

[Explanation of symbols]

1 Battery Voltage Converter 2 Constant Current Charging Circuit (Charging Current Generator) 3 Temperature Sensor 4 Battery Temperature Detector 5 Analog-Digital Converter (A / D) 6 Controller (CPU) 7 Constant Voltage Circuit 8 Reset Circuit 9 Light Emission Diode (LED) 10 Battery to be charged 10 _T1 , 10 _T2 Pair of terminals 11 _T1 , 11 _T2 Pair of power supply terminals 12 First buffer diode 13 Second buffer diode 14 Fuse 15 Variable voltage divider circuit 16 Voltage offset Circuit 17 Series resistance 18, 24 Shunt resistance 19 Controllable switch 20 Operational amplifier 21 Feedback resistance 22 First series resistance 23 Second series resistance 25 Second shunt resistance 26 Second controllable switch

Claims (4)

[Claims] 1. A charging current generator that charges a battery to be charged, a battery voltage converter that converts the battery voltage of the battery to be charged, and an analog-digital converter that converts the output analog voltage of the battery voltage converter into a digital signal. The battery voltage conversion unit includes a conversion unit and a control unit that responds to the output digital signal of the analog-digital conversion unit and controls the supply and stop of the output current of the charging current generation unit. A variable voltage dividing circuit that divides the voltage to generate a voltage-divided offset voltage, receives the battery voltage and the voltage-divided offset voltage, and offsets the battery voltage to the negative side by the voltage-divided offset voltage. A voltage offset circuit supplied to the digital conversion unit, wherein the variable voltage dividing circuit controls the control unit according to the magnitude of the battery voltage. A battery charging control device characterized in that the voltage division ratio is switched stepwise. 2. The battery charge control device according to claim 1, wherein the variable voltage dividing circuit has a voltage dividing ratio that can be switched in two stages. 3. The variable voltage dividing circuit is capable of switching the voltage dividing ratio in three or more steps.
The battery charge control device according to. 4. The battery charge control device according to claim 1, wherein the voltage offset circuit is an operational amplifier in which the divided voltage offset voltage is applied to an inverting input and the battery voltage is applied to a non-inverting input. .