JP3235135B2 - battery charger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery charger having an AC adapter with a charging function.

[0002]

2. Description of the Related Art In recent years, small personal computers, home video cameras, and the like have been reduced in size and can be carried anywhere by using a battery as a power source, and are becoming popular.

[0003] In the future, more and more battery-powered equipment will increase,
And economically advantageous rechargeable batteries have come to be used.

[0004] However, a rechargeable battery requires an optimal charging function for a battery charger in order to prolong its life and to sufficiently charge the battery and draw out its battery capacity. Its function is as follows. (1) It can be fully charged in a short time. (2) A sufficient discharge amount can be obtained. (3) Fully chargeable at each temperature. (4) No overcharging.

An example of the above-described conventional battery charger will be described below with reference to the drawings.

FIG. 2 is a block diagram of a conventional battery charger. The AC voltage input from the AC code 1 is converted into a DC voltage by the rectification / smoothing circuit 2 and the voltage is converted.
The other end was added to the primary winding of the transformer 3 in capacitor circuit 4 to switch <br/> quenching. The output from the secondary winding of the transformer 3 is rectified by a rectifier 17 into a secondary DC voltage, and the voltage / current is detected by an output voltage / output current control circuit 5 and converted to a specified voltage via a control signal 15 via a control signal 15. The switching pulse width of the circuit 4 is controlled. The converter circuit 4 and the output power
Switching regulation by voltage / output current control circuit 5
Data. The controlled secondary DC voltage is supplied from a terminal 18 to a device 8 such as a video camera.

Next, the battery charging circuit is connected to the secondary side D.
The C voltage is controlled by the transistor 6, and its output is supplied with a charging current to the + side of the battery 9 via the battery charging terminal 19. The negative side of the battery 9 is connected to the circuit ground via the terminal 20 and is connected to the transformer 3 through the current detecting resistor 11.
To the other end of the secondary winding. Whether the battery 9 is connected or not is determined by the A / D converter of the microcomputer 7 from the battery charging terminal 19 via the detection signal line 13 and the transistor 6 is turned on. The constant current required for charging the battery is obtained by converting the terminal voltage of the current detection resistor 11 to the output voltage
The input to the output current control circuit of the output current control circuit 5 can control the converter circuit 4.

Here, a low resistance is used for the current detection resistor 11 so as not to affect the output voltage. Therefore, the potential difference between both ends becomes several mV, and the input offset of the operational amplifier cannot be ignored when amplifying by the operational amplifier in the output voltage / output current control circuit 5. Therefore, a method of using an expensive operational amplifier with a small input offset or canceling with a volume has been adopted. Here, the transformer 3, the converter circuit 4, the rectifier 17, and the output voltage / output current control circuit 5 constitute a switching regulator.

[0009]

As described above, conventionally, when the voltage detected by the current is amplified by the operational amplifier, the input offset voltage of the operational amplifier cannot be ignored. Therefore, a method of using an expensive operational amplifier with a small input offset or canceling with a volume has been adopted. Microcomputer 7,
There are many circuit components such as the output voltage / output current control circuit 5 and it is difficult to reduce the size. Further, there is a problem that the accuracy of charging the battery 9 is not improved and the cost cannot be reduced.

In view of the above problems, the present invention controls the offset voltage of an operational amplifier for detecting the output current of a switching regulator, and controls the state of the switching regulator by detecting the A / D converted data by detecting the output voltage and the output current. Means for controlling the switching regulator by controlling the D / A-converted voltage by a microcomputer to control the switching regulator, and processing and controlling the output voltage to match the A / D-converted data. It is intended to provide a battery charger characterized in that it can be made into a one-chip IC.

[0011]

In order to solve the above problems, a battery charger according to the present invention is provided with a voltage supply.
To the battery by turning on / off the transistor
On the other hand, the circuit and the circuit where charge ON / OFF can be switched
A logic operation unit to which the supplied voltage is input
Supply to circuit based on instruction from arithmetic processing unit
An output current control circuit for controlling the current.
With the data turned off, the voltage flowing through the circuit
In the logical operation unit, and then
With the power supply turned off, raise the voltage supplied to the circuit.
The voltage supplied to the circuit at this time is referred to as data 2
Stored in the logical operation unit,
Process so that data 2 matches data 1 and match
The processing value of the logical operation unit at the time of
The load is connected to the
When the data is turned on, the voltage supplied to the circuit and the data 3
Is added to the output current control circuit,
By changing the voltage supplied to the circuit,
Control.

[0012]

According to the present invention, the offset voltage of the operational amplifier for detecting the output current of the switching regulator is controlled by the above-described configuration, the output voltage is detected and A / D converted data and the output current are detected to control the state of the switching regulator. Means for controlling the switching regulator by controlling the D / A-converted voltage by a microcomputer to control the switching regulator, and processing and controlling the output voltage to match the A / D-converted data. Is automatically canceled, the battery can be charged with high accuracy, and the cost can be reduced by using the above-mentioned means as a one-chip IC.

[0013]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a control section of a battery charger according to one embodiment of the present invention. The basic configuration is the same as that described in the conventional example, and the description will be focused on the features of the present invention. Therefore, the same parts as those in the conventional example will be described with the same reference numerals.

In FIG. 1, the AC cord 1, the rectifying / smoothing circuit 2, the converter circuit 4, and the primary winding of the transformer 3 are omitted, and the transformer 3, converter circuit 4, output voltage / output current control circuit 5 Constructs a switching regulator. A rectifier 17 converts the secondary winding of the transformer 3 of the switching regulator into a secondary DC voltage,
The voltage is divided by a resistor 24 and a resistor 25 to obtain a reference voltage 4
The control signal 1 is detected by the output voltage control circuit 35 of the output voltage / output current control circuit 5 which compares the control signal 1 with the control signal 1 so that the specified voltage is obtained.
The switching pulse width of the primary-side converter circuit 4 is controlled via the photocoupler 5 and the photocoupler 40. The controlled secondary DC voltage is supplied from a terminal 18 to a device such as a video camera.

Next, the battery charging circuit is connected to the secondary side D.
The ON / OFF control of the C voltage is performed by the transistor 6, and the output of the C voltage is supplied to the (+) side of the battery via the battery charging terminal 19. From the (−) side of the battery to the ground of the circuit via the terminal 20, the current detection resistor 1
1 is connected to the other end of the secondary winding of the transformer 3. Whether the battery 9 is connected or not is determined by the A of the microcomputer 7 via the detection signal line 13 from the battery charging terminal 19.
The determination is made by the / D converter, and the transistor 6 is turned on. The constant current required for battery charging is the current detection resistor 11
Is divided by the resistors 28 and 30 and the resistors 29 and 31 and input to the output current control circuit 36 to control the converter circuit 4 for controlling the primary-side switching pulse width via the control signal 15 and the photocoupler 40. . Here, in the current control, when the charging current for charging the battery is 1.3 A, when the current detection resistor 11 is 0.1Ω, the terminal voltage Vr of the current detection resistor 11 is Vr = 1.3 A × 0.05Ω = 0. 06
5 V = 65 mV, so that the differential input terminal voltage of the output current control circuit 36 becomes OV when the voltage is equal to or higher than the Vr voltage, and the voltage dividing ratio between the resistors 28 and 30 and the resistors 29 and 31 is designed and operated. It is.

Next, it is necessary to supply a charging current of about 0.1 A to the charged battery in order to supplement self-discharge. The terminal voltage Vr at that time is 5 mV, but when amplifying by the operational amplifier of the output current control circuit 36, the input offset of the operational amplifier, the voltage dividing resistors 28, 30 and the resistors 29, 3
The variation of 1 cannot be ignored. Therefore, a method of using an expensive operational amplifier having a small input offset or canceling the input offset by using the resistor 28 or 29 as a volume has been adopted.

Therefore, according to the present invention, the data from the logical operation unit (ALU) 39 in the microcomputer unit 7 is converted into an analog voltage by the D / A converter 37, and the voltage dividing resistors 28 and 30 are connected via the resistor 27. Connect to a point. As a result, the input offset of the operational amplifier can be canceled by changing the data from the logical operation unit (hereinafter referred to as ALU) 39 in the microcomputer unit 7 instead of canceling the input offset of the operational amplifier by the conventional volume. Then, the input offset of the operational amplifier can be automatically and accurately performed.

First, the transistor 6 is turned off, and when there is no load on the terminal 18, the secondary DC voltage is reduced.
The resistances 24 and 25 are set so as to reach a specified voltage (for example, 10 V).
Set the voltage dividing ratio with, compare with the reference voltage 41 and control the output voltage
The circuit 35 is operated. The secondary DC voltage obtained as a result is divided by the resistors 22 and 23, the voltage is converted into data by the A / D converter 38, and the data “DATA1” is converted to AL.
It is stored in U39. Current flowing through the current detection resistor 11 at this time and I ₀ by the sum of such output current control circuit 36 and the output voltage control circuit 35 and the microcomputer 7.

Here, the secondary side DC voltage is defined as the above specified voltage.
If set high Ri current flowing through the current detection resistor 11 is utilized to increase from I _0. Charge battery 9
Before powering, D / A conversion from ALU39 of microcomputer unit 7
By changing the data to the heater 37 , the resistors 28, 29
The output current control circuit 36 increases the AC voltage of the
Switching to the control circuit 35 to raise the secondary DC voltage
Let them work. Here, the value “DATA2” obtained by dividing the increased secondary-side DC voltage by the resistors 22 and 23 and converting the voltage into data by the A / D converter 38 is the previous “DATA2”.
1. Next , the value of “DATA2” is changed to “DAT”.
Small data to the D / A converter 37 to match the A1 "
The microcomputer unit 7 is programmed so as to change and send each time . The value of "DATA2""DATA1" match the secondary-side DC voltage is the initial I ₀ is also the current flowing through the current detection resistor 11 becomes the above specified voltage. If "DATA3" to the D / A converter 37 at this time is stored and used as a reference, the input offset of the operational amplifier of the output current control circuit 36 is canceled.

When a charging current of about 0.1 A is supplied as a supplement to the self-discharge of the charged battery, the current terminal Vr flowing through the current detection resistor 11 supplies 5 mV equivalent to the D / A converter 37. What is necessary is just to add to DATA3 ". In FIG. 1, reference numeral 34 denotes a resistor, reference numeral 42 denotes a reference power supply for supplying power to the microcomputer unit 7, and reference numeral 43 denotes a capacitor for stabilizing the power of the reference power supply 42.

From the above, the output current control circuit 3
The input offset of the operational amplifier No. 6 does not require precision, so it can be made by the same MOS process as the microcomputer.
The microcomputer and the control circuit can be integrated into one chip.

[0023]

According to the present invention as described above, according to the present invention, the configuration described above, by automatically canceling the offset of the op amp, and enables good battery charging accuracy, and the means on one chip IC Cost reduction is also possible, which is of great industrial value.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a main part of a battery charger according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional battery charger.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 AC code 2 Rectifier / smoothing circuit 3 Transformer 4 Converter circuit 5 Output voltage / output current control circuit 6 Transistor 7 Microcomputer 8, 9 Battery 11 Current detection resistor 13 Detection signal line 15 Control signal 16 Output current detection 17 Rectifier 18 DC voltage Terminal 19 Battery charging terminal 20 Negative terminal 22, 23, 24, 25, 27, 28, 29, 30, 3
Reference Signs List 1,34 Resistance 35 Output voltage control circuit 36 Output current control circuit 37 D / A converter 38 A / D converter 39 Logical operation unit (ALU) 40 Photocoupler 41 Reference voltage

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H02J ^7/ 00-7/12 H02J ⁷ /34-7/36

Claims (1)

(57) [Claims] 1. A transistor for receiving a voltage and supplying an O
Charge ON for battery (9) by N / OFF
/ OFF switching circuit and the circuit supplied to the circuit
A logic operation unit (39) to which a voltage is input and the center
Based on an instruction from the arithmetic processing unit (39),
Output current control circuit (3
6), and with the transistor (6) turned off,
The logical operation unit, wherein the voltage flowing through the path is data 1
(39), and then the transistor (6) is turned off.
To increase the voltage supplied to the circuit,
The voltage supplied to the logic operation unit as data 2.
(39), and the data 2 is decompressed by the logical operation processing unit (39).
Data 1 and the logic
The processing value of the arithmetic unit (39) is referred to as data 3 as described above.
In the logical operation unit (39), the load (9) was connected and the transistor (6) was turned on.
The difference between the voltage supplied to the circuit and the data 3
By adding the current to the output current control circuit (36).
Changes the voltage supplied to the circuit and flows to the load
Battery charger that controls voltage .