JP2786973B2 - Power supply circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit, and more particularly, to an output voltage of a power supply battery which is adjusted and used as an operating voltage of a load voltage while the output voltage of the power supply battery is high. In this case, the present invention relates to a power supply circuit suitable for a barcode scanner, which adjusts a boosted voltage and uses the adjusted boosted voltage as an operation voltage of the load voltage.

[0002]

2. Description of the Related Art Generally, in a touch bar code scanner using a CCD (Charge Coupled Device) line sensor for reading a bar code, a relatively high voltage (for example, 12 V) is required to drive the CCD line sensor.
And a relatively low stabilizing voltage (for example, 5 V), and if the voltages fluctuate, particularly if the stabilizing voltage of 5 V fluctuates, the bar code in the CCD line sensor is changed. The reading sensitivity changes or the reading operation becomes unstable.

The above-mentioned bar code scanner is often of a handy type having a built-in battery power source for driving. In such a bar code scanner driven by a battery power source, usually, the bar code scanner of the battery power source is used. Output voltage is DC-
The voltage is boosted by a DC converter to obtain the voltage of 12 V. On the other hand, the voltage of 12 V is lowered by a series voltage regulator, and the voltage is stabilized to obtain the voltage of 5 V.

FIG. 5 is a block diagram showing an example of the overall configuration of a conventional bar code scanner.

In FIG. 5, 50 is a one-chip microcomputer (microcomputer), 51 is an LED (light emitting diode) drive circuit, 52 is an LED array, 53 is a CCD line sensor, 54 is an amplifier circuit, 55 is a binarization circuit, 56 is an oscillation circuit for generating an operation clock signal, and 57 is an infrared LE
D drive circuit, 58 is an infrared LE that generates a remote control code
D and 59 are a key matrix, 60 is a battery power source, 61 is an intermittent switch, 62 is a DC-DC converter for boosting, 63 is a series voltage regulator, and 64 is a bar code.

Then, the projection light is supplied from the LED array 52 to the bar code 64, and the reflected light from the bar code 64 is scanned and read by the CCD line sensor 53. In this case, of the two voltages 12V and 5V for operating the CCD line sensor 53, 12V is the power supply battery 6
The output voltage of 0 is obtained by the output of the DC-DC converter 62 for increasing the output voltage, and 5 V is obtained by lowering the 12 V by the series voltage regulator 63 and stabilizing the voltage.

[0007] The bar code scanner having the above-described structure generally performs the following operation.

First, when no key is operated on the key matrix 59, the bar code scanner is in the stop mode, at this time the microcomputer 50 stops operating, and the oscillation circuit 56 also oscillates the operation clock signal. Operation has been stopped.

Next, when any key in the key matrix 59 is operated, the microcomputer 50 starts operating, and the oscillation circuit 56 starts oscillating the operation clock signal. Here, the key command by the key operation is the transmission of the remote control code, that is, the infrared LE.
When the remote control code is only transmitted from D58, the microcomputer 50 does not send a switch closing signal to the intermittent switch 61, so that the intermittent switch 61 is kept open, and the DC-DC converter 62 and the serial voltage The adjuster 63 does not perform any operation.
The line sensor 53 also does not read the barcode 64. When the transmission of the remote control code is completed or completed, the microcomputer 50 stops all operations, the oscillation circuit 56 also stops the oscillation operation of the operation clock signal, and returns to the original stop mode.

Subsequently, when one of the keys in the key matrix 59 is operated again, the operation of the microcomputer 50 is started, and the oscillation circuit 56 starts oscillating the operation clock signal. Here, when the key command by the operation of the key is scanning reading of the bar code 64, a switch closing signal is supplied from the microcomputer 50 to the intermittent switch 61, thereby closing the intermittent switch 61. Regulator 62 and series voltage regulator 6
3 sequentially start the operation, and operating voltages of 12 V and 5 V are supplied to the CCD line sensor 53. At this time, since the microcomputer 50 supplies a start pulse and a sensor clock signal following the start pulse to the CCD line sensor 53, the CCD line sensor 53 starts scanning and reading the barcode 64. When the scanning of the bar code 64 by the CCD line sensor 53 is completed, the microcomputer 50 stops all operations, and the switch closing signal supplied from the microcomputer 50 to the intermittent switch 61 is interrupted. Is opened, the DC-DC converter 62 and the series voltage regulator 63 become inactive,
The power supply to the CCD line sensor 53 is cut off, and the operation returns to the original stop mode.

[0011]

However, the power supply circuit in the known bar code scanner uses the DC-DC converter 62 to temporarily output the output voltage of the battery power supply 60.
V and the above-mentioned 1
By stepping down 2V to 5V, two voltages 12
V and 5 V, the battery power supply 60
It is necessary to use a large capacity nickel-cadmium (NiCd) battery or lead-acid battery, so that not only the power supply but also the barcode scanner as a whole becomes expensive and bulky. However, if a secondary battery such as a lead storage battery is used, there are problems that a dedicated charger is separately required and that much time is required for charging.

In order to avoid this problem, when a relatively small-capacity battery is used as the battery power source 60, another problem arises that the life of the battery is extremely shortened due to severe consumption of the battery.

In order to avoid the above problem, the present inventor has selected an output voltage of a battery power supply and a boosted voltage from a DC-DC converter in addition to a series voltage regulator for supplying an operating voltage to a load device. And a voltage detector for detecting the output voltage of the battery power supply, wherein the voltage detector detects that the output voltage of the battery power supply has dropped below a predetermined value. A power supply circuit that switches the switch to the boosted voltage side when the detection output is generated, thereby improving the use efficiency of the battery power supply and extending the life of the battery power supply. doing.

Although the power supply circuit according to this proposal can improve the utilization efficiency of the battery power supply and extend the life of the battery power supply, the output voltage of the battery power supply is detected on the output side of the battery power supply. Therefore, in the voltage detected by the voltage detector, it is necessary to consider a voltage drop generated in the series voltage regulator and other parts, and the voltage drop is a load fluctuation. In addition, there is a problem that it is necessary to design a circuit with a margin for such changes due to the characteristics of the transistors used.

The present invention has been made in order to eliminate all of the above-mentioned problems, and an object of the present invention is to improve the efficiency of use of a battery power source and to extend the battery life even when a relatively small capacity battery is used. An object of the present invention is to provide a power supply circuit that can be extended and that is not affected by the internal voltage drop or the load state.

[0016]

To achieve the above object, the present invention provides a DC-DC converter for boosting an output voltage of a battery power supply to generate a boosted voltage, and receiving an output voltage of the battery power supply. A first input terminal for receiving the boosted voltage;
Input terminal and a first terminal equal to the operating voltage of the load device.
And a voltage adjusting circuit having an output terminal for selectively outputting either one of the first voltage and the second voltage slightly lower than the operating voltage, wherein the voltage adjusting circuit comprises:
A first voltage regulator connected between an input terminal and the output terminal; a second voltage regulator and a switch connected in series between the second input terminal and the output terminal; A voltage detector connected to an output terminal, wherein the first voltage regulator has a first voltage whose output voltage is equal to the operating voltage, and the second voltage regulator has an output voltage lower than the operating voltage. A slightly lower second voltage and the voltage detector are respectively selected and configured so that a detection voltage becomes a third voltage intermediate between the first and second voltages, and the switching is performed by a detection output of the voltage detector. First means for interrupting the regulator and selectively activating or deactivating the second voltage regulator.

According to another aspect of the present invention, there is provided a DC-DC converter for boosting an output voltage of a battery power supply to generate a boosted voltage, and a first input terminal for receiving the output voltage of the battery power supply. A second input terminal for receiving the boosted voltage, and an output terminal for selectively outputting one of a first voltage equal to an operation voltage of the load device and a second voltage slightly lower than the operation voltage. A voltage adjusting circuit having a first PNP transistor connected between the first input terminal and the output terminal; a second PNP transistor connected between the first input terminal and the output terminal; A second PNP transistor connected between the second input terminal and a reference potential point, and a first voltage equal to the operating voltage and a second voltage slightly lower than the operating voltage. Generate voltage Voltage breeder and, the first voltage and the first P output voltage is compared with the said output terminal
A first operational amplifier that supplies a comparison output to an NP transistor; and a second operational amplifier that compares the second voltage with an output voltage of the output terminal and supplies a comparison output to the second PNP transistor. Second means.

[0018]

According to each of the above-mentioned means, the first voltage for adjusting the output voltage of the battery power supply to generate a first voltage, for example, 5V, which is equal to the operation voltage of the load device (the line sensor operation voltage).
And a second voltage that is slightly adjusted to be lower than the first voltage, for example, 4.8 V by adjusting the output voltage of the voltage regulator or the output boosted voltage of the DC-DC converter. The output voltage of the voltage regulator is selectively supplied as an operating voltage to a load device (CCD line sensor for a bar code reader). On the other hand, the operating voltage supplied to the load device (CCD line sensor) is monitored and detected by a voltage detector. At this time, the voltage detector detects that the operating voltage is equal to the first voltage (5V) and It works to detect that the voltage has dropped to a third voltage intermediate the second voltage (4.8 V), for example, 4.9 V or less.

Now, while the battery power is relatively new and its output voltage is high, the output voltage of the first voltage regulating circuit, that is, the operating voltage is sufficiently 5 V, so that the voltage detector detects the voltage. The output voltage is adjusted by the first voltage adjustment circuit without generating an output, and the adjusted output voltage (5 V) is continuously supplied to the load device (CCD line sensor) as the operating voltage.

Next, assuming that the battery power supply has been used for a relatively long period of time and its output voltage has dropped, and that the output voltage of the first voltage regulating circuit has dropped to 4.9 V or less, the voltage detector Detects the voltage drop and generates a detection output at the output. This detection output is supplied to the switch to close it, and to activate the second voltage regulator.
The output boosted voltage of the DC converter is adjusted by the second voltage adjuster, and the adjusted output voltage (4.8 V) is supplied to the load device (CCD line sensor) as the operating voltage.

As described above, the source of the operating voltage supplied to the load device (CCD line sensor) is switched according to the value of the output voltage of the battery power supply, so that the efficiency of use of the battery power supply is improved. And the life of the battery power supply can be extended.

Further, at the time of the switching, the load device (C
Since the operating voltage supplied to the CD line sensor is directly monitored and detected, the switching can be performed without being affected by the internal voltage drop or the load state.

[0023]

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

FIG. 1 is a circuit diagram showing a first embodiment in which a power supply circuit according to the present invention is applied to a bar code scanner. FIG. 2 is a diagram showing a configuration of a bar code scanner provided with the power supply circuit. FIG. 3 is a block diagram showing

In FIGS. 1 and 2, 1 is a voltage adjusting circuit, 2 is a first voltage adjuster, 3 is a second voltage adjuster,
Is a voltage detector, 5 is a switch, and 6 and 7 are first buffers.
And the second Schottky diode 8 is a DC-
9 is a battery power supply, 10 is a one-chip microcomputer (microcomputer), 11 is an LED (light emitting diode) drive circuit, 12 is an LED array, 13 is a CCD line sensor serving as a load device, 14 is an amplifier circuit, 15 Is a binarization circuit, 16 is an oscillation circuit for generating an operation clock signal,
17 is an intermittent switch, 18 is an infrared LED drive circuit, 19
Is an infrared LED for generating a remote control code, 20 is an operation key matrix, 21 is a bar code, and 22 and 23 are third and fourth Schottky diodes for supplying drive power to the microcomputer 10.

The voltage adjustment circuit 1 includes the first and second
Input terminal I₁, I_TwoAnd an output terminal O.
A first voltage equal to the operating voltage of the in-sensor, for example 5
A first voltage regulator 2 for generating V;
A second voltage slightly lower than (5V), for example, 4.8
A second voltage regulator 3 for generating V;
(5V) and a voltage intermediate between the second voltage (4.8V),
For example, a voltage detector 4 that detects a voltage of 4.9 V or less
And the second voltage regulator 3 selectively supplies a boost DC-DC
A switching unit 5 for supplying an output boosted voltage of the switching unit 8;
The interference on the output side of the pressure regulator 2 and the second voltage regulator 3 is eliminated.
First and second Schottky diodes for a buffer to be removed
6 and 7. The input of the first voltage regulator 2 is
1 input terminal I ₁The input of the second voltage regulator 3 is switched
The second input terminal I_TwoConnected to
The output of the first voltage regulator 2 is a first Schottky diode
The output of the second voltage regulator 3 is connected to the output terminal O via the
The force is also output through the second Schottky diode 7
Connected to O. The input of the voltage detector 4 is connected to the output terminal O.
The output is connected to the control end of the switch 5. No.
1 input terminal I₁Is the second input on the output side of the battery power supply 9.
Terminal I_TwoAre connected to the output side of the DC-DC converter 8 for boosting.
The output terminal O is connected to the low level of the CCD line sensor 13.
Connected to stable voltage (5V) supply terminal.

The boost DC-DC converter 8 boosts the output voltage of the battery power supply 9 to generate a boosted voltage input. The input is connected to the output side of the battery power supply 9. The output is the high voltage (1
2V) Connected to the supply terminal.

In addition, the one-chip microcomputer 10 has an LE
An LED emission drive pulse to the LED array 12, a sensor clock signal and a start pulse to the CDD line sensor 13, an oscillation start signal to the oscillation circuit 16, a switch closing signal to the line sensor intermittent switch 14 via the D drive circuit 11, Infrared LED 19 via infrared LED drive circuit 18
Are configured to supply remote control codes to the
On the other hand, the bar code reading signal obtained by the CDD line sensor 13 is received through the amplifier circuit 14 and the binarization circuit 15, and the operation clock signal from the oscillation circuit 16 and the key command from the key matrix 20 are respectively received. It is configured to receive.

In the above configuration, the overall operation of the barcode scanner shown in FIG. 2 is almost the same as the overall operation of the above-described known barcode scanner.
The overall operation will be roughly described as follows.

First, when none of the keys in the operation key matrix 20 is operated, the bar code scanner is in the stop mode. In the stop mode, the microcomputer 10 is in a state where all operations are stopped. In this case, the oscillation circuit 16 also stops oscillating the operation clock signal.

In this state, the operation key matrix 2
When any of the keys 0 is operated, the microcomputer 10
Starts operating and supplies an oscillation start signal to the oscillation circuit 16, so that the oscillation circuit 16 generates an operation clock signal. In this case, if the type of the key command by the operation of the key is a remote control code transmission, that is, if the command is only to transmit the remote control code from the infrared LED 18, the microcomputer 10 controls the infrared LED drive circuit 18. The remote control code is supplied to the infrared LED 19 via the remote control code. At this time, since the microcomputer 10 does not send the switch closing signal to the intermittent switch 17 and the intermittent switch 17 is maintained in the open state, the microcomputer 10 normally operates in the step-up DC-DC converter 8 and the voltage adjusting circuit 1. Is not performed and CC
Since no operating voltage is supplied to the D line sensor 13, C
The bar code 18 is not scanned and read by the CD line sensor 13. When the transmission of the remote control code is completed or completed, the microcomputer 10 stops all operations, the oscillation circuit 16 also stops its operation clock oscillation operation, and returns to the original stop mode.

Subsequently, again, the operation key matrix 20
Is operated, the microcomputer 10 starts operating and supplies an oscillation start signal to the oscillation circuit 16 as before, and the oscillation circuit 16 generates an operation clock signal. . In this case, if the type of the key command by the operation of the key is the scan reading of the bar code 21, the microcomputer 10 supplies a switch closing signal to the intermittent switch 17, thereby setting the intermittent switch 17 to the closed state. Therefore, both the step-up DC-DC converter 8 and the voltage adjustment circuit 1 start normal operation, and the 12V and 5V
Is supplied to the CCD line sensor 13. At the same time, the microcomputer 10 controls the CCD line sensor 13
, A start pulse and a sensor clock signal following the start pulse are supplied, so that the CCD line sensor 13 enters the scanning reading state of the bar code 21 and the bar code 2 is read.
Scan scanning of No. 1 is started. When the scanning of the bar code 21 by the CCD line sensor 13 is completed, the microcomputer 10 stops all operations. As a result, the supply of the switch closing signal to the intermittent switch 17 is stopped, the intermittent switch 17 is opened, and the DC-DC converter 8 for boosting and the voltage adjustment circuit 1 are both deactivated, and the CCD The supply of operating power to the line sensor 13 is cut off, and the CCD line sensor 13 is also disabled. Further, the oscillation circuit 16 also stops oscillating the operation clock signal, and returns to the original stop mode state.

Next, the operation of the voltage adjusting circuit 1 of the bar code scanner will be described.

Now, when the output voltage of the battery power supply 9 is relatively high, for example, 6.0 V or more, at a relatively new time of the battery power supply 9 (time just after replacement), the output voltage of the battery power supply 9 (for example, , above 6.0V) is supplied from the first input terminal I ₁ in the first voltage regulator 2, first
In the voltage regulator 2, the output voltage is adjusted so as to be equal to the operating voltage of the CCD line sensor 13, for example, 5 V, and the adjusted stabilized voltage is applied to the first Schottky switch connected in the forward direction. It is led to the output terminal O via the diode 6 and supplied to the CCD line sensor 13 from the output terminal O. In this case, the output voltage of the output terminal O indicates 5 V, the voltage detector 4 does not generate a detection output, and the switch 5 remains open.
The second voltage regulator 3 does not perform any operation, and only the voltage of 5 V from the first voltage regulator 2 is applied to the CCD line sensor 1.
3.

On the other hand, the use time of the battery power source 9 becomes longer,
When the output voltage of the battery power supply 9 decreases, for example, to 5.5 V or less, the adjustment voltage obtained for the output of the first voltage regulator 2 cannot maintain 5 V and gradually decreases. Become like When the adjustment voltage decreases by a considerable amount, for example, to about 4.8 V, the voltage detector 4 detects the adjustment voltage,
Since the detection output is supplied to the switch 5 and the switch 5 is immediately closed, the output boost voltage (for example, 12 V) of the boost DC-DC converter 8 is supplied to the second voltage regulator 3. Then, a regulated voltage of slightly lower than 5 V, for example, 4.8 V is output from the output. And
The regulated voltage of 4.8 V is led to the output terminal O via the second Schottky diode 7 which is also connected in the forward direction, and is supplied to the CCD line sensor 13 from the output terminal O.

Here, from the output terminal O to the CCD line sensor 13, the adjustment voltage (4.8 V) obtained by the first voltage regulator 2 and the adjustment voltage obtained by the second voltage regulator 3 (4.8 V) is supplied, but at the beginning of the switching operation of the switch 5, the higher voltage of the two adjustment voltages (4.8 V) is supplied to the CCD line sensor 13. However, the adjustment voltage obtained by the first voltage regulator 2 gradually decreases as the output voltage of the battery power supply 9 decreases, so that the adjustment voltage obtained by the second voltage regulator 3 is selectively applied to the CCD. The power is supplied to the line sensor 13.

In this case, the operating voltage is supplied to the microcomputer 10 via the third and fourth Schottky diodes 22 and 23 connected back to back. When the output voltage of the battery power supply 9 is lower than 5V, the output voltage of the battery power supply 9 is supplied to the microcomputer 10 via the third Schottky diode 22.
Is supplied to the microcomputer 10 via the fourth Schottky diode 23.

As described above, according to this embodiment, while the output voltage of the battery power supply 9 is high, the output voltage is adjusted by the first voltage regulator 2 to a voltage equal to the operating voltage of the CCD line sensor 13. The regulated voltage is supplied to the CCD line sensor 13 as a line sensor operating voltage. When the output voltage of the battery power supply 9 decreases, the output boosted voltage of the boosting DC-DC converter 8 is increased by a second voltage regulator. In step 3, the voltage is adjusted to be slightly lower than the operating voltage, and the adjusted voltage is used as a line sensor operating voltage in the CCD.
Since the power is supplied to the line sensor 13, the use efficiency of the battery power supply 9 can be improved, and the life of the battery power supply 9 can be extended.

Also, since the output voltage of the battery power supply 9 is monitored and detected at the supply end to the CCD line sensor 13, the output voltage can be monitored and detected without considering the internal voltage drop and load fluctuation. Can be performed.

FIG. 3 is a circuit configuration diagram showing an example of a specific configuration of each component constituting the voltage adjustment circuit.

In FIG. 3, reference numerals 24 ₂ , 24 ₃ , 24 ₄ denote operational amplifiers, 25 ₂ , 25 ₃ , 25 ₄ denote constant current sources, 26
₂ , 26 ₃ and 26 ₄ are Zener diodes, 27 ₂ and 2
7 ₃ and 27 ₅ are output npn transistors, 28 ₂ and 28
_3, 28 _4, 28 _5, 29 _2, 29 _3, 29 _4, 29 ₅
Is a resistor, and the same components as those shown in FIG. 1 are denoted by the same reference numerals.

[0042] Then, the first voltage regulator 2, an operational amplifier 24 _2, a reference voltage generating circuit comprising a noninverting connected to the input a constant current source 25 ₂ and Zener diode 26 ₂ of the series circuit of the operational amplifier 24 ₂ , a transistor 27 ₂ having a base connected to the output of the operational amplifier 24 ₂ is composed of a resistor connected 28 _2, 29 ₂ and between the inverting input transistor 27 and _second emitter and the operational amplifier 24 _2, first voltage regulator 2 is powered by the output voltage of the battery power source 9 is configured as voltage adjusted from the emitter of the transistor 27 ₂ is output. Note that the second voltage regulator 3 has the same configuration as the first voltage regulator 2. The voltage detector 4 includes the operational amplifier 2
4 ₄ and a reference voltage generating circuit comprising a series circuit of the constant current sources 25 ₄ and Zener diode 26 ₄ connected to the inverting input of the operational amplifier 24 _4, the input end and op-amp 24 ₄
Consists of a non-inverting input of the connected a resistor 28 _4, 29 ₄ during, the output voltage of the voltage regulating circuit 1 is supplied to the input terminal, so that the detection output is taken from the output of the operational amplifier 24 ₄ It is configured. The switch 5 is composed of a switching transistor 27 ₅ and resistors 28 ₅ and 29 ₅ connected to its base.
Detection outputs are configured to be supplied to the base of the transistor 27 _5.

In the above configuration, in the first voltage regulator 2 and the second voltage regulator 3, the operational amplifier 24 ₂ ,
24 _3, constant current source 25 _2, 25 ₃ and the Zener diode 26 _2, 26 ₃ which the output reference voltage of the reference voltage generating circuit composed of the transistors 27 _2, 27 ₃ resistance emitter output voltage of 28 _2, 29 ₂ and 28 _3, 29 ₃ performs adjustment and divided voltage as equal, regulated voltage of 5V from the first voltage regulator 2 is adjusted 4.8V from the second voltage regulator 3 It operates to output the output voltage. In the voltage detector 4, the operational amplifier 24
_4, the output reference voltage of the reference voltage generating circuit comprising a constant current source 25 ₄ and Zener diode 26 ₄ which were voltage and the voltage comparison obtained by dividing the input voltage by the resistors 28 _4, 29 _4, pressure was the fraction It operates to generate a low level detection output when the voltage is lower than the output reference voltage. Switch 5
In the transistor 27 ₅ is made from the voltage detector 4 to the base only on state when the detection output of the low level is supplied, the step-up DC - the output boosted voltage of the DC converter 8 and the second voltage It operates to supply the input of the regulator 3.

FIG. 4 is a block diagram showing a second embodiment in which the power supply circuit according to the present invention is applied to a bar code scanner.

In FIG. 4, reference numeral 30 ₁ denotes a first operational amplifier, 30 ₂ denotes a second operational amplifier, and 31 ₁ denotes a first output p.
np transistor, 31 ₂ and the second output pnp transistor 32 is a voltage divider consisting of the series resistance of three other, are identified by the same reference numerals to the same components as shown in FIG.

[0046] Then, the voltage adjustment circuit 1 includes a first input terminal I _1, a second input terminal I _2, and an output terminal O, the first operational amplifier 30 ₁ and the first output pnp transistor 31 ₁ A first voltage regulator portion including
Operational amplifier 30 ₂ and the second output pnp transistor 3
Containing 1 ₂ and comprising a second voltage regulator section. First
The emitter of the output pnp transistor 31 ₁ is connected to the _first input terminal I ₁ , the emitter of the second output pnp transistor 31 ₂ is connected to the _second input terminal I ₂ , and the first and second outputs pnp The collectors of the transistors 31 ₁ and 31 ₂ are connected to the output terminal O. The voltage divider 32 is connected between the output side of the DC-DC converter 8 for boosting and the ground, and has a 5V setting terminal and a 4.8V setting terminal.
5V of the first operational amplifier 30 ₁ of the inverting input divider 32
The setting terminals, the inverting input of the second operational amplifier 30 ₂ is connected to the 4.8V setting terminal of the voltage divider 32, both the operational amplifier 30 _1, 30 ₂ of the non-inverting input both the output terminal O
Connected to. The first operational amplifier 30 to the output of ₁ is the first output pnp transistor 31 ₁ of the base, the output of the second operational amplifier 30 ₂ is the second output pnp transistor 3
It is connected to one _second base.

The following operation is performed in the voltage adjustment circuit 1 having the above configuration.

First, in the first voltage regulator,
The first operational amplifier 30 ₁ is output terminal O of the voltage adjustment circuit 1
5V voltage setting terminal of the output regulated voltage divider 32, i.e., so to drive the first output pnp transistor 31 ₁ of the base to be equal to 5V, the first output pnp
Battery power supply 9 applied to the emitter of transistor 31 ₁
Is adjusted in the _first output pnp transistor 311 and taken out from its collector as an output adjustment voltage of 5V. Similarly, in the second voltage regulator portion of the second operational amplifier 30 ₂ is the voltage adjustment circuit 1
So that the output adjustment voltage of the output terminal O of the second voltage divider becomes equal to the voltage of the 4.8V setting terminal of the voltage divider 32, that is, 4.8V.
Since driving the output pnp transistor 31 ₂ of the base of the second output pnp transistor 31 ₂ of the applied step-up DC to the emitter - output the boosted voltage of the DC converter 8 and the second output pnp transistor 31 ₂ voltage at It is adjusted and taken out from its collector as an output adjustment voltage of 4.8V. As a result, 5 V and 4.8 are applied to the output terminal O.
Two output adjustment voltages of V are supplied, and the higher voltage 5 V is output from the output terminal O.

Now, the first input terminal I of the voltage adjustment circuit 1
_When the output voltage of the battery power supply 9 supplied to ₁ is relatively high, the output adjustment voltage output from the first voltage regulator section is maintained at 5 V, so that the first output pnp 5V obtained to the collector of the transistor 31 ₁
Output adjustment voltage from output terminal O to CCD line sensor 1
3 is supplied as an operating voltage.

Next, as the battery power supply 9 is consumed, the battery power supply 9 supplied to the _first input terminal I ₁ of the voltage adjustment circuit ₁ is increased.
, The output adjustment voltage output from the first voltage regulator cannot be maintained at 5 V, and for example, drops to 4.8 V or less. In this state, of the two voltages supplied to the output terminal O, the output adjustment voltage of 4.8 V extracted from the second voltage regulator is higher, so the second output pnp transistor 31 ₂ 4.8V output adjustment voltage obtained at the collector of
It is supplied to the D line sensor 13 as an operating voltage.

As described above, according to this embodiment, when the output voltage of the battery power supply 9 is relatively high, the output adjustment voltage of 5 V obtained by adjusting the output voltage is applied to the battery power supply 9. When the output voltage of the DC-DC converter 8 becomes low, the output adjustment voltage of 4.8 V obtained by adjusting the output boost voltage of the DC-DC
Since it is supplied as an operating voltage to the line sensor 13,
The use efficiency of the battery power supply 9 can be improved, and the life of the battery power supply 9 can be extended.

According to the present embodiment, as in the above-described embodiment, there is no need to consider the internal voltage drop and the fluctuation of the load, and the configuration can be simplified as compared with the above-described embodiment. It is.

In each of the embodiments described above, the case where the power supply circuit according to the present invention is applied to a bar code scanner is described. However, the power supply circuit according to the present invention is limited to the case where the power supply circuit is applied to a bar code scanner. In particular, the present invention can be similarly applied to a battery drive device that has a microcomputer built in the device and needs to operate at a constant voltage, such as a remote control device and a calculator device.

Further, the direct current for boosting shown in each of the above-described embodiments was used.
12V which is the value of the output boost voltage of the DC converter 8, 5V or 4.8V which is the value of the adjustment voltage of the first and second voltage regulators 2 and 3, and the first and second voltage regulator parts The adjustment voltage values of 5 V and 4.8 V, and the detection voltage value of the voltage detector 4 of 4.9 V are all merely examples when the CCD line sensor 13 as a load device is operated. The respective values in the present invention are not limited to those numerical values, and these values can be appropriately changed depending on the type of the CCD line sensor 13 as the load device.

[0055]

As described above, according to the present invention,
A first input terminal I ₁ for receiving the output voltage of the battery power supply 9, a second input terminal I ₂ for receiving the output boosted voltage of the DC-DC converter 8 for boosting, an operating voltage of the load device, for example, an operation of the CCD line sensor 13 A voltage adjusting circuit having an output terminal for selectively generating a first voltage equal to the voltage or a second voltage slightly lower than the first voltage, wherein the output voltage of the battery power supply is high; In the meantime, the first voltage obtained by adjusting the output voltage is supplied to a load device, for example, a CCD line sensor 1.
And when the output voltage of the battery power supply 9 decreases, the second voltage obtained by adjusting the output boost voltage of the boost DC-DC converter 8 is supplied to a load device, for example, a CCD line sensor 13. As a result, the use efficiency of the battery power supply 9 can be improved, and the life of the battery power supply 9 can be extended.

In the voltage adjusting circuit 1, the output voltage of the battery power supply 9 is monitored and detected substantially at the output terminal O. Therefore, the internal voltage drop and the fluctuation of the load are considered. There is also an effect that the output voltage can be monitored and detected without the need.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment in which a power supply circuit according to the present invention is applied to a barcode scanner.

FIG. 2 is a block diagram showing a configuration of a barcode scanner including the power supply circuit shown in FIG.

FIG. 3 is a circuit configuration diagram showing an example of a specific configuration of each component constituting the voltage adjustment circuit shown in FIG. 1;

FIG. 4 is a configuration diagram showing a second embodiment in which the power supply circuit according to the present invention is applied to a barcode scanner.

FIG. 5 is a block diagram showing an example of the overall configuration of a conventional barcode scanner.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Voltage adjustment circuit 2 1st voltage adjuster 3 2nd voltage adjuster 4 Voltage detector 5 Switch 6 1st Schottky diode for buffer 7 2nd Schottky diode for buffer 8 DC for boosting DC converter 9 Battery power supply 10 1-chip microcomputer (microcomputer) 11 LED (light emitting diode) drive circuit 12 LED array 13 CCD line sensor (load device) 14 Amplification circuit 15 Binarization circuit 16 Oscillation circuit for generating operation clock signal Reference Signs List 17 intermittent switch 18 infrared LED driving circuit 19 infrared LED generating remote control code 20 operation key matrix 21 bar code 22 third Schottky diode supplying driving power to microcomputer 10 23 supplying driving power to microcomputer 10 Fourth Schottky diode 24 ₂ , 24 ₃ , 24 ₄ operational amplifiers 25 ₂ , 25 ₃ , 25 ₄ constant current sources 26 ₂ , 26 ₃ , 26 ₄ Zener diodes 27 ₂ , 27 ₃ , 27 ₅ output npn transistors 28 ₂ , 28 ₃ , 28 ₄ , 28 ₅ , 29 ₂ , 29 ₃ , 2
9 ₄ , 29 ₅ Resistance 30 ₁ First operational amplifier 30 ₂ Second operational amplifier 31 ₁ First output pnp transistor 31 ₂ Second output pnp transistor 32 Voltage divider composed of three series resistors

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ identification code FI G06K 7/10 G06F 1/00 333D H02M 3/155 331A (58) Field surveyed (Int.Cl. ⁶ , DB name) H02J 7 / 00 302 G06F 1/26-1/32 G05F 1/56 310 H02M 3/155 G06K 7/10

Claims (3)

(57) [Claims] A DC-DC converter for boosting an output voltage of a battery power supply to generate a boosted voltage; a first input terminal receiving the output voltage of the battery power supply; and a second input terminal receiving the boosted voltage.
Input terminal and a first terminal equal to the operating voltage of the load device.
And a voltage adjusting circuit having an output terminal for selectively outputting either one of the first voltage and the second voltage slightly lower than the operating voltage, wherein the voltage adjusting circuit comprises:
A first voltage regulator connected between an input terminal and the output terminal; a second voltage regulator and a switch connected in series between the second input terminal and the output terminal; A voltage detector connected to an output terminal, wherein the first voltage regulator has a first voltage whose output voltage is equal to the operating voltage, and the second voltage regulator has an output voltage lower than the operating voltage. A slightly lower second voltage and the voltage detector are respectively selected and configured so that a detection voltage becomes a third voltage intermediate between the first and second voltages, and the switching is performed by a detection output of the voltage detector. A power supply circuit, wherein the power supply circuit is turned on and off to selectively activate or deactivate the second voltage regulator. 2. A DC-DC converter for boosting an output voltage of a battery power supply to generate a boosted voltage, a first input terminal receiving the output voltage of the battery power supply, and a second input terminal receiving the boosted voltage.
Input terminal and a first terminal equal to the operating voltage of the load device.
And a voltage adjusting circuit having an output terminal for selectively outputting either one of the first voltage and the second voltage slightly lower than the operating voltage, wherein the voltage adjusting circuit comprises:
A first P connected between the input terminal of
An NP transistor; a second PNP transistor connected between the second input terminal and the output terminal; and a connection between the second input terminal and a reference potential point, which is equal to the operating voltage. A voltage bleeder for generating a first voltage and a second voltage slightly lower than the operating voltage, comparing the first voltage with an output voltage of the output terminal, and outputting a comparison output to the first PNP transistor; And a second operational amplifier that compares the second voltage with the output voltage of the output terminal and supplies a comparison output to the second PNP transistor. Power supply circuit. 3. The power supply circuit according to claim 1, wherein the first voltage is 5V, and the second voltage is 4.8V.