JPH0651877A - Power supply circuit - Google Patents

Abstract

PURPOSE:To provide the power supply circuit for bar code scanner which is improved in utilizing efficiency of a battery power source, prolongs the service life of the battery power source and is not affected by an amt. of internal voltage drop or load state. CONSTITUTION:This circuit is provided with a DC/DC converter 8 to generate a boosting voltage from the output voltage of a battery power source 9, first input terminal 11 to receive the output voltage of the battery power source 9, second input terminal I2 to receive the boosting voltage and voltage adjusting circuit 1 equipped with an output terminal O to selectively output either a first voltage equal to the operating voltage of a load device such as a CCD line sensor for bar code reader, for example, or a second voltage a little lower than the operating voltage. Further, the voltage adjusting circuit 1 is composed of 1st and 2nd voltage adjusters 2 and 3 to generate the first and second voltages, voltage detector 4 to detect the voltage of the output terminal O, and switching part 5 to be closed by the detection output.

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 in particular, while the output voltage of a power supply battery is high, the output voltage is adjusted and used as an operating voltage of a load voltage to reduce the output voltage of the battery. In this case, the present invention relates to a power supply circuit suitable for use in a bar code scanner, in which a boost voltage is adjusted and used as an operating voltage of the load voltage.

[0002]

2. Description of the Related Art Generally, in a touch type bar code scanner using a CCD (charge coupled device) line sensor for reading a bar code, a relatively high voltage (for example, 12V) is applied to drive the CCD line sensor.
And a relatively low stabilization voltage (for example, 5V), and if there is a fluctuation in those voltages, especially if there is a fluctuation in the stabilization voltage of 5V, the bar code in the CCD line sensor The reading sensitivity changes or the reading operation becomes unstable.

Most of the bar code scanners have a handy type in which a battery power source for driving is built in. In such a bar code scanner driven by a battery power source, the battery power source is usually Output voltage is DC-
The voltage of 12V is obtained by increasing the voltage with a DC converter, while the voltage of 12V is reduced by a series voltage regulator and the voltage is stabilized to obtain 5V.

By the way, 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, 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, Reference numeral 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, 59 is a key matrix, 60 is a battery power supply, 61 is an on / off switch, 62 is a step-up DC-DC converter, 63 is a serial voltage regulator, and 64 is a bar code.

Projection light is supplied from the LED array 52 to the bar code 64, and 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 that operate 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, and 5V is obtained by stepping down the 12V by the series voltage regulator 63 and stabilizing the voltage.

The bar code scanner having the above-described structure generally operates as follows.

First, when the keys of the key matrix 59 are not operated, 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. It has stopped working.

Next, when any key in the key matrix 59 is operated, the microcomputer 50 starts to operate, and the oscillation circuit 56 starts the oscillation operation of the operation clock signal. Here, the key command by the operation of the key is the transmission of the remote control code, that is, the infrared LE.
When only the remote control code is transmitted from D58, since the switch closing signal is not sent from the microcomputer 50 to the intermittent switch 61, the intermittent switch 61 is maintained in the open state, and the DC-DC converter 62 and the serial voltage are connected. The adjuster 63 does not perform any operation, and of course, the CCD
The line sensor 53 also does not read the barcode 64. Then, 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.

Then, when any key in the key matrix 59 is operated again, the operation of the microcomputer 50 is started and the oscillation circuit 56 starts the oscillation operation of the operation clock signal. Here, when the key command by the operation of the key is scanning and reading of the bar code 64, a switch closing signal is supplied from the microcomputer 50 to the intermittent switch 61, which causes the intermittent switch 61 to close. 62 and series voltage regulator 6
3 sequentially starts operating, and the CCD line sensor 53 is supplied with operating voltages of 12V and 5V. At this time, a start pulse and a sensor clock signal subsequent thereto are supplied from the microcomputer 50 to the CCD line sensor 53, so that the CCD line sensor 53 starts scanning and reading the bar code 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 cut off, and the intermittent switch 61 is cut off. Opens, the DC-DC converter 62 and the series voltage regulator 63 become inoperative,
The power supply to the CCD line sensor 53 is cut off, and the original stop mode is restored.

[0011]

However, in the power supply circuit in the above-mentioned known bar code scanner, the output voltage of the battery power supply 60 is once converted into the DC-DC converter 62 by the DC-DC converter 62.
The voltage is boosted to V, and the serial voltage regulator 63
By lowering 2V to 5V, two voltages 12
Since it obtains V, 5V, the battery power source 60
It is necessary to use a large-capacity nickel-cadmium (nickel cadmium) battery, lead-acid battery, etc., and there is a problem that not only the power supply but also the entire bar code scanner becomes expensive and large. However, if a secondary battery such as a lead storage battery is used, there is a problem that a dedicated charger is required separately, and it is necessary to spend a lot of time for charging.

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

In order to avoid the above problems, the present inventor selects the output voltage of the battery power source and the boosted voltage from the DC-DC converter in addition to the series voltage regulator that supplies the operating voltage to the load device. Provided with a switch for switching and supplying to the input of the series voltage regulator, and a voltage detector for detecting the output voltage of the battery power supply, and the voltage detector indicates that the output voltage of the battery power supply has dropped below a predetermined value. The power supply circuit is designed to improve the utilization efficiency of the battery power supply and extend the life of the battery power supply by detecting the output voltage by the switch and switching the switch to the boost voltage side when the detection output is generated. is 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, it is necessary to consider the voltage drop generated by the series voltage regulator and other parts in the voltage detected by the voltage detector, and the voltage drop is the load fluctuation. Since it changes depending on the characteristics of the transistor used and the like, there is a problem that it is necessary to design the circuit with a margin for those changes.

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

[0016]

In order 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 an output voltage of the battery power supply. A first input terminal, a second receiving the boosted voltage
Input terminal and a first equal to the operating voltage of the load device
Voltage or a second voltage that is slightly lower than the operating voltage, the voltage adjusting circuit having an output terminal for selectively outputting the voltage.
A first voltage regulator connected between the 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 the 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 which is higher than the operating voltage. The slightly lower second voltage, the voltage detector is selectively configured so that the detection voltage is a third voltage intermediate between the first and second voltages, and the switching is performed according to the detection output of the voltage detector. And a first means for selectively energizing or deactivating the second voltage regulator by switching the device on and off.

To achieve the above object, the present invention provides a DC-DC converter for boosting an output voltage of a battery power source to generate a boosted voltage, and a first input terminal for receiving the output voltage of the battery power source. A second input terminal for receiving the boosted voltage, and an output terminal for selectively outputting either a first voltage equal to the operating voltage of the load device or a second voltage slightly lower than the operating voltage. And a voltage adjusting circuit having a first PNP transistor connected between the first input terminal and the output terminal, the second input terminal and the output terminal. A second PNP transistor connected between the second input terminal and the reference potential point, and a second voltage that is equal to the operating voltage and slightly lower than the operating voltage. Generates the voltage of Voltage breeder and, the first voltage and the first P output voltage is compared with the said output terminal
From a first operational amplifier that supplies a comparison output to an NP 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. The second means is provided.

[0018]

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

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

Next, assuming that the battery power source is used for a relatively long period of time and the output voltage thereof drops, and the output voltage of the first voltage adjusting circuit drops to 4.9 V or less accordingly, the voltage detector Detects the voltage drop and generates a detection output at the output, and this detection output is supplied to the switch to close it and 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 (4.8V) is supplied to the load device (CCD line sensor) as an 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 source, so that the utilization efficiency of the battery power source is improved. Therefore, the life of the battery power source can be extended.

Further, at the time of 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 amount, the load state, and the like.

[0023]

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

FIG. 1 is a circuit configuration diagram showing a first embodiment in which a power supply circuit according to the present invention is applied to a bar code scanner, and FIG. 2 is a configuration of a bar code scanner including the power supply circuit. It is a block configuration diagram showing.

In FIGS. 1 and 2, 1 is a voltage regulator circuit, 2 is a first voltage regulator, 3 is a second voltage regulator, 4
Is a voltage detector, 5 is a switch, and 6 and 7 are first buffers.
And a second Schottky diode, 8 is a DC for boosting-
DC converter, 9 is a battery power source, 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 as a load device, 14 is an amplification circuit, 15 Is a binarization circuit, 16 is an oscillation circuit that generates 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.

Then, the voltage adjusting circuit 1 includes the first and second
Input terminal I₁, I₂And an output terminal O
A first voltage equal to the operating voltage of the in-sensor, eg 5
A first voltage regulator 2 for generating V, and the first voltage
A second voltage slightly lower than (5V), eg 4.8.
A second voltage regulator 3 for generating V and the first voltage
An intermediate voltage between (5V) and the second voltage (4.8V),
For example, a voltage detector 4 that detects a voltage of 4.9 V or less
And a DC-DC converter for boosting selectively to the second voltage regulator 3.
The switching device 5 for supplying the boosted output voltage of the switching device 8 and the first power supply.
The interference on the output side of the pressure regulator 2 and the second voltage regulator 3 is eliminated.
First and second Schottky dio for buffer to remove
It consists of cards 6 and 7. The input of the first voltage regulator 2 is the first
Input terminal I of 1 ₁The input of the second voltage regulator 3 is switched
Second input terminal I₂Respectively connected to
The output of the first voltage regulator 2 is the first Schottky diode.
Output of the second voltage regulator 3 to the output terminal O via the battery 6.
Output also via the second Schottky diode 7 output terminal
Connected to O. The input of the voltage detector 4 is connected to the output terminal O.
And its output is connected to the control end of the switch 5. First
Input terminal I of 1₁Is the second input on the output side of the battery power source 9.
Terminal I₂On the output side of the step-up DC-DC converter 8 respectively.
Connected to the output terminal O of the CCD line sensor 13
It is connected to a stable voltage (5V) supply terminal.

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

In addition to this, the one-chip microcomputer 10 is an LE
An LED emission drive pulse is sent to the LED array 12 via the D drive circuit 11, a sensor clock signal and a start pulse are sent to the CDD line sensor 13, an oscillation start signal is sent to the oscillation circuit 16, and a switch closing signal is sent to the line sensor on / off switch 14. Infrared LED 19 via infrared LED drive circuit 18
Are configured to supply remote control codes to
On the other hand, the bar code read signal obtained by the CDD line sensor 13 is received via the amplification 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 received. It is configured to receive.

In the above construction, the overall operation of the bar code scanner shown in FIG. 2 is almost the same as that of the above-mentioned known bar code scanner.
The overall operation will be briefly described below.

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

In this state, the operation key matrix 2
When any key of 0 is operated, the microcomputer 10
Starts to operate and supplies an oscillation start signal to the oscillation circuit 16, so that the oscillation circuit 16 comes to generate an operation clock signal. In this case, if the type of the key command by the operation of the key is the transmission of the remote control code, that is, if it is the command to transmit the remote control code from the infrared LED 18, the microcomputer 10 causes the infrared LED drive circuit 18 to operate. A remote control code is supplied to the infrared LED 19 via. At this time, the microcomputer 10 does not send a switch closing signal to the intermittent switch 17, and the intermittent switch 17 is maintained in the open state. Therefore, in the step-up DC-DC converter 8 and the voltage adjusting circuit 1, Is not performed and CC
Since the operating voltage is not 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.

Then, again, the operation key matrix 20
When any one of the keys is operated, the microcomputer 10 starts operating and supplies an oscillation start signal to the oscillation circuit 16, and the oscillation circuit 16 generates an operation clock signal as before. . In this case, if the type of the key command by the operation of the key is the scanning reading of the bar code 21 this time, the microcomputer 10 supplies a switch closing signal to the intermittent switch 17, thereby closing the intermittent switch 17. Therefore, both the step-up DC-DC converter 8 and the voltage adjustment circuit 1 start normal operation, and 12V and 5V
Is supplied to the CCD line sensor 13. At the same time, the microcomputer 10 controls the CCD line sensor 13
Since the start pulse and the sensor clock signal subsequent thereto are supplied to the CCD line sensor 13, the CCD line sensor 13 enters the scanning reading state of the barcode 21, and the barcode 2
Start scan reading of 1. Then, when the scanning reading of the barcode 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 addressed to the intermittent switch 17 is stopped, the intermittent switch 17 is opened, the step-up DC-DC converter 8 and the voltage adjusting circuit 1 are both inoperative, and the CCD The supply of operating power to the line sensor 13 is cut off, and the CCD line sensor 13 is also deactivated. Further, the oscillation circuit 16 also stops the oscillation operation of the operation clock signal and returns to the original stop mode state.

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

Now, when the output voltage of the battery power source 9 is relatively high, for example, 6.0 V or higher, at a relatively new time of the battery power source 9 (when the battery power source is just replaced), the output voltage of the battery power source 9 (for example, , 6.0 V or more) is supplied from the first input terminal I ₁ to the first voltage regulator 2,
The voltage regulator 2 adjusts the output voltage to a voltage equal to the operating voltage of the CCD line sensor 13, for example, 5 V, and the regulated stabilizing voltage is the first Schottky connected in the forward direction. It is led to the output terminal O via the diode 6 and is supplied from the output terminal O to the CCD line sensor 13. In this case, the output voltage of the output terminal O is 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 5V from the first voltage regulator 2 is applied to the CCD line sensor 1.
3 is supplied.

On the other hand, when the battery power source 9 is used for a long time,
When the output voltage of the battery power source 9 drops, for example, to 5.5 V or less, the regulated voltage obtained at the output of the first voltage regulator 2 cannot maintain 5 V and gradually falls. Like When the adjusted voltage drops considerably, for example, to about 4.8V, the voltage detector 4 detects the adjusted voltage,
The detection output is supplied to the switch 5, and the switch 5 is immediately closed, so that the output boosted voltage (for example, 12 V) of the boost DC-DC converter 8 is supplied to the second voltage regulator 3. Then, a voltage slightly lower than 5V, for example, a regulated voltage of 4.8V is output from the output. And
The regulated stabilization 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 from the output terminal O to the CCD line sensor 13.

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

In this case, the operating voltage is supplied to the microcomputer 10 through the third and fourth Schottky diodes 22 and 23 connected back to back, but the output voltage of the battery power source 9 is 5V or more. When the output voltage of the battery power supply 9 is supplied to the microcomputer 10 via the third Schottky diode 22 when the output voltage of the battery power supply 9 becomes lower than 5V, the voltage adjustment circuit 1
Is supplied to the microcomputer 10 via the fourth Schottky diode 23.

As described above, according to the present embodiment, while the output voltage of the battery power source 9 is high, the output voltage is adjusted in the first voltage regulator 2 to a voltage equal to the operating voltage of the CCD line sensor 13. Then, the adjusted voltage is supplied to the CCD line sensor 13 as a line sensor operating voltage, and when the output voltage of the battery power source 9 decreases, the output boosted voltage of the boosting DC-DC converter 8 is changed to a second voltage regulator. In step 3, the voltage is adjusted to a voltage slightly lower than the operating voltage, and the adjusted voltage is used as the line sensor operating voltage in the CCD.
Since the power is supplied to the line sensor 13, the utilization efficiency of the battery power source 9 can be improved, and the life of the battery power source 9 can be extended.

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

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

In FIG. 3, 24 ₂ , 24 ₃ , 24 ₄ are operational amplifiers, 25 ₂ , 25 ₃ , 25 ₄ are 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.

The first voltage regulator 2 includes a reference voltage generating circuit composed of an operational amplifier 24 ₂ and a series circuit of a constant current source 25 ₂ and a zener diode 26 ₂ connected to the non-inverting input 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 The voltage regulator 2 is configured to be powered by the output voltage of the battery power source 9 and to output the regulated voltage from the emitter of the transistor 27 ₂ . The second voltage regulator 3 has the same configuration as the first voltage regulator 2. The voltage detector 4 is 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 the base of the switching transistor 27 _5, and the voltage detector 4
Is 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 ,
The reference numeral 24 ₃ is an output reference voltage of a reference voltage generating circuit composed of constant current sources 25 ₂ and 25 ₃ and zener diodes 26 ₂ and 26 ₃ and the emitter output voltages of the transistors 27 ₂ and 27 ₃ are resistors 28 ₂ and 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 so as to output the voltage. In the voltage detector 4, the operational amplifier 24
₄ is a voltage comparison between the output reference voltage of the reference voltage generating circuit including the constant current source 25 ₄ and the zener diode 26 ₄ and the voltage obtained by dividing the input voltage by the resistors 28 ₄ and 29 ₄ and performing the voltage division. 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.

Next, 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, 30 ₁ is a first operational amplifier, 30 ₂ is a second operational amplifier, 31 ₁ is a first output p.
An np transistor, 31 ₂ is a second output pnp transistor, 32 is a voltage divider composed of three series resistors, and the same components as those shown in FIG. 1 are denoted by the same reference numerals.

The voltage adjusting circuit 1 includes a first input terminal I ₁ , a second input terminal I ₂ , and an output terminal O, and has a first operational amplifier 30 ₁ and a first output pnp transistor 31 _1. A first voltage regulator portion including a second
Operational amplifier 30 ₂ and second output pnp transistor 3
A _second voltage regulator section including 1 ₂ and. 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 output pnp of The collectors of the transistors 31 ₁ and 31 ₂ are connected to the output terminal O. The voltage divider 32 is connected and arranged between the output side of the step-up DC-DC converter 8 and the ground, and has a 5V setting terminal and a 4.8V setting terminal.
The inverting input of the first operational amplifier 30 ₁ is 5V of the voltage divider 32.
To the setting terminal, the inverting input of the second operational amplifier 30 ₂ is connected to the 4.8 V setting terminal of the voltage divider 32, and the non-inverting inputs of both operational amplifiers 30 ₁ and 30 ₂ are both output terminals O.
Connected to. The output of the first operational amplifier 30 ₁ is at the base of the _first output pnp transistor 31 ₁ , and the output of the second operational amplifier 30 ₂ is at the second output pnp transistor 3 1.
Connected to the bases of 1 ₂ respectively.

In voltage adjusting circuit 1 having the above structure, the following operation is performed.

First, in the first voltage regulator section,
The first operational amplifier 30 ₁ has an output terminal O of the voltage adjusting circuit 1.
Drive the base of the first output pnp transistor 31 ₁ so that the output adjustment voltage of the first output pnp transistor 31 ₁ becomes equal to the voltage of the 5V setting terminal of the voltage divider 32, that is, 5V.
Battery power source is applied to the emitter of the transistor 31 ₁ 9
Output voltage is adjusted in the _first output pnp transistor 31 _{1 and} taken out as an output adjusted voltage of 5 V from its collector. Similarly, in the second voltage regulator portion, the second operational amplifier 30 ₂ is connected to the voltage regulator 1
The second voltage is adjusted so that the output adjustment voltage of the output terminal O is 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 regulated and taken from its collector as an output regulated voltage of 4.8V. As a result, 5V and 4.8 are applied to the output terminal O.
Although two output adjustment voltages of V are supplied, the higher voltage 5V among them is output from the output terminal O.

Now, the first input terminal I of the voltage adjusting circuit 1
_When the output voltage of the battery power source 9 supplied to ₁ is relatively high, the output adjustment voltage output from the first voltage regulator portion maintains 5V, so as described above, the first output pnp 5V obtained to the collector of the transistor 31 ₁
Output adjustment voltage from the output terminal O to the CCD line sensor 1
3 as an operating voltage.

Next, as the battery power source 9 is consumed, the battery power source 9 supplied to the _first input terminal I ₁ of the voltage adjusting circuit 1
When the output voltage of 1 is considerably reduced, the output regulation voltage output from the first voltage regulator portion cannot maintain 5V, and for example, falls to 4.8V or less. In this state, of the two voltages supplied to the output terminal O, the 4.8V output adjustment voltage taken out from the second voltage regulator portion is higher, so the second output pnp transistor 31 ₂ The output adjustment voltage of 4.8V obtained at the collector of the
It is supplied to the D line sensor 13 as an operating voltage.

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

Further, according to the present embodiment, it is not necessary to consider the internal voltage drop amount and the fluctuation of the load as in the above-mentioned embodiments, and the structure can be simplified as compared with the above-mentioned embodiments. Is.

In each of the above-mentioned embodiments, the case where the power supply circuit according to the present invention is applied to a bar code scanner is explained, but the power supply circuit according to the present invention is applied only to a bar code scanner. In particular, the present invention can be similarly applied to a battery drive device, such as a remote controller device or a calculator device, which has a microcomputer built in the device and needs to operate at a constant voltage.

Further, the DC for boosting shown in each of the above embodiments
12V which is the value of the output boosted voltage of the DC converter 8, 5V and 4.8V which are the values of the regulated voltage of the first and second voltage regulators 2 and 3 of the first and second voltage regulator portions. The adjustment voltage values of 5V and 4.8V, and the detection voltage value of the voltage detector 4 of 4.9V are merely examples for operating the CCD line sensor 13 which is a load device. As a matter of course, the respective values in the present invention are not limited to those numerical values, and the values are appropriately changed depending on the type of the CCD line sensor 13 which is 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 source 9, a second input terminal I ₂ for receiving the boosted output voltage of the step-up DC-DC converter 8, an operating voltage of the load device, for example, an operation of the CCD line sensor 13. A voltage adjusting circuit 1 having an output terminal O for selectively generating a first voltage equal to the voltage or a second voltage slightly lower than the first voltage is provided, and the output voltage of the battery power supply 9 is high. During the interval, the first voltage obtained by adjusting the output voltage is applied to the load device, for example, the CCD line sensor 1
3 and when the output voltage of the battery power source 9 drops, the second voltage obtained by adjusting the output boost voltage of the boost DC-DC converter 8 is supplied to the load device, for example, the CCD line sensor 13. Therefore, there is an effect that the utilization efficiency of the battery power source 9 can be improved and the life of the battery power source 9 can be extended.

Further, in the voltage adjusting circuit 1, since the output voltage of the battery power source 9 is monitored and detected substantially at the output terminal O, the internal voltage drop and load fluctuation are taken into consideration. There is also an effect that the output voltage can be monitored and detected without any need.

[Brief description of drawings]

FIG. 1 is a circuit configuration 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 block configuration diagram showing a configuration of a bar code 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 constituent element that constitutes the voltage adjustment circuit shown in FIG.

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

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

[Explanation of Codes] 1 voltage regulator 2 first voltage regulator 3 second voltage regulator 4 voltage detector 5 switcher 6 first Schottky diode for buffer 7 second Schottky diode for buffer 8 DC-DC converter for boosting 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 Operating clock signal Oscillation circuit for generating 17 Intermittent switch 18 Infrared LED drive circuit 19 Infrared LED for generating remote control code 20 Operation key matrix 21 Bar code 22 Third Schottky diode 23 for supplying drive power to the microcomputer 10 To the microcomputer 10 Fourth Schottky diode that supplies drive power Do 24 ₂ , 24 ₃ , 24 ₄ operational amplifier 25 ₂ , 25 ₃ , 25 ₄ constant current source 26 ₂ , 26 ₃ , 26 ₄ Zener diode 27 ₂ , 27 ₃ , 27 ₅ output npn transistor 28 ₂ , 28 ₃ , 28 ₄ , 28 _5, 29 _2, 29 _3, 2
9 ₄ and 29 ₅ resistor 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

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G06K 7/10 Y 8945-5L

Claims (3)

[Claims] 1. A DC-DC converter that boosts an output voltage of a battery power source to generate a boosted voltage, a first input terminal that receives the output voltage of the battery power source, and a second input terminal that receives the boosted voltage.
Input terminal and a first equal to the operating voltage of the load device
Voltage or a second voltage that is slightly lower than the operating voltage, the voltage adjusting circuit having an output terminal for selectively outputting the voltage.
A first voltage regulator connected between the 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 the 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 which is higher than the operating voltage. The slightly lower second voltage, the voltage detector is selectively configured so that the detection voltage is a third voltage intermediate between the first and second voltages, and the switching is performed according to the detection output of the voltage detector. A power supply circuit, characterized in that the power supply circuit is intermittently operated to selectively activate or deactivate the second voltage regulator. 2. A DC-DC converter for boosting an output voltage of a battery power source to generate a boosted voltage, a first input terminal for receiving the output voltage of the battery power source, and a second input terminal for receiving the boosted voltage.
Input terminal and a first equal to the operating voltage of the load device
Voltage or a second voltage that is slightly lower than the operating voltage, the voltage adjusting circuit having an output terminal for selectively outputting the voltage.
A first P connected between the input terminal of the
An NP transistor, a second PNP transistor connected between the second input terminal and the output terminal, and a second PNP transistor connected between the second input terminal and a reference potential point and equal to the operating voltage. A voltage bleeder that generates a first voltage and a second voltage slightly lower than the operating voltage is compared with the first voltage and the output voltage of the output terminal, and a comparison output is 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 to do. 3. The power supply circuit according to claim 1, wherein the first voltage is 5V and the second voltage is 4.8V.