JPH0654457A - Power supply circuit - Google Patents

Abstract

PURPOSE:To provide a power supply circuit which is suitable for being used for a bard code scanner, capable of extending the life of a battery even when a relatively small capacity of battery is used by improving the utilization efficiency of a battery source 6. CONSTITUTION:This circuit comprises a DC-DC converter 5, which generates step-up voltage by boosting the output voltage of a battery source 6, a voltage regulator 3, which has an output terminal for supplying operation voltage to a load device, for example, a CCD line sensor for a bar code reader, a switch 4, which changes the output of the battery power source 6 and the stepped-up voltage selectively over to the input terminal of the voltage regulator 3 and supplies them to it, and a voltage detector 2, which detects the output voltage of the battery power 6, and when a voltage detector 2 detects the voltage below a specified value, it changes the switch 4 over to the stepped-up voltage side.

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 battery power source is high, the output voltage is adjusted and used as an operating voltage of a load device to lower 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 the boosted voltage is adjusted and used as the operating voltage of the load device.

[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 barcode 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. 4 is a block diagram showing an example of the entire configuration of a known bar code scanner.

In FIG. 4, 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.

The present invention is intended to eliminate the above-mentioned problems, and an object thereof is to improve the utilization efficiency of a battery power source and extend the battery life even when a dry battery having a relatively small capacity is used. It is to provide a power supply circuit capable of

[0014]

In order 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 an operating voltage for a load device. A series voltage regulator, a switcher that selectively supplies the output voltage of the battery power source and the boosted voltage to the input of the series voltage regulator, and a voltage detector that detects the output voltage of the battery power source. When the voltage detector detects a voltage equal to or lower than a predetermined value, the switching device is switched to the boosted voltage side.

In order 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 an intermittent connection for intermittently inputting the DC-DC converter. A switch, a microcomputer, an oscillating circuit for generating an operating clock signal, a switcher for switching the operating clock signal frequency, an output voltage of the battery power source or the boosted voltage is selectively supplied to the microcomputer as operating power. It consists of power supply means,
During normal processing in the microcomputer, the intermittent switch is turned off, the output voltage of the battery power supply is supplied to the microcomputer in the power supply means,
And, a low-frequency operation clock signal is generated in the switch, while the high-speed processing of the microcomputer, the intermittent switch is connected, the boosted voltage is supplied to the microcomputer in the power supply means, and , Second means for generating a high frequency operating clock signal in the switch.

[0016]

According to the first means, the output voltage of the battery power supply is monitored and detected by the voltage detector, and while the battery power supply is relatively new and the output voltage is high, for example, about 6.5V. Since the detection output is not obtained from the voltage detector and the switching device is switched to the output side of the battery power source, the output voltage of the battery power source is supplied to the input of the series voltage regulator via the switching device. In the series voltage regulator, after the output voltage is regulated to, for example, 5 V, the output voltage is applied to the load device as an operating voltage, for example,
The line sensor operating voltage is supplied to the CCD line sensor.

On the other hand, when the battery power source is used for a relatively long period of time and its output voltage is low, for example, 6.0 V or less, a detection output is sent from the voltage detector, and the switch is converted from DC to DC. Since it is switched to the output side of the converter, the output boost voltage of the DC-DC converter, for example, 12V
Is supplied to the input of the series voltage regulator via the switch, and as before, in the series voltage regulator, the output voltage is regulated to, for example, 5V and then operated from its output terminal. The voltage is supplied to the load device, for example, a CCD line sensor as a line sensor operating voltage.

Therefore, the utilization efficiency of the battery power source can be improved and the life of the battery power source can be extended.

According to the second means, when the processing in the one-chip microcomputer (microcomputer) is carried out at the normal speed, for example, in the normal operation such as the key command input processing or the memory backup processing, the microcomputer is lowered. Since it can be operated with the power supply voltage,
Turn off the DC-DC converter input and deactivate the DC-DC converter. Then, the power supply means supplies the output voltage of the battery power supply, which is a relatively low voltage, to the microcomputer as a power supply for operation, the switcher switches the operation clock signal frequency to the low frequency side, and the microcomputer switches the low frequency The above-mentioned processing is executed by the operation clock signal.

On the other hand, when the processing in the microcomputer is performed at high speed, for example, in the case of high-speed operation such as arithmetic processing and bar code decoding processing, it is necessary to operate the microcomputer with a high power supply voltage. The input of the converter is connected and the DC-DC converter is operated to generate the output boosted voltage. And the power supply means is
The relatively large boosted voltage is supplied to the microcomputer as a power supply for operation, the switcher switches the operation clock signal frequency to the high frequency side, and the microcomputer executes the processing with the operation clock signal at the high frequency.

Therefore, also in this means, the utilization efficiency of the battery power source can be improved and the life of the battery power source can be extended.

[0022]

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 voltage detector, 3 is a series voltage regulator, 4 is a switcher, 5 is a step-up DC-DC converter, 6 is a battery power source, and 7 is a battery power source. Is a one-chip microcomputer, 8 is LE
D (light emitting diode) drive circuit, 9 LED array, 1
0 is a CCD line sensor which is a load device, 11 is an amplifier circuit, 12 is a binarization circuit, 13 is an oscillation circuit for generating an operation clock signal, 14 is an intermittent switch, and 15 is an infrared LED.
Driving circuit, 16 is an infrared LE that generates a remote control code
D, 17 is a key matrix for operation, 18 is a bar code,
Reference numerals 19 and 20 are first and second Schottky diodes for supplying drive power to the microcomputer 7.

The voltage adjusting circuit 1 includes a voltage detector 2 for detecting a predetermined voltage, for example, a voltage of 6.0 V or less,
A series voltage regulator 3 for adjusting the output voltage to a line sensor operating voltage, for example, 5 V and outputting the same, and an input of the series voltage regulator 3 to the output side of the battery power source 6 or the output side of the DC-DC converter 5. And a switch 4 for selectively switching. The voltage detector 2 has its input connected to the output side of the battery power source 6 and its output connected to the switching control end of the switch 4.
The switch 4 has one input on the output side of the battery power source 6,
The other input is connected to the output side of the DC-DC converter 5, and the output is connected to the input of the series voltage regulator 3. The output of the serial voltage regulator 3 is connected to the low stable voltage (5V) supply terminal of the CCD line sensor 10.

Further, the DC-DC converter 5 includes a battery power source 6
Output voltage (this voltage fluctuates in the range of 6.6 to 3.8 V, for example, according to the length of the period of use of the battery power supply 6), and the boosted voltage (this voltage is also input). (For example, fluctuates in the range of 12 to 9 V according to the output voltage of the battery power source 6), the input of which is connected to the output side of the battery power source 6, and the output is the high voltage of the CCD line sensor 10. It is connected to the (12V) supply terminal.

In addition to this, the one-chip microcomputer 7 is an LED
An LED emission drive pulse is sent to the LED array 9 via the drive circuit 8, a sensor clock signal and a start pulse are sent to the CDD line sensor 10, and an oscillation start signal is sent to the oscillation circuit 13.
A switch closing signal is sent to the line sensor intermittent switch 14.
The infrared LED drive circuit 15 is configured to supply remote control codes to the infrared LEDs 16, respectively, while
The bar code read signal obtained by the CDD line sensor 10 is received via the amplifier circuit 11 and the binarization circuit 12,
Further, the operation clock signal from the oscillation circuit 13 and the key command from the key matrix 17 are respectively received.

In the above configuration, the overall operation of the bar code scanner shown in FIG. 2 is almost the same as the overall operation 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 17 is operated, this bar code scanner is in the stop mode. In this stop mode, the microcomputer 7 is in a state in which all operations are stopped. Therefore, the oscillation circuit 13 also stops the oscillation operation of the operation clock signal.

In this state, the operation key matrix 1
When any key of 7 is operated, the microcomputer 7 starts operating and supplies an oscillation start signal to the oscillation circuit 13, so that the oscillation circuit 13 generates 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 only transmit the remote control code from the infrared LED 15, the microcomputer 7 causes the infrared LED drive circuit 15 to operate. A remote control code is supplied to the infrared LED 16 via the. At this time, the microcomputer 7 does not send a switch closing signal to the intermittent switch 14 and the intermittent switch 14 is maintained in the open state, so that the DC-DC converter 5 and the voltage adjusting circuit 1 operate normally. Is not performed and the operating voltage is not supplied to the CCD line sensor 10, so the CCD line sensor 10 does not scan and read the bar code 18. When the transmission of the remote control code is completed or completed, the microcomputer 7 stops all operations, the oscillation circuit 13 also stops its operation clock oscillation operation, and returns to the original stop mode.

Then, again, the operation key matrix 17
When any one of the keys is operated, the microcomputer 7 starts to operate and supplies an oscillation start signal to the oscillation circuit 13, and the oscillation circuit 13 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 barcode 18 this time, the microcomputer 7 supplies a switch closing signal to the intermittent switch 14, thereby closing the intermittent switch 14. In order to do so, the DC-DC converter 5 and the voltage adjustment circuit 1
Both start normal operation, and operating voltages of 12 V and 5 V are supplied to the CCD line sensor 10. At the same time, the microcomputer 7 supplies the CCD line sensor 10 with the start pulse and the subsequent sensor clock signal, respectively.
The scanning reading state of 8 is entered, and the scanning reading of the barcode 18 is started. Then, when scanning and reading of the barcode 18 on the CCD line sensor 10 is completed, the microcomputer 7 stops all operations. As a result, the supply of the switch closing signal to the intermittent switch 14 is stopped, the intermittent switch 14 is opened, the DC-DC converter 5 and the voltage adjusting circuit 1 are both inoperative, and the CCD line sensor The supply of the operating power of 10 is cut off, and the CCD line sensor 10 is also deactivated. Further, the oscillation circuit 13 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 the bar code scanner will be described.

Now, when the output voltage of the battery power source 6 is relatively high, for example, about 6.5 V, when the battery power source 6 is relatively new (just after replacement), the voltage detection circuit 2 causes the battery power source 6 to operate. The switch 3 is switched to the output side of the battery power source 6 without detecting the output voltage of the battery. Then, the series voltage regulator 3 directly inputs the output voltage (for example, 6.5 V) of the battery power source 6, adjusts the voltage to a stabilized voltage of 5 V, and outputs the adjusted voltage. Therefore, 12V obtained by the DC-DC converter 5 and 5V obtained by the series voltage regulator 3 are supplied to the CCD line sensor 10 as operating voltages.

On the other hand, when the battery power source 6 is used for a long time,
When the output voltage of the battery power source 6 drops to, for example, 5.9 V, the voltage detection circuit 2 causes the battery power source 6 to
Since the output voltage is detected and the detected output is supplied to the switch 3, the switch 3 is switched to the output side of the DC-DC converter 5. By this switching, the series voltage regulator 3 inputs the output voltage (for example, 12V) of the DC-DC converter 5, adjusts the voltage to a stabilized voltage of 5V, and outputs it. Therefore, the CCD line sensor 10 has the same operating voltage as the DC-DC converter 5 as before.
12V obtained in step 5 and 5V obtained in series voltage regulator 3
And are supplied.

In this case, the operating voltage of the microcomputer 7 is 2
It is supplied via two back-to-back first and second Schottky diodes 19 and 20, but when the output voltage of the battery power source 6 is higher than 5V, the output voltage of the battery power source 6 is the first Schottky diode 19. When the output voltage of the battery power source 6 becomes lower than 5V, the output voltage of the series voltage regulator 3 is supplied to the microcomputer 7 via the second Schottky diode 20.
Will be supplied to.

As described above, according to the present embodiment, while the battery power source 6 is relatively new and its output voltage is high, the output voltage of the battery power source 6 is directly adjusted by the voltage adjusting circuit 1, and the output voltage is adjusted. CCD with voltage as line sensor operating voltage
When the output voltage is low due to the use of the battery power source 6 for a relatively long period of time while being supplied to the line sensor 10, the voltage boosting voltage of the DC-DC converter 5 is adjusted by the voltage adjusting circuit 1, and the adjusted voltage is adjusted. Since the line sensor operating voltage is supplied to the CCD line sensor 10, the utilization efficiency of the battery power source 6 is improved, and thereby the life of the battery power source 6 can be extended.

Next, FIG. 3 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. 3, 21 is a frequency dividing circuit for generating high and low frequency-divided operating clock signals, 22 is two switching terminals 1 and 2, and a movable contact is normally connected to the switching terminal 1 side. The same components as those shown in FIG. 2 are denoted by the same reference numerals.

The difference between this embodiment and the above-mentioned first embodiment is that the first and second Schottky diodes 1
Regarding the connection of 9 and 20, the first embodiment described above is the second
While the anode side of the Schottky diode 20 is connected to the output side of the voltage adjusting circuit 1, in the present embodiment, the anode side of the second Schottky diode 20 is connected to the output side of the DC-DC converter 5. Regarding the points described above and the connection of the oscillation circuit 13, in the first embodiment described above, the output of the oscillation circuit 13 is connected to the microcomputer 7, whereas in the present embodiment, the output of the oscillation circuit 13 is A frequency divider circuit 21 for generating operation clock signals of two frequencies is connected to the side, and the operation clock signals of the two frequencies of the frequency divider circuit 21 are selectively sent to the microcomputer 7 between the frequency divider circuit 21 and the microcomputer 7. Regarding the point that the switch 22 to be supplied is connected and the configuration of the voltage adjusting circuit 1, the above-described first embodiment is composed of the voltage detecting circuit 2, the switch 3, and the series voltage adjusting unit 4. To However, the present embodiment is only for the point that the series voltage regulator 4 alone can be used (of course, the one of the first embodiment described above may be used). No structural difference can be found between the above and the first embodiment described above.

Regarding the difference between the operation according to the present embodiment and the operation according to the first embodiment described above, there is no significant difference between the two in the overall operation for the bar code scanner. Although detailed description of the specific operation is omitted, in the following, only the difference between the operation according to the present embodiment and the operation according to the first embodiment will be described.

First, a key command is input from the key matrix 17 to the microcomputer 7, and the type of the key command is, for example, key input processing, remote control code transmission processing, memory backup processing, etc. When it is sufficient to perform the processing operation at the normal speed, the microcomputer 7 sends the interrupt switch 14 and the switch 22.
No operation signal is sent to the destination. Therefore, the intermittent switch 14 is maintained in the open state, and DC-
Since the DC converter 5 does not perform a normal conversion operation, a boosted voltage is not generated at its output, and the microcomputer 7 uses the first Schottky diode 19 as an operating voltage.
The output voltage of the battery power supply 6 is supplied via the. Further, since the switch 22 is switched to the switching terminal 1 side, a low-frequency operation clock signal is taken into the microcomputer 7, and the microcomputer 7 performs the processing operation by this low operation clock signal.

On the other hand, from the key matrix 17 to the microcomputer 7
When there is a key command input to the microcomputer 7 and the type of the key command is one that requires the microcomputer 7 to operate at high speed, such as arithmetic processing and barcode decoding processing, the microcomputer 7 , Intermittent switch 1
4 is supplied with a switch closing signal, and at the same time, the switch 22
A switching signal is supplied to the destination. Therefore, the intermittent switch 14
Is switched to the closed state, the DC-DC converter 5 performs a normal conversion operation, and a boosted voltage is generated at the output thereof. Therefore, the microcomputer 7 receives the second Schottky diode 20 as an operating voltage. The boosted voltage is supplied via the. Further, since the switch 22 is switched to the switch terminal 2 side by supplying the switch signal, the operation clock signal of high frequency is taken into the microcomputer 7 this time,
The microcomputer 7 carries out the processing operation by this high operation clock signal.

As described above, the microcomputer 7 supplies the operating voltage for the operation speed depending on the type of the input key command only when the operation speed needs to be increased. Is higher than the normal voltage, and the frequency of the supplied operation clock signal is higher than the normal frequency, it is possible to effectively change the operation voltage of the microcomputer 7. , The use efficiency of the battery power source 6 is improved, and the battery power source 6
It is possible to extend the life of the.

In each of the above-described embodiments, the case where the power supply circuit according to the present invention is applied to a bar code scanner has been described, 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.

[0045]

As described above, according to the present invention,
While the output voltage of the battery power supply 6 is high, the output voltage is directly adjusted by the voltage adjusting circuit 1, and the adjusted voltage is supplied to the load device, for example, the CCD line sensor 10 as the line sensor operating voltage, and the battery power supply is used. When the output voltage of 6 is low, the output boosted voltage of the DC-DC converter 5 is adjusted by the voltage adjusting circuit 1, and the adjusted voltage is supplied to the load device, for example, the CCD line sensor 10 as a line sensor operating voltage. Therefore, there is an effect that the utilization efficiency of the battery power source 6 can be improved and the life of the battery power source 6 can be extended.

According to the present invention, the operating voltage of the microcomputer 7 is set higher than the normal voltage only when the microcomputer 7 performs a process requiring a high operating speed.
Moreover, since the operating clock signal frequency supplied to the microcomputer 7 is set higher than the normal frequency, the operating voltage of the microcomputer 7 can be effectively changed, and the utilization efficiency of the battery power source 6 can be improved. There is an effect that the life of the battery power source 6 can be extended.

The step-up DC voltage shown in each of the above embodiments
The output boosted voltage value of the DC converter 5 is 12V, the adjustment voltage value of the series voltage regulator 3 is 5V, etc.
It is a mere example when operating the load device, for example, the CCD line sensor 10, and it goes without saying that the respective values in the present invention are not limited to those numerical values, and those values are the load device. For example, it is appropriately changed depending on the type of the CCD line sensor 10.

[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 diagram showing a configuration of a bar code scanner including the power supply circuit shown in FIG.

FIG. 3 is a block configuration diagram showing a second embodiment in which a power supply circuit according to the present invention is applied to a bar code scanner.

FIG. 4 is a block configuration diagram showing an example of the overall configuration of a known barcode scanner. .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 voltage adjustment circuit 2 voltage detector 3 serial voltage regulator 4 switching device 5 step-up DC-DC converter 6 battery power supply 7 1-chip microcomputer (microcomputer) 8 LED (light emitting diode) drive circuit 9 LED array 10 CCD line sensor (Loading device) 11 Amplifier circuit 12 Binarization circuit 13 Oscillation circuit for generating operation clock signal 14 Intermittent switch 15 Infrared LED drive circuit 16 Infrared LED for generating remote control code 17 Key matrix for operation 18 Bar code 19 1st Schottky diode 20 Second Schottky diode 21 Divider circuit 22 Switching device

Claims (4)

[Claims] 1. A DC-DC converter that boosts an output voltage of a battery power source to generate a boosted voltage, a series voltage regulator that supplies an operating voltage to a load device, an output voltage of the battery power source, and the boosted voltage. A switch for selectively supplying to the input of the series voltage regulator, and a voltage detector for detecting the output voltage of the battery power supply, when the voltage detector detects a voltage equal to or lower than a predetermined value, A power supply circuit, wherein the switch is switched to the boosted voltage side. 2. The power supply circuit according to claim 1, wherein the boosted voltage is 12V and the operating voltage is 5V. 3. The power supply circuit according to claim 1, wherein the voltage equal to or lower than the predetermined value is a voltage equal to or lower than 6V. 4. A DC-DC converter for boosting an output voltage of a battery power source to generate a boosted voltage, an intermittent switch for connecting and disconnecting an input of the DC-DC converter, a microcomputer, and an operation clock signal. And a switching device for switching the operating clock signal frequency, and a power supply means for selectively supplying the output voltage of the battery power source or the boosted voltage to the microcomputer as operating power. At the time of processing, the intermittent switch is turned off, the output voltage of the battery power is supplied to the microcomputer in the power supply means, and a low-frequency operation clock signal is generated in the switch, while the microcomputer's At the time of high-speed processing, connect the on / off switch, and in the power supply means A power supply circuit which supplies the boosted voltage to the microcomputer and generates a high-frequency operation clock signal in the switch.