JP2001147244A - Voltage check circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply obtain reference voltage data which corresponds to a reference voltage used as a reference when whether a voltage is high or low is judged. SOLUTION: Instead of a battery 18, an arbitrary reference voltage Vref1 is given to a battery-voltage detection circuit 26 from an internal adjusting device 26. Detection voltage data DBTT which is obtained at this time is written into an EEPROM 40 as reference voltage data Dref1'. An arbitrary reference voltage Vref2 is given to a charging-voltage detection circuit 35. Detection voltage data DCHG which is obtained at this time is written into the EEPROM 40 as reference voltage data Dref2. Pieces of reference voltage data DBC1 to DBC3 which correspond to reference voltages VBC1 to VBC3 which are required for checking a battery are calculated in such a way that a microcomputer 20 calculates a proportion by using the reference voltages VBC1 to VBC3, the reference value of the reference voltage Vref1 and the reference voltage data Ddef1. Reference voltage data which corresponds to a prescribed charging voltage which is required for controlling a charging operation is calculated in such a way that the microcomputer 20 calculates a proportion by using a reference voltage VTH, the voltage value of the value of the reference voltage Vref2 and the detection voltage data DCHG.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage check circuit for checking the output voltage of a battery and the charge voltage of a capacitor.

[0002]

2. Description of the Related Art There are many devices driven by a battery, such as a cellular phone and a digital camera.
Some recent photographic cameras have a computerized photographing mechanism and control mechanism, and are driven by a built-in battery as a power supply. As a device incorporating such a battery as a power supply, a device in which a battery check is performed to notify a user of a remaining battery level is known. In this battery check, the remaining amount of the battery is determined by checking the level of the output voltage of the battery with respect to a predetermined reference voltage. Are set in advance.

In some strobe devices, the charge voltage of a main capacitor for strobe light emission is checked, and the charge is controlled. For example, when detecting that the main capacitor has been charged to the specified charging voltage,
Some devices stop charging automatically. In such a strobe device, similarly to the battery check, the level of the charging voltage of the main capacitor with respect to a specified charging voltage (reference voltage) is checked.

In the voltage check circuit for checking the level of the output voltage of the battery or the charging voltage of the main capacitor as described above, the target voltage to be checked, for example, the output voltage of the battery is divided as a detection voltage proportional to the voltage. The target voltage with respect to the reference voltage is obtained from the magnitude relationship between voltage data obtained by analog-to-digital conversion of the detected voltage by an A / D converter and reference voltage data prepared in advance corresponding to the reference voltage. There is something to check the height of.

[0005]

When the level of the target voltage with respect to the reference voltage is checked by a digital quantity as described above, the A / D converter is used when a voltage equal to the reference voltage is applied to the voltage dividing circuit. To output the voltage data having the same value as the reference voltage data, and adjust the resistance value of the voltage dividing circuit, or conversely, when a voltage equal to the reference voltage is applied to the voltage dividing circuit, the A / D converter The reference voltage data must be adjusted and set so as to be equal to the obtained voltage data. However, the method of adjusting the resistance value of the voltage divider circuit requires manual adjustment while measuring the voltage output from the voltage divider circuit. It is difficult to adjust.

On the other hand, a method of adjusting the reference voltage data is as follows.
By providing a reference voltage using an external power supply device instead of a battery or the like and using the voltage data obtained at this time as reference voltage data, an accurate reference taking into account errors in the voltage divider circuit and the A / D converter Voltage data can be obtained. However, when a plurality of reference voltages are required as described above, an expensive power supply device capable of controlling the output voltage by a computer or the like is required, or two or more power supply devices having different output voltages are required. However, there is a problem that the equipment for adjustment becomes expensive. In addition, there is a problem that time is required to adjust the output voltage of the power supply to a predetermined reference voltage or to switch the power supply, and it takes time to set reference voltage data.

Further, when the reference voltage data for the specified charging voltage of the main capacitor of the strobe device is set by using such a method, the specified charging voltage is set to a high voltage.
For example, since the voltage is set to 300 V or more, a power supply capable of outputting a high voltage is required as a power supply for setting the reference voltage data, which causes a problem that the power supply is expensive and difficult to handle.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and is intended to obtain a plurality of reference voltage data and reference voltage data corresponding to a high voltage easily and accurately using an inexpensive power supply device. It is an object of the present invention to provide a voltage check circuit.

[0009]

In order to achieve the above object, according to the first aspect of the present invention, when an arbitrary predetermined reference voltage is input to the voltage detecting means at the time of adjustment, an analog-to-digital converter is provided. From the first storage means for storing the detected voltage data obtained from the reference voltage data, the second storage means for storing each voltage value of the reference voltage and the reference voltage, and the first and second storage means. Calculating means for calculating voltage data corresponding to the reference voltage using the read reference voltage data and the respective voltage values of the reference voltage and the reference voltage, wherein the voltage data obtained from the calculating means is It is used as reference voltage data when checking the voltage level.

According to the second aspect of the present invention, a plurality of different voltage values are stored in the second storage means as the voltage value of the reference voltage, so that the reference voltage data corresponding to each reference voltage having a different voltage value is stored. It can be calculated by the calculating means.

According to the third aspect of the invention, the target voltage is the output voltage of the battery, and the remaining amount of the battery is determined based on the level of the reference voltage. According to a fifth aspect of the present invention, the target voltage is a charging voltage of the main capacitor for strobe light emission, and the charging of the main capacitor is controlled by the level of the reference voltage.

[0012]

FIG. 2 shows an instant camera embodying the present invention. On the front surface of the camera body 2, a collapsible lens barrel 3, a light emitting window 4 for autofocus, and a light receiving window 5 are provided.
Are provided. The lens barrel 3 holds a photographing lens 6, and a light metering window 7 for measuring the brightness of the subject and a strobe light receiving window 8 are provided on the front surface of the lens barrel 3.
A release button 10 is provided on the grip unit 9, and a flash light emitting unit 11 of a flash device and a finder 12 are provided above the release button 10.
On the upper surface of the camera body 2, a main switch button 1
3, a setting button 14, an LCD 15, and a discharge port 16 are provided.

The inside of the grip portion 9 is a battery chamber, into which a battery 18 (see FIG. 1) is loaded as a power source for the instant camera. The battery 18 is, for example, one in which four AA batteries having a nominal voltage of 1.5 V are connected in series. Further, various terminals for connecting an internal circuit of the instant camera and an external adjustment device are provided in the battery compartment.

Each time the main switch button 13 is pressed, the power of the instant camera is switched on and off alternately. When the power is turned on, the lens barrel 3 is extended to a photographing position protruding forward from the retracted position shown in the drawing, and becomes ready for photographing. When the power is turned off, the lens barrel 3 is returned to the retracted position, and no photographing is performed even if the release button 10 is pressed.

In the back of the light projecting window 4 and the light receiving window 5, a light transmitter and a light receiver for distance measurement are incorporated, and in the rear of the light measuring window 7, a light receiving element for photometry is arranged. Further, a light receiving element for automatic light control is arranged behind the strobe light receiving window 8.

When the release button 10 is half-pressed, distance measuring light is projected from the distance measuring light projector toward the object, and the reflected light is received by the light receiver to measure the object distance. The luminance of the subject is measured by the light receiving element through. Subsequently, when the release button 10 is fully pressed, the focusing of the photographing lens 6 is performed in accordance with the measured subject distance, and the opening and closing control of the shutter blades is performed based on the measured subject brightness, and instantaneous control is performed. Exposure to the film 17 is performed.

When the subject brightness is below a predetermined level,
In synchronization with opening and closing of the shutter blades, strobe light is emitted from the strobe light emitting unit 11 toward the subject. Then, the strobe light reflected by the subject at the time of the strobe light emission is received by the light receiving element for automatic light adjustment, and when the amount of received light reaches a predetermined level, the strobe light emission is stopped.

The exposed instant film 17 is discharged from a discharge port 16. At the time of discharging, the developer pod 17a of the instant film 17
6 ruptured by a pair of developing rollers provided in the back,
The developing solution contained in the developer pod 17a is developed inside. As a result, the instant film 17
Is completed, and after a lapse of a predetermined time, a printed photograph is obtained.

By operating the setting button 14, exposure correction and the like can be selected. The LCD 15 displays information necessary for photographing, such as exposure correction, the number of remaining instant films, and the remaining battery power. The remaining amount of the battery is indicated by a battery mark 19, for example, as shown in FIG. The battery mark 19 indicates the remaining amount of the battery 18 by changing the number of lighted three indicators 19a to 19c inside the shape of a dry battery. As the remaining amount of the battery 18 decreases, the number of illuminated indicators decreases. If the remaining amount is not enough to perform photographing, the battery mark 1 is turned off with all the indicators 19a to 19c turned off.
After 9 is blinked for a certain time, the power is turned off.

FIG. 1 shows a main configuration of the instant camera.
Shown in The microcomputer 20 includes an interface for inputting and outputting signals and data to and from the CPU and each unit.
The D / A (analog / digital) converters 20a and 20b are integrated into one chip, and controls the operation of the entire instant camera according to a sequence program stored in the ROM 21. The RAM 22 is used as a work memory in which data necessary for performing the sequence is temporarily written. The ROM 21 stores reference voltages V _ref1 and V _ref2 , and first to third reference voltages V _{BC1 to} V _BC1 to be described later.
_BC3 , each voltage value of the specified charging voltage V _TH (V _ref1 , V _ref2 ,
V _{BC1 to} V _BC3 , V _TH ) are written in advance.

When the power is turned on, the power supply circuit 24 converts the output voltage of the battery 18 into a constant drive voltage and outputs it. Each part of the microcomputer 20, the instant camera (not shown) such as a shutter mechanism and an auto-focus mechanism operates by receiving the driving voltage. When the power is turned off, the power supply circuit 24 is not operated to output a voltage substantially equal to the output voltage of the battery 18 in order to reduce power consumption.
Supplied to Thereby, the microcomputer 30
Operate in the sleep state by this voltage. In the sleep state, only a minimum necessary circuit such as a calendar circuit and a power ON / OFF detection circuit in the microcomputer 20 is operated.

A voltage check circuit for judging the remaining amount of the battery 18, that is, for checking the battery, includes a battery voltage detection circuit 26 and a microcomputer 20.
The output voltage of No. 8 is a target voltage. Battery voltage detection circuit 26
Is composed of an FET 27 and voltage dividing resistors 28a and 28b. The FET 27 has a voltage dividing resistor 28a, 2 having a source connected to the positive electrode of the battery 18 and a drain connected in series.
8b is grounded. When a check signal (negative voltage) is input to the gate of the FET 27 from the microcomputer 20, the FET 27 is turned ON with conduction between the drain and the source.

When the FET 27 is turned on, a current flows from the battery 18 to the voltage dividing resistors 28a and 28b connected in series. At this time, the voltage generated at the connection point between the voltage dividing resistors 28a and 28b is output as the detection voltage V _BTT . The detection voltage V _BTT is determined by each resistance value of the voltage dividing resistors 28 a and 28 b and the on-resistance between the drain and the source of the FET 27 and is proportional to the output voltage V _OUT of the battery 18. A current in a range where the on-resistance is constant flows between the drain and the source of the FET 27.

The detection voltage V _BTT output from the battery voltage detection circuit 26 is sent to the A / D converter 20a of the microcomputer 20. A / D converter 20a is a detection voltage V _{BT T} digital conversion, and outputs the detected voltage data D _BTT. At the time of this conversion, digital conversion is performed so as to have a linearity between the detection voltage V _BTT and the detection voltage data _DBTT .

The microcomputer 20 _compares the detected voltage data _DBTT with the first to third data obtained by calculation as described later.
The magnitude of the output voltage V _OUT of the battery 18 with respect to the predetermined first to third reference voltages V _{BC1 to} V _BC3 is checked based on the magnitude relationship with the reference voltage data D _{BC1 to} D _BC3 ,
8 is determined. Specifically, the output voltage V _OUT is equal to or higher than the first reference voltage V _BC1 , _lower than the first reference voltage V _BC1 and higher than the second reference voltage V _BC2 , _lower than the second reference voltage V _BC2 and higher than the third reference voltage V _BC3 , It is determined whether the voltage is _lower than the third reference voltage V _BC3 , and the remaining amount of the battery 18 is determined in four stages.

The determination result of the remaining amount of the battery 18 is sent to the LCD driver 29, and the battery mark 19 is lit on the LCD 15 in a display form corresponding to the remaining amount of the battery 18. Battery 18
If the remaining amount of insufficient to perform photographing, that is, when the detection voltage V _BTT less than the third reference voltage V _{BC 3} is, after the battery mark 19 as previously described is flashing by a certain time , The power of the instant camera is turned off.

The strobe device includes a booster circuit 30, a main capacitor 31, a trigger circuit 32, a strobe discharge tube 33,
It is composed of a dimming circuit 34, a charging voltage detecting circuit 35, and the like, and is controlled by the microcomputer 20.

The booster circuit 30 includes the microcomputer 2
It operates while the charging signal from 0 is being input, and converts the output voltage of the battery 18 into a high-voltage AC and outputs it. The AC output from the booster circuit 30 is supplied to the rectifier diode 3
Oa is rectified and supplied to the main capacitor 31 to charge the main capacitor 31.

The charging voltage detection circuit 35 is connected to the main capacitor 31. This charging voltage detection circuit 35
Is a voltage check circuit for charge control together with the microcomputer 20, and sets the charge voltage of the main capacitor 31 as a target voltage. Charge voltage detection circuit 3
5 is two voltage dividing resistors 35a and 35b connected in series.
And a capacitor 35c.
A detection voltage V _CHG proportional to the charging voltage of 1 is output. The detected voltage V _CHG is sent to the microcomputer 20, A / D converter 20b by the detection voltage data D _CHG
Is converted to At the time of this conversion, digital conversion is performed so that the detection voltage V _CHG and the detection voltage data D _CHG have linearity.

The microcomputer 20 determines the main capacitor with respect to a predetermined specified charging voltage (reference voltage) V _TH from the magnitude relation between the detected voltage data D _CHG and the reference voltage data D _TH obtained by calculation as described later. The level of the charging voltage V _{MC at} 31 is checked. When the charging voltage V _MC of the main capacitor 31 is higher than the specified charging voltage V _TH , the charging by the booster circuit 30 is stopped. When the charging voltage V _MC is lower than the specified charging voltage V _TH , the booster circuit 30 is activated. To maintain the charging voltage V _MC of the main capacitor 31 at the specified charging voltage V _TH .

The strobe discharge tube 33 includes a strobe light emitting unit 1
1. This strobe discharge tube 33 is connected in parallel with the main condenser 31, and between the main condenser 31 and the strobe discharge tube 33,
IGB whose ON / OFF is controlled by the dimming circuit 34
T37 is connected. The IGBT 37 is turned on (conduction state) prior to strobe light emission.

A synchronizing signal synchronized with the opening and closing of the shutter blades is input from the microcomputer 20 to the trigger circuit 32. When the sync signal is input, the trigger circuit 32 applies a trigger voltage to the strobe discharge tube 33. As a result, the electric charge of the main capacitor 31 is transferred to the strobe discharge tube 33 through the IGBT 37 which is turned on.
And the strobe light emission is started. The strobe light emitted from the strobe discharge tube 33 is emitted from the strobe light emitting unit 11 toward the subject.

The dimming circuit 34 turns on the IGBT 37 prior to flash emission as described above. In addition, from the moment when the strobe discharge tube 33 emits light, the strobe light reflected by the subject is received by the light receiving element for automatic light control, and the light amount is integrated. At the moment when the integrated amount reaches a predetermined level, the IGB
The flash emission is stopped by turning off T37. Thereby, the irradiation amount of the strobe light is automatically adjusted so that the exposure amount by the strobe light becomes appropriate.

The first voltage input terminals 51a and 51b and the second
The voltage input terminals 52a and 52b and the I / O terminal 53
These are provided in the battery compartment, and an external adjustment device is connected to these in a state where the battery 18 is removed at the time of adjustment by the manufacturer.

The first voltage input terminals 51a and 51b are provided on a pair of power supply lines connected to the battery 18, and are connected to the battery voltage detection circuit 26. This first voltage input terminal 5
Reference voltages V _ref1 for battery check, which also _serve as operating voltages of the instant camera, are provided from the adjusting device to 1a and 51b.
Is entered.

The second voltage input terminals 52 a and 52 b are provided on the circuits at both ends of the main capacitor 31 and are connected to the charging voltage detection circuit 35. The reference voltage _Vref2 for charge control is input to the second voltage input terminals 52a and 52b from the adjusting device.

At the time of adjustment by the manufacturer, the microcomputer 20 communicates with the adjustment device via the I / O terminal 53, executes a predetermined sequence in accordance with various instructions from the adjustment device, and executes the reference voltage V A / D when _ref1 is input
The detected voltage data D _BTT obtained from converter 20a as the reference voltage data D _ref1 for battery check and charging control detection voltage data D _{CH G} obtained from the A / D converter 20b at the input of the reference voltage V _ref2 Is written in the EEPROM 40 as the reference voltage data D _ref2 .
Each of the reference voltages V _ref1 and V _ref2 is supplied from a power supply device of a constant voltage type adjusted with high accuracy by an adjusting device.

By utilizing the fact that the detected voltage before A / D conversion and the detected voltage data after A / D conversion have linearity, EE
Using the reference voltage data D _ref1 for battery check stored in the PROM 40 and the voltage values of the reference voltage V _ref1 and the first to third reference voltages V _{BC1 to} V _BC3 stored in the ROM 21, The microcomputer 20 performs the proportional calculation according to the formulas (1) to (3) to obtain the first to third reference voltage data D required for performing the battery check.
_{BC1 to DBC3} are calculated respectively. D _BC1 = D _ref1 × (V _BC1 / V _ref1 ) ··· D _BC2 = D _ref1 × (V _BC2 / V _ref1 ) ··· _{DB 3} = D _ref1 × (V _BC3 / V _ref1 ) ···

Thus, three types of first to third reference voltages corresponding to the first to third reference voltages V _BC1 to V _BC3 necessary for performing a battery check using a single power source of one type of output. Data D _{BC1 to} D _BC3 can be obtained, and the power supply device on the adjustment device side is simplified, and the working time is shortened.

In this example, the reference voltage V_ref1To “5.0
V ", the first to third reference voltages V_BC1~ V _BC3To “4.7
V "," 4.5 V ", and" 4.0 V ". In addition,
In this example, the reference voltage V_ref1Is an instant camera
Since it also serves as the operating voltage for adjustment, the voltage range
You can operate the instant camera as much as you can.
However, if you want to give the operating voltage separately,
Is the reference voltage V_ref1Is not limited.

Similarly, reference voltage data D for charge control
_The microcomputer 20 performs a proportional calculation of the following equation using the reference voltage V _ref2 and the respective voltage values of the reference voltage V _ref2 and the charge reference voltage V _TH , whereby the specified charge voltage V required for controlling the charge voltage is obtained. Calculate reference voltage data _DTH corresponding to _TH . D _TH = D _ref2 × (V _TH / V _ref2 )

Thus, even if a voltage lower than the prescribed charging voltage V _TH is applied as the reference voltage V _ref2 , necessary reference voltage data D _TH can be obtained. It can be. In this example, the prescribed charging voltage V _TH is “315 V”, but the reference voltage V _ref2 is “60 V”.

As described above, the reference voltage data is obtained by calculation utilizing the fact that the A / D conversion is performed linearly. However, the battery voltage detection circuit 26 for the A / D converters 20a and 20b, When the impedance of the voltage detection circuit 35 is large, good linearity may not be obtained. Therefore, it is preferable to reduce the impedance of each of the voltage detection circuits 26 and 35.

Specifically, in the battery voltage detection circuit 26,
It is desirable that the combined resistance value of the voltage dividing resistors 28a and 28b be 10 KΩ or less. In the charging voltage detection circuit 35,
In order to _divide the high charging voltage V _MC of the main capacitor 31 into a relatively low detection voltage V _CHG , the voltage _dividing resistors 35a, 3
The composite impedance of 5b increases. Therefore, A
The capacitor 35c is connected in parallel with the input terminal of the / D converter 20b.
To reduce the impedance of the charging voltage detection circuit 35 with respect to the A / D converter 20b. In the battery voltage detection circuit 26, a voltage dividing resistor 28
a and 28b also function as resistors for applying a load to the battery 18, but the voltage dividing resistors 28a and 28b are used to adjust the load.
A resistor different from b may be connected to the battery 18.

In this example, the microcomputer 20 operates as a voltage check circuit that uses the output voltage of the battery 18 as a target voltage and a voltage check circuit that uses the charge voltage of the main capacitor as a target voltage.

Next, the operation of the above configuration will be described. At the time of manufacturing the instant camera, a reference voltage V _ref1 for battery check, a reference voltage V _ref2 for charge control,
The ROM 21 in which the voltage values of the third reference voltages V _{BC1 to} V _BC3 and the specified charging voltage V _TH are written is assembled. The instant camera on which various components such as the microcomputer 20 are assembled is sent to an adjustment process.

In the adjustment step, as shown in FIG.
Terminals on the adjustment device side are connected to the first voltage input terminals 51a and 51b, the second voltage input terminals 52a and 52b, and the I / O terminal 53 in the battery chamber. After the connection is completed, the adjustment device first outputs the reference voltage _Vref1, and inputs the reference voltage _Vref1 to the first voltage input terminals 51a and 51b. Next, the adjusting device sends an instruction to operate the power supply circuit 24 to the microcomputer 20 so that each part of the instant camera operates with the voltage output from the power supply circuit 24 using the reference voltage _Vref1 from the adjusting device as the power supply voltage. Make it possible.

[0048] After this, the adjusting device instructs the uptake of the reference voltage data D _{re f1} relative to the microcomputer 20. When receiving this instruction, the microcomputer 20 first sends a check signal to the FET 27 in the battery voltage detection circuit 26 to turn on the FET 27. Next, the microcomputer 20 performs sampling / digital conversion of the detection voltage V _BTT output from the battery voltage detection circuit 26 by the A / D converter 20a, and writes the result into the EEPROM 40 as reference voltage data D _ref1 .

Reference voltage data D_ref1After writing is completed
In addition, the adjusting device operates with the reference voltage V_ref1Output is continued
And the reference voltage V for charge control_ref2Start output of three
Lighting voltage V _ref2Are input to the second voltage input terminals 52a and 52b.
This reference voltage V_ref2Of the main controller
When the capacitor 31 is charged, its charging voltage V_MCIs the reference voltage
V _ref2Becomes

After the start of the output of the reference voltage _Vref2 , the adjusting device instructs the microcomputer 20 to take in the reference voltage data _Dref2 . Microcomputer 2
In the case of 0, the detection voltage V _CHG output from the charging voltage detection circuit 35 is subjected to sampling / digital conversion by the A / D converter 20b, and the result is written to the EEPROM 40 as reference voltage data D _ref2 .

Thus, each reference voltage V_reF1, V
_ref2And a voltage detection circuit that actually uses them, A
The voltage data obtained through the / D converter is converted to each reference voltage data.
Data D _ref1, D_ref2Write to EEPROM 40 as
The adjustment process is completed only by this.

Therefore, the adjustment device includes a battery chain.
Reference voltage V _ref1Output only
Only need to have a device that outputs multiple different voltages.
It is necessary to prepare three power supplies and power supplies with different output voltages
There is no. In addition, a low reference voltage V is used for charge control._ref2
It is sufficient if there is a power supply device that outputs the specified charging voltage V_THTo
There is no need for a power supply that outputs a correspondingly high voltage.

Further, the reference voltage data D _ref1 and the detection voltage data D _BTT during normal use and the reference voltage data D _ref2 and the detection voltage data D _CHG during normal use are obtained through the same voltage detection circuit and A / D converter, respectively. Therefore, the voltage detection circuits 26 and 35, the A / D converters 20a and 20b can be set only by setting the reference voltage given from the outside with high accuracy.
Even if the individual differences match, there is no need to adjust to eliminate them.

After the writing to the EEPROM 40 is completed as described above, the instant camera is completed with the remaining parts assembled, subjected to a function test, and shipped.
Sold. Then, the instant camera is used for shooting by the user. At the time of photographing, a battery 18 is loaded in the battery chamber.

In normal use, the microcomputer 20 checks the battery every time the power is turned on, each time a release operation is performed while the power is turned on, and each time a periodic interrupt process occurs. Is performed.

In the battery check process, first, as shown in FIG.
_ref1 is read by the microcomputer 20. Further, the reference voltage _Vref1 and the first to third
Each voltage value of the reference voltages V _{BC1 to} V _BC3 is read out by the microcomputer 20. Next, the microcomputer 20 reads the read reference voltage data D _ref1.
When the _BC3 voltage values V _ref1, V _{BC 1} ~V performs proportional calculation by applying the above-equation, the first to third reference voltage data D
Calculate _{BC1 to BC3} .

According to the equation, when the output voltage V _OUT of the battery 18 is equal to the first reference voltage V _BC1 (= 4.7 V), the battery voltage detection circuit 26 and the A / D converter 20
The first reference voltage data D _BC1 equal to the data obtained through “a” is obtained.

Similarly, from the equation, the output voltage V _out is the second
When the reference voltage V _BC2 (= 4.5 V), the output voltage V _out is equal to the third reference voltage V _BC3 (=
4.0 V), the battery voltage detection circuit 2
6, the second reference voltage data D _BC2 and the third reference voltage data D _BC equal to the data obtained through the A / D converter 20a
₃ are obtained respectively.

First to third reference voltage data D _{BC1 to} D _BC3
After the calculation of is completed, the microcomputer 20 sends a check signal to turn on the FET 27, and then the A / D
Activate converter 20a. Then, the detection voltage V _BTT output from the battery voltage detection circuit 26 is sampled and digitally converted to obtain detection voltage data _DBTT corresponding to the output voltage V _OUT of the battery 18. Thereafter, the microcomputer 20, the detection voltage data D _BTT, first to third reference voltage data D _{BC 1} to D was calculated as described above
The remaining amount of the battery 18 is determined from the magnitude relationship with _BC3 .

First, the detected voltage data D _BTT is compared with the first reference voltage data D _BC1 . In this comparison, for example, when the detected voltage data _DBT is determined to be equal to or higher than the first reference voltage data _DBC1, it is determined that the output voltage _Vout of the battery 18 is equal to or higher than the first reference voltage _VBC1. Based on the result, all the three indicators 19a to 19c of the battery mark 19 of the LCD 15 are turned on, and the user is notified of the battery 18
Is displayed.

When the detected voltage data D _BTT is smaller than the first reference voltage data D _BC1 , the detected voltage data D _BTT
Is compared with the second reference voltage data _DBC2 . By this comparison, the detected voltage data _DBTT is changed to the second reference voltage data _BC2.
If it is determined that the output voltage V _out
Is _lower than the first reference voltage V _BC1 and equal to or higher than the second reference voltage V _BC2 . Then, based on the determination result, the two indicators 19 of the battery mark 19 of the LCD 15 are displayed.
b and 19c are lit, indicating to the user that the remaining capacity of the battery 18 is slightly reduced.

Further, when the detected voltage data _DBTT is less than the second reference voltage data _BC2 ,
_BTT is compared with the third reference voltage data _DBC3 . By this comparison, the detected voltage data _DBTT is changed to the third reference voltage data D
If it is determined that _BC3 or more, the output voltage V of the battery 18
_out is less than the second reference voltage V _BC2 and the third reference voltage V _BC3
As a result, one indicator 19c of the battery mark 19 is turned on, and the user is notified that the remaining amount of the battery 18 is low.

When the detected voltage data _DBTT is _lower than the third reference voltage data _BC3 , it is determined that the output voltage _Vout of the battery 18 is _lower than the third reference voltage _VBC3. The power is forcibly turned off by the microcomputer 20 after the battery mark 19 in which all the lights 19a to 19c are turned off blinks for a certain period of time.

On the other hand, in the charge control process, similarly to the battery check, each time the power is turned on, each time a release operation is performed while the power is turned on, and each time a periodic interrupt process occurs. Done.

As shown in FIG. 6, first, the reference voltage data D _ref2 is read from the EEPROM 40, and each voltage value of the reference voltage V _ref2 and the specified charging voltage V _TH is read from the ROM.
21. Thereafter, the microcomputer 20 applies the read reference voltage data D _ref2 and the respective voltage values V _ref2 and V _TH to the above equation, and calculates reference voltage data D _TH by proportional calculation. That is,
The charging voltage V _MC of the main capacitor 31 is equal to the specified charging voltage V
When it is at _TH , the charging voltage detection circuit 35, A / D
Reference voltage data D _TH equal to the data obtained through converter 20b is obtained.

After calculating the specified charging voltage data D _TH , the microcomputer 20 operates the A / D converter 20b to sample / digital convert the detection voltage V _CHG ,
The detection voltage data D _CHG corresponding to the charging voltage V _MC of the main capacitor 31 is obtained. Then, the detected voltage data D
_CHG is calculated using the reference voltage data D _TH calculated as described above.
, A magnitude relationship between the charging voltage V _MC and the specified charging voltage V _TH is determined, and the charging signal is controlled.

For example, detection voltage data D_CHGIs the reference voltage
Data D_THThe charging voltage V_MC
Is the specified charging voltage V_THHas been reached, and
The electric signal remains stopped. On the other hand, the detection voltage data
TA D_CHGIs the reference voltage data D _THIf less than
Charge voltage V_MCIs the specified charging voltage V_THIs lower than
Then, a charging signal is output to the booster circuit 30. This charging signal
, The booster circuit 30 starts operating, and the main capacitor 3
1 is charged. Then, after starting this charging,
Detection voltage V_CHGSampling and digital conversion
The detection voltage data D_CHGIs the reference voltage data D
_THStop sending the charge signal at the same or higher
Stop and stop charging. This allows the main capacitor
31 charging voltage V_MCIs the specified charging voltage V_THIs kept.

In the above embodiment, each reference voltage data is calculated by executing a calculation for each process of the battery check and the charge control. For example, in response to the power being turned on, each reference voltage data is calculated. Calculate and store the result in RAM
And the stored reference voltage data may be used until the power is turned off.
Alternatively, each reference voltage data may be calculated only once after the input of the reference voltage, and the calculated reference voltage data may be written to the EEPROM and used.

In the above embodiment, whether to start or stop charging is controlled depending on the charging voltage of the main capacitor with respect to the specified charging voltage. For example, a reference voltage for stopping charging and a reference voltage for stopping charging are controlled. Alternatively, a start reference voltage for starting charging lower than the stop reference voltage may be set. Also in this case, similarly to the reference voltage data corresponding to each of the battery check reference voltages, a stop reference voltage and a start reference voltage are calculated from reference voltage data obtained by applying one fixed reference voltage. Reference voltage data corresponding to each of the voltages can be obtained.

In the above description, an example in which the voltage check circuit of the present invention is used for checking the battery of an instant camera and controlling the charging of the main capacitor has been described. The present invention can be used in addition to the battery check and the charge control of the main capacitor, and the present invention can be used in other devices of the instant camera.

[0071]

As described above, according to the present invention,
An arbitrary predetermined reference voltage is input to the voltage detection means, and data obtained from the analog-to-digital converter is stored as reference voltage data. Using each of the voltage values, voltage data corresponding to the reference voltage is calculated, and this voltage data is used as reference voltage data when checking the level of the target voltage. Thus, reference voltage data for a plurality of reference voltages can be created, and the reference voltage can be set easily and accurately. Further, even if the reference voltage is high, the reference voltage data can be created using a low-voltage power supply device.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a main part of an instant camera.

FIG. 2 is a perspective view illustrating an appearance of an instant camera embodying the present invention.

FIG. 3 is an explanatory diagram illustrating an example of a battery mark.

FIG. 4 is a flowchart showing an adjustment procedure.

FIG. 5 is a flowchart illustrating a procedure of a battery check.

FIG. 6 is a flowchart of dying a charge control procedure.

[Explanation of symbols]

 Reference Signs List 18 battery 20 microcomputer 20a, 20b A / D converter 21 ROM 26, 35 voltage detection circuit 31 main capacitor 40 EEPROM

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2G016 CA04 CB12 CC01 CC04 CC06 CC16 CC27 CC28 CD06 CD14 CE03 2G035 AA21 AB03 AC01 AC16 AD03 AD11 AD26 AD28 AD41 2H053 AA03 AA04 BA08 DA03

Claims (4)

[Claims] 1. An apparatus comprising: voltage detecting means for outputting a detection voltage proportional to an input voltage; and an analog / digital converter for outputting detection voltage data obtained by digitally converting the detection voltage. The detected voltage data obtained from the analog-to-digital converter by inputting to the voltage detecting means, and the magnitude of the target voltage with respect to the reference voltage is determined based on the magnitude relationship between the reference voltage data corresponding to a predetermined reference voltage. In a voltage check circuit to be checked, a first storage for storing detected voltage data obtained from an analog-to-digital converter when an arbitrary predetermined reference voltage is input to the voltage detecting means during adjustment, as reference voltage data Means, second storage means for storing respective voltage values of the reference voltage and the reference voltage, 2
Calculating means for calculating voltage data corresponding to the reference voltage by using the reference voltage data read from the storage means and the respective voltage values of the reference voltage and the reference voltage, obtained from the calculating means. A voltage check circuit, wherein voltage data is used as reference voltage data when checking the level of a target voltage. 2. A plurality of different voltage values are stored in the second storage means as voltage values of the reference voltage, whereby reference voltage data corresponding to each reference voltage having a different voltage value is calculated by the calculation means. 2. The voltage check device according to claim 1, wherein the voltage check device can calculate the voltage. 3. The voltage check device according to claim 1, wherein the target voltage is an output voltage of the battery, and the remaining amount of the battery is determined based on a level relative to a reference voltage. 4. The voltage checking device according to claim 1, wherein the target voltage is a charging voltage of a main capacitor for strobe light emission, and the charging of the main capacitor is controlled according to a level relative to a reference voltage.