JPH08124690A - Electronic flash device - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to minimize the wasteful consumption of the power supply battery used in the electronic flash device. [Configuration] When charging the main capacitor 3 via a booster circuit 2 that boosts the power supply battery 1 at the time of shooting, the main capacitor 3
Of the charging voltage of the control circuit 106 is detected by the voltage detection circuit 4, and the time until the voltage becomes the photographing enable voltage is measured by the timing circuit of the control circuit 106.
According to the time information, the first charge cutoff timer is used when the time is within the first predetermined time, and the second charge cutoff timer is used when the time is within the second predetermined time that is longer than the first time (medium exhausted battery). , If the second predetermined time is exceeded (batteries that have been exhausted), select a third charge cutoff timer that is shorter than the second charge cutoff timer, and when the first and second charge cutoff timers are selected, At the end or full charge voltage, the third
In the case of the charge cutoff timer, the charge is stopped by the signal which is the end of the charge or the voltage which can be photographed, whichever comes first.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic flash device for a camera, and more particularly to a charge cutoff timer in the electronic flash device.

[0002]

2. Description of the Related Art Conventionally, in an electronic flash device, a battery voltage is boosted by a DC / DC converter, a main capacitor is charged with a high voltage, and energy for light emission is stored. In this case, it is general that the full charge voltage is set to be within the latitude range of the film and the photographing voltage is lower than the full charge voltage. Therefore, there is a time lag between reaching the chargeable voltage and reaching the full charge voltage. If the battery is relatively new, it will reach the full charge voltage in a time that does not affect shooting, but if the battery is exhausted, it will reach the full charge voltage in a considerably long time or will be fully charged if the battery is exhausted. It may not reach the voltage. In such a case, the charging current flows for a longer time than the battery, resulting in further exhaustion of the consumable battery, resulting in wasted time and wasted energy consumption.

Therefore, in many cases, there is provided a charge cutoff timer for stopping the charging within a predetermined time so as to avoid wasting energy. For example,
Measures the time from the start of charging or during charging, and stops charging if it does not reach a predetermined voltage, for example, the full charging voltage, or, for example, from the start of charging or during charging to the voltage at which the image can be captured and the full charging time A time-out timer that stops charging when the voltage that can be photographed is not reached within a predetermined time or when the voltage is not reached within a second predetermined time that is longer than the predetermined time It is generally used.

[0004]

By the way, there is a strong demand for miniaturization from the viewpoint of portability, and recently the battery voltage is low due to problems in the number of batteries used and the shape, and for example, it has been changed from 6V to 3V. Is the reality. Therefore, since the charging time is longer than before and the battery capacity is small, it is more necessary than ever to suppress battery waste. As for the energy consumption of the camera, the charging energy in the flash device has a large ratio, and how to suppress the energy loss in the flash device is a problem. Therefore, in the conventional cutoff timer, if the comparison is simply made due to the decrease in battery voltage, D
Input current to C / DC converter is 1/2, boost ratio is 2
It takes twice as long, and it takes about 4 times as long, so for a long time, for example, 1
A timer of 0 to 20 seconds is required, which is a problem that cannot be ignored in terms of operability and energy consumption.

The present invention has been made in view of the above-mentioned problems of the prior art.
It is an object of the present invention to provide an electronic flash device having good operability that matches battery characteristics.

[0006]

In order to achieve the above object, the present invention provides a charging circuit for a main capacitor, a voltage detection circuit for detecting the voltage of the main capacitor, and a timing circuit for operating during charging of the main capacitor. And a first charge cutoff timer that operates when the time from the start of charging the main capacitor measured by the timing circuit to the voltage at which the image can be captured is within a first predetermined time, A second charge cutoff timer that operates within a second predetermined time that is longer than the first predetermined time, and a third charge cutoff timer that operates when the second predetermined time is exceeded; The charging is stopped at the end of the first or second charge cutoff timer and the full charge voltage, or at the end of the third charge cutoff timer and the shootable voltage, whichever comes first. Further, the charging circuit preferably has a control terminal capable of selectively oscillating and stopping oscillation. Further, the voltage detection circuit includes a voltage dividing resistor for dividing the voltage of the main capacitor and a comparator. Also, the comparator is A /
It is preferable to use a D comparator. Further, the clock circuit is preferably controlled by a microcomputer.

[0007]

In the electronic flash circuit having the above-mentioned configuration, the time counting circuit measures the charging time until the voltage becomes the voltage at which the image can be taken, and the time of the charge cutoff timer is selected based on the time information, especially for a relatively new battery. Select the first charge cutoff timer, which has a short time, the long charge second charge cutoff timer, which has a long life for medium consumption, and the third charge cutoff timer, which has a long life. By selecting a timer and setting the time shorter than the second charge cutoff timer, the operability with a new battery is improved, and energy is not wasted on the exhausted battery. It is possible to make a flash device with good operability that matches the characteristics.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block circuit diagram of the electronic flash device of the present embodiment, FIG. 2 is a specific electric circuit diagram of the booster circuit,
FIG. 3 is a specific electric circuit diagram of the voltage detection circuit. In the figure, 1 is a battery as a power source, 2 is a booster circuit composed of a DC / DC converter for boosting a voltage using the battery 1 as a power source, 3 is a main capacitor of an electronic flash device, and output energy from the booster circuit 2 is shown. Is connected to store. Reference numeral 4 denotes a voltage detection circuit for detecting the voltage of the main capacitor 3, which is connected in parallel to the main capacitor 3. Reference numeral 5 denotes a light emitting circuit including a trigger circuit (not shown) for converting the charging energy of the main capacitor 3 into light energy, a flash discharge tube, etc., and is connected in parallel to the main capacitor 3. Reference numeral 6 is a power switch connected to the anode side of the battery 1. Further, as will be described later, the control terminals a and d transmit control signals generated by the control circuit 106 on the camera side to the booster circuit 2 and the light emitting circuit 5, respectively, and the control terminals b and c from the voltage detection circuit 4. It is connected so as to transmit the information signal to the control circuit 106 on the camera side.

Regarding the camera side operation circuit, 101
Is a photometric circuit, 102 is a power supply to each block,
For example, it is a constant voltage circuit block showing a constant voltage power source or the like. Reference numeral 103 is a display circuit using liquid crystal or the like, 104 is a switch circuit block for receiving a switch input, 1
Reference numeral 05 is a shutter drive circuit block, 106 is a control circuit block including a microcomputer, 107 is a film sensitivity detection circuit block for detecting film sensitivity,
Reference numeral 108 is a motor drive circuit block for moving the lens barrel to adjust the focus, and 109 is an automatic exposure circuit block. Then, in the control circuit block 106, the photometric circuit 10
1, constant voltage circuit block 102, display circuit 103, switch circuit block 104, shutter drive circuit block 1
05, a film sensitivity detection circuit block 107, a motor drive circuit block 108, and an automatic exposure circuit block 109 are connected to each other.

Next, the operation of a concrete circuit of the booster circuit 2 will be described with reference to FIG. First, the control terminal a is set to a high level to bring the transistor 23 into conduction, so that the base current of the oscillation transistor 22 changes from the battery 1 to the collector-emitter of the transistor 23 and the oscillation transformer 27.
Of the oscillating transformer 27, and the amplified collector current of the oscillating transistor 22 flows through the P winding of the oscillating transformer 27.
Electromotive force is generated in the S winding and the F winding, and the electromotive force generated in the S winding is transmitted from the rectifier diode 29 to the main capacitor 3, the battery 1, the base-emitter of the oscillation transistor 22, and the collector-emitter of the transistor 23. On the other hand, the electromotive force generated in the F winding flows through the resistor 28, the battery 1, the base-emitter of the oscillation transistor 22, and the collector-emitter of the transistor 23. By flowing as a base current, the oscillation transistor 22 is subjected to positive feedback and is instantly saturated.

When the generation of an electromotive current in the S winding and the F winding is weakened due to saturation of the magnetic flux in the core of the oscillating transformer 27, a counter electromotive force is generated, and the above-mentioned current loop is generated in the S winding and the F winding. On the other hand, since a current tries to flow in the opposite current loop, a reverse voltage is applied between the base and the emitter of the oscillation transistor 22, and the oscillation transistor 22 is turned off in an instant. When the saturation of the magnetic flux in the core is eliminated, the base current of the oscillation transistor 22 flows again in the above loop, and this operation is repeated. The voltage generated in the S winding of the oscillating transformer 27 is boosted at a winding ratio with the P winding, and energy is stored in the main capacitor 3 at the boosted voltage.

When a high level signal is not applied to the control terminal a, the transistor 23 is turned off, the loop flowing between the base and emitter of the oscillation transistor 22 is cut off, and oscillation is stopped. The resistor 21 and the capacitor 20 connected in parallel between the base and the emitter of the oscillation transistor 22 protect the base of the oscillation transistor 22 and the resistor 24 protects the base of the transistor 23. The resistor 25 is connected as a current limiting resistor from the control terminal a. The above configuration is an example of the booster circuit 2 shown in FIG. 1, but it goes without saying that a known DC / DC converter having another control terminal may be used.

Next, when energy is stored in the main capacitor 3, the terminal voltage rises accordingly, and the voltage of the main capacitor 3 is detected by the voltage detection circuit 4 shown in FIG. The operation of a specific circuit of the voltage detection circuit 4 will be described with reference to FIG. First, the output of the rectifying diode 29 is given to the main capacitor 3 via the diode 45. Further, the capacitor 41 has a potential almost equal to that of the main capacitor 3, and the terminal voltage thereof is the resistors 42, 43,
The voltage is divided by 44, and comparators 46 and 47, respectively.
Is connected to the positive input terminal of. The negative input terminals of the comparators 46 and 47 are connected to a reference voltage 48,
When the terminal voltage of the capacitor 41 reaches the shootable voltage V ₁ , the comparator 46 generates a high level output, and when the terminal voltage of the capacitor 41 reaches the full charge voltage V ₂ , the comparator 47 generates a high level signal. Is set. The respective voltage signals of the comparators 46 and 47 are configured to be given to the control circuit 106 via the control terminals b and c.

The light emitting circuit 5 is composed of a circuit including a known trigger circuit and a flash discharge tube as described above.
A trigger circuit (not shown) generates a high-voltage pulse by a high-level signal at the control terminal d, and the high-voltage pulse is applied to a flash discharge tube (not shown) to excite the discharge circuit to discharge the charging energy of the main capacitor 3, It is converted into light energy by a flash discharge tube.

The operation of this embodiment having the above configuration will be described with reference to the flowchart of FIG. First, power is supplied to the camera control circuit from the battery 1, initial settings such as resetting of each memory are performed, and the photographing operation is waited. Therefore, in step 1, it is detected whether or not the release button for shooting operation is half-pressed, that is, whether or not the first-stage release switch Sw1 is turned on. If it is on, the process proceeds to step 2, and if it is off, the process returns to the standby state. In step 2, it is confirmed whether or not the capacity of the battery 1 is sufficient for photographing, and if it is sufficient, the process proceeds to step 3, and if the battery capacity is insufficient, the process returns to the initial stage without photographing in a loop (not shown). In step 3, distance measuring information is obtained by a distance measuring circuit (not shown), focus data is calculated, and the process proceeds to step 4.

In step 4, the photometric circuit 101 obtains the brightness information of the subject to calculate the exposure data, and the process proceeds to step 5. In step 5, if the subject brightness in step 4 is low and it is determined that flash light emission is necessary, the process proceeds to step 6, and if the subject brightness is sufficient, step 9
Go to. In step 6, it is determined that the subject brightness is low in step 5 and charging is performed for flashing. The flow after this charging will be described later using the flowchart of FIG.

Therefore, a case where the subject brightness is sufficient will be described. In step 9, if the subject brightness is at a level that does not require flash emission in step 5, the input is given by waiting for the input of the switch Sw2 for the photographing operation from the first stroke to the second stroke of the half-press of the release button. Then, the process proceeds to step 10. In step 10, the lens barrel (not shown) is moved to the focus position based on the information calculated in step 3, and the process proceeds to step 11. In step 11, the shutter is opened based on the exposure information in step 4, the film is properly exposed, and the shutter is closed. After the exposure is completed, the process proceeds to step 12.

In step 12, the lens barrel that has been extended to the focus position is reset to the initial position, and the process proceeds to step 13. In step 13, the properly exposed film is wound up by one frame, and the process proceeds to step 14. In step 14, whether or not the flash light emission is used is determined by the memory data described later, and when it is used, the process proceeds to step 15 to charge the flash device. Further, when not in use, the series of sequences is finished as it is.

On the other hand, when it is necessary to use the flash device in step 5, the flow after charging in step 6 will be described with reference to the flowchart of FIG. In step 21, in order to start charging the flash device, first, a counter and a timer, which will be described later, are initially reset, and the control terminal a is set to a high level to start oscillation. In step 22, the cutoff timer is set until the image pickup voltage V ₁ is reached. In step 23, it is determined whether or not the voltage of the main capacitor 3 has reached the photographic enable voltage V ₁ . If not reached, go to step 24; otherwise, step 27
Go to. The signal at this time is detected by the high level signal of the control terminal b. In Step 24 counts down the time T _b truncation timer. In step 25, the charging time counter C counts the time required for charging. In step 26, the count-up of the set time T _b of the cutoff timer is confirmed, and if the cutoff time T ₁ = 0 has not been reached, the process returns to step 23 and the shootable voltage V ₁ is reached.
The time until the time is reached is measured within the time range given by the set time T _b of the cutoff timer.

On the other hand, when the photographable voltage V ₁ is reached in step 23, the process proceeds to step 27. In step 27, the contents of the counter C at the time when the image pickup voltage V ₁ is reached are given as time data T _C. In step 28, time data T _C
It is determined whether the value of is longer or shorter than the predetermined time T _a set in advance. If it is longer, the process proceeds to step 29, and if it is shorter, the process proceeds to step 30.

Here, if it is first determined that the time is shorter than the predetermined time T _a , in step 30, the time data t1 is set in the second cutoff timer T ₂ as a relatively new battery. When it is determined in step 28 that the time is longer than the predetermined time T _a , in step 29, the time data t2 that is larger than the time setting given in step 30 is set as the battery having a middle level of consumption. In Step 31, Step 2
Since it is determined in 3 that the image capturing voltage V ₁ has been reached, 1 is set in the memory F _CRG indicating that the charging has reached the image capturing voltage V ₁ . In step 32, it is further determined whether or not the charge level of the main capacitor 3 has reached the full charge voltage V ₂ . As described above, the full charge voltage signal is detected when the control terminal c becomes high level. Here, if the full charge voltage V ₂ is not reached, the process proceeds to step 33, and if it is determined that it is reached, the process proceeds to step 36.

If it is determined that the full charge voltage V ₂ has not been reached yet, in step 33 a down count is performed from the content t2 or t1 of the second abort timer T ₂ . In step 34, it is determined whether or not the second discontinuation timer T ₂ is counting up, and if it is within the time, the process proceeds to step 35, and when the discontinuation time is reached, the process proceeds to step 42 and the charging is stopped.

If it is determined that the time has expired, step 3
In the case of No. 5, the state in which the photographing is possible has already been reached. Therefore, if the second step stroke for photographing is pressed from the first half depression of the release button because the photographing is possible, the release button is input so as to proceed to step 42. It is determined. If the release button is not pressed, the process returns to step 32, and the charging is continued until the full charge voltage V ₂ is reached or the count-up by the second cutoff timer is performed. On the other hand, when the full charge voltage V ₂ is reached in step 32, the memory F _{CG FULL} indicating that full charge is reached is set to 1 in step 36, and the process proceeds to step 42 to stop charging. Step 3
When the termination time T ₂ = 0 of the second termination timer T ₂ is reached at 4, the process proceeds to step 42 and the charging is stopped.

On the other hand, when the first abort timer T ₁ is determined in step 26, the process proceeds to step 37. In step 37, since the photographable voltage V ₁ is not reached within the termination time T _{b of the first} termination timer T ₁ , the second termination timer T _{2 is set} to the second termination timer T ₂ as an exhausted battery,
A small time data t3 is set for the time data t2 and t1 given by 30. In step 38, it is determined whether or not the voltage of the main capacitor 3 has reached the image-capturable voltage V ₁ , and if it has reached step 41, it proceeds to step 41, and if it has not reached step 39.

When the photographable voltage V ₁ is not reached,
In step 39, the set time t3 of the _second abort timer T2 is down counted. In step 40, it is determined whether or not the second cutoff timer T ₂ has counted up, and when the cutoff time of the _second cutoff timer T ₂ is reached, step 4
Go to 2 and stop charging. Second abort timer T ₂
If the time t3 is within the range, the process returns to step 38 to continue this operation. Time t of the second abort timer T ₂
When the light emission enable voltage V ₁ is reached within the range of 3, step 41
Go to. In step 41, 1 is set in the memory F _CRG indicating that the image _pickup voltage V ₁ has been reached, and the process proceeds to step 42 to stop charging.

After that, returning to the flowchart of FIG. 4, when the charging in step 6 is completed as described above, the process proceeds to step 7. In step 7, the contents of the memory F _CRG indicating whether or not the photographable voltage V ₁ has been reached are confirmed. If the data 1 indicating that the voltage V ₁ has been reached is set, the operation proceeds to step 9 and the data is 0. If so, go to step 8. In step 8, it is also possible to perform processing due to exhaustion of the battery, for example, correction of remaining battery level display or non-display of flash photography, and the processing is ended. Steps 9 and 10
Is the same as that described above, and the shutter is controlled according to the exposure condition under which the exposure content of step 11 is the condition of using the flash device calculated in step 4 described above. Note that steps 12 and 13 are the same as those described above, and the process proceeds to step 14. In step 14, the contents of the memory (not shown) are confirmed in the flow chart showing that the flash device has been used, and if it is used, the same flow as in step 6 is followed by step 1
5 is processed, and then the photographing operation is ended.

FIG. 6 shows the relationship between the charging time and the terminal voltage of the main capacitor 3 charged according to the above-mentioned flow chart, where V ₁ is the photographable voltage, V ₂ is the full charging voltage, and T is the voltage.
₁ is the first predetermined time, T ₂ is the _second predetermined time which is longer than the first predetermined time, and t1, t2 and t3 are the abort timer times given in steps 30, 29 and 37 in FIG. 5, respectively. There is. Therefore, when the time required to reach the shootable voltage is shorter than the first predetermined time T _a, t1 is selected as the abort timer, t2 longer than t1 is selected between T _a and T _b , and longer than T _b. In the case of a depleted battery, charging is terminated in a time t3 shorter than t2 to prevent useless energy loss and poor operability due to charging. Also, here, even if the time of t1 is equal to t2,
Needless to say, there is no problem because it is configured to stop at the full charge voltage.

FIG. 7 is a diagram showing the relationship between the charging time of the main capacitor 3 and the terminal voltage for explaining the second embodiment of the present invention. The reference numerals and the flowchart for the operation are the same as those in the first embodiment. In this embodiment, the set times t1, t2, and t3 are shortened with respect to the cutoff timer, and the photographable voltage V near the first predetermined time T _a and the second predetermined time T _b.
When it reaches ₁ , stop charging with a cutoff timer,
The camera's shooting interval is set to be short. Here, there is no problem because the filming voltage V ₁ is reached in a general negative film from the film latitude. Further, it is possible to determine the case where the battery is fully charged in step 36 in the flow of FIG. 5 of the first embodiment described above, and the exposure of the shutter is corrected from the memory content indicating that the voltage is charged more than the photographable voltage in steps 31 and 41. Needless to say, more appropriate correction can be made by dividing the charging voltage of the main capacitor of the flash device and inputting it to an A / D converter such as a general microcomputer. Absent.

[0029]

As described above, the present invention provides an electronic flash of a camera including a charging circuit for a main capacitor, a voltage detecting circuit for detecting the voltage of the main capacitor, and a clock circuit which operates during charging of the main capacitor. In the device, the timer circuit measures the time from the start of charging the main capacitor until the voltage reaches the shootable voltage, and by changing the cutoff timer based on the time information, a timer time is selected that matches the degree of battery consumption. By doing so, it is possible to improve operability and prevent wasteful energy consumption.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an electronic flash device according to a first embodiment of the present invention.

FIG. 2 is a specific electric circuit diagram of the booster circuit.

FIG. 3 is also a specific electric circuit diagram of the voltage detection circuit.

FIG. 4 is a flowchart illustrating the shooting operation.

FIG. 5 is a flowchart similarly illustrating a charging operation.

FIG. 6 is a characteristic diagram showing the relationship between the charging time and the terminal voltage of the main capacitor during charging.

FIG. 7 is a characteristic diagram showing the relationship between the charging time of the main capacitor and the terminal voltage during charging in the electronic flash device according to the second embodiment of the present invention.

[Explanation of symbols]

1..Battery 2. Booster circuit 3. Main capacitor 4
..Voltage detection circuit, 5..Light emitting circuit, 22..Oscillation transistor, 27..Oscillation transformer, 41 .. Capacitor, 42, 43, 44 .. Resistor, 46, 47 .. Comparator, 106 .. Microcomputer Control circuit including.

Claims (5)

[Claims] 1. An electronic flash device for a camera, comprising: a main capacitor charging circuit; a voltage detection circuit for detecting the voltage of the main capacitor; and a timing circuit that operates during charging of the main capacitor. A first charge cutoff timer that operates when the time from the start of charging the main capacitor to the voltage at which the image pickup is possible is within a first predetermined time and a second charge time that is longer than the first predetermined time. A second charge cutoff timer and a third charge cutoff timer that operates when the second predetermined time is exceeded, and the end of the first or second charge cutoff timer and the full charge voltage, or An electronic flash device, characterized in that the charging is stopped by the signal which is the earliest of the end of the third charge cutoff timer or the shootable voltage. 2. The electronic flash device according to claim 1, wherein the charging circuit has a control terminal capable of selectively oscillating and stopping oscillation. 3. The electronic flash device according to claim 1, wherein the voltage detection circuit includes a voltage dividing resistor for dividing the voltage of the main capacitor and a comparator. 4. The electronic flash device according to claim 3, wherein the comparator comprises an A / D comparator. 5. The electronic flash device according to claim 1, wherein the timing circuit is controlled by a microcomputer.