JP2003347093A - Electronic flash device and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic flash device having excellent operability and chargeable with excellent efficiency. <P>SOLUTION: This device has a discharge tube, a main capacitor for storing light emitting energy of the discharge tube and a flyback type boosting circuit for boosting battery voltage. The boosting circuit is capable of controlling magnetic flux amount generated in the inside of a transformer in a first level and a second level. A boosting control circuit controls first and second boosting operations and is capable of selecting the first or second boosting operation according to a setting state of an operating member. <P>COPYRIGHT: (C)2004,JPO

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, and more particularly to a charge control.

[0002]

2. Description of the Related Art In a camera having a zoom function with a downsizing of a camera, a lens on a long focal length side becomes dark, and photographing depending on an electronic flash device has been increased. In addition, the battery used has been reduced in power supply voltage, for example, from the use of two lithium batteries to the use of one lithium battery because of portability, and smaller batteries have been employed.

In a situation where a small battery has a small electric capacity and a lens is dark on the long focal length side, and the dependence on the electronic flash device is high, a more efficient and easy-to-use electronic flash device is required. I have. Generally, when considering the usage state of a camera, the ratio of the power consumption of the flash device is very high, and it is not an exaggeration to say that the total number of times the camera is used is determined by the frequency of use of the strobe.

[0004]

However, the charging of the strobe generally tends to reduce the efficiency of the booster circuit if the charging is performed at a high speed, and the charging time tends to be reduced if the driving for increasing the efficiency is performed. is there.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electronic flash device which is built in a camera without impairing the operational feeling and has a high charging efficiency.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an electronic flash device having a discharge tube, a main capacitor for storing luminous energy of the discharge tube, and a flyback type booster circuit for boosting a battery voltage. The circuit is capable of controlling the amount of magnetic flux generated inside the transformer at the first level and the second level, and the boost control circuit controls the first and second boost operations, depending on the setting state of the operation member. The first or second boosting operation can be selected. This makes it possible to perform a step-up operation with good usability and high charging efficiency.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a circuit diagram of an electronic flash device according to one embodiment of the present invention. In this embodiment, a flyback type separately-excited converter is used as a charging device for an electronic flash device.

First, a circuit configuration of an electronic flash device will be described with reference to FIG. 1. 1 is a battery as a power supply, 2 is a semiconductor switch element for oscillation, and 3 is a resistor. Reference numeral 4 denotes an oscillation transformer having a flyback configuration, and a resistor 3 is connected as a pull-down resistor of a control terminal of the switch element 2.

Reference numeral 13 denotes a high-voltage rectifying diode, which is connected from a secondary output terminal of the oscillation transformer 4 to a main capacitor described later. 15 is a block showing a voltage detection circuit, 16 is a trigger circuit, 17 is a discharge tube, 18 is a main capacitor, and an output from the trigger circuit 16 is connected to a trigger electrode of the discharge tube 17.

The discharge tube 17 is connected in parallel with the main capacitor 18, and the voltage detection circuit 15 is connected to the main capacitor 18.
Is connected in parallel with the main capacitor 18 so as to detect the voltage of

Reference numeral 19 denotes a camera control circuit.
d and e are connection lines to the camera control unit, a is a control electrode of the switch element 2, connection line c is a drive signal line of the voltage detection circuit to the voltage detection circuit 15, and this output signal is transmitted through the terminal d. It is input to the camera control circuit 19 and detects the charging voltage of the main capacitor 18. Terminal e is the discharge tube 17
The light emission activation for operating the trigger circuit 16 for emitting light.

FIG. 2 is a block diagram of a camera control circuit for controlling the electronic flash device.

A block 125 indicated by a broken frame at the center is a camera control block composed of a microcomputer (hereinafter referred to as a microcomputer). 120 is a constant voltage block,
It is controlled from the camera control block 125 via a VCCEN terminal, and supplies a power supply VCC to each circuit block.

Reference numeral 121 denotes a switch circuit block which is operated by a battery or a VCC power supply which is a power supply for each control block of the camera, and transmits the state and change of each switch to the camera control block 125. 122 is a temperature detection circuit block, 123 is a film sensitivity detection block for obtaining information such as film sensitivity and the number of frames, 124 is a battery check circuit, 126 is a shutter drive circuit for driving a shutter, 127 is a distance measurement circuit block, and 128 is photometry. It is a circuit block and transmits necessary information to the camera control block 125 via each terminal.

Reference numeral 129 denotes a display block, for example, LC
The information required for D and the like is displayed. 130 is a lens drive circuit for driving the lens, 131 is a film drive circuit for feeding the film, and drives the film by controlling the FILMD terminal of the camera control block 125.

Next, along with the operation of the control circuit, FIG.
The operation will be described with reference to the flowchart of FIG.

Here, it is assumed that the power supply of the camera control circuit 22 has already been turned on, and in this state, the microcomputer of the camera control block 125 is in the low power consumption mode and the operation is stopped.

Here, according to the flowchart of FIG.
Initial settings necessary for the microcomputer of the camera control block 125 are performed (S1). Next, the switch detection circuit block 121
The information necessary for photographing and the setting state of the switch are confirmed based on the above information (S2).

The state of the power switch is detected in the switch detection circuit block 121, and the determination is made in S3. At this time, if the power supply SW is turned on, the control block 125 gives a signal to the low voltage circuit block 120 via the VCCEN terminal, and the low voltage block 120 supplies the power supply Vcc to each circuit block. If the power switch has not been turned on, the process returns to S2.

Next, a battery check is performed in S4. In this battery check operation, the open voltage E of the battery is
Check the battery voltage E1 by flowing 0 and the constant current I0. Based on the confirmed data, the internal resistance Rbatt of the battery is obtained from the equation of Rbatt = (E0−E1) / I0, and the battery state is determined (S5).

Of course, the present invention is not limited to this method, and another method may be used. For example, from the battery voltage E2 when a known resistor R0 is temporarily connected between the power supply lines of the battery, Rbat = R0 * (1-E0 / A method of calculating the internal resistance Rbat of the battery as in E2) may be used.
The open circuit voltage and the internal resistance of the battery are obtained by any other method to determine the battery state (S5).

The battery resistance thus obtained includes the contact resistance of a battery contact piece or the like.

At S5, the result of the battery check is N
If G, that is, if the power supply voltage is determined to be low, the camera operation is disabled and the process returns to S2.

Next, in step S6, it is checked whether or not the main flash capacitor has been charged. If the charging has not been completed, the efficiency priority driving of the flash is performed in S7. This efficiency priority driving will be described.

The operation of the microcomputer at this time will be described with reference to the flowchart of FIG.

First, at 101, the battery voltage VBAT is set to A
D-convert and obtain the voltage value. At 102, the charging voltage of the main capacitor is obtained via the voltage detection circuit 15 and A / D converted. T1 and T2 calculations performed at 103 are performed.

This T1 is for calculating the pulse width of the ON time of the semiconductor SW2.
T1 = (LI * I10) / VBAT, where L1 is the primary inductance value of the transformer 3 and I10 is the maximum primary current value.

T2 is the charging voltage of the main capacitor being V
It is determined from the inductance value L2 of the CM and the transformer secondary side, and is a time required for the secondary current to be released from the maximum value of the secondary side current and become zero.

[0029] T2 = (L2 * I10) / (N * VCM) Here, N is the ratio of the number of turns of the transformer to the primary and the secondary.

T1, T calculated at 103 at 104
The semiconductor SW2 is driven based on the time of 2. The semiconductor SW2 is kept on for the time T1. At the end of the ON period, the primary current value reaches the maximum value I10. After the elapse of the time T1, the semiconductor SW is turned off for the time T2.

At the moment when the semiconductor SW is turned off, 2
The initial current on the secondary side (that is, the maximum value) is I10 / N
And the current value becomes exactly 0 at the end of T2. In order to repeat the on / off driving, for example, the driving condition is set in a PWM port or the like of the microcomputer, and the gate driving of the semiconductor SW2, that is, the step-up operation of the transformer is performed. FIG. 5 shows a timing chart at this time.

During the period T1, the primary current of the transformer gradually increases, and when the current reaches the predetermined value I10, the transformer is turned off and the emission of the secondary current I2 starts. After the current is released during the period T2, when the value becomes zero, the semiconductor SW2 is turned on again, and the primary current starts to increase again. Thereafter, this operation is repeated to perform the boosting operation to the main capacitor.

When such driving is performed, the primary current becomes a relatively low value, and the amount consumed by the internal resistance of the battery becomes a small value, so that efficient charging is performed.
Further, the T2 off time at this time varies depending on the VCM. When the VCM is low, T2 is long, and when the VCM is high, T2 is short.

Referring back to FIG. 3, when charging is completed in S6, charging is stopped in S8.

In step S9, a first stroke signal (denoted as SW1), which is a half-pressed state of a release button for preparing for photographing, is determined. When the first stroke signal switch signal is generated, the process is branched, and in S10, any charging is temporarily stopped. If the first stroke signal switch signal has not been generated, the process returns to the switch detection routine of S2.

After returning, if there is no change in the state of SW or the like, the charging is continued, and the charging is continued until the charging voltage of the main capacitor reaches a predetermined value. If the predetermined value is reached, the charging is stopped in S8, and S9
It will wait for W1 to be turned on. Here, if SW1 is turned on in S9, charging is stopped once in S10 regardless of the state of charge in S10, and S1 is stopped.
The routine enters an AF (distance measurement) routine of No. 11.

A signal is supplied to the terminal AFEN, and the distance measuring circuit block 127 is operated to measure the distance to the subject.
The distance measurement information is transmitted from the AFD terminal to the camera control block 1.
25.

Subsequently, in S12, the photometric circuit block 12
By sending a signal to the AEEN terminal of No. 8, the luminance of the subject is measured, and this information is given to the camera control block 125 via the terminal AED. Then, in S13, it is determined from the brightness data whether the subject brightness is higher or lower than a predetermined brightness. If the brightness is low, the process proceeds to the flash mode setting in S14. The setting of the flash mode means a mode in which flash light emission is performed at the time of exposure.

In S15, it is determined whether or not the charging of the main capacitor is completed.
To perform flash stop processing. If the charging is not completed, in S16, the flash charging is performed by speed priority driving. This is already SW1, ie release SW
Is operated by the photographer, and there is a possibility that the photographing may be performed immediately. Therefore, in order to finish the pre-photographing preparation operation as soon as possible, the charging speed priority driving is performed.

Referring to FIG. 6 for explaining the speed-priority driving, the routines 101 and 102 acquire the battery voltage and the AD value of the charging voltage of the main capacitor in the same manner as in FIG.

At 105, the times T3, T4 and T5 for this speed priority driving are calculated. This T3 is to calculate the pulse width of the ON time only at the first charge initial stage. If the VBAT obtained earlier, the primary inductance value of the transformer 4 is L1, and the maximum primary current value is I10, T3 = It is calculated by (LI * I10) / VBAT.

The inductance value of the transformer secondary side is L2
The emission of the secondary current is stopped when the current value becomes a half of the maximum value of the secondary current, and the time T4 is determined so that the current flows again on the primary side. .

[0043] T4 = (L2 * I10) / (2 * N * VCM) Here, N is the ratio of the number of turns of the transformer to the primary and the secondary.

At the moment when the semiconductor SW2 is turned off, the secondary current is defined as I10 /
It starts with the current of N. This T4 also fluctuates according to the VCM similarly to T2.

Next, T5 is calculated. Since T5 is the second time or later, the on-time of the primary current control is changed. Basically, the value is set to be exactly half the value of T1 in the following equation.

T3 = (LI * I10) / (2 * VBA
In T) 106, the transformer 4 is driven, that is, the gate of the semiconductor SW2 is driven based on T3, T4, and T5 calculated above. FIG. 7 shows a timing chart of the driving at this time.

In this figure, the terminal a of the microcomputer is T3
The control is first turned on for the time, and the transformer secondary current is the maximum value I1
Reach 0. The state of the magnetic flux inside the transformer at this time is described as Φ. After the primary current reaches the maximum value, T
The current is discharged from the secondary side of the transformer to the main capacitor by performing the off control for four times.

Next, on and after the second time, the ON control is performed for T5 time, and the primary side current starts just from half the value of I10.
Reach 0. Thereafter, charging is repeatedly performed, such as turning off T4 and turning on T5.

In this speed-priority driving method,
As the average value of the primary side current, the average current amount increases as compared with the efficiency priority driving described above, so that the charging time is shortened. However, since the primary current increases, the energy consumed by the internal resistance of the battery increases, resulting in a drive that deteriorates in efficiency.

A general outline of the operation of the fly-back type boost control will be described below. The camera control block 1 shown in FIG.
9 (camera control block 125 in FIG. 2) to connection terminal a
A predetermined oscillating signal is given to the control electrode of the switch element 2 via the switch, so that high-level and low-level signals are input to the control electrode of the switch element 2.

When the control electrode of the oscillation element 2 goes high. The switch element 2 conducts, and a current flows from the battery 1 to the primary winding of the oscillation transformer 4. Therefore, the oscillation transformer 4
An induced electromotive force is generated in the secondary winding S. However, since the polarity of this current is a polarity that is blocked with respect to the high-voltage rectifier diode 13, the excitation current does not flow from the oscillation transformer 4 and the energy is oscillated. It is stored in the transformer 4.

When the connection line a goes low, the control electrode of the switch element 2 goes low, so that the switch element 2 is turned off and a counter electromotive force is generated in the secondary winding of the oscillation transformer 4. This back electromotive force is a rectifier diode 1
3. The electric charge flows through the main capacitor 18 and is accumulated in the main capacitor 18. When a high-level signal is generated again from the terminal a at the time when the energy in the oscillation transformer is released, the switching element 2 is turned on again to accumulate energy in the oscillation transformer 4 and the oscillation element 2 Is turned off, the energy stored in the oscillation transformer 4 is released, and the electric charge is charged in the main capacitor. By repeating this operation, the main capacitor 2
The voltage of 1 rises.

Returning to FIG. 3, it is determined whether or not SW1 is turned off in S18, and if it is turned off, the process returns to S2.
At this time, even if the speed-priority drive is set once in S16, if the drive has not been completed yet, the flash drive mode is changed to the efficiency-priority drive by passing through the routine in S7 again if it is not completed. Charging will be performed.

If the switch SW1 is not turned off in S18, the second stroke (full-press operation, abbreviated as SW2) of the release switch is determined in S19. If the switch SW2 is not turned on, the flow proceeds to S13. Return, and again, S14, S1
5. After passing through the routine of S16, the charging drive is continued,
When the charging of the main capacitor is completed, the charging is stopped through the routine of S17. If SW2 is on in S19, it is determined in S20 whether or not the flash mode is set. If the flash mode is set, S25 is set.
It is determined whether or not charging is completed.

If the charging is completed, the process proceeds to S21. If charging is not completed, the process returns to S15, and charging is performed again. Since this is a flash mode, light emission during exposure is not possible unless charging of the main capacitor is completed, so charging is performed. When charging is completed in S25, the process proceeds to S21.

At S21, a lens is set. This lens set performs focus adjustment by controlling the lens drive circuit block 129 based on the distance measurement data in S11. Next, shutter control and light emission control are performed in S22. This is because the shutter opening is controlled via the shutter drive circuit block 124 according to the conditions based on the brightness of the subject and the film sensitivity data obtained in S12, and when the brightness is low and light emission by the electronic flash device is required, measurement is performed. Shutter control is performed based on the distance data and the film sensitivity, and the electronic flash device emits light at an appropriate aperture value.

The light emitted from the electronic flash device is connected to the connection line e shown in FIG.
By giving a high-level signal to. When a high-level signal is applied to the connection line e, a high-voltage pulse voltage is generated at the output of the trigger circuit block 11, applied to the trigger electrode of the discharge tube 12, and the discharge tube 12 is excited.

By this excitation, the impedance of the discharge tube 12 drops at a stretch, and discharge energy of the main capacitor 13 is converted into light energy to illuminate the subject.

When the shutter is closed, the lens at the focal position is returned to the initial position (lens reset in S23). Then, the film that has been photographed is wound up by one frame by controlling the film drive circuit block 131 (S2).
4 film winding). Thereafter, the process returns to the switch detection in S2.

As described above, in the flyback converter, two levels are prepared for the amount of magnetic flux generated inside the transformer, and the driving method, that is, the efficient driving in the operation state of the release button, (The first level and the second level, the level of which is 0) and the drive with the fast charging speed (the first level and the second level) are selectively used, so that the efficiency can be improved and the charging time can be improved. An electronic flash device with a good operation feeling that can be operated quickly.

(Second Embodiment) FIG. 7 shows a flowchart as a second embodiment. This embodiment shows a configuration in which a photographer can set a charging mode to a power saving mode as an operation member. The basic flow of the entire camera is the same as that of the first embodiment, but the difference will be described (FIG. 8).

First, before SW1 is turned on, it is determined in S6 whether or not charging is completed.
In S30, it is determined whether the power saving mode is set among the various operation members. This is detected as one of various operation SW state detections in the switch detection routine of S2.

Here, if the power saving mode has been set, in S31, the drive for giving priority to the efficiency of charging the flash is performed. This content is the same as in the previous embodiment, and is operated according to the flow of FIG.

If the power saving mode is not set in S30, the flash is charged by speed-priority driving in S32. This is driven by the flow of FIG.

After the setting of the flash mode in S14, it is determined in S35 whether the mode is the power saving mode. If the mode is the power saving mode, the efficiency-priority driving is performed in S36 and the mode is set to the power saving mode. If not, speed-priority driving is performed.

After all, in this embodiment, when charging is necessary, the power saving mode is set according to the setting state of the operation member.
The driving method of charging will change.

By changing the drive in this manner, options can be given to the method of use by the photographer, so that the operation can be performed efficiently or with a sense of speed.

In the above embodiment, in the charging state of the flash, the primary current is the first level and the zero level when the efficiency is prioritized, and when the speed is prioritized, the primary current is used for the efficiency priority driving and the speed priority driving. Level and the second level.
The first level may be changed from the first level at the time of giving priority to the efficiency, and may be set to a higher current amount.

Further, in the embodiment, the second level in the drive at the time of giving priority to the speed is set to an intermediate value of the first level, but the intermediate level is not an intermediate value, but a level of 1/3 or 3/4.
It is also possible to set the level and so on.

Further, the first and second driving modes are also used during the efficiency priority driving.
Level may be provided. However, at this time, it is also possible to set a driving method in which the primary average current is smaller in the efficiency priority driving and in the speed priority driving and smaller in the efficiency priority driving and larger in the speed priority driving.

As a method of controlling the magnetic flux inside the transformer, the amount of magnetic flux can be equivalently controlled by monitoring the primary current and the secondary current of the transformer and controlling the current value.

[0072]

As described above, in an electronic flash device having a discharge tube, a main capacitor for accumulating luminous energy of the discharge tube, and a fly-back type booster circuit for boosting the battery voltage, the booster circuit has a first magnetic flux amount generated inside the transformer. The boost control circuit controls the first and second boost operations, and the first or second boost operation can be selected according to the setting state of the operation member. By doing so, efficient charging is also possible,
This has the effect that the charging time can be shortened without impairing the operation feeling of the photographer.

Further, by performing the switching of the step-up driving in conjunction with the shutter button, the photographer can be made conscious of the switching of the driving mode, and a camera having a good operational feeling can be provided.

Furthermore, the driving mode setting means (specifically, the power saving mode) can be set by the photographer, so that there is an advantage that the photographer can select.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a configuration of a camera including the electronic flash device of the present invention.

FIG. 3 is a flowchart showing the operation of the present invention.

FIG. 4 is a flowchart illustrating an efficiency priority driving according to the present invention.

FIG. 5 is a diagram showing driving waveforms during efficiency priority driving according to the present invention.

FIG. 6 is a flowchart illustrating a speed priority drive according to the present invention.

FIG. 7 is a diagram showing driving waveforms during speed priority driving according to the present invention.

FIG. 8 is a diagram for explaining a second embodiment of the present invention.

[Explanation of symbols]

1 Power battery 2 Switch element 4 Oscillation transformer 7 Oscillation transistor 15 Voltage detection circuit block 17 Discharge tube 18 Main capacitor 19 Camera control circuit block

Claims (5)

[Claims] 1. An electronic flash device comprising a discharge tube, a main capacitor for storing luminous energy of the discharge tube, and a flyback type booster circuit for boosting a battery voltage, wherein the booster circuit is generated inside a transformer. The amount of magnetic flux
And a second level. The boost control circuit controls the first and second boost operations, and can select the first or second boost operation according to the setting state of the operation member. An electronic flash device characterized by the above-mentioned. 2. The step-up operation of one of a first step-up operation and a second step-up operation controls the amount of magnetic flux generated inside the transformer to be a first level and a second level, and the other is a step-up operation. The electronic flash device according to claim 1, wherein the electronic flash device is controlled at a third level by a boosting operation. 3. A camera comprising the electronic flash device according to claim 1. 4. The camera according to claim 3, wherein the operation member is a shutter button provided on the camera body and for starting exposure. 5. The camera according to claim 3, wherein the operation member can set a drive mode for charging.