JPH0455285B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic flash device, and more particularly to a flash device having at least two capacitors for storing flash energy.

Conventionally, in electronic flash devices, the voltage at which light can be emitted is set depending on the type of xenon tube, so if you reduce the capacity of the capacitor in an attempt to shorten the flash interval, the amount of flash light will become smaller and the guide number will become lower, making it possible to take pictures. The disadvantage was that the distance was limited. In view of this, the capacitor of the electronic flash device is divided into a second capacitor with a relatively large capacity and a first capacitor with a relatively small capacity, and charging of the second capacitor is prohibited when the strobe device is powered on. After the charging of the first capacitor is completed by the signal of the detection means that charges the first capacitor and detects the charging of the first capacitor, charging of the second capacitor is started and the second capacitor is charged.
By the method of enabling the first capacitor to emit light before the charging of the second capacitor is completed, the generation interval is shortened, and the amount of flash light emitted at the time of light emission increases as the charge accumulates in the second capacitor. A similar flash device was proposed in Japanese Patent Application No. 195661-1983. However, in order to shorten the generation circuit, the first
If the capacitor is made small, the first capacitor will be discharged because the detection means detects the charging of the first capacitor while the second capacitor is being charged. Therefore, if the first capacitor is made smaller in order to shorten the light emission interval, the above-mentioned discharge may cause the terminal voltage of the first capacitor to drop below the voltage that can be generated by the Canon tube, making it impossible to emit light. It was hot.

The present invention has been made in view of the above-mentioned matters, and has the following features: a first flash energy storage capacitor connected in parallel to each flash tube, and a capacitor having a larger capacity than the first flash energy storage capacitor. a second flash energy storage capacitor; a power supply circuit that supplies charging current to the first and second capacitors; and a power supply circuit connected to the second flash energy storage capacitor and configured to charge the second flash energy A switching means for prohibiting the supply of charging current to the storage capacitor is provided, and after the power supply circuit starts supplying the charging current to the first and second capacitors,
activating the switching means at a predetermined time point before the release operation to prohibit charging of the second flash energy storage capacitor and quickly complete charging of the first flash energy storage capacitor;
It is an object of the present invention to provide a flash device that eliminates the above-mentioned drawbacks.

In the embodiment described below, the xenon tube 37 (Fig. 1) corresponds to a flash tube,
The capacitor 30 (Fig. 1) corresponds to the first flash energy storage capacitor, and the capacitor 39
(Fig. 1) corresponds to the second flash energy storage capacitor, which includes a battery 21, a transformer 26, a transistor 27, a capacitor 28, and a resistor 29 (the first flash energy storage capacitor).
) corresponds to the power supply circuit, and the transistor 86 (FIG. 1) corresponds to the switching means.

FIG. 1 is a circuit diagram of a first embodiment of the present invention, and FIG. 2 is a diagram showing charging curves of a first capacitor and a second capacitor of the embodiment of the present invention.

In FIG. 1, 20 is a power switch for the flash device, 21 is a power battery, 23, 24, 25 are reverse voltage prevention diodes, and 26 is an oscillating transistor, which together with a transistor 27, a capacitor 28, and a resistor 29 constitute a known oscillating circuit. .

30 is a first capacitor having a relatively small capacity. Resistor 31, capacitor 32, switch 3
3. The trigger coil 36 constitutes a known trigger circuit. 37 is a xenon tube, 38 is a reverse current prevention diode, 39 is a second capacitor with a relatively large capacity, and 41 is a reverse current prevention diode. 86 is a second capacitor charge switching transistor, 87 is a pull-down resistor connected to the base of transistor 86, and 100 is a signal indicating that the first stroke of a release button (not shown) has been pressed from the camera side to the flash device. This is a terminal for input. 101 is a capacitor for forming a time constant circuit together with resistors 102 and 104; 105 and 109 are transistors that control the oscillation of the oscillation circuit; and 106 is the capacitor 10.
1 is a short-circuit transistor, 107 is a pull-down resistor connected to the pace of transistor 106,
Normally, the b side is on, and the switch is switched to the a side in response to a signal input from the terminal 100 indicating that the first stroke of a release button (not shown) has been pressed.

In Figure 2, the vertical axis is voltage V ₁ and the horizontal axis is time T.
, where A is the charging curve of the first capacitor,
B is the charging curve of the second capacitor, C is the voltage at which stable light emission is possible for the xenon tube 37, D is the point at which the a side of the switch 108 is turned on, and D' is the point at which the first capacitor reaches the voltage at which stable light emission is possible. show.

Next, the operation of the first embodiment of the present invention constructed as above will be explained. Power switch 20
When turned on, diode 23 and oscillation transformer 2
6, transistor 27, capacitor 28, resistor 2
The oscillator circuit consisting of 9 is started and the first capacitor 30 and the resistor 31 are
Charging of the capacitor 32 begins through the trigger coil 36, and at the same time, charging of the second capacitor 39 begins through the diode 24 and the transistor 86. When the charging of the first and second capacitors progresses and the first stroke of the release button (not shown) is turned on at time D in FIG. 2, the switch 10 is activated.
8 is switched to the a side, and the transistor 86 is turned off, so that charging of the second capacitor 39 is prohibited, and only the first capacitor 20 and the trigger capacitor 32 are charged. At the same time, the transistor 106 turns off and the capacitor 101 becomes the resistor 1.
Charging begins with the divided voltage of 02 and 104.
When a predetermined period of time has elapsed and the time shown on the time axis D' in FIG. 2 comes, and the charging of the capacitor 101 has progressed beyond the voltage V _BE between the transistors, the transistor 105 is turned on, the transistor 109 is also turned on, and the oscillation stops. do. Thereafter, the second stroke of the release button (not shown) is pressed, the switch 33 is turned on, and light is emitted.

Next, a second embodiment of the present invention will be described.

FIG. 3 shows a second embodiment of the invention.

In FIG. 3, elements having the same functions as those in the first embodiment shown in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 3, 111 connects the terminal voltage of the first capacitor 30 to resistors 117 and 118.
114 and 115 are D-flip-flops (hereinafter referred to as D-FF), and 116 is an OR gate.

Next, the operation of the embodiment configured as above will be explained.

When the strobe power switch 20 is turned on, the oscillation circuit starts oscillating, and charging of the first capacitor 30, second capacitor 39, and trigger capacitor 32 starts. The first stroke of the release button (not shown) is pressed and the switch 10 is pressed.
At the same time as the movable contact piece 8 leaves the b side, the transistor 86 is turned off, charging of the second capacitor 39 is prohibited, and the first capacitor and the trigger capacitor are charged. At the same time that the movable contact piece of the switch 108 is switched to the a side, the clock terminal of the D-FF 114 and the terminal D of the D-FF 115 become H level. Further, as the charging of the first capacitor 30 progresses and the voltage of the first capacitor becomes higher than the voltage C at which stable light emission is possible, the output of the comparator 111 is inverted from the L level to the H level, and the terminal D of the D-FF 114,
The clock terminal of D-FF115 becomes H level.

Therefore, after the voltage of the first capacitor 30 and the second capacitor 39 reaches a voltage C or higher that enables stable light emission, a signal indicating that the first stroke of the release button has been pressed is input from the camera side via the terminal 100 and the switch 108 is activated. When switches from side b to side a, D-
The output terminal Q of the FF 114 is inverted from L level to H level, transistor 105 is turned on, and therefore transistor 109 continues to be turned on, thereby stopping oscillation.

Furthermore, if the first stroke of the release button is pressed from the camera side and the switch 108 is switched from the B side to the A side before the first capacitor 30 and the second capacitor 39 are charged to the voltage C that enables stable light emission, the transistor 86 is turned off, charging of the second capacitor 39 is prohibited, and only the first capacitor 30 and the trigger capacitor 32 are charged. When charging progresses and the voltage of the first capacitor 30 becomes higher than the voltage of the reference power supply 112 connected to the inverting input side of the comparator 111, the output of the comparator 111 is inverted from L level to H level, and the output of D-FF 115 Terminal Q is inverted from L level to H level, transistor 105 is turned on, and oscillation is stopped. In the first embodiment, charging of the second capacitor 39 is prohibited for a predetermined time set in a timer means composed of a capacitor 101 and resistors 102, 104, and the first capacitor 30 is charged. The voltage of the capacitor was configured to be charged to at least the stable light emission voltage C, whereas in this embodiment, the first and second
If the first stroke of the camera release button is pressed before the capacitor reaches the voltage C that enables stable light emission, the comparator 111, the reference power source 112,
Since oscillation is stopped by the output of the circuit that detects the voltage of the first capacitor 30 composed of resistors 117 and 118, the charge level of the first capacitor can be brought to an appropriate level. In the embodiment of the present invention, a signal indicating that the camera is at least immediately before film exposure is transmitted from side b to a in conjunction with the first stroke of the camera's release button.
Although the signal is from the switch 108 that switches to the side, if the capacity of the second capacitor is sufficiently small, it may also be a signal from a switch that turns on in conjunction with the second stroke of the release button.
In an autofocus camera, the signal may be sent from the second switching means after the autofocus operation is completed.

In this embodiment, a terminal 100 receives a signal indicating that the camera is about to expose the film, and a terminal 100 receives a signal for driving the switch 108.
However, the switch 108 may be provided outside the flash device, and the terminal may receive a signal generated by driving the switch 108. It goes without saying that the switch 108 may be replaced by other switching means.

Furthermore, in this embodiment, during flash photography, the first capacitor and the second capacitor are charged, and the second capacitor is charged until at least the charging of the first capacitor is completed after the signal of the terminal is detected. In the first embodiment, the capacitor 101 and the resistors 87, 102, 10 are used as control means to prohibit charging of the first capacitor and charge only the first capacitor.
3,104,107, transistor 86,10
5, 106, switch 108, resistors 87, 113, 117, 118 in the second embodiment,
Although the configuration is made up of a reference voltage 112, D-FFs 114 and 115, an OR gate 116, and transistors 86 and 105, it is of course not limited to this configuration. The timer means for setting the time may also be constituted by other digital timer means, or a neon tube may be used instead of detecting the terminal voltage of the first capacitor with a comparator, or other means may be used. The detection means may also be comprised of the following detection means.

As described above, according to the present invention, the electronic flash device has a first capacitor with a relatively small capacity for storing energy for flash emission, a second capacitor with a relatively large capacity, and a camera at least immediately before film exposure. a terminal that receives a signal indicating that the first capacitor and the second capacitor are charged during flash photography; Since the second capacitor is equipped with a control means that prohibits charging of the second capacitor and charges only the first capacitor, it becomes possible to emit light even though the second capacitor is not charged to a voltage that allows emitting light, and the light emitting interval is In addition, the first capacitor with a smaller capacity can be charged first, and the second capacitor can be charged after the first capacitor is fully charged.
The first capacitor is charged, and the first capacitor is discharged before the second capacitor is fully charged, thereby preventing the first capacitor from being able to emit light during photographing.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of the first embodiment of the present invention;
FIG. 3 is a diagram showing charging curves of a first capacitor and a second capacitor according to an embodiment of the present invention, and FIG. 3 is a circuit diagram of a second embodiment of the present invention. 30...First capacitor, 39...Second capacitor, 108...Switch, 86...Transistor, 38...Diode.

Claims (1)

[Claims] 1. The first one connected in parallel to each flash tube.
a flash energy storage capacitor;
a second flash energy storage capacitor having a larger capacity than the flash energy storage capacitor, a power supply circuit that supplies charging current to the first and second capacitors, and the second flash energy storage capacitor. A switching means is provided which is connected to the capacitor and prohibits the supply of charging current to the second flash energy storage capacitor by switching, and after the power supply circuit starts supplying the charging current to the first and second capacitors. A flash device characterized in that said switching means is operated at a predetermined time point before a release operation.