JPS5852205B2 - electronic flash device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic flash device used with a photographic camera, and particularly to an electronic flash device (hereinafter referred to as a strobe) that can output a shutter speed control signal for a photographic camera. It is.

Generally, in order to take a photo using a strobe, the photographer must manually change the shutter speed of the photo camera to a value suitable for using the strobe, and this operation may be done incorrectly or forgotten. This will lead to shooting failure.

In order to solve these problems, various strobes that can output shutter speed control signals for photographic cameras have been proposed and put into practical use.

As such a strobe, Japanese Patent Application Laid-Open No. 49-15430
No. 49-148053, these send a shutter control signal to the camera 7 side through the connection terminal between the strobe and camera, and also discharge the trigger capacitor of the strobe through this terminal. The strobe and camera are connected by two small terminals.

However, a problem common to both is that the discharge of the trigger capacitor occurs through the coupling terminal, and since the trigger capacitor is normally charged to a high voltage, the discharge of the trigger capacitor causes a spark between the coupling terminals, causing the terminal surface to become Due to damage, the electrical connection between the coupling terminals is insufficient, and the shutter control signal is not sufficiently transmitted to the camera, making it impossible to control the shutter accurately, or the trigger voltage from the trigger circuit is weak, resulting in flash discharge. This causes the problem that the tube does not emit light.

The present invention has been made to solve these problems, and will be described below with reference to the drawings.

The figure shows an electrical circuit diagram of an embodiment of a strobe according to the invention.

Now, when switch 1 is turned on, power supply 2 becomes the well-known DC-
The main discharge capacitor 4 is supplied to the DC converter circuit 3, and the high voltage output from the DC-DC converter circuit 3
charging starts.

At the same time, the terminal voltage of the power supply 2 is applied via a resistor 13 and a diode 14 to a capacitor (not numbered) and a resistor 15.
Capacitor 11. is supplied to a series body consisting of a resistor 12,
As a result, capacitors not numbered and capacitor 11 are charged.

At this time, the current flowing through the capacitor 11 is greatly influenced by the charging characteristics of the unnumbered capacitor because the unnumbered capacitor is not being charged when the switch 1 is turned on. Furthermore, resistance 15, 12
Therefore, the capacitor 11 has a characteristic that it gradually increases at the beginning of charging, and decreases from the maximum value as the charging progresses.

In this case, the value of the current flowing through the capacitor 11 is set so that the voltage drop that occurs when the maximum current flows through the resistor 12 does not cause the thyristor 16 to become conductive.・It will be controlled.

When the charging of the main discharge capacitor 4 progresses and the strobe becomes ready for use, the neon tube 5, which is a display element that detects the state of charge of the main discharge capacitor 4, lights up, and from the resistor 6, neon tube 5, and diode 7. A current flows through the series body.

Therefore, a constant voltage is generated across the diode 7 and 80 due to the voltage drop, and this voltage is connected to the ground terminal A and the B terminal, which also serves as the shutter speed control signal output terminal and the synchronization terminal, to the photographic camera. and is used as a control signal for the shutter speed of a photographic camera.

At the same time, the voltage drop across the diodes 7 and 80 mentioned above is applied between the base and emitter of the transistor 10 via the resistor 9, so that the transistor 10 becomes conductive.

When the transistor 10 becomes conductive, the charge in the capacitor 11, which was previously charged by the power supply 2 via the resistor 13, diode 14, and resistor 15, is discharged via the transistor 10 and resistor 12. Thus, the gate and cathode of the thyristor 16 are reverse biased, and the thyristor 16 is maintained in a non-conductive state.

Note that the means for obtaining the voltage used as the shutter speed control signal and for making the transistor 10 conductive between the ground terminal A and the terminal B is as follows.
Of course, a resistor or a Zener diode may be used instead of the diodes 7 and 8.

Now, consider the case where the shutter of a photographic camera is released.

In the figure, the synchronization terminal is a terminal B which also serves as a shutter speed control signal output terminal, and this terminal B is short-circuited with the ground terminal A in conjunction with the shutter release.

When the ground terminal A and the terminal B are short-circuited, the base-emitter of the transistor 10 described above is short-circuited, so that the transistor 10 becomes non-conductive.

Therefore, resistor 13, diode 14, resistor 15, capacitor 11 . A steep current flows through the resistor 12, that is, the charging current of the capacitor 11 flows, and a so-called differential pulse voltage is generated across the resistor 120, and the thyristor 16
A gate voltage is applied between the gate and cathode of the thyristor 16, and the thyristor 16 becomes conductive.

In this case, unlike when the switch 10 is turned on, the unnumbered capacitor is charged by the power supply 2, so it is possible to generate the differential pulse voltage across the resistor 120 as described above. There is no need to elaborate.

When the thyristor 16 becomes conductive, the flash discharge tube 18 and the trigger circuit 17 of the thyristor 19 operate, and the flash discharge tube 18 consumes the charge stored in the main discharge capacitor 4 and emits light.

When the amount of irradiation of the subject due to the light emitted from the flash discharge tube 18 reaches an extremely normal light amount, the thyristor 23 is brought into conduction by the light emission stop signal from the light receiving section 24, and the resistor 23 is turned on in advance.
Commutation capacitor 2 which was charged via 1 and 22
The zero charge is discharged through the thyristor 23, reverse biasing the thyristor 19 and making it non-conductive, and the flash discharge tube 18 stops emitting light.

In this way, the strobe according to the embodiment of the present invention has a flash discharge tube 1
8 is ready to emit light, that is, when the neon tube 5, which is a display element that displays the charging state of the main discharge capacitor 4, lights up, the shutter speed control signal is connected to the ground terminal A, the synchronization terminal, and the shutter speed control signal for the first time. The flash discharge tube 18 is output by short-circuiting between the earth terminal A and the dual-purpose terminal B by the shutter release of the photographic camera.
is a strobe that emits light.

It goes without saying that the photographic camera to which the strobe according to the present invention is attached has a mechanism that allows the shutter speed to be controlled by electrical signals, and also has a mechanism that allows the shutter speed to be controlled by electrical signals. In the above embodiment, the above signal is used to control the shutter speed. However, if the photographic camera has a mechanism that can change the aperture value using an electrical signal, the above signal can be used to control the aperture value. Of course, it can also be used as a control signal.

As explained above, in the present invention, even if the synchronization terminal to which the camera shutter or aperture control signal is applied is short-circuited for synchronized strobe light emission, the voltage applied to this synchronization terminal will not conduct, for example, to a transistor. Since the voltage is extremely low, which is only the base voltage of the strobe, the terminals are not damaged, and therefore a shutter or aperture control signal can be reliably applied, and it is possible to provide a strobe that can reliably perform synchronized light emission.

[Brief explanation of drawings]

The figure is an electrical circuit diagram showing an embodiment of a strobe according to the present invention. 1... Switch, 2... Power supply, 3...
...DCDC converter circuit, 4 ... Main discharge capacitor, 5 ... Neon tube, 6 ...
・Resistance, 7, 8...Diode, 9...
・Resistance, 10...Transistor, 11...
...Capacitor, 12,13,15...Resistance,
14...Diode, 16...Thyristor, 17...Trigger circuit, 18...
・Flash discharge tube, 19... Thyristor, 20...
...Commuting capacitor, 23...--Thyristor, 24... Light receiving section.

Claims (1)

[Claims] 1. A main discharge capacitor that is charged by a booster circuit to which low-voltage power is supplied when a switch is turned on; a flash discharge tube that emit light by consuming the charge of the main discharge capacitor due to the operation of a trigger circuit; Voltage generating means includes a voltage detection element that is turned on when the charging voltage reaches a voltage that allows the flash discharge tube to emit light, and a first capacitor that is connected to both ends of the low voltage power supply via the switch and outputs a predetermined voltage; a series body consisting of a transistor having a control electrode and connected to both ends of the first capacitor via a first resistor; a second capacitor and a second resistor connected in parallel with the transistor; a voltage detection element and an element connected to the control electrode of the transistor and generating a voltage that is applied to the control electrode and makes the transistor conductive when the voltage detection element is turned on; and a second element of the series body. A semiconductor switching element is connected to the connection point between the capacitor and the second resistor, and is activated when the transistor is turned off to operate the trigger circuit; a first terminal and a second terminal connected to each other; the first terminal is used to apply the voltage generated by the voltage generating element to the photographic camera as a shutter or aperture control signal; An electronic flash device in which the first and second terminals are short-circuited in conjunction with the shirt release of the photographic camera.