JPS58224340A - Automatic electronic flash device - Google Patents

Abstract

PURPOSE:To realize high-speed repetitive flashing by electrifying a commutating capacitor by a main capacitor through a trigger transformer and a trigger thyristor which form a trigger circuit for a serial control type auto strobe. CONSTITUTION:When a synchro contact 19 is made, a pulse transformer 20 operates to turn on the trigger thyristor 11. Consequently, the potential of a point P3 rises to turn on a main thyristor 9 and charged charge of the main capacitor 7 is discharged to the series circuit of the primary winding 10a of the trigger transformer 10, thyristor 11, commutating capacitor 13, and main thyristor. The commutating capacitor, thyristors 9 and 11, and primary winding 10a form a single oscillation circuit, to obtain the charge voltage of the commutating capacitor nearly twice as high as that of the main capacitor. Further, a flash discharge tube 8 is triggered during the discharge.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic electronic flash device, and more particularly to a dimmable automatic electronic flash device for cameras that uses a light receiving circuit to control the timing of stopping light emission.

Conventionally, in this type of device, the trigger capacitor and the commutating capacitor were each charged via a resistor. As a result, the repetition rate of the conventional device is limited by the capacitance of the trigger capacitor and commutating capacitor used therein, and the charging time constant of the charging resistor, making it impossible to repeatedly flash at high speed.

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic electronic flash device that eliminates the drawbacks of the conventional devices mentioned above.

The present invention will be explained in detail below based on an embodiment shown in FIG. Transistor 1, capacitor 2,
An oscillation booster circuit 5 consisting of an oscillation transformer 6 and a resistor 4 is connected. The output of this oscillation booster circuit 5 is a diode 6
It is connected to the capacitor 7 through the capacitor 7. A series circuit of a flash discharge tube 8 and a main thyristor 9 as a semiconductor switching means in parallel with the main capacitor 7, a trigger thyristor 11 and a sub thyristor 12 as a semiconductor switching means forming a trigger circuit with the primary winding 10a of the trigger transformer 1o.
series circuits are connected in parallel. trigger transformer 100
The secondary winding 1ob is connected between the trigger terminal 8a of the flash tube 8 and the tangent point P1 between the cathode of the flash discharge tube 8 and the anode of the main cylisk 9.

A series circuit including a commutating capacitor 13, a capacitor 14, and resistors 15 and 16 is connected in parallel with the main thyristor 9. A connection point P2 between the commutating capacitor 16 and the capacitor 14 is connected to a connection point P4 between the cathode of the trigger thyristor 11 and the anode of the sub-thyristor 12.

A connection point P6 of resistance 15.1<S is connected to the gate of main thyristor 9.

The base of a transistor 170 whose emitter is connected to the positive terminal of the power source E is connected to the negative terminal of the power source E through a series circuit including a resistor 18 and a synchro contact 19 provided on the camera side. The collector load of this transistor 17 is the primary winding of the pulse transformer 20 @ 20 a,
A parallel circuit formed by a resistor 21 and a series circuit including a constant voltage diode 22 is connected. pulse transformer 20
The secondary winding 20b is connected between the gate and cathode of the trigger thyristor 11.

A series circuit of a light receiving element 26 and an integrating capacitor 24 in parallel with a constant voltage diode 22, a series circuit of resistors 25 and 26,
Comparator 27 is connected. The non-inverting input of the comparator 27 is connected to the connection point Q1 between the light receiving element 26 and the integrating capacitor 24, its inverting input is connected to the connection point Q2 of the resistor 25.26, and its output is connected to the gate of the sub-thyristor 12. .

In Figure 1, the main thyristor 9, sub-thyristor 12°, and the part surrounded by broken lines from 16 to 16 are the light amount control circuit A.
form. Further, the portion surrounded by broken lines from 26 to 27 forms a photometric circuit B.

One embodiment of the present invention has the above-mentioned configuration, and its operation will be explained below.

When a power switch (not shown) is turned on, the oscillating booster circuit 5 is activated and the main capacitor 7 is charged via the diode 6 to the polarity shown.

When the charging voltage of the main capacitor 7 reaches a high enough value to cause the flash discharge tube 8 to emit light, a synchro contact 19 provided inside the camera is turned on, and a pace current is supplied to the transistor 17 through the resistor 18. The pulse transformer 2 is turned on at the same time as the transistor 17 is turned on.
Current flows through the primary winding 20a of 0, as a result of which the secondary winding 2
A voltage is induced at 0b, which causes current to flow through the gate of the trigger thyristor 11, turning the trigger thyristor 11 on. When the trigger thyristor 11 is turned on, the main capacitor 7 is charged and the charge is transferred to the primary winding i of the trigger transformer 10.
oa, trigger thyristor 11, capacitor 14, resistor 1
resistor 15,1 for discharging through the series circuit of 5,16
The potential of P3, which is the connection point of P6, increases, and since this is also connected to the gate of the main thyristor 9, a part of the discharge current of the main capacitor that has flowed through the resistor 15 flows to the gate of the main thyristor 9. The main thyristor 9 is turned on. When the main thyristor 9 turns on, the main capacitor 7
The charged Tt charge is 108% of the primary winding of the trigger transformer 10.
)! It is discharged through the series circuit of the J gas thyristor 11, the commutating capacitor 16, and the main thyristor 9, and due to this discharge, υ
Commutation capacitor 16 is charged to the polarity shown. In this case, the resistance that enters the discharge path of the main capacitor charges the on-state thyristor vacitor in a short period of time. Of course, even in this case, the thyristors 11 and 9 are not destroyed by the action of the trigger transformer 100. Also, assuming that there is a Japanese dog C whose electrostatic capacitance of the main capacitor can be ignored by ignoring the capacitance of the commutating capacitor 16, from the inverse ratio 11-characteristics of the thyristors 9 and 11, the trigger transformer 10
The primary winding m10a, the commutating capacitor 16, and the thyristor 9.11 form a simple harmonic circuit, and the charging of the commutating capacitor 1 does not stop when the charging voltage of the main capacitor 7 reaches ¥4L, but continues within the circuit. If the loss is reduced to 1, the commutating capacitor 13 is charged to a voltage nearly twice the charging voltage of the main capacitor 7.

As described above, when the charge in the main capacitor 7 is discharged through the primary winding 110a of the trigger transformer 10, the secondary windings i1, 10, . The high voltage induced in the flash discharge tube 8 is applied to the trigger terminal 8a of the flash discharge tube 8).
is ionized, and since the main thyristor 9 is on at this time, the flash discharge tube 8 starts emitting light.

When some of the transistors 17 are turned on, power is supplied to the primary winding of the pulse transformer 20, and at the same time, current is supplied to the constant voltage diode 22 via the resistor 21.
The voltage generated across the constant voltage diode 220 is 23~2
7. Works as a power source for the other photometric circuit B (.

The light reflected from the subject (not shown) is converted in light quantity by the light receiving element 26, and becomes light 1! When the voltage of the integrating capacitor 24 (voltage at Ql), which generates a charging voltage according to the amount of conversion, becomes higher than the voltage at Q2, the comparator 27
The output of is reversed from low level to high level, current flows to the gate of the sub-thyristor 12, the sub-thyristor 12 is turned on, the known light amount control circuit A is activated, the main thyristor 9 is turned off, and the flash discharge tube 80 is turned off. Light emission stops.

As explained above, according to the present invention, commutation capacitor imaging can be performed. In addition, the charging voltage of the commutating capacitor can be as high as nearly twice that of the main capacitor.
In order to obtain the same energy, the static screw capacitance of the commutating capacitor can be made much smaller than in the conventional case, and this has the effect of making it possible to downsize the flashlight emitting device.

[Brief explanation of drawings]

FIG. 1 is an electrical circuit diagram showing one embodiment of the present invention. 7.000. Main capacitor 9. ..., main thyristor 10...fist... trigger transformer 11...-trigger thyristor 1ro 1111@@IT commutation capacitor

Claims (1)

[Claims] Trigger transformer, trigger thyristor, commutation capacitor,
A series circuit consisting of a main thyristor is connected in parallel with the main capacitor, and the commutating capacitor is charged by turning on the trigger thyristor and the main thyristor. :) Automatic electronic flash device for photography that allows rigging to be performed at the same time.