JPS6335078B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a dimmable flash device, particularly a flash discharge tube, which illuminates a subject and controls the extinguishing timing of the flash discharge tube by receiving the reflected light from the subject. The present invention relates to a dimmable flash device equipped with an optical circuit.

Figure 1 shows an electrical circuit diagram of a conventional dimmable flash device, where 1 is a rectifier diode, and 2 is connected in parallel with a chiyoke coil 3 to absorb the back electromotive force of the chiyoke coil 3 for suppressing discharge current. 4 is a main capacitor that stores luminous energy based on the output of an oscillation circuit (not shown) connected to terminals 0 and 0', 6 is a main capacitor that detects the completion of charging of the main capacitor 4, and connects an X contact (tuning contact). ) 5 is a trigger circuit that gives a gate signal to the first thyristor 9 when closed, 7 is a resistor provided between the gate and cathode of thyristor 9, 8 is a resistor provided in the anode circuit of thyristor 9, and 10 is a trigger circuit. capacitor,
11 is a trigger transformer, 13, 14, 18, 2
0, 22, 24 are resistors, 12, 19 are capacitors, 16 is a main thyristor connected in series to the xenon discharge tube 15 to control the amount of light emitted, 17 is a rectifier capacitor for turning off the main thyristor 16,
23 is a sub-thyristor; 25 is a light control circuit that receives reflected light from the subject with a light receiving element 26, performs time integration, and provides a gate signal to the gate of the sub-thyristor 23 when the appropriate amount of light is reached; and 27 is a light control circuit. A constant voltage element that obtains a constant voltage to operate the
28 is a limiting resistor for applying a discharge current from the capacitor 29 to the constant voltage element 27 for a certain period of time.

In the above circuit configuration, when the main switch (not shown) is closed, the output from the oscillation circuit (not shown) that boosts the low voltage power supply is applied to the main capacitor via the parallel circuit of rectifier diode 1, diode 2, and chiyoke coil 3. 4 is charged to the polarity shown. At this time, capacitors 10, 17, 19,
29 are also charged to the polarities shown.

Then, when the charging voltage of the main capacitor 4 reaches a sufficiently high value to cause the flash discharge tube 15 to flash, an indicator lamp (not shown) in the trigger circuit 6 lights up to indicate that charging is complete. When this display is displayed and the camera's The charge is applied to the constant voltage element 27 through the resistor 28 and the thyristor 9 to generate a constant voltage across the constant voltage element.

As mentioned above, the trigger signal is one of the trigger transformers.
When applied to the secondary side, the high voltage induced on the secondary side is applied to the trigger electrode 15a and ionizes the xenon discharge tube 15. Due to this ionization, the discharge current of the xenon discharge tube 15 is reduced to the capacitor 17.
- resistor 18 - applied to the gate of the main thyristor 16 via the capacitor 19, the main thyristor is turned on, and the xenon discharge tube 15 starts flashing. On the other hand, the light control circuit 25 is enabled to operate by applying a constant voltage across the constant voltage element, and when the xenon discharge tube 15 emits light, the light receiving element 26 receives the reflected light from the subject, and the light receiving element 26 receives the reflected light from the subject. Integration is performed, and when the appropriate amount of light is reached, the sub-thyristor 23 is activated by a signal from the dimming circuit 25, and the main thyristor 16 is reverse-biased by the charge of the commutating capacitor 17, making the main thyristor non-conducting and turning off the xenon discharge tube. Stops light emission.

Since the electric circuit of the conventional dimming type flash device has the above-mentioned configuration, when the X contact 5 is closed and the thyristor 9 is conductive, the charge in the capacitor 29 is applied to the constant voltage element 27. In order to obtain a constant voltage across both ends of the thyristor, a diode 21 with a high withstand voltage and forward current rating is connected between the cathode electrode of the main thyristor and the cathode electrode of the sub thyristor.
must be connected. Therefore, in order to ensure commutation, it was necessary to increase the capacitance of the commutation capacitor 17 in consideration of the loss of the diode. Further, in other known examples of power supply voltage generation circuits for the above-mentioned dimming circuits, an inverting circuit or the like is required for polarity matching, which complicates the circuit configuration.

The present invention has been proposed in view of the above, and eliminates the need for a diode connecting the cathode electrode of the main thyristor and the cathode electrode of the sub-thyristor for commutation of the main thyristor, reduces the number of component parts, and simplifies the circuit configuration. It is an object of the present invention to eliminate the need to increase the capacitance of the commutation capacitor of the main thyristor.

Hereinafter, an embodiment of the present invention will be described with reference to FIG. In FIG. 2, the cathode electrode of a constant voltage element 27 that supplies a constant voltage to the dimming circuit 25 is connected to the cathode electrode of a thyristor 9 as a semiconductor switch that operates in synchronization with the closing of the X contact 5. The anode electrode of the constant voltage element 27 is connected to the main thyristor 1.
6 and the connection point between the cathode electrode of the sub thyristor 23 and the negative electrode of the main capacitor 4. Note that the other circuit configurations are the same as in FIG. 1, so explanations will be omitted.

In this embodiment, the main capacitor is charged to the illustrated polarity through a closed loop of rectifier diode 1 - parallel circuit of diode 2 and choke coil 3 - main capacitor 4 - constant voltage element 27, and other circuit operations are as shown in FIG. The same is true.

That is, the present invention provides a main capacitor 4 that stores charge as the light emission energy of the flash discharge tube 15, a first thyristor 9 that is turned on in synchronization with the closing of the tuning contact 5, and a main capacitor 4 that is connected in parallel to the first thyristor. Trigger capacitor 10 and trigger transformer 11
When the first thyristor 9 is turned on, the charge pre-charged in the trigger capacitor 10 is discharged, and the trigger transformer 11
A high voltage is generated in the secondary coil of the flash discharge tube 1.
5, and a trigger circuit 16 that is connected in series with the flash discharge tube 15 and is turned on in conjunction with the turn-on of the first thyristor 9 to form a closed loop between the main capacitor 4 and the flash discharge tube 15. It has a main thyristor 16 that discharges accumulated charge into a flash discharge tube 15, and a light receiving element 26 that receives reflected light from a flash from a subject, and integrates the amount of light received by the light receiving element, and when the integrated value reaches a predetermined voltage. A dimming circuit 25 that generates an output when the dimming circuit 25 is turned on, and a commutating capacitor 17 that is a thyristor that is turned on by the output of the dimming circuit and that is connected between the anode electrode of the thyristor and the anode electrode of the main thyristor 16. A dimming type flash device comprising a sub thyristor 23 which applies charge to the main thyristor 16 in a reverse bias direction to turn on the main thyristor, the cathode electrode of the first thyristor 9 and its cathode electrode. a constant voltage element 27 to which is connected, and the first thyristor 9
One end is connected to the positive electrode of the main capacitor 4 via the anode electrode and resistor 8, and the other end is connected to the anode electrode of the constant voltage element 27 and the main and sub thyristor 1.
A series body of a resistor 28 and a capacitor 29 is provided which is connected to the cathode electrodes 6 and 23, and further to the connection point with the negative electrode of the main capacitor, and the charge pre-charged in the capacitor 29 of the series body is transferred to the capacitor 29 of the series body. When the first thyristor 9 is turned on, a discharge is caused via the first thyristor 9 and the constant voltage element 27,
A dimming type characterized in that the constant voltage element 27 generates a constant voltage, and the dimming circuit 25 connected between the cathode electrode and the anode electrode of the constant voltage element 27 is operated at the constant voltage. It is a flash device.

By having the above circuit configuration, the present invention provides
The diode between the cathode electrode of the main thyristor and the cathode electrode of the sub-thyristor for commutation of the main thyristor, which was conventionally necessary, can be omitted. As a result, there is no need to correct the loss caused by the diode, and the capacitance of the commutating capacitor may be small. Furthermore, the number of components can be reduced due to the elimination of diodes, thereby simplifying the circuit configuration.

[Brief explanation of the drawing]

Figure 1 is an electrical circuit diagram of a conventional dimmable flash device.
FIG. 2 is an electrical circuit diagram of the dimmable flash device of the present invention. 15 is a xenon discharge tube, 16 is a main thyristor,
23 is a sub-thyristor, 25 is a dimming circuit, 26 is a light receiving element, and 27 is a constant voltage element.

Claims (1)

[Scope of Claims] 1. A main capacitor that stores charge as the light emission energy of the flash discharge tube, a first thyristor that turns on in synchronization with the closing of the tuning contact, and a main capacitor that is connected in parallel to the first thyristor. When the first thyristor, which includes a series body of the trigger capacitor and the primary coil of the trigger transformer, is turned on, the charge pre-charged in the trigger capacitor is discharged, and a high voltage is generated in the secondary coil of the trigger transformer, resulting in a flash discharge. a trigger circuit that triggers the flash discharge tube; and a trigger circuit that is connected in series with the flash discharge tube and turns on in conjunction with the turn-on of the first thyristor to form a closed loop between the main capacitor and the flash discharge tube, and transfers the accumulated charge of the main capacitor to the flash discharge tube. a main thyristor that discharges light to and a thyristor that is turned on by the output of the dimming circuit, the electric charge of a commutating capacitor connected between the anode electrode of the thyristor and the anode electrode of the main thyristor being reverse biased with respect to the main thyristor. a sub-thyristor that turns on the main thyristor by applying an electric current to the cathode electrode of the first thyristor; One end is connected to the positive electrode of the main capacitor via an anode electrode and a resistor, and the other end is connected to the anode electrode of the constant voltage element, the cathode electrodes of the main and sub thyristors, and further to the connection point with the negative electrode of the main capacitor. A series body of a resistor and a capacitor is provided, and when the first thyristor is turned on, the charge pre-charged in the capacitor of the series body is discharged via the first thyristor and a constant voltage element, and the constant voltage is A dimmable flash device characterized in that a constant voltage is generated in an element, and the dimming circuit connected between a cathode electrode and an anode electrode of the constant voltage element is operated at the constant voltage.