JPS5842600B2 - electronic flash device - Google Patents

Description

Detailed Description of the Invention The present invention connects a semiconductor switching element in series with a flash discharge tube, and when a desired amount of light is obtained when the flash discharge tube emits light, the semiconductor switching element is turned off by a control circuit, and the semiconductor switching element is turned off by a control circuit. This invention relates to an electronic flash device that can be used to control the electronic flash device.

FIG. 1 shows an example of an electric circuit of a conventional electronic flash device of this type.

In the figure, 1 is the main discharge capacitor that stores the discharge energy to be discharged into the flash discharge tube 8, and 3 is the trigger switch 5.
When the switch 5 is turned on, the trigger capacitor 4 discharges its charge to the trigger transformer 1, and when the switch 5 is turned on, the voltage charged at both ends of the trigger capacitor 4 is superimposed on the charging voltage of the main discharge capacitor 1, and the voltage at both ends of the flash discharge tube 80 is discharged. A sub-capacitor 9 for increasing the voltage is a semiconductor switching element 1, such as an SCR, which is connected in series with the flash discharge tube 8.
2 is a commutating capacitor that controls the light emission of the flash discharge tube 80 by discharging the sub-discharge tube 14; 10 is a trigger circuit for the semiconductor switching element 9; and 15 is a control circuit that detects an appropriate amount of light and controls the sub-discharge tube 8. It is.

Now, when the switch 5 is turned on with the main discharge capacitor 1, trigger capacitor 3, sub-capacitor 4, and commutating capacitor 12 fully charged from a power supply (not shown) to the polarities shown, the charged charge 3 of the trigger capacitor 3 is discharged through the primary winding of the rotation trigger transformer T,
A high voltage pulse occurs in the secondary winding of trigger transformer I,
Due to the charges in the main discharge capacitor 1 and the sub-capacitor 4, the flash discharge tube 8 discharges and emits light.

When the amount of irradiated light reaches an appropriate value, the control circuit 15 operates to make the sub-discharge tube conductive, and the charge in the commutation capacitor 12 reverse biases the semiconductor switching element 9, which turns off and flashes. The discharge tube 80 stops emitting light.

In this way, in this device, only the required amount of discharge energy from the main discharge capacitor is released and the remaining energy is stored, so that it is possible to emit light in a short repetition time.

Here, the repetition time until the next normal light emission becomes possible is as follows: the main discharge capacitor 1, the trigger capacitor 3,
It is determined by the time until charging of the sub capacitor 4 and the commutating capacitor 12 is completed again.

However, in the circuit configuration described above, current flows through the commutation capacitor 12 in a closed circuit consisting of the main discharge capacitor 1, the flash discharge tube 8, the commutation capacitor 12, and the sub-discharge tube 14 immediately after the light emission ends. As shown in FIG. 2, charging occurs in the opposite direction, and at the same time, current flows through the sub capacitor 4 and the trigger capacitor 3 in a closed circuit including the resistor 6 and the trigger transformer 7, resulting in the polarity shown in FIG. Charging is threatened.

Therefore, when the switch 5 is turned on in this state, the trigger capacitor 3 is charged as described above, and the flash discharge tube 8 discharges and emits light due to the charge remaining in the main discharge capacitor 1. .

However, in this case, the capacitor 12 that should control this light emission is connected to the auxiliary discharge tube 14 by the dimming operation of the control circuit 15.
Due to the discharge of the semiconductor switching element 9, the semiconductor switching element 9 is charged in the opposite direction to the state in which it can perform the operation of reverse biasing, and the light emission cannot be controlled. It emits light.

The present invention eliminates these drawbacks and provides an electronic flash device that does not cause erroneous light emission.

Hereinafter, one embodiment of the present invention will be explained with reference to the drawings. In Fig. 3, a diode 17 is inserted and connected between the trigger capacitor 3 and the sub-capacitor 4, so that the sub-capacitor 4 can be directly charged from a power supply (not shown). A resistor 16 is provided as shown.

Components with the same numbers as those in FIG. 1 perform the same operations.

Therefore, like the conventional device described above, there is no change in the light emission operation of the flash discharge tube 8, and after the light emission operation is completed, the commutation capacitor 12 is charged in the reverse direction as described above.

However, the flash discharge tube 8 and the resistor 6 described in the conventional example above
In the electric circuit according to the present invention, the current flowing through the primary winding of the sub capacitor 4 and the trigger transformer 7 is blocked by the diode 17 provided between the sub capacitor 4 and the trigger capacitor 3. First, charging of the trigger capacitor 3 is not affected.

Charging of the trigger capacitor 3 is started via the resistor 2 only after the light emission has ended and the commutation capacitor 12 has been charged to a normal state.

Therefore, immediately after the flash discharge tube 8 starts emitting light, even if the switch 5 is turned on, no high-voltage pulse is generated in the secondary winding of the trigger transformer T, and the flash discharge tube 8 does not erroneously emit light.

In addition, the light emission repetition time of this device is lost during the time it takes for the main discharge capacitor 1, commutation capacitor 12, trigger capacitor 3, and sub-capacitor 4 to be recharged, as in the conventional example described above. Conventional equipment & L low resistance 3
After charging of commutation capacitor 12 is completed, trigger capacitor 3 and sub capacitor 4 are charged via resistor 2, whereas in this device, sub capacitor 4 is charged via resistor 16. , the overall time constant becomes smaller and the light emission repetition time can be shortened.

As explained above, in the present invention, a diode is inserted and connected between the trigger capacitor and the auxiliary capacitor to prevent charging current from flowing into the trigger capacitor via the flash discharge tube and the auxiliary capacitor. It is possible to provide an electronic flash device that can reliably perform a light emission operation by applying , shorten the repetition time of normal light emission, and prevent erroneous light emission unlike conventional devices.

[Brief explanation of the drawing]

Figure 1 is an electric circuit diagram of a conventional electronic flash device, Figure 2 is an electric circuit diagram showing the polarity of each of the four capacitors provided in the circuit shown in Figure 1 immediately after light is emitted, and Figure 3 is an electric circuit diagram of a conventional electronic flash device. 1 is an electrical circuit diagram of an embodiment of an electronic flash device of the present invention. 1... Main discharge capacitor, 2, 6, 11, 13
゜16...Resistor, 3...Trigger capacitor, 4...Sub-capacitor, 5...
Switch, I...Trigger transformer, 8...
... Flash discharge tube, 9 ... Semiconductor switching element, 10 ... Trigger circuit for semiconductor switching element, 12 ... Commutation capacitor, 15.
...Trigger circuit of sub-discharge tube 14, 17...
··diode.

Claims (1)

[Claims] 1. A series body of a flash discharge tube and a semiconductor switching element connected in parallel to a main discharge capacitor, a commutation circuit that controls conduction of the semiconductor switching element and controls light emission of the flash discharge tube, a switch and a trigger capacitor. A trigger circuit consisting of a trigger transformer is provided between the connection point of the flash discharge tube and the semiconductor switching element and the switch, and when the switch is closed, the voltage is superimposed on the charging voltage of the main discharge capacitor via this switch. and an auxiliary capacitor provided to increase the voltage applied to both ends of the flash discharge tube, the trigger capacitor being connected between the trigger capacitor and the auxiliary capacitor via the flash discharge tube and the auxiliary capacitor. An electronic flash device characterized in that a diode is inserted and connected in such a direction that it is not charged.