JPS60232699A - Flashing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flash device, and more particularly to a safety circuit for a flash device.

Usually, a so-called series dimming type flash device has a configuration in which a main thyristor is connected in series to a discharge tube, and a series body of a commutating capacitor and an auxiliary thyristor is connected in parallel to the main thyristor.

In a series dimming type flash device with such a configuration, a transceiver or the like is used near the flash device while the main capacitor is being charged, and a strong electric field is applied to the gate of the sub-thyristor, causing a malfunction (the sub-thyristor turns on). Then, current will continue to flow through the commutator capacitor charging resistor connected in series with the sub-thyristor, which may cause serious problems such as failure to emit flash light or the resistor overheating and causing a fire. be.

Conventional methods for solving this problem include increasing the holding current of the auxiliary thyristor, and configuring the charging resistor with a fuse resistor. However, the former method has the drawback that when the sub-thyristor turns on, the voltage between its anode and cathode increases, worsening the turn/off characteristics for the main thyristor, and the latter method has the disadvantage that once the fuse resistor is activated, Since the wire is disconnected, there are inconveniences such as not being able to charge the commutation capacitor from the next time onwards.

The present invention has been made in view of the above-mentioned matters, and is a power supply circuit (1.2.s, io of the embodiment) that supplies a light heavy current to the main capacitor (Embodiment 19).

11.12), a series body of a flash tube (Example 24) and a main thyristor (Example 25) connected in parallel to the main capacitor, and a transformer connected in parallel to the main thyristor. A series body of a current capacitor (Example 27) and a sub-thyristor (Example 30), and a commutating capacitor whose one end is connected between the commutating capacitor and the sub-thyristor and the other end is connected to the main capacitor. In the flash device, which is equipped with a charging resistor (Embodiment 29), turns on the sub-thyristor, reverse biases the electric charge of the commutating capacitor to the main thyristor, and stops the flash emission, and the reduction in the anode potential of the sub-thyristor is A detection circuit (34 to 36 in the embodiment) for detecting the detection and a prohibition circuit (6°9 in the embodiment) for prohibiting charging of the main capacitor from the power supply circuit in response to the output of the detection circuit are provided to prevent malfunction. When the auxiliary thyristor turns on, the power supply from the power supply circuit is cut off to prevent current from continuing to flow to the charging resistor of the commutation capacitor.

Next, the flash device pressure according to the present invention will be explained. 1st
The figure is a circuit diagram showing an embodiment of a flash device according to the present invention.

In the figure, 1 is a power battery, and 2 is a power switch. When the switch 2 is turned on, a transistor 8, a resistor 10, a capacitor 11, and a transformer 12, which constitute a booster circuit, are activated. A diode 219 13 rectifies the boosted output and is a main capacitor that stores flash energy, and the capacitor 19 is charged by the output of the booster circuit.

38 is a resistor connected in series to the trigger capacitor 22 and the primary winding of the trigger transformer 23; a thyristor connected in parallel to the trigger capacitor 22 and the primary winding of the transformer 23; A resistor 21 is connected. These resistors 28
．． The 21° capacitor 22 and the thyristor 20 constitute a known trigger circuit, which is activated when a voltage is applied between the ground terminal T3 and the synchro contact terminal 17 when the synchro switch of the camera is turned on to trigger the flash tube 24.

25 is the main thyristor connected in series with the flash tube 2tK, 2
7 is a commutating capacitor connected between charging current resistors 29 and 28, 30 is a rigid thyristor connected in parallel with the commutating capacitor 27 and resistor 28, and these resistors 2
9.28, a capacitor 27, and a thyristor 30 constitute a known commutation circuit. The gate of the sub-thyristor is connected via terminal T4 to the output of a dimming circuit consisting of a light amount integrating circuit and a comparator provided in the camera, and the output of the dimming circuit is generated when the output of the integrating circuit reaches a predetermined value. It turns on in response to a light emission stop signal from.

14 is a resistor 16, 17, and 18 that divides the voltage of the booster circuit output. Ten power is connected to the voltage dividing point of resistors 16 and 17 of 18, and the output of battery 1 is connected to the power by resistor 3 and Zener diode 4. This is a comparator to which a reference voltage Vref obtained by applying it to a series circuit is applied.

36 has one input terminal applied with a divided voltage from a voltage dividing resistor 34 and 35 that divides the potential at the connection point between the capacitor and the resistor 29, and the reference voltage Vre applied to its tenth input terminal.
It is a comparator to which f is applied.

37[1e Comparator 14. This AND gate receives the outputs of 36 and outputs H only when the outputs of the co-comparators are both at high level (hereinafter referred to as H). Reference numeral 6 denotes a transistor whose pace is connected to the output of the AND gate 37 and whose collector is connected to the base of the transistor 9. These transistors constitute an oscillation operation stop circuit of the booster circuit.

Reference numeral 15 denotes a comparator to which the divided potential of the resistors 17 and 18 is applied to the voltage, and the reference voltage Vref is applied to the voltage.

The flash device shown in the first diagram receives reflected light from a subject due to flash light emission on a shutter surface, integrates the amount of received light, and transmits a light emission stop signal to the terminal T4 when the integrated output reaches a predetermined value. It is assumed to be used for a TTL light control type camera.

Next, the operation of the embodiment shown in FIG. 1 will be explained. first,
Power switch 2f: When turned on, the power supply battery 1 is connected to the booster circuit and the booster circuit is activated. As a result, charging of the capacitor 9 is started by the booster circuit output.

On the other hand, when the main capacitor 9 is charged, the commutating capacitor 27 is also charged with a charging current flowing through the resistors 29 and 28. While the capacitors 19 and 27 are being charged in this manner, their respective charging potentials are detected by the comparators 14 and 36. This comparator 14.36 full! The potential detection operation is as follows.

(1) When charging is started by turning on the power switch 2 In this state, the comparator 14 is at a low level (hereinafter referred to as "low level").
The comparator 36 outputs H.

(2) When the capacitor 27 is charged to a predetermined level, in this state, the comparator 36 outputs L, and the comparator 14 outputs L.

(3) When the charging of the capacitor 19 progresses from the state of (2) and the capacitor 19 is charged to a predetermined level, the comparator 14 outputs H and the comparator 36 outputs L in this state.

As described above, since the charge level of the capacitor 19.27 is detected by each comparator 14.36,
It outputs L through the charging process of AND gate 37V'i capacitor 19.27, and transistor 6.9
is maintained in an off state, the booster circuit continues to operate, and the above-mentioned capacitors 19 and 27 are charged.

In this way, capacitor 19.27 is charged and further (
Proceeding from state 3), when the charge level of the capacitor 19 is charged to a level that allows flash photography, an H signal is sent from the comparator 15, and this H signal is sent to the terminal T1.
is transmitted to a known mode switching circuit of the camera, and the exposure control mode of the camera is switched from daylight mode to flash mode.

Thereafter, when the camera (not shown) is released and the shutter front curtain runs, the synchro switch is turned on when the shutter front curtain is fully opened, voltage is applied between the terminals Tt and T, and the thyristor 20 is turned on.

Since the capacitor 22Vi is charged during the charging process of the main capacitor 19 mentioned above, the electric charge of the capacitor 22 is transferred to the trigger transformer 2 when the thyristor 20 is turned on.
30 winding and triggers the flash tube 24.

On the other hand, the trigger state of the flash tube 24 by the transformer 23 is detected by the capacitor 32 and the resistor 31, and H is transmitted to the gate of the main thyristor 25 using a known method to turn on the thyristor 25. As a result, the charge in the flash tube 24Vi capacitor 19 is discharged and flash light is emitted.

On the other hand, in a camera, the light reflected from the subject due to the flash light emission is received on the shutter surface or film surface, the amount of received light is integrated, and when the integrated value reaches a predetermined level, a light emission stop signal is outputted to the terminal T4. Inform the thyristor 30 via the wire.

Thyristor 30 is turned on in response to the light emission stop signal, and the charge in capacitor 27 is discharged through thyristor 30, reverse biasing thyristor 25 and turning off thyristor 25.

Also, at this time, current flows through the flash tube 24 and the sub-thyristor 30 to the commutation capacitor 27, reversely charging the commutation capacitor, turning off the flash tube Z4, and stopping the flash. Since bias is applied between the anode and cathode of the sub-thyristor, the sub-thyristor
30 means the flash light emission stops! It turns off at the same time.

As described above, when the above commutation operation is performed by turning on the sub-thyristor 30, the comparator 36 sends out H while the thyristor 30 is on, and at this time, the main capacitor
Assuming that a sufficient amount of charge remains in 19, since comparator 14 also sends out H, AND gate 37 also sends out H. Therefore, the transistor 6.9 turns on and the transistor 8 turns off, making the booster circuit inoperable. However, as mentioned above, the thyristor 30 turns off almost at the same time as the flash stops, and then the commutating capacitor 27 connects to the main capacitor 19. Since it is charged with electric charge and the charge level rises in about 0.2 seconds, the comparator 36 immediately sends out KL. Therefore, the above-mentioned operation stop operation for the booster circuit is canceled and the pressure capacitor 19 is turned off for the next photographing.
As a practical matter, charging starts at approximately 0.2
Stopping the oscillation operation for about seconds has almost no effect on continuous light emission.

The normal flash photography operation is executed by the above operation, but for example, when the power switch 2 is turned on and the main capacitor 19 is being charged, when the flash is used near the flash device for a tiger/seaper collar. If noise is input to the gate of the sub-thyristor and the sub-thyristor 30 malfunctions and turns on, the sub-thyristor 30 will be kept in the on state.

That is, in this case, since the thyristor 30 is turned on while the flash discharge tube 24 is not emitting light, the thyristor 3
The above-mentioned off operation for 0 is not performed and thyristor 3
0 is held on, so that current flows from the booster circuit to the resistor 29, and if it continues, it will generate heat and cause a fire ring accident. Therefore, in the present invention, when the sub-thyristor 30 is inadvertently turned on as described above, the booster circuit is deactivated and the thyristor 30 is automatically turned off.

To explain in detail, as described above, the thyristor 30
When turned on, the output of the converter 36 immediately sends out an H level, and the output of the AND gate 37 becomes an H level.

Therefore, as described above, the booster circuit becomes inactive, thereby preventing power from being supplied to the resistor 29 from the booster circuit.

Further, at this time, charging of the main capacitor 19 is also stopped, and the electric charge stored in the main capacitor 19 is discharged via the thyristor 30. As the capacitor 19 discharges, the charge level of the main capacitor decreases, and this level causes the output of the comparator 14 to become L.
When the current value decreases to a level slightly higher than the level at which the current is reversed, the current value flowing through the thyristor 30 becomes less than the holding current level, and the thyristor 30 shifts from on to off and returns to its initial state.

In this way, when the thyristor 30 returns to its initial state, that is, off, the remaining charge in the main capacitor causes the capacitor 2 to
7 is charged, the output of the converter 36 becomes L, and the output of the AND gate 37 also shifts to L. Therefore, the booster circuit starts operating again, and the charging operation to the main capacitor resumes as described above.

As described above, in the present invention, the anode potential (charge level of the commutation capacitor) of the auxiliary thyristor is detected, and when the potential drops while charging the main capacitor, the booster circuit is made inactive. Therefore, even in such a case, it is possible to prohibit the power supply to the charging resistor after a predetermined time, and it is possible to prevent the inconvenience caused by the continued flow of the resistor IC9i current, and to restore the circuit state to the initial state. This allows the flash preparation operation to be started immediately.

In the example, 1flT T Lv! Although an example of use with a four-light camera has been described, it is clear that the present invention can be applied to a normal auto strobe by connecting the output of the dimming circuit to the gate of the thyristor 30.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a flash device according to the present invention. 27... Commutation capacitor, 3o... Sub-thyristor, 36... Comparator, 37... AND gate, 29... Resistor, 6.8.9... Transistor, 12... Trance.

Claims (1)

[Claims] A power supply circuit that supplies charging power to the main capacitor, a series body of a flash tube and a main thyristor connected in parallel to the main capacitor, and a commutating capacitor and a sub-thyristor connected in parallel to the main thyristor. a series body, and a commutating capacitor charging resistor having one end connected between the commutating capacitor and the sub-thyristor and the other end connected to the main capacitor, and turning on the sub-thyristor and charging the commutating capacitor. A flash device that reverse biases a main thyristor to stop flash emission includes a detection circuit that detects a drop in the anode potential of the sub thyristor, and a detection circuit that charges the main capacitor from the power supply circuit in response to the output of the detection circuit. A flash device characterized by being provided with a prohibition circuit.