JPS5853530Y2 - Electronic Flash Warehouse - Google Patents

Description

[Detailed Description of the Invention] Currently, there are some devices in which an automatic flash timer switching circuit (hereinafter referred to as an FPS circuit) is added to an electric shutter circuit.

And, this FPS circuit is, for example,
It is incorporated into a camera together with an electric shutter as disclosed in Japanese Patent No. 77.

In such an FPS circuit, a switching transistor is connected in parallel to the photoconductive element of the adjustment value circuit that determines the shutter time, and the transistor is made conductive by a time constant signal of a time constant circuit consisting of a resistor and a capacitor.
Further, this time constant circuit becomes operational when the electroflash device is plugged in, and a synchronizing contact is connected in parallel to the capacitor of the circuit.

Therefore, if the synchro contact is opened during flash photography, the switching transistor will become conductive in response to the time constant signal of the time constant circuit, so that the capacitor of the adjustment value circuit will be charged via this transistor. , so that the shutter stays for a certain period of time (e.g.
1/30 seconds).

According to this conventional FPS circuit, the shutter closes for a certain period of time even when the amount of light emitted is insufficient, thereby avoiding the adverse effects of camera shake and eliminating the risk of the shutter remaining open. It has a profit.

However, according to the FPS circuit described above, the shutter time remains constant regardless of whether the flash device actually fires or not, so if the main capacitor of the flash device is not sufficiently charged, It has the disadvantage of underexposure when it does not emit light due to careless shooting or other reasons.

This invention is intended to solve the above-mentioned malfunction of the FPS circuit, and will be described in detail below with reference to one embodiment shown in the drawings.

B in the figure shows an FPS circuit, and by connecting a certain resistance in parallel to the photoconductive element in the electric shutter circuit A, the exposure time during flash photography is obtained.

As is well known, the electric shutter circuit A obtains field light conversion information through a shutter speed adjustment value circuit consisting of a photoconductive element 1 and a capacitor 2, and uses this information to control an electromagnet 3 that controls shutter closing. It is configured to operate the switching circuit 4 to control.

On the other hand, an FPS circuit switching transistor 5 and a fixed resistor 6 are connected in parallel to the photoconductive element 1, and the base of the transistor 5 is connected to a silicon-controlled rectifier 7.
(hereinafter referred to as SCR).

Therefore, when 5CR7 becomes conductive, the base potential of the transistor 5 drops, making the transistor 5 conductive, so that an individual resistor 6 is inserted in a circuit in parallel with the photoconductive element 1 and switched at the flash time.

The SCR 7 is configured to conduct by receiving a terminal voltage of a coil 10 as a control signal generating member connected to the primary coil 8a of the synchro transformer 8 via the synchro terminals a, l) and the synchro contact 9. Since the voltage generated between the terminals of the gate electrode 11 appears as a temporary pulse, only a positive pulse is supplied to the gate by the diode 11.

Next, the electronic flash circuit C is composed of a high voltage generation circuit 12, a main condenser 13, a synchro transformer 8, a discharge tube 14, etc. by known means.
A 5CR 15 is connected in series to the primary coil 8a of the main condenser 13, and the gate voltage of the SCR 15 is obtained through a neon tube 16 for displaying charge-up of the main condenser 13.

Note that 17 is a smoothing diode, and 18 is a capacitor that supplies power to the synchro transformer 8.

Therefore, in order to facilitate understanding of this invention, we will now explain the case where the SCR 15 according to this invention does not exist. In this case, the neon tube 16 is connected to the main condenser 13 in parallel.

The synchro contact 9 closes in conjunction with the shutter opening operation, and the synchro transformer 8 is supplied with power by the capacitor 18 and operates, thereby activating the discharge tube 14 and forcing it to start discharging.Meanwhile, the FPS circuit coil 10
One end P of the capacitor 18 temporarily rises in voltage due to the sudden discharge of the capacitor 18, increasing the gate voltage of the SCR 7.

Therefore, SCR 7 becomes conductive, making transistor 5 conductive and connecting fixed resistor 6 in parallel to photoconductive element 1 .

Therefore, if the resistance value of the fixed resistor 5 is set to obtain constant exposure time information such as 1/40 seconds or 1/70 seconds depending on the time constant with the capacitor 2, it will be possible to obtain constant exposure time information such as 1/40 seconds or l/70 seconds. In such a dark field state, the resistance value of the photoconductive element 1 is large and the response is slow, so the influence of the photoconductive element 1 on the time constant is ignored, and the time constant is almost equal to the resistance of the fixed resistor 6. It is determined by the value, and the exposure time is a constant value such as 1/40 second or 1/70 second.

However, if the field is bright and the change in the resistance value of the photoconductive element 1 affects the time constant, the exposure time will be shorter than the above value, resulting in proper exposure in this case as well.

Note that when the shutter is fully open, the synchro contact 9 is closed to cause the discharge tube 14- to emit light, but this timing for causing the discharge tube 14 to emit light is conventionally known and is the same as in the normal configuration. be.

The FPS circuit operates with the circuit configuration described above, but
With that circuit configuration, there is a risk that it will operate unexpectedly.

That is, if we consider a state in which the synchro cord is connected even after flash photography, the charging voltage of the capacitor 18 that remains after the discharge tube 14 is discharged is in a state where it can be supplied to the coil 10, and it is not possible to intend for flash photography. Even if the synchronization contact 90 is closed, a pulse voltage may be generated at one end of the coil 10, causing the transistor 5 to conduct, resulting in an error in the exposure time.

In addition, as explained in the above-mentioned known example, when the main capacitor 13 is still insufficiently charged and the shutter release is performed, the discharge tube 14 does not discharge, but the F
The PS circuit works, causing insufficient exposure.

Therefore, in this invention, as described above, the primary coil 8a of the synchro transformer 8 is equipped with 5C as a switching element.
In addition to connecting R15, the gate of the 5CR15 is controlled by the lighting current of the neon tube 16 for displaying charge up.

With this configuration, the synchro transformer 8 does not operate due to the residual voltage of the capacitor after the discharge tube 14 is discharged.

In other words, with this residual voltage, the neon tube 16 does not light up and the 5CR15 is non-conducting, so even if the synchro contact 9 closes with the release operation, no current flows through the coil 10. , since the FPS circuit does not operate, it does not cause an error in exposure time.

This also applies when the release operation is started when the charging pressure of the main condenser 13 is insufficient.

On the other hand, when the main capacitor 13 is sufficiently charged and the neon tube 16 lights up, the lighting current causes S
By increasing the gate voltage of CR15, 5CR1
5 is conductive.

When the synchro contact 9 is closed with the release operation, the synchro transformer 8 is operated to start discharging the discharge tube 14, while the current at one end P of the coil 10 rapidly increases due to the primary coil current of the transformer 8. .

Therefore, the transistor 5 is conductive and the fixed resistor 6 is inserted in parallel with the photoconductive element 1, so that the exposure time can be obtained in flash seconds.

Therefore, according to this invention, when the charging pressure of the main capacitor is sufficient and the indicator light lights up, if you move to the shutter release, you can take a flash photo at the correct flash time; The FPS circuit may not operate even if the shutter release is performed if the main capacitor is not yet lit and the charging pressure of the main capacitor is insufficient, or if there is residual voltage in the capacitor after discharge by the discharge tube. Therefore, there is an essential effect that there is no risk of underexposure.

Of course, such an effect can be obtained if a sync cord is connected to the camera.

In addition, in the above embodiment, for convenience of explanation, the SCR15 was explained as a switching element, but the effects of the present invention can also be obtained by inserting a switching circuit made of a switching transistor, a transistor, etc. into the primary coil of a synchro transformer. can.

[Brief explanation of drawings]

The drawing shows a specific embodiment of this invention, in which an FPS circuit is added to the electric shutter circuit A, and the synchronization cord of the electronic flash circuit C is connected to the contacts on the camera side. ing. 1... Photoconductive element, 2... Condenser, 3... Electromagnet, 4... Switching circuit, 5... Switching transistor, 6 ...Fixed resistance, 7...5CR18
... Synchro transformer, 8a ... Primary coil of synchro transformer, 9 ... Synchro contact, 10 ... Coil, 11 ... Diode, 12... High voltage generation circuit, 13...
...Main condenser, 14...Discharge tube, 1
5...5CR116...Neon tube, 1
7... Diode, 18... Condenser

Claims (1)

[Scope of utility model registration request] A synchro contact, a control signal generating member such as a coil, a synchro transformer primary coil, and a switching element or circuit are inserted into a power supply circuit whose output is the power of a capacitor charged through a resistor from the output end of the main capacitor. connected and configured to supply the lighting current of an indicator light used to indicate the completion of charging in the main capacitor as an operation signal of the switching element or circuit,
When the synchro contact is closed under a charging completion state in which the operation signal is supplied to the switching element or circuit, the synchro transformer generates a control signal in response to the current supplied to the synchro transformer flowing through the contact. A control signal generating member is used as a control signal source of an automatic flash time switching circuit, and a switching element or circuit of the switching circuit which connects a resistive member in parallel to a photoconductive element for shutter time adjustment generates the control signal. An electronic flash device equipped with a malfunction prevention function of an automatic flash time switching circuit configured to conduct a conduction operation in response to a control signal from a generating member.