JPS5971300A - Flash light discharge controller - 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 [Technical Field of the Invention] The present invention relates to a flash discharge control device in which a turn-off circuit for a switching element for controlling light emission of a flash discharge tube is improved.

[Technical background of the invention]

When taking photographs using a flash discharge tube, the amount of light reflected from the subject is detected and the flash duration is controlled to provide the camera with appropriate exposure. Various types of flash discharge control devices have been considered for this purpose. For example, the electric charge of a pre-charged main capacitor is discharged into a flash discharge tube to cause it to emit light, and the amount of light reflected from the subject is received by this emission, and when this reaches the amount of light that provides the required exposure, the flash discharge tube is Some devices control the amount of light emitted by making parallel-connected switching elements conductive and branching the discharge current. Although this system has a simple structure, it has the disadvantage that it consumes a lot of power because the switching element completely discharges the charge stored in the main capacitor.

For this reason, recently, as shown in Figure 11, a switching element (121) is provided in series with flash discharge tube No. 0, and when it is turned on, the electric charge pre-charged in the main capacitor U flows to the flash discharge tube 0D. When light is emitted and the amount of light reflected from the subject due to this light emission reaches the amount of light that provides the required exposure, the switching element (141) for commutation control is turned on and the commutation capacitor (15) is charged in advance. A device is used that controls the amount of light emitted by causing the light to flow backwards to a switching element (12) for controlling light emission and turning off the light.

[Problems with background technology]

However, in this case, in the configuration shown in Figure 1, after the commutation capacitor (1ω) is once discharged, current may not flow instantaneously as shown by the arrow in the figure.

This current charges the main capacitor (13) with the opposite polarity, so it instantly charges the flash discharge tube (
A large current flows through 11), and the amount of light emitted momentarily increases. Therefore, there is a problem in that the error in the amount of light emitted from the required exposure increases.

[Object of the Invention] An object of the present invention is to provide a high-precision flash that prevents an instantaneous increase in the amount of light emitted from the flash discharge tube when the light emission control switching element is turned off, thereby preventing the occurrence of errors in the required exposure. An object of the present invention is to provide a discharge control device.

[Summary of the invention]

A flash discharge control device according to the present invention includes a DC power supply device having two high and low positive electrodes and a common negative electrode, a main capacitor connected between the low voltage side positive electrode and the negative electrode of the DC power supply device, and a main capacitor connected between the low voltage side positive electrode and the negative electrode of the DC power supply device. A flash discharge tube having a switching element for controlling light emission connected in series to both ends of the flash discharge tube, one end connected to the high voltage side positive electrode of the DC power supply, and the other end connecting the above flash discharge tube and a switching element for controlling light emission. A commutation capacitor connected in series to the negative pole of the DC power supply, and a switching element for commutation control connected between the one end of the commutation capacitor and the negative pole side electrical path of the switching element for light emission control. This prevents an instantaneous increase in the amount of light emitted from the flash discharge tube when the switching element for light emission control is turned off.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail with reference to an embodiment shown in the drawings.

In Figure 2, (2)l is a DC power supply, which has two types of high and low positive poles and a common negative pole.In other words, this DC power supply (21J has a battery (221), whose positive pole is connected to the PNPN It is connected to the emitter of a type transistor (23).It is connected as shown to the two windings af251 (26) provided on the primary side of this transistor (2□□□ is the output transformer 04), and these two winding f251c
I! 6) are alternately excited. In addition, a capacitor t28) is connected to the secondary winding (both ends 1 of 2η) of the output transformer (24), and a series circuit of a diode (29) and a capacitor (30) is connected in parallel to this. . A current line (3
2 is the high voltage side positive electrode path. In addition, the electric line (341) led out from the upper end of the capacitor C (01) via the diode (33) is the electric line 5 for the stop bar of the low voltage (1 (U). Note that the electric line (351 is This is a co-connected negative electrode circuit (hereinafter referred to as the negative circuit).Here, the high voltage side positive electrode circuit (hereinafter referred to as the positive circuit) Gz is approximately twice that of the low voltage side positive circuit (34). A voltage is generated.

(36) is the main capacitor, and the positive circuit (34) on the low voltage side
1 and the negative current circuit. 2) is a flash discharge tube, one end is connected to the low voltage side positive tli path (34) via the beam handle (39), and the other end is connected to the negative side via the switching element (for example, SCR) for light emission control (4C). Connect to Den 2 Road.

(42 is a pulse transformer, and one end of its primary winding is connected to the positive electric circuit (34) on the low voltage side via a resistor (4).

Moreover, the other end is connected to the negative current circuit via a trigger capacitor (44). (461 is a switching element (for example, 5CR) that is turned on by a signal synchronized with the release of a camera (not shown), and its anode is connected between the resistor (431) and the primary winding of the pulse transformer (421). , the cathode is a diode (47)
and a Zener diode (connected to the negative current line (351) via mark 4, and connected to the gate of the switching element (inhibitor) for light emission control via a resistor (40).

5 is a commutation capacitor, one end of which is connected to the high voltage side positive circuit (32) through a resistor (50), and the other end connected to the negative circuit between the flash discharge tubes and the switching element (through 4α). 521 is a switching element (for example, 5CR) for commutation control, the anode of which is connected to the upper end of the flash discharge tube (38) via the capacitor 5V, and the cathode of the switching element for light emission control. (Connected to the cathode of 4G to form a commutation circuit. Also, this switching element (gate 52) is an off switch (not shown) that receives the amount of light reflected from the subject and produces an output when the amount of light that provides the required exposure. Connect with control circuit.

In the above configuration, it is assumed that both the Imao capacitor (36) and the trigger capacitor (4) have been fully charged.In this state, when the switching element (46) is turned on in synchronization with the camera release, the trigger capacitor (44) was charged with the primary winding of the pulse transformer (421) and the switching element (461).

The discharge occurs in the path of the diode (4η) and the Zener diode (48).Therefore, a trigger pulse is generated in the secondary winding of the pulse transformer (43), triggering the flash discharge g. When turned on, a voltage is also applied to the gate of the switching element (41) for light emission control via the resistor (49), turning on the switching element (40). Reactor (
39, between the flash discharge tubes, the switching element (flows through 401 and causes light to flow between the flash discharge tubes. Also, at this time, the commutation capacitor 51) is connected from the positive current line C13 on the high voltage side to the capacitor 51), between the flash discharge tubes, Switching element (
It is charged via the 4α route. Here, the voltage of the positive electric circuit (32) on the high voltage side is about 2 compared to the positive electric circuit (2) on the low voltage side.
Since the value is doubled, the capacitor 511 is charged instantly.

Next, when the above amount of light emission reaches the amount of light emission that provides the required exposure,
This is detected by reflection from the object, and an off control circuit (not shown) applies a signal to the gate of the commutation control switching element (52) to turn it on.
The charge charged in the commutation capacitor 6υ flows forward through the switching element 521, and then flows back to the switching element (4G) for light emission control, turning it off.Therefore, the flash discharge tube C'181 is turned off. , this means that the light emission amount is controlled to the correct amount.

In this case, even if a part of the discharge current of the commutation capacitor 6υ flows to charge the main capacitor (G) with the opposite polarity as in the conventional case, since the flash discharge tube (381 is out of this current path) , it is not affected by the instantaneous increase in the amount of light emitted.Also, in reality, the main capacitor (■) is connected in series with the reactor (391), so the current as described above flows. There are almost no such things.

In the figure, 541 is an indicator light, which is connected to both ends of the indicator light via a resistor (551) and a Zener diode (56) so that it lights up when the charging voltage of the main capacitor (36I) exceeds a predetermined value.

Figure 8 shows another embodiment of the invention. Note that the same reference numerals are given to the parts corresponding to those in Figure 2, and the explanation thereof will be omitted.

The difference from the embodiment shown in Figure 2 is that a contact (581) is provided that turns on in synchronization with the camera release operation, thereby discharging the pre-charged capacitor (591) and switching the gate of the switching element (46) to the correct position. I try to bias it and turn it on.

When the switching Takako (46) is turned on, the trigger capacitor (44J) charged in advance is discharged, and the flash discharge tube (38J) is connected via the pulse transformer (42).
) is triggered in the same way as in the previous embodiment. In addition, in this embodiment, a switching element (4
A is provided between the reactor circuit and the flash discharge tube circuit.

The gate is connected to the high voltage side positive electric circuit (321
A resistor (60) and a capacitor (6υ) are connected between the electrode and the cathode, and a resistor (621) is connected between the cathode and the cathode.

In this case, with the trigger of the flash discharge tube (381),
The above switching element (4α is also turned on, and the charge charged in the main capacitor (blade) is passed to the flash discharge tube μs 1,
, make it emit light. Note that, at this time, the commutation capacitor 5η is charged as in the previous embodiment.

In addition, when turning off the flash discharge lamp in order to control the amount of light emitted, the switching element 521 for commutation control is turned on as in the previous embodiment, and the electric charge charged in the commutation capacitor 6υ is used for light emission control. The switching element turns the current back and turns it off.

In this case, even if a part of the discharge current from the commutation capacitor 6υ flows to charge the main capacitor (G) with the opposite polarity, it will deviate from this current path during the flash discharge lamp, and the light will emit light. There is no adverse effect such as an instantaneous increase in the amount.

〔Effect of the invention〕

As described above, according to the present invention, when turning off the light emission control switching element connected in series with the flash discharge tube, the amount of light from the flash discharge tube does not increase instantaneously as in the conventional case. It is possible to provide an appropriate amount of light emission for the required exposure, and the practical effect is significant.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an example of a conventional device. Figure t2 is a circuit diagram showing one embodiment of the flash discharge control device according to the present invention, and Figure 3 is a circuit diagram showing another embodiment of the present invention.

Claims (1)

[Claims] (1) A DC power supply device having two types of high and low positive electrodes and a common negative electrode, a main capacitor connected between the positive and negative electrodes on the low voltage side of this DC power supply device, and a light emission control device connected to both ends of this main capacitor. a flash discharge tube connected in series with a switching element, one end of which is connected to the high voltage side positive electrode of the DC power supply, and the other end connected to a DC power supply with the flash discharge tube and a switching element for light emission control connected in series. A commutation capacitor connected to the negative pole of the device, and a switch jig element for commutation control connected between the one end of the commutation capacitor and the negative pole side electrical path of the switching element for light emission control. A flash discharge control device characterized by: