JPH0529094B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an automatic flash device equipped with a thyristor that switches an energy supply loop to a flash discharge tube during the course of light emission from the flash discharge tube, and particularly relates to an operation control circuit for the thyristor. The present invention relates to an automatic light control flash device having the following characteristics.

BACKGROUND TECHNOLOGY Conventionally, an automatic light control strobe device that controls, for example, luminance brightness by switching the energy supply loop to a flash discharge tube during the course of light emission has been disclosed, for example, in Japanese Patent Laid-Open No. 61-69048 and Japanese Patent Application Laid-Open No. 69048. Showa 56
It is known from the publication No.-142516.

The strobe device disclosed in the former publication is
As shown in the electrical circuit diagram in the figure, the discharge loop for the flash discharge tube T of the first and second capacitors C ₁ and C ₂ charged by the power source E is connected to the thyristor 1.
The above capacitor C ₁ ,
The purpose is to control the light emission state based on the difference in C ₂ capacitance.

Briefly describing the operation, when the synchro switch S is closed, the timer circuit 2 operates and supplies an output signal to the trigger circuit 3 and delay circuit 4.

The trigger circuit 3 is operated by the above output signal,
In order to excite the main switch element SCR ₁ and the flash discharge tube T, the charged charge of the capacitor C ₁ is first transferred to the flash discharge tube T from the diode D ₁ , the inductor L ₁ and the parallel body 5 of the inductor L ₂ and the diode D ₂ . The flash discharge tube T emits light.

While the flash discharge tube T is in the process of emitting light, the delay circuit 4 operates, that is, after receiving the output signal from the timer circuit 2, it operates after a predetermined time period taking into consideration the light emission characteristics of the flash discharge tube T, and turns on the thyristor 6.

When thyristor 6 is turned on, the charge in gate capacitor _C3 that has been charged by power supply E is discharged through the pulse transformer T _P provided at the gate of thyristor 1, and therefore thyristor 1 is turned on. become.

When thyristor 1 turns on, the capacitor
The charge of _C2 is discharged to the flash discharge tube T in a discharge loop via the parallel body 5.

Therefore, by setting the capacitances of capacitors C ₁ and C ₂ such that C ₁ <C ₂ , the luminous characteristics of a flash discharge tube as shown in Figure 3 can be obtained, making it possible to photograph objects at close range. The automatic light control operation by receiving the reflected light, that is, the light amount control operation by the well-known operation of the light amount control circuit 7 including the sensor P shown in the figure can be expected to be effective in performing the light amount control operation with high precision.

The latter strobe device also has a thyristor 8 that switches the discharge loop of the flash discharge tube T while it is in the process of emitting light, as shown in a schematic electrical circuit diagram in FIG. In FIG. 4, the same numbers and symbols as those in FIG. 2 indicate the same functional members.

Briefly describing its operation, when the synchro switch is closed, the trigger circuit 3 operates and at the same time, the delay circuit 4 also starts operating in conjunction.

The flash discharge tube T is excited by the operation of the trigger circuit 3, and the thyristor 9 is also turned on, and the charge in the main capacitor C _H charged by the power supply E is discharged in the discharge loop of the flash discharge tube T, the resistor 10, and the thyristor 9. Therefore, the flash discharge tube T
will emit light.

When the delay circuit 4 operates during the light emission process as described above, the thyristor 8 turns on.

When thyristor 8 turns on, the previous resistance 1
0, main capacitor C _H via thyristor 9
The discharge loop of the charged charge will be switched to the thyristor 8. At this time, the flash discharge tube T becomes a discharge loop that does not include any resistance, so the amount of light increases, and as a result, the light emission characteristics shown in Figure 3 are obtained as in the previous example. Become.

Problems to be Solved by the Invention As mentioned above, various thyristors are known for switching the discharge loop of a flash discharge tube during the process of light emission, but the former type has the following disadvantages, for example. There is a possibility that this may occur.

In other words, since a pulse transformer T _P is used, an oscillating voltage is applied to the gate of thyristor 1. Therefore, when a negative oscillating voltage is generated in the pulse transformer T _P , thyristor 1 cannot be turned on. Otherwise, the on operation will be delayed until the next positive oscillating voltage occurs, and in some cases, the capacitor may be turned on by the next positive oscillating voltage.
There is a possibility that the discharge of C ₁ has ended, in which case the flash discharge tube T has extinguished and the capacitor
This results in the inconvenience that the light emission operation using C ₂ cannot be performed.

In addition, since a pulse transformer T _P is used, a charging resistor R and a gate capacitor are installed on the primary side.
A circuit consisting of C ₃ and thyristor 6 is required,
On the other hand, the resistance value of the charging resistor R cannot be lowered sufficiently due to the holding current of the thyristor 6, and as a result, during short-term repeated light emission, the gate capacitor _C3 is insufficiently charged, and the gate operation of the thyristor 1 is delayed. There is also the risk that the process cannot be carried out reliably.

In addition, in the latter case, the thyristor 8 for switching the discharge loop is provided on the low voltage side, and its gate means does not use the pulse transformer T as in the former case, but instead uses a general pulse circuit as described above. Although such inconvenience does not occur, in order to obtain the waveform shown in Figure 3, which is the purpose of switching the discharge loops, a resistor is connected to one discharge loop, and in terms of effective energy use, it is better than the former. It has some disadvantages.

Furthermore, when considering automatic dimming operation by the light amount control circuit 7 including the sensor P, both thyristors 8 and 9 are commutated, so
Thyristors with good commutation characteristics must be used as the thyristors 8 and 9, which has the disadvantage of increasing costs.

The present invention has been made in consideration of the above points, and allows the use of an inexpensive thyristor that is not affected by commutation characteristics for switching the discharge loop, and also enables continuous light emission without using a pulse transformer. Another object of the present invention is to provide a strobe device equipped with an operation control circuit that causes the thyristor to perform stable on/off operations.

Means for Solving the Problems The automatic light control strobe device according to the present invention includes a flash discharge tube that has a plurality of discharge light emission loops and emits light by receiving energy supply from a light emitting capacitor, and a flash discharge tube that is connected in series with the flash discharge tube. a main switch element,
a light amount control circuit that controls the operation of the main switch element based on the amount of reflected light received from the subject; and a thyristor that is connected in series with the flash discharge tube and selectively forms one of the plurality of discharge loops when turned on. An automatic light control flash device comprising: a low impedance element connected between the gate and cathode of the thyristor; a gate capacitor connected between the gate and the low potential side of the main switch element; and the low impedance element connected between the gate and the cathode of the thyristor. A series body with a resistor having an impedance higher than the impedance of the element, a bidirectional switch element connected to both ends of the resistor, and the flash light so that the connection point between the gate capacitor and the gate has a high potential. The thyristor comprises a charging means for charging the discharge tube before it emits light, and a control circuit that is connected to the control pole of the bidirectional switch element and outputs a control signal that turns on the switch element while the flash discharge tube is in the process of emitting light. It is configured with an operation control circuit.

Function Since the automatic light control strobe device according to the present invention has the above-described configuration, when the flash discharge tube emits light in a discharge loop that does not include a thyristor, the charge in the gate capacitor is transferred to the low impedance element and the flash discharge tube. The discharge occurs in a discharge loop consisting of a tube, a main switch element, and a resistor.

However, since the impedance of the resistor, that is, the resistance value, is higher than the impedance of the low impedance element, the voltage drop generated in the low impedance element becomes extremely low due to the division ratio, and the thyristor does not turn on.

On the other hand, when the bidirectional switch element is turned on by the operation of the above-mentioned operating control circuit, the charge in the gate capacitor is transferred to the low-impedance element,
The discharge will occur in a different discharge loop from the above, consisting of a flash discharge tube, a main switch element, and a bidirectional switch element.

At this time, the voltage drop occurring in the low impedance element is naturally higher than in the previous case because the resistance is short-circuited by the bidirectional switch element and the discharge impedance decreases, so the thyristor becomes stable. By supplying the dropped voltage, which is a direct current voltage, to the gate, it is ensured that the gate is turned on.

Embodiment FIG. 1 is an electric circuit diagram showing an embodiment of an automatic light control flash device according to the present invention. In the figure, the same figure numbers and symbols as in FIG. 2 indicate the same functional members.

As is clear from the drawings, this embodiment connects the two discharge loops of the flash discharge tube T with capacitors C ₁ and
This is a type formed by switching _C2 .

A resistor 11 having a relatively low resistance value, which is a low impedance element and serves as a gate means for the thyristor 1, is connected between the gate and cathode of the thyristor 1 in FIG. It is connected via a series body 12 consisting of a triax 14, which is a directional switch element, to an earth line, that is, to the cathode of the main switch element _SCR1 forming a series body with the flash discharge tube T.

A resistor 15 having a high resistance value is connected to both ends of the triax 14.
A control circuit 16 is connected to the gate 4, which operates at a predetermined time after the flash discharge tube T starts emitting light and outputs a control signal to turn on the triac 14.

Further, one end of the gate capacitor 13 is connected to a power source E via a resistor 11 and diodes D ₅ , D ₁ , and D ₃ .

The diodes _D3 and _D4 are well-known rectifying diodes that are also used in the conventional device shown in FIG.

The operation of the embodiment configured as described above will be described below.

When a predetermined voltage is output from power supply E, capacitor C ₁ is connected to capacitor C ₂ via diode D ₃ .
is connected through the diode _D4 , and the gate capacitor 13 is connected to the diodes _D3 , _D1 , _D5 and the resistor 11,
It will be charged via 15. That is, in this embodiment, the resistors 11 and 15 also function as charging means for the gate capacitor 13.

When the trigger circuit 3 operates with the above charging completed, the flash discharge tube T is excited, and this change in the state of the flash discharge tube T causes the main switch element to be activated.
A gate signal is supplied to SCR ₁ , and flash discharge tube T first consumes the charge in capacitor C ₁ to emit light.

At the same time, the charge in the gate capacitor 13 is also discharged in the first discharge loop consisting of the resistor 11, inductor _L3 , flash discharge tube T, main switch element _SCR1 , and resistor 15.

Therefore, the resistor 11 is connected to the gate of the thyristor 1.
The voltage drop generated across the resistor 11 and the resistor 15 is applied in the forward direction, but the respective resistance values R ₁₁ ,
If the relationship of R ₁₅ is set so that R ₁₁ << R ₁₅ , the voltage drop generated across the resistor 11 will be at an extremely low level, and the thyristor 1 can be controlled to a voltage value that cannot be turned on. As mentioned above, in the present invention, the resistor 11 is set to a low resistance value, and the resistor 15 is set to a high resistance value, so that the first discharge through the resistor 15 of the gate capacitor 13, that is, the first discharge During discharging in the loop, thyristor 1 is prevented from turning on.

On the other hand, the above-mentioned capacitor is connected to the control circuit 16 which starts operating in conjunction with the operation of the trigger circuit 3.
When a control signal is output at a predetermined point in time during the flash discharge tube T's light emission due to the charged charge of _C1 , the triac 14 is turned on.

When the triax 14 is turned on, the first discharge loop of the gate capacitor 13 that has been formed until then is discharged from the triax 14 without passing through the resistor 15.
into the discharge loop via: resistor 11, inductor L ₃ , flash discharge tube T, main switch element SCR ₁ ,
A switch is then made to the second discharge loop consisting of the triax 14.

Therefore, the discharge impedance of the gate capacitor 13 is greatly reduced, and the voltage drop generated across the resistor 11 becomes high.

It goes without saying that the drop voltage value at this time can be set to a high level that can turn on the thyristor 1, which is of course done in the present invention. It will turn on.

When the thyristor 1 is turned on, the charge in the capacitor _C2 is discharged to the flash discharge tube T via the thyristor 1, inductor _L3 , etc.
In other words, the discharge light emission loop is switched,
The flash discharge tube T discharges and emits light based on the charge on the capacitor _C2 , in continuation of the previous discharge and emit light based on the charge on the capacitor _C1 .

When the reflected light from the subject reaches a predetermined amount during the discharge light emission operation as described above, the light amount control circuit 7 including the sensor P that receives the reflected light operates, and the main switch element SCR ₁ In order to turn off the flash discharge tube T, the light emission of the flash discharge tube T is stopped.

When the flash discharge tube T stops emitting light, the gate capacitor 13 includes the capacitor C ₁ , the diode D ₁ ,
It is rapidly charged in a loop consisting of D ₅ , resistor 11, and triax 14, and is ready for the next operation.

On the other hand, since the gate and cathode of the thyristor 1 are reverse biased while the gate capacitor 13 is being charged, it goes without saying that the thyristor 1 is turned off at an appropriate time.

By setting the end point of the output of the control signal output by the control means 16 after the end of the manual light emitting operation of the flash discharge tube T, the triax 14 contributes to the above-described rapid charging operation of the gate capacitor 13. However, it may be done before the above-mentioned end point. However, in this case, charging of the gate capacitor 13 is also performed via the resistor 15.

Effects of the Invention The automatic light control strobe device according to the present invention charges the gate capacitor charged prior to light emission in response to the ON operation of the bidirectional switch element.
In addition, switching discharge is performed in the first and second discharge loops having different discharge impedances formed through the flash discharge tube, and the voltage drop difference generated in the common portion of the two discharge loops obtained by such discharge operation is utilized. Since the operation of the thyristor that switches the energy supply loop to the flash discharge tube is controlled, a stable DC voltage can be reliably supplied to the gate of the thyristor at the desired time of switching the discharge loop.

Furthermore, the above effect makes it easy to use the thyristor on the high pressure side, and therefore an inexpensive thyristor that does not require particular consideration of commutation characteristics can be used as the switching thyristor.

In addition, by continuing to turn on the bidirectional switch element, the charging time constant of the recharging loop of the gate capacitor can be reduced, ensuring that the switching thyristor is turned on even when repeated light emission operations are performed. You can also expect some positive effects.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing an embodiment of an automatic light control strobe device according to the present invention, FIG. 2 is an electric circuit diagram showing an example of a conventional device, and FIG. 3 is an electric circuit diagram showing an example of a conventional device. FIG. 4 is an electric circuit diagram showing another example of a conventional device. 1... Thyristor, 3... Trigger circuit, 7...
...Light amount control circuit, 11...Resistor, 12...Series body, 13...Gate capacitor, 14...Triack, 15...Resistor, 16...Control circuit,
SCR ₁ ...Main switch element, T...Flash discharge tube,
_D1 to _D5 ...Diode, _L3 ...Inductor, _C1 ,
C ₂ ... Capacitor.

[Claims]

1. A card-type camera characterized by having the following requirements. (b) Formed into a convex shape by a base formed thin and a thin lens part provided at the upper part of the center, and the thin side part is detachably attached to one side of the lens part. The entire body is formed into a card shape by rotatably connecting the viewfinder part to the lens part on the other side. ,
A mounting portion for a film magazine having a film storage portion at one end and a film winding portion at the other end is formed. The film winding section shall be located on the shoulder of the camera.

Claims (1)

2. The automatic light control strobe device according to claim 1, wherein the supply of the control signal to the flash discharge tube is stopped after the maximum light emission period of the flash discharge tube. 3. The automatic light control flash device according to claim 1, wherein the low impedance element is a resistor having a low resistance value.