JPH07122389A - Stroboscopic circuit - Google Patents

Abstract

PURPOSE:To carry out charging up to a specific voltage and shorten the charg ing time by one time pressing operation of a stroboscope charging switch. CONSTITUTION:A stroboscope charging switch 6 is turned on once and immediately after that, it is turned off. An oscillation transistor 16 starts oscillation by an oscillation transformer 13 and amplifies current from a primary winding 13a. The oscillation transistor is saturated, feedback current from a secondary winding 13c is gone, and current in primary side lowers. Since bias voltage is applied to the oscillation transistor, the transistor is not turned to be in complete off. Primary side current starts flowing again and oscillation is continued. When secondary side current is rectified and a main capacitor 21 is charged up to the specified voltage, current flows in a Zener diode 30 and an oscillation stopping transistor 40 is turned on and no bias voltage is applied to the oscillation transistor, so that the oscillation transistor is turned completely off and a control transistor is also turned off and the oscillation is interrupted and the charging of the main capacitor 21 is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a strobe circuit,
More specifically, the present invention relates to a strobe circuit that charges a main capacitor to a specified voltage even if a strobe charging switch is turned on and then turned off.

[0002]

2. Description of the Related Art In the case of photographing a subject having a short exposure amount, if a strobe is fired, a good print photograph can be obtained. Some low-priced cameras, such as large-sized cameras such as lens-fitted film units, have a built-in strobe device.
Since it is necessary to charge the main capacitor to a specified voltage in advance when performing flash photography, the strobe charging switch is normally turned on prior to flash photography.

The strobe charging switch includes a push operation type and a slide operation type. In the push operation type, while the user is pressing the movable piece, the strobe charging switch 6 of the charging circuit shown in FIG. 6 is turned on to oscillate the transistor 16 and the oscillation transformer 13.
The main capacitor 21 is charged via the, and the charging is stopped by releasing the pressing of the movable piece. Therefore, it is possible to prevent wasteful consumption of the battery without leaving the strobe charging switch 6 turned on, but it is necessary to keep pressing the movable piece until the charging is completed. Further, in this case, since the pressing of the movable piece is released after confirming the start of the discharge of the neon tube, the charging voltage to the main capacitor is not constant, and the light emission amount of the strobe may vary.

In order to improve the operability of the push-type strobe charging switch and the amount of strobe light emission, charging is performed until the voltage reaches the specified voltage even if the strobe charging switch is released from the specified voltage, for example. Kaihei 3-65
The strobe circuit described in No. 129 is known. In this strobe circuit, oscillation is started at the moment when the strobe charge switch is pressed, and thereafter, oscillation is continued even if the strobe charge switch is released from the push. Then, from the time when the strobe charge switch is pressed, a predetermined time required for the main capacitor to be fully charged is measured by the time constant circuit, and oscillation is automatically stopped when this predetermined time has elapsed. It has become.

[0005]

However, the above method has a problem that the charging time becomes longer than that of the circuit in which the same oscillation transformer is continuously pressed. In order to shorten this charging time, if the number of secondary windings of the oscillation transformer is increased to output a voltage higher than the withstand voltage of the main capacitor and a voltage higher than the withstand voltage is to be limited using a Zener diode, etc. However, since a high voltage is applied to the transistor and a transistor having a high breakdown voltage is required, the transistor and the transformer are increased in size, which is disadvantageous in downsizing.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a strobe circuit in which the charging time is short by one pressing operation of the charging switch.

[0007]

In order to achieve the above object, the present invention has a primary coil having one end connected to a power source and the other end connected to the collector of an oscillating transistor, and one end inductively coupled to the primary coil. Is connected to the main capacitor, a secondary coil whose other end is connected to the base of the oscillating transistor, is connected in parallel to the primary coil with respect to a power supply and is inductively coupled to the secondary coil, and one end is a power switch. To the power source and the other end to the base of the oscillating transistor, the collector of the oscillating transistor and the base to the other end of the primary coil, the emitter to the power source, the collector to the The base of the oscillation transistor or the control transistor connected to the power switch side of the tertiary coil, the base of the oscillation transistor, and A Zener diode connected in series with the in-capacitor is provided, and the collector current of each of the oscillation transistor and the control transistor is positively fed back to the other base to maintain oscillation, while the secondary coil is connected to the secondary coil. The main capacitor is charged by the flowing current, and when the main capacitor reaches a specified voltage, the oscillation transistor is reverse biased by the voltage from the Zener diode to stop the oscillation.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 2, a lens-fitted photo film unit having a built-in strobe circuit of the present invention (hereinafter referred to as a strobe photo film unit) is shown in FIG. Photographing is performed with the outer case 2 in which is stored. At the center of the front surface of the unit body 1, the taking lens 3
Are arranged. A finder 4 is provided above the taking lens 3, and a strobe light emitting section 5 is arranged on the right side of the finder 4. A strobe charge switch 6 is provided below the strobe light emitting section 5. A shutter button 7, a winding knob 8, a display window 9 for confirming the number of remaining films, and a display window 10 for confirming completion of strobe charging are provided on the upper surface of the film unit with a strobe.

FIG. 1 is a circuit diagram showing a strobe circuit. The booster 18 oscillates via the positive terminal of the battery 11 as the power supply source, the emitter terminal of the control transistor 12, the second terminal of the primary coil 13a of the oscillation transformer 13, the strobe charge switch 6 and the resistor 14. Transformer 13
Is connected to the third terminal of the tertiary coil 13b. The collector terminal of the control transistor 12 has a resistor 1
Via the third coil 13b of the oscillation transformer 13
Connected to the terminals, this tertiary coil 13b and secondary coil 1
The base terminal of the oscillation transistor 16 is connected to the fourth terminal which is a shared terminal with 3c. The base terminal of the control transistor 12 is connected to the primary coil 1 via the resistor 15.
It is connected to the first terminal of 3a and the collector terminal of the oscillation transistor 16.

The emitter terminal of the oscillating transistor 16 is connected to the negative terminal of the battery 11 and the positive side of the strobe discharge section 20. Once the strobe charging switch 6 is turned on, the oscillation transistor 16 performs oscillation because the positive feedback is applied from the oscillation transformer 13, and after the strobe charging switch 6 is turned off,
Positive feedback is applied from the collector of the control transistor 12 via the resistor 14 and the tertiary coil 13b, and since the bias voltage is applied to the base terminal, continuous oscillation occurs.

The fifth terminal of the secondary coil 13c is connected to the cathode of the diode 17, and the anode of the diode 17 is connected to the minus side of the strobe discharge section 20. During the oscillating operation of the oscillating transistor 16, a high voltage corresponding to the winding ratio between the primary coil 13a and the secondary coil 13c is generated, and only the secondary side current flowing from the fifth terminal to the fourth terminal is a diode. Strobe discharge unit 20 by 17
Is powered.

The strobe discharge section 20 includes a main capacitor 21, a trigger capacitor 22, a synchro switch 23,
It comprises a trigger transformer 24, a trigger electrode 25, a strobe discharge tube 26, a neon tube 27 and the like. The current supplied from the booster 18 is supplied to the main capacitor 21 and the trigger capacitor 2
Charged to 2. The specified voltage of the main capacitor 21 is
It is 300V. The neon tube 27 is the main condenser 2
It is connected to both terminals of 1 through resistors 28 and 29.
The neon tube 27 blinks when the main capacitor 21 is charged to the specified voltage, and the photographer can confirm that the charging is completed by confirming the blinking through the display window 10. The synchro switch 23 is turned on when the shutter blades are fully opened, the trigger capacitor 22 is discharged, a current is passed through the primary side of the trigger transformer 24, and a high voltage is applied to the trigger electrode 25 connected to the secondary side. And
By applying a high voltage to the trigger electrode 25, the Xe gas in the strobe discharge tube 26 is ionized and the resistance is broken, so that the main capacitor 21 is discharged and the strobe discharge tube 26 emits light.

The negative terminal of the main capacitor 21 is connected to the anode terminal of the Zener diode 30, and the cathode terminal of the Zener diode 30 is connected to the base terminal of the oscillation stopping transistor 40 via the resistor 31. There is. The emitter terminal of the oscillation stopping transistor 40 is a shared terminal (fourth terminal) of the oscillation transformer 13.
Is connected to the base terminal of the oscillating transistor 16 and the collector terminal is connected to the negative side of the battery 11 and the positive side of the strobe discharge section 20. The Zener diode 30 has a Zener voltage of 300V, and when the main capacitor 21 is charged to a specified voltage and the voltage of the negative terminal of the main capacitor 21 becomes -300V, a Zener current is passed from the cathode terminal to the anode terminal. . When this Zener current flows, the oscillation stopping transistor 40 operates and the base current does not flow through the oscillation transistor 16. In this way, the oscillation transistor 16
Is turned off, and the control transistor 12 is turned off
As a result, the operation of the booster 18 is stopped.

Next, the operation of the above embodiment will be described. The photographer rotates the winding knob 8 of the film unit with a strobe to charge the shutter and prepares for photographing. When it is necessary to make the strobe emit light for photographing, the strobe charging switch 6 is pressed and released.

When the strobe charge switch 6 is turned on, a current flows between the base and emitter of the oscillation transistor 16 via the resistor 14 and the tertiary coil 13b. This increase in the tertiary side current causes an electromotive force in the primary coil 13a, and the primary side current in the first terminal direction starts flowing from the second terminal. This primary side current flows as a collector current of the oscillation transistor 16. Further, the increase in the primary side current causes an electromotive force to be generated in the secondary coil 13c to flow the secondary side current in the direction from the fifth terminal to the fourth terminal, so that the base current of the oscillation transistor 16 increases and the primary coil is increased. The collector current (primary side current) from 13a further increases.

In the control transistor 12, when the current flows between the collector and the emitter of the oscillation transistor 16 as described above, the base current flows. Therefore, the control transistor 12 is turned on and the emitter and collector are electrically connected. As a result, the bias voltage (V1) is applied via the resistor 14 and the tertiary coil 13b.
Is applied to the base terminal of the oscillation transistor 16.

Due to the positive feedback action with the oscillating transformer 13, the oscillation transistor 16 becomes saturated as the base current increases, and the collector current becomes a constant value. Therefore, the change (increase) in the primary side current disappears, the electromotive force does not occur in the secondary coil 13c, and the secondary side current does not flow. The oscillation transistor 16 rapidly reduces the collector current because the base current from the secondary coil 13c sharply decreases.

However, since the oscillator transistor 16 is fed back to the base terminal from the controlling transistor 12 through the resistor 14 and the tertiary coil 13b by positive feedback, the base potential is the bias voltage from the controlling transistor 12. It only drops to (V1). That is, even if the secondary side current of the oscillating transistor 16 becomes zero, the collector current from the controlling transistor 12 flows in as a base current, so that the collector-emitter of the oscillating transistor 16 is not completely turned off. . Therefore, the primary-side current starts to flow from the second terminal of the primary coil 13a toward the first terminal again, and flows in as the collector current of the oscillation transistor 16. When the primary current again increases, the base current input to the oscillation transistor 16 increases due to the positive feedback action with the oscillation transformer 13, and the primary current further increases and flows as a collector current. The oscillating transistor becomes saturated and the primary side current becomes constant. After that, the above-described operation of continuing the oscillation from the saturated state is repeated.

On the other hand, when the current flowing through the primary coil 13a changes, the secondary coil 13c generates an electromotive force,
A secondary current in the direction from the fifth terminal to the fourth terminal is supplied to the strobe discharge circuit 20 by the diode 17, and the main capacitor 21 and the trigger capacitor 22 are charged.

When the main capacitor 21 is fully charged, the negative terminal has a voltage of −300 V or more, and a Zener current flows through the Zener diode 30. This allows
In the oscillation stopping transistor 40, the base current flows so that the emitter-collector is turned on, and the base current flowing in the oscillation transistor 16 is set to almost 0. The oscillation transistor 16 cuts off the collector-emitter. As a result, the primary side current does not flow, and at the same time, the base current of the control transistor 12 becomes 0, the emitter-collector is cut off, and the bias voltage is not applied to the base terminal of the oscillation transistor 16. Since the bias voltage disappears, the oscillation transistor 16 cannot continue oscillation. In this way, the operation of the booster 18 is stopped.

When the main capacitor 21 is fully charged, the neon tube 27 blinks. The photographer presses the shutter button 7 after confirming by flashing the neon tube 27 that the preparation for strobe light emission is completed. When the shutter button 7 is pressed, the synchro switch 23 is turned on when the shutter blades are fully opened. Then, the trigger capacitor 22 is discharged and a high voltage is applied to the trigger electrode 25. When the high voltage is applied to the trigger electrode 25, the main capacitor 21 is discharged and the strobe discharge tube 26 emits light.

In the strobe circuit shown in FIG. 1, when the main capacitor 21 is charged to the specified voltage, a Zener current flows through the Zener diode 30, the oscillation stopping transistor 40 operates, and the base current flows through the oscillation transistor 16. Although the oscillation is stopped so that the current does not flow in, the oscillation transistor 1 is used as in the strobe circuit shown in FIG.
A circuit in which the oscillation stopping transistor 40 between the transistor 6 and the Zener diode 30 is omitted may be used. Also in this case,
When the main capacitor 21 is charged to the specified voltage, the Zener current flows through the Zener diode 30,
The base current of the oscillating transistor 16 stops flowing and the oscillation stops. Thus, the operation of the booster 11 can be stopped even if the number of parts is reduced. The same parts as those in FIG. 1 are designated by the same reference numerals.

In the above embodiment, the control transistor 1 is used.
A bias voltage is applied to the oscillation transistor 16 from the collector of No. 2 through the tertiary coil 13b to restart the oscillation, but as shown in FIG.
A bias voltage may be directly applied to the oscillation transistor 16 from the collector to maintain the oscillation.

Even in this case, the electric current obtained by rectifying the high-voltage alternating current can be supplied to the strobe discharge section 20. When the charging of the main capacitor 21 is completed and the specified voltage is reached, the operation of the booster 18 is stopped in the same manner as the embodiment shown in FIG. Even in the case of the circuit shown in FIG. 4, the operation of the booster 11 can be stopped even if the oscillation stopping transistor 40 is omitted as shown in FIG. 5 and the number of components is reduced. The same parts as those in FIG. 1 are designated by the same reference numerals.

The charging time by the strobe circuit shown in FIG. 1, FIG. 3, FIG. 4, and FIG. 5 described above is the same as that in the case where the conventional strobe charging switch is continuously pressed.

[0026]

As described above, according to the strobe circuit of the present invention, once the strobe charge switch is pressed, the oscillating transistor oscillates with the positive feedback current from the oscillating transformer, and the oscillating transistor is saturated. Therefore, even if the positive feedback current from the oscillating transformer disappears, the controlling transistor gives positive bias to the oscillating transistor to give a bias voltage.When the main capacitor is charged to the specified voltage, the main capacitor Voltage is detected, the transistor for oscillation is turned off, and the transistor for oscillation is turned off so that the transistor for control is turned off. Therefore, press the strobe charge switch once to release the press immediately. However, since the main capacitor is charged to the specified voltage and charging is stopped, the strobe charging switch You need to hold down the Nakuru. Also,
Charging can be performed in the same time as the conventional one that continues to be pressed, and since the charging to the main capacitor ends at the specified voltage, there is no variation in the amount of light emitted by the strobe.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a strobe circuit embodying the present invention.

FIG. 2 is an external view of a lens-fitted film unit incorporating the strobe circuit of the present invention.

FIG. 3 is a circuit diagram of a strobe circuit in which an oscillation stopping transistor is removed from the strobe circuit of FIG.

FIG. 4 is a circuit diagram of a strobe circuit in which a collector of a control transistor is connected to a base of an oscillation transistor.

5 is a circuit diagram of a strobe circuit in which an oscillation stopping transistor is removed from the strobe circuit of FIG.

FIG. 6 is a circuit diagram of a conventional strobe circuit.

[Explanation of symbols]

 6 Strobe Charge Switch 11 Battery 12 Control Transistor 16 Oscillation Transistor 13 Oscillation Transformer 21 Main Capacitor 26 Strobe Discharge Tube 30 Zener Diode 40 Oscillation Stop Transistor

Claims (1)

[Claims] 1. A primary coil having one end connected to a power source and the other end connected to the collector of an oscillation transistor, one end being inductively coupled to the primary coil, one end being a main capacitor, and the other end being a base of the oscillation transistor. A secondary coil connected to the secondary coil is connected in parallel to the primary coil to a power source and is inductively coupled to the secondary coil. One end is connected to the power source via a power switch and the other end is the base of the oscillation transistor. Connected to the third coil, the collector of the oscillation transistor and the base of the other end of the primary coil are connected, the emitter is connected to the power supply, the collector is connected to the base of the oscillation transistor or the power switch side of the tertiary coil. Control transistor, and a Zener connected in series between the base of the oscillation transistor and the main capacitor. An anode is provided, and the collector current of each of the oscillation transistor and the control transistor is positively fed back to the other base to maintain oscillation, while the main capacitor is charged by the current flowing in the secondary coil, and the main capacitor is A strobe circuit, characterized in that, when a prescribed voltage is reached, the oscillation transistor is reverse-biased with the voltage from the Zener diode to stop oscillation.