JPH0299933A - Method for charging strobe of camera - Google Patents

Abstract

PURPOSE:To obtain a satisfactory charging condition within a desired period of time even if a main capacitor inferior in accuracy is used by recharging a main capacitor with the prescribed number of times at prescribed intervals after the completion of charging the main capacitor. CONSTITUTION:The main capacitor 10 for emitting the light of a flash tube 9 is charged, and recharged with the prescribed number of times at the prescribed intervals after the completion of charging. For example, if the prescribed intervals is one minute and the prescribed number of times is four, a first recharging is performed when one minute elapses after charging is completed, a second recharging is performed when one minute elapses after the first recharging is completed, and this is repeated four times. Thus, satisfactory charging condition can be obtained within the desired period of time even if the voltage of the main capacitor 10 in about one minute after the completion of charging is not higher than the voltage at which the light of the flash tube 9 is emitted.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a camera flash charging method.

[Description of Prior Art] In the conventional strobe charging method, the main capacitor for flash tube emission is charged by boosting the DC voltage, and after the charging is completed, the main capacitor maintains a voltage that allows the flash tube to emit light. During this time, a charging OK state is given and the shack release is permitted. That is, in the conventional method, the period of the charging OK state is determined only according to the discharge characteristics of the main capacitor. Whether charging is OK can be determined by detecting whether the voltage of the main capacitor is higher than the predetermined value that allows the flash tube to emit light, or if the voltage of the main capacitor is higher than the predetermined value after the completion of charging the main capacitor. This is done based on recognition of whether or not the voltage is within a predetermined period of time, and the shirt release is prohibited when the voltage drops below a predetermined value or when a predetermined period of time has elapsed after charging is completed.

[Problems to be Solved by the Invention] According to the above-mentioned prior art, the period of the charging OK state depends only on the discharging characteristics of the main capacitor, so the longer the period of the charging OK state is attempted, the longer the period of the charging OK state becomes. This not only requires the use of a high-precision main capacitor with low voltage drop, but also poses problems such as high cost.

The present invention has been made based on the above-mentioned viewpoints, and an object of the present invention is to provide a camera strobe charging method that can obtain a charging OK state for a desired period using a less accurate main capacitor and is extremely effective in reducing costs. It is about providing.

[Means for Solving the Problems] In the present invention, the main capacitor for flash tube light emission is charged, and charging is completed so that the flash tube can emit light.
In the camera strobe charging method, the main capacitor is recharged a predetermined number of times at predetermined time intervals after the charging is completed, and the camera strobe is brought into a charging OK state for a desired period after the charging is completed. The above objectives are achieved by the charging method.

[Operation] According to the present invention, after the completion of charging the main capacitor, the main capacitor is recharged a predetermined number of times at predetermined time intervals. For example, if the predetermined time interval is 1 minute and the predetermined number of times is 4 times, the first recharging will be performed 1 minute after the completion of charging, and the first recharging will be performed 1 minute after the completion of the first recharging. Recharge the battery for the second time, and repeat up to 4 times.

Therefore, even if the voltage of the main capacitor drops below the voltage at which the flash tube can emit light within one minute after completion of charging, a charging OK state can be obtained for the desired period.

[Embodiment of the Invention] FIG. 1 is a diagram for explaining an embodiment of a strobe charging method according to the present invention.

As is well known, a camera flash device includes an oscillating booster circuit and a rectifier that boosts a DC power source to supply high-voltage DC power, and a main capacitor that is charged by the high-voltage DC power source from the oscillating booster circuit and rectifier. It has a flash tube inserted in parallel to the main capacitor and a trigger circuit for triggering the flash tube.When the main capacitor is in a charging state where the flash tube can emit light, the flash tube is activated by discharging the main capacitor. It is designed to be driven to emit light. The main capacitor is charged in the manner shown in FIG.

In Figure 1, the vertical axis is voltage and the horizontal axis is time.

The solid curve (A) represents the voltage change of the main capacitor. First, the oscillation booster circuit is driven to start charging the main capacitor, and the main capacitor reaches the charging completion voltage V. to charge. The main capacitor reaches the charging completion voltage V.

At charging completion time t, the driving of the oscillation booster circuit is stopped to provide a charging OK state in which the flash tube can emit light. Thereafter, at time t2, one minute after charging completion time t1, the oscillation booster circuit is driven again to start the first recharging. The voltage of the main capacitor decreases due to natural discharge within 1 minute after charging is completed, but the minimum voltage V at which the flash tube can emit light
It shall not be less than L. In the first recharging, the main capacitor is charged again to the charge completion voltage V0, and the charge completion voltage V. At the time t3 when the first recharging is completed, the driving of the oscillation booster circuit is stopped. Thereafter, at time t4, which is 61 minutes after the first recharging completion time t3, the oscillation booster circuit is driven again to start the second recharging. Similarly,
The third recharge is performed at time t6, one minute after the second recharge completion time t5, and the third recharge is completed at time t7.
At time t8, one minute has elapsed since then, the fourth recharging is performed. Then, the charging OK state ends at time t1°, one minute after the fourth recharging completion time t9.

The characteristic (B) indicated by the dashed-dot line in FIG.
, is the discharge characteristic of the main capacitor conventionally used to provide a charging OK condition from time t+o to time t+o.

In the present invention, a charging OK state can be obtained for a desired period without using a high-precision main capacitor that minimizes voltage drop over a long period of time as shown in characteristic (B).

FIGS. 2 and 3 show a configuration diagram and a flowchart when the strobe charging method explained in FIG. 1 is implemented using a microcomputer.

In FIG. 2, l is a microcomputer, and 2 is a strobe circuit controlled by the microcomputer l. The strobe circuit 2 includes an oscillation control transistor 31
Oscillation boost circuit 4. Transistor for overcharge earth prevention 5. Rectifier diode 6, charging completion detection circuit 7. Trigger circuit 8. It has a flash tube 9 and a main capacitor IO.

The oscillation control transistor 3 has an emitter connected to the power supply line 1.
1, and the base is connected to the first
The collector is connected to the second control terminal of the microcomputer 1 through a resistor 3a, and is turned on/off by level control of the control terminals a and b of the microcomputer 1. ing. The oscillation transistor 4a of the oscillation booster circuit 4 has a base connected to the collector of the oscillation control transistor 3 and one end of the secondary coil of the booster transformer 4b, an emitter connected to the power supply line 11, and a collector connected to the primary coil of the booster transformer 4b. Grounded via the coil. One end of the secondary coil of the step-up transformer 4b to which the base of the oscillation transistor 4a is connected is connected to the power supply line 11 via the emitter-collector circuit of the overcharge prevention transistor 5, and the other end is inserted into the power supply line 11. It is connected to the power supply line 11 via a capacitor 12 . Oscillation transistor 4
A resistor 4c and a capacitor 4d are inserted in parallel between the base of a and the power supply line 11. Such an oscillation booster circuit 4 is driven when the oscillation control transistor 3 is off, and when it is on, the base and emitter of the transistor 4a are shorted and is not driven.

The rectifier diode 6 is inserted into the power supply line 11,
A charge completion detection circuit 7 which rectifies the output of the oscillation booster circuit 4.
Trigger circuit 8. It is designed to supply a flash tube 9 and a main condenser 10.

In the charging completion detection circuit 7, a series connection of a Zener diode 7a, a diode 7b, a resistor 7c, and a resistor 7d is inserted between the power supply line 11 and the ground. The Zener diode 7a is in an off state before the charging of the main capacitor 10 is completed, and turns on when the charging of the main capacitor 10 is completed. Detection transistor 7 of charging completion detection circuit 7
The base of e is connected between the resistors 7c and 7d, the emitter is grounded, and the collector is connected to the charge completion signal input terminal C of the microcomputer 1. When the Zener diode 7a is off, the micro Terminal C of the computer 1 becomes a level, and the Zener diode 7a turns on, turning it on and giving an L level charging completion signal to the terminal C of the microcomputer 1. The charge completion detection circuit 7 is further connected to the base of the above-mentioned overcharge prevention transistor 5 via a resistor 5a between a Zener diode 7a and a diode 7b. The overcharge prevention transistor 5 is turned on when the oscillation booster circuit 4 does not stop and continues to charge the main capacitor → j-10 even after the charging of the main capacitor 10 is completed, and the oscillation booster circuit 4 is turned on. The base of the oscillation transistor 4a
The oscillation booster circuit 4 is stopped by shorting between the emitters. The overcharge prevention transistor 5 is connected to the charge completion detection circuit 7
Since the threshold level is higher than that of the detection transistor 7e, the detection transistor 7e is inverted to the on state.
later than. In the trigger circuit 8, a series connection of a resistor 8a and a trigger capacitor 8b is inserted between the power supply line 11 and the ground. The trigger transformer 8c of the trigger circuit 8 has one end of the secondary coil connected between the resistor 8a and the 1~Rigacondenser 4J-8b, one end of the secondary coil connected to the trigger electrode 9a of the flash tube 9, and the secondary coil connected to the trigger electrode 9a of the flash tube 9. The other ends of the coil and the other end of the coil are both grounded via a silicon risk 8d. The gate of the thyristor 8d is connected to the trigger output terminal d of the microcomputer 1 via a resistor 8e and a diode 8f, so that the thyristor 8d is turned on by a trigger signal from the microcomputer 1. A capacitor 8g and a resistor 8h are inserted in parallel between the gate of the SIRISK 8d and the ground. Such a trigger circuit 8 triggers the flash tube 9 by the high voltage induced in the trigger transformer by the discharge of the trigger capacitor 8b when the cyrisk 8d is turned on. A flash tube 9 and a main capacitor 10 are inserted in parallel between a power supply line 11 and ground. The microcomputer 1 charges the main controller 10 according to the flow chart shown in FIG.

In FIG. 3, first, in step 20, the oscillation control transistor 3 is turned off and the oscillation booster circuit 4 is driven. As a result, the main capacitor lO is charged. Next, in step 21, it is determined whether or not charging of the main capacitor IO has been completed, and if it has not been completed, the process waits for the charging to be completed. When charging is completed, the Zener diode 7a is turned on, the detection transistor 7e is turned on, and an L level charging completion signal is given to the microcomputer 1. Step 22 is entered by recognizing the input of the charging completion signal,
The oscillation control transistor 3 is turned on to stop the oscillation booster circuit 4, and in the next step 23, a strobe flag is set to indicate that the flash tube 9 is in a charging OK state where it can emit light, and then the process proceeds to step 24. enter. Wait until one minute has passed after charging is completed in step 24, then enter step 25, turn off the oscillation control transistor 3, drive the oscillation booster circuit 4 again, and perform the first recharging. After that, in step 26, the number of times N is set to 1, and then step 27 is entered, and recharging is repeated 4 times until the number of times N becomes 4. When the fourth recharging is performed and the number of times N becomes 4, step 28 waits for the completion of charging, step 29 waits for 1 minute after completion of the fourth recharging, and then step 3
0 and resets the strobe flag to indicate the end of the charging OK state.

In the embodiment described above, recharging was performed four times at one-minute intervals, but it is of course not limited to this.
It can be arbitrarily selected depending on the period of the state.

[Effects of the Invention] As explained above, according to the present invention, the main capacitor is recharged a predetermined number of times at predetermined time intervals after the completion of charging of the main capacitor, thereby providing a charging OK state for a desired period. It is possible to obtain a charging OK state for a desired period using a main capacitor with poor accuracy, and it is possible to provide a camera strobe charging method that is extremely effective in reducing costs.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining an embodiment of the strobe charging method according to the present invention, and FIGS. 2 and 3 are block diagrams in which the strobe charging method explained in FIG. 1 is realized using a microcomputer. and a flowchart.

Claims (1)

[Claims] 1) In a camera strobe charging method that charges a main capacitor for flash tube emission and provides a charging OK state in which the flash tube can emit light upon completion of charging, the main capacitor is charged a predetermined number of times at predetermined time intervals after the completion of charging. A camera strobe charging method for recharging a capacitor and bringing the main capacitor into a charging OK state for a desired period of time after the charging is completed.