JPH023976B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power wastage prevention device for preventing wastage of a power supply battery used in a so-called flash camera having a built-in strobe device.

Generally, the operation of the strobe device in a flash camera is controlled as necessary via a mechanical switch such as a slide switch. Often, the switch is operated by mistake at the same time, resulting in a waste of battery power.

Therefore, considering the above problems,
Combining an electromagnetic magnet and a mechanical switch that is energized so that it cannot be energized all the time, the strobe device is energized by locking the mechanical switch in a predetermined state with the electromagnetic magnet, and the strobe device is energized for a predetermined period of time. Later, devices were proposed or put into practical use that cut off the power to the electromagnetic magnet and caused the mechanical switch to return to its original state.

However, although the above method is obvious when considering the configuration, it requires the use of an electromagnetic magnet etc. in a flash camera, which is desired to be more compact, resulting in a complicated structure, increased costs, and equipment This has led to various new problems, such as the increase in size, and strong improvements are still desired.

Furthermore, when considering the normal usage conditions of the above means, that is, when considering the timing of turning on the mechanical switch necessary to cause the flash discharge tube to emit light, the brightness of the subject When the flash camera user decides to input the
It is conceivable that the brightness of the object is detected electrically and when the brightness of the object falls below a predetermined value, a warning is displayed on a display element such as an LED to notify the user. In the former case, the user has to make the decision, which is cumbersome and can lead to wrong decision criteria, resulting in underexposure or overexposure, resulting in shooting failures.
In the latter case, there is a risk that even though a warning is displayed using a display element such as an LED, the user may make a visual error or forget to turn on the start switch, resulting in a failure in photographing.

The present invention has been made in consideration of the above-mentioned points, and includes an electrical switch element that can control the supply of power to the DC-DC converter circuit in a flash camera and the supply of base current of the oscillation transistor. In addition, it is controlled by a timer circuit that controls the operation of the switch element and a subject brightness detection circuit that controls the timing of operation of the timer circuit, and because it is a purely electrical control system, the configuration is simple. Moreover, it provides a means for preventing wastage of power in a flash camera which is superior in terms of space and cost compared to those using conventional electromagnetic magnets, and will be described in detail below with reference to the drawings.

The figure is an electric circuit diagram showing an embodiment of the means for preventing power wastage in a flash camera according to the present invention. A subject brightness detection circuit consisting of a switch 2, transistors 5, 6, a resistor 4, etc. 7 is a resistor 8, 9, 12, 13, a transistor 11, 1
4. Timer circuit consisting of capacitor 10, 15
18 is a trigger circuit consisting of a resistor 19, a trigger capacitor 20, a trigger transformer 21, a synchro switch 22, 23 is a flash discharge tube, and 24 is a main capacitor. , 25 is a resistor, 27 is a lock switch interlocked with, for example, a shutter release lock mechanism (not shown), and 28 is a resistor.

As for the operation of the circuit constructed as described above, when the shutter release button is pressed in order to take a picture, the switch 2 is turned on in the middle-pressed state. Therefore, the power source 26 is supplied to the subject brightness detection circuit 1 via this switch 2, and the subject brightness is measured by the light receiving sensor 3 and the like.

The operation of the object brightness detection circuit 1 is such that when the object brightness is high and the flash discharge tube 23 does not need to emit light, that is, the voltage drop across the resistor 4 is high and the transistor 5 is turned on. There are two types of operation: when the brightness is low and the flash discharge tube 23 needs to emit light, that is, when the voltage drop across the resistor 4 is low and the transistor 5 is rendered non-conductive. In other words, if we consider point A in the figure, which is the output terminal of the object brightness detection circuit, when the object brightness is sufficiently high, transistor 6 is in a non-conducting state due to the operation of transistor 5 described above, and point A is reached. There is no influence on this, and in the illustrated configuration, the potential of the capacitor 10 charged via the resistors 8 and 9 is maintained. On the other hand, when the subject brightness is low, the above-mentioned operation of the transistor 5 causes the transistor 6 to receive the base current from the power supply 26 via the switch 2 and the resistor and become conductive. , the charge in the capacitor 10 will be discharged and brought to a low level.

Now, let's consider a case where the subject brightness is low. When the brightness of the subject is low, as mentioned above, the transistor 5 does not become conductive, the transistor 6 becomes conductive, the point A becomes low level, and the charge in the capacitor 10 is discharged, so that the timer circuit 7 Current will flow through the resistors 8 and 9. When current flows through resistors 8 and 9,
Transistor 11 due to the voltage drop occurring across resistor 8.
becomes conductive, and current also flows through the resistors 12 and 13, so that the transistor 14 becomes conductive.

Needless to say, the transistor 14 becomes conductive and the base current of the oscillation transistor 16 of the DC-DC converter circuit 15 is supplied, so that the well-known operation is performed in the DC-DC converter circuit 15.
starts. When the DC-DC converter circuit 15 starts operating, the main capacitor 24 and the trigger capacitor 20 are charged, and the flash discharge tube 23 is prepared to emit light.

Now, let us consider the operation of the DC-DC converter circuit 15 described above. As is clear from the above operation, if the flash camera user presses the shutter release button halfway and the subject brightness is low, the DC-DC converter circuit 15 is automatically activated.
starts its operation, but it is clear from the figure that this operation stops when the supply of base current to the oscillation transistor 16 ceases. That is, if the transistor 14 becomes non-conductive,
The operation of the DC-DC converter circuit 15 is therefore stopped.

On the other hand, the transistor 14 constitutes a part of the timer circuit 7, and as is clear from the above description, its operation is controlled by the operation of the transistor 11, and when the transistor 11 becomes non-conductive, it becomes non-conductive. Becomes conductive.

That is, in the present invention, the transistor 11
The operation of the circuit is controlled by a timekeeping configuration consisting of resistors 8 and 9 and a capacitor 10, and the consumption of power supply energy by the oscillation transistor 16, that is, the DC-DC converter circuit 15 is controlled.

In other words, if the camera user recognizes that the subject brightness is low by the LED 29, which lights up when the transistor 6 becomes conductive, and returns the shutter release button to its original state, the transistor 1
The conduction period 1 is the period from the start of charging of the capacitor 10 when current is flowing through the resistor 8 to the completion of charging,
Needless to say, this period is the operating period of the DC-DC converter circuit 15.

As is clear from the actions described above,
The basic operation of the power wastage prevention means according to the present invention is such that energy is consumed only when the brightness of the subject is low and when photographing is attempted, making it possible to use power source energy efficiently and efficiently. .

Furthermore, when the period counted by the timer circuit 7 stops after the switch 2 is turned off, the main capacitor 24 starts to self-discharge, and the charge in the trigger capacitor 20 is instantly discharged via the resistors 19 and 25. released. Therefore, this example:
When the DC--DC converter circuit 15 stops operating, the flash discharge tube immediately becomes unable to emit light, and if light emission is required, the switch 2 must be turned on again.

On the other hand, when the shutter release button is pressed while the DC-DC converter circuit 15 is in operation and the main capacitor 4 etc. are ready to emit light, that is, in a fully charged state, the synchro switch 22 is closed. It goes without saying that the trigger circuit 18 performs a well-known operation and the flash discharge tube 23 emits light.

By the way, as described above, when the brightness of the object changes while the DC-DC converter circuit 15 is operating and the flash discharge tube no longer requires light emission, or when the flash camera is suddenly tried to be stored, There is no need to operate the DC-DC converter circuit 15 until the predetermined time set by the timer circuit 7 described above has elapsed;
Needless to say, if the energy supply from 6 is cut off, the power source 26 can be used more effectively. In this embodiment, a lock switch 27 and a resistor 28 are provided to perform the above functions.

As is clear from FIG. 1, this lock switch 27 connects the capacitor 10 to both ends of the power supply 26 via the resistor 28 when it is closed, and also connects the capacitor 10 to both ends of the power supply 26 by the power supply 26 at this time. The charging time constant is set to be much shorter than the time constant via the resistors 8 and 9. Therefore, in operation, the lock switch 27
When the capacitor 10 is closed, charging of the capacitor 10 is immediately completed and the time counting operation of the timer circuit 7 is completed, and the operation of the DC-DC converter circuit 15 is stopped, thereby preventing unnecessary energy usage. . The lock switch 27 cuts off the supply of energy when it is closed, and since it is connected to the transistor 6, it can be easily closed, or it can be closed at the same time as the switch 2. If the configuration is such that there is a risk of inconvenience, it goes without saying that consideration should be given to linking the shutter release lock mechanism with the operation of a shutter release lock mechanism that restricts the pressing operation of the shutter release button, for example. .

As described above, the present invention reduces the consumption of power supply energy by a strobe device in a flash camera by connecting the switch element provided in the base current supply loop of the oscillation transistor constituting the DC-DC converter circuit of the strobe device. A timer circuit that controls the operation and a subject brightness detection circuit that controls the timing of the operation of the timer circuit are connected to the subject brightness and a predetermined time, and the configuration allows extremely effective use of power without waste. This provides a simple means to prevent power wastage.

[Brief explanation of drawings]

The figure is an electrical circuit diagram showing an embodiment of a device for preventing power wastage in a flash camera according to the present invention. 1... Subject brightness detection circuit, 2... Switch,
3... Light receiving sensor, 7... Timer circuit, 8, 9
...Resistor, 10...Capacitor, 11,14...
Transistor, 15...DC-DC converter circuit, 16...Oscillation transistor, 18...Trigger circuit, 23...Flash discharge tube, 24...Main capacitor, 26...Power supply, 27...Lock switch,
28...Resistance.

Claims (1)

[Claims] 1. A DC-DC converter circuit that boosts the voltage of a low-voltage DC power supply including an oscillation transformer and an oscillation transistor, a main capacitor charged by the output of this DC-DC converter circuit, and a main capacitor connected to the main capacitor. In a flash camera having a built-in strobe device having a flash discharge tube and a trigger circuit for controlling light emission of the flash discharge tube, when the strobe device is provided in a base current supply loop to the oscillation transistor by the power supply and becomes conductive. a first switch element that supplies a base current to the oscillation transistor; a resistor and a capacitor connected in series between both ends of the power supply; A second switch element that is brought into conduction by a charging current flowing through the capacitor or a charging current flowing through a switch circuit connected in parallel with the capacitor, thereby making the first switch element conductive and operating the DC-DC converter circuit. a timer circuit having a switch element; a light receiving sensor for detecting subject brightness; and a light receiving sensor connected in parallel to the capacitor and controlled by the output of the light receiving sensor, the subject brightness to a predetermined value that requires light emission of the flash discharge tube. The switch circuit is made conductive by the output of the light receiving sensor to discharge the charge in the capacitor when and a subject brightness detection circuit having a switch that supplies operating power from the camera, and charges the capacitor when the switch is turned on and the subject brightness is above a predetermined value, or when the switch is opened. A device for preventing power wastage in a flash camera, characterized in that the operation of the DC-DC converter circuit is stopped when the current stops flowing. 2. A patent claim characterized in that a series body is provided in parallel with the resistor, the lock switch interlocking with the operation lock mechanism of the shutter release button, and a second resistor having a resistance value lower than the resistance value of the resistor. A device for preventing power wastage in a flash camera according to item 1.