JPS6318338A - Electronic flash device - Google Patents

Abstract

PURPOSE:To prevent a photograph from being taken while the quantity of emitted light is deficient by providing a display means which generates a warning when the charging voltage of a 1st main capacitor does not reach a prescribed value. CONSTITUTION:When a power switch 1 is turned on, an oscillation voltage boosting circuit 8 operates to start charging the 1st main capacitor 12 with small capacity in an initial state. At this time, the output of a comparator 16 is at low level and a transistor (TR) 18 is kept off, so a photothyristor coupler 26 does not begin to charge a main capacitor 13 which is turned off. When the charging voltage of the main capacitor 12 does not reaches a constant value, the output voltages of comparators 16 and 21 are still in the initial state and the output of the comparator 21 is at high level; and the base voltage of a TR 5 rises gradually up to its turn-on voltage and then the TR 5 turns on, thereby lighting a light emitting diode 4 for display.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to an electronic flash device for a camera.

<Prior art> In conventional electronic flash devices for cameras, light can be emitted after the main capacitor is fully charged.
When the voltage of the main capacitor with a small capacity exceeds a certain voltage, the main capacitor with a large capacity starts charging. If the voltage does not exceed a certain value, charging of the main capacitor with a large capacity does not start, and therefore, there is a drawback that a sufficient amount of light emission cannot be obtained during photographing.

<Object of the Invention> The object of the present invention is to solve the above-mentioned problems and to provide an electronic flash device that enables stable light emission by providing a warning display device to prevent photography due to insufficient light emission. It is to provide.

<Embodiment> Figure 1 shows an embodiment of the present invention, in which 1 is a power switch, 2 is a power supply battery, 3 is a resistor, 4 is a light emitting diode, 5 is a transistor, 6 is a delay capacitor, and 7 is a resistor. 7 constitutes a warning display circuit. 8 is an oscillation booster circuit, 9 is a resistor, 10° 11 is a rectifying diode, 12 is a first main capacitor, 13 is a second main capacitor, 26 is a photothyristor coupler, 14.15 is a resistor, 16 is a first 17 is a resistor, 18 is a transistor, resistor 9 and photothyristor coupler 26. The resistor 9 to the transistor 18 constitute a charging control circuit for the second main capacitor 13. The resistors 19 and 20 and the second comparator 21 constitute a control circuit for displaying a warning. 2
2 is a trigger circuit, 23 is a synchro contact, 24 is a flash discharge tube, and 25 is a diode.

Next, the operation of the circuit shown in FIG. 1 will be explained with reference to the drawings.

When the power switch 1 is turned on, the oscillation booster circuit 8 is activated, and in the initial state, the first main capacitor 12 with a small capacity is
However, since the output of the comparator 16 is at a low level and the transistor 18 is off, the photothyristor coupler 26 is turned off, so charging of the main capacitor 26 is not started. Also, at this time, the output of the comparator 21 is at a high level, and the base voltage of the transistor 5 gradually rises due to the time constant determined by the capacitor 6 and the resistor 7, so the transistor 5 does not turn on immediately, so it is not necessary to display a warning. The light emitting diode 4 does not light up immediately. Regarding the following two cases,
The operation will be explained using FIGS. 1 and 2.

(1) When the charging voltage of the main capacitor 12 rises above a certain value, the charging voltage of the main capacitor 12 reaches a certain value Vr in FIG.
The output of becomes high level, the transistor 18 is turned on, the photothyristor coupler 13 is turned on, and charging of the second main capacitor 13 with a large capacity starts (see Fig. 2).
a) Solid line). At this time, the output of the comparator 21 becomes a low level, the transistor 5 is turned off, and the light emitting diode does not light up.

(2) When the charging voltage of the main capacitor 12 does not reach a certain value, in this case, the output voltage of the comparator 16゜21 remains in the initial state, and the photothyrist coupler 13 remains off as described above. , charging of the main capacitor 13 is not started (dashed line in FIG. 2). At this time, the output of the comparator 21 is at a high level, and the transistor 5
The base voltage gradually increases until it reaches a turn-on voltage (broken line in FIG. 2(b)), turns on the transistor 5, and lights up the display light emitting diode 4.

In this embodiment, as shown in FIG. 2(b), the timing at which the above-mentioned light emitting diode 4 lights up is determined by the charging time t of the capacitor 6 when the transistor 5 turns on. When the seventh charge reaches the turn-on voltage of the transistor 5, if the comparator 21 is not inverted, the light emitting diode 4 is turned on.

Further, instead of the light-emitting diode lighting display of this embodiment, a blinking display may be used, and furthermore, a piezoelectric buzzer or the like may be used instead of the light-emitting diode.

Effect> As detailed above, in the present invention, when the charging voltage of the first capacitor does not reach a predetermined value and the charging of the second capacitor is not performed, the battery voltage decreases. By displaying the information on the display, it is possible to inform the photographer in advance of the time to replace the battery, and it is possible to prevent failures in taking pictures at photo opportunities and the like.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an electronic flash device showing an example of the present invention, and Fig. 2 is a charging characteristic diagram of two main capacitors and a comparator output voltage and transistor base voltage characteristic diagram of a warning display control circuit. The solid line shows when the charging voltage of the first main capacitor exceeds a certain value, and the broken line shows when the charging voltage of the first main capacitor does not reach the certain value.

Claims (2)

[Claims] (1) first and second main capacitors that store charging energy; charging control means that starts charging the second main capacitor when the charging voltage of the first main capacitor reaches a predetermined value; In an electronic flash device including a flash discharge tube that emits light by the charging energy, a charging voltage of the first main capacitor is determined by a charging detection circuit of the first main capacitor and an output signal of the charging detection circuit. An electronic flash device characterized by comprising: a display means for warning when the value is not reached. (2) The charge detection circuit detects the first charge after a predetermined time has elapsed.
2. The electronic flash device according to claim 1, wherein when a predetermined voltage of the main capacitor is not detected, the display means is lit to give a warning.