JPH0461797A - Light emission control circuit of electronic flash device - Google Patents

Abstract

PURPOSE:To automatically generate the pulse luminescence of a luminescent tube by means of giving a luminescence command signal only once for the accomplishment of a preparatory operation by detecting that the cathode of the luminescent tube has turned into a negative voltage, and triggering a trigger circuit so as to generate the luminescence of a luminescent tube. CONSTITUTION:High voltage applying circuits LC21, 23 turn the cathode of a luminescent tube 19 into a negative voltage and apply a higher voltage than the charging voltage of a main capacitor 6 to between the anode and the cathode of the luminescent tube 19. Luminescence starting circuits SC13, 14 detect that the cathode of the luminescent tube 19 has turned into the negative voltage and trigger circuits TC8 to 10 to apply a trigger voltage to the luminescent tube 19 for generating the luminescence of the luminescent tube 19. Thus, inputting two signals of a luminescence preparation signal and a luminescence starting signal to a predetermined timing becomes unnecessary so that an accurate pulse luminescence generation can be performed by giving a luminescence command signal only once.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a light emission control circuit for an electronic flash device that performs optical communication by causing an arc tube to emit flash light.

B. Prior Art Conventionally, a light emission control circuit for an electronic flash device as shown in FIG. 5 has been known.

In FIG. 5, 1 is a power source such as a battery, 2 is a power switch, 3 is a known booster circuit that boosts the voltage of power source 1, 4 is a diode, 5 is a coil, 6 is a main capacitor that stores luminous energy, and 19 is a It is a luminous tube that emits light by receiving luminous energy from the main capacitor 6.

18 is a thyristor which is a switching element connected in series with the arc tube 19, and 21 is a capacitor.

23 is a coil, and these constitute an LC resonance circuit (high voltage application circuit) LC that applies a negative high voltage to the cathode (point A) of the arc tube 19 prior to light emission. Also, 20
is a resistor that supplies power to and charges the capacitor 21 from the high voltage line L1. The signal line L3 of the light emission mode command circuit 24 is connected to the gate of the thyristor 18 through the resistor 1.
5, and a light emission preparation signal is input. Note that a resistor 16 and a capacitor 17 are connected between the gate and cathode of the thyristor 18 to protect the gate and prevent noise from entering the gate.

8 is a trigger transformer, 9 is a trigger capacitor, and 26 is a trigger thyristor.
Configure C. Further, the series circuit of the resistor 7 and the diode 22 is connected to the LC resonant circuit LC so as to charge the trigger capacitor 9 every time the LC resonant circuit LC operates. The signal line L4 of the light emission mode command circuit 24 is connected to the gate of the trigger thyristor 26 through the resistor 2.
5, and a light emission start signal is input. Note that a resistor 12 and a capacitor 1 for protection and noise prevention are installed between the gate and cathode of the trigger thyristor 26.
1 is connected.

Figure 6 shows the points A-C shown in Figure 5 and the signal line L.
3. 7 is a timing chart showing changes over time in the voltage of L4.

The operation of the light emission control circuit of a conventional electronic flash device will be explained with reference to FIGS. 5 and 6.

When the power switch 2 is closed, the booster circuit 3 starts operating, charging the main capacitor 6 via the coil 5 and charging the capacitor 21 of the LC resonance circuit via the resistor 20. After the charging voltage of the main capacitor 6 reaches the voltage at which the arc tube 19 can emit light, the light emission mode command circuit 24 outputs a light emission preparation signal from the signal line L3 at time 10 in FIG. This signal is input to the gate of the thyristor 18 via the resistor 15, and the anode and cathode of the thyristor 18 are made conductive.

Due to conduction of thyristor 18, a closed loop of capacitor 21 → thyristor 18 → coil 23 is formed, and coil 2
3 and the capacitor 21 cause LC resonance. At this time, one end of the capacitor 21 at point A is short-circuited to the reference potential L2 by the thyristor 18, so the voltage at the other end at point B changes as shown in FIG. (V). On the other hand, the trigger capacitor 9 is charged via the diode 22 and the resistor 7 from time t1 to time t2 in FIG.

At time t2, the LC of the coil 23 and capacitor 21
The current flowing through the resonant circuit LC tries to reverse, but since the thyristor 18 is a unidirectional element, it becomes non-conductive, and B
The potential at the point changes discontinuously up to 0 (V), which is the reference potential, and thereby the potential at point A changes to -H (V).

That is, the anode of the arc tube 19 is connected to the main capacitor 6.
The charging voltage H (V) is applied to the cathode, and the cathode is biased to -H (V), and a high voltage approximately twice the charging voltage of the main capacitor 6 is applied between the anode and cathode of the arc tube 19 .

At time t3, when a light emission start signal is output from the light emission mode command circuit 24 to the signal line L4, this signal is input to the gate of the trigger thyristor 26 via the resistor 25, and the signal is input between the anode and cathode of the trigger thyristor 26. conducts. As a result, the already charged trigger capacitor 9 is instantly discharged via the primary winding of the trigger transformer 8, and a high voltage is generated in the secondary winding of the trigger transformer 8.

This high voltage is applied to the arc tube 19, and the arc tube 19 becomes excited and starts emitting light. At this time, since the thyristor 18 connected in series with the arc tube 19 has already become non-conductive, the luminous current flowing through the arc tube 19 is reduced to the capacitor 2.
1, and the capacitor 21 is charged. Then, upon completion of charging the capacitor 21, the arc tube 19 stops emitting light.

That is, the arc tube 19 emits pulsed light for the charging time of the capacitor 21.

In this way, prior to - times of pulse emission, the thyristor 18 is turned on by the emission preparation signal to operate the LC resonance circuit, and a high voltage is applied to both ends of the arc tube 19.
Charge the capacitor 9 of the trigger circuit TC. And L
After the operation of the C resonance circuit TC is completed and the thyristor 18 is turned off, the trigger circuit TC is activated by the 1 light emission start signal to cause the arc tube 19 to emit light.

C0 Problems to be Solved by the Invention However, the light emission control circuit of the conventional electronic flash device requires two control signals, a light emission preparation signal and a light emission start signal, in order to perform - times of pulsed light emission, and moreover, the light emission control circuit of the conventional electronic flash device requires two control signals, a light emission preparation signal and a light emission start signal. There is a problem in that normal pulsed light emission cannot be performed unless the start signal is input at a timing after the thyristor 18 of the LC resonant circuit LC is turned off. That is, if the light emission start signal is input before the thyristor 18 of the LC resonance circuit LC is turned off, the light emission current of the arc tube that has started emitting light will not flow to the capacitor 21 that determines one light emission time, but will flow through the thyristor 18 which is conducting. Since the voltage flows to the reference potential L2, the desired light emission time cannot be obtained.

Furthermore, when changing the capacitance of the capacitor 21 to change the pulse emission time, calculate the time for the thyristor 18 to turn off from the resonance period of the LC resonant circuit LC each time, input the 1 emission preparation signal, and then input the emission start signal. I had to reconsider the time interval between inputs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light emission control circuit for an electronic flash device that performs a preparatory operation for light emission by simply applying a light emission command signal once, and automatically causes the light emitting tube to emit pulse light when ready to emit light. .

09 Means for Solving the Problems The present invention will be explained in conjunction with FIG. 1 showing an embodiment.
and (2) an arc tube 19 that emits light by receiving luminous energy supplied from the main capacitor 6, a switching element 18 connected in series with the arc tube 19, and a negative voltage applied to the cathode of the arc tube 19 to control the arc tube 19. A high voltage application circuit LC (21, 23) applies a voltage higher than the charging voltage of the main capacitor 6 between the anode and cathode, and a trigger circuit TC ( 8, 9, 10) is applied to a light emission control circuit of an electronic flash device.

Then, the high voltage application circuit LC (21, 23) detects that the cathode of the arc tube 19 has become a negative voltage, and activates the trigger circuit TC (8, 9, 10) to cause the arc tube 19 to emit light. By providing the circuit 5c (13, 14), the above object is achieved.

The high voltage applying circuit LC (21, 23) applies a voltage higher than the charging voltage of the main capacitor 6 between the anode and cathode of the arc tube 19 by applying a negative voltage to the cathode of the arc tube 19. The light emission starting circuit 5c (13, 14) is one light emitting tube 19
It is detected that the cathode of has become a negative voltage, and the trigger circuit TC (8°9.10) is activated to apply a trigger voltage to the arc tube 19, causing the arc tube 19 to emit light.

In the above-mentioned sections and section E, which describe the present invention in detail, figures of embodiments are used to make the present invention easier to understand, but the present invention is not limited to the embodiments.

F. Embodiment FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a time chart showing changes over time in the voltage at points A to C in FIG. 1 and at L3. Components similar to those in FIG. 5 showing the conventional light emission control circuit are designated by the same reference numerals, and the explanation will focus on the differences.

In FIG. 1, 10 is a triac, the gate of which is connected to the cathode of an arc tube 19 via a resistor 13 and a diode 14. That is, the resistor 13 and the diode 14 constitute a light emission starting circuit SC, and when the cathode of the light emitting tube 19 becomes a negative voltage, the gate of the triac 10 is biased in the forward direction by the same circuit, the triac 10 becomes conductive, and the trigger circuit is activated. will be activated. Also,
In the conventional light emission control circuit shown in FIG. 5, a series of light emission is performed using a light emission preparation signal outputted from the light emission mode command circuit 24 via the signal line L3 and a light emission start signal outputted via the signal line L4. However, in this embodiment, a series of light emission sequences is controlled only by the light emission command signal outputted from the light emission mode command circuit 24 via the signal line L3.

Next, the operation of this circuit will be explained.

From when the power switch 2 is closed until time t2 in FIG. 2, the circuit operates in the same manner as the conventional light emission control circuit shown in FIGS. 5 and 6 described above, and at time t2, the cathode A of the arc tube 19 The potential at the point is biased to -H (V), and the potential at the -18 point is biased to the charging voltage H (V) of the main capacitor 6.
Furthermore, the potential at one end of the trigger capacitor 9 at point C is also approximately H (
V) and ready to emit light.

At this time mark 2, the cathode of the arc tube 19 (point A)
When the voltage changes to -H (V), this negative voltage is applied to the gate of the triac 10 via the resistor 13 and the diode 14, and conduction occurs between the anode and cathode of the triac 10, causing the trigger capacitor 9. A trigger circuit TC composed of a trigger transformer 8 and a triac 10 is activated. Then, the trigger voltage induced on the secondary side of the trigger transformer 8 is applied to the arc tube 19, and the arc tube 19 starts emitting light. However, since the thyristor 18 connected in series with the arc tube 19 has already become non-conductive,
The light emitting current flowing through the arc tube 19 flows to the capacitor 21 and charges the capacitor 21. Then, one pulse emission ends when the capacitor 21 is completely charged.

In this way, when the LC resonance circuit LC is activated by the light emission command signal and the cathode potential of the first arc tube 19 changes from 0 to negative, the LC resonance of the capacitor 21 and the coil 23 causes a negative potential to be applied to the cathode of the arc tube 19. When a high voltage is applied, which is approximately twice the charging voltage of the main capacitor 6, between the anode and cathode of the arc tube 19, and when the trigger capacitor 9 has been charged and ready to emit light. Then, the triac 10 of the trigger circuit TC is turned on via the diode 14 and the resistor 13, and the trigger circuit TC is activated to cause the arc tube 19 to emit light, so that accurate pulsed light emission can be performed with only the light emission command signal.
There is no need to input two systems of signals, that is, a light emission preparation signal and a light emission start signal, at preset timings as in the conventional case.

Furthermore, even if the capacitance of the capacitor or the inductance of the coil changes, accurate pulsed light emission can be performed without any problem.

FIG. 3 is a circuit diagram showing another embodiment of the present invention, and FIG. 4 is a time chart showing changes over time in the voltage at point A-C and L3 in FIG. 1 and 2 showing the above-described embodiment and FIGS. 5 and 6 showing the conventional example, the same reference numerals are given to the same parts, and the explanation will focus on the differences.

In the embodiment described above, the triac 10 was used as a switching element for starting the trigger circuit TC, but in this embodiment, a thyristor 26 is used as shown in FIG. 3. A diode 30 constituting a light emission starting circuit SC is connected between the cathode of the trigger thyristor 26 and the cathode of the arc tube 19. Further, a Zener diode 27 is connected between the gate and cathode of the trigger thyristor 26, and a series body of a resistor 28 and a diode 29 is connected between the gate of the trigger thyristor 26 and the reference potential L2. Further, as in the above-described embodiment, only a light emission command signal is output from the light emission mode command circuit 24 via the signal line L3, thereby controlling the series of light emission sequences.

Next, the operation will be explained.

From the time when the power switch 2 is closed until the time L2 in FIG. 4, the operation is the same as that of the above-described embodiment and the conventional light emission control circuit, and at time t2, the potential at the cathode point A of the arc tube 19 becomes -H( At V), the potential at point Anno-18 is biased to the charging voltage H (V) of the main capacitor 6, and the potential at point C at one end of the trigger capacitor 9 is also charged to approximately H (V), completing preparation for light emission. .

At this time t2, the cathode of the arc tube 19 (point A)
When becomes -H (V), the potential of the cathode of the trigger thyristor 26 also becomes approximately -H (V) via the diode 30. On the other hand, since the gate of the trigger thyristor 26 is connected to the reference potential L2 via the resistor 28 and the diode 29, the gate of the trigger thyristor 26 is biased when the cathode of the trigger thyristor 26 becomes a negative potential, and the anode Conductivity occurs between the cathodes. And trigger capacitor 9. The trigger circuit TC constituted by the trigger transformer 8 and the trigger thyristor 26 is activated, a trigger voltage is applied to the arc tube 19, and light emission begins. but,
Since the thyristor 18 connected in series with the arc tube 19 is already non-conductive, the light emitting current flowing through the arc tube 19 flows to the capacitor 21 and charges the capacitor. That is, the light emission ends when the capacitor 21 is completely charged.

In this way, when the LC resonance circuit LC is activated by the light emission command signal and the cathode potential of the arc tube 19 changes from 0 to negative, the LC resonance of the capacitor 21 and the coil 23 causes the cathode of the arc tube 19 to have a negative potential. When a high voltage is applied, which is approximately twice the charging voltage of the main capacitor 6, between the anode and cathode of the arc tube 19, and when the trigger capacitor 9 has been charged and ready to emit light. Then, the trigger thyristor 26 is turned on via the diode 30, and the trigger circuit TC is activated to cause the arc tube 19 to emit light, so that accurate pulsed light emission can be performed using only the light emission command signal, as in the embodiment described above.

In addition, in the two embodiments described above, the light emission mode command circuit 24
The light emission command signal output from the signal line L3 to the signal line L3 is a signal with a short pulse width as shown in FIGS. 2 and 4. However, if this pulse width is set longer than time t2,
9 emits full light instead of pulsed light.

Furthermore, in the two embodiments described above, the energy required for the next light emission of the capacitor 21 forming the LC resonant circuit LC is:
Since it is stored by the light emission current of the arc tube 19, high-speed pulsed light emission can be repeated, and is applied, for example, to remote control devices using optical communication and strobe lights that emit light in synchronization with the high shutter speed of a camera.

As described in detail of the G0 invention, according to the present invention, the light emission starting circuit detects that the cathode of the arc tube has a negative potential and a high voltage is applied between the anode and cathode, and the detection causes light emission. The starting circuit activates the trigger circuit to cause the light emitting tube to emit pulses, so there is no need to input two signals, a light emission preparation signal and a light emission start signal, at preset timings as in the past, and the light emission command signal can be input once. Accurate pulsed light emission can be performed just by feeding the light.

Further, even if the capacitance of the capacitor and the inductance of the coil related to pulsed light emission change, pulsed light emission can be performed accurately without any problem.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, and Fig. 2 is a circuit diagram showing an embodiment of the present invention.
A time chart showing voltage changes at each point of the circuit shown in the figure,
FIG. 3 is a circuit diagram showing another embodiment of the present invention, FIG. 4 is a time chart showing voltage changes at each point of the circuit shown in FIG. 3, FIG. 5 is a circuit diagram showing a conventional example, and FIG. The figure is a time chart showing voltage changes at each point of the circuit shown in FIG. 3: Boost circuit 1o: Triac 13.28:
Resistor 18: Thyristor 19: Arc tube 2
1: Capacitor 23: Coil 24: Light emission mode command circuit 27: Zener diode Ll: High voltage line L2: Reference potential L3. L4: Signal line LC: LC resonant circuit TC:)-Tsuga circuit 80: Light emission starting circuit

Claims (1)

[Scope of Claims] A main capacitor that stores luminous energy, an arc tube that receives luminous energy from the main capacitor and emits light, a switching element that is connected in series with the arc tube, and a cathode of the arc tube. a high voltage application circuit that applies a negative voltage higher than the charging voltage of the main capacitor between the anode and cathode of the arc tube; and a trigger circuit that applies a trigger voltage to the arc tube prior to the emission of light from the arc tube. In the light emission control circuit for an electronic flash device, the light emission starting circuit detects that the cathode of the arc tube has become a negative voltage by the high voltage application circuit and activates the trigger circuit to cause the arc tube to emit light. A light emission control circuit for an electronic flash device, comprising: