JPH07263167A - Light emission control circuit of electronic flashing apparatus - Google Patents

Abstract

PURPOSE:To prevent the omission of light emission at continuous light emission by applying voltage larger than the charge voltage of a main capacitor to both ends of a light emitting tube at light emission. CONSTITUTION:An IGBTQ to apply a control signal TG to a gate is turned on, and a closed loop resonance circuit composed of a capacitor C3, an inductance L2, and the IGBTQ starts resonance, and nodes C and D goes up gradually to positive potential, and a capacitor C5 is charged. By this charge, the voltage about twice as high as the charge voltage of a main capacitor C1 is applied to the node A at the junction between the capacitor C4 of a double voltage applying means and a light emitting tube Xe, and voltage higher than the charge voltage of the capacitor C1 is applied to both ends of the light emitting tube Xe. Hereby, it becomes possible for the light emitting tube to emit light as far as low voltage, and the omission of light emission at continuous light emission is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emission control circuit for an electronic flash device, and more particularly to a voltage application circuit for applying a voltage higher than a charging voltage of a main capacitor to both ends of the light emission tube prior to light emission of the light emission tube. The present invention relates to a light emitting circuit of an electronic flash device.

[0002]

2. Description of the Related Art Heretofore, there has been proposed an electronic flash device using an insulated gate bipolar transistor (hereinafter referred to as an IGBT) as a switching element for controlling a light emitting current flowing through an arc tube. FIG. 3 shows an example of a light emission control circuit of an electronic flash device using an IGBT as a switching element. In FIG. 3, a main capacitor (not shown) is connected between the power supply line La connected to the output terminal of a power supply booster circuit (not shown) and the reference potential line Lb, and the main capacitor is charged with light emission energy and triggers. Resistor R for capacitor C7
It is charged through 1.

In this state, when a light emission starting signal is output from the control circuit (not shown) to the control terminal TG of the IGBTQ, I
Conduction is made between the collector and the emitter of GBTQ. As a result, the electric charge of the trigger capacitor C7 is discharged in the closed loop formed between the primary winding of the trigger transformer T, the trigger capacitor C7, and the collector / emitter of the IGBTQ, and a trigger voltage of several thousand V is applied to the arc tube Xe. The arc tube Xe is excited by the application of this trigger voltage to start emitting light. When a dimming circuit (not shown) outputs a dimming signal, the signal output to the control terminal TG is stopped. As a result, the collector and emitter of the IGBTQ become non-conductive, and the light emission of the arc tube Xe is stopped.

[0004]

However, in the circuit configuration shown in FIG. 3, since the main capacitor (not shown) is connected in series at both ends of the arc tube Xe, the arc tube Xe is connected at a voltage higher than the voltage of the main capacitor. It cannot be driven. When the main capacitor is sufficiently charged, the arc tube Xe does not fail to emit light, but when light is emitted continuously, for example, several tens Hz.
It is known that the temperature of the light emitting tube Xe rises when the light is repeatedly emitted, and the minimum light emitting voltage of the light emitting tube Xe also rises with it, and the light emission may not occur at the voltage of the main capacitor. . At the same time, the charging voltage of the main capacitor gradually decreases due to light emission,
If it is used continuously, it may not emit light. Further, the arc tube Xe has a characteristic that the luminous efficiency is increased by increasing the gas pressure to be enclosed inside the glass tube. However, in this case, the minimum luminous voltage is also increased at the same time, which makes it difficult to emit light. Will be. Therefore, there is a possibility that the ready light may not be emitted even though the ready light is turned on when the electronic flash device is used.

Therefore, the present invention has been made in order to solve the above-mentioned conventional problems, and an object thereof is an electronic flash device capable of repeatedly emitting light from an arc tube and preventing occurrence of light emission omission. To provide a light emission control circuit.

[0006]

In order to achieve such an object, in the present invention, when this is embodied, it becomes as shown in FIG. 1, for example. That is, when a light emission start signal is applied to the control terminal TG of the IGBTQ, the collector and the emitter of the IGBTQ become conductive, and the connection point B becomes almost the same potential as the reference potential line Lb which is the reference potential. Also, IG
BTQ collector / emitter, diode D3, capacitor C3 as second voltage multiplying means, and inductor L
A closed loop is formed by 2 and LC resonance is started. As a result, the potential at the connection point C gradually rises from the negative voltage to the positive voltage, and the potential at the connection point D also rises via the diode D4, and the capacitor C5 is charged. In addition,
Since this closed loop can be discharged only in one direction by the diode D3, the connection point B discontinuously changes to a negative voltage and becomes a negative voltage close to the charging voltage of the main capacitor C1.

On the other hand, by the charged capacitor C5, a voltage about twice the charging voltage of the main capacitor C1 is applied to the point A, which is the connection point between the capacitor C4 as the first voltage doubling voltage applying means and the arc tube Xe. To be done. Therefore, a voltage larger than the charging voltage of the main capacitor C1 is applied to both ends of the arc tube Xe. This allows the arc tube Xe to emit light to a lower voltage. Also, I
Between GBTQ collector-emitter and trigger capacitor C
7 and the primary winding of the trigger transformer T form a closed loop, whereby a trigger voltage is applied to the arc tube Xe and the arc tube Xe starts emitting light.

When the light emission start signal of the control terminal TG disappears by a dimmer circuit (not shown), the collector and emitter of the IGBTQ become non-conductive, the light emission of the arc tube Xe is stopped, and the capacitor C2 and the resistor R6 are used. A signal is applied to the gate of the thyristor SCR so that the anode and cathode of the thyristor SCR are electrically connected. As a result, the electric charge of the capacitor C5 is rapidly discharged. At the same time, the capacitor C4 is rapidly charged. Furthermore, the condenser C3 and the trigger condenser C7 are also the arc tube Xe.
The battery is rapidly charged via, and the next light emission preparation is completed.

[0009]

In the present invention, since a voltage higher than the charging voltage of the main capacitor C1 is applied to both ends of the arc tube Xe, even if the charging voltage of the main capacitor C1 decreases due to continuous light emission, light is emitted. It is possible to prevent falling out. Further, a circuit for rapidly charging and discharging the capacitor for voltage application makes it possible to apply a large voltage every time even when light is repeatedly emitted at high speed.

[0010]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a circuit diagram illustrating a configuration of an embodiment of a light emission control circuit of an electronic flash device according to the present invention, and FIG. 2 is a timing chart showing a voltage change at each connection point in FIG. In FIG. 1, C1 is a main capacitor that stores the emission energy of the arc tube Xe, and Q is an insulated gate bipolar transistor (IGBT) that is an emission control element.
And the capacitor C3 as the second voltage multiplying means.
The inductor L2, the diode D3 and the IGBTQ form a closed loop. In this circuit, a voltage having a polarity different from the charging voltage of the main capacitor C1 is applied to the cathode side of the arc tube Xe.

Further, the capacitor C4 and the capacitor C5 as the first voltage doubling means apply a voltage which is about twice the charging voltage of the main capacitor C1 to the anode side of the arc tube Xe. Furthermore, the trigger transformer T and the trigger capacitor C7 constitute a trigger circuit. Also, the resistor R4
The resistor R5, the resistor R6, the thyristor SCR, the capacitor C2, and the capacitor C6 set and reset the capacitors C4 and C5.

In the figure, La is a power supply line to which a high voltage is applied, Lb is a reference potential line, and TG is a control terminal of the IGBTQ. Further, the connection point of the diode D2, the resistor R1, the arc tube Xe and the capacitor C4 is A
And the connection point of the arc tube Xe, the resistor R1, the capacitor C3, the diode D3, and the trigger transformer T is point B,
A connection point between the diode D4, the capacitor C3, and the inductor L2 is defined as a point C, and a connection point between the capacitor C4, the diode D4, the resistor R4, the capacitor C5, and the resistor R2 is defined as a point D.

The operation of the light emission control circuit of the electronic flash device thus configured will be described with reference to the timing chart shown in FIG. Here, when the main capacitor C1 is charged to a predetermined voltage by a power supply boosting circuit (not shown),
The capacitor C3 is charged through the path of the diode D2, the resistor R1, the capacitor C3 and the inductor L2, and the capacitor C4 is charged by the diode D2, the capacitor C4 and the resistor R2.
It is charged via the route. Further, the capacitor C7 is also charged via the resistor R1 and the trigger transformer T.

In this state, when a light emission activation signal as shown in FIG. 2A is output from the control circuit (not shown) to the control terminal TG at time t ₀ as shown in FIG. 2, I
The collector and the emitter of the GBTQ are electrically connected, and the connection point B becomes the ground potential which is almost the reference potential as shown in FIG. 2 (c). As a result, a closed loop is formed between the capacitor C3, the inductor L2, the diode D3 and the IGBTQ, LC resonance is started, and the potential at the connection point C is shown in FIG.
As shown in, changes from time t ₀ to time t ₂ .

The capacitor C5 receives the voltage change at the connection point C and is charged to almost the same potential as the connection point C via the diode D4 (time t ₁ to time t _{2 in} FIG. 2 (e)). Since the capacitor C4 has already been charged, the potential at the connection point A also rises as the potential at the connection point D rises (time t ₁ to time t _{2 in} FIG. 2B). As a result, the main capacitor C1 is provided on the anode side of the arc tube Xe.
A voltage that is about twice the charging voltage is applied.

On the other hand, the potential of the connection point B changes discontinuously at time t ₂ in FIG. 2 because the LC resonance is performed only in one direction by the diode D3, and the main capacitor C1 is provided on the cathode side of the arc tube Xe. A potential having a polarity different from that of the charging voltage is applied. As a result, at both ends of the arc tube Xe,
A voltage that is about three times the charging voltage of the main capacitor C1 will be applied. At the same time, the primary winding of the trigger transformer T, the trigger capacitor C7, the diode D3, and I
A trigger voltage of several thousand V is applied to the arc tube Xe by a closed loop formed between the collector and the emitter of the GBTQ, whereby the arc tube Xe is excited and emits light (FIG. 2 (f)).

When a light emission stop signal is output by a light control circuit (not shown) after the light emission of the arc tube Xe, the IGBT
The signal at the control terminal TG, which is the gate of Q, disappears (see FIG. 2).
At time t _{3 in} (a), the collector-emitter of the IGBTQ becomes non-conductive, and the light emission of the arc tube Xe is stopped as shown in FIG. 2 (f). At the same time capacitor C
2, a signal is output to the gate of the thyristor SCR via the resistor R6, and the anode and cathode of the thyristor SCR are electrically connected.

As a result, the capacitor C4 is rapidly charged through the resistor R4, and the capacitor C5 is rapidly discharged through the resistor R5. The capacitor C3 is also rapidly charged via the inductor L2, and similarly, the trigger capacitor C7 is also rapidly charged via the primary winding of the trigger transformer T. The capacitors C3 and C7 are charged by the residual current flowing through the arc tube Xe. This completes the settings required for the next light emission.

In the above-mentioned embodiments, the case where the IGBT is used as the light emission control element has been described, but the present invention is not limited to this IGBT.
Needless to say, the same effect as described above can be obtained by using a light emission control element or a light emission control circuit formed by combining a plurality of transistors.

[0020]

As described above, according to the present invention, a voltage higher than the charging voltage of the main capacitor is applied to both ends of the arc tube during light emission to prevent light emission dropout that tends to occur during continuous light emission, and further to emit light. Since the next setting is performed by using the light emission current etc. at the end, it is configured so that a large voltage can be applied to the arc tube every time even during high-speed repeated light emission (several tens Hz to several tens KHz). An extremely excellent effect that there is no need to worry about omission is obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration according to an embodiment of a light emission control circuit of an electronic flash device according to the present invention.

FIG. 2 is a diagram showing a timing chart at each connection point for explaining the operation of the circuit diagram of FIG.

FIG. 3 is a circuit diagram showing a configuration of a light emission control circuit of a conventional electronic flash device.

[Explanation of symbols]

 La power line Lb reference potential line C1 main capacitor Xe arc tube Q light emission control element (IGBT) D3 diode L2 inductor T trigger transformer C4 capacitor C5 capacitor C7 capacitor

Claims (3)

[Claims] 1. An arc tube and a switching element connected in series between a power supply line connected to a power supply voltage and a reference potential line; and a power supply voltage connected between the power supply line and the reference potential line. A main capacitor that stores electric charge that causes the arc tube to emit light, a trigger circuit that applies a trigger voltage to the arc tube, and a charging voltage of the main capacitor that has the same polarity and is high at one end of the arc tube. First voltage applying means for applying a voltage, and second voltage applying means for applying a voltage having a polarity different from the charging voltage of the main capacitor to the other end side of the arc tube,
A light emission control circuit for an electronic flash device, comprising: 2. An arc tube and a switching element connected in series between a power supply line connected to a power supply voltage and a reference potential line, and a unidirectional element connected between the arc tube and the switching element. A main capacitor that is connected between the power supply line and a reference potential line and that stores a charge that is charged by the power supply voltage to cause the arc tube to emit light; and a trigger circuit that applies a trigger voltage to the arc tube. A first voltage applying means for applying a voltage having a polarity equal to and higher than the charging voltage of the main capacitor to one end side of the arc tube, and having a polarity different from the charging voltage of the main capacitor at the other end side of the arc tube. Second voltage applying means for applying a voltage,
A light emission control circuit for an electronic flash device, comprising: 3. The light emitting device according to claim 1, wherein the first voltage applying means and the second voltage applying means are each formed of a capacitor, the switching element is turned off, and the light emission of the arc tube is stopped. A light emission control circuit for an electronic flash device, which is characterized in that it is rapidly charged at the point of time.