JP2778778B2 - Dimmable strobe control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a control circuit for a dimmable strobe, more specifically, a method of controlling the emission and stop of a light emission discharge tube in a dimmable strobe device used for photographing and the like. The present invention relates to a control circuit that performs the processing efficiently.

[Prior Art] As is well known, flashlight photography using a dimmable strobe device causes a light-emitting discharge tube to emit light toward a subject, and stops the light emission when an optimum exposure value is reached. .
Further, in order to control the light emission of the light emitting discharge tube of the above-mentioned strobe device, conventionally, a thyristor is connected in series as a semiconductor switching element to the light emitting discharge tube, and the conduction of the thyristor is controlled on and off. Was common.

However, this conventional thyristor-controlled strobe circuit has a drawback that a firing circuit for turning on the thyristor and a commutation circuit for extinguishing the thyristor are required, which makes the circuit complicated and expensive. .

Therefore, in order to eliminate this drawback, a thyristor is replaced with an insulated gate bipolar transistor (hereinafter referred to as I) which has been put into practical use in recent years.
A flash control circuit using a gate-controlled switching element such as a GBT (see Japanese Patent Application Laid-Open No. Sho 64-17033).
Is provided.

The strobe control circuit using the gate control type switching element does not require a commutation circuit because it uses a self-extinguishing element, which is a function of itself, compared to a conventional strobe control circuit using a thyristor. There is a feature that there is. However, in order to control the control element such as the IGBT to a sufficiently conductive state, it is necessary to apply a voltage of several tens of volts higher than that of the thyristor to its gate.

A means for obtaining a gate voltage as high as several tens of volts has been disclosed in Japanese Patent Application Laid-Open No. Sho 64-17033. I
There is a means shown in the strobe control circuit using GBT. As shown in FIG. 5, the control circuit includes a battery power booster for charging the main capacitor C at a high voltage.
100 is provided with a step-down coil S. The AC voltage induced by the coil S is converted into a DC constant voltage by a constant voltage circuit 101 including a transistor Q ₁ , a zener diode ZD, and a large-capacity smoothing capacitor C _1. conversion, making the gate application voltage of several 10V, so that applied to the gate of the IGBT which via the switching transistor Q _2. Above when the transistor Q ₂ is adapted to the on-operation by the transistor Q ₃ to turn on the light emission start signal generated from the control signal generating circuit 102, also the emission stop signal from the signal generating circuit 102 is issued, the transistor Q ₄
And Q ₅ is turned on, the transistor Q _2, Q ₃ is followed by removal of gate voltage is applied to IGBT by off.

In this strobe control circuit, the discharge tube Xe is connected to the collector of the IGBT connected in series to the discharge tube Xe for light emission.
Xe have been connected trigger transformer T for applying a high voltage trigger voltage to the trigger electrode of which is applied a high pressure is induced in the trigger electrode to trigger transformer T charged in the trigger capacitor C ₂ during conduction of the IGBT It has become so.

On the other hand, FE, which is well known as a gate control switching element,
A flash control circuit using a T (field-effect transistor) is also disclosed in Japanese Patent Application Laid-Open No. Sho 61-50126. In this control circuit, however, the gate voltage of a FET connected in series to a discharge tube for light emission is as follows. The same means as that for obtaining the gate voltage of the IGBT is employed.

[Problems to be Solved by the Invention] However, in a strobe control circuit using a gate control element such as an IGBT or an FET, as described above, a voltage for applying a gate electrode is applied by using a strobe power supply boosting circuit 100. Therefore, an intermediate tap for attaching the step-down coil S to the winding of the step-up transformer must be provided.

The AC voltage induced in the step-down coil S is changed to a stable number.
Transistor to make 10V gate application voltage
Q ₁ , Zener diode ZD, large-capacity smoothing capacitor C
_A constant voltage circuit 101 consisting of ₁ must be provided.

In order to connect a voltage to the gate electrode, a gate circuit 103 including a plurality of switching transistors Q ₂ , Q ₃ , Q ₄ , and Q ₅ having a high withstand voltage is required.

However, there is a disadvantage in that the circuit is complicated and the number of parts is large and the cost is high.

An object of the present invention is to eliminate the above-mentioned conventional drawbacks in a strobe control circuit using a gate control type switching element such as an IGBT, eliminate the need for a complicated gate drive power supply circuit, and reduce the number of parts and reduce the number of parts. An object of the present invention is to provide an optical strobe control circuit.

[Means for Solving the Problems] A control circuit for a dimmable strobe according to the present invention includes a booster circuit including a power supply, a main capacitor charged by the booster circuit, a discharge tube for light emission, and light emission of the main capacitor. In a strobe device having a gate-controlled switching element connected in series in a discharge path including a discharge tube, a start voltage is applied to a trigger electrode of the discharge tube in response to a light emission start signal to make the discharge tube conductive. Exciting trigger means, a series circuit of a diode and a bias capacitor connected in parallel with the gate-controlled first switching element, and charged by a discharge current of the discharge tube which has been excited and turned on. The charged charge is applied to the gate electrode of the first switching element by using the bias capacitor as a power source to make the switching element conductive. And a gate electrode control means including a second switching element for stopping voltage application to the gate electrode in response to the light emission stop signal and returning the first switching element to a non-conductive state. And a booster circuit including a power supply, a main capacitor charged by the booster circuit, a discharge tube for light emission, and a series connection in a discharge path including the discharge tube for light emission of the main capacitor. A strobe device having a gate-controlled first switching element, a trigger means for applying a starting voltage to a trigger electrode of the discharge tube to excite the discharge tube to a conductive state in response to a light emission start signal; A constant voltage generating element connected to the gate terminal of the first switching element of the gate type; A second switching element connected between the first and second terminals, and the strobe device applies a constant voltage generated by the constant voltage generating element to the gate terminal based on a charging voltage from the main capacitor. 1
The first switching element is turned on and the second switching element is turned on in response to the light emission stop signal.
A gate electrode control means for making the switching element non-conductive, further comprising a capacitor provided in parallel with the first switching element, wherein the constant voltage generating element generates a constant voltage by using the charge of the capacitor as a power supply. Occur. The capacitor is charged by a discharge current of the discharge tube.

[Operation] First, at the start of light emission of the strobe, the trigger means is actuated in response to the light emission start signal to excite the discharge tube for light emission to make it conductive. At this time, the first switching element of the gate control type has no bias voltage applied to the gate and is non-conductive, so that the discharge current of the main capacitor from the discharge tube is connected in parallel with this switching element. Charge the self-biasing capacitor. When the capacitor is charged, the terminal voltage of the capacitor rises instantaneously, and a part of the voltage is applied to the gate electrode of the first switching element. As a result, the first switching element becomes conductive, and thereafter, the discharge current flowing through the discharge tube flows through the first switching element, and discharge light emission is continued.

When the light emission is stopped, the application of the bias voltage from the self-bias circuit to the gate electrode is stopped in response to the light emission stop signal, and the first switching element of the self-extinguishing type is turned off to connect the discharge tube to the discharge tube. The current is cut off and light emission is stopped.

EXAMPLES Hereinafter, the present invention will be described with reference to the illustrated examples.

FIG. 1 shows a control circuit of a dimming strobe according to a first embodiment of the present invention, in which a power supply boosting circuit 2 for supplying a high voltage required for discharging a discharge tube 1 for light emission is provided at both ends. A main capacitor 3 for storing the electric charge supplied from the booster circuit 2, a series circuit of the resistor 4, the thyristor 5, and a series circuit of the discharge tube 1 for light emission and the first switching element 8 of the gate control type. It is connected.

The thyristor 5 is turned on when a light emission start signal is applied to the gate of the thyristor 5 from the input terminal 9 to activate the trigger means.
A trigger capacitor 6 having one end connected to a connection point of the trigger tube 7 and the other end connected to a primary winding of a trigger transformer 7, and a secondary winding connected to a trigger electrode 1 t of the discharge tube 1. A trigger transformer 7 for generating a high-voltage pulse for excitation to the electrode 1t; and a thyristor 5 for discharging a charge accumulated in the capacitor 6 through a primary winding of the trigger transformer 7 when turned on. It is composed of

The gate-controlled first switching element 8 is configured such that a bias voltage is applied to its gate electrode 8g,
A self-extinguishing gate-controlled switching element that conducts between the collector 8c and the emitter 8e and becomes non-conductive when the voltage application to the gate electrode 8g is cut off, specifically, an IGBT or power FET It is.

The collector 8 of the first switching element 8
A bias capacitor 11 is connected in parallel between c and the emitter 8e via a backflow preventing diode 10, and a series circuit of a resistor 12 and a zener diode 13 is connected to the capacitor 11 in parallel. A transistor that is a second switching element 14 is connected in parallel to the diode 13.

The bias capacitor 11 is a capacitor for storing a charge for the gate bias of the first switching element 8 and constitutes a self-bias circuit for applying a bias voltage to the gate electrode 8g via the resistor 12.

The backflow prevention diode 10 causes the bias capacitor 11 to charge the discharge current of the discharge tube 1, and the charge of the bias capacitor 11 is discharged through the first switching element 8 even after the first switching element 8 is turned on. Serve to prevent The zener diode 13 is a switching element 8
This is for obtaining a voltage that is sufficient for conduction with respect to the gate electrode 8g and does not cause voltage breakdown of the gate electrode 8g.

On the other hand, when the light emission is stopped, the second switching element 14 is turned on by applying a light emission stop signal to the base electrode of the second switching element 14 from the input terminal 15, and connects the gate electrode 8 g of the first switching element 8 to the second switching element 14. This is a switching element for maintaining the element 8 at a voltage or less at which the element 8 becomes non-conductive.

Next, the operation of the control circuit of the first embodiment thus configured will be described with reference to the time chart shown in FIG.
First, when a power switch (not shown) is turned on, the main capacitor 3 is charged from the power supply booster circuit 2 with a voltage sufficient for the light emitting discharge tube 1 to discharge and emit light. In this state, the trigger capacitor 6 is charged with the same voltage through the resistor 4 and the primary winding of the trigger transformer 7.

In this state, at the start of flash emission, the input terminal 9
When a light emission start signal Va having a voltage required to turn on the thyristor 5 is applied to the thyristor 5, the thyristor 5 is turned on and the charge of the trigger capacitor 6 is discharged through the primary winding of the trigger transformer 7. Then, a high trigger pulse voltage Vt is generated in the secondary winding of the trigger transformer 7 and applied to the trigger electrode 1t of the discharge tube 1. The discharge tube 1 is excited by the application of a high voltage pulse to the trigger electrode 1t, and becomes conductive. At this time, the first switching element 8
Is not conducted yet, and the current discharged from the main capacitor 3 through the discharge tube 1 flows through the backflow preventing diode 10 to the biasing capacitor 11,
Charge. Then, the voltage at both ends of the capacitor 11 rises accordingly, so that the voltage Vc between the emitter 8e and the gate electrode 8g of the first switching element 8 rises via the resistor 12 and the first switching element 8 Turns on.
The operation up to this point is usually performed within several μsec or less because the conduction impedance of the discharge tube 1 is very low.

Discharge tube 1 with charging of bias capacitor 11
Although the voltage of the cathode 1k once rises, the discharge tube 1 once in the excited state is activated and continues to conduct for 100 μsec or more. Therefore, when the first switching element 8 is turned on within a few μsec and the collector 8c and the emitter 8e conduct, the discharge current of the discharge tube 1 flows from the collector 8c of the switching element 8 to the emitter 8e. 1 discharge light emission
Vp continues. When the switching element 8 is turned off, the potential Vc of the collector 8c decreases to several volts or less, but the electric charge once charged in the bias capacitor 11 is changed by the diode 10 in the reverse direction.
, And is discharged only through the resistor 12 and the zener diode 13.

Next, when the light emission of the strobe is stopped, a light emission stop signal Vb for turning on the second switching element 14 is applied to the other input terminal 15. Then, the switching element 14 is turned on, and the potential between the gate electrode 8g and the emitter 8e of the first switching element 8 is lowered. First switching element 8
When the conduction between the collector 8c and the emitter 8e is cut off when the gate potential drops, the second switching element 14 is turned on and the collector 8c to the emitter of the first switching element 8 is turned on when the second switching element 14 is turned on. It is non-conductive during 8e. Therefore, the discharge current of the discharge tube 1 is cut off, and the generation of discharge is stopped. The application of the light emission stop signal Vb to the second switching element 14 is removed after the discharge tube 1 is extinguished.

The zener diode 13 clamps the voltage between the emitter 8e and the gate electrode 8g of the first switching element 8,
Although there is a function to prevent the gate electrode 8g from being destroyed, it is not necessary if the breakdown voltage of the gate electrode 8g of the first switching element 8 is equal to or lower than the charging voltage of the main capacitor 3.

In the case of a gate-insulated switching element,
Since only the voltage is applied to the gate and the current is turned on without the current flowing, the bias capacitor 11 only needs to apply the voltage to the gate of the first switching element 8 during the discharge of the discharge tube 1. The capacity can be very small.

FIG. 3 is a control circuit of a dimming strobe according to a second embodiment of the present invention. The control circuit according to the second embodiment is obtained by adding a voltage doubler circuit and a speed-up capacitor 19 to the control circuit according to the first embodiment, and other configurations are completely the same as those according to the first embodiment. It is configured similarly.
Therefore, the same components are denoted by the same reference numerals, and description thereof will be omitted.

That is, the voltage doubler circuit has one end connected to the connection point between the resistor 4 and the thyristor 5 and the other end connected to the cathode of the discharge tube 1 for light emission.
It comprises a voltage doubler capacitor 16 connected to 1k, a resistor 17 connected between the cathode 1k and the ground, and a speedup capacitor 19 is connected in parallel to the resistor 12.

When the thyristor 5 is turned on, the voltage doubler capacitor 16 applies a voltage approximately twice the charged voltage of the main capacitor 3 to both ends of the discharge tube 1,
The purpose of this is to make it easier to discharge even if the charging pressure is low.

In the circuit of the second embodiment, when the thyristor 5 is turned off, the trigger capacitor 6 and the doubler capacitor 16 are charged with the same voltage as the charged voltage of the main capacitor 3, respectively.

When a light emission start signal is applied to the input terminal 9 in this state, the thyristor 5 is turned on, and a high-voltage pulse for excitation is applied to the trigger electrode 1t of the discharge tube 1 and the cathode of the discharge tube 1
Reduce 1k to minus potential. When the discharge tube 1 is excited in this way, a conduction state is established between the anode 1a and the cathode 1k of the discharge tube 1. When the discharge tube 1 conducts, the cathode 1k instantaneously changes from a negative potential to a positive potential, and the current flowing through the discharge tube 1 charges the bias capacitor 11.
Thereafter, the operation from turning on to turning off of the first switching element 8 is as described in the circuit of the first embodiment.

The speed-up capacitor 19 delays the rise of the gate voltage of the switching element 8 due to the time constant circuit of the resistor 12 and the capacitance between the emitter 8 e and the gate electrode 8 g of the first switching element 8. This is to prevent delay of turn-on, and a capacitor having a very small value is used.

In the circuit of the second embodiment, a diode 18 is connected between the cathode 1k of the discharge tube 1 and the collector 8c of the first switching element 8.
When is turned on, the collector 8c of the switching element 8 becomes the same potential when the cathode 1k of the discharge tube 1 is pulled to a negative potential due to the charged voltage of the voltage doubler capacitor 16,
Some elements are inserted in order to prevent the element 8 from being destroyed, but this is not necessary if the breakdown voltage of the collector 8c of the element 8 is sufficiently large.

FIG. 4 is a timing chart showing a case where a pulse signal is repeatedly applied to the other input terminal 15 in the control circuit of the second embodiment of FIG. 3 to cause continuous light emission by a so-called intermittent operation. .

This is because, at the start of light emission, an operation in which a light emission start signal Va is applied to one input terminal 9 and light emission of the discharge tube 1 is started,
As described above. Further, when the light emission is interrupted, the current of the light emission stop signal Vb is applied to the input terminal 15 to turn on the second switching element 14 to lower the gate potential of the first switching element 8, turn off the element 8, and discharge. Interrupt. However, when the first switching element 8 is turned off,
, The collector potential Vc rises, whereby the bias capacitor 11 is charged again. Since the discharge tube 1 is in an active state even when the current is cut off, while in this active state,
The voltage applied to the other input terminal 15 is returned to "L" again to turn off the second switching element 14. Then, the gate potential Vg of the first switching element 8 rises again by the charging voltage of the bias capacitor 11, and the switching element 8
Is turned on, and the discharge of the discharge tube 1 is restarted.

Even when the discharge is intermittently repeated in such a short period, continuous strobe light emission can be performed only by applying a repetition pulse Vb as shown in FIG.

In the control circuit of the embodiment described above, the current limiting resistor, the shunt resistor between the cathode and the gate of the thyristor, the shunt resistor between the emitter and the base of the capacitor and the transistor, and the like are omitted for the sake of simplicity. I have.

As described above, according to the present invention, in a strobe control circuit using a self-extinguishing type gate controlled switching element such as an IGBT, a bias voltage of the switching element is obtained by using an excitation current of a light emitting discharge tube. Because it was
Like this kind of conventional control circuit mentioned at the beginning of the specification,
There is no need to provide a power supply for biasing the gate electrode of the switching element separately from the booster circuit, and a rectifying diode for the bias power supply, a large-capacity capacitor for smoothing, a constant voltage element, and the like. No longer needed
Further, the bias voltage is applied to the date electrode only when the discharge tube is triggered, so that a voltage is applied from the bias power supply to the gate electrode as in the related art.
A gate circuit including a plurality of transistors is not required.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a simple dimming circuit that does not require a complicated gate driving power supply circuit and has a small number of components.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of a control circuit of a dimmable strobe showing a first embodiment of the present invention, FIG. 2 is a time chart of the control circuit of the first embodiment, and FIG. FIG. 4 is an electric circuit diagram of a control circuit of a dimmable strobe showing a second embodiment of the present invention. FIG. 4 is a time chart at the time of continuous stroboscopic light emission in the control circuit of the second embodiment. FIG. FIG. 2 is an electric circuit diagram illustrating an example of a control circuit of the strobe light. DESCRIPTION OF SYMBOLS 1 ... Discharge tube for light emission 1t ... Trigger electrode 2 ... Booster circuit for power supply 3 ... Main capacitor trigger means 5 ... Thyristor trigger means 6 ... Trigger capacitor trigger means 7 ... Trigger transformer 8 ... Gate control type First switching element 8g Gate electrode 10 Diode 11 Bias capacitor 14 Second switching element

Claims (4)

(57) [Claims] 1. A booster circuit including a power supply, a main capacitor charged by the booster circuit, a discharge tube for light emission, and a gate control type connected in series in a discharge path including the discharge tube for light emission of the main capacitor. A strobe device having a switching element, in response to a light emission start signal, applying a starting voltage to a trigger electrode of the discharge tube to excite the discharge tube to a conductive state; A series circuit of a diode and a bias capacitor connected in parallel with the element; and the first capacitor charges the charge by using the bias capacitor charged by the discharge current of the discharge tube in an excited and conductive state. A voltage is applied to the gate electrode of the switching element, the switching element is turned on, and the gate is turned on in response to the emission stop signal. A gate electrode control means including a second switching element for stopping voltage application to the pole and returning the first switching element to a non-conducting state. Control circuit. 2. A booster circuit including a power supply, a main capacitor charged by the booster circuit, a discharge tube for light emission, and a gate control type connected in series in a discharge path including the discharge tube for light emission of the main capacitor. A strobe device having a first switching element, wherein in response to a light emission start signal, a trigger voltage is applied to a trigger electrode of the discharge tube to excite the discharge tube to a conductive state; A constant voltage generating element connected to the gate terminal of the first switching element; a second switching element connected between the gate terminal and the emitter terminal of the gate-controlled first switching element; The first voltage is applied to the gate terminal by applying a constant voltage generated in the constant voltage generating element based on the charging voltage from the main capacitor. A strobe device, comprising: a gate electrode control unit that turns on the switching element and turns off the first switching element by turning on the second switching element in response to the light emission stop signal. 3. The strobe device according to claim 2, wherein a capacitor is provided in parallel with the first switching element, and the constant voltage generating element generates a constant voltage using a charge of the capacitor as a power supply. 4. The strobe device according to claim 3, wherein the capacitor is charged by a discharge current of the discharge tube.