JP3889145B2 - Flash device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flash device used as an artificial light source at the time of taking a photograph, and more particularly to a flash device capable of performing a high-speed repeated light emission operation.
[0002]
[Prior art]
Flash devices are often used as artificial light sources for illuminating a subject when taking a picture. Some flash devices can select an operation mode in which a light emission operation is repeated at high speed, that is, a so-called flat light emission operation mode.
[0003]
FIG. 3 is an electric circuit diagram of a main part of the flash device capable of selecting the flat light emission operation mode.
[0004]
The flash device of FIG. 3 includes a DC high-voltage power supply 101 composed of, for example, a DC low-voltage power supply that is a battery and a DC / DC converter circuit, a main capacitor 102 connected to both ends of the DC high-voltage power supply 101, and a main capacitor 102. A control element that controls the light emission operation that consumes the charge of the coils 103, 104, the flash tube 105, and the main capacitor 102 of the flash tube 105 connected to both ends of the flash tube 105, for example, an insulated gate type A bipolar transistor (hereinafter referred to as IGBT) 106 is provided in series.
[0005]
The flash device is a self-holding switch element connected in the forward direction to both ends of the coil 104, for example, a thyristor 107, transistors 108 and 109 for controlling the on / off operation of the thyristor 107, and on / off of the transistor 109. , A resistor 112, a capacitor 112 connected in parallel to the resistor 111, a trigger circuit 114 for exciting the flash tube 105, a light emission control circuit 115 for controlling the operation of the IGBT 106, and a coil 103. , 104 and the flash tube 105, and a diode 116 connected in the reverse direction.
[0006]
The coils 103 and 104 and the thyristor 107 control the rising characteristics of the discharge current that flows when the charge of the main capacitor 102 is discharged through the flash tube 105, thereby controlling the rising characteristics of the light emitted from the flash tube 105. Is provided to do.
[0007]
Specifically, due to the on / off operation of the thyristor 107, the discharge path of the charged charge of the main capacitor 102 through the flash tube 105 is inserted into both the first discharge path in which only the coil 103 is inserted and the coils 103 and 104. The second discharge path having a different impedance value from the first discharge path is selected.
[0008]
As a result, the light emission operation mode of the flash tube 105 is changed to, for example, a normal light emission operation mode having a rising characteristic with a steep light emission waveform, a continuous light emission operation mode by a high-speed repetition of a light emission operation having a gentle rise characteristic, a so-called flat light emission operation mode. Can be selectively controlled.
[0009]
In the flash device configured as described above, when the normal light emission operation mode is set, first, the transistor 109 is turned on by an output signal (control signal) from the control circuit 113. As a result, an on-voltage is supplied to the gate which is the control electrode of the thyristor 107 via the transistor 108, the resistor 110, etc., and the thyristor 107 is turned on.
[0010]
In this state, when the flash tube 105 is excited by the operation of the trigger circuit 114 and the IGBT 106 which is the control element is turned on by the light emission control circuit 115, the charged charge of the main capacitor 102 causes the coil 103, the thyristor 107 and the IGBT 106 to be charged. To the flash tube 105. That is, the first discharge path not through the coil 104 is selected as the discharge path of the main capacitor 102, and the flash tube 105 consumes the charge of the main capacitor 102 discharged through the first discharge path, and emits light. As a result, the light emission waveform of the flash tube 105 has a steep rise characteristic.
[0011]
On the other hand, when the flat light emission operation mode is set, the supply of the output signal from the control circuit 113 is stopped and the transistor 109 is turned off, so that the ON voltage cannot be supplied to the gate which is the control electrode of the thyristor 107 and the thyristor 107 is kept off. To do.
[0012]
In this state, when the flash tube 105 is excited and the IGBT 106 which is a control element is turned on, the charged charge of the main capacitor 102 is different from that in the normal light emission operation, without passing through the thyristor 107, the coil 103, The flash tube 105 is discharged through 104 and the IGBT 106. That is, the second discharge path through both the coils 103 and 104 is selected as the discharge path of the main capacitor 102, and the flash tube 105 consumes the charge of the main capacitor 102 discharged through the second discharge path. As a result, the light emission waveform of the flash tube 105 has a gradual rise characteristic.
[0013]
[Problems to be solved by the invention]
As described above, in the flash device shown in FIG. 3, the on / off operation of the thyristor 107, which is a self-holding switch element, is controlled according to the set light emission operation mode of the flash tube 105, and the discharge path of the main capacitor 102 is selected. Thus, the light emission waveform of the flash tube 105 is controlled.
[0014]
However, in the flat light emission operation mode setting in which the thyristor 107 is maintained in the OFF state and the charge of the main capacitor 102 is discharged to the flash tube 105 through the second discharge path, the flat light emission operation cycle is the flash tube 105. Is the end process of the previous light emission operation, and in the period when the next light emission operation is started when the internal sealing gas is still in an ionized state while no light is emitted, the control element in the second and subsequent light emission operations There is a risk that the thyristor 107 malfunctions due to the voltage induced in the coils 103 and 104 when the IGBT 106 is turned on, and is turned on.
[0015]
That is, in the flat light emission operation in the above cycle, first, since the energy has not been accumulated in the coils 103 and 104 until the first light emission operation, the cathode to anode of the thyristor 107 and the cathode to anode of the thyristor 107 associated with the on / off operation of the IGBT 106 are obtained. The potential fluctuation generated between the gates does not become a large potential fluctuation but a desired normal light emission operation.
[0016]
Next, when the IGBT 106 is turned on for the second light emission operation, the cathode potential of the thyristor 107 is suddenly lowered to the ground level due to the IGBT 106 being turned on. The back electromotive force induced in the coil 103 when the IGBT 106 for turning off the initial light emission operation is applied, and the back electromotive force generated in the coil 104 due to the rapid energy supply from the main capacitor 102 are applied. Become.
[0017]
As a result, the potential between the cathode and the anode of the thyristor 107 and the potential between the cathode and the gate rise. When the potential fluctuation between the cathode and the gate reaches or exceeds the ON voltage Vg of the thyristor 107, the thyristor 107 is controlled by the control circuit 113. Even though the normal on control based on the on operation is not performed, the device malfunctions and turns on.
[0018]
The thyristor 107 that is turned on due to malfunctioning is in an ionization state when the light emission operation cycle is such that the next light emission operation is started when the flash tube 105 does not emit light but the internal gas is still ionized. Since the current flows through the flash tube 105, the ON state is maintained thereafter.
[0019]
Therefore, when the thyristor 107 malfunctions and is turned on, the charge of the main capacitor 102 is discharged to the flash tube 105 through the first discharge path not passing through the coil 104, and the emission waveform of the flash tube 105 is flattened. It becomes impossible to realize a stable flat light emission operation of a light emission waveform having desired characteristics to be set in the light emission operation mode, that is, a gradual rise characteristic due to the discharge of the charged charge through the second discharge path.
[0020]
In addition, when the thyristor 107 is turned on due to a malfunction in the flat light emission operation mode, a discharge current repeatedly flows to the IGBT 106 serving as a control element with a steep rise characteristic, and in some cases, the IGBT 106 may be damaged.
[0021]
Accordingly, the present invention provides a self-holding switch element for selecting a discharge path in a flash device that selects a discharge path for charge of a main capacitor having different impedance values in a normal light emission operation mode and a flat light emission operation mode. It is an object of the present invention to provide a flash device capable of preventing a malfunction of the light source and performing a stable light emitting operation.
[0022]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, a main capacitor, a flash tube, and a high potential side electrode connected to the main capacitor and a low potential side electrode are provided between the main capacitor and the flash tube. A first discharge path having a self-holding switch element connected to the flash tube; a second discharge path provided in parallel with the first discharge path and having an impedance value different from that of the first discharge path; In a flash device having a control circuit for turning on or off a self-holding switch element to select a first or second discharge path and discharging a charge stored in a main capacitor via the selected discharge path. When the circuit selects the first discharge path, the control signal from the control circuit is applied to the control electrode of the self-holding switch element to turn on the self-holding switch element. It is provided with a bias circuit for reverse biasing the control electrodes of the self-holding switching element when the second discharge path is selected.
[0023]
Then, the bias circuit, a first resistor connected between the control electrode and the low-potential-side electrode of the self-holding switching element, a control electrode of the self-holding switching element connected in series to the first resistor the main capacitor is constituted by a second resistor connected between the low potential side terminal.
[0024]
Further, it is desirable to connect a capacitor in parallel with the first resistor. As a result, the capacitor is connected between the control electrode (gate) and the cathode of the self-holding switch element, and the self-holding switch element of the self-holding switch element is turned on when a control element such as an IGBT that emits light for the second and subsequent times. It is possible to suppress a rise in the potential of the gate as viewed from the cathode, and to more effectively prevent the self-holding switch element from malfunctioning.
[0028]
According to the present invention, in the flat light emission operation mode in which the discharge is performed by the discharge loop through the second discharge path, the ON operation due to the malfunction of the self-holding switch element on the first discharge path side is prevented, and the stable flat A light emitting operation can be obtained.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
A flash device according to an embodiment of the present invention will be described below with reference to FIG. FIG. 1 is an electric circuit diagram of the main part of the flash device.
[0030]
This flash device includes, for example, a DC high-voltage power supply 1 composed of a DC low-voltage power supply that is a battery and a DC / DC converter circuit, a main capacitor 2 connected to both ends of the DC high-voltage power supply 1, and both ends of the main capacitor 2. For example, an insulated gate bipolar transistor that is a control element for controlling the light emission operation that consumes the charge of the coils 3 and 4 and the flash tube 5 and the main capacitor 2 of the flash tube 5 that are connected to the (Hereinafter referred to as IGBT) 6 and a serial body.
[0031]
In addition, the flash device controls a thyristor 7 which is a self-holding switch element connected in the forward direction to both ends of the coil 4, transistors 8 and 9 for controlling the on / off operation of the thyristor 7, and on / off of the transistor 9. A control circuit 13, a resistor 10, 11, a capacitor 12 connected in parallel to the resistor (first resistor) 11, a trigger circuit 14 for exciting the flash tube 5, and a light emission control circuit 15 for controlling the operation of the IGBT 6. And a diode 16 connected in a reverse direction to a series body of the coils 3 and 4 and the flash tube 5.
[0032]
The coils 3 and 4 and the thyristor 7 control the rising characteristics of the discharge current that flows during the discharge of the charge of the main capacitor 2 through the flash tube 5 to control the rising characteristics of the light emitted from the flash tube 5. Is provided to do.
[0033]
Specifically, due to the on / off operation of the thyristor 7, the discharge path of the charge of the main capacitor 2 through the flash tube 5 is inserted into both the first discharge path in which only the coil 3 is inserted and the coils 3 and 4. The second discharge path having a different impedance value from the first discharge path is selected.
[0034]
As a result, the light emission operation mode of the flash tube 5 is changed to, for example, a normal light emission operation mode having a rising characteristic with a steep emission waveform, a continuous light emission operation mode by a high-speed repetition of a light emission operation having a gentle rise characteristic, a so-called flat light emission operation mode. Can be selectively controlled.
[0035]
In the flash device of this embodiment, a resistor (second resistor) 18 connected in series to the resistor 11 and connected between the control electrode of the thyristor 7 and the low potential side (ground side) terminal of the main capacitor 2. Is provided.
[0036]
The resistor 11 and the resistor 18 constitute a bias circuit 17, which corresponds to the bias circuit referred to in the claims. The resistor 18 corresponds to the reverse bias means described in the claims.
[0037]
Therefore, between the cathode and gate of the thyristor 7, the voltage generated at both ends of the resistor 11 among the voltages obtained by dividing the charging voltage of the main capacitor 2 shown in the figure by the coils 3, 4 and the bias circuit 17 is always applied. become.
[0038]
The application direction of the voltage generated at both ends of the resistor 11 is a direction in which the cathode potential is raised with respect to the gate potential. For this reason, the gate of the thyristor 7 is reverse-biased.
[0039]
The operation of the flash device configured as described above will be described first when the normal light emission operation mode is set.
[0040]
The transistor 9 is turned on by an output signal (control signal) from the control circuit 13. As a result, an on-voltage is supplied to the gate which is the control electrode of the thyristor 7 via the transistor 8, the resistor 10, etc., and the thyristor 7 is turned on.
[0041]
In this state, when the flash tube 5 is excited by the operation of the trigger circuit 14 and the IGBT 6 as the control element is turned on by the light emission control circuit 15, the charge of the main capacitor 2 is charged to the coil 3, the thyristor 7 and the IGBT 6. To the flash tube 5. That is, the first discharge path not through the coil 4 is selected as the discharge path of the main capacitor 2, and the flash tube 5 consumes the charge of the main capacitor 2 discharged through the first discharge path to emit light, As a result, the light emission waveform of the flash tube 5 has a steep rise characteristic.
[0042]
Next, the operation at the time of setting the flat light emission operation mode in such a cycle that the next light emission operation is started when the gas enclosed in the flash tube 5 is in an ionized state will be described.
[0043]
The potential between the cathode and gate of the thyristor 7 in this embodiment is the potential state between the cathode and gate of the thyristor 107 in the conventional flash device shown in FIG. In contrast, the potential is controlled to reverse bias the gate.
[0044]
Thus, when the gate of the thyristor 7 is reverse-biased and the thyristor 7 is turned off, the flash tube 5 is excited and the IGBT 6 as the control element is turned on, the charge of the main capacitor 2 is Unlike the normal light emitting operation, the light is discharged to the flash tube 5 through the coils 3 and 4 and the IGBT 6 without passing through the thyristor 7. That is, the second discharge path through both the coils 3 and 4 is selected as the discharge path of the main capacitor 2, and the flash tube 5 consumes the charge of the main capacitor 2 discharged through the second discharge path. As a result, the light emission waveform of the flash tube 5 has a gradual rise characteristic. Thus, the first light emission is performed first.
[0045]
When the IGBT 6 is turned on for the second and subsequent light emission operations, the reverse is induced in the coil 3 when the IGBT 6 is turned off at the end of the first light emission operation or the previous light emission operation due to a rapid decrease in the cathode potential of the thyristor 7 to the ground level. The electromotive force and the counter electromotive force generated in the coil 4 are applied to the thyristor 7, and the potential of the thyristor 7 between the cathode and the anode and between the cathode and the gate rises and varies.
[0046]
However, in this embodiment, the rising fluctuation of the potential between the cathode and the gate of the thyristor 7 is a fluctuation from a state in which the gate of the thyristor 7 is reverse-biased by the bias circuit 17, and thus the rising fluctuation value is the value of the thyristor 7. It does not reach the on-voltage Vg.
[0047]
In addition, since the capacitor 12 is connected between the gate and the cathode of the thyristor 7 so as to be in parallel with the resistor 11, an increase in the potential of the gate seen from the cathode of the thyristor 7 is suppressed when the IGBT 6 is turned on for the second time and thereafter. that.
Therefore, the thyristor 7 does not cause a malfunction that is turned on by the induced voltage of the coils 3 and 4 to be applied when the IGBT 6 is turned on.
[0048]
Since the thyristor 7 does not turn on due to a malfunction as described above, the potential fluctuation between the cathode and the anode of the thyristor 7 gradually decreases until the IGBT 6 is turned off after the rising fluctuation, and further to the coil 4 when the IGBT 6 is turned off. It shows a characteristic that fluctuates in the reverse direction greatly by application of the induced back electromotive force.
[0049]
The potential between the cathode and the gate of the thyristor 7 also stops rising due to the falling potential variation between the cathode and the anode of the thyristor 7 because the thyristor 7 does not turn on due to a malfunction, and then gradually decreases.
[0050]
As a result, in the flash device of this embodiment, during the flat light emission operation with the thyristor 7 kept in the off state, the charge of the main capacitor 2 is always transmitted through the second discharge path in which both the coils 3 and 4 are inserted. As a result, the flash tube 5 is discharged. Therefore, a stable flat light emission operation can be obtained.
[0051]
In the above embodiment, the charge of the main capacitor 2 is discharged through only the coil 3 during the normal light emission operation, and the charge of the main capacitor 2 is discharged through the plurality of coils 3 and 4 during the flat light emission operation. In the present invention, as shown in FIG. 2, in the normal light emission operation, the charge of the main capacitor 2 is discharged without passing through the coil, and in the flat light emission operation, the main capacitor 2 is charged only through the coil 4. The present invention can also be applied when discharging electric charges.
[0052]
【The invention's effect】
As described above, according to the present invention, the self-holding switch element malfunctions during the flat light emission operation when the self-holding switch element for selecting the discharge path of the main capacitor is controlled to be in the off state. Therefore, it is possible to realize a flash device capable of performing a stable flat light emission operation in which the rising characteristic at each light emission has a gentle light emission waveform.
[0053]
In addition, the rise characteristic at each light emission can be controlled to a gentle light emission waveform, and the discharge current with the steep rise characteristic can be prevented from flowing repeatedly during flat light emission operation, so that the control element that controls the light emission operation of the flash tube is damaged. Can also be avoided.
[Brief description of the drawings]
FIG. 1 is a main part electric circuit diagram of a flash device according to an embodiment of the present invention.
FIG. 2 is a main part electric circuit diagram of a modification of the embodiment.
FIG. 3 is a main part electric circuit diagram of a conventional flash device;
[Explanation of symbols]
1 DC high voltage power supply 2 Main capacitor 3, 4 Coil 5 Flash tube 6 Insulated gate bipolar transistor (IGBT)
7 Thyristor (self-holding switch element)
8, 9 Transistors 10, 11, 18 Resistor 12 Capacitor 13 Control circuit 14 Trigger circuit 15 Light emission control circuit 16 Diode 17 Bias circuit

Claims (2)

A main capacitor, a flash tube, and a self-holding switch provided between the main capacitor and the flash tube, the high potential side electrode being connected to the main capacitor and the low potential side electrode being connected to the flash tube A first discharge path having an element; a second discharge path provided in parallel with the first discharge path and having an impedance value different from the first discharge path; and A flash device having a control circuit for turning off and selecting the first or second discharge path and discharging the charge accumulated in the main capacitor through the selected discharge path;
When the first discharge path is selected, a control signal from the control circuit is applied to the control electrode of the self-holding switch element to turn on the self-holding switch element, and the second discharge path is selected. Providing a bias circuit for reverse-biasing the control electrode of the self-holding switch element when
A first resistor connected between a control electrode of the self-holding switch element and a low potential side electrode; and a control electrode of the self-holding switch element connected in series to the first resistor; A flash device comprising: a second resistor connected between a low potential side terminal of the main capacitor.   The flash device according to claim 1, wherein a capacitor is connected in parallel to the first resistor.

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