JP2008089797A - Permission signal generation circuit and power source circuit for flash light discharge tube using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a permission signal generation circuit capable of stably controlling the permission of light emission with simple circuit constitution. <P>SOLUTION: The permission signal generation circuit 3 includes: a first comparator 14 outputting a first comparison signal V<SB>C1</SB>based on charge voltage and reference voltage of a discharge capacitor 9; a second comparator 15 outputting a second comparison signal V<SB>C2</SB>for controlling the on/off of the charge of the discharge capacitor 9 based on the charge voltage and reference voltage higher than that of the first comparator 14; and a detection circuit 16 having a bipolar transistor 17 turned on/off in accordance with the first comparison signal V<SB>C1</SB>and a thyristor 18 connected to the bipolar transistor 17 in series and turned on in accordance with the second comparison signal V<SB>C2</SB>and turned off in accordance with the transition of the bipolar transistor 17 to an off-state, and detecting that both the bipolar transistor 17 and the thyristor 18 are in an on-state and outputting it as a permission signal S<SB>3</SB>. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a permission signal generation circuit for allowing light emission of a flash discharge tube such as a xenon flash lamp, and a power supply circuit for a flash discharge tube using the permission signal generation circuit.

  Flash discharge tubes, typified by xenon flash lamps, are characterized by the ability to instantaneously obtain high-power white light, so they are widely used for light sources for spectroscopic analysis, camera flash lamps, strobe light sources, high-speed shutter camera lamps, etc. It has been broken. The flash discharge tube power supply circuit has a built-in capacitor for light emission from the flash discharge tube, and charges are supplied from the capacitor to the flash discharge tube when the flash discharge tube emits light.

Conventionally, such a power supply circuit has a function of allowing light emission by detecting the charge state of a built-in capacitor in order to cause the flash discharge tube to emit light stably. For example, Patent Documents 1 and 2 listed below disclose a power supply circuit having a function of allowing a shutter release by monitoring an elapsed time from a charging period and generating a charging completion signal. Patent Documents 3 and 4 listed below disclose a power supply circuit for a camera that outputs a charge completion signal according to whether a charging voltage of a capacitor is equal to or higher than a predetermined voltage.
Japanese Patent Laid-Open No. 6-4002 Japanese Patent Laid-Open No. 2-99933 JP-A 63-130742 Japanese Patent Laid-Open No. 7-20543

  By the way, when the charging completion signal is generated by monitoring the elapsed time from the charging period as described in Patent Documents 1 and 2, since the capacitor may vary in characteristics, the charge state detection accuracy is improved. There is a limit.

  On the other hand, when detecting the charging voltage of a capacitor as described in Patent Documents 3 and 4, digital processing using a microcomputer or the like is used to generate a charging completion signal. For this reason, when used for a high-power flash discharge tube, it is difficult to stably control emission permission due to the influence of discharge noise.

  Therefore, the present invention has been made in view of such problems, and an object of the present invention is to provide a permission signal generation circuit and a flash discharge tube power supply circuit capable of stable light emission permission control with a simple circuit configuration. .

  In order to solve the above-mentioned problem, the permission signal generation circuit of the present invention detects a charging voltage of a discharge capacitor for light emission of the flash discharge tube, thereby generating a permission signal for permitting the external device to emit light from the flash discharge tube. A permission signal generation circuit for generating a first comparator that receives a voltage signal corresponding to a charging voltage of the discharge capacitor and outputs a first comparison signal according to a comparison result between the charging voltage and the first reference voltage; A voltage signal corresponding to the charging voltage of the discharge capacitor is inputted, and a second signal for controlling on / off of charging of the discharging capacitor is controlled according to a comparison result between the charging voltage and a second reference voltage higher than the first reference voltage. A second comparator that outputs two comparison signals; a first semiconductor element that is turned on / off in response to the first comparison signal; and a first semiconductor element that is connected in series to the first semiconductor element, and that corresponds to the second comparison signal. A second semiconductor element that turns on and turns off in response to the transition of the first semiconductor element to the off state, detects that both the first and second semiconductor elements are in the on state, and receives a permission signal As a detection circuit.

  According to such a permission signal generation circuit, a decrease in the charging voltage due to natural discharge or the like is detected by the second comparison signal obtained by comparing the charging voltage of the discharge capacitor and the second reference voltage, and the discharging is performed by the second comparison signal. Capacitor charging on / off is controlled. On the other hand, in the detection circuit, when the charging voltage reaches the second reference voltage after starting the charging of the discharging capacitor, the first and second semiconductor elements are turned on, and the charging voltage is discharged by the subsequent discharging. When the voltage drops below the first reference voltage lower than the second reference voltage, the first and second semiconductor elements are turned off simultaneously. Then, a permission signal for permitting light emission is output from the detection circuit to the external device when both the first and second semiconductor elements are in the on state. Therefore, with a simple circuit configuration, it is possible to output a stable light emission permission signal in accordance with the state of charge of the discharge capacitor while keeping the charge voltage of the discharge capacitor stable near the reference voltage.

  The detection circuit includes a transistor whose base is connected to the output of the first comparator, a gate which is connected to the output of the second comparator, a cathode which is connected to the collector of the transistor, and an anode which is a terminal for outputting a permission signal. It is preferable to have a thyristor connected.

  In this case, since the permission signal is output from the end of the series circuit including the transistor and the thyristor, the circuit configuration of the detection circuit is further simplified, and the influence of discharge noise is reduced.

  The detection circuit includes a transistor having a base connected to the output of the first comparator, a collector connected to the output signal output terminal, a gate connected to the output of the second comparator, and an anode connected to the output of the transistor. It is also preferred to have a thyristor connected to the emitter.

  In this case, since the permission signal is output from the end of the series circuit including the transistor and the thyristor, the circuit configuration of the detection circuit is further simplified, and the influence of discharge noise is reduced.

  Furthermore, the second comparator is preferably a hysteresis comparator having hysteresis characteristics. With such a configuration, stability during charge control of the discharge capacitor is improved.

  Alternatively, a power supply circuit for a flash discharge tube according to the present invention includes a permission signal generation circuit described above, a power supply circuit that includes a discharge capacitor and supplies electric charge to the flash discharge tube, and a signal corresponding to the second comparison signal from the permission signal generation circuit. Is inputted, and a light emission trigger is applied to the flash discharge tube according to a light emission trigger control signal inputted from an external device, and a charge control circuit for controlling on / off of charging of the discharge capacitor in the power supply circuit according to the second comparison signal And a light emission trigger generating circuit for discharging the electric charge accumulated in the discharge capacitor.

  In such a flash discharge tube power supply circuit, the charge control circuit performs on / off control of charging of the discharge capacitor in the power supply circuit in accordance with the second comparison signal generated by the permission signal generation circuit. Thereby, the charging voltage of the discharge capacitor is stably maintained at the reference voltage. When a permission signal is output from the permission signal generation circuit to the external device, a light emission trigger control signal is input from the external device to the light emission trigger generation circuit, and a light emission trigger is applied to the flash discharge tube by the light emission trigger generation circuit. As a result, the flash discharge tube emits light. Therefore, stable emission control can be performed with a simple circuit configuration.

  According to the permission signal generation circuit of the present invention, it is possible to control light emission permission stably with a simple circuit configuration.

  Hereinafter, preferred embodiments of a permission signal generation circuit and a flash discharge tube power supply circuit according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a circuit block diagram of a power supply circuit 1 for a flash discharge tube which is a preferred embodiment of the present invention. A flash discharge tube power supply circuit 1 is a circuit that generates an applied voltage for causing a flash discharge tube such as a xenon flash lamp to emit light. The power supply circuit 2, the permission signal generation circuit 3, the charge control circuit 4, and the light emission trigger generation circuit. 5.

  The power supply circuit 2 includes a capacitor 7 having both ends connected to an external DC power supply 6, a transformer 8 including a primary coil 8 a connected in parallel to the capacitor 7, and a secondary coil 8 b of the transformer 8. A discharge capacitor 9 for light emission from the flash discharge tube L connected to both ends of the first and second MOSFETs 10 and a MOS FET 10 connected in series to the primary coil 8a.

More specifically, one end of the primary side coil 8a of the transformer 8 is connected to the positive electrode of the DC power supply 6, the other end of the primary side coil 8a is connected to the drain of the FET 10, and the source of the FET 10 has a resistance the negative electrode of the DC power source 6 through the element R ₁ is connected. Further, the gate of the FET 10, the charge control circuit 4, which will be described later, via a resistor R ₂ is connected. One end of the discharge capacitor 9 is connected to one end of the secondary coil 8b via the rectifying diode 11, and the other end of the discharge capacitor 9 is connected to the other end of the secondary coil 8b. Both ends of the capacitor 9 are connected to the anode and the cathode of the flash discharge tube L via the connector 12 and the socket 13, respectively.

In the power supply circuit 2 of the above configuration, by the pulse current is applied to the primary coil 8a of the transformer 8 according to the input of the pulse signals S ₁ from the charging control circuit 4, from the secondary side coil 8b The discharge capacitor 9 is charged by supplying a pulse current corresponding to the turn ratio between the primary side and the secondary side to the discharge capacitor 9. When a light emission trigger TR is applied to the flash discharge tube L from the light emission trigger generation circuit 5 (details will be described later) in a state where the discharge capacitor 9 is charged, a discharge accompanied by light emission starts in the flash discharge tube L. A discharge current flows from the discharge capacitor 9 to the flash discharge tube L.

  Next, the configuration of the permission signal generation circuit 3 will be described. The permission signal generation circuit 3 detects the charging voltage of the discharge capacitor 9 in the power supply circuit 2 and permits the external device 21 connected to the flash discharge tube power circuit 1 to emit light from the flash discharge tube L. Is a circuit that generates

The permission signal generation circuit 3 is configured according to the outputs of the first comparator 14 and the second comparator 15 to which a voltage corresponding to the charging voltage of the discharge capacitor 9 is input, and the outputs of the first and second comparators 14 and 15. And a detection circuit 16 for outputting a charging voltage detection signal S ₂ for controlling the charging of the discharge capacitor 9 and an enabling signal S ₃ for permitting the flash discharge tube L to emit light.

The first and second comparators 14 and 15 are supplied with the charging voltage of the discharge capacitor 9 divided by the series circuit constituted by the resistance elements R ₃ , R ₄ and R ₅ and a variable reference voltage. V _R is input. The first and second comparators 14 and 15 are so-called open collector output comparators. The first comparator 14 compares the reference voltage V _R with the voltage V _A × (R ₄ + R ₅ ) / (R ₃ + R ₄ + R ₅ ), where V _A is the charging voltage of the discharge capacitor 9. A first comparison signal V _C1 corresponding to the comparison result is output. As a result, the first comparator 14 has a high-level first comparison signal V _C1 when the charging voltage V _A is equal to or higher than the reference voltage V _R × (R ₃ + R ₄ + R ₅ ) / (R ₄ + R ₅ ). When the charging voltage V _A is smaller than the reference voltage V _R × (R ₃ + R ₄ + R ₅ ) / (R ₄ + R ₅ ), the low-level first comparison signal V _C1 is output.

Similarly, the second comparator 15 compares the reference voltage V _R with the voltage V _A × R ₅ / (R ₃ + R ₄ + R ₅ ), thereby obtaining the second comparison signal V _C2 according to the comparison result. Output. As a result, the second comparator 15 outputs the second comparison signal V _C2 having a high level when the charging voltage _VA is equal to or higher than the reference voltage V _R × (R ₃ + R ₄ + R ₅ ) / R _5. When the charging voltage V _A is smaller than the reference voltage V _R × (R ₃ + R ₄ + R ₅ ) / R ₅ , the low-level second comparison signal V _C2 is output. Therefore, the reference voltage for the charging voltage _VA of the second comparator 15 is larger than that of the first comparator 14. In the present embodiment, the reference voltage of the first comparator 14 is set to be about 5 to 10 percent lower than the reference voltage of the second comparator 15. The second comparator 15 is a hysteresis comparator having a hysteresis characteristic. When the second comparison signal V _C2 is at a high level, the charging voltage V _A of the discharge capacitor 9 decreases due to natural discharge, and a predetermined reference voltage is set. When the ratio is decreased (for example, about 1% of the reference voltage), the second comparison signal V _C2 is set to a low level. Second comparison signal V _C2 output from the second comparator 15 is inputted via the detection circuit 16 as a charging voltage detection signal S ₂ to the charge control circuit 4.

  The detection circuit 16 includes a bipolar transistor 17 and a thyristor 18 connected in series to the bipolar transistor 17, and has a function of detecting and outputting the switching state of the bipolar transistor 17 and the thyristor 18.

The anode of the thyristor 18 is biased to a positive potential through the resistor element R ₆ , the gate thereof is connected to the output of the second comparator 15 through the diode 19, and the cathode is connected to the collector of the bipolar transistor 17, gate - resistive element R ₈ is between the cathode is connected. Further, a pull-up resistor R ₇ is connected to the output of the second comparator 15.

The base of the bipolar transistor 17, the output of the first comparator 14 is connected through a resistor R _9, its emitter is connected to ground, the base - emitter between the resistance element R ₁₀ is connected. Furthermore, a pull-up resistor R ₁₁ is connected to the output of the first comparator 14.

The anode of the thyristor 18 of the detection circuit 16 is connected to the external device 21 through the terminals of the permission signal S ₃ output connector 20, is outputted as the anode potential is permission signal S ₃ of the thyristor 18 to the external device 21 .

In the detection circuit 16 configured as described above, the bipolar transistor 17 is turned on / off according to the high level / low level state of the first comparison signal V _C1 . Further, when the second comparison signal V _C2 transitions to a high level when the thyristor 18 is in the off state, the output transistor (not shown) of the second comparator 15 is turned off, so that the pull-up resistor R ₇ to the diode 19 As a result, a thyristor 18 is turned on. Here, after the thyristor 18 is once switched to the on state, the thyristor 18 remains on as long as the bipolar transistor 17 is in the on state even if the second comparison signal V _C2 transitions to the low level. That is, the thyristor 18 is turned off almost simultaneously with the bipolar transistor 17 in response to the transition of the first comparison signal V _{C1 to} the low level. Moreover, permission signals S ₃ output from the detection circuit 16 to the external device 21 becomes a low level when both of the bipolar transistors 17 and thyristor 18 is in the ON state, a high level otherwise.

The charge control circuit 4, corresponding to the charging voltage detection signal S ₂ input from the enable signal generating circuit 3 controls the charging of the on / off of the discharge capacitor 9 in the power supply circuit 2. Specifically, when the charging voltage detection signal S ₂ at the low level, i.e., if the second comparison signal V _C2 is at a low level, and supplies the pulse signals S ₁ to charge the discharge capacitor 9 to the power supply circuit 2 . Thereby, the charge control circuit 4 cooperates with the permission signal generation circuit 3 and the power supply circuit 2 so that the charging voltage of the discharge capacitor 9 before the flash discharge tube L emits light is within a predetermined range (for example, within 1%). Control to fit.

Light emission trigger generating circuit 5 in response to the light emission trigger control signal S ₄ that is input from the external device 21 when the permission signal S ₃ is at the low level, applies a light emission trigger TR to the flash discharge tube L. Specifically, the input of the light emission trigger generation circuit 5 is connected to the external device 21 via the connector 20, and the output of the light emission trigger generation circuit 5 is supplied to the trigger electrode of the flash discharge tube L via the connector 12 and the socket 13. It is connected.

Next, the operation of the flash discharge tube power supply circuit 1 will be described with reference to FIG. In FIG. 2, (a) is a timing chart of light emission trigger TR, (b) is a timing chart of the charging voltage of the discharge capacitor 9, (c) is a timing chart of the enable signal _{S 3.}

First, immediately after the flash discharge tube L emits light, the charging voltage of the discharge capacitor 9 decreases, and the first comparison signal V _C1 and the second comparison signal V _C2 are in a low level state (time T ₁ ). In such a state, the discharge capacitor 9 is charged under the control of the charge control circuit 4, and the charge voltage gradually rises. Thereafter, when the charging voltage reaches the reference voltage of the second comparator 15, a low level permission signal S ₃ is output from the detection circuit 16 to the external device 21, and the light emission control of the flash discharge tube L by the external device 21. Is permitted (time T ₂ ). Low level of permission signal S _3, the charging voltage of the discharge capacitor 9 is maintained until the drop in the reference voltage of the first comparator 14. In contrast, when the light emission trigger control signal S ₄ to the light emission trigger generating circuit 5 from the external device 21 is inputted, the light emission trigger TR is applied to the trigger electrode of the flash discharge tube L (time T _3). As a result, dielectric breakdown occurs between the anode and the cathode of the flash discharge tube L, and the electric charge stored in the discharge capacitor 9 is discharged in the flash discharge tube L. This discharge charged voltage of the discharge capacitor 9 drops instantaneously, the permission signal S ₃ transitions high state, light emission control by the external device 21 is prohibited. In the flash discharge tube power supply circuit 1, the operations from the light emission trigger input to the completion of charging as described above are repeated.

The operational effects of the flash discharge tube power supply circuit 1 described above will be described. Reduction of the charging voltage due to natural discharge or the like by the second comparison signal V _C2 charging voltage of the discharge capacitor 9 and the reference voltage of the second comparator 15 is compared is detected, discharging the capacitor 9 by the second comparison signal V _C2 ON / OFF of charging is controlled. On the other hand, in the detection circuit 16, when the charging voltage reaches the reference voltage of the second comparator 15 after the charging of the discharge capacitor 9 is started, the bipolar transistor 17 and the thyristor 18 are turned on, and thereafter When the charging voltage drops below the reference voltage of the first comparator 14 which is lower than the reference voltage of the second comparator 15 due to the discharging, the bipolar transistor 17 and the thyristor 18 are simultaneously turned off. Then, the external device 21 from the detection circuit 16, enabling signal S ₃ that allows light emission in the case both of the bipolar transistors 17 and thyristor 18 is turned on is outputted. Therefore, with a simple circuit configuration, it is possible to output a stable light emission permission signal according to the state of charge of the discharge capacitor 9 while keeping the charge voltage of the discharge capacitor 9 stable near the reference voltage. As a result, it is possible to prevent a shortage of light in the flash discharge tube L, poor light emission, and the like.

  In addition, by adopting the method of detecting the charging voltage of the discharge capacitor 9 and outputting the light emission permission signal in this way, the time loss between the light emission start time and the charge completion time is reduced, and the light emission amount is adjusted. Even when the discharge capacitor is switched or the charging voltage of the discharge capacitor is changed, it is possible to accurately detect the completion of charging and generate a light emission permission signal.

Also, grant signal generating circuit 3 because it has a structure enabling signal S ₃ is output from the end of the series circuit consisting of bipolar transistor 17 and the thyristor 18. The circuit configuration of the detection circuit is further simplified, The influence of discharge noise when the high-power flash discharge tube L is used is also reduced.

  Further, since the hysteresis comparator having a hysteresis characteristic is used as the second comparator 15, the stability of the charge control is improved when the charging voltage of the discharge capacitor 9 is reduced due to natural discharge or the like and recharged. .

In addition, this invention is not limited to embodiment mentioned above. For example, the circuit configuration illustrated in the present embodiment is not limited to a specific configuration. FIG. 3 shows a main part of a permission signal generation circuit 33 which is a modification of the permission signal generation circuit 3 of the flash discharge tube power supply circuit 1. As shown in the figure, the connection order of the bipolar transistor 17 and the thyristor 18 is changed, the collector of the bipolar transistor 17 is connected to the output terminal of the permission signal S ₃ of the connector 20, and the anode of the thyristor 18 is connected to the bipolar transistor 17. It may be connected to the emitter.

1 is a circuit block diagram of a power supply circuit 1 for a flash discharge tube that is a preferred embodiment of the present invention. FIG. FIG. 2 is a timing chart of various signals generated by the flash discharge tube power supply circuit of FIG. 1, (a) is a timing chart of a light emission trigger, and (b) is a timing chart of charging voltage of the discharge capacitor of FIG. 1. (C) is a timing chart of the permission signal. It is a circuit diagram which shows the principal part of the permission signal generation circuit which is a modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Flash discharge tube power supply circuit, 2 ... Power supply circuit, 3,33 ... Permit signal generation circuit, 3 ... Permit signal generation circuit, 4 ... Charge control circuit, 5 ... Light emission trigger generation circuit, 6 ... DC power supply, 9 ... Discharge Capacitors, 14 ... first comparator, 15 ... second comparator, 16 ... detection circuit, 17 ... bipolar transistor (first semiconductor element), 18 ... thyristor (second semiconductor element), 21 ... external device, L ... flash discharge tube, S ₃ ... permission signal, TR ... light emission trigger, V _C1 , V _C2 ... comparison signal, V _R ... reference voltage.

Claims (5)

A permission signal generation circuit for generating a permission signal for permitting light emission of the flash discharge tube to an external device by detecting a charging voltage of a discharge capacitor for light emission of the flash discharge tube;
A first comparator that receives a voltage signal corresponding to the charging voltage of the discharge capacitor and outputs a first comparison signal according to a comparison result between the charging voltage and a first reference voltage;
A voltage signal corresponding to the charging voltage of the discharge capacitor is input, and on / off of charging of the discharge capacitor is controlled according to a comparison result between the charging voltage and a second reference voltage higher than the first reference voltage. A second comparator that outputs a second comparison signal for:
A first semiconductor element that is turned on / off in response to the first comparison signal, and connected in series to the first semiconductor element, is turned on in response to a second comparison signal, and the first semiconductor element is turned off. A detection circuit that includes a second semiconductor element that is turned off in response to a transition to a state, detects that both of the first and second semiconductor elements are in an on state, and outputs the detection signal as the permission signal;
A permission signal generation circuit comprising: The detection circuit includes:
A transistor having a base connected to the output of the first comparator;
A thyristor having a gate connected to an output of the second comparator, a cathode connected to a collector of the transistor, and an anode connected to a terminal for outputting the permission signal;
The permission signal generation circuit according to claim 1. The detection circuit includes:
A transistor having a base connected to the output of the first comparator and a collector connected to a terminal for outputting the permission signal;
A thyristor having a gate connected to the output of the second comparator and an anode connected to the emitter of the transistor;
The permission signal generation circuit according to claim 1.   The permission signal generation circuit according to claim 1, wherein the second comparator is a hysteresis comparator having a hysteresis characteristic. The permission signal generation circuit according to any one of claims 1 to 4,
A power supply circuit including the discharge capacitor and supplying electric charge to the flash discharge tube;
A charge control circuit that receives a signal corresponding to the second comparison signal from the permission signal generation circuit and controls on / off of charging of the discharge capacitor in the power supply circuit according to the second comparison signal;
A light emission trigger generating circuit that discharges charges accumulated in the discharge capacitor by applying a light emission trigger to the flash discharge tube according to a light emission trigger control signal input from the external device;
A power supply circuit for a flash discharge tube, comprising:

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