Title of Invention

FLASHLIGHT GENERATING CIRCUIT.

Abstract

In a flashlight generating circuit, a primary side winding 16_3a of a trigger coil 163 and a arc tube 161 are arranged in a discharge loop L1 where an electric force discharged from a main capacitor 13 flows, a voltage of an internal battery 1 is stepped up to a predetermined voltage by a step-up circuit 11, an electric power is stored in the main capacitor 13 and a trigger-use capacitor 16_2, a trigger switch 15 is closed so that an electric current is allowed to flpw in the primary side winding 16_3a so that a light is emitted from the arc tube 16_1 by a trigger voltage from a secondary side winding 16_3b.

Full Text

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a flashlight generating circuit for generating a flashlight. Description of the Related Art Conventionally, a camera, which emits a flashlight in synchronization with a shutter action so as to take a photograph of a subject in the case where a brightness of the subject is insufficient, is known. Such a camera is provided with a flashlight generating circuit for generating a flashlight. Fig. 14 is a diagram of a conventional flashlight generating circuit. A flashlight generating circuit 200 shown in Fig. 14 is provided with a step-up circuit 211 which is connected to an internal battery 1 for controlling the whole camera. This step-up circuit 211 rises a voltage from the internal battery 1 to a predetermined voltage. In addition, the flashlight generating circuit 200 is provided with a main capacitor 213 for storing an electric power stepped up by the step-up circuit 211 via a diode 212. A (-) side of the main capacitor 213 is connected to an anode side of the diode 212, and a cathode side of the diode 212 is connected to a (-) output side of the step-up circuit 211. Moreover, a ( + ) side of the main capacitor 213 is connected to a ( + ) output side of the step-up circuit 211. Further, a resistance element 214 and a trigger switch 215 are connected to the (-) side and the (+) side of the main capacitor 213 in series, and an arc tube 216 is arranged parallel to the main capacitor 213. The arc tube 216 has an anode 216a and a cathode 216b and a side electrode 216c, and a xenon (XE) gas is sealed in the inside of the arc tube 216. Furthermore, the flashlight generating circuit 200 is provided with a trigger coil 218 which is composed of a primary- side winding 218a with a predetermined winding number and a secondary side winding 218b with a larger winding number.-. One end of the primary side winding 218a is connected to a connection point between the resistance element 214 and the trigger switch 215 via a trigger-use capacitor 217. On the other hand, one end of the secondary side winding 218b is connected to the side electrode 216c of the arc tube 216. The other end of the primary side winding 218a and the other end of the secondary side winding 218b are_connected commonly to the anode 216a of the arc tube 216. In the flashlight generating circuit 200 having the above structure, at first the electric power from the internal battery 1 is stepped up by the step-up circuit 211 in a state that the trigger switch 215 is opened. The stepped-up electric power is stored in the main capacitor 213 via the diode 212. Moreover, the stepped-up electric power is also stored in the trigger-use capacitor 217 via the primary side winding 218a, the trigger-use capacitor 217, the resistance element 214 and the diode 212. Next, the trigger switch 215 is closed in synchronization with the action of the shutter of the camera when taking a picture. The electric power stored in the trigger-use capacitor 217 is discharged. As a result, an electric current flows in the primary side winding 218a, and an electromotive force is caused in the secondary side winding 218b. Here, since a winding number of the secondary side winding 218b is larger than a winding number of the primary side winding 218a, the electromotive force which is caused in the secondary side winding 218b is amplified so as to be large. Since this large electromotive force is given as a trigger voltage to the,side electrode 216c of the arc tube 216, the xenon gas sealed in the arc tube 216 is excited. As a result, the electric power stored in the main capacitor 213 is discharged via a discharge loop L of the (+) side of the main capacitor 213, the anode 216a, the cathode 216b and the (-) side of the main capacitor 213 so that a flashlight is generated from the arc tube 216. In such a manner_,. the flashlight is emitted. Fig. 15 is a diagram of a conventional flashlight generating circuit which is different from the flashlight generating circuit shown in Fig. 14. Here, the same reference numerals are given to the components which are the same as those of the flashlight generating circuit 200 shown in Fig. 14. The ( + ) output side of the step-up circuit 211 composing the flashlight generating circuit 210 is connected to the (+) side of the main capacitor 213 via the diode 212, and the (-) output side of the step-up circuit 211 is connected to the (-) side of the main capacitor 213 . Further, the resistance element 214 and the trigger switch 219 which are connected in series are arranged on the ( + ) side and the (-) side of the main capacitor 213. Moreover, the ( + ) side and the (-) side of the main capacitor 213 are connected to the anode 216a and the cathode 216b of the arc tube 216. The connection point between the resistance element 214 and the trigger switch 219 is connected to one end of the primary side winding 218a of the trigger coil 218 via the trigger-use capacitor 217, and the one end of the secondary side winding 218b of the trigger coil 218 is connected to the side electrode 216c of the arc tube 216. The respective other ends of the primary side winding 218a and the secondary side winding 218b are connected commonly to the cathode 216b of the arc tube 216. In the flashlight generating circuit 210 having the above structure, when the trigger switch 219 is closed, the electric power stored in the trigger-use capacitor 217 is discharged. As a result, an electric current flows in the primary side winding 218a and a strong electromotive force is generated in the secondary side winding 218b. This electromotive force is given as a trigger voltage to the side electrode 216c of the arc tube 218 , and a xenon gas sealed in the arc tube 216 is excited. The electric power stored in the main capacitor 213 is discharged through the discharge loop of the (+) side of the main capacitor 213, the anode 216a, the cathode 216b and the (-) side of the main capacitor 213 so that a flashlight is generated from the arc tube 216. In the above-mentioned flashlight generating circuit 200 or 210, when the trigger switch 215 or 219 is closed and a trigger voltage is given to the arc tube 216, electric discharge starts to take place instantaneously in the arc tube 216, and the light emission takes an abrupt rising light emission curve (hereinafter, referred to as abrupt light emission curve), in which a peak light amount is large and light emitting time is short, so as to be ended. As for the light emission in such an abrupt light emission curve, it is generally difficult to control exposure by means of the flashlight accurately in a near distance. Particularly in an automatically adjusted flashlight generating apparatus having an exposure adjusting circuit for controlling to stop the emission of the flashlight at the time of reaching a predetermined light amount, since the flashlight emission duration is too short, a delay of the response in the exposure adjusting circuit cannot follow the emission of the flashlight when a light amount is adjusted. Therefore, there arises a problem that the adjustment of a light amount in the automatically adjusted flashlight generating apparatus is difficult. In addition, in order to stop the emission of the flashlight during the emission, a non-contact switch is arranged in the discharge loop via the arc tube 216, and the non-contact switch is turned off so as to stop the light emission. This technique is known, but in order to obtain a predetermined light amount of the flashlight with short light emission connection time, an extremely great electric current flows . As a result, it is necessary to adopt a large-sized and expensive non-contact switch arranged in the discharge loop which can « withstand the great electric current. Further, in the light emission with abrupt light emission curve, a color temperature of the flashlight is high, and a light having much blue component is emitted. In photography, in order to correct such a blue component of the light, it is necessary to arrange a protector, for example, composed by coloring a transparent plate before a light emitting section. There arises a problem that the cost rises. In order to solve these problems, there suggests a technique that a choke coil is added into the discharge loop so that the light emission curve becomes gentle. Fig. 16 is a diagram of a conventional flashlight generating circuit which is constituted so that a choke coil is connected to a main capacitor in series and a thyristor is connected to an arc tube parallel. In_a flashlight generating circuit 220 shown in Fig. 16, a choke coil 221 is connected to the main capacitor 213 in series. Moreover, a thyristor 222 is connected to the arc tube 216 parallel. A gate of the thyristor 222 is connected to a control terminal 224 for controlling on/off operation of the thyristor 222. Moreover, a resistance element 223 for adjusting a gate voltage of the thyristor 222 is provided on the gate of the thyristor 222 and the (-) side of the main capacitor 213. In this flashlight generating circuit 220, at the first time when a power of the camera is turned on, a control signal of 'L' level is input into the control terminal 224, and the thyristor 222 is in the off state. Moreover, an electric power « is stored in both the main capacitor 213 and the trigger-use capacitor 217. When the trigger switch 219 is closed, the electric power stored in the trigger-use capacitor 217 is discharged, and an electric current flows in the primary side winding 218a and an electromotive force is generated in the secondary side winding 218b. The electromotive force is given to the side electrode 216c of the arc tube 216, and the xenon gas sealed in the arc tube 216 is excited. The electric power stored in the main capacitor 213 is discharged through the discharge loop of the ( + ) side of the main capacitor 213, the choke coil 221, the anode 216a, the cathode 216b and the (-) side of the main capacitor 213 so that a flashlight is generated from the arc tube 216. Here, since the choke coil 221 is provided in the discharge loop, a peak value of the electric current flowing in the arc tube 216 is suppressed. Therefore, the light emission curve becomes gentle, and the color temperature of the flashlight is lowered, and the light emission color is closer to a natural color where the blue component is less. Next, an emitted light amount is integrated in an exposure adjusting circuit (not sown) of the automatically adjusted flashlight generating apparatus, and at the time of reaching a predetermined light amount, a pulse signal of H level is input into the control terminal 224 so that the thyristor 222 is turned on. Here, an impedance of the thyristor 222 in the on state is smaller than an impedance of the arc tube 216 in the exciting state (for example, 1/10). Therefore, the electric power * stored in the main capacitor 213 bypasses the (+) side of the main capacitor 213, the choke coil 221, thyristor 222 and the (-) side of the main capacitor 213 so that the light emission is stopped. Here, since a peak value of the electric current flowing in the thyristor 222 is suppressed by the choke coil 221, the thyristor 222 can be composed of an element whose allowable current is comparatively small. In such a manner, a light amount is controlled accurately even in a near distance. Fig. 17 is a diagram of a conventional flashlight generating circuit which is constituted so that a choke coil and a thyristor are connected to both ends of a main capacitor in series. In a flashlight generating circuit 230 shown in Fig. 17, the choke coil 221 and the thyristor 222 are connected to both the ends of the main capacitor 213 in series. When the trigger switch 219 is closed, the electric power stored in the trigger-use capacitor 217 is discharged, and an electric current flows in the primary side winding 218a and an electromotive force is generated in the second side winding 218b. This electromotive force is given to the side electrode 216c of the arc tube 218, and a xenon gas sealed in the arc tube 216 is excited. An electric power stored in the main capacitor 213 is discharged through the discharge loop of the ( + ) side of the main capacitor 213, the anode 216a, the cathode 216b and the (-) side of the main capacitor 213 so that a flashlight is generated from the arc tube 216. Next, a light emission amount is integrated by an exposure adjusting circuit (not shown) of the automatically adjusted flashlight generating apparatus, and at the time of reaching a predetermined light amount, a pulse signal of 'H' level is input into the control terminal 224 so that the thyristor 222 is turned on. The electric power stored in the main capacitor 213 bypasses the (+) side of the main capacitor 213, the choke coil 221, the thyristor 222 and the (-) side of the main capacitor 213 so that the light emission is stopped. In such a manner, an electric current having a large peak value is prevented from flowing in the thyristor 222 by the choke coil 221. However, in the above-mentioned flashlight generating circuit 220 and 230, since the choke coil 221 is added so as to suppress the peak value of the electric current flowing in the arc tube 216 and the thyristor 222, there arises problems that the cost rises and an area of a substrate circuit is large. SUMMARY OF THE INVENTION The present invention is devised in order to solve the above problems, and it is an object of the present invention to provide a flashlight generating circuit in which a cost and an area of a substrate circuit are reduced. Accordingly, the present invention provides a flashlight generating circuit, comprising : a step-up circuit; a main capacitor for storing an electric power which is stepped up by said step-up circuit; an arc tube for generating a light by means of the electric power discharged from said main capacitor; and a trigger circuit which is provided with a trigger-use capacitor and a trigger coil in which a primary side winding is connected to said trigger-use capacitor and an electric power flowing in said trigger-use capacitor is transmitted to a secondary side winding so that a trigger voltage is applied to said arc tube, wherein the primary side winding of said trigger coil as well as said arc tube are arranged in a discharge loop where the electric power discharged from said main capacitor flows. In the flashlight generating circuit of the present invention, the primary side winding of the trigger coil as well as the arc tube is arranged in the discharge loop where the electric power discharged from the main capacitor flows. For this reason, time from starting the discharge in the arc tube and until a peak value of a light emission amount becomes maximum is delayed, and the peak value of the light emission amount becomes comparatively small and a light emission duration is kept longer so that a comparatively gentle light emission curve is obtained. Therefore, it is not necessary to add a choke coil in the discharge loop in order to obtain a gentle light emission curve unlike the conventional technique. As a result, the cost and an area of a substrate circuit are reduced. Here, the primary side winding of the trigger coil may be arranged on an anode side of the arc tube, or the primary side winding of the trigger coil may be arranged on a cathode side of the arc tube. In such a manner, when the primary side winding of the trigger coil is arranged on the anode side or on the cathode side of the arc tube, a degree of freedom of the circuit design is heightened. Further, the flashlight generating circuit of the present invention is provided with a non-contact switch in the discharge loop. In the case where the non-contact switch is provided in the discharge loop, the non-contact switch is turned on at the light emission starting timing so that a flashlight is generated from the arc tube. At the time of reaching a predetermined amount of light, the non-contact switch is turned off so that the flashlight is stopped. AS a result, an automatically adjusted light control can be made in an automatically adjusted flashlight generating apparatus. In the case where the non-contact switch is provided, it is preferable to provide a by-pass-use diode for allowing an electric current caused by a back electromotive force generated in the primary side winding of the trigger coil to bypass when the non-contact switch is changed from an on-state into an off-state. When the non-contact switch with good performance which is instantaneously changed from the on-state into the off-state is used, light adjusting performance is improved, but a great back electromotive force is generated in the primary side winding of the trigger coil. When the by-pass-use diode is provided, the generated back electromotive force is applied directly to the non-contact switch so that the non-contact switch is prevented from being destroyed. In addition, the trigger-use capacitor may apply a voltage with polarity for helping a flow of the electric force discharged from the main capacitor to between the anode and the cathode of the arc tube at timing that a trigger voltage is applied to the arc tube. In another way, a voltage application-use capacitor for applying a voltage with polarity, for helping a flow of the electric force discharged from the main capacitor to between the anode and the cathode of the arc tube at timing that a trigger voltage is applied to the arc tube, may be provided besides the trigger-use capacitor. In the case where the voltage application-use capacitor is provided, it is preferable that the voltage application- use capacitor applies a voltage at the time when the main capacitor and the voltage application-use capacitor are connected in series to between the anode and the cathode of the arc tube at the timing that the trigger voltage is applied to the arc tube in cooperation with the main capacitor. When the voltage with polarity is applied to between the anode and the cathode of the arc tube at the timing that a trigger voltage is applied to the arc tube, a light is easily generated from the arc tube when a trigger voltage is applied to the arc tube. As a result, a capacitance of the trigger-use capacitor is lowered, or the trigger voltage can be lowered. Further, the trigger-use capacitor may be kept in a discharged state before the timing that a trigger voltage is applied to the arc tube, and may apply a trigger voltage to the arc tube via the trigger coil after the electric power discharged from the main capacitor passes therethrough. In addition, it is preferable that the primary side winding of the trigger coil and the main capacitor are arranged in series. Since the primary side winding of the trigger coil and the main capacitor are arranged in series, the primary side winding serves as a choke coil for suppressing a peak value of the electric current flowing in the arc tube. As a result, a gentle light emission curve can be obtained. Further, the flashlight generating circuit of the present invention may be provided with a by-pass circuit for bypassing an electric current which is supplied from the main capacitor and flows via the arc tube during the flowing of the electric current in the arc tube so as to stop the electric current flowing in the arc tube. When such a by-pass circuit is provided, the flashlight from the arc tube can be stopped during the emission . Therefore, a light amount can be controlled. In addition, the by-pass circuit may have: a resistance arranged in series with the arc tube; and a switch element which is arranged parallel with the arc tube between a connection node, arranged between the resistance and one terminal of the arc tube, and the other terminal of the arc tube. Since the by-pass circuit has the resistance and the switch element arranged in such a manner, when a flashlight is generated from the arc tube, both the primary side winding and the resistance suppress a peak value of the electric current flowing in the arc tube. As a result, a gentler light emission curve is obtained, and when the flashlight from the arc tube is stopped during the emission, a peak value of the electric current flowing in the switch element can be suppressed. Further, the by-pass circuit may have a resistance and a switch element for controlling on/off state of by-pass which are arranged in series. Since the by-pass circuit has the resistance and the switch element arranged in series, when a flashlight which is generated from the arc tube is stopped, both the primary side winding and the resistance can suppress a peak value of the electric current flowing in the switch element. In addition, a light adjusting circuit, for detecting timing that a predetermined amount of a light is emitted from the arc tube according to the electric current flowing in the arc tube and instructing the by-pass circuit to bypass the electric current, may be provided. When such a light adjusting circuit is provided, the flashlight from the arc tube can be stopped at the timing that a predetermined amount of light is emitted from the arc tube. For this reason, an automatically adjusting flashlight generating apparatus can be realized. Further, the by-pass circuit may be detachably connected parallel with the arc tube. With this structure, when a normal flash apparatus which does not stop a flashlight during emission, and an automatically adjusted flashlight generating apparatus (auto-flash apparatus) for controlling a flashlight so that its emission is stopped at the time of reaching a predetermined light amount, are manufactured, the flashlight generating circuit to which the arc tube is mounted and the by-pass circuit can be manufactured individually. As a result, circuit parts are commonly used so that the manufacturing process is simplified and the troublesome of product management is reduced. Moreover, when an adaptor into which a circuit substrate is incorporated is attached to a housing of a normal flash apparatus, an auto-flash apparatus can be realized easily. /ACCOMPANYING BRIEF DESCRIPTION OF THE/DRAWINGS Fig. 1 is a diagram showing a flashlight generating circuit according to a first embodiment of the present invention. Fig. 2 is a diagram showing an light emission characteristic of the flashlight generating circuit shown in Fig. 1 and a light emission characteristic of a conventional flashlight generating circuit shown in Fig. 14. Fig. 3 is a diagram showing a flashlight generating circuit according to a second embodiment of the present invention. Fig. 4 is a diagram showing a flashlight generating circuit according to a third embodiment of the present invention. Fig. 5 is a diagram showing a flashlight generating circuit according to a fourth embodiment of the present invention. Fig. 6 is a diagram showing a flashlight generating circuit according to a fifth embodiment of the present invention. Fig. 7 is a diagram showing a flashlight generating circuit according to a sixth embodiment of the present invention. Fig. 8 is a diagram showing a flashlight generating circuit according to a seventh embodiment of the present invention. Fig. 9 is a diagram showing a flashlight generating circuit according to an eighth embodiment of the present invention. Fig. 10 is a diagram showing a flashlight generating circuit^jaccording to a ninth embodiment of the present invention. Fig. 11 is a diagram showing a flashlight generating circuit according to a tenth embodiment of the present invention. Fig. 12 is a diagram showing a flashlight generating circuit according to an eleventh embodiment of the present invention. Fig. 13 is a diagram showing a flashlight generating circuit according to a twelfth embodiment of the present invention. Fig. 14 is a diagram of a conventional flashlight generating circuit. Fig. 15 is a diagram of a conventional flashlight generating circuit which is different from the flashlight generating circuit shown in Fig. 14. Fig. 16 is a diagram of a flashlight generating circuit which is constituted so that a choke coil is connected to a main capacitor in series and a thyristor is connected to an arc tube parallel. Fig. 17 is a diagram of a flashlight generating circuit which is constituted so that a choke coil and a thyristor are connected to both ends of a main capacitor in series. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS There will be described below preferred embodiments of the present invention. Here, a flashlight generating circuit which is mounted to a camera will be explained. Fig. 1 is a diagram showing a flashlight generating circuit according to a first embodiment of the present invention. A flashlight generating circuit 10 shown in Fig. 1 is provided with a step-up circuit 11 which is connected to an internal battery 1 for controlling the whole camera. This step-up circuit 11 steps up a voltage from the internal battery 1 to a predetermined voltage. In addition, the flashlight generating circuit 10 is provided with a main capacitor 13 for storing an electric power which is stepped up by the step-up circuit 11 via a diode 12. A resistance element 14 and a trigger switch 15 are connected to both ends of the main capacitor 13 in series. Further, the flashlight generating circuit 10 is provided with a trigger circuit 16 having an arc tube 16_1, a trigger-use capacitor 16_2 and a trigger coil, 16_3. The arc tube 16_1 has an anode 16_la, a cathode 16_lb and a side electrode 16_lc, and a xenon (XE) gas is sealed in the arc tube 16_1. This arc tube 16_1 emits a light by means of the electric power discharged from the main capacitor 13. Moreover, the trigger coil 16_3 is composed of a primary side winding 16_3a having a predetermined winding number and a secondary side winding 16_3b having a winding number larger than that of the primary side winding 16_3a. One end of the primary side winding 16_3a is connected to the cathode 16_la of the arc tube 16_1. The one end of the primary side winding 16_3a is connected, also to a connection point between the resistance element 14 and the trigger switch 15 via the trigger-use capacitor 16_2. Meanwhile, one end of the secondary side winding 16_3b is connected to the side electrode 16_lc of the arc tube 16_1. The other end of the primary side winding 16_3a and the other end of the secondary side winding 16_3b are connected commonly to a (+) side of the main capacitor 13. The trigger coil 16_3 transmits an electric power flowing in the trigger-use capacitor 16_2 to the secondary side winding 16_3b so as to apply a trigger voltage to the arc tube 16_1. The primary side winding 16_3a of the trigger coil 16_3 as well as the arc tube 16_1 is arranged in a discharge loop LI where the electric power discharged from the main capacitor 13 flows. In the flashlight generating circuit 10 having such a structure, at first an electric power from the internal battery 1 is stepped up by the step-up circuit 11 in a state that the trigger switch 15 is opened. The stepped-up electric power is stored in the main capacitor 13 via the diode 12. Moreover, the stepped-up electric power is stored also in the trigger-use capacitor 16_2 through the primary side winding 16_3a, the trigger-use capacitor 16_2, the resistance element 14 and the diode 12. Next, the trigger switch 15 is closed in synchronization with an action of a shutter of the camera at the time of photography. The voltage of the main capacitor 13 is applied to one end of the trigger-use capacitor 16_2 via the trigger switch 15, as a result, a positive voltage which is higher than the applied voltage by a voltage of the trigger-use capacitor 16_2 is output from the other end of the trigger-use capacitor 16_2. This positive voltage is applied to the anode 16_la of the arc tube 16_1 and the primary side winding 16_3a. As a result, the electric power stored in the trigger-use capacitor 16_2 is discharged, and an electric current flows in the primary side winding 16_3a so that an electromotive force is caused in the secondary side winding 16_3b. Here, since a winding number of the secondary side winding 16_3b is larger than a winding number of the primary side winding 16_3a, the electromotive force caused in the second side winding 16_3b is amplified to be strong. Since such a strong electromotive force is applied as a trigger voltage to the side electrode 16_lc of the arc tube 16_1, the xenon gas sealed in the arc tube 16_1 is excited. The electric power stored in the main capacitor 13 is discharged via the discharge loop LI of the ( + ) side of the main capacitor 13, the primary side winding 16_3a, the anode 16_la, the cathode 16_lb and the (-) side of the main capacitor 13 so that a flashlight is generated from the arc tube 16_1. In such a manner, the flashlight is emitted. In the flashlight generating circuit 10 of the present embodiment, as mentioned above, the trigger-use capacitor 16_2 applies the positive voltage to the anode 16_la of the arc tube 16_1 and a negative voltage to the cathode 16_lb at timing that the trigger voltage is applied to the arc tube 16_1 at the time when the trigger switch 15 is closed, namely, applies voltages with polarity for helping the flow of the electric power discharged from the main capacitance 13. Therefore, this voltage coupled with the trigger voltage applied to the arc tube 16_1 makes light emission from the arc tube 16_1 more easy. Fig. 2 is a diagram showing a light emission } characteristic of the flashlight generating circuit 10 shown w in Fig. 1 and a light emission characteristic of the conventional flashlight generating circuit 200 shown in Fig. 14. A curved line A show in Fig. 2 is a light emission curve showing the light emission characteristic of the flashlight generating circuit 200 from the time when the light emission is started to the time when the light emission is ended. Meanwhile, a curved line B is a light emission curve showing the light emission characteristic of the flashlight generating circuit 10 of the present embodiment from the time when the light emission is started to the time when the light emission is ended. There is no great difference between an integral value of a light emission amount represented by the curved line A and an integral value of a light emission amount represented by the curved line B. In the conventional flashlight generating circuit. 200, as described with reference to Fig. 14, since only the arc tube is arranged in the discharge loop, a discharge is started instantaneously in the arc tube, and the light emission takes the abrupt light emission curve represented by the curved line A so as to be ended. In the light emission represented by the abrupt light emission curve, it is generally difficult to control an exposure by means of the flashlight accurately in a near distance. Moreover, since the color temperature of the flashlight is high and a light having great blue component is emitted, it is necessary to arrange, for example, a protector formed by coloring a resin material before a light emission section. Meanwhile, in the flashlight generating circuit 10 of the present embodiment, the primary side winding 16_3a of the trigger coil 16_3 as well as the arc tube 16_1 is arranged in the discharge loop LI where the electric power discharged from the main capacitor 13 flows. For this reason, as represented by the curved line B in Fig. 2, time from starting the discharge in the arc tube 16_1 and until a peak value of a light emission amount becomes maximum is delayed, and the peak value of the light emission amount becomes comparatively small and a gentle light emission curve is obtained so that a light emission duration is kept longer. In addition, a value of the electric current flowing in the arc tube 16_1 of the flashlight generating circuit 10 is smaller than a value of the electric current flowing in the arc tube of the conventional flashlight generating circuit-200. For this reason, although a light amount of the flashlight is being maintained, the color temperature of the flashlight is I ! lowered, and the light emission color is closer to a natural color with less blue component. As a result, a light with good photographic congeniality can be obtained. Further, since the value of the electric current flowing in the arc tube 16_1 is 1 small, the life of the arc tube 16_1 is lengthened. In addition, when the present invention is compared with the conventional technique that a choke coil is added into a discharge loop in order to obtain a gentle light emission curve, the cost and an area of a substrate circuit are reduced. Fig. 3 is a diagram showing a flashlight generating circuit according to a second embodiment of the present invention. Here, the same reference numerals are given to the components which are the same as those of the flashlight generating circuit 10 shown in Fig. 1, and characteristic portion will be explained. A flashlight generating circuit 20 of the present embodiment is maintained in a state of discharge before the timing that the trigger-use capacitor 16_2 applies a trigger voltage to the arc tube 16_1, and when an electric power discharged from the main capacitor 13 is allowed to pass, the trigger voltage is applied to the arc tube 16_1 via the trigger coil 16_3. The trigger-use capacitor 162 and the trigger switch 15 are connected in series between the anode 16_la and the cathode 16_lb of the arc tube 16_1 composing the flashlight generating circuit 20 shown in Fig. 3 in an order from the anode 16_la side. Moreover, the resistance element 14 is connected to the trigger-use capacitor 16_2 parallel. At the first time when the power source of the camera is turned on, the trigger switch 15 is opened, and after the power source is turned on, the main capacitor 13 is charged. Meanwhile, the trigger-use capacitor 16_2 is kept in the state of discharge. Next, the trigger switch 15 is closed in synchronization with the action of the shutter of the camera at the time of photography. An electric current flows through the path of the ( + ) side of the main capacitor 13, the primary side winding 16_3a, the trigger-use capacitor 16__2, the trigger switch 15 and the (-) side of the main capacitor 13. Since the electric current flows in the primary side winding 163a, the trigger voltage is applied from the secondary side winding 16_3b to the side electrode 16_lc. The electric power stored in the main capacitor 13 is discharged through a discharge loop L2 of the ( + ) side of the main capacitor 13 , the primary side winding 16_3a, the anode 16_la, the cathode 16_lb and the (-) side of the main capacitor 13. As a result, the flashlight is generated from the arc tube 16_1. When the electric power discharged from the main capacitor 13 is allowed to pass at the time when the trigger switch 15 is closed in such a manner, the electric current is allowed to flow in the primary side winding 16_3a so that the trigger voltage is obtained. The light may be emitted from the arc tube 16_1 by this trigger voltage. Fig. 4 is a diagram showing a flashlight generating circuit according to a third embodiment of the present invention. In the flashlight generating circuit 10 shown in Fig. 1, the primary side winding 16_3a of the trigger coil 16_3 is arranged^pn the anode 16_la side of the arc tube 16_1, but in the flashlight generating circuit 30 shown in Fig. 4, the primary side winding 16_3a of the trigger coil 16_3 is arranged on the cathode 16_lb side of the arc tube 16_1. Moreover, a non-contact switch 17 is arranged between the primary side winding 16_3a and the main capacitor 13 in the discharge loop L3. The non-contact switch 17 has a control terminal 18 for controlling on/off state of the non-contact switch 17. Moreover, the resistance element 14 and the trigger-use capacitor 16_2 are connected in series to both the ends of the main capacitor 13. The contact point between the resistance element 14 and the trigger-use capacitor 16_2 is connected to the cathode 16_lb and the primary side winding 16_3a via the diode 16_4. In the flashlight generating circuit 30 of the present embodiment, at the first time when the power source of the camera is turned on, a control signal of 'L' level is input into the control terminal 18, and the non-contact switch 17 is in the off state. Moreover, an electric power is stored in both the main capacitor 13 and the trigger-use capacitor 16_2. Here, a control signal of 'H' level is input into the control terminal 18 in synchronization with the action of the shutter of the camera at the time of photography. The non- contact switch 17 is turned on, and the electric power stored in the trigger-use capacitor 16_2 is discharged via the diode 16_4, the primary side winding 16_3a and the non-contact switch 17 . As a result, the electric current flows in the primary side winding _1.6_3 a, and the trigger voltage is applied from the secondary side winding 16_3b to the side electrode 16_lc. The electric power stored in the main capacitor 13 is discharged through the discharge loop L3 of the ( + ) side of the main capacitor 13, the anode 16_la, the cathode 16_lb, the primary side winding 16_3a, the non-contact switch 17 and the (-) side of the main capacitor 13 . As a result, a flashlight is generated from the arc tube 16_1. Thereafter, a light emission amount is integrated in an exposure adjusting circuit (not shown) of the automatically adjusted flashlight generating apparatus, and at the time of reaching a predetermined light amount, the control signal is changed into 'L' level and the non-contact switch 17 is turned off so that the light emission is stopped. In such a manner, the non-contact switch 17 is arranged in the discharge loop L3 and the non-contact switch 17 is controlled so that the light amount can be controlled accurately in a near distance. Fig. 5 is a diagram showing a flashlight generating circuit according to a fourth embodiment of the present invention. In a flashlight generating circuit 40 shown in Fig. 5, the non-contact switch 17 is arranged in a discharge loop L4. Moreover, the trigger-use capacitor 16_2 composing the flashlight generating circuit 40 is maintained in a discharged state before the timing that a trigger voltage is applied to the arc tube 16_1, and when an electric power discharged from the main capacitor 1 is allowed to pass, the trigger voltage is applied to the arc tube 16_1 via the trigger coil 16_3. The diode 16_4 and the trigger switch 15 are connected in series to between the anode 16_la and the cathode 16_lb of the arc tube 16_1 in an order from the anode 16_la side . Moreover, the resistance element 14 is connected to the trigger switch 15 parallel. Further, the non-contact switch 17 is arranged between the cathode 16_lb and the main capacitor 13. At the first time when the power source of the camera is turned on, a control signal of ' L' level is input into the control terminal 18, and the non-contact switch 17 is in the off state. The main capacitor 13 is charged, and the trigger-use capacitor 16_2 is kept in the discharged state. Here, a control signal of 'H' level is input into the control terminal 18 in synchronization with the action of the shutter of the camera at the time of photography. The non- contact switch 17 is turned on, and the electric power stored in the main capacitor 13 is discharged via the primary side winding 16_3a, the diode 16_4, the trigger-use capacitor 16_2 and the non-contact switch 17 . As a result, an electric current flows in the primary side winding 16_3a, and a trigger voltage is applied from the secondary side winding 16_3b to the-side electrode 16_lc. The electric power stored in the main capacitor 13 is discharged through the discharge loop L4 of the ( + ) side of the main capacitor 13 , the primary side winding 16_3a, the anode 16_la, the cathode 16_lb the non-contact switch 17 and the (-) side of the main capacitor 13. As a result, a flashlight is generated from the arc tube 16_1. Thereafter, at the time of reaching a predetermined light amount, the control signal is changed into 'L' level and the non-contact switch 17 is turned off so that the light emission is stopped. With this structure, the light amount may be controlled accurately. Fig. 6 is a diagram showing a flashlight generating circuit according to a fifth embodiment of the present invention. In a flashlight generating circuit 50 shown in Fig. 6, the non-contact switch 17 is arranged in a discharge loop L5. Moreover, the trigger-use capacitor 16_2 composing this flashlight generating circuit 50 applies a voltage with polarity for helping the flow of an electric power discharged from the main capacitor 13 to between the anode 16_la and the cathode 16_lb of the arc tube 16_1 at timing that a trigger voltage is applied to the arc tube 16_1. In the flashlight generating circuit 50, at the first time a control signal of ' L' level is input into the control terminal 18, and the non-contact switch 17 is in the off state. An electric power is stored in the main capacitor 13 via the diode 12. Moreover, the electric power is stored also in the trigger-use capacitor 16_2 via the diode 12, the resistance element 14, the trigger-use capacitor 16_2, the primary side winding 16_3a and the resistance element 16_6. Here, a control signal of "H" level is input into the control terminal 18 in synchronization with the action of the shutter of the camera at photography. The non-contact switch 17 is turned on, and an electric potential of one end (on the side of the non-contact switch 17) of the trigger-use capacitor 16_2 drops abruptly to a potential on the (-) side of the main capacitor 13. As a result, a negative voltage, which is lower than a voltage of the (-) side of the main capacitor 13 by a voltage of the trigger-use capacitor 16_2, is output from the other end of the trigger-use capacitor 16_2. This negative voltage is applied to the cathode 16_lb, and the electric power stored in the trigger-use capacitor 16_2 is discharged through the non-contact switch 17, the diode 16_5 and the primary side winding 16_3a. As a result, an electric current flows in the primary side winding 16_3a, and a trigger voltage is applied from the secondary side winding 163b to the side electrode 16_lc. The electric power stored in the main capacitor 13 is discharged through the discharge loop L5 which passes through the anode 16_la, the cathode 16_lb, the primary side winding 16_3a, the diode 16_4 and the non-contact switch 17. As a result, a flashlight is generated form the arc tube 16_1. In such a manner, at the timing that the trigger voltage is applied to the arc tube 16_1 at the time when the non-contact switch 17 is turned on, a positive voltage is applied to the anode 16_la and the negative voltage is applied to the cathode 16_lb, namely, the voltages with polarities for helping the flow of the electric power discharged from the main capacitor 13 are applied to between the anode 16_la and the cathode 16_lb of the arc tube 16_1. This voltage coupled with the trigger voltage applied to the arc tube 16_1 makes the light emission from the arc tube 16_1 easj-.er. Next, at the time of reaching a predetermined light amount, the control signal is changed into 'L1 level and the non-contact switch 17 is turned off so that the light emission is stopped. With this structure, the light amount may be controlled accurately. Fig. 7 is a diagram showing a flashlight generating circuit according to a sixth embodiment of the present invention. In the flashlight generating circuit shown in Fig. 7, the arc tube 16_1, the primary side winding 16_3a of the trigger coil 16_3 and the non-contact switch 17 are arranged in series in a discharge loop L6 in an order from the (+) side of the main capacitor 13. Moreover, the resistance element 14 and the trigger-use capacitor 16_2 are connected in series between the ( + ) side and the (-) side of the main capacitor 13 in an order from the ( + ) side. The connection point between the resistance element 14 and the trigger-use capacitor 16_2 is directly connected to the connection point between the arc tube 16_1 and the primary side winding 16_3a. Further, a by-pass-use diode 16-7 is connected to between the connection point between the trigger coil 16_3 and the non-contact switch 17 and the (+) side of the main capacitor 13, namely, an anode of the by-pass-use diode 16_7 is connected to the side of the non-contact switch 17 and a cathode is connected to the side of the main capacitor 13. In this flashlight generating circuit 60, at the first time when the power source of the camera is turned on, a control signal of 'L' level is input into the control terminal 18, and the non-contact switch 17 is in the off state. Moreover, an electric power is stored in both the main capacitor 13 and the trigger-use capacitor 16_2. Here, a control signal of 'H' level is input into the control terminal 18 in synchronization with the action of the shutter of the camera at the time of photography. The non- contact switch 17 is turned on, and the electric power stored in the trigger-use capacitor 162 is discharged via the primary side winding 16_3a and the non-contact switch 17. As a result, an electric current flows in the primary side winding 16_3a, and a trigger voltage is applied from the secondary side winding 16_3b to the side electrode 16_lc. The electric power stored in the main capacitor 13 is discharged via the discharge loop L6 which passes through the ( + ) side of the main capacitor 13, the anode 16_la, the cathode 16_lb, the primary side winding 16_3a, the non-contact switch 17 and the (-) side of the main capacitor 13. As a result, a flashlight is discharged from the arc tube 16_1. Next, a light emission amount is integrated in the exposure adjusting circuit (not shown) in the automatically adjusted flashlight generating apparatus, and at the time of reaching a predetermined light amount, the control signal is changed into 'L' level. The non-contact switch 17 is turned off so that the light emission is stopped. When the non-contact switch 17 is turned off, the electric current, which flows in the primary side winding 16_3a just before the turning-off, is abruptly cut off, and a strong back, electrom&tive force is generated in the primary side winding 16_3a. When this back electromotive force is applied directly to the non-contact switch 17, there is a possibility that the non-contact switch 17 is destroyed. However, in the case of the flashlight generating circuit of the sixth embodiment shown in Fig. 7, since the by-pass-use diode 16_7 is provided, an electric which is caused by the back electromotive force generated in the trigger coil 16_3 flows via the by-pass-use diode 16_7. As a result, a large voltage which is caused by the back electromotive force is prevented from being applied .' to the non-contact switch 17, and the non-contact switch 17 is prevented from being destroyed. Here, when the flashlight generating circuit 30 of the third embodiment shown in Fig. 4 is compared with the flashlight generating circuit 60 of the sixth embodiment shown in Fig. 7, there exist two differences. One is that the by-pass-use diode 16_7 which is provided in the flashlight generating circuit 60 is not provided in the flashlight generating circuit 30 shown in Fig. 4. This is because there exists a difference that the by-pass-use diode 16_7 should be provided according to strength of the electric current flowing in the arc tube 16_1, a withstand voltage of the non-contact switch 17 or a speed that the non-contact switch 17 is changed from the on-state to the off-state, or even if such a by-pass-use diode is not provided, the non-contact switch 17 is not destroyed. In the case of a design that a comparatively great electric current flows in the arc tube_^16_l or in the case the withstand voltage of the non-contact switch 17 is comparatively low or in the case where a speed that the non-contact switch 17 is changed from the on-state to the off-state is comparatively high, the by- pass-use diode is required, and in the opposite case, the by-pass-use diode is not necessarily required. In addition, the other difference between the flashlight generating circuit 30 shown in Fig. 4 and the flashlight generating circuit 60 shown in Fig. 7 is that the diode 16_4 is provided between the connection point between the resistance element 14 and the trigger-use capacitor 16_2 and the connection point between the arc tube 161 and the primary side winding 16_3a in the flashlight generating circuit 30 shown in Fig. 4, and these connection points are directly connected to each other in the flashlight generating circuit 60 shown in Fig. 7. As mentioned above, the non-contact switch 17 is turned on and the electric power stored in the trigger-use capacitor 16_2 is discharged so that the light emission is started. Therefore, after the starting of the light emission, the trigger-use capacitor 16_2 is empty at the timing that the non-contact switch 17 is changed from the on-state to the off-state. Here, when the non-contact switch 17 is changed from the on-state to the off-state, in the case of the flashlight generating circuit 30 shown in Fig. 4, the light emission is stopped at the changing timing. However, in the case of the flashlight generating circuit 60 shown in Fig. 7, the light emission is not exactly stopped at the changing timing, and the light emission is stopped after the trigger-use capacitor 16_2 is charged. As a result, over exposure might occur. Therefore, in the case of the flashlight generating circuit to be used for macrophotography, for example, in which a slight delay of the stop of the light emission greatly contributes to the exposure, the diode 16_4 is preferably provided. On the contrary, in the case where the flashlight generating circuit is mounted to a camera which does not take a picture in a near distance, the diode 16_4 is eliminated so that the cost may be reduced. Fig. 8 is a diagram showing a flashlight generating circuit according to a seventh embodiment of the present invention. In a flashlight generating circuit 70 shown in Fig. 8, the arc tube 16_1, the diode 16_4 , the primary side winding 16_3a of the trigger coil 16_3 and the non-contact switch 17 are arranged in series in a discharge loop L7 in an order from the (+) side of the main capacitor 13. In addition, the resistance element 14 is connected to between the ( + ) side of the main capacitor 13 and the connection point between the trigger coil 16_3 and the non-contact switch 17. A voltage application-use capacitor 16_8 is connected to between the connection point between the arc tube 16_1 and the diode 16_4 and the connection point between the trigger coil 16_3 and the non-contact switch 17. A resistance element 19 is connected between the connection point between the arc tube 16_1 and the diode 16_4 and the (-) side of the main capacitor 13. The_trigger-use capacitor 162 is connected to between the connection point between the diode 16_4 and the primary side winding 16_3a and the (-) side of the main capacitor 13. In this flashlight generating circuit 70, at the first time when the power source of the camera is turned on, a control signal of 'L' level is input into the control terminal 18, and the non-contact switch 17 is in the off-state. In this state, an electric power is stored in the main capacitor 13, and the electric power is stored also in the voltage application-use capacitor 16_8 via the resistance element 14, the voltage application-use capacitor 16_8 and the resistance element 19. Further, the electric power is stored also in the trigger-use capacitor 16_2 via the resistance element 14, the primary side winding 16_3a and the trigger-use capacitor 16_2. Here, a control signal of 'H' level is input into the control terminal 18 in synchronization with the action of the shutter of the camera at the time of photography. The non- contact switch 17 is turned on, an electric potential of one end of the voltage application-use capacitor 16_8 (on the side of the non-contact switch 17 charged to ( + )) is dropped abruptly to an electric potential of the ( - ) side of the main capacitor 13 . The other end of the voltage application-use capacitor 16_8 (on the side of the arc tube 16_1) has a negative voltage which is lower than the voltage of the (-) side of the main capacitor 13 by the voltage on both ends of the voltage application-use capacitor 16_8 . This negative voltage is applied to the cathode 16_lb of the arc tube 16_1. Therefore, at this instance, a sum of the charging voltages of the main capacitor 13 and the voltage application-use capacitor 16_8, namely, a voltage which is twice as much as the charging voltage of the main capacitor is applied to between the anode 16_la and the cathode 16_lb of the arc tube 16_1. In addition, when the non-contact switch 17 is turned on, the electric power stored in the trigger-use capacitor 16_2 is discharged via the primary side winding 16_3a and the non- contact switch 17. As a result, the electric current flows in the primary side winding 16_3a, and a trigger voltage is applied from the secondary side winding 163b to the side electrode 16_lc . The electric power stored in the main capacitor 13 is discharged via the discharge loop L7 which passes through the anode 16_la, the cathode 16_lb, the diode 16_4 , the primary side winding 16_3a and the non-contact switch 17. As a result, a flashlight is generated form the arc tube 16_1. In such a manner, in the case of the flashlight generating circuit 70 shown in Fig. 8, the voltage, which is twice as much as the charging voltage of the main capacitor 13, is applied to between the anode 16_la and the cathode 16_lb of the arc tube 16_1 by the action of the voltage application-use capacitor 16_8 at the timing that the trigger voltage is applied to the arc tube 16_1. This voltage coupled with the trigger voltage applied to the arc tube 16_1 ensure the light emission. Thereafter, at the time of reaching a predetermined light amount, the control signal is changed into 'L' level, and the non-contact switch 17 is turned off so that the light emission is stopped. With this structure, a light amount may be controlled accurately. Fig. 9 is a diagram showing a flashlight generating circuit according to an eighth embodiment of the present invention. In a flashlight generating circuit 80 shown in Fig. 9, the primary side winding 16_3a of the trigger coil 16_3 and the main capacitor 13 are arranged in series. The arc tube 16_1 is arranged parallel with the primary side winding 16_3a and the main capacitor 13 arranged in series. The resistance element 14 and a trigger switch 81 are arranged in series on both ends of the arc tube 16_1. The trigger-use capacitor 16_2 is arranged between the connection point between the resistance element 14 and the trigger switch 81 and the connection point between the main capacitor 13 and the primary side winding 16_3a. Moreover, the secondary side winding 16_3b of the trigger coil 16_3 is connected to the side electrode 16_3c of the arc tube 16_1. In the flashlight generating circuit 80 having such a structure, at first in a state that the trigger switch 81 is opened, an electric power from the internal battery 1 is stepped up by the step-up circuit 11. An electric power is stored in the main capacitor 13 via the diode 12, the main capacitor 13 and the primary side winding 16_3a of the trigger coil 16_3. Moreover, the electric power is stored also in the trigger- use capacitor 16_2 via the diode 12, the resistance element 14, the trigger-use capacitor 16_2 and the primary side winding 16_3a of the trigger coil 16_3. Next, the trigger switch 81 is closed in synchronization with the action of the shutter of the camera at the time of photography. The electric power stored in the trigger-use capacitor 16_2 is discharged, and an electric current flows in the primary side winding 16_3a so that an electromotive force is generated in the secondary side winding 16_3b. This electromotive force is applied to the side electrode 16_lc of the arc tube 16_1, and a xenon gas sealed in the arc tube 16_1 is excited. The electric power stored in the main capacitor 13 is discharged via a discharge loop L8 of the ( + ) side of the main capacitor 13, the anode 16_la, the cathode 16_lb, the primary side winding 16_3a and the ( - ) side of the main capacitor 13. As a result, a flashlight is generated from the arc tube 16_1. Here, since the primary side winding 16_3a of the trigger coil 16_3 and the main capacitor 13 are arranged in series, the primary side winding 16_3a serves as a choke coil for suppressing a peak value of the electric current flowing in the arc tube 16_1. As a result, a gentle light emission curve can be obtained. Fig. 10 is a diagram showing a flashlight generating circuit according to a ninth embodiment of the present invention. The flashlight generating circuit 90 shown in Fig. 10 is provided with a circuit substrate 91 to which the above- mentioned flashlight generating circuit 80 is mounted. This circuit substrate 91 has connection terminals 91_1 and 91_2. In addition, the flashlight generating circuit 90 is provided with a circuit substrate 92 having connection terminals 92_1 and 92_2. A by-pass circuit 90_1, which is composed of a thyristor 93 and a resistance element 94 connected to a gate of the thyristor 93, is mounted to the circuit substrate 92. This by-pass circuit 90-1 bypasses an electric current, which is supplied from the main capacitor 13 and flows via the arc tube 16_1, during the flowing of the electric current in the arc tube 16_1 so as to stop the electric current flowing in the arc tube 16_1. Further, a light adjusting circuit 95, which detects timing that a light of a predetermined amount is emitted from the arc tube 16_1 by means of the electric current flowing in the arc tube 16_1 so as to instruct the by-pass circuit 90_1 about the by-pass of the electric current, is mounted to the circuit substrate 92. This light adjusting circuit 95 is composed of a light receiving sensor 95_1, a capacitor 952, a switch element 95_3, an amplifier 95_4, a variable resistor 95-5, a comparator 95_6 and a trigger pulse generator 95_7. The light receiving sensor 95_1 receives a flashlight from the arc tube 16_1. The capacitor 95_2 stores electric charges corresponding to an amount of the light received by the light receiving sensor 95_1. The switch element 95_3 is controlled into the on-state before a flashlight is generated from the arc tube 16_1 so as to discharge residual electric charges in the capacitor 95_2. On the contrary, the switch element JJ5_3 is controlled into the off-state at the time when the flashlight is generated so as to allow the capacitor 95_2 to store electric charges. The amplifier 9 5_4 amplifies a voltage according to the electric charges of the capacitor 95_2. The variable resistor 9 5_5 sets a threshold value according to a film sensitivity, iris , desirable light and shade and the like. The comparator 9 5_6 inputs the voltage from the amplifier 95_4 and the threshold value set in the variable resistor 95_5, and when the voltage from the amplifier 9 5_4 exceeds the threshold value, the comparator 95_6 outputs a signal of 'H' level. The trigger pulse generator 95_7 receives the signal of 'H' level from the comparator 95_6 and outputs a trigger pulse. Next, there will be explained below an operation of the flashlight generating circuit 90. Since the operation during the time when the trigger switch 81 is closed and the flashlight is generated from the arc tube 16_1 is the same as the operation in the above-mentioned flashlight generating circuit 80, the description thereof is omitted. When the flashlight is generated from the arc tube 16_1, the light receiving sensor 95_1 receives the flashlight, and electric charges according to an amount of the received light are stored in the capacitor 95_2. The amplifier 95_4 amplifies a voltage according to the electric charges. The amplified voltage is input into a positive phase ( + ) terminal of the voltage comparator 95_6 . The threshold value is input into an opposite phase (-) terminal of the comparator 95_6. The comparator 95_6 compares the voltage with the threshold value, and when the voltage from the amplifier.95_4 exceeds the threshold value, outputs a signal of 'H' level to the trigger pulse generator 95_7. As a result, a trigger pulse is output from the trigger pulse generator 95_7. The trigger pulse output from the trigger pulse generator 95_7 is input into the gate of the thyristor 93. The thyristor 93 is then in the on-state, and the electric power stored in the main capacitor 13 is bypassed successively via the ( + ) side of the main capacitor 13, the connection terminal 91_1, the connection terminal 921, the thyristor 93, the connection terminal 922, the connection terminal 91_2, the primary side winding 16_3a of the trigger coil 163 and the (-) side of the main capacitor 13. Since the electric current, which is supplied from the main capacitor 13 and flows via the arc tube 16_1, flows in the by-pass circuit 90_1, the electric current flowing in the arc tube 16_1 is stopped so that the light emission is stopped. Here, since the primary side winding 16_3a of the trigger coil 16_3 serves as a choke coil, an electric current with a comparatively large peak value is prevented from flowing in the thyristor 93. - In the flashlight generating circuit 90 of the present embodiment, since the primary side winding 16_3a of the trigger coil 16_3 and the main capacitor 13 are arranged in series, when the flashlight is generated from the arc tube 16_1, the primary side winding 16_3a suppresses the peak value of the electric current flowing in the arc tube 16_1. As a result, a gentler light emission curve can be obtained, and when a light amount is controlled, the peak value of the electric current flowing in the thyristor 93 can be suppressed. For this reason, the thyristor 93, which can withstand a comparatively small electric current and has a small dimension and is inexpensive, can be adopted. Moreover, since the light adjusting circuit 95 is provided, the automatically adjusted flashlight generating apparatus, which controls a flashlight so that its emission is stopped at the time of reaching a predetermined light amount, can be realized. Further, in the flashlight generating circuit 90 of the present embodiment, the circuit substrate 92 to which the by-pass circuit 90_1 and the light adjusting circuit 95 are mounted is detachably connected to the circuit substrate 91 to which the arc tube 16_1 and the like is mounted. For this reason, when a camera, which is constituted by incorporating a normal flash apparatus which does not stop a flashlight during emission, and a camera, which is constituted by incorporating the automatically adjusted flashlight generating apparatus (auto-flash apparatus) for controlling a flashlight so that its emission is stopped at the time of reaching a predetermined light amount, are manufactured, the circuit substrate 91 and the circuit substrate 92 can be manufactured individually-. As a result, parts are commonly used so that the manufacturing process is simplified and the troublesome of product management is reduced. Moreover, a structure, that an adaptor into which the circuit substrate 92 is incorporated is attached to a housing of the camera into which the normal flash apparatus is incorporated, is adopted, a camera having an auto-flash apparatus^ can be realized easily. Here, the flashlight generating circuit 90 of the present embodiment was described in relation to the example that the thyristor 93 is controlled by a signal from the light adjusting circuit 95, but it is not limited to this example, and the thyristor 93 may be controlled by a signal according to guide number. Fig. 11 is a diagram showing a flashlight generating circuit according to a tenth embodiment of the present invention. A flashlight generating circuit 100 show in Fig. 11 is+ provided with a circuit substrate 101, to which a resistance element 102 arranged in series between the ( + ) side of the main capacitor 13 and the anode 16_la of the arc tube 16_1 is mounted. Moreover, the thyristor 93 is arranged between the connection point between the resistance element 102 and the anode 16_la of the arc tube 16_1 and the cathode 16_lb of the arc tube 16_1 via connection terminals 101_1 and 9 2_1 and connection terminals 101_2 and 92_2. These resistance element 102 and the thyristor 93 correspond to the by-pass circuit of the present invention. Since the flashlight generating circuit 100 of the present embodiment has the resistance element 102 and the thyristor 93 arranged in such a manner, when a flashlight is generated from the arc tube 16_1, both the primary side winding 16_3a and the resistance element 102 suppress a peak value of an electric current flowing in the arc tube 16_1 so that a gentler light emission curve is obtained. At the same time, when the flashlight from the arc tube 16_1 is stopped during the emission, both the primary side winding 16_3a and the resistance element 102 suppress a peak value of an electric current flowing in the thyristor 93. Fig. 12 is a diagram showing a flashlight generating circuit according to an eleventh embodiment of the present invention. A flashlight generating circuit 110 shown in Fig. 12 has a resistance element 111 and a thyristor 93 for controlling on/off state of a by-pass which are arranged in series between the anode 16_la and the cathode 16_lb of the arc tube 161 via the connection terminals 91_1 and 92_1 and the connection terminals 91_2 and 922. These resistance element 111 and the thyristor 93 correspond to the by-pass circuit of the present invention. Since the flashlight generating circuit 110 of the present embodiment has the resistance element 111 and the thyristor 93 which are arranged in series, when a flashlight from the arc tube 16_1 is stopped during emission, the primary side winding 16_3a and the resistance element 111 suppress a peak value of an electric current flowing in the thyristor 93. Fig. 13 is a diagram showing a flashlight generating circuit according to a twelfth embodiment of the present invention. In a flashlight generating circuit 120 shown in Fig. 13, a series of pulse signals are input into an IGBT element 124 so as to be pulse-generated, and a flashlight is generated form the arc tube 16_1. When this flashlight generating circuit 120 is compared with the flashlight generating circuit 80 shown in Fig. 9, the trigger switch 81 is replaced by a thyristor 121. A gate of the thyristor 121 is connected to a resistance element 122 and a control terminal 123. Moreover, the IGBT (Insulated Gate Bipolar Transistor) element 124, in which a collector is connected to the cathode 16_lb of the arc tube 16_1 and an emitter is connected to the ( - ) side of the main capacitor 13 via the primary side winding 163a of the trigger coil 163, is arranged in a discharge loop L9. A gate of the IGBT element 124 is connected to the control terminal 125. In the flashlight generating circuit 120 having such a structure, at the first time that a power source of a camera is turned on, a control signal of 'L' level is input into the control terminal 123, and the thyristor 121 is in the off state. Moreover, an electric power from the internal battery 1 is stepped-up by the step-up circuit 11, and an electric power is stored in the main capacitor 13b via the diode 12, the main capacitor 13 and the primary side winding 16_3a of the trigger coil 16_3. Further, an electric power is stored also.in a trigger-use capacitor 16_2 via the diode 12, the resistance element 14, the trigger-use capacitor 16_2 and the primary side winding 16_3a of the trigger coil 16_3. Next, a trigger pulse is applied to the control terminal 123 in synchronization with the action of the shutter of the camera at the time of photography. Moreover, a series of pulse signals are input into the control terminal 125. Since the trigger pulse is applied to the control terminal 123, the thyristor 121 is in the on-state, and the electric power stored in the trigger-use capacitor 16_2 is discharged. An electric current flows in the primary side winding 16_3a, and an electromotive force is generated in the second side winding 16_3b. This electromotive force is applied to the side electrode 16_lc of the arc tube 16_1, and a xenon gas sealed in the arc tube 16_c is excited. Meanwhile, since a series of pulse signals are input also into the control terminal 125, the IGBT element 124 starts a switching operation according to the series of pulse signals. The electric power stored in the main capacitor 13 is discharged through the discharge loop L9 of the ( + ) side of the main capacitor 13, the anode 16_la, the cathode 16_lb, the IGBT element 124, the primary side winding 16_3a and the (-) side of the main capacitor 13, and a flashlight is generated form the arc tube 16_1. Here, since the primary side winding 16_3a of the trigger coil 16_3 and the main capacitor 13 are arranged in series , a peak value of a pulse current flowing in the IGBT element 124 is suppressed by the primary side winding 16_3a. Therefore, a choke coil is not required, and thus the IGBT element 124 with comparatively small allowable current can be adopted. As a result, the cost can be reduced. WE CLAIM : 1. A flashlight generating circuit, comprising : a step-up circuit; a main capacitor for storing an electric power which is stepped up by said step-up circuit; an arc tube for generating a light by means of the electric power discharged from said main capacitor; and a trigger circuit which is provided with a trigger-use capacitor and a trigger coil in which a primary side winding is connected to said trigger-use capacitor and an electric power flowing in said trigger-use capacitor is transmitted to a secondary side winding so that a trigger voltage is applied to said arc tube, wherein the primary side winding of said trigger coil as well as said arc tube are arranged in a discharge loop where the electric power discharged from said main capacitor flows. 2. The flashlight generating circuit as claimed in claim 1, wherein the primary side winding of said trigger coil is arranged on an anode side of said arc tube. 3. The flashlight generating circuit as claimed in claim 1, wherein the primary side winding of said trigger coil is arranged on a cathode side of said arc tube. 4. The flashlight generating circuit as claimed in claim 1, wherein a non-contact switch is provided in said discharge loop. 5. The flashlight generating circuit as claimed in claim 4, having a by-pass-use diode for allowing an electric current caused by a back electromotive force generated in the primary side winding of said trigger coil to bypass when said non-contact switch is changed from an on-state into an off-state. 6. The flashlight generating circuit as claimed in claim 1, wherein said trigger-use capacitor applies a voltage with polarity for helping a flow of the electric force discharged from said main capacitor to between the anode and the cathode of said arc tube at timing that a trigger voltage is applied to said arc tube. 7. The flashlight generating circuit as claimed in claim 1, having a voltage application- use capacitor for applying a voltage with polarity for helping a flow of the electric force discharged from said main capacitor to between the anode and the cathode of said arc tube at timing that a trigger voltage is applied to said arc tube. 8. The flashlight generating circuit as claimed in claim 1, wherein said voltage application-use capacitor applies a voltage at the time when said main capacitor and said voltage application-use capacitor are connected in series to between the anode and the cathode of said arc tube at the timing that the trigger voltage is applied to said arc tube at the timing that the trigger voltage is applied to said arc tube in cooperation with said main capacitor. 9. The flashlight generating circuit as claimed in claim 1, wherein said trigger-use capacitor is kept in a discharged state before the timing that a trigger voltage is applied to said arc tube, and applies a trigger voltage to said arc tube via said trigger coil after the electric power discharged from said main capacitor passes therethrough. 10. The flashlight generating circuit as claimed in claim 1, wherein the primary side winding of said trigger coil and said main capacitor are arranged in series. 11. The flashlight generating circuit as claimed in claim 1, having a by-pass circuit for bypassing an electric current which is supplied from said main capacitor and flows via said arc tube during the flowing of the electric current in said arc tube so as to stop the electric current flowing in said arc tube. 12. The flashlight generating circuit as claimed in claim 11, wherein said by-pass circuit has : a resistance arranged in series with said arc tube; and a switch element which is arranged parallel with said arc tube between a connection node, arranged between said resistance and one terminal of said arc tube, and the other terminal of said arc tube. 13. The flashlight generating circuit as claimed in claim 11, wherein said by-pass circuit has a resistance and a switch element for controlling on/off state of by-pass which are arranged in series. 14. The flashlight generating circuit as claimed in claim 11, having a light adjusting circuit for detecting timing that a predetermined amount of a light is emitted from said arc tube according to the electric current flowing in said arc tube and instructing said by-pass circuit to bypass the electric current. 15. The flashlight generating circuit as claimed in claim 11, wherein said by-pass circuit is detachably connected parallel with said arc tube. 16. A flashlight generating circuit, substantially as herein described, with particular reference to and, as illustrated in the accompanying drawings. 17. A camera with a flashlight generating circuit, being provided therein, said circuit being as claimed in any of the preceding claims. In a flashlight generating circuit, a primary side winding 16_3a of a trigger coil 163 and a arc tube 161 are arranged in a discharge loop L1 where an electric force discharged from a main capacitor 13 flows, a voltage of an internal battery 1 is stepped up to a predetermined voltage by a step-up circuit 11, an electric power is stored in the main capacitor 13 and a trigger-use capacitor 16_2, a trigger switch 15 is closed so that an electric current is allowed to flpw in the primary side winding 16_3a so that a light is emitted from the arc tube 16_1 by a trigger voltage from a secondary side winding 16_3b.

Documents:

630-cal-2000-granted-abstract.pdf

630-cal-2000-granted-claims.pdf

630-cal-2000-granted-correspondence.pdf

630-cal-2000-granted-description (complete).pdf

630-cal-2000-granted-drawings.pdf

630-cal-2000-granted-examination report.pdf

630-cal-2000-granted-form 1.pdf

630-cal-2000-granted-form 18.pdf

630-cal-2000-granted-form 2.pdf

630-cal-2000-granted-form 3.pdf

630-cal-2000-granted-form 5.pdf

630-cal-2000-granted-gpa.pdf

630-cal-2000-granted-priority document.pdf

630-cal-2000-granted-reply to examination report.pdf

630-cal-2000-granted-specification.pdf

630-cal-2000-granted-translated copy of priority document.pdf