Ultraviolet irradiation device, lighting circuit

Abstract

The present invention provides an ultraviolet light irradiation device and a lighting circuit that can stably illuminate an ultraviolet light irradiation section. [Solution] The lighting circuit includes a DC power supply, a transformer having a primary winding and a secondary winding, and a switching element, configured to generate an electromotive force in the secondary winding of the transformer by switching between the ON and OFF states of the switching element; an ultraviolet light irradiation unit connected to the secondary winding of the transformer, having a first electrode and a second electrode, with the tube wall of a light-emitting tube filled with light-emitting gas and a first space with changing impedance interposed between the first electrode and the second electrode; a detection unit that directly or indirectly detects the impedance of the first space; and a control unit that controls the frequency for switching between the ON and OFF states of the switching element based on the impedance of the first space detected by the detection unit, or parameters related to the impedance of the first space.

Description

Technical Field

[0001] The present invention relates to an ultraviolet light irradiation device and a lighting circuit mounted on the ultraviolet light irradiation device.

Background Art

[0002] In recent years, methods using ultraviolet light have been increasingly used in semiconductor manufacturing, surface treatment of resin materials, etc. For example, in Patent Document 1 below, a method of hydrophilizing the surface of a resin material by irradiating the surface of the resin material with ultraviolet light emitted from a xenon excimer lamp in a humid environment is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The inventors of the present invention have been earnestly studying further improvements to an ultraviolet light irradiation device applicable to the method described in Patent Document 1 above, and have noticed that in a conventional ultraviolet light irradiation device, during the process of treating a resin material, the lighting state of the ultraviolet light irradiation part gradually becomes unstable, or the ultraviolet light irradiation part may turn off. And the inventors of the present invention have also found that such a phenomenon of unstable lighting occurs not only in a humid environment but also in an environment where the atmospheric pressure changes.

[0005] In view of the above problems, an object of the present invention is to provide an ultraviolet light irradiation device and a lighting circuit capable of stably lighting an ultraviolet light irradiation part.

Means for Solving the Problems

[0006] The ultraviolet light irradiation device of the present invention is A lighting circuit comprising a DC power supply, a transformer having a primary winding and a secondary winding, and at least one switching element, wherein the switching element switches between an ON state and an OFF state to switch the supply and cessation of current from the DC power supply to the primary winding of the transformer, or to change the direction of the current flowing through the primary winding, thereby generating an electromotive force in the secondary winding of the transformer. A UV light irradiation unit connected to the secondary winding of the transformer, having a first electrode and a second electrode, wherein the tube wall of a light-emitting tube filled with light-emitting gas and a first space where the impedance changes are interposed between the first electrode and the second electrode, A detection unit that directly or indirectly detects the impedance of the first space, The system is characterized by comprising a control unit that controls the frequency for switching between the ON and OFF states of the switching element based on the impedance of the first space detected by the detection unit, or a parameter related to the impedance of the first space.

[0007] The above ultraviolet light irradiation device is At least a portion of the second electrode may be in contact with the wall of the discharge tube.

[0008] Furthermore, in the above ultraviolet light irradiation device, The aforementioned first space may be configured such that its impedance changes as the atmospheric pressure or humidity within the space changes.

[0009] Here, "direct detection" refers to directly measuring the impedance of the first space, for example, using an instrument for measuring impedance. "Indirect detection" refers to indirectly deriving the change in the impedance of the first space by measuring, for example, the voltage between predetermined nodes in the primary or secondary windings of a transformer, or the current or power flowing through predetermined nodes.

[0010] The ultraviolet light irradiation device with the above configuration controls the frequency at which the switching element switches based on the signal from the detection unit. Specifically, the ultraviolet light irradiation device with the above configuration controls the ON time, OFF time, or the period between the ON and OFF states of the switching element.

[0011] The inventors noticed that the impedance between electrodes changes with changes in humidity and atmospheric pressure in the first space. They then discovered that this change in impedance affects the stability of the illumination of the ultraviolet light irradiation section, leading to the present invention.

[0012] In this configuration, the ultraviolet light irradiation device can be controlled to reduce the load on the circuit even when the impedance of the first space changes, by controlling the ON time of the switching element to be relatively shorter than the OFF time when the impedance of the first space decreases (for example, when the air pressure in the first space decreases), or by controlling the frequency at which the ON state and OFF state are switched to a lower value.

[0013] Furthermore, factors that can cause changes in the impedance of the first space include changes in the composition ratio of materials within the first space, temperature, humidity, atmospheric pressure, and the flow velocity of the gas passing through it. Among these, changes in atmospheric pressure and humidity are particularly likely to fluctuate significantly not only in human living spaces but also in specialized equipment that performs ultraviolet light irradiation, such as semiconductor manufacturing equipment, and are thought to greatly affect the operation of the ultraviolet light irradiation section.

[0014] Therefore, with the above configuration, the power supplied between the first electrode and the second electrode is feedback-controlled according to the impedance of the first space. In other words, the ultraviolet light irradiation unit is lit by supplying power in accordance with the change in the impedance of the first space. As a result, the ultraviolet light irradiation device operates stably.

[0015] The above ultraviolet light irradiation device is The lighting circuit may be a push-pull, full-bridge, or half-bridge circuit.

[0016] For illuminating the ultraviolet light irradiation section, a lighting method can be employed in which voltage is applied to the ultraviolet light irradiation section from a DC power supply via a transformer. Examples of specific circuit configurations include the flyback method, push-pull method, half-bridge method, and full-bridge method.

[0017] As described above, when the ultraviolet light irradiation device irradiates an object to be treated with ultraviolet light, that is, when the ultraviolet light irradiation unit is turned on, a current path is formed in which the ultraviolet light irradiation unit and a space with a higher impedance compared to the wiring and other components that make up the electrical circuit are connected in series.

[0018] In particular, when a relatively large output is required from the various lighting circuit methods described above, push-pull, half-bridge, or full-bridge configurations are adopted.

[0019] Therefore, the inventors were considering constructing an ultraviolet light irradiation device in which a push-pull, half-bridge, or full-bridge lighting circuit, which is commonly used in conventional ultraviolet light irradiation devices, is applied to the ultraviolet light irradiation section.

[0020] However, in ultraviolet light irradiation devices employing the above method, as mentioned above, the impedance of the first space sometimes caused the ultraviolet light irradiation section to become unstable or fail to light up at all.

[0021] Here, push-pull, half-bridge, and full-bridge lighting circuits are circuits that switch the direction of the current generated in the primary winding of a transformer by switching the ON and OFF states of a switching element, thereby generating an electromotive force in the secondary winding. Furthermore, these circuit configurations are such that a closed circuit is always formed, except for the moment when the switching element is switched.

[0022] In many cases, the impedance of the first space changes due to changes in air pressure, humidity, etc. within the space. Also, the first space may not reach an equilibrium state throughout, and the impedance may locally increase or decrease.

[0023] Here, assuming that the impedance in the first space becomes low, an excessive current flows through the ultraviolet irradiation unit connected to the secondary winding. As a result, the ultraviolet light irradiation unit is likely to experience abnormal discharge. In this case, the lighting circuit enters an overload state, and damage is likely to occur in the elements, wiring, etc. that make up the circuit due to the occurrence of abnormal heat generation and the like. Thus, due to the change in the impedance of the first space, problems such as the lighting state of the ultraviolet light irradiation unit becoming unstable or the ultraviolet light irradiation unit not lighting up occur.

[0024] The inventor who identified the above causes came up with a new idea of controlling the electromotive force generated in the secondary winding of the transformer according to the fluctuation of the impedance of the first space.

[0025] A current corresponding to the impedance in the first space detected by the detection unit flows through the primary winding of the transformer. According to the current flowing through the primary winding of the transformer, the electromotive force generated in the secondary winding changes. Therefore, with the above configuration, even if the impedance of the first space fluctuates, power for lighting the ultraviolet light irradiation unit is stably supplied between the electrodes of the ultraviolet light irradiation unit. Therefore, the ultraviolet light irradiation device with the above configuration can stably generate ultraviolet light in the ultraviolet light irradiation unit regardless of the state of the first space.

[0026] Also, the above ultraviolet light irradiation device The lighting circuit may be a flyback method circuit.

[0027] Unlike push-pull systems, the flyback lighting circuit switches between an open and closed circuit by switching the ON and OFF states of a switching element. In other words, when the discharge in the ultraviolet light irradiation area stops and an electromotive force is generated in the primary winding, the switching element is in the OFF state.

[0028] Furthermore, the electromotive force generated in the primary winding after the ultraviolet light irradiation section is stopped is almost entirely consumed by heat generation in the circuit elements and charge release to the ground terminal when the switching element is switched from the OFF state to the ON state. For this reason, in a flyback type lighting circuit, the electromotive force generated in the primary winding has little effect on the electromotive force generated in the secondary winding.

[0029] Therefore, with the above configuration, the UV light irradiation device is less susceptible to changes in the impedance of the first space in terms of the voltage applied to the UV light irradiation section. In other words, the UV light irradiation device with the above configuration can more stably illuminate the UV light irradiation section regardless of the impedance of the first space.

[0030] In the above ultraviolet light irradiation device, The detection unit may be connected to the secondary winding of the transformer.

[0031] The detection unit is connected to the secondary winding of the transformer, thereby being connected in series or parallel to the circuit via the first space. Therefore, compared to a configuration in which it is connected to the primary winding side, which is not directly connected to the first space, the above configuration allows the detection unit to more accurately detect the impedance of the first space.

[0032] Switching control of the switching element in response to the detected impedance is performed, for example, based on a data table relating the impedance of the first space calculated in advance and the voltage required to light up the ultraviolet light irradiation unit. In such a case, if the detected impedance of the first space and the actual impedance of the first space deviate significantly, the voltage applied to the ultraviolet light irradiation unit will also deviate significantly from the ideal value, and in the worst case, it may fail to light up.

[0033] In other words, with the above configuration, the switching control of the switching element is set to a frequency suitable for the impedance of the actual first space, so that the ultraviolet light irradiation section lights up reliably and stably.

[0034] In the above ultraviolet light irradiation device, The detection unit may be connected to the primary winding of the transformer.

[0035] When the detection unit is connected to the primary winding side of the transformer, the detection unit is not directly connected to the circuit via the first space. Therefore, the electromotive force generated in the secondary winding side of the transformer is not partially consumed by the detection unit.

[0036] In other words, with the above configuration, the electromotive force generated in the secondary winding of the transformer is directly used to light the ultraviolet light irradiation section, thus reducing energy loss on the secondary winding side and making circuit design relatively easy.

[0037] The lighting circuit of the present invention is This is the lighting circuit provided in the above-mentioned ultraviolet light irradiation device. [Effects of the Invention]

[0038] According to the present invention, an ultraviolet light irradiation device and a lighting circuit are realized that can stably light up an ultraviolet light irradiation section. [Brief explanation of the drawing]

[0039] [Figure 1A]This is a schematic diagram showing the configuration of one embodiment of an ultraviolet light irradiation device. [Figure 1B] This is a schematic diagram showing the configuration of one embodiment of an ultraviolet light irradiation device. [Figure 1C] Figure 1B is a cross-sectional view of the ultraviolet light irradiation device, as seen in the direction of the tube axis of the discharge tube. [Figure 2] This is a schematic diagram showing the configuration of a lighting circuit in one embodiment. [Figure 3] This timing chart schematically shows an example of the time variation of the control signal, secondary voltage, and secondary current. [Figure 4] This diagram schematically shows the configuration of a lighting circuit in one embodiment. [Figure 5] This timing chart schematically shows an example of a control unit determination method based on the control signal, primary current, secondary voltage, time variation of the secondary current, and the detected voltage at the detection unit. [Figure 6] This timing chart schematically shows an example of the time variation of the control signal, primary current, secondary voltage, and secondary current. [Modes for carrying out the invention]

[0040] The ultraviolet light irradiation device and lighting circuit of the present invention will be described below with reference to the drawings. Note that the following drawings are schematic illustrations, and the numbers shown in the drawings do not necessarily correspond to the actual numbers.

[0041] Furthermore, the following explanation assumes that a change in atmospheric pressure within the first space causes a change in the impedance between the first and second electrodes, which will be described later. However, the change in impedance in this invention is not limited to changes in atmospheric pressure within the first space. Specifically, changes in the composition ratio of materials, temperature, humidity, atmospheric pressure, and flow velocity of the gas passing through the first space are also conceivable.

[0042] [First Embodiment] First, the configuration of the first embodiment of the ultraviolet light irradiation device 1 will be described. Figure 1A is a schematic diagram showing the configuration of the first embodiment of the ultraviolet light irradiation device 1. As shown in Figure 1A, the ultraviolet light irradiation device 1 comprises an ultraviolet light irradiation unit 10 and a lighting circuit 20. The ultraviolet light irradiation unit 10 comprises a discharge tube 11, a chamber 12, and a first electrode 13a.

[0043] As shown in Figure 1A, the discharge tube 11 has a rod-shaped first electrode 13a positioned within its inner discharge space 11a. The first electrode 13a is connected to the first electrode terminal a1 of the lighting circuit 20 via a pinch seal portion 14 formed on one end of the discharge tube 11.

[0044] The discharge tube 11 is a tube made of quartz glass, and xenon (Xe) is sealed as a luminescent gas in the discharge space 11a inside the discharge tube 11. The luminescent gas sealed in the discharge space 11a inside the discharge tube 11 can be arbitrarily selected depending on the treatment being performed. Other specific examples include gases containing group 18 elements such as xenon (Xe), argon (Ar), and krypton (Kr), or gases containing group 17 elements and the aforementioned group 18 elements such as fluorine (F), chlorine (Cl), and bromine (Br).

[0045] Furthermore, the material of the discharge tube 11 is appropriately selected according to the wavelength range of ultraviolet light that you want to irradiate the object to be processed.

[0046] Chamber 12 has a first space A1 formed inside which an object to be processed (not shown) to be irradiated with ultraviolet light is contained, and the air pressure inside the first space A1 is controlled by a pump (not shown) connected via valves (15a, 15b). Chamber 12 is a container whose side walls are made of a conductive metal, and as shown in Figure 1A, these side walls are connected to the second electrode terminal a2 of the lighting circuit 20 and are also electrically grounded. In other words, in the first embodiment, chamber 12 serves as both a container for containing the object to be processed and a function of the second electrode 13b.

[0047] Furthermore, the shape of the chamber 12 is not limited to a cylindrical shape as shown in Figure 1A. Also, the position and orientation of the light-emitting tube 11 inside the chamber 12 are not limited to the positional relationship shown in Figure 1A. Additionally, a platform or the like for placing a predetermined object to be processed may be installed inside the chamber 12.

[0048] In the ultraviolet light irradiation unit 10, with the object to be processed contained within the first space A1 of the chamber 12, when the voltage necessary for lighting is applied from the lighting circuit 20 to the electrodes (13a, 13b), the voltage is applied via the discharge space 11a, the tube wall of the discharge tube 11, and the first space A1. As a result, a discharge occurs in the discharge space 11a of the discharge tube 11, which is positioned between the electrodes (13a, 13b). In other words, this ultraviolet light irradiation unit 10 is a dielectric barrier discharge in which a discharge occurs when a voltage is applied to the discharge space 11a via the discharge tube 11, which is made of a dielectric material, and the first space A1. When a discharge occurs in the discharge tube 11, ultraviolet light is generated in the discharge space 11a of the discharge tube 11, and this ultraviolet light is irradiated onto the object to be processed contained within the first space A1.

[0049] In the first embodiment, when irradiating the object to be processed in the first space A1 with ultraviolet light, the valves (15a, 15b) are opened and the processing is carried out while gradually reducing the pressure with a pump. However, the ultraviolet light irradiation device 1 may be configured to irradiate with ultraviolet light while gradually reducing the pressure by opening and closing the valves (15a, 15b). Furthermore, the valves (15a, 15b) may be connected to a humidifier, heater, blower, cylinder that discharges a predetermined gas, etc., and the composition ratio of the substances in the first space A1, temperature, humidity, flow rate of the gas passing through, etc. may be changed.

[0050] Furthermore, as described above, the present invention may also be applied to an apparatus that processes a target object while humidifying the first space A1, changing the concentration of a predetermined gas, or changing the flow rate of the gas being passed through, rather than while reducing the pressure within the space.

[0051] It should be noted that the configuration of the ultraviolet light irradiation unit 10 applicable to the present invention is not limited to the embodiment shown in Figure 1A. For example, although the first electrode 13a is located inside the discharge space 11a of the discharge tube 11, it may also be located outside the discharge space 11a.

[0052] Furthermore, various configurations can be adopted for the discharge space 11a of the discharge tube 11, in which it is positioned between the first electrode 13a and the second electrode 13b. The first electrode 13a and the second electrode 13b, which is positioned spaced apart from the discharge tube 11, are separated by a first space A1 having a predetermined impedance, which is interposed between the discharge tube 11 and the second electrode 13b to apply a voltage to the discharge space 11a.

[0053] Furthermore, the configuration of the ultraviolet light irradiation unit is not limited to the above, and may be, for example, an excimer lamp with a structure also called a flat tube shape, which is fixed inside the chamber 12 and has a flat cross-section when cut by a plane perpendicular to the tube axis, with the first electrode and the second electrode arranged to face each other via a discharge tube. In an excimer lamp with this configuration, it is sufficient that at least one of the electrodes has a portion that is separated from the wall surface of the discharge tube, and the gap between the electrode in that portion and the discharge tube becomes the first space A1 in which the impedance gradually changes. Such an ultraviolet light irradiation unit can be applied, for example, to cases in which a predetermined object is treated by exposing it to ozone or radicals generated by irradiation with ultraviolet light, or when the object to be treated is a gas that also flows between the discharge tube and the electrodes.

[0054] Next, the details of the lighting circuit 20 will be described. Figure 2 is a schematic diagram showing the configuration of the lighting circuit 20 in the first embodiment. The lighting circuit 20 is an example of a circuit configuration called a push-pull type, and as shown in Figure 2, it comprises a DC power supply 21, two switching elements (22a, 22b), a detection unit 26, and a transformer 30.

[0055] The transformer 30 includes a primary winding L1 and a secondary winding L2. Of the terminals on the primary winding L1 of the transformer 30, one end is connected to the switching element 22a and the other end is connected to the switching element 22b. In addition, the intermediate node L1c of the primary winding L1 is connected to the positive terminal of the DC power supply 21.

[0056] For the purposes of the following explanation, the primary winding L1 is distinguished as shown in Figure 2, into winding L1a, which is on the switching element 22a side when viewed from the intermediate node L1c, and winding L1b, which is on the switching element 22b side when viewed from the intermediate node L1c. However, the primary winding L1 does not necessarily have to consist of two windings (L1a, L1b); for example, it may consist of a single winding, with the midpoint of the winding portion being the intermediate node L1c.

[0057] The switching elements (22a, 22b) of the first embodiment are composed of field-effect transistors (FETs).

[0058] Note that the switching elements (22a, 22b) may be other types of switching elements besides field-effect transistors (FETs).

[0059] The DC power supply 21 may be configured, for example, by an AC / DC converter that converts a commercial power supply (not shown) into AC / DC.

[0060] The lighting circuit 20 of the first embodiment includes a control unit 24 for performing ON / OFF control of the switching elements (22a, 22b). The control unit 24 only needs to be capable of outputting a control signal G1(t) to the switching element 22a and a control signal G2(t) to the switching element 22b.

[0061] In the first embodiment, the detection unit 26 detects the current flowing on the low-voltage side of the secondary winding L2. Specifically, it can detect the current flowing through a resistor provided within the detection unit 26 by converting it into a voltage value. The detection unit 26 then outputs a detection signal D1, which includes the measured current value, to the control unit 24.

[0062] Here, the current flowing through the primary winding L1 or the secondary winding L2 changes in accordance with the change in impedance of the first space A1 interposed between the electrodes (13a, 13b), which is caused by the change in atmospheric pressure in the first space A1. In other words, as the atmospheric pressure gradually decreases, the impedance between the electrodes (13a, 13b) decreases, and the current flowing through the primary winding L1 or the secondary winding L2 increases. Therefore, by detecting the current flowing through the primary winding L1 or the secondary winding L2 with the detection unit 26, it is possible to indirectly detect the change in impedance of the first space A1 interposed between the electrodes (13a, 13b). As can be seen from this, the current flowing through the primary winding L1 or the secondary winding L2 is a parameter related to the impedance of the first space A1 interposed between the electrodes (13a, 13b).

[0063] Next, the operation of the lighting circuit 20 will be explained. Figure 3 is a timing chart that schematically shows an example of the time variation of the control signals (G1(t), G2(t)) and the secondary voltage V2.

[0064] The graph of the control signal G1(t) in Figure 3 shows that a high level indicates that the switching element 22a is being controlled to the ON state, and a low level indicates that the switching element 22a is being controlled to the OFF state. The graph of the control signal G2(t) in Figure 3 shows similar control for the switching element 22b.

[0065] The secondary voltage V2 shown in Figure 3 corresponds to the potential of the first electrode terminal a1 with respect to the potential of the second electrode terminal a2 in Figure 2. In the first embodiment, the second electrode terminal a2 is grounded.

[0066] The graphs showing voltage and current fluctuations illustrated in the drawings referenced in the following description, like the graph of the secondary voltage V2 in Figure 3, do not show offsets that do not affect the explanation of the main operation of the present invention, nor spike noise due to switching operation, and schematically represent an example of an ideal waveform. Furthermore, whether the secondary voltage V2 is configured to swing to the positive side or the negative side with respect to a predetermined voltage (0V in the first embodiment) may be set arbitrarily as appropriate depending on the specifications of the ultraviolet light irradiation unit 10 and the configuration of the lighting circuit 20.

[0067] When the control unit 24 starts operation, it switches the control signal G1(t) from a low level to a high level, switching the switching element 22 from the OFF state to the ON state. Then, the primary current I1a flows to the winding L1a side of the primary winding L1 of the transformer 30.

[0068] Subsequently, at time t2, a predetermined time has elapsed from time t1, the control unit 24 switches the output of the control signal G1(t) from a high level to a low level. As a result, the switching element 22a switches from the ON state to the OFF state, and the primary current I1a stops.

[0069] Next, at time t3, the control unit 24 switches the output of the control signal G2(t) from a low level to a high level. Then, the primary current I1b flows to the winding L1b side of the primary winding L1 of the transformer 30.

[0070] Subsequently, at time t4, a predetermined time has elapsed since time t3, the control unit 24 switches the output of the control signal G2(t) from a high level to a low level. As a result, the switching element 22b switches from the ON state to the OFF state, and the primary current I1b stops. From there, the control unit 24 repeats the above control.

[0071] Here, as shown in Figure 3, the control unit 24 derives the impedance of the first space A1 based on the current value of the secondary current I2 measured by the detection unit 26, and adjusts the frequency at which the above-described control is repeated according to the derived impedance. Specifically, at time t5, when the detection unit 26 detects that the impedance of the first space A1 has decreased, the control unit 24 executes control to lower the frequency at which the control signals (G1(t), G2(t)) are switched in accordance with the decrease in the impedance of the first space A1.

[0072] This control ensures that the ultraviolet light irradiation unit 10 is continuously supplied with power suitable for lighting, regardless of changes in the impedance of the first space A1 interposed between the electrodes (13a, 13b).

[0073] As described above, with the above configuration, even if the impedance of the first space A1 fluctuates, power for generating ultraviolet light is stably supplied between the electrodes (13a, 13b) of the ultraviolet light irradiation unit 10. Therefore, the load on the lighting circuit 20 is reduced. Furthermore, the ultraviolet light irradiation device 1 with the above configuration can stably generate ultraviolet light in the ultraviolet light irradiation unit 10 regardless of the impedance of the first space A1.

[0074] In the first embodiment, the ultraviolet light irradiation unit 10 is equipped with a chamber 12 with metal side walls, and the chamber 12 itself also functions as the second electrode 13b. However, the second electrode 13b may be provided separately from the chamber 12. For example, the outer wall surface of the chamber 12 may be made of a dielectric material and the second electrode 13b may be provided on this outer wall surface, or metal valves (15a, 15b) may be used and configured so that at least one of the valves (15a, 15b) also functions as the second electrode 13b.

[0075] Figure 1B is a schematic diagram showing the configuration of another embodiment of the ultraviolet light irradiation device 1, different from that shown in Figure 1A, and Figure 1C is a cross-sectional view of the ultraviolet light irradiation unit 10 shown in Figure 1B, viewed in the direction of the tube axis of the discharge tube. As shown in Figures 1B and 1C, the ultraviolet light irradiation device 1 may consist of a discharge tube 11, a first electrode 13a arranged inside the discharge tube 11, and a second electrode 13b provided on the outer wall surface of the discharge tube 11.

[0076] In the ultraviolet light irradiation device 1 with the configuration shown in Figures 1B and 1C, the discharge tube 11 and the second electrode 13b are configured to be separated in some areas and in contact in others. As shown in Figure 1C, the space formed by the separation of the discharge tube 11 and the second electrode 13b corresponds to the first space A1.

[0077] Furthermore, in the first embodiment, the second electrode 13b is grounded, but if no particular problems arise with the electrical stability of the ultraviolet light irradiation section 10, the second electrode 13b does not need to be grounded.

[0078] Furthermore, although the lighting circuit 20 was configured as a push-pull circuit in the first embodiment, the lighting circuit 20 can also be configured as a half-bridge or full-bridge circuit, similar to the push-pull circuit, which changes the direction of the primary current I1 flowing through the primary winding L1 to generate an electromotive force in the secondary winding L2.

[0079] [Second Embodiment] The configuration of the second embodiment of the ultraviolet light irradiation device 1 of the present invention will be described, focusing on the differences from the first embodiment.

[0080] Figure 4 is a schematic diagram showing the configuration of the lighting circuit 20 in the second embodiment. The lighting circuit 20 is an example of a circuit configuration called a flyback type, and as shown in Figure 4, it comprises a DC power supply 21, a switching element 22, a control unit 24, a detection unit 26, and a transformer 30.

[0081] The transformer 30 includes a primary winding L1 and a secondary winding L2. Of the terminals on the primary winding L1 of the transformer 30, the first terminal b1 is connected to the positive terminal of the DC power supply 21, and the second terminal b2 is connected to the negative terminal of the DC power supply 21 via a switching element 22.

[0082] In the second embodiment, the switching element 22 is composed of a field-effect transistor (FET), and a parasitic diode 23 is formed, with the anode connected to the negative terminal of the DC power supply 21 and the cathode connected to the primary winding L1 of the transformer 30. In the second embodiment, this parasitic diode 23 functions as a regenerative circuit.

[0083] Note that the switching element 22 may be an element other than a field-effect transistor (FET). Furthermore, the switching element 22 may be an IGBT or relay element without a parasitic diode 23, and the regenerative circuit may be configured by connecting a single diode element in parallel with the switching element 22.

[0084] As shown in Figure 4, the detection unit 26 of the second embodiment includes a resistor R1 connected in series with the switching element 22, and outputs a detection signal D1 that includes the voltage value generated between the terminals of the resistor R1 when the primary current I1 flowing through the switching element 22 flows. However, the configuration of the detection unit 26 is not limited to this configuration. For example, the detection unit 26 may be configured to include a shunt resistor and detect the current value of the primary current I1 by measuring the divided current value.

[0085] Furthermore, in order to prevent the regenerative current flowing through the primary winding L1 from being consumed by the detection unit 26, the detection unit 26 may be equipped with a resistor R1 and a diode element 26a whose anode terminal is connected to the negative terminal side of the DC power supply 21 and whose cathode terminal is connected to the positive terminal side of the DC power supply 21.

[0086] As a result, when the impedance of the first space A1 interposed between the electrodes (13a, 13b) changes significantly, the detection unit 26 detects the impedance fluctuation, and a detection signal D1 is output to the control unit 24. Based on the information contained in the detection signal D1, the control unit 24 controls the ON / OFF state of the switching element 22. In other words, when the impedance of the first space A1 fluctuates violently, the load on the circuit on the primary winding L1 side can be minimized. Therefore, the ultraviolet light irradiation device 1 with this configuration has a wider tolerance range for the impedance of the first space A1 compared to other configurations.

[0087] Next, the operation in the second embodiment will be described. Figure 5 is a timing chart schematically showing an example of a determination method of the control unit 24 according to the control signal G(t), primary current I1, secondary voltage V2, the time change of the secondary current I2, and the detected voltage in the detection unit 26. In the graph of the control signal G(t) in Figure 5, a high level indicates that the switching element 22 is controlled to the ON state, and a low level indicates that the switching element 22 is controlled to the OFF state.

[0088] The secondary voltage V2 shown in Figure 5 corresponds to the potential of the first electrode terminal a1 with respect to the potential of the second electrode terminal a2 in Figure 4. In the second embodiment, the second electrode terminal a2 is grounded.

[0089] The secondary current I2 shown in Figure 5 corresponds to the current flowing through the secondary winding L2 of the transformer 30 in Figure 4.

[0090] When the control unit 24 starts operation, it switches the control signal G(t) from a low level to a high level, thereby switching the switching element 22 from the OFF state to the ON state.

[0091] As shown in Figure 5, after the switching element 22 switches from the OFF state to the ON state, the primary current I1 flowing through the primary winding L1 of the transformer 30 gradually increases.

[0092] After a predetermined time has elapsed, the control unit 24 switches the output of the control signal G(t) from a high level to a low level. As a result, the switching element 22 switches from the ON state to the OFF state.

[0093] When the switching element 22 switches from the ON state to the OFF state, the primary current I1 stops flowing. Then, in response to the sharp fluctuation of the primary current I1, an electromotive force is generated in the secondary winding L2, and power is supplied to the ultraviolet light irradiation section 10.

[0094] At this time, an electromotive force is generated in the primary winding L1 of the transformer 30 by the energy not consumed by the ultraviolet light irradiation unit 10, and a regenerative current is generated associated with this electromotive force. In the second embodiment, the regenerative current flows from the negative terminal side to the positive terminal side of the DC power supply 21 through the parasitic diode 23 provided in the switching element 22. Subsequently, the control unit 24 switches the control signal G(t) output to the switching element 22 from a low level to a high level, switching the switching element 22 from the OFF state to the ON state. Thereafter, the control unit 24 repeats the above operation.

[0095] The detection unit 26, connected to the circuit on the primary winding L1 side, detects the voltage when the primary current I1 flows through the detection unit 26 and transmits the detection signal D1 to the control unit 24. Although not shown in Figure 4, the control unit 24 is equipped with a comparator that compares the detected voltage (Vcp = R1 × I1) output from the detection unit 26 with a predetermined reference voltage and outputs an output signal corresponding to the comparison result. However, this comparator does not need to be mounted on the control unit 24; it may be configured by combining the necessary circuit components.

[0096] The detection unit 26 detects the current and power values ​​in the circuit on the primary winding L1 side of the transformer 30. When the product of the primary current I1 and the resistance value of resistor R1, i.e., the voltage value across the terminals of resistor R1, reaches a predetermined reference voltage, the control unit 24 switches from the first control mode C1, in which it operates normally, to the second control mode C2, in which it suppresses power overload. In this embodiment, as shown in Figure 5, the second control mode is executed for a longer period than the cycle of repeating the ON and OFF states of the switching element 22 in the first control mode C1, but the duration for executing the second control mode C2 can be set arbitrarily.

[0097] In this way, by switching between the first control mode C1 and the second control mode C2, the power value is controlled to remain below a predetermined reference value even when the impedance of the first space A1 fluctuates violently. In addition to the above, the control unit 24 can employ various means to control the power value in the circuit on the primary side winding L1 of the transformer 30.

[0098] In the second control mode C2, the control signal G(t) of the switching element 22 is kept in the OFF state during periods when the detected voltage Vcp is higher than the periodically fluctuating comparison voltage Vt.

[0099] More specifically, with respect to the comparison voltage Vt, which is formed as a triangular wave with a frequency lower than G(t), initially, when the detected voltage Vcp is sufficiently low immediately after the start of operation, the detected voltage Vcp rarely exceeds the comparison voltage Vt, and the first control mode C1 is executed, in which the switching element 22 repeatedly switches between the ON and OFF states.

[0100] As the impedance changes and the amplitudes of the secondary voltage V2 and secondary current I2 gradually increase, the electromotive force generated in the primary winding L1 of the transformer 30 increases due to the secondary current I2 that flows in the opposite direction to the lighting operation after the UV light irradiation unit 10 is turned on. As a result, a charge is accumulated in the parasitic capacitance element (not shown) located between the switching element 22 and the detection unit 26, causing the potential of that node (detection voltage Vcp) to fluctuate, as shown in Figure 5.

[0101] When the detected voltage Vcp gradually fluctuates and exceeds the comparison voltage Vt, the second control mode C2 is executed. At this time, as shown in Figure 5, since the comparison voltage Vt is a triangular wave, the period during which the second control mode C2 is executed is temporary. Then, as the detected voltage Vcp gradually increases and the period during which it exceeds the comparison voltage Vt increases, the period during which the second control mode C2 is executed gradually becomes longer than the period during which the first control mode C1 is executed.

[0102] This control is a feedback control in which, as the impedance of the secondary winding L2 of the transformer 30 decreases, the period of execution of the second control mode C2 becomes longer than the period of execution of the first control mode C1.

[0103] This controls the power value in the circuit on the primary winding L1 side to be below the reference value. As a result, even if the impedance of the first space A1 fluctuates, the load on the circuit on the primary winding L1 side is reliably reduced. Note that, not limited to the configuration shown in Figure 5, the second control mode may be executed during the period when the detected voltage Vcp is lower than the comparison voltage Vt, and the control signal G(t) of the switching element may be kept in the OFF state. In this case, the comparison voltage Vt used will be a waveform with the opposite phase to the waveform shown in Figure 5.

[0104] Based on the above configuration, the voltage applied to the ultraviolet light irradiation unit 10 of the ultraviolet light irradiation device 1 is hardly affected by changes in the impedance of the first space A1. In other words, the ultraviolet light irradiation device 1 with the above configuration can stably light up the ultraviolet light irradiation unit 10 regardless of the impedance of the first space A1.

[0105] Furthermore, when using a push-pull circuit that operates at the resonant frequency, the operating frequency of the ultraviolet light irradiation unit 10 can be changed by installing multiple resonant capacitors with different capacitances in the lighting circuit 20 and switching the resonant capacitor used during operation according to the data signal from the detection unit 26. Such control can reduce the load on the lighting circuit 20.

[0106] [Verification experiment] Here, we conducted a verification experiment to confirm how the power supplied to the ultraviolet light irradiation unit 10 changes when the air pressure inside the chamber 12 changes, under two conditions: when the power supplied to the ultraviolet light irradiation unit 10 is controlled (Condition 1) and when it is not controlled (Condition 2). The details of this experiment will now be explained.

[0107] (Verification conditions) In this verification experiment, using the lighting circuit shown in Figure 4, an excimer lamp, a type of dielectric barrier discharge lamp, was housed in a housing that mimicked the chamber 12, instead of the ultraviolet light irradiation unit 10. The experiment confirmed how the power supplied to the excimer lamp changed while the inside of the housing was depressurized. The excimer lamp housed in the housing was an excimer lamp equipped with a cylindrical discharge tube as shown in Figures 1B and 1C, and a mesh electrode wrapped around the outer wall surface of the discharge tube. In this case, the space between the discharge tube and the mesh electrode corresponds to the first space A1.

[0108] This verification experiment compared the effective power supplied to the excimer lamp when the air pressure inside the enclosure was varied to 800 hPa, 600 hPa, 400 hPa, and 237 hPa. As a baseline, the effective power supplied to the excimer lamp was also confirmed when the pressure inside the enclosure was not reduced. Furthermore, the ultraviolet intensity was measured by placing the light-receiving element of an ultraviolet intensity meter (TOPCON UVR-300) 5 mm away from the excimer lamp inside the enclosure.

[0109] (result) The results are shown in Tables 1 and 2 below. Table 1 shows the results under condition 1, and Table 2 shows the results under condition 2.

[0110] [Table 1]

[0111] [Table 2]

[0112] As shown in Table 2 above, under condition 2, where no control is applied, the power supplied to the excimer lamp increases in response to the decrease in air pressure inside the enclosure. Such fluctuations create a large load on the lighting circuit 20, which could lead to problems such as damage to the circuit elements that make up the lighting circuit.

[0113] In contrast, as shown in Table 1 above, under condition 1, the power supplied to the excimer lamp and the ultraviolet intensity remain constant even when the atmospheric pressure changes.

[0114] [Alternative Embodiment] The following describes other embodiments.

[0115] <1> Figure 6 is a schematic timing chart showing an example of the time variation of the control signal G(t), primary current I1, secondary voltage V2, and secondary current I2. It shows the case when the control unit 24 is operated to transition the switching element 22 from the OFF state to the ON state after a predetermined OFF holding time has elapsed from the point when the regenerative current flowing through the primary winding L1 reaches zero. Note that the graph shown in Figure 6 was obtained by an embodiment to which the lighting circuit shown in Figure 4 is applied. Therefore, the following explanation describes an embodiment to which the lighting circuit shown in Figure 4 is applied.

[0116] In this embodiment, the control signal G(t) from the control unit 24 is set so that the time for which the switching element 22 is held in the OFF state is variable based on the detection signal D1 from the detection unit 26. As a result, the average power value of the circuit on the primary winding L1 side is controlled to be below a reference value, and the power of the circuit on the primary winding L1 side is controlled in accordance with the detection signal D1 from the detection unit 26. This ensures that the load on the circuit on the primary winding L1 side is reliably reduced when the impedance of the first space A1 fluctuates.

[0117] <2> The configurations of the ultraviolet light irradiation device 1 and the lighting circuit 20 described above are merely examples, and the present invention is not limited to the illustrated configurations. [Explanation of Symbols]

[0118] 1: Ultraviolet light irradiation device 10: Ultraviolet light irradiation section 11: Discharge tube 11a: Discharge space 12: Chamber 13a: First electrode 13b: Second electrode 14: Pinch seal section 20: Lighting circuit 21: DC power supply 22: Switching mechanism 23: Parasitic diode 24: Control Unit 25: Smoothing Capacitor 26: Detection unit 26a: Related to diodes 30: Trans 40: Capacitive control circuit 41: Resistor control circuit A1 : First space L1: Primary winding L2: Secondary winding a1: First electrode terminal a2: Second electrode terminal b1 : First terminal b2 : Second terminal

Claims

1. A lighting circuit comprising a DC power supply, a transformer having a primary winding and a secondary winding, and at least one switching element, wherein the switching element switches between an ON state and an OFF state to switch the supply and stop of current from the DC power supply to the primary winding of the transformer, or to change the direction of the current flowing through the primary winding, thereby generating an electromotive force in the secondary winding of the transformer. A UV light irradiation unit connected to the secondary winding of the transformer, having a first electrode and a second electrode, wherein the tube wall of a light-emitting tube filled with light-emitting gas and a first space where the impedance changes are interposed between the first electrode and the second electrode, A detection unit that directly or indirectly detects the impedance of the first space, An ultraviolet light irradiation device comprising a control unit that controls the frequency for switching between the ON state and the OFF state of the switching element based on the impedance of the first space detected by the detection unit, or a parameter related to the impedance of the first space.

2. The ultraviolet light irradiation device according to claim 1, characterized in that at least a portion of the second electrode is in contact with the wall of the discharge tube.

3. The ultraviolet light irradiation device according to claim 1, characterized in that the impedance of the first space changes due to a change in atmospheric pressure or humidity within the space.

4. The ultraviolet light irradiation device according to claim 1, characterized in that the lighting circuit is a push-pull type, a full-bridge type, or a half-bridge type circuit.

5. The ultraviolet light irradiation device according to claim 1, characterized in that the lighting circuit is a flyback type circuit.

6. The ultraviolet light irradiation device according to claim 1, characterized in that the detection unit is connected to the secondary winding of the transformer.

7. The ultraviolet light irradiation device according to claim 1, characterized in that the detection unit is connected to the primary winding of the transformer.

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