Lighting device and irradiation device for barrier discharge lamps

Abstract

The objective is to provide a lighting device and irradiation device for a barrier discharge lamp that can control the barrier discharge lamp at a constant power level using simple means. [Solution] The lighting device for a barrier discharge lamp according to the embodiment applies power to the barrier discharge lamp. The lighting device for the barrier discharge lamp comprises, on its output side, an inverter circuit to which the barrier discharge lamp is electrically connected; a DC power supply electrically connected to the input side of the inverter circuit; a power detection circuit electrically connected between the inverter circuit and the DC power supply to detect the power applied to the inverter circuit; and a control circuit electrically connected between the power detection circuit and the DC power supply to control the DC power supply to a constant power based on a signal from the power detection circuit.

Description

Technical Field

[0001] Embodiments of the present invention relate to a lighting device for a barrier discharge lamp and an irradiation device.

Background Art

[0002] A barrier discharge lamp such as an excimer lamp includes, for example, a light-emitting tube formed of a dielectric material such as synthetic quartz glass, internal electrodes provided inside the light-emitting tube, and external electrodes provided outside the light-emitting tube. Further, in order to dissipate the heat generated during lighting of the barrier discharge lamp, a cooling portion facing the light-emitting tube is provided across the external electrodes. The cooling portion is formed of a metal such as aluminum or stainless steel.

[0003] Here, if constant current control is performed so that the lamp current of the barrier discharge lamp becomes constant, or constant voltage control is performed so that the lamp voltage of the barrier discharge lamp becomes constant, it is considered that the illuminance of ultraviolet rays or the like irradiated from the barrier discharge lamp falls within a predetermined range.

[0004] However, when a cooling portion facing the barrier discharge lamp is provided, variations in equivalent capacitance due to errors in the wall thickness of the light-emitting tube or variations in equivalent capacitance due to mounting errors between the barrier discharge lamp and the cooling portion may occur. When variations in equivalent capacitance occur, even if constant current control of the lamp current or constant voltage control of the lamp voltage is performed, the power of the barrier discharge lamp fluctuates. When the power of the barrier discharge lamp fluctuates, there is a risk that the illuminance of ultraviolet rays or the like irradiated fluctuates, or the barrier discharge lamp may have a shortened life due to over-power.

[0005] Therefore, a technology for constant power control of barrier discharge lamps has been proposed. However, since the operation of barrier discharge lamps is controlled by an inverter, the waveforms of the lamp voltage and lamp current become pulse waveforms. As a result, it becomes difficult to accurately detect the lamp current and lamp voltage using simple means such as shunt resistors (current sensing resistors), and consequently, it can be difficult to control the barrier discharge lamp at a constant power level.

[0006] Therefore, there was a need for the development of a technology that could control barrier discharge lamps at constant power using simple methods. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2010-27944 [Overview of the project] [Problems that the invention aims to solve]

[0008] The problem that this invention aims to solve is to provide a lighting device and irradiation device for a barrier discharge lamp that can control the barrier discharge lamp at a constant power level using simple means. [Means for solving the problem]

[0009] The lighting device for a barrier discharge lamp according to the embodiment applies power to the barrier discharge lamp. The lighting device for the barrier discharge lamp comprises, on its output side, an inverter circuit to which the barrier discharge lamp is electrically connected; a DC power supply electrically connected to the input side of the inverter circuit; a power detection circuit electrically connected between the inverter circuit and the DC power supply to detect the power applied to the inverter circuit; and a control circuit electrically connected between the power detection circuit and the DC power supply to control the DC power supply to a constant power based on a signal from the power detection circuit. [Effects of the Invention]

[0010] According to embodiments of the present invention, it is possible to provide a lighting device for a barrier discharge lamp and an irradiation device that can control the barrier discharge lamp at a constant power level using simple means. [Brief explanation of the drawing]

[0011] [Figure 1] This is a block diagram illustrating an illumination device equipped with a lighting device according to this embodiment. [Figure 2] This is a schematic diagram illustrating an excimer lamp module. [Figure 3] This is a circuit diagram illustrating a power detection circuit. [Modes for carrying out the invention]

[0012] The embodiments will be illustrated below with reference to the drawings. In each drawing, similar components are denoted by the same reference numerals, and detailed descriptions will be omitted as appropriate.

[0013] The lighting device 1 for barrier discharge lamps according to this embodiment (hereinafter simply referred to as lighting device 1) is suitable for lighting, for example, an excimer lamp. However, lighting device 1 can also be used to light barrier discharge lamps other than excimer lamps. Here, as an example, lighting device 1 for lighting an excimer lamp will be described.

[0014] Figure 1 is a block diagram illustrating an illumination device 100 equipped with a lighting device 1 according to this embodiment. As shown in Figure 1, the irradiation device 100 includes, for example, an excimer lamp module 200 and a lighting device 1.

[0015] Figure 2 is a schematic diagram illustrating the excimer lamp module 200. As shown in Figure 2, the excimer lamp module 200 includes, for example, an excimer lamp 201 and a cooling unit 208.

[0016] The excimer lamp 201 has, for example, a discharge tube 202, internal electrodes 203, a reflective film 204, a holder 205, lead wires 206, and external electrodes 207.

[0017] The discharge tube 202 is cylindrical and made of a dielectric material such as synthetic quartz glass. Both ends of the discharge tube 202 are sealed, and a gas capable of generating excimer-excited molecules such as xenon gas is enclosed in the internal space of the discharge tube 202.

[0018] The internal electrodes 203 are coiled and extend along the tube axis in the internal space of the discharge tube 202. The reflective film 204 is in the form of a film and provided on the inner wall of the discharge tube 202. The holder 205 is provided at each of both ends of the discharge tube 202 in the tube axis direction.

[0019] One end of the lead wire 206 is electrically connected to the internal electrode 203. The other end of the lead wire 206 is electrically connected to the output terminal of the lighting device 1 (inverter circuit 3).

[0020] The external electrodes 207 can be provided on the outer wall of the discharge tube 202. The external electrodes 207 extend along the tube axis of the discharge tube 202. The external electrodes 207 face the reflective film 204 through the discharge tube 202, for example.

[0021] The lead wire 206 and the lead wire electrically connected to the external electrode 207 are electrically connected to the inverter circuit 3 of the lighting device 1.

[0022] When power is applied from the lighting device 1 to the excimer lamp 201, a barrier discharge occurs between the internal electrode 203 and the external electrode 207, and high-energy electrons are given to the enclosed gas to generate excimer-excited molecules. When the excimer-excited molecules return to their original state, ultraviolet rays having a specific peak wavelength are generated according to the type of gas. For example, when the gas is xenon gas, ultraviolet rays with a main wavelength of 172 nm are generated.

[0023] The generated ultraviolet light is irradiated to the outside of the excimer lamp 201 via the discharge tube 202, and the irradiated ultraviolet light is used for surface treatments such as photocleaning, surface modification, oxide film formation, and ozone generation.

[0024] The cooling section 208 is provided to dissipate the heat generated when a barrier discharge occurs between the internal electrode 203 and the external electrode 207. The cooling section 208 is block-shaped and has a recess in which a portion of the excimer lamp 201 is housed. The recess of the cooling section 208 opens on one side of the cooling section 208 and extends along the tube axis of the discharge tube 202. The recess of the cooling section 208 faces the discharge tube 202 with the external electrode 207 in between. For example, the inner surface of the recess of the cooling section 208 is a curved surface that follows the outer surface of the external electrode 207.

[0025] The cooling unit 208 can be made of a metal such as aluminum or stainless steel, and may have a passage through which a coolant such as water flows. The presence of the cooling unit 208 prevents the excimer lamp 201 from overheating, which could shorten its lifespan or cause it to malfunction.

[0026] The lighting device 1 is electrically connected to the excimer lamp 201. The lighting device 1 applies power to the excimer lamp 201. As shown in Figure 1, the lighting device 1 includes, for example, a DC power supply 2, an inverter circuit 3, a power detection circuit 4, and a control circuit 21.

[0027] The output side of the DC power supply 2 is electrically connected to the input side of the inverter circuit 3. The input side of the DC power supply 2 can be electrically connected to the AC power supply 300. The AC power supply 300 is, for example, a commercial power supply. The DC power supply 2 is equipped with, for example, a rectifier to convert the AC voltage from the AC power supply 300 to a DC voltage. Note that the AC power supply 300 is not necessarily required; for example, the DC power supply 2 may be a battery or the like.

[0028] Furthermore, a control circuit 21 for constant power control of the DC power supply 2 can be provided. Based on a signal from the power detection circuit 4 (comparison circuit 45), the control circuit 21 controls at least one of the output voltage and output current of the DC power supply 2 so that the power applied to the inverter circuit 3 and, consequently, the excimer lamp 201 is within a predetermined range. The control circuit 21 is electrically connected between the power detection circuit 4 and the DC power supply 2. The control circuit 21 can be built into the DC power supply 2 or it can be provided separately from the DC power supply 2. The control circuit 21 illustrated in Figure 1 is built into the DC power supply 2.

[0029] The input side of the inverter circuit 3 is electrically connected to the output side of the DC power supply 2 via the power detection circuit 4. The output side of the inverter circuit 3 is electrically connected to the excimer lamp 201. The inverter circuit 3 converts, for example, the DC voltage from the DC power supply 2 into a pulse voltage of a predetermined frequency. In this case, the frequency is, for example, around 30kHz to 300kHz. The inverter circuit 3 can be equipped with, for example, a half-bridge circuit or a full-bridge circuit using switching elements such as a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor).

[0030] Here, if the lamp current of the excimer lamp 201 is controlled to be constant, or the lamp voltage of the excimer lamp 201 is controlled to be constant, it is thought that the illuminance of ultraviolet light emitted from the excimer lamp 201 will be within a predetermined range. If the illuminance of ultraviolet light is within a predetermined range, it becomes easier to control the integrated light quantity and the quality of the processed object can be improved.

[0031] However, the equivalent capacitance between the excimer lamp 201 and the cooling unit 208 may fluctuate. For example, as mentioned above, the discharge tube 202 of the excimer lamp 201 is made from synthetic quartz glass or the like, making it difficult to suppress variations in wall thickness. Therefore, variations in the equivalent capacitance between the excimer lamp 201 and the cooling unit 208 may occur due to manufacturing tolerances of the excimer lamp 201.

[0032] Furthermore, it is difficult to suppress variations in the shape and dimensions of the discharge tube 202 in the direction perpendicular to the tube axis. As a result, when the excimer lamp 201 is housed in the recess of the cooling unit 208, the position of the excimer lamp 201 relative to the cooling unit 208 may vary. When the position of the excimer lamp 201 relative to the cooling unit 208 varies, variations occur in the equivalent capacitance between the excimer lamp 201 and the cooling unit 208.

[0033] In other words, variations in equivalent capacitance may occur due to errors in the thickness of the discharge tube 202, and variations in equivalent capacitance may occur due to mounting errors between the excimer lamp 201 and the cooling unit 208.

[0034] When variations in equivalent capacity occur, the power of the excimer lamp 201 will fluctuate even if the lamp current is controlled to a constant current or the lamp voltage is controlled to a constant voltage. When the power of the excimer lamp 201 fluctuates, the intensity of the emitted ultraviolet light may fluctuate, and the lifespan of the excimer lamp 201 may be shortened due to overpowering.

[0035] In this case, the power applied to the excimer lamp 201 can be kept within a predetermined range by detecting the power on the output side of the inverter circuit 3 and by the control circuit 21 feedback-controlling at least one of the output voltage of the DC power supply 2 and the output current of the DC power supply 2 so that the detected power falls within a predetermined range.

[0036] However, the voltage and current waveforms output from the inverter circuit 3 are pulse waveforms. Since pulse waveforms have pauses and fluctuate alternately between positive and negative sides, it becomes difficult to accurately detect the voltage and current output from the inverter circuit 3 using simple means such as a shunt resistor (current sensing resistor). Therefore, detecting the power on the output side of the inverter circuit 3 may make it difficult to control the excimer lamp 201 at a constant power level.

[0037] Therefore, in the lighting device 1 according to this embodiment, as shown in Figure 1, a power detection circuit 4 is electrically connected between the inverter circuit 3 and the DC power supply 2. The power detection circuit 4 detects the power on the input side of the inverter circuit 3 (the power applied to the inverter circuit 3) and inputs a signal based on the detected power value to the control circuit 21.

[0038] The control circuit 21, based on the input signal, feedback-controls at least one of the output voltage and output current of the DC power supply 2 so that the power applied to the input side of the inverter circuit 3, and consequently the power applied to the excimer lamp 201, is within a predetermined range.

[0039] In this way, even if the aforementioned variation in equivalent capacity occurs, the power applied to the excimer lamp 201 can be kept within a predetermined range. Furthermore, since the input side of the inverter circuit 3 is supplied with DC voltage and DC current, it becomes easy to accurately detect the voltage and current input to the inverter circuit 3 using simple means such as a shunt resistor (current sensing resistor). Therefore, the power applied to the input side of the inverter circuit 3, and consequently the power applied to the excimer lamp 201, can be controlled to a constant power level using simple means.

[0040] Figure 3 is a circuit diagram illustrating the power detection circuit 4. As shown in Figures 1 and 3, the power detection circuit 4 includes, for example, a voltage detection circuit 41, a current detection circuit 42, a power calculation circuit 43, a reference voltage circuit 44, a comparison circuit 45, and a photocoupler 46.

[0041] The voltage detection circuit 41 is electrically connected to the output side of the DC power supply 2. The voltage detection circuit 41 detects the voltage output from the DC power supply 2. The voltage detection circuit 41 includes, for example, a voltage divider circuit having multiple resistors 41a. The voltage detection circuit 41 detects the voltage output from the DC power supply 2 based on the voltage drop that occurs when the voltage output from the DC power supply 2 is applied to the resistors 41a. The voltage detection circuit 41 outputs a voltage corresponding to the resistance value of the resistors 41a and the voltage output from the DC power supply 2 as the detected voltage. Since the voltage output from the voltage detection circuit 41 is a voltage divided by the voltage divider circuit at a predetermined ratio, the voltage output from the voltage detection circuit 41 is smaller than the voltage output from the DC power supply 2. Therefore, the voltage applied to the power calculation circuit 43, which will be described later, can be reduced, making it possible to use a smaller power calculation element.

[0042] The current detection circuit 42 is electrically connected to the output side of the DC power supply 2. The current detection circuit 42 detects the current output from the DC power supply 2. The current detection circuit 42 includes, for example, a shunt resistor type current detection circuit 42a and an RC integrating circuit 42b.

[0043] The shunt resistor type current detection circuit 42a is electrically connected to the output side of the DC power supply 2. The shunt resistor type current detection circuit 42a detects the current output from the DC power supply 2. The shunt resistor type current detection circuit 42a includes, for example, a resistor and an operational amplifier. The shunt resistor type current detection circuit 42a detects the current output from the DC power supply 2 based on the voltage drop generated when the current output from the DC power supply 2 flows through the resistor. The resistor outputs a voltage corresponding to its resistance value and the current output from the DC power supply 2 as the detected current. Since the voltage output from the resistor is small, the operational amplifier amplifies the current output from the resistor. In this way, the current output from the DC power supply 2 can be detected with high accuracy.

[0044] Here, since the current output from the DC power supply 2 is a pulse wave, the voltage output from the operational amplifier in the shunt resistor type current detection circuit 42a fluctuates in a pulse-like manner. For this reason, an RC integrator circuit 42b is electrically connected to the output side of the operational amplifier in the shunt resistor type current detection circuit 42a. The RC integrator circuit 42b averages the voltage output from the operational amplifier. Therefore, even with a pulse wave, fluctuations in the voltage output from the current detection circuit 42 can be suppressed.

[0045] The power calculation circuit 43 is electrically connected to the output side of the voltage detection circuit 41 and to the output side of the RC integrator 42b of the current detection circuit 42. The power calculation circuit 43 multiplies the voltage detected by the voltage detection circuit 41 and the voltage detected by the current detection circuit 42. The power calculation circuit 43 includes, for example, a multiplier 43a. The multiplier 43a can be, for example, an analog multiplier. The multiplier 43a multiplies the voltage input from the voltage detection circuit 41 and the voltage input from the RC integrator 42b, and outputs a voltage corresponding to the multiplied value. In other words, the power calculation circuit 43 outputs a voltage corresponding to the power output from the DC power supply 2.

[0046] The reference voltage circuit 44 generates a reference voltage used when generating a signal for constant power control. The reference voltage circuit 44 can be, for example, a shunt regulator.

[0047] The comparator circuit 45 generates a signal for constant power control based on the reference voltage and the output from the power calculation circuit 43. The comparator circuit 45 includes, for example, a comparator 45a. The output side of the reference voltage circuit 44 is electrically connected to the non-inverting input (V+) of the comparator 45a. The output side of the power calculation circuit 43 is electrically connected to the inverting input (V-) of the comparator 45a.

[0048] If the voltage from the power calculation circuit 43 corresponding to the power output from the DC power supply 2 is higher than the reference voltage from the reference voltage circuit 44, the output terminal of comparator 45a is connected to GND. If the voltage from the power calculation circuit 43 corresponding to the power output from the DC power supply 2 is lower than the reference voltage from the reference voltage circuit 44, the output terminal of comparator 45a is open.

[0049] The output side of the comparison circuit 45 is electrically connected to the control circuit 21 via a photocoupler 46. The photocoupler 46 electrically isolates the power detection circuit 4 from the control circuit 21. By providing the photocoupler 46, it is possible to suppress the flow of unexpected current between the power detection circuit 4 and the control circuit 21. Therefore, the power detection circuit 4 and the control circuit 21 can be protected.

[0050] The control circuit 21, based on the signal from the comparator circuit 45 (comparator 45a), feedback-controls at least one of the voltage and current output from the DC power supply 2 to ensure that the power applied to the input side of the inverter circuit 3, and consequently the power applied to the excimer lamp 201, is within a predetermined range. In other words, the control circuit 21 provides constant power control to the excimer lamp 201 based on the signal from the comparator circuit 45 (comparator 45a).

[0051] As described above, since the lighting device 1 according to this embodiment is provided with a power detection circuit 4, even if at least one of the following occurs: variation in equivalent capacitance due to an error in the thickness of the discharge tube 202, or variation in equivalent capacitance due to mounting errors between the excimer lamp 201 and the cooling unit 208, constant power control can be performed so that the power applied to the excimer lamp 201 remains within a predetermined range.

[0052] Furthermore, the power detection circuit 4 is electrically connected between the DC power supply 2 and the inverter circuit 3. Therefore, the power detection circuit 4 can detect the power applied to the excimer lamp 201 based on the DC voltage and DC current output from the DC power supply 2. If power can be detected based on DC voltage and DC current, the power applied to the input side of the inverter circuit 3, and thus the power applied to the excimer lamp 201, can be detected using simple means such as a shunt resistor (current sensing resistor).

[0053] Furthermore, the DC voltage output from the DC power supply 2 is lower than the AC voltage output from the inverter circuit 3. Therefore, if the power detection circuit 4 is electrically connected between the DC power supply 2 and the inverter circuit 3, detection can be performed based on the lower voltage, allowing voltage detection with a low-resistance detection resistor.

[0054] Although several embodiments of the present invention have been illustrated above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. Furthermore, the embodiments described above can be implemented in combination with each other.

[0055] The following are additional notes regarding the embodiments described above.

[0056] (Note 1) On the output side, there is an inverter circuit to which the barrier discharge lamp is electrically connected; A DC power supply electrically connected to the input side of the inverter circuit; A power detection circuit is electrically connected between the inverter circuit and the DC power supply and detects the power applied to the inverter circuit; A control circuit is electrically connected between the power detection circuit and the DC power supply, and controls the DC power supply to a constant power based on a signal from the power detection circuit; A lighting device for barrier discharge lamps equipped with the following features.

[0057] (Note 2) The power detection circuit is, A voltage detection circuit for detecting the voltage output from the DC power supply; A current detection circuit for detecting the current output from the DC power supply; A power calculation circuit that multiplies the voltage detected by the voltage detection circuit and the current detected by the current detection circuit; A lighting device for a barrier discharge lamp as described in Appendix 1, comprising the features described above.

[0058] (Note 3) The current detection circuit is, A shunt resistor type current detection circuit for detecting the aforementioned current; An RC integrating circuit is electrically connected to the output side of the aforementioned shunt-resistance type current detection circuit; A lighting device for a barrier discharge lamp as described in Appendix 2, which is equipped with the following:

[0059] (Note 4) The power detection circuit is, A reference voltage circuit that generates a reference voltage; A comparison circuit that generates a signal for performing constant power control based on the aforementioned reference voltage and the output from the power calculation circuit; A lighting device for a barrier discharge lamp as described in Appendix 2 or 3, further comprising the above.

[0060] (Note 5) Barrier discharge lamp and; A cooling unit having a recess in which a portion of the barrier discharge lamp is housed; A lighting device for a barrier discharge lamp, as described in any one of the appendices 1 to 4, which is electrically connected to the barrier discharge lamp; An irradiation device equipped with the following. [Explanation of Symbols]

[0061] 1 Lighting device, 2 DC power supply, 3 Inverter circuit, 4 Power detection circuit, 21 Control circuit, 41 Voltage detection circuit, 42 Current detection circuit, 42a Shunt resistor type current detection circuit, 42b RC integrating circuit, 43 Power calculation circuit, 44 Reference voltage circuit, 45 Comparison circuit, 46 Photocoupler, 100 Irradiation device, 200 Excimer lamp module, 201 Excimer lamp, 202 Discharge tube, 203 Internal electrode, 207 External electrode, 208 Cooling unit

Claims

1. A lighting device for a barrier discharge lamp that applies power to a barrier discharge lamp, On the output side, there is an inverter circuit to which the barrier discharge lamp is electrically connected; A DC power supply electrically connected to the input side of the inverter circuit; A power detection circuit is electrically connected between the inverter circuit and the DC power supply and detects the power applied to the inverter circuit; A control circuit is electrically connected between the power detection circuit and the DC power supply, and controls the DC power supply to a constant power based on a signal from the power detection circuit; A lighting device for barrier discharge lamps equipped with the following features.

2. The power detection circuit is, A voltage detection circuit for detecting the voltage output from the DC power supply; A current detection circuit for detecting the current output from the DC power supply; A power calculation circuit that multiplies the voltage detected by the voltage detection circuit and the current detected by the current detection circuit; A lighting device for a barrier discharge lamp according to claim 1, comprising the above.

3. The current detection circuit is, A shunt resistor type current detection circuit for detecting the aforementioned current; The RC integrating circuit is electrically connected to the output side of the aforementioned shunt-resistance type current detection circuit; A lighting device for a barrier discharge lamp according to claim 2, comprising the above.

4. The power detection circuit is, A reference voltage circuit that generates a reference voltage; A comparison circuit that generates a signal for performing constant power control based on the reference voltage and the output from the power calculation circuit; A lighting device for a barrier discharge lamp according to claim 2 or 3, further comprising the above.

5. Barrier discharge lamp and; A cooling section having a recess in which a portion of the barrier discharge lamp is housed; A lighting device for a barrier discharge lamp according to claim 1, electrically connected to the barrier discharge lamp; An irradiation device equipped with the following.

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