JP3348648B2 - Dielectric barrier discharge lamp light source device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp used as an ultraviolet light source for photochemical reactions, for example, which forms excimer molecules by dielectric barrier discharge.
The present invention relates to a light source device including a so-called dielectric barrier discharge lamp using light emitted from the excimer molecule.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. Hei 2-7353 discloses a technique relating to a dielectric barrier discharge lamp related to the present invention. This publication describes a radiator in which a discharge vessel is filled with a discharge gas for forming excimer molecules, excimer molecules are formed by dielectric barrier discharge, and light emitted from the excimer molecules is extracted (dielectric). Body barrier discharge: also known as ozonizer discharge or silent discharge, refer to the revised edition of the “Discharge Handbook” published by the Institute of Electrical Engineers of Japan, reprinted in 7th edition, June 1991, page 263).
In a dielectric barrier discharge lamp, one or two dielectrics exist between electrodes across a discharge plasma space. FIG. 19A shows a dielectric barrier discharge lamp 1 in which two dielectrics 5 and 6 are present. By the way, FIG.
In the figure, the lamp envelope 7 also functions as the dielectrics 5 and 6.

When the dielectric barrier discharge lamp 1 is turned on, the electrodes 3 and 4 of the two poles are, for example, 10 kHz to 2 kHz.
A high-frequency AC voltage of 00 kHz, 2 kV to 10 kV is applied. However, due to the dielectrics 5 and 6 interposed between the discharge plasma space 2 and the electrodes 3 and 4, current does not flow directly from the electrodes 3 and 4 to the discharge plasma space 2, but the dielectrics 5 and 6 are used as capacitors. Electric current flows by working. That is, the discharge plasma space 2 of each of the dielectrics 5 and 6
On the surface on the side, electric charges having the same sign as the surface on the side of each of the electrodes 3 and 4 are induced by the polarization of the dielectric, and discharge occurs between the surfaces of the dielectrics 5 and 6 opposed to each other across the discharge plasma space 2. I do.

A small amount of current flows along the surface of the dielectrics 5 and 6 on the side of the discharge plasma space 2, and the portion where the discharge occurs is induced on the surface of the dielectrics 5 and 6 on the side of the discharge plasma space 2. The charge is neutralized by the charge transferred by the discharge,
The electric field in the discharge plasma space 2 decreases. For this reason, even if the voltage application to the electrodes 3 and 4 is continued, the discharge current eventually stops. However, when the voltage applied to the electrodes 3 and 4 further increases, the discharge current continues. When the discharge is stopped after the discharge once occurs, the discharge is not performed again until the polarity of the voltage applied to the electrodes 3 and 4 is reversed. For example, in the case of a dielectric barrier discharge lamp in which xenon gas is sealed, the xenon gas is separated into ions and electrons by discharge and becomes xenon plasma. In this plasma, xenon excited to a specific energy level is combined to form excimer molecules. Xenon excimer is dissociated after a certain lifetime, and the energy released at this time is emitted as a photon having a vacuum ultraviolet wavelength. In order to operate the dielectric barrier discharge lamp efficiently as a vacuum ultraviolet light source, it is necessary to efficiently form excimer molecules.

A major factor that hinders efficient excimer molecule formation during discharge is that the discharge plasma is excited to an energy level that does not contribute to excimer molecule formation. The electron motion of the discharge plasma immediately after the start of discharge is collective, and the energy is high but the temperature is low. In this state, the discharge plasma has a high probability of transitioning to a resonance state necessary for forming excimer molecules.
However, as the discharge time increases, the electron motion of the plasma gradually becomes thermal, that is, a thermal equilibrium state called a Maxwell-Boltzmann distribution, and the plasma temperature increases,
The probability of transition to a higher excited state that cannot form excimer molecules increases.

Furthermore, even when excimer molecules are formed, the excimer molecules may be destroyed by a subsequent discharge before the intended photons are emitted and naturally dissociated after the elapse of the lifetime. . In fact, in the case of xenon excimer, it takes 1 μs from the start of discharge to the emission of photons of vacuum ultraviolet wavelength.
A period of time is required, and subsequent discharge or re-discharge during this period reduces the efficiency of excimer light emission. That is, it is understood that once the discharge has started, it is most important to make the energy of the subsequent discharge as small as possible.

Even if the discharge time is short, if the energy injected during the discharge period is too large, the probability of similarly transitioning to a high excited state will increase. Plasma that has transitioned to a highly excited state emits infrared radiation and relaxes,
Only increasing the temperature of the lamp does not contribute to excimer emission. That is, discharge driving must be performed to suppress the excitation of discharge plasma to an energy level that does not contribute to excimer molecule formation. In this respect, the conventional dielectric barrier discharge lamp light source device has not been satisfactory.

Japanese Unexamined Patent Publication No. 1-243363 discloses a proposal for achieving high efficiency of excimer light emission by all pulse discharges including a dielectric barrier discharge. This is in line with the above-mentioned condition that once the discharge has started, the energy of the subsequent discharge should be as small as possible. However, what is described in this proposal is about what parameters should be adjusted to improve the efficiency of excimer emission, and what conditions are effective for the parameter values are specifically described. Not. In particular, in the case of dielectric barrier discharge, since voltage application and current injection to the discharge plasma space must be performed through the dielectric, the degree of freedom in controlling the voltage and current is low, and it is difficult to find optimal conditions. Very difficult.

As a proposal for improving the efficiency of a dielectric barrier discharge lamp, for example, Japanese Patent Application Laid-Open No. 8-508363 is disclosed.
There is a gazette. However, in this proposal, in order to make the excimer molecule formation more efficient, a specific effective, specific method for achieving the suppression of discharge plasma excitation to an energy level that does not contribute to excimer molecule formation is described. No matter is mentioned. Also, as a proposal for improving the driving waveform of a fluorescent lamp using a dielectric barrier discharge, for example,
There is JP-A-6-163006. according to this,
It is described that the luminance of a fluorescent lamp is improved by driving with a positive / negative rectangular pulse train or an alternating rectangular wave. In this, about the rectangular pulse train and the square wave,
An experimental result of a change in luminance with respect to a change in applied voltage is described in relation to a frequency and a duty ratio, and an improvement in efficiency as compared with a conventional sine wave drive is described.

However, an actual power supply device includes a high-voltage transformer and the like, and it is impossible to apply an ideal rectangular pulse train or rectangular wave, and the interaction between the output impedance of the power supply device and the impedance of the lamp is not possible. As a result, the waveform becomes dull, and a sinusoidal voltage is applied partially due to resonance. If there is a deviation from an ideal rectangular waveform in such a real power supply device, any component in the deviation is harmful and economical unless it is clear to what extent the deviation can be tolerated. It is impossible to design and manufacture a practical light source device that meets the requirements.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a dielectric material capable of efficiently generating excimer molecules and operating efficiently as a vacuum ultraviolet light source. It is an object to provide a body barrier discharge lamp light source device.

[0012]

In order to efficiently form excimer molecules, an object of the present invention, it is to suppress the excitation of discharge plasma to an energy level that does not contribute to the formation of excimer molecules. For this purpose, the discharge may be terminated as soon as possible when the voltage applied to the lamp increases at a finite increase rate and reaches the discharge start voltage to start the discharge. The electric circuit operation of the dielectric barrier discharge lamp 1 will be described with reference to FIG. As shown in FIG. 19B, the discharge path of the discharge plasma space 2 is
And the switch 11 are connected in series. Further, the dielectric barrier discharge lamp 1 has dielectrics 5, 6 between the electrodes 3, 4 and the discharge plasma space 2, which function as a capacitor in an electric circuit. However, when there are two dielectrics, it is considered that one capacitor 13 is obtained by combining respective capacitors in series.

Since this capacitor has a structure inserted in series with the discharge plasma space 2, the discharge current flows through the dielectric barrier discharge lamp 1 only during a certain period immediately after the polarity of the voltage applied to the lamp changes. Even when a pulse voltage having a pause period in which the lamp application voltage is substantially zero is not applied, a discharge pause period naturally occurs. No discharge occurs unless the voltage of the discharge plasma space 2 reaches the discharge starting voltage. The discharge plasma space 2 itself also has a capacitor 12.
When the discharge is started, most of the energy charged in the capacitor is consumed in the discharge. Therefore, the power supply device adds an unnecessary current to the dielectric barrier discharge lamp 1 after the start of the discharge. It can be understood that it is sufficient to make it not flow.

Next, consider the unit area of the lamp wall. The discharge starting voltage is almost automatically determined when the gas pressure and the interval between the discharge gaps are determined. Further, the capacitance C1 of the capacitor 12 formed by the discharge plasma space is:
Since it is determined by the discharge gap interval, the minimum energy given to the plasma during the period from the start of one discharge to the end thereof is the energy at which all the charges charged in the capacitor 12 formed by the discharge plasma space are discharged. This is determined by the structure of the lamp. In order to make the excimer molecule formation efficient, suppressing the excitation of the discharge plasma to an energy level that does not contribute to the excimer molecule formation is best achieved under the condition of this minimum energy discharge. Become.

However, the condition of the discharge with the minimum energy can be realized in principle by increasing the voltage applied to the lamp very slowly using a power supply device having an extremely large output impedance and discharging the lamp. . However, such a power supply device has a problem when applied as an actual light source device. The first problem is that if the output impedance is large, a high operating speed for periodic repetitive discharge cannot be obtained. The second problem is that under the condition of the discharge with the minimum energy, the discharge gap may be uneven in one lamp due to the uneven position of the discharge gap in the lamp. Therefore, a practical light source device using a power supply device having a small output impedance capable of realizing a required light amount, and having a margin for uniformly generating a discharge on all wall surfaces of the dielectric barrier discharge lamp. Therefore, it is necessary to make the lamp applied voltage higher than the minimum energy discharge condition. However, the extent to which the voltage applied to the lamp is increased should be kept within a range in which the decrease in excimer emission efficiency due to this is acceptable.

That is, the peak value of the lamp applied voltage is
The value should be suppressed to twice or less, preferably 1.5 times or less, based on the lower limit value for practically negligible discharge nonuniformity. Alternatively, it should be suppressed to 3 times or less, preferably 2.5 times or less, based on a lower limit value for maintaining discharge. When increasing the lamp power, the driving frequency of the lamp power supply should be increased instead of increasing the lamp applied voltage. Since a fixed amount of the lamp current flows every time the lamp applied voltage is inverted, the lamp power is proportional to the driving frequency. Therefore, by increasing the driving frequency, the lamp power can be increased without deteriorating the efficiency due to an increase in the lamp applied voltage.

FIG. 1 shows the basic structure of a dielectric barrier discharge lamp light source device. In the figure, 1 is the above-described dielectric barrier discharge lamp, 8 is a power supply device, and the power supply device 8 is
It comprises a high-frequency AC power supply 9 of a bridge system, a push-pull system, a flyback system or the like, and a step-up transformer Tr. Typical values of the lamp applied voltage E (t), the discharge gap voltage (that is, the voltage of the discharge plasma space 2) V1 (t), the lamp current Is (t), and the discharge current Id (t) in a practical power supply device. FIG. 2 shows a waveform obtained by computer simulation based on a circuit and a lamp based on a full-bridge type power supply device. The waveform is also basic for a half-bridge and push-pull type power supply device. The same applies to the above.) Since the discharge current Id (t) is a current in the lamp flowing through the resistor 10 in FIG. 19B, its waveform cannot be directly measured, but the lamp applied voltage E (t) and the lamp current If the waveform data of Is (t) can be measured, the capacitance C1 of the capacitor 12 in the discharge plasma space 2 and the capacitance C2 of the capacitor 13 in the dielectrics 5 and 6 shown in FIG.
It can be calculated from the floating capacitance C3 existing in parallel with the dielectric barrier discharge lamp.

That is, the capacitance C1 of the capacitor 12 in the discharge plasma space 2 and the capacitance 13 of the dielectrics 5 and 6
Of the discharge current waveform Id (2) using two coefficients F = 1 + C1 / C2 and Cv = C1 + C3.F, which are determined by the capacitance C2 and the floating capacitance C3 existing in parallel with the dielectric barrier discharge lamp. t) can be obtained by the following equation (1). Id (t) = F · Is (t) −Cv · dE (t) / dt (1) Since this method uses numerical differentiation, the accuracy in a region where the current value is small in the obtained waveform is obtained. Although it is not so good, it shows a rapid rise at the start of discharge, so there is no problem as long as it is used for finding it.

In FIG. 2, when the polarity of the lamp applied voltage E (t) changes suddenly, the discharge gap voltage V1 (t) also changes suddenly, and the discharge starts at the point G1 when the discharge gap voltage V1 (t) reaches the discharge starting voltage. When the discharge starts, the discharge current waveform J1 (discharge current I in FIG. 2)
d (t) waveform) appears rapidly, and as a result, the discharge gap voltage V1 (t) drops sharply. The lamp applied voltage E (t) also decreases in accordance with the sharp decrease in the discharge gap voltage V1 (t) (that is, the voltage in the discharge plasma space), and the inflection point K occurs. The point on the ramp applied voltage waveform corresponding to the point J2 at which the discharge current stops exists at or near the maximum point P1 of the absolute value or a little after it. In the evaluation of the actual light source device, the above point can be assumed to exist at the maximum point P1 of the absolute value. Thereafter, the change in the ramp applied voltage waveform up to the inflection point K is reduced to C2 / (C1 + C2) times, and appears as it is in the discharge gap voltage V1 (t) waveform. Here, C1 and C2 are the capacitance C1 of the capacitor 12 in the discharge plasma space 2 and the dielectrics 5 and 6 respectively.
Is the capacitance C2 of the capacitor 13 of FIG. In the case of a dielectric barrier discharge lamp in which the dielectrics 5 and 6 are present on both the electrodes 3 and 4, C2 is considered to be a combination of the individual capacitances of the respective dielectrics in series.

Here, in a practical power supply device, the reason why the bending point K as shown in FIG. 2 occurs in the voltage applied to the lamp is as follows. In response to the sudden decrease in the discharge gap voltage V1 (t) (that is, the voltage in the discharge plasma space),
The lamp applied voltage E (t) also tends to decrease. The power supply device 8 attempts to compensate for the decrease in the lamp applied voltage E (t). However, since there is an inductive output impedance due to the magnetic flux leakage of the step-up transformer Tr and the inductance of the cable, the decrease in the lamp applied voltage E (t) is reduced. Is delayed, and as a result, a bending point K that is convex in a direction of a larger absolute value is generated. Further, the resonance between the inductive output impedance and the capacitance of the dielectric barrier discharge lamp 1 causes the inflection point K
After that, a vibration component with respect to the lamp applied voltage is mixed. As a result, a minimum point of the absolute value or a maximum point of the absolute value may occur on the lamp applied voltage waveform. Hereinafter, the vibration that occurs after the bending point K is called ringing, and the frequency is called the ringing frequency Fr. The time from the start of the discharge at the inflection point K until the applied voltage E (t) reaches the peak is τ, and the time from the peak P1 appearing after the inflection point K to the next peak P2 is T12. I do.

The present invention focuses on the change in the voltage applied to the lamp after the inflection point K, and effectively supplies power to the dielectric barrier discharge lamp without lowering the ultraviolet light emission efficiency. . That is, as described above, excimer molecules are generated when discharge occurs due to a sudden rise or fall of the lamp applied voltage E (t) waveform, and the generated excimer molecules are dissociated to generate ultraviolet rays. Excessive addition of discharge current during the period will destroy the excimer molecules. Therefore, it is desirable to cut off the discharge current promptly in terms of ultraviolet light emission efficiency.

However, as shown in FIG. 2, the discharge current continues from the start of the discharge at the bending point K until the lamp applied voltage E (t) reaches the first peak. Therefore, if the time τ from the start of the discharge to the peak of the applied voltage is long, the ultraviolet ray generation efficiency is reduced as a result. In the state where ringing occurs after the inflection point K, the discharge current continues until the voltage peaks. When the ringing frequency is low, it takes time until the discharge current stops, and as a result, the ultraviolet light emission efficiency decreases. That is, by shortening the time τ from the start of the above-described discharge to the peak of the applied voltage or by increasing the ringing frequency Fr, the dielectric barrier discharge lamp can be used without lowering the ultraviolet light emission efficiency. Can be discharged.

Here, the time τ from the start of the discharge until the applied voltage E (t) reaches the peak and the ringing frequency Fr are substantially the same as those of the circuit composed of the power supply device 8 and the dielectric barrier discharge lamp 1. It is determined by the inductance L and the capacitance C. By reducing these values, the time τ can be shortened and the ringing frequency can be increased. Here, since the discharge is completed around the first peak P1 (that is, the switch 11 in FIG. 19B is open at this time), after the first peak P1, FIG. 19B
The capacitance and stray capacitance of the capacitors 12 and 13 shown in
The applied voltage waveform E (t) changes oscillatingly at an oscillation frequency determined by the inductance L of the circuit. Since the discharge has ended immediately after the first peak P1 as described above, the time T12 from the first peak P1 to the second peak P2 is substantially equal to the electrostatic capacitance of the capacitors 12 and 13 described above. It corresponds to the period of the oscillation frequency determined by the capacitance and the stray capacitance, and the inductance L of the circuit.

In general, the resonance frequency of an LC resonance circuit can be calculated by the following equation. LC = 1 / (2πf) ² Therefore, assuming that the inductance of the circuit is L and the capacitance is C, the ringing frequency Fr is approximately 1
/ {2π × {(LC)}, and the value of the capacitance C depends on the capacitance of the dielectric barrier discharge lamp 1. Therefore, to increase the ringing frequency Fr (to shorten the time τ), What is necessary is just to make the value of the said inductance L small. Specifically, the ringing frequency Fr can be increased by reducing the coupling impedance of the step-up transformer Tr. Based on the above consideration, the present inventors examined the relationship between the time τ, the time T12 from the peaks P1 to P2, and the ultraviolet light emission efficiency, and the relationship between the ringing frequency and the ultraviolet light emission efficiency. As a result, FIGS.
As shown in FIG. 10, when the time τ is set to τ ≦ 2.1 μs, the time T12 is set to T12 ≦ 3 μs, or the ringing frequency Fr is set to Fr ≧ 300 kHz, the dielectric barrier discharge can be performed without lowering the ultraviolet light emission efficiency. It has been found that the lamp can be discharged.

Here, as described above, the ringing frequency Fr is generally determined by 1 / {2π × {(LC)}, so that the value of LC is expressed as LC ≦ 2.8 × 10 ⁻¹³ [unit of C Is F (Farad), and the unit of L is H (Henry). Since the value of LC is generally determined by the capacitance of the lamp 1 and the inductance of the transformer Tr, if the inductance of the transformer Tr is selected in accordance with the capacitance of the lamp 1 so that the LC value satisfies the above condition, Good.
The capacitance C may be measured by measuring the capacitance of the lamp in the unlit state with an impedance meter or the like.
Regarding the measurement of L, after the state of the primary side of the transformer Tr is simulated in accordance with the state immediately after the discharge at the time of lighting, the inductance of the secondary side is measured by an impedance meter or the like. I just need.

For example, when a full-bridge or half-bridge high-frequency AC power supply is used, the inductance of the secondary side may be measured while the primary side of the transformer is short-circuited. In the case of the push-pull method, the inductance of the secondary side may be measured with the middle point and one end of the primary side of the transformer Tr short-circuited and the other end opened. Further, in the case of the flyback method, the inductance of the secondary side may be measured with the primary side of the transformer Tr open. Note that, depending on the power supply device 8 used, the bending point K may not clearly appear on the applied voltage waveform. In particular, when a flyback type power supply is used, the bending point often does not clearly appear on the applied voltage waveform. In this case, the discharge current waveform Id (t) may be calculated as described above, and it may be estimated that the inflection point is located at the steep rising portion.

The invention according to claims 1 to 3,
Based on the above, practical conditions for efficiently discharging the dielectric barrier discharge lamp are defined, and by satisfying any of the following conditions, the dielectric barrier discharge lamp can be efficiently discharged. it can. (1) After the time when the voltage value at which the dielectric barrier discharge starts is reached, a voltage at which the time from reaching the maximum voltage value to reaching the next maximum voltage value is 3 μs or less is applied to the dielectric barrier discharge lamp. Apply. (2) A voltage in which the time from when the voltage value at which the dielectric barrier discharge starts to the time when the next lamp voltage is applied to the maximum voltage value becomes 2.1 μs or less is set to 2.1 μs or less. Apply to body barrier discharge lamp. (3) When the inductance of the circuit composed of the power supply device and the dielectric barrier discharge lamp is L and the capacitance is C, the inductance L and the capacitance C are selected so as to satisfy the following formula. LC ≦ 2.8 × 10 ⁻¹³

[0028]

Embodiments of the present invention will be described below. FIG. 3 is a diagram showing an example of a dielectric barrier discharge lamp lighting circuit according to an embodiment of the present invention. FIG. 3 shows a schematic configuration of a dielectric barrier discharge lamp lighting circuit using a full-bridge type inverter circuit. . FIG. 4 is a waveform diagram for explaining the operation of the above lighting circuit. FIG. 4 is a waveform diagram in the case where, for example, a capacitive load that does not cause a discharge phenomenon due to no primary or secondary leakage inductance of a transformer is connected. Is schematically shown. In the figure, Q1 to Q4 are switching elements (for example, FETs), G1 to G4 are gate signals of the switching elements Q1 to Q4, Vp is a primary side voltage of a step-up transformer Tr (hereinafter abbreviated as a transformer Tr), and Vs is a transformer. This is a secondary voltage of Tr.

The operation of the lighting circuit of FIG. 3 will be described with reference to FIG. (a) When the first gate signal G1 and the fourth gate signal G4 are turned on, the first switching element Ql and the fourth switching element Q4 are turned on by the gate drive circuits GD1 and GD4 (FIG. 3), A DC voltage is applied to the primary side of the transformer Tr from the DC power supply DC (the same figure), a voltage is generated on the secondary side of the transformer Tr, and a voltage is applied to the dielectric barrier discharge lamp 1 (the same figure). (b) When the first gate signal G1 and the fourth gate signal G4 are turned off (the same figure), the first switching element Ql and the fourth switching element Q4 are cut off, and the primary side voltage Vp of the transformer Tr is set. , Secondary voltage Vs of transformer Tr
Is the leakage inductance of the transformer Tr and the transformer T
The unstable fluctuation starts at a speed related to the resonance frequency determined from the secondary-side capacitance of r (FIG. 1). (c) When the second gate signal G2 and the third gate signal G3 are turned on, the gate drive circuits GD2 and GD3 turn on the second switching element Q2 and the third switching element Q3 (FIG. 3), A DC voltage in the opposite direction to the above (a) is applied to the primary side of the transformer Tr,
A voltage in the direction opposite to the above (a) is generated on the secondary side, and a voltage in the opposite direction is applied to the dielectric barrier discharge lamp 1 (FIG. 1). (d) When the second gate signal G2 and the third gate signal G3 are turned off (circled numeral 10 in the figure), the second switching element Q
2. The third switching element Q3 is turned off, and the primary voltage Vp of the transformer Tr and the secondary voltage Vs of the transformer Tr depend on the leakage inductance of the transformer Tr and the secondary capacitance of the transformer Tr. The unstable fluctuation starts at a speed related to the determined resonance frequency (see circles 11 and 12 in the figure).
). (e) Hereinafter, the operations of (a) to (d) are repeated.

5 and 6 are measured data of the applied voltage waveform E (t) and the current waveform I (t) in the lighting circuit. FIG.
Is an enlarged view of the section Y1 in FIG. 5, and the waveform is measured under the following conditions. Note that this condition is a condition under which the lighting circuit of FIG. 3 can be lighted most efficiently. -Frequency: 33.9 kHz-Transformer Tr primary inductance: 1.42 mH Secondary inductance: 204 mH Coupling impedance: 0.99995-Dielectric barrier discharge lamp Dielectric: quartz glass-thickness 1 mm Discharge gas: xenon-pressure 33 kPa Discharge gap: 4.3 mm Lamp capacitance without discharge: 84 pF

FIG. 7 is an analysis and calculation of the discharge current waveform Id (t) in FIGS. 5 and 6, and in addition to the applied voltage waveform E (t) and the current waveform I (t), the discharge current waveform Id (t). ), And shows the section Y2 in FIG. 6 in an enlarged manner. The conditions for the above analytical calculation are as follows. -Capacitance of the discharge plasma space: C1: 97.2 pF-Capacitance of the dielectric: C2: 607 pF-Floating capacitance: C3: 70 pF In FIG. 7, the inflection point K clearly appears. T
Since the discharge current waveform Id (t) rapidly rises at d, it can be seen that the inflection point K is the discharge start point.
The time from the inflection point K to the next first peak P1 is the above-mentioned time τ, and the time from the first peak P1 to the second peak P1 is the above-mentioned time T.
The applied voltage waveform E (t) is oscillating after the first peak P1.

In the lighting circuit shown in FIG. 3, an inductance was added to the secondary side of the transformer Tr to adjust the ringing frequency (time τ or time T12) to light the lamp, and the luminous efficiency was obtained. 8, 9, and 10, the luminous efficiency, time τ, time T12, and
The relationship between the ringing frequency Fr is shown. FIG. 11 shows an applied voltage waveform E (t) and a current waveform I (t) when the ringing frequency is reduced to 250 Hz. As is clear from FIGS. 8, 9 and 10, the time τ is 2.1 μs or less, the time T12 is 3 μs or less, or the ringing frequency F
It can be seen that setting r to 300 Hz or more is effective from the viewpoint of increasing efficiency. Curves a, b, and c in FIGS. 8, 9, and 10 show the efficiency when the applied voltage of the lamp is changed. V1 <V2 <V3 when V2 and the applied voltage of the curve c are V3. Also,
At that time, the relative light amount was 1 for curve a, 1.33 for curve b, and 1.67 for curve c.

FIG. 12 shows another waveform of the voltage E (t) applied to the lamp,
FIG. 6 shows actual measurement data of the current Is (t) waveform, and FIG. 6 shows an example in which the inflection point K of the voltage indicating the start of discharge does not clearly appear. When the inflection point K does not clearly appear as described above, as described above, the capacitance C1 of the capacitor 12 in the discharge plasma space 2, the capacitance C2 of the capacitor 13 in the dielectrics 5, 6, and the dielectric The discharge start point can be known by obtaining the discharge current waveform Id (t) from the floating capacitance C3 existing in parallel with the barrier discharge lamp according to the above equation (1).

FIG. 13 shows the discharge current waveform Id (t) as described above.
FIG. 9 is a diagram showing the calculated values of the applied voltage E (t) and the current Is (t) together with the calculated values. The experimental conditions and the analysis conditions of the discharge current waveform Id (t) are as follows. -Inverter method of power supply device: push-pull method-Analysis conditions Capacitance of discharge plasma space: C1: 8.7 pF Capacitance of dielectric: C2: 140 pF Floating capacitance: C3: 10 pF Referring to FIG. At Td, the discharge current waveform Id (t) sharply rises, and it can be seen that this time is the discharge start time. Therefore, the point on the waveform of the applied voltage E (t) corresponding to the time point Td corresponds to the inflection point K, and the time τ can be obtained by measuring the time from this inflection point K to the next peak P1. In this example, the first peak P1 and the second peak P2 clearly appear, and the time T1
2 can be immediately obtained from the applied voltage waveform E (t).

FIG. 14 is a diagram showing a configuration example in which a push-pull type inverter circuit is used for a lighting circuit. Also,
FIG. 15 is a waveform diagram for explaining the operation of the lighting circuit. As shown in FIG. 15, for example, a capacitive load that has no leakage inductance between the primary and secondary transformers and does not cause a discharge phenomenon is connected. 5 schematically shows the waveform when the above-mentioned operation is performed.
In the figure, G1 and G2 are switching elements Q1 to Q
2, a gate signal V1, V2 is a primary voltage of the transformer Tr, and Vs is a secondary voltage of the transformer Tr. The operation of the lighting circuit of FIG. 3 will be described with reference to FIG.

(A) When the first gate signal G1 is turned on,
The first switching element Q is provided by the gate drive circuit GD1.
1 becomes conductive (the same figure), and a DC voltage is applied from the DC power supply DC to the primary side first coil L1 of the transformer Tr (the same figure). Since the transformer primary side first coil L1 and the transformer secondary side coil Ls have opposite directions, the transformer
A voltage in a direction opposite to that of the transformer primary side first coil L1 is generated in the secondary side coil Ls, and a voltage is applied to the dielectric barrier discharge lamp 1 (FIG. 1). (b) When the first gate signal G1 is turned off, the first switching element Q1 is cut off, and the first primary switching element Q1 is turned off.
Coil voltage V1, transformer primary side second coil voltage V2,
The transformer secondary-side voltage Vs starts to fluctuate unstablely at a speed related to the resonance frequency determined by the leakage inductance of the transformer Tr and the secondary-side capacitance of the transformer Tr (FIG. 1). (c) When the second gate signal G2 is turned on, the second switching element Q2 is turned on (the same figure), and a DC voltage is applied to the transformer primary-side second coil L2 from the DC power supply DC (the same). Figure). Since the transformer primary-side second coil L2 and the transformer secondary-side coil Ls have the same direction, a voltage in the same direction as the transformer primary-side second coil L2 is generated in the transformer secondary-side coil Ls, and the dielectric A voltage is applied to the barrier discharge lamp 1 (FIG. 1). (d) When the second gate signal G2 is turned off, the second switching element Q2 is turned off (circled numeral 10 in the figure), the transformer primary side first coil voltage V1, and the transformer primary side second
The coil voltage V2 and the transformer secondary-side voltage Vs begin to fluctuate unstablely at a speed related to the resonance frequency determined by the leakage inductance of the transformer Tr and the secondary-side capacitance of the transformer Tr. 11,12). (e) Hereinafter, the above operations (a) to (d) are repeated.

As is clear from the above description, when the push-pull type inverter circuit is used as the lighting circuit, the voltage waveform applied to the dielectric barrier discharge lamp is the case where the above-described full bridge type inverter circuit is used. Τ, time T12,
Further, the ringing frequency Fr can be obtained.
Although not shown, the same applies to the case where a half-bridge type inverter circuit is used.

FIG. 16 is a diagram showing a configuration example of a lighting circuit using a flyback type inverter circuit, and FIG. 17 is a diagram showing a configuration of a dielectric barrier discharge lamp using a lighting circuit using a flyback type inverter circuit. This is actually measured data of an applied voltage E (t) waveform and a current Is (t) waveform. As shown in FIG. 17, when a flyback type inverter circuit is used as the lighting circuit, the waveform of the voltage E (t) and the current Is (t) applied to the dielectric barrier discharge lamp are the same as those of the full bridge described above. , Half-bridge, push-pull type inverter circuit. However, even when the flyback type inverter circuit is used, the lamp can be efficiently turned on similarly to the above by paying attention to the change in the voltage applied to the lamp after the inflection point K.

Hereinafter, a case where the dielectric barrier discharge lamp is lit by a lighting circuit using a flyback type inverter circuit will be described. FIG. 18 is a diagram schematically showing the waveforms of FIG. 17 and the waveforms of various parts of the circuit obtained by simulation. In the figure, E (t) is
In 6, the secondary side voltage waveform of the transformer Tr (voltage waveform applied to the dielectric barrier discharge lamp), Is (t) is the lamp current waveform, Id (t) is the discharge current waveform obtained by the above-described analytical calculation, and Vq (t). Is a voltage waveform applied to the switching element (for example, FET) Q, Iq (t) is a current waveform flowing through the switching element Q, Ir (t) is a current waveform flowing through the diode D1,
G (t) is a gate signal input to the gate drive circuit GD.

The operation of the lighting circuit shown in FIG. 17 will be described with reference to FIG. (a) When the gate signal G (t) is turned on only during the time t1 to t2, the current Iq (t) flowing through the switching element Q increases almost linearly and is suddenly cut off at the time t2. Current I
In response to the current immediately before q (t) is disconnected, the transformer Tr
Magnetic energy stored in the core of the transformer Tr appears in the form of a voltage on the primary and secondary sides of the transformer Tr, and on the secondary side of the transformer Tr, a high voltage boosted according to the turns ratio of the transformer Tr is present. Appears and is applied to the dielectric barrier discharge lamp 1. (b) When a high voltage is applied to the lamp 1, the lamp discharges at time ta, and a bending point K1 occurs in the waveform of the applied voltage E (c). However, the bending point K1 is not clearly shown in FIG. When a discharge occurs, the voltage in the discharge space is rapidly neutralized to almost zero. (d) At a resonance frequency substantially determined by the capacitance of the lamp 1 and the secondary side inductance of the transformer Tr, the lamp applied voltage E (t) causes resonance oscillation. (e) When the lamp applied voltage E (t) becomes a low voltage, the time t
A high voltage in the opposite direction is generated in the discharge space due to the neutralization of the voltage in the discharge space by the discharge in a. Thereby, at time Tb, re-discharge occurs,
An inflection point K2 occurs. However, the bending point K2 is not clearly shown in FIG. (f) The resonance vibration of the lamp applied voltage E (t)
Appearing on the primary side of the switching element Q, the voltage V
q (t) varies as shown in FIG.

(G) During the period when the voltage Vq (t) is positive, substantially no current flows on the primary side of the transformer Tr. However, when the diode D1 is connected in parallel with the switching element Q, a current flows through the diode D1 during the period Tz from t3 to t4 when the voltage Vq (t) tends to become negative. This can be interpreted as that the transformer having a large impedance on the primary side suddenly decreases. Therefore, free resonance oscillation of the lamp applied voltage E (t) is hindered, and a period Tr in which the voltage change of the voltage E (t) stops correspondingly occurs.

As described above, in the case of the flyback lighting circuit, the discharge current Id (t) is discharged at the time Ta, Tb where the rising of the discharge current Id (t) is relatively difficult to understand from the waveform of the lamp applied voltage E (t). Has started, and from this point the bending point K
Can be determined. That is, even when the flyback type inverter circuit is used, the time τ from the inflection point K indicating the start of discharge to the next peak can be obtained, and the time τ is set to 2.1 μs or less as described above. By selecting the inductance of the transformer Tr in such a manner, the lamp can be efficiently turned on.

As described above, in the case of a flyback type lighting circuit using the switching element Q to which an anti-parallel diode is connected (or has a built-in anti-parallel diode), as described above, First peak P
Between the first and second peaks P2 there is a period Ts during which the essentially insignificant voltage change has stopped. Therefore, the time T12 between the first and second peaks has no meaning, and the relationship in FIG. 9 does not hold. As described above, when the impedance of the circuit changes during the operation, attention should be paid to the application of the present invention. In the case of a full-bridge, half-bridge or push-pull inverter circuit using a switching element to which an anti-parallel diode is added (or built-in), the primary side of the transformer is always The above problem does not occur because it is connected to the power supply with low impedance. However, when the gate signal is turned off and the current flowing through the anti-parallel diode stops, the impedance increases thereafter, so that the lamp has a low resonance frequency that is generally determined by the lamp capacitance and the secondary inductance. The applied voltage E (t) starts resonance oscillation and the ringing disappears. Note that the discharge may not be completed even after the first peak, but at this time, T12 is slightly longer than the subsequent ringing cycle. The extent to which the length is increased depends on the structure of the lamp, that is, the distribution of the capacitance C1 of the capacitor 12 in the discharge plasma space 2 and the capacitance C2 of the capacitor 13 in the dielectrics 5, 6. Even in such a case, it is desirable if the light source device can be configured so that T12 ≦ 3 μs is maintained. Conversely, in such a case, T12 ≦ 3μ
Even if s is not satisfied, the discharge after passing the first peak is generally weak and has a small effect on the ultraviolet light emission efficiency, so that LC ≦ 2.8 × 10 ⁻¹³ or τ ≦
The light source device may be configured to satisfy any one of 2.1 μs. Note that the present invention provides a dielectric barrier discharge lamp that emits ultraviolet light that does not have a phosphor applied to the inner surface of the discharge vessel and a dielectric barrier discharge lamp that emits visible light that has a phosphor applied to the inner surface of the discharge vessel. Can also be applied.

[0044]

As described above, in the present invention,
After the time when the voltage value at which the dielectric barrier discharge starts is reached, a voltage is applied to the dielectric barrier discharge lamp such that the time from reaching the maximum voltage value to reaching the next maximum voltage value is 3 μs or less, 1. The time from when the voltage value at which the dielectric barrier discharge is started to when the voltage value reaches the maximum voltage value in the period until the next lamp voltage is applied is 2.
When a voltage of 1 μs or less is applied to the dielectric barrier discharge lamp, and the inductance of a circuit composed of the power supply device and the dielectric barrier discharge lamp is L and the capacitance is C, the inductance L and the capacitance C Is LC ≦ 2.8 ×
Since the discharge current is selected so as to satisfy 10 ^-13 , the discharge current that destroys excimer molecules can be rapidly cut, and the luminous efficiency of the dielectric barrier discharge lamp can be improved using a feasible power supply device. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of a dielectric barrier discharge lamp light source device.

FIG. 2 shows a lamp applied voltage E in a practical power supply device.
(t) is a diagram showing typical waveforms of a discharge gap voltage V1 (t), a current Is (t), and a discharge current Id (t).

FIG. 3 is a diagram showing an example of a dielectric barrier discharge lamp lighting circuit (full bridge system) according to an embodiment of the present invention.

FIG. 4 is a waveform chart for explaining an operation of the lighting circuit of FIG. 3;

5 shows an applied voltage waveform E (t) in the lighting circuit of FIG. 3,
FIG. 6 is a diagram showing actually measured data of a current waveform I (t).

6 shows an applied voltage waveform E (t) in the lighting circuit of FIG. 3,
FIG. 4 is a diagram (enlarged view) showing measured data of a current waveform I (t).

FIG. 7 is an enlarged view of a portion Y2 in FIG. 6 to which a discharge current waveform Id (t) obtained by calculation is added.

FIG. 8 is a diagram showing a relationship between time τ and luminous efficiency η.

FIG. 9 is a diagram showing a relationship between time T12 and luminous efficiency η.

FIG. 10 is a diagram showing a relationship between a ringing frequency Fr and a light emission efficiency η.

11 shows an applied voltage waveform E (t) when the ringing frequency is reduced to 250 Hz in the lighting circuit of FIG. 3,
FIG. 3 is a diagram showing a current waveform I (t).

FIG. 12 is a diagram showing a lighting waveform of another lamp.

FIG. 13 is an enlarged view of a portion Z in FIG. 12 and added with a discharge current waveform Id (t) obtained by calculation.

FIG. 14 is a configuration example of another lighting circuit (push-pull method)
FIG.

FIG. 15 is a waveform chart for explaining the operation of the lighting circuit of FIG. 14;

FIG. 16 is a diagram illustrating a configuration example of a lighting circuit of a flyback system.

FIG. 17 is a diagram showing actually measured data of an applied voltage waveform E (t) and a current waveform I (t) when a flyback lighting circuit is used.

FIG. 18 is a diagram showing waveforms of respective parts when a flyback type lighting circuit is used.

FIG. 19 is a diagram showing a dielectric barrier discharge lamp having two dielectrics and an equivalent circuit showing its electrical operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dielectric barrier discharge lamp 2 Discharge plasma space 3, 4 electrode 5, 6 Dielectric 7 Lamp enclosure 8 Power supply device 9 High frequency AC power supply Tr Boosting transformer Q1-Q4 Switching element (FET) GD Gate drive circuit GD1-GD4 Gate drive Circuit D1 to D4 Diode DC power supply

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01J 65/00

Claims (3)

(57) [Claims] 1. A discharge plasma space filled with a discharge gas for generating excimer molecules by a dielectric barrier discharge, wherein at least one of electrodes of both electrodes for inducing a discharge phenomenon in the discharge gas and the discharge plasma space. Dielectric barrier discharge lamp light source device having a dielectric barrier discharge lamp having a structure in which a dielectric is interposed between discharge gases, and a power supply device for applying a high voltage to the electrodes of the dielectric barrier discharge lamp Wherein the power supply device applies a high voltage having a substantially periodic waveform to the dielectric barrier discharge lamp via a step-up transformer, and the applied voltage waveform is a voltage at which a dielectric barrier discharge is started. A dielectric barrier discharge lamp wherein the time from when the maximum value is reached to when the next maximum value is reached is 3 μs or less. Source apparatus. 2. A discharge plasma space filled with a discharge gas for generating excimer molecules by a dielectric barrier discharge, wherein at least one of electrodes of both electrodes for inducing a discharge phenomenon in the discharge gas and the discharge plasma space. Dielectric barrier discharge lamp light source device having a dielectric barrier discharge lamp having a structure in which a dielectric is interposed between discharge gases, and a power supply device for applying a high voltage to the electrodes of the dielectric barrier discharge lamp Wherein the power supply device applies a high voltage having a substantially periodic waveform to the dielectric barrier discharge lamp via a step-up transformer, and the applied voltage waveform is a voltage for starting a dielectric barrier discharge. It is noted that the time from when the voltage reaches the maximum voltage value to the time when the next new lamp voltage is applied is 2.1 μs or less. The dielectric barrier discharge lamp light source device according to. 3. A discharge plasma space filled with a discharge gas for generating excimer molecules by a dielectric barrier discharge, wherein at least one of electrodes of both electrodes for inducing a discharge phenomenon in the discharge gas and the discharge plasma space. Dielectric barrier discharge lamp light source device having a dielectric barrier discharge lamp having a structure in which a dielectric is interposed between discharge gases, and a power supply device for applying a high voltage to the electrodes of the dielectric barrier discharge lamp In the above, the power supply device may apply a high voltage having a substantially periodic waveform to the dielectric barrier discharge lamp via a boosting transformer, and may include an inductance of a circuit including the power supply device and the dielectric barrier discharge lamp. Is L and the capacitance is C,
The dielectric barrier discharge lamp light source device, wherein the inductance L and the capacitance C are selected so as to satisfy the following formula: LC ≦ 2.8 × 10 ⁻¹³ .