JP2001093684A - Outside electrode type discharge lamp apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently produce excimer molecules in a discharge lamp and to acquire a stable quantity of light emission, without being affected by the load condition of the discharge lamp or the condition of circuits of a lighting device and the like, or without complicated adjustment of the condition of circuits between the lighting device and the discharge lamp, etc. SOLUTION: This outside electrode type discharge lamp apparatus consists of a discharge lamp 1 and a lighting device. At least one of electrodes 5 and 6 of the discharge lamp 1 is mounted outside of a lamp sealing material 7 consisting of dielectrics 3 and 4. In the lighting device, the primary sides of a DC power supply 9, a switching element 13 and a transformer 10 are connected in series and the electrodes of the discharge lamp 1 are connected to the secondary side of the transformer 10. The lighting device applies a voltage, consisting of an oscillating voltage period for making the discharge lamp 1 glow and a constant voltage period for making the discharge lamp 1 not to glow, and starts the on-signal period for a switching element 13 from the constant voltage period, when an electric current is flowing in the direction opposite to the direction of an electric current sent by the switch element 13 based on the on-signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an external electrode type discharge lamp device, and more particularly to an external electrode type discharge lamp device which generates excimer molecules in a discharge lamp by dielectric barrier discharge and uses light emitted from the excimer molecules. The present invention relates to a discharge lamp device.

[0002]

2. Description of the Related Art As a prior art, Japanese Unexamined Patent Publication No. 2-7353 discloses a method in which a discharge vessel is filled with a discharge gas for generating excimer molecules, and excimer molecules are generated by a dielectric barrier discharge, also known as an ozonizer discharge or a silent discharge. An emitter for extracting light emitted from an excimer molecule is described.

FIG. 8 shows an example of a lighting device for such an external electrode type discharge lamp.

In FIG. 1, a dielectric barrier discharge lamp 1 is shown.
01 has electrodes 10 sandwiching discharge plasma space 102 therebetween.
Two dielectrics 105 and 106 are provided between 3 and 104. In this case, a lamp envelope 107 constituting the dielectric barrier discharge lamp 101 also serves as the dielectrics 105 and 106.

The dielectric barrier discharge lamp 101 is lit between electrodes 103 and 104, for example, from 10 kHz to 2 kHz.
A high-frequency AC voltage of 00 kHz, 2 kV to 10 kV is applied from the power supply device 108. The current supplied from the power supply device 108 is supplied to the discharge plasma space 102 and the electrodes 103 and 1.
Since the dielectrics 105 and 106 intervene between the electrodes 04, current does not flow directly from the electrodes 103 and 104 to the discharge plasma space 102, but current flows due to the action of the capacitors of the dielectrics 105 and 106. That is, each of the dielectrics 105, 1
On the opposite surfaces of the discharge plasma space 102, electric charges having the same sign as the surface on the side of each of the electrodes 103 and 104 are induced by polarization of the dielectric, and discharge is performed between these surfaces.

Since little current flows along the inner surface of the discharge plasma space 2 of the dielectrics 105 and 106, the dielectric 1
The electric charge induced on each surface of the discharge plasma space 2 at 05 and 106 is neutralized by the electric charge moved by the discharge, and the electric field of the discharge plasma space 102 is reduced.
Even if the voltage application to 3,104 is continued, the discharge current eventually stops. The discharge continues when the voltage applied to the electrodes 103 and 104 further rises. However, after the discharge occurs once, when the discharge stops, the polarity of the voltage applied to the electrodes 103 and 104 is reversed. Do not re-discharge.

When xenon gas is used as the sealing gas, xenon gas becomes xenon plasma separated into ions and electrons by discharge. In this plasma, xenon excited to a specific energy level is combined with each other to generate excimer molecules. Excimer molecules are dissociated after a certain lifetime, and at the time of this dissociation, they emit photons of a vacuum ultraviolet wavelength, which are used as a vacuum ultraviolet light source.

In order to operate the discharge lamp efficiently as a vacuum ultraviolet light source, it is important to efficiently generate excimer molecules. A major factor that hinders efficient excimer molecule generation is that the discharge plasma is excited to an energy level that does not contribute to excimer molecule generation. Since the electron motion of the discharge plasma immediately after the start of the discharge is collective and the discharge energy is high but the temperature is low, the discharge plasma has a high probability of transitioning to the resonance state necessary to form excimer molecules. ,
If the discharge energy is too large or the discharge time is long, the electron motion of the discharge plasma gradually becomes thermal, that is, a thermal equilibrium state called Maxwell-Boltzmann distribution, so that the plasma temperature rises and excimer molecules cannot be generated. Note that the probability of transition to a higher excited state increases.

[0009] Even when excimer molecules are generated, the excimer molecules may be destroyed by a subsequent discharge before the desired photons are emitted after the lifetime elapses and the spontaneous dissociation occurs. For example, in the case of xenon excimer, 1 micron
A period of about s is required, but if a subsequent discharge or re-discharge is performed during this period, the efficiency of excimer light emission is reduced.

That is, once the discharge has started, it is very important that the required electric power is applied to the plasma in a short time and the discharge is terminated as soon as possible, thereby minimizing the energy of the subsequent discharge as much as possible. is there.

JP-A-9-199285 and JP-A-10-223384 disclose a discharge lamp lighting device for efficiently generating excimer molecules. These devices constitute a so-called flyback inverter lighting system in which a DC power supply, a primary side of a transformer, and switch elements such as transistors and FETs are connected in series and a discharge lamp is connected to a secondary side of the transformer. In the former publication, the pulse width of the lamp application voltage is defined as a condition for efficiently realizing the generation of excimer molecules, and in the latter publication, the rising of the lamp application voltage is used. It specifies the time.

[0012]

However, the lighting devices described in each of the above publications basically have one switch element.
Although it has the economical advantage of low cost because it requires only one piece, on the other hand, since the generation of high voltage is realized by turning off the switch element, the operation is easily affected by the load impedance, There is also a problem that the amount of light obtained from the discharge lamp becomes unstable.

Furthermore, the lighting device disclosed in the latter publication must be achieved by adjusting the inductance of the step-up transformer in order to satisfy the above condition, and there is a problem that the degree of freedom in design is low.

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, it is an object of the present invention to efficiently generate excimer molecules in a discharge lamp and to be affected by a load state of the discharge lamp, a circuit condition of a lighting device, and the like. It is an object of the present invention to provide an external electrode type discharge lamp device capable of obtaining a stable light emission amount without troublesome adjustment of circuit conditions between the lighting device and the discharge lamp.

[0015]

In order to achieve the above object, the present invention employs the following means.

The first means is to connect in series a discharge lamp having at least one of electrodes provided outside a lamp envelope made of a dielectric, a DC power supply, a switch element, and a primary side of a transformer. An external electrode type discharge lamp device comprising: a lighting device in which an electrode of the discharge lamp is connected to a secondary side of the transformer; wherein the lighting device has an oscillating voltage period for causing the discharge lamp to emit light and emitting the discharge lamp. A voltage consisting of a constant voltage period not to be applied is applied to the discharge lamp, and an ON signal period of the switch element starts from a constant voltage period in which a current flows in a direction opposite to a direction in which the switch element conducts by the ON signal. It is characterized by doing.

A second means is the first means, wherein the ON signal period of the switch element is started from a constant voltage period which first appears after the switch element is turned OFF.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a diagram showing the configuration of an external electrode type discharge lamp device according to this embodiment.

In FIG. 1, reference numeral 1 denotes a discharge lamp, 2 denotes a lamp envelope forming a discharge space of the discharge lamp 1 composed of a glass tube or the like, and 3 and 4 denote dielectrics formed by the lamp envelope 2 itself. , 5 and 6 are external electrodes formed on the outer surface of the lamp envelope 2 corresponding to the dielectrics 3 and 4, respectively.
Is a discharge plasma space formed by the lamp envelope 2,
Reference numeral 8 denotes a lighting device for supplying a flyback voltage described below between the external electrodes 5 and 6.

The lighting device 8 includes a DC power supply 9 and a primary winding 1.
A step-up transformer 10 having primary and secondary windings 12;
A switch element 13 comprising an FET 14 and a built-in diode 15; and a gate drive circuit 16 for driving the FET 14
It is composed of

Although an example has been described in which the FET 14 incorporating the diode 15 is used as the switch element 13, the diode may be reversely connected to another semiconductor element such as a transistor.

FIG. 2 is a sectional view of a discharge lamp when a discharge lamp 1 is a straight tube external electrode type discharge lamp.

1, the same reference numerals as those shown in FIG. 1 denote the same parts, reference numeral 21 denotes a covering tube made of a telescopic resin or the like which covers the outer surface of the lamp envelope 2, reference numeral 22 denotes an aperture portion, Is a fluorescent substance.

This external electrode type discharge lamp is composed of a straight tubular glass tube 2 whose both ends are hermetically sealed, and a fluorescent substance 23 is coated on the inner surface of the glass tube 2. An aperture 22 for light emission extending in the length direction that is not provided is formed. A predetermined amount of a rare gas such as xenon is sealed in the inside of the glass tube 2, and the outer surface of the glass tube 2 is diametrically opposed to each other in the length direction of the glass tube 2. A pair of film-shaped electrodes 5 and 6 extending are arranged.

Here, the fluorescent substance 23 is applied as needed, and is unnecessary in the case of an external electrode type discharge lamp which emits ultraviolet rays.

FIG. 3 is a diagram showing an equivalent circuit of the discharge lamp 1.

In the figure, C1 is a discharge plasma space 7
C2 is the capacitance of the dielectrics 3 and 4, C3 is the stray capacitance, R is the load resistance, SW1 is the equivalent switch during discharge and non-discharge, and the discharge lamp 1 has the capacitance as a whole. It can be expressed as a combined impedance consisting of load resistance.

FIGS. 4 and 5 are diagrams showing voltage and current waveforms at various parts in the external electrode type discharge lamp device shown for comparison with the present invention.

FIG. 6 is a diagram showing voltage and current waveforms at various parts in the external electrode type discharge lamp device according to this embodiment.

Next, the operation of the external electrode type discharge lamp device according to this embodiment will be described with reference to FIGS.

Here, the FET 14 is a gate drive circuit 1
6 is supplied to the gate terminal of the FET 14 and turned on when the gate signal Gt is at a high level,
It shall be off at low level.

First, as shown in FIG. 4A, when the gate signal Gt is applied and the FET 14 is turned on, the voltage from the DC power supply 9 is applied to the primary winding 11 of the step-up transformer 10, and As shown in (b), the primary current Ipt starts to flow. The primary side current Ipt linearly increases in proportion to the length of the period in which the FET 14 is on, and accumulates magnetic energy in the core of the step-up transformer 10. FE
When T14 is turned off after a predetermined period, the primary-side current Ipt is sharply cut off. Therefore, as shown in the oscillating voltage period A1 of FIG. As a result, a secondary voltage multiplied by the number of turns is also induced in the secondary winding 12, and this is applied to the external electrodes 5 and 6 of the discharge lamp 1 as a lamp applied voltage Vst. .

The voltage Vst applied to the lamp is
0 secondary inductance and the discharge lamp 1 shown in FIG.
And increases at a speed based on the resonance frequency determined by the capacitance. When the voltage of the discharge plasma space 7 of the discharge lamp 1 reaches the discharge starting voltage, discharge is started, and a discharge current Idt flows into the discharge plasma space 7 as shown in FIG. It should be noted that the discharge current Idt shown in FIG. 3 conceptually represents the flow of charges in the discharge plasma space 7 and is not the same as the secondary current Ist of the step-up transformer 10.
It is impossible to measure directly. Thereafter, when the lamp applied voltage Vst approaches 0 volts in accordance with the resonance phenomenon, the electric discharge formed in the discharge plasma space 7 by the previous discharge causes the electric field attached to the dielectrics 105 and 106 to form an electric field. Discharge occurs in the opposite direction, and a discharge current Idt having a polarity opposite to that of the previous discharge current flows.

Thereafter, under the condition that the drain voltage of the FET 14 is going to be negative, a current flows through the built-in diode 15, so that the voltage induced in the primary winding 11 and the secondary winding 12 of the step-up transformer 10 is As shown in the constant voltage periods A2 and A3 in FIG.

The main discharge current Idt so far is shown in FIG.
This is two discharges in the period B1 shown in (d), which occupies most of the power input to the discharge lamp 1. Usually, the above-mentioned resonance phenomenon is continued and the lamp applied voltage Vst oscillates. As long as the condition that the voltage of the plasma space 2 reaches the discharge starting voltage of the discharge lamp 1 can be satisfied, FIG.
The start and stop of the discharge are repeated as shown in a period B2 of (d). Since the resonance frequency of the resonance circuit is set sufficiently higher than the frequency of the gate signal Gt,
At the time when t becomes a high level, the lamp applied voltage Vst
Is sufficiently small, and the discharge current Idt does not flow.

However, when the resonance frequency is high as described above, the discharge lamp 1 does not discharge uniformly, and an inconvenient phenomenon (light distribution) in which a specific portion such as a center portion or an end portion in the lamp axis direction becomes locally dark. Non-uniformity). In order to reduce the resonance frequency in order to improve such non-uniform light distribution, it is necessary to increase the inductance of the step-up transformer 10. However, if the inductance is increased without changing the turns ratio of the primary winding 11 and the secondary winding 12 in order to prevent the primary side voltage from rising when the FET 14 is turned off, the slope of the primary side current Ipt , It takes time to store magnetic energy, and it is necessary to increase the on-time of the gate signal Gt in order to store sufficient magnetic energy. However, this is shown in FIG.
If the gate signal Gt shown in (1) takes a long on-period, the frequency of the gate signal Gt will change. However, the frequency of the gate signal Gt cannot be largely changed in order to keep the brightness of the lamp constant. Therefore, it is better to turn on the gate signal Gt of the FET 14, that is, to advance the gate start timing.

FIG. 5 shows the timing of starting the gate of the gate signal Gt of the FET 14 earlier than that shown in FIG.

In this driving method, when the gate signal Gt goes high, almost the voltage of the DC power supply 9 is induced in the primary winding 11, so that the resonance circuit induced in the secondary winding 12 Is erased, but there is a possibility that the discharge current Idt (C3) may or may not flow due to a slight shift in gate timing of the gate signal Gt. Even if the driving conditions are set so that the discharge current Idt (C3) does not flow (or flow), the resonance frequency changes due to a rise in the lamp temperature or the temperature of the transformer core after lighting, The discharge current Idt (C3) flows (or stops flowing)
There are some cases like this. In such a case, the discharge current Idt
Since the average light emission amount changes by an amount corresponding to (C3), a jump occurs in the brightness of the lamp.

Here, even if the resonance frequency changes due to a rise in temperature, for example, the frequency of the gate signal Gt, the secondary side inductance of the transformer, and the static of the lamp so that the appearance and disappearance of the discharge current Idt (C3) do not occur. Set the capacity,
If an attempt is made to set the timing at which the gate signal Gt becomes high level at a position distant from the discharge current Idt (C3), the appearance or disappearance of the discharge current Idt (C2 or C4) may occur. In addition, since the frequency of the gate signal Gt, the secondary side inductance of the transformer, and the capacitance of the lamp have manufacturing variations, the discharge current Idt
(C2 or C4) cannot always be manufactured so as not to appear or disappear. Furthermore, even if the lamp and the lighting device are combined and adjusted to absorb variations, if the routing of the cable connecting the lamp and the lighting device changes, the stray capacitance at that portion changes, The resonance frequency changes, and the discharge current appears or disappears.

FIG. 6 shows voltage and current waveforms at various parts of the external electrode type discharge lamp device when the external electrode type discharge lamp device is driven by the driving method according to the present embodiment in consideration of the above problems. 4 is different from those of FIGS. 4 and 5 in that the time when the gate signal Gt is turned on is determined by the built-in diode 1.
5, a flat voltage period A2 induced in the primary winding 11 and the secondary winding 12 of the step-up transformer 10, that is, the ON signal period of the FET 13
3 is performed in a constant voltage period A2 in which a current flows in a direction opposite to the direction in which the current is conducted by the ON signal.

In the driving method of the present embodiment, FIG.
As shown in (c), the oscillation voltage period A1 is based on the resonance frequency determined by the secondary inductance of the step-up transformer 10 and the capacitance of the discharge lamp 1 shown in FIG. , A steep secondary voltage of the opposite polarity is induced, and then this voltage is inverted to a positive polarity. In the constant voltage period A2, even if the primary side voltage of the step-up transformer 10 inverted to the positive polarity is going to become higher than the voltage of the DC power supply 9, as shown in FIG. Since the secondary current Ipt flows, the primary voltage in the constant voltage period A2 is substantially maintained at the voltage value of the DC power supply 9. In the constant voltage period A2, as described above, the FET 14
Is gated on by the gate signal Gt, but the primary current I in the reverse direction is applied to the built-in diode 15 as described above.
pt continues to flow, and the conduction current by the FET 14 does not flow. Next, a constant voltage period A4 is reached, and the primary current I
When the current direction of pt reverses, no current flows through the built-in diode 15, and if the gate of the FET 14 is not turned on, the primary side circuit of the step-up transformer 10 is cut off. The oscillation starts at a resonance frequency determined by the side inductance and the capacitance of the discharge lamp 1 shown in FIG. 3, but in this constant voltage period A4, as shown in FIG. Is gate-on, so FET1 immediately
4, the voltage of the DC power supply 9 is applied to the primary winding 11, and the primary current Ipt starts flowing from the DC power supply 9 to the primary winding 11 as shown in FIG. Electromagnetic energy is stored in 10. In the period A4, as shown in FIG. 6C, the secondary voltage, that is, the lamp applied voltage Vst does not oscillate, and the voltage maintained at a constant voltage value is applied to the discharge lamp 1. So period B
3, the discharge current Idt (C1, C2...) Does not occur.

As described above, according to the invention of this embodiment,
In the period B2, the discharge current Idt (C1, C2,...)
Is eliminated, so that there is no problem in adjusting the gate-on timing of the gate signal Gt and the generation timing of the discharge current Idt (C1, C2...). Further, since the gate signal Gt can be turned on at any time within the fixed voltage period A2, the gate on time can be easily set. Further, even if the resonance frequency changes due to the lamp temperature or the temperature rise of the transformer core after lighting, the discharge current Idt
(C1, C2...) Do not flow, so the discharge current Idt
The problem that the average light emission changes depending on the presence or absence of (C1, C2...) Is eliminated. Also, due to fluctuations in the frequency of the gate signal Gt, the secondary inductance of the transformer and the capacitance of the lamp may vary due to manufacturing variations and the stray capacitance due to routing between the cables connecting the lamp and the lighting device. Even if the resonance frequency changes due to the change, the resonance frequency is substantially affected only in the oscillating voltage period A1, and the resonance disappears in the other constant voltage periods A2 and A4. Almost gone.

In FIGS. 4, 5 and 6, for example, the main peak widths of the lamp applied voltage Vst are all substantially the same, but this is only for convenience of explanation. For example, when the waveform shown in FIG. 5 is improved as shown in FIG. 6 without changing the brightness of the lamp, usually, the inductance on the secondary side of the transformer is increased. The peak width tends to widen.

FIG. 7 is a diagram showing voltage and current waveforms at various parts of the external electrode type discharge lamp device when the external electrode type discharge lamp device is driven by the driving method according to the second embodiment of the present invention.

In the driving method according to the first embodiment, FIG.
As shown in FIG. 7, the gate signal Gt is turned on during a fixed voltage period A2.
As shown in (a), the point at which the gate signal Gt is turned on is performed during the ON signal period of the FET 13 during a constant voltage period A3 in which a current flows in a direction opposite to the direction in which the FET 13 conducts by the ON signal. Is different.

The constant voltage period A3 of the present embodiment is narrower than the period of the constant voltage period A2, and the margin for the shift of the gate-on start timing of the gate signal Gt is reduced, but the gate is turned on in the constant voltage period A3. As a result, as shown in a period B3 of FIG. 7D, the discharge current Idt (C3, C4...) Is not generated in the period, so that the gate-on timing of the gate signal Gt and the discharge current Id
The problem of adjustment with the generation time of t (C3, C4...) is eliminated. Further, the gate signal Gt can be turned on at any point in the fixed voltage period A3,
It is easy to set the gate-on timing. Also, even if the resonance frequency changes due to the lamp temperature or the temperature rise of the transformer core after lighting, the discharge current Idt (C3, C4.
.) Does not flow, so the discharge current Idt (C3, C4.
There is no problem that the average light emission changes depending on the presence or absence of ()).
In addition, even if the resonance frequency changes due to variations in manufacturing and the change in stray capacitance due to variations in manufacturing and the routing between cables connecting the lamp and the lighting device, the secondary inductance of the transformer and the capacitance of the lamp may vary. The resonance frequency is affected by the oscillating voltage periods A1 and A5, and there is no resonance in the other fixed voltage periods A3 and A4.

Further, in the present embodiment, the amount of light emission can be increased as compared with the first embodiment because the discharge current Idt (C1, C2) can flow.

In any of the first and second embodiments of the present invention, for example, when the voltage of the DC power supply 9 decreases, the period during which the gate signal Gt is at the high level is increased to increase the brightness of the lamp. Can be controlled so as to compensate for the decrease. At this time, even if the voltage of the DC power supply 9 or the period during which the gate signal Gt is at a high level slightly changes, the time from when the gate signal Gt goes to a low level,
Since the start timings of the constant voltage periods A2 and A3 hardly change, the period during which the gate signal Gt is at a low level (this period is substantially equal to the off period of the switch element 13) can be fixed. An electrode-type discharge lamp device can be realized with a simple circuit configuration.

Here, as a circuit configuration for adjusting the period during which the gate signal Gt is at a high level, for example, a change in the voltage of the DC power supply 9 is detected and the gate signal Gt is detected.
A configuration in which the period during which t is at a high level may be adjusted, and the error of the peak value of the source-drain voltage of the switch element 13, the peak value of the drain current, and the average value from the target value is reduced It may be configured to be automatically adjusted in a feedback manner.

Also, in FIGS. 4 to 7, the lamp voltage Vs is illustrated as having a negative polarity, but the polarity is not essentially different. Good retention.

Conventionally, the technique of gradually reducing the current flowing through the switch element by partially utilizing the resonance phenomenon and automatically activating the switch element when the current becomes zero is known as zero current switching. It is used when constructing a switching power supply, etc., but in this case, it is used for the purpose of reducing the loss of the switch element and reducing the occurrence of noise, As in the case of the external electrode type discharge lamp device of the present invention, it is possible to prevent a change in the brightness of the lamp caused by a rise in the temperature of the lamp or the transformer, a variation in the production thereof, a change in the resonance frequency caused by cable routing, and the like. There is nothing intended for it.

[0053]

According to the first aspect of the present invention, the ON signal period of the switch element is started from a constant voltage period in which a current flows in a direction opposite to the direction in which the switch element conducts by the ON signal. Even if the switching frequency of the switching element fluctuates, conduction of the switching element can always be started from the beginning of the oscillating voltage period, and the light emission amount of the discharge lamp can be stabilized.

Further, the on-signal period of the switch element is started from a constant voltage period in which a current flows in a direction opposite to the direction in which the switch element is turned on by the on-signal. Setting becomes easy.

Further, since the ON signal period of the switch element is started from a constant voltage period in which a current flows in a direction opposite to the direction in which the switch element conducts by the ON signal, the lamp temperature after lighting and the transformer Even if there is a change in the discharge current generation timing due to a change in resonance frequency due to a rise in core temperature, variation in transformer or lamp manufacturing, or a change in stray capacitance due to cable routing between the lamp and the lighting device, the light emission of the discharge lamp The change in the amount can be prevented, and the timing of starting the ON signal of the switch element and the timing of generating the discharge current can be easily adjusted.

According to the second aspect of the present invention, in addition to the above effects, the period of the constant voltage mode which appears first after the switch element is turned off is long, so that the start timing of the ON signal of the switch element can be set more easily. Become.

Further, since there is no discharge other than the main discharge causing the discharge lamp to emit light, the discharge is less affected by changes in the resonance frequency and the like, and the amount of light emitted from the discharge lamp can be further stabilized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an external electrode type discharge lamp device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a discharge lamp in the case where a straight tube external electrode type discharge lamp is used as the discharge lamp 1 shown in FIG.

FIG. 3 is an equivalent circuit of the discharge lamp 1 shown in FIG.

FIG. 4 is a diagram showing voltage and current waveforms at various parts in an external electrode type discharge lamp device compared with the present invention.

FIG. 5 is a diagram showing voltage and current waveforms at various parts in an external electrode type discharge lamp device compared with the present invention.

FIG. 6 is a diagram showing voltage and current waveforms at various parts in the external electrode type discharge lamp device according to the embodiment.

FIG. 7 is a diagram showing voltage and current waveforms at various parts in an external electrode type discharge lamp device according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a lighting device of an external electrode type discharge lamp according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge lamp 2 Lamp enclosure 3, 4 Electrodes 5, 6 Dielectric 7 Discharge plasma space 8 Lighting device 9 DC power supply 10 Step-up transformer 11 Primary winding 12 Secondary winding 13 Switching element 14 FET 15 Built-in diode 16 Gate drive circuit 21 Aperture part 22 Coated tube 23 Fluorescent substance

Continued on the front page (72) Inventor Koji Oda 1194 Sado Bessho-cho Himeji-shi Hyogo Ushio Electric Co., Ltd. (72) Inventor Takahiro Hiraoka 1194 Sado Bessho-cho Himeji-shi Hyogo Ushio Electric F Terms (reference) 3K072 AA01 AA19 BA03 BC07 GA02 GB04 GC04 HB03

Claims (2)

[Claims] 1. A discharge lamp having at least one of electrodes provided outside a lamp envelope made of a dielectric material, a DC power supply, a switch element, and a primary side of a transformer are connected in series, and said transformer is connected to said discharge lamp. An external electrode type discharge lamp device comprising: a lighting device having an electrode of the discharge lamp connected to a secondary side thereof; wherein the lighting device has an oscillating voltage period during which the discharge lamp emits light and a constant voltage period during which the discharge lamp does not emit light. And applying a voltage consisting of the following to the discharge lamp, and starting an ON signal period of the switch element from a constant voltage period in which a current flows in a direction opposite to a direction in which the switch element is turned on by the ON signal. External electrode type discharge lamp device. 2. The external electrode type discharge lamp device according to claim 1, wherein the on-signal period of the switch element starts from a constant voltage period which first appears after the switch element is turned off.