JP2006059790A - High-pressure discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize a position of arc bright spots and prevent generation of flicker, on a high-pressure discharge lamp, in which mercury is enclosed by 0.20 mg/mm<SP>3</SP>or more. <P>SOLUTION: A power supply device supplies alternating current to the high pressure discharge lamp in which mercury is enclosed by 0.20 mg/mm<SP>3</SP>or more, with a frequency selected from a range of 60 to 1,000 Hz as a stationary lighting frequency, and the high-pressure discharge lamp is lighted while inserting the alternating current of low frequency into the alternating current of the stationary lighting frequency at an interval having a length of half cycle or longer and 5 cycles or shorter, at an interval selected from a range of 0.01 second to 120 seconds, with frequencies selected from a range of 5 to 200 Hz which is lower than the stationary lighting frequency as the low frequency. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a high pressure discharge lamp lighting device. In particular, the present invention relates to an ultra-high pressure discharge lamp in which mercury is enclosed in an amount of 0.2 mg / mm ³ or more and the lighting pressure is 200 atmospheres or more and a lighting device including the power supply device.

In general, there are a projector apparatus using a liquid crystal panel and a DLP system.
There are 1 type and 3 type using the liquid crystal panel, but in either method, the radiated light from the light source is separated into 3 colors (RGB) to correspond to the image information in the liquid crystal panel In this method, light is transmitted and adjusted, and then the three colors transmitted through the panel are combined and projected onto the screen.
On the other hand, in the method using DLP, a spatial modulation element (also called a light modulation device, specifically a DMD element, etc.) is sometimes passed through a rotary filter in which RGB light is divided and formed from light emitted from a light source. Irradiation is performed in a divided manner, and specific light is reflected by this DMD element and irradiated onto the screen. The DMD element is a device in which millions of small mirrors are laid out for each pixel, and light projection is controlled by controlling the direction of each small mirror.
Compared with the liquid crystal system, the DLP system has a merit that the entire system is small and simple because the optical system is simple and there is no need to use three liquid crystal panels.

A high pressure discharge lamp having a high mercury vapor pressure is used as a light source of the projector apparatus. This is because by increasing the mercury vapor pressure, light in the visible wavelength range can be obtained with high output.
Further, it is known that this kind of discharge lamp having a high mercury vapor pressure has a protrusion formed at the tip of the electrode during lighting. For example, Patent Document 1 introduces a technique for eliminating the protrusions by regarding the existence of such protrusions as a problem. Specifically, a technique is disclosed in which a lower frequency (for example, 5 Hz) is present in the steady lighting frequency for 1 second or longer to melt the electrode surface and completely eliminate the protrusion. .

However, even when a high-pressure discharge lamp (ultra-high pressure mercury lamp) is turned on as a light source of the projector apparatus by the above technique, the arc bright spot is not stable, and so-called flicker is generated frequently. In particular, it occurred remarkably in a discharge lamp having an enclosed mercury amount of 0.20 mg / mm ³ or more.
JP 2002-175890 A

The problem to be solved by the present invention is to prevent the occurrence of so-called flicker by stabilizing the arc bright spot in an ultrahigh pressure discharge lamp having a mercury filling amount of 0.20 mg / mm ³ or more.

In order to solve the above-mentioned problems, a high pressure discharge lamp lighting device according to the present invention has a discharge vessel made of quartz glass, and a pair of electrodes having projections formed at the tip thereof are arranged to face each other at intervals of 2.0 mm or less. An ultrahigh pressure discharge lamp in which 0.20 mg / mm ³ or more of mercury and a halogen in the range of 10 ⁻⁶ μmol / mm ³ to 10 ⁻² μmol / mm ³ are enclosed in a discharge vessel, and an alternating current with respect to this discharge lamp It is comprised from the electric power feeder which supplies an electric current.
The power supply device supplies an alternating current with a frequency selected from a range of 60 to 1000 Hz to the ultra high pressure discharge lamp as a steady lighting frequency, and is a frequency lower than the steady lighting frequency and is 5 to 5. A frequency selected from a range of 200 Hz is set as a low frequency.
This low-frequency alternating current is lit while being inserted at intervals selected from 0.01 seconds to 120 seconds, with a length of half cycle or more and 5 cycles or less with respect to the alternating current of the steady lighting frequency. It is characterized by that.

  The power feeding device includes an inverter circuit having at least two switching elements, a coil of 210 μH or less connected in series with the discharge lamp at a subsequent stage of the inverter circuit, and dead time for the switching elements. It is characterized by having a control unit that is alternately turned on and off while being provided.

  In the ultra high pressure discharge lamp, a trigger electrode is disposed on the outer surface of the discharge vessel.

The present invention has the following effects by the above configuration.
First, a protrusion can be formed at the tip of the electrode, and a stable arc discharge can be formed starting from the protrusion. As disclosed in Patent Document 1, it is not a technique for extinguishing a protrusion, but a protrusion is actively made. As a result, an arc is formed with the protrusion as a starting point, so that the lighting of the discharge lamp can be stabilized.
Second, it is possible to prevent the occurrence of extra protrusions other than the protrusion that becomes the arc starting point. This is because when a plurality of protrusions are formed at the tip of the electrode, a so-called arc jump occurs between the protrusions, resulting in an unstable arc. The present invention generates and maintains only the projections to be the arc starting point, and prevents generation and growth of extra projections other than the projections.

FIG. 1 shows a high-pressure discharge lamp which is an object of the present invention.
The discharge lamp 10 has a substantially spherical light emitting portion 11 formed by a discharge vessel made of quartz glass. In the light emitting section 11, a pair of electrodes 20 are arranged to face each other with an interval of 2 mm or less. Further, sealing portions 12 are formed at both ends of the light emitting portion 11. A conductive metal foil 13 made of molybdenum is embedded in the sealing portion 12 in an airtight manner, for example, by a shrink seal. The shaft portion of the electrode 20 is joined to one end of the metal foil 13, and the external lead 14 is joined to the other end of the metal foil 13 to supply power from an external power supply device.
The light emitting unit 11 is filled with mercury, rare gas, and halogen gas. Mercury is used to obtain a required visible light wavelength, for example, radiation having a wavelength of 360 to 780 nm, and is enclosed in an amount of 0.2 mg / mm ³ or more. Although the amount of sealing varies depending on the temperature condition, the vapor pressure becomes extremely high at 200 atm or more at the time of lighting. Also, by enclosing more mercury, it is possible to make a discharge lamp with a high mercury vapor pressure of 250 atm or higher and 300 atm or higher when the lamp is turned on. The higher the mercury vapor pressure, the more suitable the light source suitable for the projector device. realizable.

As the rare gas, for example, argon gas is sealed at about 13 kPa. Its function is to improve the lighting startability. As for halogen, iodine, bromine, chlorine and the like are enclosed in the form of mercury or other metals and compounds. The amount of halogen encapsulated is selected from the range of 10 ⁻⁶ μmol / mm ³ to 10 ⁻² μmol / mm ³ . The function of the halogen is to extend the life using a so-called halogen cycle. However, an extremely small and extremely high lighting vapor pressure like the discharge lamp of the present invention also has an effect of preventing devitrification of the discharge vessel.
For example, the discharge lamp has a maximum outer diameter of 9.5 mm, a distance between electrodes of 1.5 mm, an arc tube inner volume of 75 mm ³ , a rated voltage of 70 V, and a rated power of 200 W, and is turned on by alternating current.
In addition, this type of discharge lamp is built in a projector apparatus that is miniaturized, and requires a large amount of light emission while requiring an extremely small overall size. For this reason, the thermal influence in the light emitting part is extremely severe. The lamp wall load value of the lamp is 0.8 to 2.0 W / mm ² , specifically 1.5 W / mm ² .
When such a high mercury vapor pressure or tube wall load value is mounted on a presentation device such as a projector device or an overhead projector, emitted light with good color rendering can be provided.

A protrusion is formed at the tip of the electrode 20 (the end facing the other electrode) as the lamp is turned on. The phenomenon in which such protrusions are formed is not necessarily clear, but can be estimated as follows.
That is, tungsten (electrode constituent material) evaporated from the high temperature portion near the electrode tip during lamp operation is combined with halogen and residual oxygen present in the arc tube. For example, if the halogen is Br, WBr, WBr ₂ , WO, It exists as tungsten compounds such as WO ₂ , WO ₂ Br, and WO ₂ Br ₂ . These compounds are decomposed into tungsten atoms or cations at a high temperature portion in the gas phase near the electrode tip. Temperature diffusion (high temperature part in the gas phase = from the inside of the arc to low temperature part = diffusion of tungsten atoms toward the tip of the electrode) and when tungsten atoms are ionized into cations in the arc to operate as a cathode It is considered that the tungsten vapor density in the gas phase in the vicinity of the electrode tip is increased by being drawn toward the cathode by the electric field (= drift), and is deposited on the electrode tip to form a protrusion.

FIG. 2 schematically shows the tip of the electrode 20 shown in FIG. 1 for the purpose of showing the tip and protrusion of the electrode. The electrodes 20 are each composed of a sphere portion 20a and a shaft portion 20b, and a protrusion 21 is formed at the tip of the sphere portion 20a. Even if the projection 21 does not exist at the start of lamp lighting, the projection 21 is naturally formed by the subsequent lighting.
This protrusion does not occur in any discharge lamp. The distance between the electrodes is 2 mm or less, and the light emitting part is filled with 0.15 mg / mm ³ or more of mercury, rare gas, and halogen in the range of 1 × 10 ⁻⁶ to 1 × 10 ⁻² μmol / mm ³ . In short arc type discharge lamps, it is known that protrusions are formed as the lamp is lit.
As for the size of the protrusion, as a numerical example, the maximum electrode diameter (direction perpendicular to the discharge direction) is φ1.0 to 1.5 mm, and the distance between the electrodes is 1.0 to 1.5 mm. In some cases, the diameter is about 0.2 to 0.6 mm.

This protrusion is indispensable when used as a light source of a projector apparatus having a distance between electrodes of 2 mm or less and containing 0.2 mg / mm ³ or more of mercury in the arc tube as in the discharge lamp according to the present invention.
This is because, in a discharge lamp that contains 0.2 mg / mm ³ or more of mercury in the arc tube and the operating pressure reaches 200 atmospheres or more, the arc discharge is reduced by a high vapor pressure, and as a result, the discharge start point is also reduced. Because it is.
For this reason, as disclosed in Patent Document 1, in the spherical electrode with the protrusions disappeared, the discharge starting point moves little by little, leading to a problem of flicker (flicker) on the image screen of the projector device. . In particular, an arc bright spot formed at a short distance between electrodes of 2 mm or less can be a fatal flicker for a video screen even if it is a slight movement of 0.5 mm or less.

In this respect, the discharge lamp disclosed in Patent Document 1 has a level of enclosed mercury of 0.18 mg / mm ³ and is not 0.20 mg / mm ³ or more as in the present invention. It is considered that the action of squeezing is low, that is, if the tip has a spherical electrode, the flicker problem can be solved.

  Further, in the discharge lamp to which the present invention is directed, a projection is formed at the tip of the electrode, and arc discharge is generated starting from the projection, so that the light from the arc is not easily blocked by the spherical portion 20a of the electrode. In addition, the light utilization efficiency is improved and a brighter image can be obtained. Although FIG. 2 is a schematic drawing, normally, the tip of the shaft portion 20b has an element corresponding to a spherical portion having a diameter larger than the shaft diameter. This point is referred to FIG. 7 described later.

FIG. 3 shows a power feeding device for lighting the discharge lamp.
The lighting device includes a discharge lamp 10 and a power feeding device. The power feeding device includes a step-down chopper circuit 1 to which a DC voltage is supplied, and a full-bridge inverter circuit 2 (hereinafter referred to as “the following”) that is connected to the output side of the step-down chopper circuit 1 and changes the DC voltage to an AC voltage. And a starter circuit 3 including a coil L1, a capacitor C1, and a starter circuit 3 connected in series to the discharge lamp.
The step-down chopper circuit 1, the full bridge circuit 2, and the starter circuit 3 constitute a power feeding device, and the discharge lamp 10 and the lighting device are referred to as a lighting device.

The step-down chopper circuit 1 is connected to a DC power source _VDC , and includes a switching element Qx, a diode Dx, a coil Lx, a smoothing capacitor Cx, and a drive circuit Gx for the switching element Qx. The switching element Qx is turned on / off by the drive circuit Gx. By this driving, the duty ratio of the switching element Qx is adjusted, and the current or power supplied to the discharge lamp 10 is controlled.
The full bridge circuit 2 includes transistors and FET switching elements Q1 to Q4 connected in a bridge shape, and driving circuits G1 to G4 for the switching elements Q1 to Q4. Note that a diode may be connected in parallel to each of the switching elements Q1 to Q4, but the diode is omitted in this embodiment.
The switching elements Q1 to Q4 are driven by driving circuits G1 to G4 via a control unit (not shown).

In the operation of the full bridge circuit 2, the switching elements Q1, Q4 and the switching elements Q2, Q3 are alternately turned on and off repeatedly. When the switching elements Q1 and Q4 are turned on, a current flows through the step-down chopper circuit 1 → the switching element Q1 → the coil L1 → the discharge lamp 10 → the switching element Q4 → the step-down chopper circuit 1. On the other hand, when the switching elements Q2 and Q3 are turned on, an AC rectangular wave current is supplied to the discharge lamp 10 through the path of the step-down chopper circuit 1, the switching element Q3, the discharge lamp 10, the coil L1, the switching element Q2, and the step-down chopper circuit 1. To do.
When driving the switching elements Q1 to Q4, in order to prevent the switching elements Q1 to Q4 from being simultaneously turned on, a period (dead time Td) in which all the switching elements Q1 to Q4 are turned off is provided when the polarity of the AC rectangular wave is switched. It is done.

  The frequency of the AC rectangular wave output supplied to the discharge lamp 10 is selected from the range of 60 to 1000 Hz (steady frequency), for example, 200 Hz. The dead time period is selected from the range of 0.5 μs to 10 μs.

  Here, the high-pressure discharge lamp lighting device of the present invention uses the power supply device shown in FIG. 3 to light the discharge lamp shown in FIG. 1 at a steady frequency (60 to 1000 Hz), and a frequency lower than the steady frequency is a half cycle. It is characterized by being inserted at intervals of 0.1 seconds to 120 seconds with a length of ˜5 cycles.

FIG. 4 shows the current waveform of the discharge lamp 10, the vertical axis represents the current value, and the horizontal axis represents time.
As illustrated, the current waveform of the discharge lamp is intermittently driven at a low frequency, for example, 10 Hz, lower than the steady frequency while being driven at a steady frequency, for example, 200 Hz.
This low frequency is a frequency lower than the stationary frequency and is selected from the range of 5 to 200 Hz, preferably 5 to 50 Hz. The low frequency is periodically generated at intervals of 0.01 seconds to 120 seconds, preferably 0.1 seconds to 120 seconds, or 1 second to 120 seconds. The interval at which the low frequency is inserted is a period indicated as a low frequency insertion period in the figure, and is defined as a time interval from the timing at which one low frequency waveform starts to the timing at which the next low frequency waveform starts. . Further, the length of insertion of the low-frequency lighting is not limited to one cycle as shown in the figure, and is selected from a period of not less than a half cycle and not more than 5 cycles as will be described later.

The frequency of the low frequency (5-200 Hz), the length of insertion (half cycle to 5 cycles), and the interval of insertion (0.01 seconds to 120 seconds) depend on the design of the discharge lamp, particularly the electrode thermal. Selected in relation to specific design.
As an example, when the rated power of the discharge lamp is 120 W, the stationary frequency is 90 Hz, the low frequency frequency is 5 Hz, the insertion length is one cycle, and the insertion interval is 15 seconds (Lighting Example 1). Further, when the rated power of the discharge lamp is 150 W, the stationary frequency is 125 Hz, the low frequency frequency is 5 Hz, the insertion length is one period, and the insertion interval is 15 seconds (lighting example 2). Further, when the rated power of the discharge lamp is 200 W, the stationary frequency is 200 Hz, the low frequency frequency is 7.5 Hz, the insertion length is one period, and the insertion interval is 10 seconds (Lighting Example 3). Further, when the rated power of the discharge lamp is 250 W, the stationary frequency is 400 Hz, the low frequency frequency is 15 Hz, the insertion length is one period, and the insertion interval is 0.1 second (Lighting Example 4). When the rated power of the discharge lamp is 135 W, the stationary frequency is 360 Hz, the low frequency frequency is 45 Hz, the length of insertion is 0.5 cycles, and the insertion interval is 0.02 seconds (Lighting Example 5). When the rated power of the discharge lamp is 135 W, the stationary frequency is 540 Hz, the low frequency frequency is 180 Hz, the length to be inserted is one period, and the insertion interval is 0.02 seconds (Lighting Example 6).

Here, the technical effect of periodically inserting the low frequency lighting into the steady frequency lighting will be described. It has already been explained that the discharge lamp targeted by the present invention is advantageous in that it is possible to stabilize the arc when the protrusion is formed at the electrode tip.
However, if only the control for generating the protrusions is used, extra protrusions may be derived in addition to the protrusions that should be originally required. In the present invention, the control of periodically inserting the low frequency lighting into the steady frequency lighting is nothing but preventing the generation of such extra protrusions.

FIG. 5 is a comparative diagram for explaining the present invention, and schematically shows an undesirable state that occurs when the frequency control of the present invention is not performed.
When the lamp is turned on, a protrusion 21 (first protrusion) is formed at the center of the tip of the ball portion 20a of the electrode. The protrusion 21 is a protrusion that is a starting point of discharge and is necessary for stabilizing the arc. If the control of the present invention is not performed, another protrusion 22 (second protrusion) is generated around the protrusion 21 as the lamp is continuously turned on. The protrusions 22 are originally unnecessary protrusions, and the discharge start point moves between the protrusions 21 and causes a so-called flicker problem. The number of the second protrusions is not limited to one, and many second protrusions may occur.

Here, the phenomenon in which unnecessary protrusions 22 (second protrusions) are generated and grown can be explained as follows.
That is, there is a temperature distribution on the electrode surface during operation of the discharge lamp, the temperature at the tip is highest, and the temperature is lower at the rear.
In the high temperature region near the electrode tip, the electrode surface is eroded by evaporation of tungsten and evaporation of tungsten oxide such as WO and WO2 generated by reaction with oxygen remaining in the discharge vessel. However, as described above, at the electrode tip, which is the starting point of discharge, because of the high tungsten vapor density in the arc, rather, tungsten is deposited and deposited, and the first protrusion is formed.
On the other hand, in the low temperature region of the electrode surface, the electrode surface is also eroded by evaporation of WBr, WBr2, WO2Br, WO2Br2, etc. generated by the reaction with bromine sealed in the discharge vessel and the remaining oxygen.
That is, the type of tungsten compound that evaporates differs depending on the temperature of the electrode surface, but both the high temperature region and the low temperature region of the electrode surface are eroded.
Next, in the temperature range between the high temperature region and the low temperature region on the electrode surface, the formation of the tungsten compound as described above is small due to the thermochemical properties of tungsten, and therefore the electrode surface is less eroded. Rather, since the deposition and deposition of tungsten vapor existing in the discharge vessel is more dominant, the second protrusion is generated and grown.

As described above, the present invention is indispensable for the first protrusion, and thus must be maintained without disappearing, but the second protrusion is not necessary and must be eliminated.
It can be said that the frequency control of the present invention acts to eliminate the second protrusion. This mechanism will be described below.

When the discharge lamp is steadily lit at a frequency of 60 Hz to 1000 Hz, the formation of the second protrusion starts in the intermediate temperature region on the electrode surface as described above. At that time, when the frequency is switched to a frequency lower than the steady lighting frequency, the temperature of the electrode tip rises due to the long anode operation period during the period of operation as the anode. This temperature increase is conducted to an intermediate temperature region where the second protrusion is generated, and the electrode surface temperature in that region is increased. Therefore, the second protrusion which has started to be formed is evaporated, eroded and disappears. is there.
Here, in order to suppress the generation and growth of the second protrusion, it is essentially important to change the temperature of the electrode surface with time. For example, even if the temperature of the electrode surface is set to be high overall by reducing the size of the electrode, the position where the second protrusion is generated and grown is only shifted to the rear of the electrode, and the generated growth is suppressed. It is not possible. That is, the present invention is based on the idea of suppressing the formation of the second protrusion by preventing the second protrusion from being generated at a certain position by changing the temperature of the electrode surface at an appropriate time interval.

By the way, when the low frequency to be inserted is less than 5 Hz, the insertion interval is less than 0.01 seconds, or the low frequency is inserted over 5 cycles, the temperature rise at the electrode tip becomes too large. Not only the second protrusion but also the first protrusion which is indispensable for the ultrahigh pressure discharge lamp according to the present invention is lost.
Conversely, if the low frequency to be inserted exceeds 200 Hz or a low frequency less than a half cycle is inserted, a sufficient temperature rise in the intermediate temperature region where the second protrusion is generated cannot be obtained. The growth of the second protrusion cannot be suppressed. Also, when the insertion interval exceeds 120 seconds, the second protrusion grows until it cannot be eroded by low frequency insertion during steady lighting.
In addition, if the insertion interval is 0.1 second or more, the temperature rise of the electrode can be completely suppressed, and if the insertion frequency is 50 Hz or less, the growth of the second protrusion is prevented. It can be suppressed perfectly.

  The specific means for inserting the low-frequency lighting can be achieved by adjusting the switching period of the switching elements Q1 to Q4 of the full bridge circuit 2 in the circuit configuration shown in FIG.

FIG. 6 shows a current waveform flowing in the discharge lamp, and shows another current waveform different from the current waveform shown in FIG.
(A) shows a case where a low-frequency current waveform is inserted in a half cycle. In this case, since one electrode continues to operate as an anode in the low-frequency insertion period, the low-frequency insertion period is interpreted by defining the illustrated period Ta as a half-cycle length. In addition, when inserting such low frequency lighting of a half cycle, it is preferable to insert with the polarity different from previous insertion.
(B) shows a case where the low-frequency current waveform is larger than a half cycle and smaller than one cycle. In this case, a period in which the current polarity is fixed can be defined as a half cycle. That is, in the figure, the period Tb is defined as the length of a half cycle, and in the figure, it can be interpreted that a low frequency current is inserted for a period of 3/4 period. The reason for defining the period in which the polarity is fixed as a half cycle is that the second protrusion disappears due to the temperature rise of the electrode surface during the period. In addition, when inserting such low frequency lighting larger than a half period and smaller than one period, it is desirable to insert so that the polarity of the longer period may change alternately. This is because both electrodes can be heated uniformly.
(C) has shown the form from which a frequency differs (changes) in the case of insertion of low frequency lighting. In this case, the insertion cycle (how many cycles have been inserted) is defined by the lowest frequency. In the figure, it can be interpreted that the period Tc is defined as a half cycle, and one cycle of the low frequency is inserted. The reason why the low frequency waveform is defined as the low frequency is that the fixed period of the polarity is the longest during the insertion period of the frequency, and the temperature rise effect at the electrode tip can be exhibited.
The above definition prevents the low-frequency insertion state (form) from being obscured as a current waveform, and can be said to be defined to clarify the low-frequency insertion period and insertion cycle.

Here, it can be said that the discharge lamp which is the object of the present invention is characterized in that the amount of enclosed mercury is 0.2 mg / mm ³ or more. According to the experiments by the present inventors, when the amount of enclosed mercury is smaller than 0.2 mg / mm ³ , specifically, 0.18 mg / mm ³ , the influence of the mercury vapor pressure during lighting on the arc is Make sure it is small. That is, when the amount of enclosed mercury is about 0.18 mg / mm ³ , the arc does not fluctuate even when the surface of the electrode tip is smooth (no protrusions or the like). However, when the amount of enclosed mercury is 0.2 mg / mm ³ or more, the effect of constricting the arc due to the vapor pressure during lamp operation is markedly increased, thereby causing a phenomenon that the arc moves (flacks).
The present invention has invented that, in a discharge lamp having an enclosed mercury amount of 0.2 mg / mm ³ or more, it is indispensable to form a protrusion at the tip of the electrode in order to stabilize the arc. And it can be said that it is a big feature that lighting of a predetermined low frequency is inserted in order to prevent unnecessary protrusions from occurring and growing on the premise that there is a protrusion at the electrode tip.

Returning to the circuit of the power supply apparatus of FIG. 3, the high-pressure discharge lamp lighting apparatus of the present invention is a subsequent stage of the full-bridge inverter circuit 2, and the inductance of the coil L1 connected in series with the discharge lamp is 210 μH or less. Is preferred.
The reason is that the drop in the light output of the discharge lamp can be reduced during the dead times of the switching elements Q1 to Q4 of the full bridge circuit 2.
This effect is meaningful in that it is possible to suppress fluctuations in the amount of light with the passage of time regardless of which of the method using the liquid crystal panel and the method using the DLP. In particular, in the case of the DLP method, the polarity of the discharge lamp can be changed without synchronizing with the driving of the DMD element or the rotary filter. Therefore, the effect is great in that the insertion of the low-frequency lighting in the lighting at the steady frequency according to the present invention can be performed freely from the viewpoint of controlling the protrusion.

The starter circuit 3 includes a resistor R1, a switch element Q5, a capacitor C2, a high voltage transformer T2, and a drive circuit G5 for the switch element Q5. Since the high voltage side input terminal and the low voltage side input terminal of the starter circuit 3 are connected in parallel with the discharge lamp 10, the same voltage as the voltage applied to the discharge lamp 10 is also supplied to the starter circuit 3. In response to this applied voltage, the starter circuit 3 charges the capacitor C2 via the resistor R1.
The switch element Q5 is composed of an SCR thyristor or the like. When the switch element Q5 is turned on by the drive circuit G5, the charging voltage of the capacitor C2 is generated in the primary winding of the high voltage transformer T2, and a dielectric breakdown trigger voltage is generated in the secondary winding.

Here, in the high pressure discharge lamp lighting device of the present invention, it is desirable to arrange the trigger electrode on the outer surface of the discharge vessel. This means that a high voltage at the start of lighting is not generated between the electrodes of the discharge lamp. (Hereinafter also referred to as “external trigger method”). In the circuit diagram of FIG. 3, one end of the secondary winding of the high voltage transformer T2 is disposed on the outer surface of the discharge lamp 10 as a trigger electrode Et. The other end of the secondary winding is electrically connected to one electrode of the discharge lamp 10.
This circuit configuration is the sum of inductances in the current loop formed during normal lighting, in that the high-voltage generating transformer T2 that is required only at the time of starting lighting does not exist in the current supply path during steady lighting after starting lighting. This is advantageous because the coil L1 can be made small.

With this circuit configuration, when a trigger voltage is generated at the start of lighting of the discharge lamp 10, quartz glass (a constituent material of the discharge vessel) is interposed between the trigger electrode Et and the electrode in the discharge vessel. Dielectric barrier discharge is generated. When plasma is generated in the discharge vessel due to the dielectric barrier discharge, discharge is generated by the no-load open voltage applied in advance between the first electrode and the second electrode in the discharge vessel using the plasma as a seed. To do.
The trigger voltage is 5 kv to 20 kv, for example, 13 kv. The no-load open transmission voltage is 250 to 400 v, for example, 350 v.

  Here, strictly speaking, the inductance is not only the coil L1 but also the total sum of inductances in a current loop formed during steady lighting of the discharge lamp 10. However, since it is typically determined by the inductance of the coil L1, in the present invention, the numerical value is defined by paying attention to the inductance of the coil L1. Therefore, the numerical value specification of the inductance is more preferably the total sum of inductances in the current loop during steady lighting, that is, the capacitor Cx, the full bridge circuit 2, the coil L1, the discharge lamp 10, the full bridge circuit 2, and the capacitor Cx. From the viewpoint of practical effects, the coil L1 is numerically defined.

  Note that the coil L1 and the capacitor C1 are necessary for preventing noise when the lamp is steadily lit, and specifically, it is desirable that the coil L1 and the capacitor C1 be 0.15 μH or more.

  In FIG. 3, the full bridge circuit 2 has been described using a circuit composed of four switching elements. However, the present invention is not limited to this configuration, and other circuit configurations may be employed. In particular, even if the number of switching elements is not four, it is sufficient if at least two switching elements can be alternately turned on and off with a dead time interposed.

Further, the step-down chopper circuit is not an essential component, and other circuit methods can be employed as the current amount adjusting means.
Furthermore, the capacitor Cx existing in the step-down chopper circuit can adopt a configuration in which the capacitance changes at the start of lighting and at the time of steady lighting. In this configuration, for example, a plurality of capacitors may be connected in parallel, and the circuit configuration may be switched by a switch element.

FIG. 7 shows the relationship between the lighting control by the high-pressure discharge lamp lighting device of the present invention and the electrodes, (a) is an enlarged view of the electrodes, and (b) shows specific numerical values.
The electrode dimensions shown in (b) represent dimension examples according to lighting examples 1 to 3 introduced in paragraph 0023. The dimensions of the light emitting part are such that the maximum outer diameter in the direction perpendicular to the discharge direction of the light emitting part 11 shown in FIG. 1 is the outer diameter value, and the maximum inner diameter is the inner diameter value.
Such numerical examples are merely examples and do not constrain the technical scope of the present invention.

1 shows a high-pressure discharge lamp according to the present invention. 1 shows an electrode of a high-pressure discharge lamp according to the present invention. 1 shows a power supply device of a high pressure discharge lamp lighting device according to the present invention. 2 shows a current waveform of a discharge lamp according to the present invention. The enlarged view of the electrode for demonstrating this invention is shown. The other form of the current waveform of the discharge lamp which concerns on this invention is shown. The example of the electrode dimension of the discharge lamp which concerns on this invention is shown.

Explanation of symbols

1 Step-down chopper circuit 2 Full bridge circuit 3 Starter circuit 10 Discharge lamp 20 Electrode 21 Projection

Claims (3)

In a discharge vessel made of quartz glass, a pair of electrodes with projections formed at the tips are arranged to face each other at intervals of 2.0 mm or less, and 0.20 mg / mm ³ or more of mercury and 10 ⁻⁶ are placed in this discharge vessel. In a high-pressure discharge lamp lighting device composed of a high-pressure discharge lamp in which halogen in the range of μmol / mm ³ to 10 ⁻² μmol / mm ³ is enclosed, and a power supply device that supplies an alternating current to the discharge lamp,
The power supply device, for the high-pressure discharge lamp,
While supplying an alternating current with a frequency selected from the range of 60 to 1000 Hz as a steady lighting frequency,
A frequency lower than the steady lighting frequency and a frequency selected from a range of 5 to 200 Hz as a low frequency,
While inserting this low-frequency alternating current with a length of half cycle or more and 5 cycles or less with respect to the alternating current of the steady lighting frequency, at an interval selected from the range of 0.01 seconds to 120 seconds. A high pressure discharge lamp lighting device characterized by being lit.   The power feeding device includes an inverter circuit having at least two switching elements, a coil of 210 μH or less connected in series with the discharge lamp at a subsequent stage of the inverter circuit, and a dead time for the switching elements. The high pressure discharge lamp lighting device according to claim 1, further comprising a controller that alternately drives on and off. The high pressure discharge lamp lighting device according to claim 1 or 2, wherein the ultra high pressure discharge lamp has a trigger electrode disposed on an outer surface of the discharge vessel.

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