JP2003243194A - Driving method of high pressure mercury lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving method for lessening loss of electrode loss, extending life and stabilizing I and light output as a light source for an image projector. <P>SOLUTION: Drive power of a high pressure lamp is selected in such a manner that when a power wave form is frequency-resolved, a frequency of a component not lower than 5% of the whole powder is at least 2 kHz and not higher than the lowest acoustical resonance frequency of the lamp. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a high-pressure mercury lamp, which is mainly used for image projectors, and which has a pair of tungsten electrodes in a discharge vessel made of quartz glass and in which mercury and a rare gas are sealed. It is a thing.

[0002]

2. Description of the Related Art A high pressure mercury lamp, which is preferably used as a light source for a video projector device, has a pair of electrodes facing each other inside a discharge vessel made of quartz glass, and has a mercury and a rare gas. Gas and halogen are enclosed. The high-pressure mercury lamp is required to have high illuminance of the screen in the above-mentioned video projector device application, and in order to achieve high brightness of the lamp, the amount of mercury tends to increase more and more for the purpose of ensuring pressure during operation. Yes, 0.16 mg / mm ³ or more has been encapsulated recently. On the other hand, the high-pressure mercury lamp requires high input power to completely evaporate the enclosed mercury, and the tube wall load of the lamp is 0.8 W / mm ² or more. By satisfying these conditions, it is possible to provide an unprecedented, extremely high-luminance lamp, and the lamp can be suitably used as the light source of the above-mentioned device. Most of the high-pressure mercury lamps described above are driven by supplying an alternating current of about several tens to several hundreds of Hz. Furthermore, by using a rectangular-wave current whose period of zero is sufficiently short and whose current waveform rises sufficiently fast, it is possible to prevent the re-ignition voltage from rising when driving with a sine-wave current, for example. Wear can be suppressed, and therefore
It is possible to extend the life of the lamp.

[0003]

However, when driving the lamp with an alternating current, the thermal design of the electrodes is extremely difficult. In other words, when the lamp is lit by alternating current, the electrode operates as an anode in the half cycle and operates as a cathode in the other half cycle, so that the electrode temperature rises when electrons flow in and the electrode temperature when the polarity is reversed. It must be balanced against degradation and it is very difficult to design to operate at optimum temperature. For example, when the electrode design is suitable for the anode half cycle where the temperature easily rises, in the cathode half cycle, the temperature does not become high enough to give sufficient thermionic emission, which causes an unstable phenomenon of the cathode bright spot. On the contrary, if the electrode design is suitable for the cathode half cycle,
In the anode half cycle, the temperature becomes too high, which causes melting, deformation and evaporation of the electrode, which causes various problems such as blackening of the discharge vessel and reduction of illuminance. .

In view of such a problem, if the driving current is driven at a high frequency, the difference in electrode temperature between the anode half cycle and the cathode half cycle becomes small, and an electrode suitable for both half cycles is obtained. It enables the thermal design of.

However, when the frequency of the lamp drive current is increased, the drive power waveform often coincides with the acoustic resonance frequency of the lamp.

Acoustic resonance is caused by high-frequency lighting of a lamp.
When the frequency peculiar to the lamp, which is determined by the enclosure in the arc tube and the shape of the arc tube, and the frequency of the periodic change in the power input to the lamp become almost equal, a standing wave of compressional wave is generated in the arc tube. It is a phenomenon that occurs because it occurs, generally,
This may cause the arc to become unstable, disappear, or the arc tube to burst. When an arc instability occurs in the lamp due to acoustic resonance, the image projected by the video projector has unstable brightness and flickers, so such a lamp cannot be used for the purpose of the video projector device. .

Therefore, according to the present invention, even when driven by an alternating current, arc instability due to acoustic resonance does not occur, and therefore stable discharge can be maintained and the cathode luminescent spot becomes unstable. It can be prevented and the fluctuation of the electrode tip temperature during one cycle of alternating current can be made sufficiently small,
It is an object of the present invention to provide a method of driving a mercury lamp for use in an image projector, which can suppress the wear of the electrode and facilitate the thermal design of the electrode.

[0008]

In order to solve the above-mentioned problems, the lamp driving method according to the present invention supplies the frequency component of the power waveform supplied to the mercury lamp when the power waveform is decomposed. It is characterized in that all the frequency components that are 5% or more of the total power are 2 kHz or more and are the lowest acoustic resonance frequency or less in the lamp. In other words, when the power waveform of the power supplied to the mercury lamp is frequency-resolved, all the frequency components that account for 5% or more of the total power supplied are 2 kHz or higher. The fluctuation of the electrode tip temperature during one cycle of the electric current is small, so that the wear of the electrode can be suppressed and the arc is unstable due to the acoustic resonance because it is lower than the lowest acoustic resonance frequency in the lamp. Nothing.

Further, in the lamp driving method of the present invention, when a sine wave voltage is applied to light the lamp, the current frequency is 1 kHz or higher and 1/1 of the lowest acoustic resonance frequency in the high pressure mercury lamp. It is characterized by being in the range of 2 or less.

The lowest acoustic resonance frequency is 197.2 × L ^−0.83 [kHz] when the axial length of the discharge space of the high pressure mercury lamp is L (mm). Characterize.

First, the inventors of the present invention measured the fluctuation range of the electrode tip temperature during one cycle when the high-pressure mercury lamp was driven by an alternating rectangular wave current, while changing the frequency. FIG. 2 is a schematic explanatory view of the high pressure mercury lamp used in the experiment, and is a cross-sectional view taken along the tube axis of the lamp. The discharge space inside the discharge vessel 2 has a rotationally symmetric shape obtained by rotating a substantially elliptical shape with its major axis as an axis. Note that, as shown in FIG. 2, the major axis of the discharge space, that is, the major axis of the substantially elliptical shape is L [mm]. The discharge vessel 2 is made of quartz glass, and an argon gas, a halide, and a pair of electrodes are arranged so as to face each other.
Enclose 2 mg / mm ³ of mercury and load on the tube wall 1.0 W / m
It was driven by m ² . When the high pressure mercury lamp was driven with a rectangular wave current having a frequency of 100 Hz, the fluctuation range of the electrode tip temperature during one cycle reached several hundred K (Kelvin). Next, when the frequency of the drive current was set to 1 kHz without changing the current waveform, it was confirmed that the fluctuation range of the electrode tip temperature decreased to several tens K (Kelvin). Further, it was found that when the frequency of the driving current was set to 20 kHz and driving was performed, the fluctuation range decreased to several K (Kelvin). From the above experiment, when the frequency of the drive current is set to 1 kHz or more, even if there is temperature fluctuation in one cycle, it fluctuates on the order of only a few tens of K (Kelvin), which is suitable for both the anode and the cathode. I found that thermal design is possible. As a result, the drive current frequency is 1 kHz.
It is preferably z or more, and particularly preferably about several tens kHz or more.

Incidentally, the acoustic resonance is a phenomenon in which the pressure fluctuation caused by the fluctuation of the gas temperature accompanying the fluctuation of the electric power resonates with the acoustic resonance frequency peculiar to the lamp. is important. From this viewpoint, as a result of further detailed investigation by the inventors, when the power waveform is decomposed into frequency components included in the power waveform, the power of the arbitrary frequency component exceeds 5% with respect to all driving power, and It has been found that an acoustic resonance phenomenon is triggered when the frequency matches the acoustic resonance frequency of the lamp. In other words, if the electric power when the total electric power waveform is decomposed into frequency components is less than 5% of the total electric power, the acoustic resonance phenomenon is generated even if it matches the acoustic resonance frequency of the lamp. Does not occur.

Here, the frequency decomposition of the power waveform will be described. Current waveform is I (t), voltage waveform is V
(T), if their period is T seconds, the power waveform w (t) also becomes a waveform of period T seconds, and w (t) =
It can be written as I (t) × V (t). At this time, when the power waveform is decomposed into Fourier series, the following equation is obtained.

[0014]

[Formula 1]

[0015] Note that the above formula (1), the power waveform of the period T seconds, in general, a _0/2 of the magnitude of the DC component and the natural number n times the angular frequency of the fundamental angular frequency omega = 2 [pi / T It indicates that the sine wave component with is included.

The total power of this power waveform is a ₀ /
2 [W], and the power component of the angular frequency nω is √ (a
Since ^{_n 2} + _{b n} ²⁾ is a [W], component power component is more than 5% of the total power, i.e., √ _{(a ^{a n 2 + b n 2)}} ≧ 0.05 × (a 0/2) Scope If the frequency nω / (2π) of a certain component is regulated within a predetermined frequency range, the acoustic resonance phenomenon does not occur, the electrode wear can be prevented, and a stable lighting state can be maintained.

Examining the above-mentioned experimental results of the variation range of the electrode tip temperature by the inventors of the present application, the components of the frequency component whose power is less than 5% of the total power are: The electrodes are not affected and the frequency is, for example, 10
Even if the frequency is 0 Hz or less, the temperature of the electrode does not rise. Therefore, the frequency component of which the power is 5% or more of the total power has a frequency of 2k.
It may be W or more. It should be noted that the lower limit of the frequency of the component is set to 2 kHz because when the drive current is 1 kHz,
This is because the frequency of electric power is 2 kHz.

Further, when the power waveform of the driving power waveform of the lamp is subjected to frequency decomposition, if the frequency of the component which is 5% or more of the total power is equal to or lower than the lowest acoustic resonance frequency of the lamp, the acoustic resonance phenomenon is generated. It becomes possible to drive the lamp with the prevention of

Here, it can be considered that the lowest acoustic resonance frequency of the lamp is the frequency at which the acoustic resonance occurs due to the size of the discharge space of the lamp and the like. Needless to say, the lowest frequency at which such acoustic resonance occurs is on the low frequency side, and is therefore determined in relation to the length of the discharge space of the lamp in the longitudinal direction.

FIG. 1 shows that when high-pressure mercury lamps having different discharge spaces are lit by a sinusoidal current and the frequencies are changed, the lowest lighting frequency at which acoustic resonance occurs in each lamp is shown. It shows the relationship between double, that is, the lowest acoustic resonance frequency and L of each lamp.

The minimum frequency at which the acoustic resonance frequency is generated can be expressed by the following equation (2) in relation to the length of the discharge vessel in the longitudinal direction. (Note that this equation (2) is shown by a curve in the figure.)

[0022]

[Equation 2] ^{f [kHz] = 197.2 × L} -0.83 (2)

That is, among the frequency components when the power waveform is frequency-resolved, the frequency components of 5% or more with respect to the total power supplied are expressed by the above formula (2) or less at which no acoustic resonance of the lamp occurs. If present in the frequency domain, no acoustic resonance will occur.

From the above results, when the discharge and the power waveform thereof are frequency-decomposed, the frequency of the component which is 5% or more of the total power is 2 kHz or more and the lowest acoustic resonance frequency of the lamp or less. With such a selection, it is possible to drive the lamp in which the fluctuation of the electrode tip temperature during one cycle is small and the acoustic resonance phenomenon is prevented.

By the way, the above describes the conditions for driving the lamp with a general AC waveform. In the case of limiting to the AC sine wave, the current also becomes a sine wave, so the power waveform consists of only the DC component and the frequency component twice the frequency of the voltage waveform. It may be in the range of ½ or less of the lowest acoustic resonance frequency in the lamp.

The discharge space length L is 6 mm and the rated power consumption is 1
When driving a high-pressure mercury lamp of 20 W with an alternating sine wave current, the frequency is 1 kHz or higher, 22.3 kHz.
The lighting frequency may be set so that the lamp is driven so that it falls within the range of z or less. The component of the power waveform excluding the DC component is 1 in the range of 2 kHz or more and less than 44.6 kHz.
Will exist.

[0027]

As described above, according to the present invention, it is possible to provide a lamp driving method as a light source for a video projector, which has a long life and a stable light output.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between an inner length L of a discharge space of a high-pressure mercury lamp according to the present invention and a minimum acoustic resonance frequency.

FIG. 2 is an explanatory diagram showing a configuration of a high pressure mercury lamp according to the present invention.

[Explanation of symbols]

1: High pressure mercury lamp 2: Discharge container 3: Sealing part 4: Electrode 5: Metal foil 6: External lead

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3K072 AA12 AC02 AC11 CA03 CA06                       CA14 CA16 GB01                 5C039 HH02 HH06

Claims (3)

[Claims] 1. Inside a discharge vessel made of quartz glass,
A pair of electrodes are arranged facing each other, and 0.16 mg
/ Mm ³ or more of mercury, a rare gas, and a halogen are enclosed, and a method for driving a high-pressure mercury lamp, which is driven at a tube wall load of 0.8 W / mm ² or more, is supplied to the high-pressure mercury lamp. Of the frequency components when the power waveform of the power is decomposed into frequencies, all frequency components that account for 5% or more of the total power supplied are 2 kHz.
The method for driving a high-pressure mercury lamp, which is not less than the lowest acoustic resonance frequency in the high-pressure mercury lamp. 2. Inside the discharge vessel made of quartz glass,
A pair of electrodes are arranged facing each other, and 0.16 mg
/ Mm ³ or more of mercury, a rare gas, and a halogen are enclosed, and a driving method of a high-pressure mercury lamp driven by a tube wall load of 0.8 W / mm ² or more. Wave voltage is applied, and the frequency of the current supplied to the high-pressure mercury lamp is 1 k.
A driving method for a high-pressure mercury lamp, which is equal to or higher than Hz and is equal to or lower than 1/2 of the lowest acoustic resonance frequency in the high-pressure mercury lamp. 3. The method for driving a high-pressure mercury lamp according to claim 1, wherein the lowest acoustic resonance frequency is 197.2 when the axial length of the discharge space is Lmm. × L ^−0.83 [kHz] The method for driving a high-pressure mercury lamp, characterized in that