JPH10326681A - Discharge lamp lighting device and method - Google Patents

Abstract

(57) [Problem] To provide a device for lighting a high-intensity discharge lamp, in particular, to eliminate the color unevenness of the discharge arc due to the cataphoresis phenomenon and minimize the curvature of the discharge arc to form a straight discharge arc. I do. SOLUTION: A waveform having an acoustic resonance frequency component which excites a mode in which a discharge arc is straightened is determined by a sound velocity in a discharge space medium of a discharge lamp and a length of a discharge space intersecting the discharge arc, and an acoustic wave. Lighting means for outputting a composite wave with a waveform whose polarity changes at a frequency having the resonance frequency as the upper limit turns on the discharge lamp.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting apparatus for reducing the curvature of a discharge arc due to harmful gravitationally induced convection when the discharge lamp is horizontally lit, and is particularly useful for an HID lamp (high intensity discharge lamp). The present invention relates to a discharge lamp lighting device.

[0002]

2. Description of the Related Art In recent years, HID lamps have been widely applied to outdoor lighting and the like due to their high efficiency and long life.
Among them, metal halide lamps have good color rendering properties, and by taking advantage of their characteristics, are becoming popular not only in the field of outdoor lighting but also in the field of indoor lighting, and are attracting attention as light sources for video equipment and headlights for vehicles.

[0003] Conventional discharge lamp lighting devices include
Proceedings of the Annual Meeting of the Illuminating Engineering Institute of Japan Tokyo Section No. 10 is described. In this discharge lamp lighting device, a low-frequency (several 100 Hz) rectangular wave current is supplied to the HID lamp, which is a discharge lamp, so that fluctuations, extinguishment, and lamp breakdown of the discharge arc caused by an acoustic resonance phenomenon specific to the HID lamp are prevented. It discloses that the lighting can be stably performed. However, although the HID lamp can be stably turned on by this kind of lighting device when it is turned on horizontally, the discharge arc bends upward in a bow shape due to the influence of gravity induced convection. When the discharge arc is curved, the temperature rise in the upper part of the discharge space increases, the deterioration of the quartz glass forming the discharge space, that is, the devitrification is large, and the life of the lamp is shortened. There was a problem that the efficiency was reduced.

In particular, in recent years, metal halide lamps, which have attracted attention as light sources for video equipment and headlights for vehicles, are being reduced in arc length, and it is necessary to further increase the mercury pressure in the discharge space during lamp operation. is there. Increasing the mercury pressure increases gravity induced convection and the curvature of the discharge arc becomes greater, further reducing lamp life and efficiency. As a discharge lamp lighting device which solves these problems, there is one disclosed in Japanese Patent Publication No. 7-9835. This discharge lamp lighting device will be described with reference to FIG.

FIG. 14 is a diagram showing a lamp current waveform when the discharge lamp is lit by the above-described conventional discharge lamp lighting device (Japanese Patent Publication No. 7-9835). By reducing the influence of gravity induced convection of the filling of the discharge lamp by acoustic resonance to the DC current 51 and supplying the lamp with a current waveform superimposed on an AC waveform 52 having a frequency that straightens the discharge arc, the discharge arc is reduced. It teaches that the curvature can be reduced to make a substantially straight discharge arc. By making the discharge arc straight, the temperature of the hot spot at the upper part of the discharge space, which is a factor that shortens the life of the discharge lamp, can be lowered, and the life of the lamp can be prolonged. There are advantages such as the luminous efficiency can be improved.

[0006]

However, in the above-described conventional discharge lamp lighting device, since a unidirectional current flows through the discharge lamp, the electric field intensity in the discharge space of the discharge lamp periodically changes, but the electric field intensity always changes in one direction. An electric field is generated. Therefore, there is a problem that color unevenness occurs in the discharge arc due to the cataphoresis phenomenon in which the filler is biased. In addition, since the temperature on the electrode axis has an asymmetrical temperature distribution with the anode side high and the cathode side low, the curvature of the discharge arc can be reduced somewhat even if the frequency for exciting the mode for straightening the discharge arc is superimposed. Had a problem of being small.

The present invention solves the above-mentioned conventional problems. A discharge lamp lighting device capable of forming a straight discharge arc by avoiding the cataphoresis phenomenon, eliminating color unevenness of the discharge arc, and minimizing the curvature of the discharge arc. It is intended to provide.

[0008]

SUMMARY OF THE INVENTION According to a first aspect, the present invention is an apparatus for operating a discharge lamp having a glass envelope defining a discharge space, wherein the acoustic resonance excites a mode that straightens the discharge arc. Generating means for generating a first waveform signal which is a waveform having a frequency component of a frequency, wherein the center line of the waveform is maintained at a constant level; A discharge lamp lighting device characterized by having a modulation means for modulating the first waveform signal with a periodicity so that the polarity alternately changes at a lower modulation frequency and generating a modulation signal.

Thus, the discharge arc can be easily controlled straight.

According to a second aspect of the present invention, the acoustic resonance frequency is determined by the speed of sound in the discharge space medium of the discharge lamp and the length of the discharge space intersecting the discharge arc. A discharge lamp lighting device according to the aspect of the present invention.

The present invention according to a third aspect is the discharge lamp lighting device according to the first aspect, wherein the discharge lamp is sealed with at least a metal halide or mercury as a filler.

According to a fourth aspect of the present invention, the modulation depth α / β when the value from the peak of the first waveform signal to the peak is α and the effective value of the modulation signal is β is 0.3 or more. The discharge lamp lighting device according to the first aspect, wherein: Thereby, the discharge arc can be kept almost straight.

The present invention according to a fifth aspect is the discharge lamp lighting device according to the fourth aspect, wherein the modulation depth α / β is 0.8 or more. Thereby, the discharge arc can be kept even more straight.

According to a sixth aspect of the present invention, there is provided the discharge lamp lighting device according to the first aspect, wherein the center line changes by a substantially rectangular wave.

The present invention according to a seventh aspect is the discharge lamp lighting device according to the first aspect, wherein the frequency of the substantially rectangular wave is within a range of 100 Hz to 2 kHz.

The invention according to an eighth aspect is the discharge lamp lighting device according to the first aspect, wherein the center line of the first waveform signal is substantially at the ground level.

According to a ninth aspect of the present invention, the modulating means has a polarity changing power supply for outputting a waveform whose polarity changes at a frequency having the acoustic resonance frequency as an upper limit, and a synthesizing circuit. A discharge lamp lighting device according to an eighth aspect.

According to a tenth aspect of the present invention, the modulating means includes: a DC power supply for generating a DC signal; a first waveform signal on which the first waveform signal and the DC signal are superimposed; The discharge lamp lighting device according to an eighth aspect, comprising: a superimposing circuit for outputting; and an inverter circuit for converting the first waveform signal on which the DC component is superimposed into the modulation signal.

The invention according to an eleventh aspect is the discharge lamp lighting device according to the first aspect, wherein the center line of the first waveform signal is at a predetermined DC level.

The present invention according to a twelfth aspect is the discharge lamp lighting apparatus according to the eleventh aspect, wherein the modulation means comprises an inverter circuit for converting a first waveform signal into the modulation signal.

According to a thirteenth aspect of the present invention, there is provided an apparatus for operating a discharge lamp having a glass envelope defining a discharge space, having a frequency component of an acoustic resonance frequency for exciting a mode in which a discharge arc is straightened. Generating means for generating a first waveform signal having a waveform whose center line is held at a constant level; and a second waveform signal having a frequency lower than the first resonance signal and the acoustic resonance frequency. Is a discharge lamp lighting device, characterized by having a modulation means for modulating as if alternately switched on the time axis.

According to a fourteenth aspect of the present invention, there is provided a method for operating a discharge lamp having a glass envelope defining a discharge space, comprising a frequency component of an acoustic resonance frequency for exciting a mode in which a discharge arc is straightened. Generating a first waveform signal having a centerline of the waveform maintained at a constant level, wherein the centerline of the first waveform signal alternates in polarity at a modulation frequency lower than the acoustic resonance frequency; A method for lighting a discharge lamp, characterized in that the first waveform signal is modulated with a periodicity so that the first waveform signal changes to the following, and a modulated signal is generated.

According to a fifteenth aspect of the present invention, the curvature of the discharge arc is controlled by a value α from peak to peak of the first waveform signal. It is.

According to a sixteenth aspect of the present invention, there is provided a method of operating a discharge lamp having a glass envelope defining a discharge space, comprising a frequency component of an acoustic resonance frequency for exciting a mode in which a discharge arc is straightened. Generating a first waveform signal having a centerline of the waveform maintained at a constant level, wherein the first waveform signal and a second waveform signal having a frequency lower than the acoustic resonance frequency are alternately generated; A discharge lamp lighting method is characterized in that modulation is performed as switching on a time axis.

According to a seventeenth aspect of the present invention, in the discharge lamp according to the sixteenth aspect, the curvature of the discharge arc is controlled by a time ratio of a period during which the first waveform signal appears in a unit period. It is a lighting method.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a sine wave having an acoustic resonance frequency f2 for exciting a mode for straightening a discharge arc and a frequency f1 (400 Hz) having a waveform whose polarity changes at a frequency lower than the acoustic resonance frequency f2. 3 shows a composite wave with the rectangular wave of FIG. This composite wave is a waveform in which a sine wave of the acoustic resonance frequency f2 and a rectangular wave of the frequency f1 are superimposed. FIG.
Is supplied to the lamp, and the difference between the maximum value and the minimum value of the sine wave of the acoustic resonance frequency f2, that is, the value α from peak to peak is changed, as shown in FIG. The results of experimentally determining the magnitude L of the curvature of the discharge arc and the temperature at the surface Ts of the arc tube will be described below.

A test was performed using two discharge lamps, a 35 W metal halide lamp and a 200 W metal halide lamp. As shown in FIG. 2A, the discharge lamp is lit horizontally to supply the current waveform shown in FIG.
ramp 1 while changing β (β is the effective value of the composite wave)
The distance L between the electrode axis of the cross section orthogonal to the electrode axis which is the center line between the electrodes lm and ln of t and the center of the discharge arc was experimentally obtained. The acoustic resonance frequency f2 is about 150 kHz for a 35 W metal halide lamp, and 200 W
In the case of a metal halide lamp, the frequency is about 32 kHz. For both lamps, the distance L between the electrode axis and the center of the discharge arc becomes smaller at a modulation depth of 0.3 or more. Furthermore, a modulation depth of 0.8
Thus, the distance L between the electrode axis and the center of the discharge arc is minimized, and the discharge arc becomes almost straight. The results of these experiments are shown in FIG.

Therefore, in the present invention, the modulation depth α / β is preferably at least 0.3, more preferably at least 0.8.

FIG. 3 shows the surface temperature at the upper part Ts of the arc tube 1t having a cross section orthogonal to the electrode axis at the center between the electrodes while supplying the current waveform shown in FIG. 1 and changing the modulation depth while horizontally lighting the 200 W metal halide lamp. This is a result obtained experimentally. At a modulation depth of 0.3 or more, the curvature of the discharge arc gradually decreases, so that the surface temperature of the upper arc tube gradually decreases. Furthermore, the surface temperature at the upper part Ts of the arc tube becomes minimum at a modulation depth of 0.8 or more, which becomes a substantially straight discharge arc. The surface temperature of the lower portion Tb of the arc tube 1t tends to gradually increase at a modulation depth of 0.3 or more.

From the results of the above two experiments, the modulation depth of 0.
By setting it to 3 or more, the curvature of the discharge arc can be reduced, so that the temperature at the high temperature point in the upper portion Ts of the discharge space, which is a factor for shortening the life of the discharge lamp, can be reduced, and the life of the lamp can be extended. At the same time, the coldest point temperature of the lower part Tb of the discharge space can be raised, so that the luminous efficiency can be improved. That is, the temperature distribution along one circumference around the arc tube can be made constant. Further, at a modulation depth of 0.8 or more, the curvature of the discharge arc is minimized and can be made almost straight, and the effect is large. Further, since a composite wave of the acoustic resonance frequency and the rectangular wave shown in FIG.
The polarity of the lamp current changes with the period of the rectangular wave of z, and the polarity of the electric field generated in the discharge space changes periodically. Therefore, the cataphoresis phenomenon can be prevented, the color unevenness of the discharge arc can be prevented, and the temperature distribution on the electrode axis can be symmetrical about the center between the electrodes. it can.

Next, the frequency f of the rectangular wave with a constant modulation depth
The result of experimentally determining the upper arc tube surface temperature by changing only 1 will be described below. FIG. 4 shows the results obtained by applying the waveform shown in FIG. 1 to a 200 W metal halide lamp and experimentally obtaining the surface temperature at the upper portion Ts of the arc tube while changing only the frequency f1 of the rectangular wave at a constant modulation depth of 1.0. is there. If the frequency f1 of the rectangular wave exceeds 2 kHz, the surface temperature in the upper part Ts of the arc tube tends to increase. This indicates that the curvature of the discharge arc increases. At 2 kHz or less, the temperature is low and almost constant, but at 100 Hz or less, visual flickering due to alternation of the lamp current polarity poses a problem. Therefore, the frequency f1 of the rectangular wave should be selected in the range of 100 Hz to 2 kHz.

FIG. 5 shows the synthesis of a sine wave having an acoustic resonance frequency f2 for exciting a mode in which a discharge arc is straightened and a triangular wave having a frequency f3 whose polarity changes at a frequency lower than the acoustic resonance frequency f2. Show the waves. This composite wave has a waveform in which a sine wave of the acoustic resonance frequency f2 and a triangular wave of the frequency f3 are superimposed. Even if the current having the waveform shown in FIG. 5 is supplied to the lamp, the curvature of the discharge arc can be similarly reduced, and substantially straightened by increasing the modulation depth. Furthermore, since the polarity of the electric field generated in the discharge space changes at a period determined by the frequency f3, the cataphoresis phenomenon can be prevented, the color unevenness of the discharge arc can be prevented, and the temperature distribution on the electrode axis is centered on the center between the electrodes. Therefore, the curvature of the discharge arc can be reduced.

FIG. 6 shows a composite wave of a sine wave having an acoustic resonance frequency f2 for exciting a mode for straightening a discharge arc and a rectangular wave having a waveform whose polarity changes at a frequency lower than the acoustic resonance frequency f2. In other words, it shows a composite wave in which sine waves and rectangular waves are alternately arranged in a time-division manner. This synthesized wave is obtained by converting a sine wave and a rectangular wave having an acoustic resonance frequency f2 into T4 and T5.
The waveform is switched alternately at a predetermined cycle determined by Even when the current having the waveform shown in FIG. 6 is supplied to the lamp, the curvature of the discharge arc can be similarly reduced, and the discharge arc can be made straighter as the ratio of the time T4 to the total time of T4 and T5 increases.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 7A shows a first embodiment for a 35 W metal halide lamp.
In FIG. 7A, reference numeral 1 denotes a 35 W metal halide lamp as described above, which is a discharge lamp in which mercury, metal halides sodium iodide and scandium iodide are sealed as a filler in a glass envelope defining a discharge space. . Reference numeral 2 denotes a lighting unit that supplies a predetermined waveform to the 35 W metal halide lamp 1 and lights the lamp. The lighting unit 2 outputs an AC power supply that outputs a waveform having a frequency component of an acoustic resonance frequency that excites a mode in which a discharge arc is straightened. A
And a 400 Hz rectangular wave generating circuit 4 which is a polarity changing power supply that outputs a waveform whose polarity changes at a frequency whose upper limit is the acoustic resonance frequency.
And a combining circuit 5 for combining the output of the sine wave generating circuit 3 and the output of the rectangular wave generating circuit 4. FIG. 8 shows the waveform of each part of the first embodiment configured as described above.

FIG. 8A shows an output waveform of the rectangular wave generating circuit 4, which is a 400 Hz rectangular wave. FIG. 8 (b)
The output waveform of the sine wave generation circuit 3 is a 150 kHz sine wave. FIG. 8C shows an output waveform of the synthesizing circuit 5 in which the output of the sine wave generating circuit 3 and the output of the rectangular wave generating circuit 4 are superimposed, and the waveform of FIG. Is applied. With the above configuration, the 35 W metal halide lamp 1 has a sine wave (150 kHz) having an acoustic resonance frequency of 400 Hz and an acoustic resonance frequency for exciting a mode for straightening a discharge arc as shown in FIG.
Can be applied, and a straight discharge arc having no color unevenness in the discharge arc can be realized.

FIG. 7B shows a modification of the lighting means 2 shown in FIG. 7A. A switch 6 and a time division control circuit 8 are provided instead of the synthesis circuit 5. The time division control circuit 8 controls the switching ratio indicated by T4 and T5 in FIG. 6, and switches the switch 6 based on the switching ratio. Therefore, the waveform shown in FIG. 6 is applied to the 35 W metal halide lamp.

The shape of the discharge arc can be continuously varied from a curved discharge arc to a straight discharge arc by changing the time ratio T4 / (T4 + T5) for applying the output of the sine wave generation circuit 3.

As shown in FIG. 13, by changing the curvature of the discharge arc, when the light from the 35W metal halide lamp 1 is irradiated through the reflecting mirror 7, the light distribution can be varied. For example, the position of the discharge arc can be changed to 1a, 1b, 1c shown in FIG. 13, whereby the light reflected from the reflecting mirror 7 can be changed to La, Lb, Lc.

In the discharge lamp lighting device shown in FIG. 7A, the position of the discharge arc can be controlled by changing any of the parameters of the modulation depth α / β.

FIG. 9 shows the second embodiment. In FIG. 9, reference numeral 1 denotes 35 similar to the first embodiment.
It is a W metal halide lamp. Reference numeral 12 denotes lighting means for supplying a predetermined waveform to the 35 W metal halide lamp 1 and lighting the same. The lighting means 12 applies a direct current superimposed with a waveform having a frequency component of an acoustic resonance frequency for exciting a mode for straightening a discharge arc. A DC power supply 13 for outputting, a rectangular wave conversion circuit 14 which is an inverter circuit for changing the polarity of the output of the DC power supply 13 at a frequency whose upper limit is the acoustic resonance frequency, and a sufficient voltage for starting the discharge of the 35 W metal halide lamp 1. And a starting means 15 for applying a high voltage. The DC power supply 13 includes a DC power supply 16 that outputs a DC waveform whose instantaneous value does not change with time and an AC power supply B that outputs a waveform having a frequency component of an acoustic resonance frequency that excites a mode for straightening a discharge arc. It comprises a high-frequency power supply 17 that outputs a sine wave (150 kHz) of a certain acoustic resonance frequency, and a superimposing circuit 18 that superimposes the output of the high-frequency power supply 17 on the output of the DC power supply 16. FIG. 10 shows the waveform of each part of the second embodiment configured as described above.

FIG. 10A shows an output current waveform of the DC power supply 16. The DC power supply 16 constitutes a step-down chopper circuit including the DC power supply 19, the transistor 20, the diode 21, the choke coil 22, and the capacitor 23. Resistance 24
The control circuit 27 calculates the lamp power from the signal corresponding to the lamp voltage detected at 25 and the signal corresponding to the lamp current detected at the resistor 26, and varies the on / off ratio of the transistor 20 so that the lamp power is fixed at 35W. And outputs a DC waveform whose instantaneous value does not change with time.

FIG. 10B shows the output current waveform of the high-frequency power supply 17. The high-frequency power supply 17 outputs a sine wave having an acoustic resonance frequency and a predetermined modulation of the output current of the sine wave power supply 28. And a choke coil 29 for limiting the current to a depth, and outputs a sine wave current having an acoustic resonance frequency.

FIG. 10C shows the output current waveform of the superposition circuit 18. The superposition circuit 18 is composed of a choke coil 30 and a capacitor 31 so that the output current of the DC power supply 16 does not flow into the high-frequency power supply 17. DC cut at 31 and the output current of the high frequency power supply 17
In this configuration, a high-frequency cut is performed by the choke coil 30 so as not to flow into the circuit 6, and a connection point between the choke coil 30 and the capacitor 31 is used as an output terminal to output a direct current on which a sine wave of an acoustic resonance frequency is superimposed.

FIG. 10D shows an output current waveform of the rectangular wave conversion circuit 14, and the rectangular wave conversion circuit 14
2, 33, 34, 35 and a drive circuit 36. The transistors 32, 35 are driven by an output signal from the drive circuit 36.
Are turned on and the periods when the transistors 33 and 34 are turned on alternately, so that the DC having the sine wave of the acoustic resonance frequency output from the superposition circuit 18 is superimposed on
Converted to 0Hz AC, 35W metal halide lamp 1
To supply.

With the above configuration, when the 35 W metal halide lamp 1 is turned on by the high voltage from the starting means 15, the acoustic resonance frequency for exciting the mode for straightening the discharge arc shown in FIG. And a rectangular wave having a frequency (400 Hz) can be supplied, so that a straight discharge arc having no color unevenness in the discharge arc can be realized. In addition, sine wave power supply 2
By changing the output voltage of No. 8, the modulation depth can be freely changed and the degree of curvature of the discharge arc can be changed, so that the light distribution can be varied.

Hereinafter, a third embodiment of the present invention will be described with reference to FIG.
Shown in In FIG. 11, reference numeral 1 denotes a 35 W metal halide lamp, which is a discharge lamp similar to those of the first and second embodiments. 40 starts 35W metal halide lamp 1.
DC power supply 41 which is a lighting means for lighting and outputs a DC having a waveform having a frequency component of an acoustic resonance frequency for exciting a mode in which a discharge arc is straightened.
And a rectangular wave conversion circuit 14, which is an inverter circuit for changing the polarity of the output of the DC power supply 41 at a frequency having the upper limit of the acoustic resonance frequency, and applying a high voltage sufficient to start the discharge of the 35W metal halide lamp 1. And the starting means 15 which performs the operation. Note that the rectangular wave conversion circuit 14 and the starting means 15 have the same configuration as in the second embodiment.

The difference from the second embodiment is that the DC power supply 4
The configuration and operation of the DC power supply 41 will be described below. The DC power supply 41 constitutes a step-down chopper circuit including a DC power supply 42, a transistor 43 serving as a switching element, a diode 44, a choke coil 45, and a capacitor 46, and a signal corresponding to a lamp voltage detected by resistors 47 and 48 and a resistor 49. The control circuit 50 calculates the lamp power from a signal corresponding to the detected lamp current, and varies the on / off ratio of the transistor 43 so that the lamp power becomes constant at 35 W. A filter circuit composed of the choke coil 45 and the capacitor 46 is set to 150 kHz, which is an acoustic resonance frequency that excites the mode in which it is straightened.
The DC power supply 41
Can output a direct current that fluctuates periodically at 150 kHz.

FIG. 12A shows the output current waveform of the DC power supply 41 of the third embodiment configured as described above, and FIG. 12B shows the output current waveform of the rectangular wave conversion circuit 14. . As in the first and second embodiments, a combined wave current of a waveform having a frequency component of an acoustic resonance frequency for exciting a mode for straightening a discharge arc and a rectangular wave having a frequency of 400 Hz is applied to a 35 W metal halide lamp 1. Therefore, a straight discharge arc having no color unevenness in the discharge arc can be realized. Further, the choke coil 45 and the capacitor 46 are set to predetermined values, and the ON / OFF frequency of the transistor 43 is set to 150 kHz, which is a frequency at which the discharge arc can be straightened at the acoustic resonance frequency. Can be added with a predetermined modulation depth, so that the configuration of the lighting means is simplified.

In the above embodiment, the discharge lamp is not limited to a 35 W metal halide lamp or 200 W metal halide lamp, but may be another discharge lamp such as a high pressure mercury lamp or a high pressure sodium lamp.

Although the rectangular wave generating circuit 4 generates a standard rectangular wave in the present embodiment, it may be configured to generate a trapezoidal wave having slopes at rising and falling edges of the waveform. May be generated. Similarly, the rectangular wave conversion circuit 14 may have another configuration as long as it can be converted into a substantially rectangular wave. Furthermore, the square wave generation circuit 4 and the square wave conversion circuit 14 perform sine waves, triangle waves, staircase waves,
It may be a configuration that can generate a waveform whose polarity changes at a frequency up to the acoustic resonance frequency that excites the mode that straightens the discharge arc such as a sawtooth wave, even if the polarity changes even with a waveform containing some DC component Alternatively, a positive or negative asymmetric waveform may be used. The point is that any waveform may be used as long as the electric field in the discharge space of the discharge lamp does not become unidirectional, so that the cataphoresis phenomenon can be avoided without the filler being offset.

Further, the frequency of the rectangular wave generating circuit 4 and the rectangular wave converting circuit 14 is set to 400 Hz. However, if the frequency is within the range of 100 Hz to 2 kHz as described above, the effect of minimizing the curvature of the discharge arc can be obtained. it can.

The sine wave is generated by using the 150 kHz sine wave generation circuit 3 as the AC power supply A for outputting a waveform having the frequency component of the acoustic resonance frequency for exciting the mode in which the discharge arc is straightened. The waveform need not be a sine wave but may be a triangular wave or a sawtooth wave, as long as the waveform has a frequency component of an acoustic resonance frequency. Sine wave power supply 28
The same is true for

Further, the sine wave generating circuit 3 and the sine wave power supply 28
The frequency modulation of the sine wave generated by adding the FM modulation function to the predetermined period and the width of the sine wave enables the acoustic resonance frequency to excite the mode in which the discharge arc generated due to the aging and variation of the lamp characteristics is straightened. Changes and variations can be absorbed. Similarly, if the on / off frequency of the transistor 43 of the third embodiment can be FM-modulated by a signal from the control circuit 50, the same effect can be obtained.

The high-frequency power supply 17 comprises a sine-wave power supply 28 and a choke coil 29, and the output current of the sine-wave power supply 28 is limited by the impedance of the choke coil 29 so as to have a predetermined modulation depth. A resistor / capacitor other than a coil and a composite configuration thereof may be used.

Although the DC power supply 16 for outputting a waveform whose instantaneous value does not change with time is constituted by a step-down chopper circuit, a similar structure can be applied to other circuit systems such as a step-up chopper circuit and an inverting chopper circuit.

The control circuits 27 and 50 operate the transistors 20 and 4 so that the lamp power becomes constant at the rated value of 35 W.
The on / off ratio of 3 is controlled. However, in order to supplement the light output at the beginning of lighting, it may be controlled to supply power equal to or higher than the rated value at the beginning of lighting, or the lamp characteristics such as dimming control may be varied A configuration for controlling may be used.

The superimposing circuit 18 includes the choke coil 3
Although the configuration is made up of 0 and the capacitor 31, it goes without saying that another configuration may be used.

Further, the DC power supply 41 may be constituted by another circuit system such as a boosting chopper circuit, an inverting chopper circuit, or a forward converter circuit as long as it can output a DC having a waveform having a frequency component of an acoustic resonance frequency superimposed thereon.

The transistor 4 is used as a switch element.
Although 3 was used, other elements such as FET, thyristor, and IGBT may be used.

As described above, in the present invention,
Circuits 3, 28 and 41 generate a first waveform signal having a waveform having an acoustic resonance frequency that excites a mode for straightening the discharge arc, the center line of the waveform being held at a constant level. It can be said that it is a means. Further, in each of the circuits 4 and 5 shown in FIG. 7A, the circuits 16, 18, and 14 shown in FIG. 9, and the circuit 14 shown in FIG. 11, the center line of the first waveform signal is higher than the acoustic resonance frequency. The first so that the polarity changes alternately at a low modulation frequency.
It can be said that it is a modulation means for modulating a waveform signal with a periodicity and generating a modulation signal.

Further, according to the present invention, the circuits 4 and 6 shown in FIG. 7B are used to modulate the first waveform signal and the second waveform signal having a frequency lower than the acoustic resonance frequency so that they are switched on the time axis. It can be said that it is a means.

As described above, the present invention combines a waveform having a frequency component of an acoustic resonance frequency that excites a mode in which a discharge arc is straightened with a waveform whose polarity changes at a frequency whose upper limit is the acoustic resonance frequency. By lighting the discharge lamp with waves, a straight discharge arc having no color unevenness in the discharge arc can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a composite wave of a sine wave having an acoustic resonance frequency f2 and a rectangular wave having a frequency f1 for exciting a mode in which a discharge arc is straightened.

FIG. 2A is an explanatory view showing the curvature of a discharge arc in a lamp. (B) is a diagram showing a change in the distance between the electrode axis and the arc center when the modulation depth is changed.

FIG. 3 is a diagram showing a change in the upper arc tube surface temperature when the modulation depth is changed.

FIG. 4 is a diagram showing a change in the upper arc tube surface temperature when the frequency f1 of the rectangular wave is changed.

FIG. 5 is a diagram showing a composite wave of a sine wave having an acoustic resonance frequency f2 and a triangular wave having a frequency f3 for exciting a mode in which a discharge arc is straightened.

FIG. 6 is a diagram showing a composite wave of a sine wave and a rectangular wave having an acoustic resonance frequency f2 that excites a mode in which a discharge arc is straightened.

FIG. 7A is a block diagram of the discharge lamp lighting device according to the first embodiment of the present invention. (B) A block diagram showing a modification of the first embodiment.

FIG. 8A is an output waveform diagram of the rectangular wave generation circuit 4. (B) An output waveform diagram of the sine wave generation circuit 3. (C) The output waveform diagram of the synthesis circuit 5.

FIG. 9 is a circuit diagram of a discharge lamp lighting device according to a second embodiment of the present invention.

10A is an output waveform diagram of a DC power supply 16. FIG. (B) Output waveform diagram of the high-frequency power supply 17. (C) The output waveform diagram of the superimposing circuit 18. (D) The output waveform diagram of the rectangular wave conversion circuit 14.

FIG. 11 is a circuit diagram of a discharge lamp lighting device according to a third embodiment of the present invention.

12A is an output waveform diagram of a DC power supply 41. FIG. (B) The output waveform diagram of the rectangular wave conversion circuit 14.

FIG. 13 is an explanatory diagram showing variable light distribution when the discharge lamp according to the present invention is used for a reflector.

FIG. 14 is a lamp current waveform diagram when a discharge lamp is lit by a conventional discharge lamp lighting device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 35W metal halide lamp 2 Lighting means 3 Sine wave generating circuit 4 Square wave generating circuit 5 Synthesizing circuit 12 Lighting means 13 DC power supply for outputting a DC with a waveform having an acoustic resonance frequency component superimposed thereon 14 Square wave converting circuit 15 Starting means 16 DC power supply that outputs a DC waveform whose instantaneous value does not change with time 17 High-frequency power supply that outputs a sine wave of an acoustic resonance frequency 18 Superposition circuit 40 Lighting means 41 Outputs a DC with a waveform having an acoustic resonance frequency component superimposed DC power supply

Claims (17)

[Claims] An apparatus for lighting a discharge lamp having a glass envelope defining a discharge space, comprising a waveform having a frequency component of an acoustic resonance frequency for exciting a mode for straightening a discharge arc, the waveform comprising the waveform. Generating means (3; 28; 41) for generating a first waveform signal whose center line is maintained at a constant level; and a center line of the first waveform signal having a modulation frequency lower than the acoustic resonance frequency. So that the polarity changes alternately.
Modulating means (4, 5; 16, 18, 14, 14; 1) for modulating a waveform signal with a periodicity and generating a modulated signal.
4) A discharge lamp lighting device comprising: 2. The discharge lamp lighting device according to claim 1, wherein the acoustic resonance frequency is determined by a sound speed in a discharge space medium of the discharge lamp and a length of the discharge space intersecting the discharge arc. . 3. The discharge lamp lighting device according to claim 1, wherein the discharge lamp is sealed with at least a metal halide or mercury as a filler. 4. A modulation depth α / β when a value from peak to peak of the first waveform signal is α and an effective value of the modulation signal is β is not less than 0.3. The discharge lamp lighting device according to claim 1. 5. The discharge lamp lighting device according to claim 4, wherein the modulation depth α / β is 0.8 or more. 6. The discharge lamp lighting device according to claim 1, wherein the center line changes by a substantially rectangular wave. 7. The discharge lamp lighting device according to claim 6, wherein the frequency of the substantially rectangular wave is in a range from 100 Hz to 2 kHz. 8. The discharge lamp lighting device according to claim 1, wherein the center line of the first waveform signal is substantially at a ground level. 9. The modulation means comprises a polarity changing power supply (4) for outputting a waveform whose polarity changes at a frequency whose upper limit is the acoustic resonance frequency, and a synthesizing circuit (5). Item 10. A discharge lamp lighting device according to Item 8. 10. The modulation means generates a DC signal.
A C power supply (16), a superimposing circuit (18) for superimposing the first waveform signal and the DC signal and outputting a first waveform signal on which a DC component is superimposed, and a first waveform signal on which the DC component is superimposed 9. The discharge lamp lighting device according to claim 8, further comprising an inverter circuit (14) for converting the signal into the modulation signal. 11. The discharge lamp lighting device according to claim 1, wherein the center line of the first waveform signal is at a predetermined DC level. 12. The discharge lamp lighting device according to claim 11, wherein said modulation means comprises an inverter circuit (14) for converting a first waveform signal into said modulation signal. 13. An apparatus for lighting a discharge lamp having a glass envelope defining a discharge space, comprising: a waveform having a frequency component of an acoustic resonance frequency that excites a mode in which a discharge arc is straightened. Generating means (3; 28; 41) for generating a first waveform signal whose center line is maintained at a constant level; and a second waveform signal having a frequency lower than the first resonance signal and the acoustic resonance frequency. A discharge lamp lighting device, characterized in that it has a modulating means (4, 6) for modulating as if alternately switched on the time axis. 14. A method of lighting a discharge lamp having a glass envelope defining a discharge space, comprising: a waveform having a frequency component of an acoustic resonance frequency for exciting a mode for straightening a discharge arc, the waveform comprising: Generates a first waveform signal whose center line is maintained at a constant level, such that the center line of the first waveform signal alternates in polarity at a modulation frequency lower than the acoustic resonance frequency. First
A method of lighting a discharge lamp, comprising modulating a waveform signal with a periodicity and generating a modulation signal. 15. The discharge lamp lighting method according to claim 14, wherein the curvature of the discharge arc is controlled by a value α between the peaks of the first waveform signal. 16. A method for operating a discharge lamp having a glass envelope defining a discharge space, comprising: a waveform having a frequency component of an acoustic resonance frequency for exciting a mode for straightening a discharge arc, the waveform comprising: Generates a first waveform signal whose center line is held at a constant level, and modulates the first waveform signal and the second waveform signal having a frequency lower than the acoustic resonance frequency to be alternately switched on the time axis. A method for lighting a discharge lamp. 17. The discharge lamp lighting method according to claim 16, wherein the curvature of the discharge arc is controlled by a time ratio of a period during which the first waveform signal appears in a unit period.