JP4151632B2 - A discharge tube capable of efficient and stable driving - Google Patents

Description

  The present invention relates to a discharge tube, and more particularly to a technique for efficiently and stably driving a discharge tube.

  A discharge lamp having a discharge tube is used as a light source for a projector or the like. Some discharge tubes are driven by a single-phase power source (for example, Patent Document 1) and others are driven by a multi-phase power source (for example, Patent Document 2).

JP-A-6-325735 Japanese Patent Application Laid-Open No. 64-86442

  The above conventional discharge tubes have variations in discharge characteristics, and the discharge efficiency has not been sufficiently improved and the luminance has not been sufficiently stabilized. In addition, there is a problem that light loss occurs due to an electrode or the like disposed on the light transmission path, and the light transmission efficiency is not good.

  Such a problem is not limited to a discharge tube used in a discharge lamp as a light source of a projector, but is a problem common to discharge tubes.

  The present invention has been made in order to solve the above-described conventional problems, and provides a technique capable of improving discharge efficiency, stabilizing luminance, and improving light transmission efficiency in a discharge tube. The purpose is to do.

In order to solve at least a part of the above problems, a discharge tube of the present invention is a discharge tube driven by a multiphase drive circuit,
A discharge vessel having a discharge space therein;
A plurality of electrodes fixed to the discharge vessel and corresponding to each phase of the multiphase drive circuit,
Each tip of the plurality of electrodes protrudes into the discharge space and is directed to one predetermined coupling point,
All of the plurality of electrodes are located on one side with respect to a predetermined plane including the predetermined coupling point.

  In this discharge tube, since the tips of the plurality of electrodes are directed to one predetermined coupling point, light energy due to discharge between the electrodes can be concentrated, and the discharge efficiency can be improved. In addition, since all of the plurality of electrodes are located on one side with respect to a predetermined plane including a predetermined coupling point, light loss due to the electrodes can be suppressed, and light transmission efficiency can be improved. . Furthermore, since it is driven by a multiphase drive circuit, variations in discharge can be alleviated and luminance can be stabilized.

In the discharge tube, the plurality of electrodes include a tip including a tip protruding into the discharge space, and a body portion formed to form a predetermined angle with the tip.
The body portions of the plurality of electrodes may be arranged so as to be substantially parallel to each other.

  In this way, obstacles that block light in the light transmission path can be reduced, and light loss can be particularly suppressed.

In the discharge tube, the multiphase drive circuit is a three-phase drive circuit,
It is good also as discharging between several sets of said electrodes simultaneously.

  In this way, the distance between the electrodes can be reduced, the discharge start voltage can be reduced, the discharge start time can be shortened, and a light source closer to a point light source can be formed. In addition, power consumption can be reduced. Furthermore, when the conventional single-phase discharge tube is applied to a display device such as a projector, the light source becomes a sine wave AC light source, and flicker phenomenon occurs due to interference between the discharge frequency and the display device drive frequency. In the above discharge tube, a light source state close to a direct current light source can be generated, interference between the discharge frequency and the display device driving frequency can be reduced, and the occurrence of flicker phenomenon can be suppressed. Further, driving by oversampling technology is not necessary, and a display device at a low frequency can be realized.

  Note that the present invention can be realized in various forms, for example, in the form of a discharge tube, a discharge lamp having a discharge tube, a projector having a discharge lamp, an illumination device having a discharge lamp, and the like. Can do.

Next, embodiments of the present invention will be described in the following order based on examples.
A. First embodiment:
B. Second embodiment:
C. Variation:

A. First embodiment:
FIG. 1 is an explanatory view schematically showing the configuration of a discharge lamp having a discharge tube as a first embodiment of the present invention. The discharge lamp 100 includes a discharge tube 200, a reflection case 300, a drive circuit 400, and a power supply line 500 that connects the discharge tube 200 and the drive circuit 400. The discharge tube 200 is fixed to the base portion 320 of the reflection case 300 so that the tip thereof protrudes into the hollow portion 310 of the reflection case 300. For example, nitrogen gas is sealed in the hollow portion 310 of the reflection case 300.

  The discharge lamp 100 is used, for example, as a light source for a projector, a headlight for a vehicle, a lighting device, or the like.

  FIG. 2 is an explanatory view showing a detailed configuration of the discharge tube of the first embodiment. 2A shows a transverse section of the discharge tube 200, and FIG. 2B shows a bb section of FIG. 2A. The discharge tube 200 includes a discharge vessel 210 having a discharge space 212 therein. The discharge vessel 210 is formed in a substantially cylindrical shape using, for example, quartz glass. The discharge space 212 is a substantially spheroidal space formed inside one end of the discharge vessel 210. In the discharge space 212, for example, mercury and argon gas are sealed.

  Inside the discharge vessel 210, three electrodes 220, three metal foils 230, and three external leads 240 are housed. The electrode 220 and the external lead 240 are formed using, for example, tungsten, and the metal foil 230 is formed using, for example, molybdenum. One electrode 220, one metal foil 230, and one external lead 240 are connected to each other in this order. Each of the three external leads 240 is connected to each of the three power supply lines 500 (FIG. 1).

  The electrode 220 has a rod-like shape, and one end (hereinafter referred to as “discharge end”) projects into the discharge space 212 of the discharge vessel 210. In this embodiment, the electrode 220 is composed of a tip portion 222 including a discharge end and a body portion 224 which is the remaining portion, and the tip portion 222 and the body portion 224 have a predetermined angle. It has become. As shown in FIG. 2A, the body portions 224 of the three electrodes 220 are arranged substantially parallel to each other. Further, as shown in FIGS. 2A and 2B, the tip portions 222 of the three electrodes 220 are all arranged so as to point to one point (hereinafter referred to as “coupling point P”). In the following description, the three electrodes 220 are also referred to as “A pole”, “B pole”, and “C pole”, respectively.

  FIG. 3 is a conceptual diagram of electrodes in the discharge tube of the first embodiment. The three electrodes 220 (A pole, B pole, C pole) of the discharge tube 200 are arranged as shown in FIG. This corresponds to a delta electric circuit in which each of the three electrodes 220 is connected to the other two electrodes 220 via a capacitor C as shown in FIG.

  FIG. 4 is an explanatory diagram showing the configuration of the drive circuit in the first embodiment. The drive circuit 400 is a three-phase drive circuit for driving the discharge tube 200 (shown surrounded by a broken line in FIG. 4). In FIG. 4, the internal configuration of the discharge tube 200 is omitted. The drive circuit 400 includes a DC power source E and six switches (Sa1, Sa2, Sb1, Sb2, Sc1, Sc2). In FIG. 4, for convenience of illustration, the power source E is illustrated in two places. The power source E is connected to the A pole via the switch Sa1, and is also connected to the B pole via the switch Sb1 and the C pole via the switch Sc1. Each switch receives a drive signal transmitted from a drive signal circuit (not shown). The drive signal input to the switch Sa1 is referred to as “A + drive signal”. Similarly, the drive signals input to the switches Sa2, Sb1, Sb2, Sc1, and Sc2 are referred to as “A− drive signal” and “B +”, respectively. These are called “drive signal”, “B− drive signal”, “C + drive signal”, and “C− drive signal”, respectively.

  FIG. 5 is a timing chart when driving the discharge lamp using the discharge tube of the first embodiment. Moreover, FIG. 6 is explanatory drawing which shows notionally the mode of the discharge current formed between each electrode in each timing. The symbols T1, T2,... Shown at the top of FIG. 5 represent the periods in the timing chart, and correspond to the symbols T1, T2,.

  For example, in the period T1 in the timing chart of FIG. 5, three of the A + drive signal, the B− drive signal, and the C− drive signal are at the H level, and three of the A− drive signal, the B + drive signal, and the C + drive signal are at the L level. It becomes. At this time, in the circuit shown in FIG. 4, the three switches Sa1, Sb2, and Sc2 are turned on, and the remaining three switches Sa2, Sb1, and Sc1 are turned off. Therefore, an electrical path from the power supply E to the ground of the B pole and the C pole through the A pole is opened. At this time, a discharge current is generated from the A pole toward the B pole and the C pole as shown in the figure labeled T1 in FIG. 6, and in the directions indicated by IA +, IB−, and IC− in FIG. Current flows. Note that in the period T1, both ends of the B pole-A pole / C pole and both ends of the C pole-A pole / B pole are not involved in the operation (discharge) and are in a non-conductive state.

  Similarly, for example, in the period T2, three of the A− drive signal, the B + drive signal, and the C− drive signal are at the H level, and three of the A + drive signal, the B− drive signal, and the C + drive signal are at the L level (FIG. 5). ). Therefore, in FIG. 4, the switches Sa2, Sb1, and Sc2 are turned on, and the remaining three switches Sa1, Sb2, and SC1 are turned off. Accordingly, a discharge current is generated from the B pole toward the A pole and the C pole as shown in the figure labeled T2 in FIG. 6, and the current flows in the directions indicated by IA−, IB +, and IC− in FIG. Flows. The same applies to the periods T3 to T6.

  Thus, in the discharge tube 200 of the first embodiment, the on / off state of each switch is switched by the drive signal, and the discharge between the electrodes 220 is performed while repeating the six states shown in FIG. At this time, as can be seen from FIG. 6, the discharge between the two sets of electrodes 220 is simultaneously performed in all the periods (T1 to T6). For example, in the period T1, discharge is performed between two sets of electrodes, between the A pole and the B pole and between the A pole and the C pole.

  Here, in the discharge tube 200 of the present embodiment, as described above with reference to FIG. 2, the tip portions 222 of the three electrodes 220 are all arranged so as to be directed to the coupling point P. Therefore, the light energy by the discharge between the electrodes 220 can be concentrated, and the discharge efficiency can be improved.

  Further, in the discharge tube 200 of the present embodiment, the three electrodes 220 are arranged on one side with respect to the discharge space 212 of the discharge vessel 210 (FIG. 2A). Therefore, light loss due to light generated by the discharge between the electrodes 220 being blocked by the electrode 220 or the like can be suppressed, and light transmission efficiency can be improved. In particular, in the discharge tube 200 of the present embodiment, since the body portions 224 of the electrodes 220 are arranged substantially in parallel with each other, the number of obstacles that block light in the light transmission path can be reduced, and light loss is particularly suppressed. can do.

  Further, in the discharge tube 200 of the present embodiment, the discharge is performed while repeating the state shown in FIG. 6 between the three electrodes 220, so that the variation in discharge can be alleviated and the luminance can be stabilized. In addition, since the energy of discharge is distributed to the three electrodes 220, the life of the electrodes 220 can be extended.

  Further, in the discharge tube 200 of the present embodiment, the discharge between the two sets of electrodes 220 is simultaneously performed by being driven by the three-phase drive circuit. Therefore, the distance between the electrodes 220 can be reduced accordingly, and the discharge start voltage can be reduced and the time required for the discharge start can be shortened, and a light source closer to a point light source can be formed. In addition, power consumption can be reduced. Furthermore, when the conventional single-phase discharge tube is applied to a display device such as a projector, the light source becomes a sine wave AC light source, and flicker phenomenon occurs due to interference between the discharge frequency and the display device drive frequency. In the discharge tube 200 of the present embodiment, a light source state close to a direct current light source can be generated, interference between the discharge frequency and the display device driving frequency can be reduced, and the occurrence of flicker phenomenon can be suppressed. Further, driving by oversampling technology is not necessary, and a display device at a low frequency can be realized.

B. Second embodiment:
FIG. 7 is a conceptual diagram of electrodes of a discharge tube as a second embodiment of the present invention. Unlike the first embodiment, the discharge tube 200 of the second embodiment is driven by a two-phase drive circuit. Therefore, unlike the first embodiment shown in FIG. 3, the discharge tube 200 according to the second embodiment includes three electrodes 220 including an A pole, a B pole, and a COM pole (common). The three electrodes 220 are arranged as shown in FIG. 7A, which is connected between the A pole and the COM pole and between the B pole and the COM pole shown in FIG. It corresponds to the electric circuit made. In addition, about the structure of the discharge lamp 100 of 2nd Example, and the detailed structure of the discharge tube 200, it is the same as that of 1st Example shown in FIG. 1 and FIG.

  FIG. 8 is an explanatory diagram showing the configuration of the drive circuit in the second embodiment. The drive circuit 400a has a DC power source E and six switches (Sa1, Sa2, Sb1, Sb2, Sab1, Sab2). In FIG. 8, for convenience of illustration, the power source E is illustrated in two places. The power source E is connected to the A pole via the switch Sa1, and is also connected to the B pole via the switch Sb1 and the COM pole (FIG. 7) via the switch Sab2. Each switch receives a drive signal transmitted from a drive signal circuit (not shown). The drive signal input to the switch Sa1 is referred to as “A1 drive signal”. Similarly, the drive signals input to the switches Sa2, Sb1, and Sb2 are referred to as “A2 drive signal”, “B1 drive signal”, “ These are called “B2 drive signals”. Further, the A1 drive signal and the B1 drive signal are input to the switch Sab1 via the OR circuit, and the A2 drive signal and the B2 drive signal are input to the switch Sab2 via the OR circuit.

  FIG. 9 is a timing chart when driving a discharge lamp using the discharge tube of the second embodiment. The symbols T1, T2,... Shown at the top of FIG. 9 represent each period in the timing chart. For example, in the period T1 in the timing chart, the A1 drive signal is at the H level, and three of the A2 drive signal, the B1 drive signal, and the B2 drive signal are at the L level. At this time, in the circuit shown in FIG. 8, the switch Sa1 and the switch Sab1 are turned on, and the remaining four switches Sa2, Sb1, Sb2, and Sab2 are turned off. Therefore, an electric path from the power source E to the ground of the COM pole through the A pole is opened. At this time, a discharge current is generated from the A pole toward the COM pole, and the current flows in the direction indicated by IA1 in FIG. Note that in the period T1, both ends of the B pole and the COM pole are not involved in the operation (discharge) and are in a non-conductive state.

  Similarly, for example, in the period T2, the B1 drive signal is at the H level, and the three of the A1 drive signal, the A2 drive signal, and the B2 drive signal are at the L level (FIG. 9). Therefore, in FIG. 8, the switches Sb1 and Sab1 are turned on, and the remaining switches are turned off. Accordingly, a discharge current is generated from the B pole toward the COM pole, and the current flows in the direction indicated by IB1 in FIG. The same applies to the periods T3 to T4. In the discharge tube 200a of the second embodiment, the on / off state of each switch is switched by the drive signal, and the discharge between the electrodes 220 is performed while repeating the state in the periods T1 to T4.

  In the discharge tube 200a of the second embodiment, as in the first embodiment, the tip portions 222 of the three electrodes 220 are all arranged so as to be directed to the coupling point P. The discharge efficiency can be improved.

  Further, in the discharge tube 200a of the second embodiment, as in the first embodiment, since the three electrodes 220 are arranged on one side with respect to the discharge space 212 of the discharge vessel 210, the light loss is reduced. And the light transmission efficiency can be improved.

  Further, in the discharge tube 200a of the second embodiment, the discharge is performed while switching the electric circuit between the three electrodes 220 according to the drive signal shown in FIG. 9, so that the variation in discharge is reduced as in the first embodiment. Thus, the luminance can be stabilized. In addition, since the energy of discharge is distributed to the three electrodes 220, the life of the electrodes 220 can be extended.

C. Variation:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

C-1. Modification 1:
The configurations, materials, and the like of the discharge lamp 100 and the discharge tube 200 in the above embodiments are merely examples, and other configurations, materials, and the like can be employed. For example, in each of the above-described embodiments, the tip portion 222 and the body portion 224 of the electrode 220 are formed to have a predetermined angle. The portion 222 and the body portion 224 may be formed in a straight shape along the same axis. In each of the above embodiments, the body portions 224 of the three electrodes 220 are arranged substantially parallel to each other. However, it may be arranged so as to be located on one side. If the body portions 224 of the three electrodes 220 are arranged substantially parallel to each other as in the above-described embodiments, the number of obstacles that block light in the light transmission path can be reduced. It is preferable because loss can be particularly suppressed.

C-2. Modification 2:
In the first embodiment, the arrangement of the electrode 220 of the discharge tube 200 is a delta type. However, the arrangement of the electrode 220 of the discharge tube 200 may be a star type. At this time, in addition to the three electrodes (A pole, B pole, C pole) shown in FIG. 3, a COM pole (common) is provided, and discharge is performed between the A pole, the B pole, the C pole, and the COM pole. It becomes the composition like this.

C-3. Modification 3:
In each of the above-described embodiments, the discharge tube 200 is described as being driven by a three-phase drive circuit or a two-phase drive circuit. However, the discharge tube 200 may be driven by a multiphase drive circuit having four or more phases. Further, the number of electrodes 220 of the discharge tube 200 can be arbitrarily set depending on the drive circuit used.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows schematically the structure of the discharge lamp which has a discharge tube as 1st Example of this invention. Explanatory drawing which shows the detailed structure of the discharge tube of 1st Example. The conceptual diagram of the electrode in the discharge tube of 1st Example. Explanatory drawing which shows the structure of the drive circuit in 1st Example. The timing chart at the time of driving the discharge lamp using the discharge tube of 1st Example. Explanatory drawing which shows notionally the mode of the discharge current formed between each electrode in each timing. The conceptual diagram of the electrode of the discharge tube as 2nd Example of this invention. Explanatory drawing which shows the structure of the drive circuit in 2nd Example. The timing chart at the time of driving the discharge lamp using the discharge tube of 2nd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Discharge lamp 200 ... Discharge tube 210 ... Discharge vessel 212 ... Discharge space 220 ... Electrode 222 ... Tip part 224 ... Body part 230 ... Metal foil 240 .. External lead 300 ... Reflective case 310 ... Hollow part 320 ... Base part 400 ... Drive circuit

Claims (2)

A discharge tube driven by a multiphase drive circuit,
A discharge vessel having a discharge space therein;
A plurality of electrodes fixed to the discharge vessel and corresponding to each phase of the multiphase drive circuit,
Each tip of the plurality of electrodes protrudes into the discharge space and is directed to one predetermined coupling point,
All of the plurality of electrodes are located on one side with respect to a predetermined plane including the predetermined coupling point ,
Each of the plurality of electrodes has a tip portion including a tip protruding into the discharge space, and a body portion formed so as to form a predetermined angle with the tip portion,
The body portions of the plurality of electrodes are arranged so as to be substantially parallel to each other,
The electrode is a discharge tube in which only a part including the tip of the tip is located in the discharge space . The discharge tube according to claim 1 , wherein
The multi-phase drive circuit is a three-phase drive circuit,
A discharge tube that discharges between a plurality of sets of electrodes simultaneously.

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