JP2006179414A - High-pressure discharge lamp lighting device and lighting method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting device with a long life of its electrode, capable of restraining generation of flicker. <P>SOLUTION: A down converter 12 and a full-bridge circuit 13 generate an alternating current wave form turning a current value at the start of a half-cycle into a value of a steady current. A control part 11 generates a current waveform including a period in which a value of a current supplied to the lamp 30 decreases from the value of the steady current to a first current value, a period in which the value of the current supplied to the lamp increases from the value of the steady current to a second current value larger than the first current value in a form of a quadratic curve, and a period maintaining the value of the second current until the end, as a current wave-form at half cycle. The decreased amount of the energy of the current wave-form at the half-cycle against a standard energy at the first period in which the value of the current supplied to the lamp is lower than the value of the steady current is made equivalent with the increased amount of the energy against the standard energy at the second period in which the value of the current supplied to the lamp is higher than the value of the steady current. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lighting device and a lighting method for a high-pressure discharge lamp, in particular, an AC lighting type high-pressure discharge lamp.

  High-pressure discharge lamps typified by xenon lamps, high-pressure mercury lamps, metal halide lamps, and the like are widely used as light sources for projection devices typified by projectors because of their high brightness and good color rendering.

  In this type of high-pressure discharge lamp, for example, mercury (Hg) and an inert gas necessary for maintaining a small amount of halogen gas to maintain discharge light emission are pre-enclosed in a bulb, and a glow discharge is induced between the electrodes. Thus, the enclosed mercury is vaporized and plasma discharge is generated in the high-pressure mercury gas. During plasma discharge, a sputtering phenomenon occurs due to mercury ions and electrons, and an electrode material, for example, tungsten atoms (ionized state) is released from both electrodes. If the tungsten atoms thus released adhere to the inner wall of the bulb, the bulb wall becomes black. The halogen cycle prevents blackening of the bulb wall.

  In the halogen cycle, tungsten atoms released from both electrodes (ionized state) are combined with previously encapsulated halogen atoms to form tungsten halide. This tungsten halide floats in the bulb by thermal convection and is separated into tungsten atoms and halogen atoms by being exposed to a high temperature in the vicinity of the electrode. The separated tungsten atoms adhere to the electrode, and thus electrode regeneration is performed. On the other hand, the separated halogen atoms contribute to the formation of tungsten halide again. The repetition of this series of reactions is a halogen cycle.

  In the AC lighting type high-pressure discharge lamp, when the waveform of the current supplied to the electrode is a rectangular waveform whose polarity is switched every half cycle as shown in FIG. The temperature rises smoothly. In this case, the electrode tip portion is in a high temperature state over a wide range, and as a result, the return of the electrode material in the halogen cycle (adhesion of the above-mentioned tungsten atoms to the electrode) is dispersed, and a plurality of protrusions are formed at the electrode tip portion become. When a plurality of protrusions are formed, a phenomenon called arc jump occurs in which the arc moves. This arc jump is one of the causes of flickering. When the distance between the electrodes (arc gap) is wide, the arc jump phenomenon tends to increase.

  As a lighting method of a high-pressure discharge lamp that can suppress the above flicker, there is a lighting method described in Patent Document 1. This lighting method superimposes a current pulse of a predetermined half of the half cycle on the lamp current whose polarity changes every half cycle, so that the current increases rapidly in the last part of the half cycle. is there.

In addition to the above, there is a lighting method described in Patent Document 2. In this lighting method, the average value of current in a half cycle (1/2 cycle) is a, the average value of current in the first half of the half cycle is a1, and the average value of the latter half of the half cycle is 1/4 cycle. When the average value of the current is a2, the condition of a1 <a2 is satisfied.
Japanese National Patent Publication No. 10-501919 JP 2002-110392 A

  However, the conventional lighting method described above has the following problems.

  The volume (capacity) of the electrode of the high-pressure discharge lamp is optimally designed according to the power consumption (wattage), and the amount of energy supplied in a half cycle is limited by the amount of energy supplied by the optimal design. If the upper limit is exceeded, an extra load is applied to the electrode. As a result, the electrode growth and electrode wear in the halogen cycle cannot be balanced, and the life of the electrode is shortened.

  In the lighting method described in Patent Document 1, the occurrence of flicker due to arc jump is suppressed by superimposing a pulse of 5 to 15% of the amount of energy supplied to the lamp every half cycle. However, in this lighting method, the amount of energy supplied in a half cycle may exceed the upper limit of the amount of energy supplied that is limited by the optimum design. For this reason, the problem that the lifetime of an electrode becomes short arises.

  In the lighting method described in Patent Literature 2, the average value of the current value in the second half of the half cycle is made larger than the average value of the current value in the first half, thereby suppressing the occurrence of flicker due to arc jump. However, this lighting method also has a problem in that the life of the electrode is shortened because the amount of energy supplied in a half cycle may exceed the upper limit of the amount of energy that is limited by the optimum design.

  In addition, image projection apparatuses such as projectors are increasingly required to have high brightness year by year, and high output lamps have been used as light sources. Since such a high power lamp consumes a lot of electrodes, it is difficult to sufficiently reduce the consumption of the electrodes in the lighting methods described in Patent Documents 1 and 2 described above. For this reason, in order to provide a long-life lamp that is less prone to flicker in the long term, it is necessary to take further measures against electrode consumption.

  An object of the present invention is to provide a lighting device and a lighting method that can solve the above-described problems and can suppress the occurrence of flicker due to arc jump and that has a long electrode life.

  In order to achieve the above object, the present invention generates an alternating current waveform in which a current value at the beginning of a half cycle is a steady current value, and supplies a current to a high-pressure discharge lamp based on the generated alternating current waveform. As a current waveform in the current supply unit and the half cycle, a period in which the supply current value to the high pressure discharge lamp decreases from the steady current value to the first current value, and the gradient of the increasing current value gradually increases. In accordance with a curve (specifically, a quadratic curve), a period in which the supply current value increases to a second current value larger than the steady-state current value, and the second current value at the end of the half cycle And a control unit that causes the current supply unit to generate a current waveform including a period of time until the current supply unit holds. The current waveform in the half cycle is based on the energy when the steady current is supplied to the high-pressure discharge lamp, and is the standard in the first period in which the supply current value is lower than the steady current value. The amount of energy decrease relative to energy is the same as the amount of energy increase relative to the reference energy in the second period in which the supply current value exceeds the steady current value.

  According to the above invention, the temperature of the electrode tip in the arc tube of the high-pressure discharge lamp can be reduced by once decreasing the supply current value from the steady current value to the first current value at the beginning of the half cycle. . This makes it possible to increase the temperature gradient (temperature gradient at the electrode tip) between the tip of the electrode and its adjacent portion immediately after the polarity is switched (start of the half cycle).

  In addition, after the supply current value is lowered to the first current value and then increased to the second current value in a quadratic curve toward the end of the half cycle, a local temperature rise at the electrode tip occurs. . Thereby, since the electrode tip temperature can be greatly increased immediately before the polarity is switched (end of the half cycle), the temperature gradient of the electrode tip can be increased. When the supply current value is increased linearly, the local temperature rise at the electrode tip hardly occurs, and the electrode tip temperature rises smoothly. In this case, it is difficult to increase the temperature gradient at the tip of the electrode.

  Moreover, according to said invention, since the energy decrease amount in the 1st period and the energy increase amount in the 2nd period are made the same, the optimal design according to power consumption (wattage) is made. In the electrode of the high-pressure discharge lamp, the amount of energy supplied in a half cycle does not exceed the upper limit of the amount of energy supplied limited by the optimum design. Therefore, it is possible to balance electrode growth and electrode wear in the halogen cycle without applying an extra load to the electrode.

  According to the present invention, the electrode tip temperature is reduced immediately after the polarity switching (start of the half cycle), and the electrode tip temperature is greatly increased immediately before the polarity switching (end of the half cycle). The temperature gradient at the tip can be increased. Thereby, generation | occurrence | production of an arc jump can be reduced and generation | occurrence | production of a flicker can be suppressed.

  In addition, according to the present invention, the amount of energy supplied in a half cycle does not exceed the upper limit of the amount of energy supplied that is limited by the optimum design, so that no extra load is applied to the electrode. The electrode growth and electrode wear in the halogen cycle can be balanced. Therefore, the distance between the electrodes suitable for discharge can be maintained over a long period of time, and a lamp with a long life and less flicker can be realized.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a book diagram showing a schematic configuration of a lighting device for a high-pressure discharge lamp according to an embodiment of the present invention. The lighting device 10 is based on signals from a down converter 12 connected to a DC power supply 20, a full bridge circuit 13, an igniter 14 connected to a lamp 30, and an external device (for example, a projector). And a control unit 11 for controlling the entire operation. The lamp 30 is an AC lighting type high-pressure discharge lamp in which electrode regeneration is performed by the halogen cycle described above, and is, for example, a xenon lamp, a high-pressure mercury lamp, a metal halide lamp, or the like.

  The control unit 11 detects the current and voltage supplied from the DSP (digital signal processor), the D / A conversion unit that converts the digital signal from the DSP into an analog signal, and the DC power source 20, And a control interface for creating a waveform for controlling the down converter 12 based on an analog signal from the A converter.

The down converter 12 converts the input voltage into a voltage having a necessary magnitude and generates a waveform based on the signal waveform from the control unit 11. FIG. 2 shows an example of the output waveform of the down converter 12. In the output waveform shown in FIG. 2, after gradually decreasing from the steady current value I ₀ to the current value I _a (<I ₀ ) in the half cycle (T / 2), the current value I in _a quadratic curve (parabolic shape). _It increases to _b (> I ₀ ), and the current value I _b is held over the period t.

  The full bridge circuit 13 converts the output waveform of the down converter 12 into a waveform whose polarity is switched every half cycle. FIG. 3 shows an example of the output waveform of the full bridge circuit 13. In the output waveform shown in FIG. 3, the polarity is switched every half cycle (T / 2). The output of the full bridge circuit 13 is supplied to the lamp 30.

  The igniter 14 is inserted in series with the output of the full bridge circuit 13 (so-called internal trigger method), and generates a high voltage (pulse voltage necessary for dielectric breakdown) required at the start of lighting of the lamp 30.

  Next, the lighting operation in the lighting device of the present embodiment will be described.

A current based on the output waveform of the full bridge circuit 13 shown in FIG. In this current supply operation, values such as the current value I _a , current value I _b , period t, and energy increase / decrease amount based on the steady current in the output waveform of the full bridge circuit 13 make the halogen cycle work more effective. Is set to a suitable value such as

  FIG. 4 shows detailed conditions of the output waveform shown in FIG. In FIG. 4, the solid line indicates the output waveform (supply current waveform) shown in FIG. 3, and the broken line indicates a rectangular waveform (reference waveform) in which positive and negative are switched at a steady current value every half cycle (T / 2).

The difference between the current value I _a and the steady current value I ₀ is
I ₀ −I _a = I ₀ × 0.01 to I ₀ × 0.15
It is set in the range. The period t1 until the current value gradually decreases from the steady current value I ₀ to the current value I _a and again becomes the steady current value I ₀ is set in a range of 1/100 sec to 1/1000 sec. The period t during which the current value _Ib is held is set in a range of 1/1000 sec to 1/10000 sec.

Supply current waveform in the first period t1 of the half period, is below the current value is constant current value I _0, subsequent, in a period t2 to the end of the half cycle, the current value is constant current value I ₀ Is over. In the supply current waveform, the area S1 of the region surrounded by the supply current waveform and the reference waveform in the period t1 is the same as the area S2 of the region surrounded by the supply current waveform and the reference waveform in the period t2. It is set to be. That is, the supply current waveform is based on the supply energy when a steady current is supplied to the lamp 30 over a half cycle, and the amount of energy decrease (area S1) in the period t1 and the amount of energy amplification (area S2) in the period t2. Is the same. The amount of energy reduction (area S1) is in the range of 1% to 15% of the total energy amount supplied to the lamp 30 in the half cycle (same as the energy amount when the steady current is supplied to the lamp 30 over the half cycle). It is desirable to set.

Current I _b is possible to set the difference between the current value I _a and the steady-state current value I _0, the period t, the period t1, increase or decrease the amount of energy each value of (the area S1 = area S2) in the above range It is set within the range.

Under the control of the control unit 11, a current based on the output waveform of FIG. 4 set as described above is supplied from the current supply unit including the down converter 12 and the full bridge circuit 13 to the flump 30. In the current supply control by the control unit 11, in the half cycle (T / 2), first, the current supplied to the lamp 30 is gradually decreased from the steady current (I ₀ ) to the current value I _a . Thereafter, the supply current quadratic curve (parabolic) to increase until the current value I _b. Then, the supply current is held at the current value _Ib for a period t.

  According to the current supply control based on the output waveform of FIG. 4 by the control unit 11 described above, the halogen cycle works more effectively by the interaction of the following points (1) to (3). The electrode tip shape can be maintained over a long period of time, and the life of the electrode can be extended.

(1) The lamp supply current is reduced from the steady current value I ₀ to the current value I _a :
At the beginning of the half cycle, the temperature of the electrode tip in the arc tube of the lamp 30 can be reduced by once decreasing the value of the supply current. This makes it possible to increase the temperature gradient (temperature gradient at the electrode tip) between the tip of the electrode and its adjacent portion immediately after the polarity is switched (start of the half cycle).

(2) the lamp supply current quadratic curve (parabolic) to a point increased to a current value I _b:
When the temperature is increased linearly, the local temperature rise at the electrode tip hardly occurs, and the electrode tip temperature rises smoothly. In this case, it is difficult to increase the temperature gradient at the tip of the electrode. On the other hand, according to a quadratic curve (parabolic) control, a local temperature rise at the tip of the electrode occurs. Therefore, the electrode tip temperature can be greatly increased immediately before the polarity is switched (end of the half cycle), and the temperature gradient of the electrode tip can be increased. Due to the interaction between the point (1) and the point (2), the temperature gradient of the electrode tip is further increased.

(3) The point where the decrease energy amount in the period t1 and the increase energy amount in the period t2 are the same:
The volume (capacity) of the electrode of the high-pressure discharge lamp is optimally designed according to the power consumption (wattage). For this reason, when the amount of energy supplied in a half cycle exceeds the upper limit of the energy supply amount limited by the optimum design, an extra load is applied to the electrode, and the life of the electrode is shortened. By making the decreased energy amount in the period t1 and the increased energy amount in the period t2 the same, the energy amount supplied in the half cycle is limited by the energy amount when the steady current is supplied over the half cycle (limited by the optimum design). The same as the amount of energy). In this case, since no extra load is applied to the electrode, the electrode growth and electrode wear in the halogen cycle are balanced, and the discharge interval can be maintained over a long period of time. Therefore, it is possible to realize a long-life lamp with less flicker.

Further, in the current supply control by the control unit 11 described above, the length of the period t1 (period in which the supply current is lower than the steady current value I ₀ ), the amount of reduced energy in the period t1, and the length of the period t Has a suitable range in which the effects of the above points (1) to (3) can be made larger.

  More specifically, if the period t1 is longer than “1/100 sec”, the temperature of the lamp electrode itself is greatly lowered, and the function of the halogen cycle is hindered. In some cases, the flicker and the lamp bulb are blackened. Cause the phenomenon. Conversely, if the period t1 is shorter than “1/1000 sec”, it is difficult to reduce the electrode tip temperature. Therefore, the period t1 needs to be in the range of “1/100 sec to 1/1000 sec”.

Further, when the amount of decrease energy in the period t1 exceeds “15%” of the total energy amount supplied to the lamp 30 (or the difference between the current value I _a and the steady current value I ₀ is the current value I ₀ ). If it exceeds “15%”), the temperature of the lamp electrode itself will be too low, which will impede the function of the halogen cycle. On the other hand, when the decrease energy amount is less than “1%” of the total energy amount (or the difference between the current value I _a and the steady current value I ₀ is less than “1%” of the current value I ₀ ), the electrode tip temperature It will not contribute to the reduction of. For this reason, the decrease energy amount in the period t1 is in the range of “1% to 15%” of the total energy amount (or the difference between the current value I _a and the steady current value I ₀ is “1% of the current value I _0. -15% "range).

  Further, when the period t is longer than “1/1000 sec”, the amount of consumption of the electrode increases, and as a result, the amount of consumption of the electrode exceeds the electrode growth by the halogen cycle. On the contrary, when the period t is shorter than “1/10000 sec”, it does not contribute to the rise of the electrode tip temperature. For this reason, the period t needs to be in the range of “1/1000 sec to 1/10000 sec”.

  From the above knowledge, in the present embodiment, the period t1 is in the range of “1/100 sec to 1/1000 sec”, the amount of energy decreased in the period t1 is “1% to 15%” of the total energy amount, and the period t is “ A suitable condition of “1/1000 sec to 1/10000 sec” has been found, and by adopting this condition, the effects of the above-mentioned points (1) to (3) are made larger. Specifically, when the current is supplied under these preferable conditions, the lamp life is about 1.5 to 2 times longer than when the current is supplied based on the waveform shown in FIG. It has been. Note that the conditions of the period t1, the period t, and the amount of reduced energy may be appropriately combined.

  The lighting device of the present embodiment described above is an example of the present invention, and the configuration and operation thereof may be changed in any way as long as they have the points (1) to (3) described above.

  For example, instead of the output waveform of FIG. 4, another output waveform that can realize the points (1) to (3) is adopted as the output waveform of the current supply unit including the down converter 12 and the full bridge circuit 13. Also good. FIG. 5 shows an example of another output waveform. In FIG. 5, the solid line indicates the output waveform (supply current waveform) of the current supply unit, and the broken line indicates a rectangular waveform (reference waveform) in which positive and negative are switched at a steady current value every half cycle (T / 2).

In the supply current waveform shown in FIG. 5, in a half cycle (T / 2), after suddenly decreasing from the steady-state current value I ₀ to the current value I _c (<I ₀ ), the current value has a quadratic curve (parabolic). The current value I _d increases to I _d (> I ₀ ) and is held for the period t. The conditions are the same as those of the output waveform shown in FIG. 4 except that the current value I _c rapidly decreases from the steady current value I ₀ to the current value I _c (<I ₀ ). That is, the difference between the current value I _c and the steady current value I ₀ is
I ₀ −I _c = I ₀ × 0.01 to I ₀ × 0.15
It is set in the range. The period t1 is set in a range of 1/100 sec to 1/1000 sec, and the period t is set in a range of 1/1000 sec to 1/10000 sec. The amount of energy decrease (area S3) in the period t1 is the same as the amount of energy increase (area S4) in the period t2, and the amount of energy decrease (area S3) is the total energy amount supplied to the lamp 30 in a half cycle. Is set in the range of 1% to 15%.

  Even with the supply current waveform set as described above, the same operation and effect as the supply current waveform shown in FIG.

  Further, in the configuration shown in FIG. 1, an internal trigger system in which an igniter 14 is inserted in series with the output of the full bridge circuit 13 is adopted, but the output of the igniter 14 is connected in parallel to the electrode of the lamp 30. An external trigger method may be adopted.

  In addition to the light source of a projection device represented by a projector, it can be applied to a medical lamp or the like.

It is a book figure which shows schematic structure of the lighting device of the high pressure discharge lamp which is one Embodiment of this invention. It is a wave form diagram which shows an example of the output waveform of the down converter shown in FIG. It is a wave form diagram which shows an example of the output waveform of the full bridge circuit shown in FIG. It is a figure for demonstrating the detailed conditions of the output waveform shown in FIG. It is a wave form diagram which shows an example of the other output waveform of the full bridge circuit shown in FIG. It is a wave form diagram which shows an example of the alternating current waveform supplied to the conventional high voltage | pressure discharge lamp of an alternating current lighting system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Lighting device 20 DC power supply 30 Lamp 11 Control part 12 Down converter 13 Full bridge circuit 14 Igniter

Claims (10)

A current supply unit that generates an alternating current waveform in which the current value at the beginning of the half cycle is a steady current value, and supplies current to the high-pressure discharge lamp based on the generated alternating current waveform;
As a current waveform in the half cycle, according to a period in which the supply current value to the high pressure discharge lamp decreases from the steady current value to the first current value, and a curve in which the gradient of the increasing current value gradually increases. A current waveform including a period in which the supply current value increases to a second current value larger than the steady current value and a period in which the second current value is held until the end of the half cycle is supplied to the current supply unit. A control unit to generate,
The current waveform in the half cycle is based on the energy when the steady current is supplied to the high-pressure discharge lamp, and is the standard in the first period in which the supply current value is lower than the steady current value. The amount of decrease in energy relative to energy is the same as the amount of increase in energy relative to the reference energy in the second period in which the supply current value exceeds the value of the steady current. High pressure discharge lamp lighting device.   2. The lighting device for a high-pressure discharge lamp according to claim 1, wherein a period for holding the second current value is in a range of 1/1000 second to 1/10000 second.   The lighting device for a high-pressure discharge lamp according to claim 1 or 2, wherein the first period is in a range of 1/100 second to 1/1000 second.   The amount of energy reduction is in a range of 1% to 15% of total energy when the steady current is supplied to the high-pressure discharge lamp over the half cycle. High pressure discharge lamp lighting device.   4. The high-pressure discharge lamp according to claim 1, wherein a difference between the first current value and the steady current value is in a range of 1% to 15% of the steady current value. 5. Lighting device. Supplying an alternating current to the high pressure discharge lamp in which the current value at the beginning of the half cycle is a steady current value;
In the half cycle, after the supply current value to the high-pressure discharge lamp is reduced from the steady-state current value to the first current value, the supply current value follows a curve in which the gradient of the increasing current value gradually increases. Increasing to a second current value greater than the steady-state current value and holding the second current value until the end of the half cycle;
Based on the energy when the steady current is supplied to the high-pressure discharge lamp as a reference, the amount of decrease in energy relative to the reference energy in the first period in which the supply current value is lower than the steady current value, A method of lighting a high-pressure discharge lamp, comprising the step of making the amount of increase in energy relative to the reference energy in a second period in which the supply current value exceeds the steady-state current value. .   The lighting method of the high-pressure discharge lamp according to claim 6, wherein the period for holding the second current value is in a range of 1/1000 second to 1/10000 second.   The lighting method of the high pressure discharge lamp according to claim 6 or 7, wherein the first period is in a range of 1/100 second to 1/1000 second.   The lighting of the high-pressure discharge lamp according to any one of claims 6 to 8, wherein the amount of decrease in the energy is in the range of 1% to 15% of the total energy when the steady current is supplied over the half cycle. Method.   The lighting of the high pressure discharge lamp according to any one of claims 6 to 8, wherein a difference between the first current value and the steady current value is in a range of 1% to 15% of the steady current value. Method.

Images