JP2015220058A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting device capable of suppressing flicker of light output from a discharge lamp as compared with a conventional one.SOLUTION: This discharge lamp lighting device includes a power feeding part for feeding an AC current to a discharge lamp in which a pair of electrodes are disposed face to face in a discharge container, a power control part for outputting a signal relating to a control power value to the power feeding part, and a pulse generating part for outputting a pulse wave to the power feeding part. The power feeding part is formed so as to convert a DC voltage supplied is to an AC current corresponding to the frequency of the pulse wave and the control power value and to supply it to the discharge lamp, the pulse generating part is formed so as to repeat a cycle in which after outputting a first pulse wave over a first period, a second pulse wave having a lower frequency than the first pulse wave is output, and the power control part performs control for varying the control power value so as to offset the change of light intensity during polarity reversal of the AC current in a specific period within the half period of the first pulse wave.

Description

  The present invention relates to a discharge lamp lighting device preferably used for a light source such as a projector.

  A discharge lamp with a high mercury vapor pressure is used as a light source of the projector apparatus. Such a high-pressure mercury lamp can obtain light in the visible wavelength region with high output by increasing the mercury vapor pressure.

  The discharge lamp has a substantially spherical light emitting portion formed by a discharge vessel, and a pair of electrodes are arranged in the light emitting portion so as to face each other at an extremely small interval of, for example, 2 mm or less.

  When such a discharge lamp is lit for a long time in the same state, a plurality of minute protrusions may be formed at a high temperature, or minute irregularities may be generated on the tip surface portion of the electrode. These micro-protrusions and irregularities are formed by agglomeration of the compound formed by melting the material constituting the electrode (for example, tungsten) and combining with the gas sealed in the light emitting part. The shape of the surface part of the is changed. Along with this, the starting point of the arc moves, the discharge position becomes unstable, and there is a problem that flickering of projection light called so-called flicker occurs.

  In order to solve such a problem, the following Patent Document 1 supplies a current of a pulse wave P1 having a predetermined frequency (fundamental frequency) to the discharge lamp and a current of a pulse wave P2 having a frequency lower than the fundamental frequency. A discharge lamp lighting system that is intermittently or periodically inserted into the pulse wave of the fundamental frequency is disclosed (see FIG. 9).

  By setting the frequency of the pulse wave to a low frequency, the period during which one electrode is fixed to the anode and the other electrode is fixed to the cathode becomes longer. As a result, the degree of heating of the electrode is increased, and heat can be transmitted not only to the tip of the electrode but also to a location away from the tip. Therefore, while a low-frequency pulse wave is applied, heat is also transmitted to a location away from the tip of the electrode, and the minute protrusions and irregularities generated at the location can be melted and evaporated. Thereby, protrusions and irregularities other than the electrode tip that may adversely affect can be eliminated, and the bright spot of the arc can be stabilized.

JP 2006-59790 A

  When the discharge lamp is turned on by the method described in the above-mentioned Patent Document 1 by the diligent research of the present inventors, the lighting period based on the pulse wave P1 of the fundamental frequency (period T1 in FIG. 9) is lower than that. It has been found that there is a phenomenon that a difference occurs in the light intensity of the discharge lamp in the lighting period (period T2 in FIG. 9) based on the frequency pulse wave P2. The reason why such a phenomenon occurs is considered to be as follows.

  In the period T1, since the current is supplied to the discharge lamp based on the high-frequency pulse wave P1, the polarity inversion of the supply current frequently occurs. Since the current value instantaneously becomes zero at the timing when the polarity of the supply current is reversed, the output of the projection light instantaneously decreases at this timing (dip phenomenon). In contrast, in the period T2, current is supplied to the discharge lamp based on the low-frequency pulse wave P2, and the polarity of the supply current hardly reverses, so that the output of the projection light hardly decreases. For this reason, in period T1, it is thought that light intensity falls rather than period T2 by the instantaneous fall of the projection light resulting from the difference in polarity reversal.

  FIG. 10 is an example of a graph showing a change in the light intensity of the projection light in accordance with the lamp current waveform shown in FIG. 9 under the above consideration. 10, (a) shows the same lamp current waveform as in FIG. 9, and (b) shows the change in the light intensity of the projection light. In the range shown in FIG. 10B, the state D1 in which the light intensity decreases frequently occurs in the period T1, whereas the state D2 in which the light intensity decreases occurs only once in the period T2. Absent.

  According to FIG. 10, since the dip phenomenon frequently occurs in the period T1, the frequency of the light intensity decreasing instantaneously is high. Since this phenomenon occurs in an extremely short cycle, a phenomenon in which a large number of instantaneous light intensity decreases is not visually recognized, but is visually recognized as a state in which the light intensity is reduced to a certain degree throughout the period T1. On the other hand, since the frequency of occurrence of the dip phenomenon is extremely low in the period T2, compared to the period T1, there is almost no decrease in light intensity over the entire period T2.

  The discharge lamp is lit and driven on the basis of the pulse wave P1 having the fundamental frequency for many periods, and is lit and driven on the basis of the pulse wave P2 having the low frequency intermittently or periodically. In other words, during driving, the period corresponding to the period T1 is long, and the period corresponding to the period T2 is inserted intermittently or periodically. As a result, at the timing when the low-frequency pulse wave P2 is inserted, it is visually recognized that the light intensity instantaneously rises, which is considered to appear as the light intensity difference. In particular, when the low-frequency pulse wave P2 is periodically inserted, it is considered that the light intensity is periodically increased, thereby causing a problem that the projected light flickers.

  Further, when the discharge lamp is driven by the above driving method, the above phenomenon that the light intensity in the period T2 becomes higher than the light intensity in the period T1 does not necessarily occur. Depending on the specifications of the power supply device and the program, a phenomenon may occur in which the light intensity in the period T2 is lower than the light intensity in the period T1. This is considered to be caused by an overshoot when driving with an alternating current.

  FIG. 11 schematically illustrates an example of a current waveform in the period T1. As described above, in the period T1, the polarity of the supply current is inverted at a high frequency. At the timing of reversing from negative polarity to positive polarity, it is necessary to instantaneously raise the current value in a short time, but immediately before reaching the target value (steady value), the current value is instantaneously higher than the steady value. After that, it decreases slightly to realize the steady value (reference numeral Y1 in FIG. 11). The reverse phenomenon also occurs at the timing of reversing from positive polarity to negative polarity (reference symbol Y2 in FIG. 11). Such an overshoot is a phenomenon that occurs because the polarity is reversed in a very short time, and its magnitude depends on the configuration of the power supply device and the program.

  When overshoot (Y1, Y2) is taken into consideration, a current larger than the intended steady-state value is actually supplied to the lamp, so that the light intensity slightly increases at this moment. The period T1 has a very large number of times of polarity reversal compared to the period T2. For this reason, in the period T1, the frequency at which a current larger than the target steady value is supplied to the lamp is much higher than in the period T2. As described above, such a phenomenon that the amount of current increases occurs in a very short time, and therefore, an instantaneous increase in light intensity due to this phenomenon is not visually recognized. However, since the average amount of current supplied over the entire period T1 is larger than the average amount of current supplied over the entire period T2, the light intensity in the period T1 is higher than the light intensity in the period T2. Will lead to being. In other words, when such a phenomenon occurs, when a low-frequency pulse wave is periodically inserted, the light intensity periodically decreases, which may cause a problem that the projected light flickers. .

  As described above, when the discharge lamp is driven by the method described in Patent Document 1, the light intensity is different between the period T1 and the period T2, and may be visually recognized as flicker. In addition, depending on the configuration of the power supply device and the program, the possibility that the light intensity increases may decrease during the period T2 inserted intermittently or periodically.

  In view of the above problems, an object of the present invention is to provide a lighting device that can suppress flickering (flicker) of light output from a discharge lamp.

The discharge lamp lighting device of the present invention is
A power feeding unit for supplying an alternating current to a discharge lamp in which a pair of electrodes are arranged to face each other in a discharge vessel in which a predetermined gas is sealed;
A power control unit that outputs a signal related to a control power value to the power supply unit;
A pulse generation unit that outputs a pulse wave to the power supply unit.

And the said electric power feeding part is the structure which converts the supplied DC voltage into the alternating current according to the frequency of the said pulse wave, and the said control electric power value, and supplies it to the said discharge lamp,
The pulse generator is configured to repeat a cycle of outputting a first pulse wave over a first period and then outputting a second pulse wave having a frequency lower than that of the first pulse wave,
The power control unit performs control to vary the control power value in a direction that cancels a change in light intensity when the polarity of the alternating current is reversed in a specific period in a half cycle of the first pulse wave.

  Conventionally, the same power is supplied from the power supply unit to the discharge lamp over both the first period in which lighting driving is performed based on a high-frequency pulse wave and the second period in which lighting driving is performed based on a low-frequency pulse wave. Was controlled to be supplied. This is a control to keep the input power constant at an instantaneous time point in each period. However, when such control is performed, the difference in the frequency of occurrence of polarity reversal between the first period and the second period may cause a difference in light intensity in each period. As described above.

  The above problem is that even if constant power control is performed instantaneously in each period, the average input power is not constant when each period is viewed as a whole due to the difference in the frequency of polarity reversal. This is thought to be due to disappearance. Therefore, a difference occurs between the average value of the light intensity in the first period and the average value of the light intensity in the second period, and flicker is visually recognized. In particular, when power is supplied from the power supply unit to the discharge lamp based on a first pulse wave whose polarity is inverted at an extremely high frequency of, for example, about 60 to 1000 Hz in the first period, the timing of polarity inversion of the supply current Occurs in a very short time interval, and the accompanying fluctuations in the power supply also occur in a very short time. As a result, during the period from the end of the immediately preceding second period to the start of the immediately following second period, the light intensity output from the discharge lamp increases or decreases from the steady value associated with power fluctuations. It is visually recognized as the light intensity when the average power calculated in consideration is continuously supplied.

  Similarly, in the second period from the end of the immediately preceding first period to the start of the immediately following first period, the light intensity output from the discharge lamp is the average power supplied in the period. It is visually recognized as the light intensity when continuously supplied. However, the frequency of polarity reversal that occurs compared to the immediately preceding first period is less. Therefore, at the timing of each moment, even if control is performed so that the supplied power is equal between the first period and the second period, the second period is immediately before due to the difference in the frequency of polarity reversal. There is a difference in the average power supplied compared to the first period. This difference in average power is visually recognized as flicker.

  The discharge lamp lighting device according to the present invention is based on the control from the power control unit in a direction to cancel the change in light intensity at the time of polarity inversion of the alternating current in a specific period in the half cycle of the first pulse wave. Then, control for changing the control power value is performed. Thereby, the change (decrease or increase) of the light intensity accompanying the polarity inversion in the first period in which the occurrence frequency of the polarity inversion is high is alleviated. As a result, the light intensity difference between the first period and the second period as described above is reduced, and flicker is suppressed.

  In addition, in a specific period in the half cycle of the first pulse wave, control is performed to vary the control power value, and the change in light intensity due to polarity inversion immediately before or after the half cycle is alleviated. As described above, in the present invention, the change in the light intensity for each polarity inversion (for example, one dip or one overshoot) individually and within a short period (for example, in the range of about 100 to 1000 μs). ) Can be offset and relaxed. As a result, the instantaneous light intensity change can be alleviated each time.

  In the above configuration, the specific period is preferably a period immediately before and / or immediately after the polarity inversion.

If the specific period is a period immediately before or immediately after the polarity inversion, the change in light intensity for each polarity inversion is mitigated within an extremely short period (for example, in the range of about 100 to 1000 μs) immediately before or after the change. can do. As a result, an instantaneous change in light intensity can be more suitably mitigated.
Further, when the specific period is a period immediately before and after the polarity inversion, the control power value is changed at two locations immediately before and after the polarity inversion. And the change of the light intensity for one polarity inversion will be relieved by the fluctuation | variation of the control electric power value in these two places. As a result, the fluctuation amount of the control power value at one place can be reduced. Thereby, the change of the light intensity at the time of relieving the change of the light intensity for one polarity inversion can be suppressed, and flicker can be further suppressed.

  The said structure WHEREIN: It is preferable that the said specific period is set for every polarity inversion in said 1st period. If the specific period is set for every polarity inversion in the first period, the change in light intensity for every polarity inversion in the first period can be alleviated. As a result, it is possible to achieve a state in which there is almost no change in light intensity due to polarity inversion over the entire first period.

  In the above configuration, the power control unit may be configured such that the difference between the integrated value of the light intensity that changes during the specific period and the integrated value of the light intensity that changes when the polarity is inverted is within a range of ± 2%. It is preferable to perform control to vary the control power value. When the control power value is varied so that the difference between the integrated value of the light intensity that changes during the specific period and the integrated value of the light intensity that changes during the polarity inversion is within a range of ± 2%. The change in light intensity associated with the polarity inversion can be alleviated without excess or deficiency for each polarity inversion.

  In the above configuration, it is preferable that the specific period is in a range of 50 to 700 μs, and a variation amount of the control power value is within ± 20%. When the specific period is in the range of 50 to 700 μs and the fluctuation amount of the control power value is in the range of ± 20%, it is possible to more suitably alleviate the change in light intensity due to polarity inversion. .

  According to the lighting device of the present invention, it is possible to suppress flickering (flicker) of light output from the discharge lamp as compared with the related art.

It is a cross-sectional schematic diagram of a discharge lamp. It is the cross-sectional schematic diagram which expanded the electrode tip vicinity of the discharge lamp. It is a circuit block diagram which shows typically the structure of a discharge lamp lighting device. It is a figure which shows an example of the lamp current waveform and light intensity waveform which concern on 1st Embodiment. It is a typical drawing explaining the setting method of control electric power value. It is a graph which shows the relationship between a light intensity difference and a flicker level. It is a figure which shows an example of the lamp current waveform and light intensity waveform which concern on 2nd Embodiment. It is a figure which shows an example of the lamp current waveform and light intensity waveform which concern on 3rd Embodiment. It is a figure which shows an example of the lamp current waveform and light intensity waveform which concern on 4th Embodiment. It is a figure which shows an example of the conventional lamp current waveform. It is a figure which shows an example of the conventional lamp current waveform and the waveform of light intensity. It is a figure which shows an example of a part of conventional lamp current waveform.

  An embodiment of a discharge lamp lighting device of the present invention will be described with reference to the drawings.

[First Embodiment]
Hereinafter, prior to the description of the configuration of the lighting device, the configuration of a discharge lamp to which an alternating current is supplied by the lighting device will be described with reference to the drawings. In each figure, the dimensional ratio in the drawing does not necessarily match the actual dimensional ratio.

[Lamp configuration]
1A and 1B are schematic cross-sectional views of a discharge lamp. FIG. 1B is a schematic cross-sectional view enlarging the vicinity of the electrode tip of FIG. 1A.

  The discharge lamp 10 has a substantially spherical light emitting portion 11 formed by a discharge vessel made of quartz glass. The material of the discharge vessel is not limited to quartz glass, and may be made of other materials.

  In the light emitting unit 11, a pair of electrodes 20a and 20b are disposed to face each other at an extremely small interval of, for example, 2 mm or less.

  Further, sealing portions 12 are formed at both ends of the light emitting portion 11. A conductive metal foil 13 made of molybdenum or the like is hermetically embedded in the sealing portion 12 by, for example, a shrink seal. The shaft portions of the electrodes 20a and 20b are joined to one end of the metal foil 13, and the external lead 14 is joined to the other end of the metal foil 13, and power is supplied from the discharge lamp lighting device of the present invention described later. .

  Mercury, rare gas, and halogen gas are sealed in the light emitting portion 11 of the discharge lamp 10.

Mercury is used to obtain a necessary visible light wavelength, for example, radiation having a wavelength of 360 to 780 nm, and in terms of specific values, 0.20 mg / mm ³ or more is enclosed. Although the amount of sealing varies depending on the temperature condition, a high vapor pressure of 200 atm or more is realized as the pressure inside the light emitting unit during lighting. In addition, by enclosing more mercury, it is possible to make a discharge lamp with a high mercury vapor pressure of mercury vapor pressure of 250 atm or higher and 300 atm or higher when the lamp is turned on. it can.

  As the rare gas, for example, argon gas is sealed at about 13 kPa. Its function is to improve the lighting startability.

As the halogen gas, iodine, bromine, chlorine, etc. are enclosed in the form of a compound with mercury or other metals. The amount of halogen encapsulated is selected from the range of 10 ⁻⁶ μmol / mm ³ to 10 ⁻² μmol / mm ³ . The biggest reason for enclosing the halogen is to extend the life of the discharge lamp using a so-called halogen cycle. Further, when the discharge lamp 10 is extremely small and has a very high lighting vapor pressure, the effect of preventing devitrification of the discharge vessel can be obtained by enclosing the halogen. Devitrification means that crystallization proceeds from a metastable glass state and changes to an aggregate of crystal grains grown from many crystal nuclei. If such a phenomenon occurs, light is scattered at the grain boundaries of the crystal and the discharge vessel becomes opaque.

  In addition, as long as the same function is realizable, the gas enclosed with the light emission part 11 is not limited to the said gas.

As an example of the discharge lamp 10, the maximum outer diameter of the light emitting part is 9.4 mm, the distance between the electrodes is 1.0 mm, the inner volume of the discharge vessel is 55 mm ³ , the rated voltage is 70 V, and the rated power is 180 W. It can be set as a structure.

In addition, when it is assumed that a discharge lamp 10 is built in and used in a projector that has been miniaturized in recent years, the discharge lamp 10 is required to be extremely small as a whole size, and on the other hand, a high light emission amount is also required. . For this reason, the thermal influence in the light emitting part is extremely severe, and the lamp wall load value of the lamp is 0.8 to 2.5 W / mm ² , specifically 2.4 W / mm ² . As described above, the discharge lamp 10 having a high mercury vapor pressure and a tube wall load value is mounted on a presentation device such as a projector or an overhead projector, thereby providing the presentation device with emitted light having good color rendering properties. be able to.

[Shape of electrode tip]
As shown in FIG. 1B, the electrode 20a includes a head portion 29a and a shaft portion 30a, and the electrode 20b includes a head portion 29b and a shaft portion 30b. Each of the electrode 20a and the electrode 20b has a protrusion 21 at the tip. The protrusion 21 is formed by agglomerating molten electrode material at the electrode tip when the lamp is turned on. In the present embodiment, the electrode 20a and the electrode 20b are described as both made of tungsten, but the material is not limited to this.

  When the electrode 20a and the electrode 20b are energized, the electrode 20a and the electrode 20b are heated to a high temperature, and tungsten constituting them is sublimated. The sublimated tungsten is combined with the enclosed halogen gas in the inner wall surface region of the light emitting portion 11 which is a relatively low temperature portion to form tungsten halide. Since the vapor pressure of tungsten halide is relatively high, it moves again in the vicinity of the tips of the electrodes 20a and 20b in the gas state. When heated again at this point, the tungsten halide is separated into halogen and tungsten. Among these, tungsten returns to the tips of the electrodes 20 a and 20 b and aggregates, and the halogen returns as the halogen gas in the light emitting unit 11. This corresponds to the “halogen cycle” described above. The agglomerated tungsten adheres to the vicinity of the tips of the electrode 20a and the electrode 20b, whereby the protrusion 21 is formed.

[Configuration of lighting device]
FIG. 2 is a circuit block diagram schematically showing the configuration of the discharge lamp lighting device of the present invention. As shown in FIG. 2, the lighting device 1 includes a power feeding unit 3 and a control unit 4. The control unit 4 includes a pulse generation unit 41, a power control unit 42, and a frequency control unit 43, and a pulse wave P having a frequency determined based on a signal from the frequency control unit 43 is supplied from the pulse generation unit 41 to the power supply unit. 3 is supplied. And the electric power feeding part 3 is alternating current based on the signal (corresponding to the gate signal Gx in FIG. 2) regarding the control electric power value output from the electric power control part 42, and the pulse wave P output from the pulse generation part 41. A current is generated and supplied to the discharge lamp 10. The discharge lamp 10 lights up when this alternating current is supplied.

<Power supply unit 3>
The power feeding unit 3 includes a step-down chopper unit 31, a DC / AC conversion unit 32, and a starter unit 33.

  The step-down chopper unit 31 steps down the supplied DC voltage Vdc to a desired low voltage and outputs it to the DC / AC conversion unit 32 at the subsequent stage. In FIG. 2, as a specific configuration example, the step-down chopper unit 31 includes a switching element Qx, a reactor Lx, a diode Dx, a smoothing capacitor Cx, a resistor Rx, and a voltage dividing resistor Vx.

  Switching element Qx has one end connected to the + side power supply terminal to which DC voltage Vdc is supplied and the other end connected to one end of reactor Lx. The diode Dx has a cathode terminal connected to a connection point between the switching element Qx and the reactor Lx, and an anode terminal connected to the negative power supply terminal. The smoothing capacitor Cx has one end (+ side terminal) connected to the output side terminal of the reactor Lx and the other end (− side terminal) connected to the output side terminal of the resistor Rx. The resistor Rx is connected between the negative terminal of the smoothing capacitor Cx and the anode terminal of the diode Dx, and realizes a current detection function. In addition, the voltage dividing resistor Vx is connected between the − side terminal and the + side terminal of the smoothing capacitor Cx to realize a voltage detection function.

  The switching element Qx is driven by a gate signal Gx output from the power control unit 42. Based on the duty of the gate signal Gx, the step-down chopper unit 31 steps down the input DC voltage Vdc to a voltage corresponding to the duty and outputs it to the DC / AC conversion unit 32 at the subsequent stage.

  The DC / AC conversion unit 32 converts the input DC voltage into an AC voltage having a desired frequency, and outputs the AC voltage to the subsequent starter unit 33. In FIG. 2, as a specific configuration example, the DC / AC converter 32 is configured by switching elements Q1 to Q4 connected in a bridge shape (full bridge circuit).

  The switching element Q1 is driven by a gate signal G1 output from the driver 35. Similarly, the switching element Q2 is driven by the gate signal G2, the switching element Q3 is driven by the gate signal G3, and the switching element Q4 is driven by the gate signal G4. The driver 35 outputs a gate signal to alternately repeat on / off for the pair of switching elements Q1 and Q4 and the pair of switching elements Q2 and Q3 arranged diagonally. Thereby, a rectangular wave AC voltage is generated between the connection point of the switching elements Q1 and Q2 and the connection point of the switching elements Q3 and Q4.

  The starter unit 33 is a circuit unit for boosting the alternating voltage supplied from the DC / AC conversion unit 32 when starting the discharge lamp and supplying the boosted voltage to the discharge lamp 10. In FIG. 2, as a specific configuration example, the starter unit 33 is configured by a coil Lh and a capacitor Ch. When the discharge lamp is started, an AC voltage having a high switching frequency (for example, several hundred kHz) in the vicinity of the resonance frequency of the LC series circuit including the coil Lh and the capacitor Ch is applied from the DC / AC conversion unit 32, whereby the starter unit 33 On the next side, a high voltage required for starting the discharge lamp is generated and supplied to the discharge lamp 10. After the discharge lamp is lit, the frequency of the AC voltage supplied from the DC / AC converter 32 is shifted to a steady frequency (for example, 60 to 1000 Hz), and a steady lighting operation is performed. This steady frequency corresponds to the frequency of a pulse wave P1 described later.

  In the above circuit, the change in the frequency of the AC voltage supplied to the starter unit 33 is performed by switching on / off the switching element Q1 and Q4 group and the switching element Q2 and Q3 group in the DC / AC conversion unit 32. This can be achieved by adjusting the period. Further, the change of the peak value of the AC voltage supplied to the starter unit 33 can be achieved by adjusting the operation duty of the switching element Qx in the step-down chopper unit 31.

  That is, the switching element Qx of the step-down chopper unit 31 is turned on / off at a switching frequency corresponding to the duty of the gate signal Gx output from the power control unit 42, thereby changing the power supplied to the discharge lamp 10. For example, when it is desired to increase the power supplied to the discharge lamp 10, the power control unit 42 performs control to increase the duty of the gate signal Gx so that a desired power value is obtained.

<Control unit 4>
As described above, the control unit 4 includes the pulse generation unit 41, the power control unit 42, and the frequency control unit 43. The pulse generator 41 outputs the generated pulse signal P to the driver 35 of the DC / AC converter 32. As described above, switching control for the switching elements Q1 to Q4 of the DC / AC converter 32 is performed based on this pulse signal.

  The pulse generator 41 generates a pulse signal having a frequency specified by the frequency controller 43. The frequency control unit 43 may be configured by a microcomputer or the like together with the power control unit 42 described above.

  The pulse wave P supplied from the power supply unit 3 to the discharge lamp 10 will be described with reference to FIG. FIG. 3A is a diagram showing an example of the waveform of the pulse signal P, that is, the lamp current waveform of the discharge lamp 10. In the following description, the pulse wave P shown in FIG. 3A is compared with the pulse wave P shown in FIG. 9 in that the current value Ia1 is added in the period Ta1 and the current value Ia2 is added in the period Ta3. Except for the case where it is the same, the case where it is the same will be described. However, in FIG. 3A, the ratio is different from that in FIG.

  The pulse wave P supplied from the power supply unit 3 outputs a pulse wave P1 (corresponding to “first pulse wave”) having a fundamental frequency f1 for a predetermined period T1 (corresponding to “first period”), and then the fundamental frequency f1. A cycle of outputting a pulse wave P2 having a lower frequency f2 (corresponding to the “second pulse wave”) for a predetermined period T2 (corresponding to the “second period”) that is shorter than that is repeated. This is the same as the content described above with reference to FIG. In FIG. 9, for the sake of explanation, there is no significant difference between the lengths of the period T1 and the period T2, but in actuality, the length of the period T1 is sufficiently longer than the length of the period T2. It doesn't matter.

  However, in the present embodiment, the pulse wave P is set so that a constant amount of current value is added to the pulse wave P for a predetermined period immediately after the polarity inversion of the supply current. Specifically, the pulse wave P1 is set so that the current value Ia1 is added to the peak value I1 during the period Ta1 (corresponding to the “specific period”) immediately after the polarity inversion. That is, the value of the control power value specified from the power control unit 42 to the power feeding unit 3 is different between the period Ta1 and the period Ta2 until the next polarity reversal after the period Ta1 elapses. In this example, the gate signal Gx is supplied from the power control unit 42 to the switching element Qx so that the power value in the period Ta1 is higher than the power value in the period Ta2. More specifically, in the period Ta1, the duty ratio of the gate signal Gx is increased compared to the period Ta2, so that the power supplied to the discharge lamp 10 in the period Ta1 is increased compared to the period Ta2.

  In the present embodiment, similarly to the pulse wave P1, the pulse wave P2 is set so that the current value Ia2 is added to the peak value I1 during the period Ta3 immediately after the polarity inversion. That is, the value of the control power value specified from the power control unit 42 to the power feeding unit 3 is different between the period Ta3 and the period Ta4 until the next polarity reversal after the period Ta3 elapses. In this example, the gate signal Gx is supplied from the power control unit 42 to the switching element Qx so that the power value in the period Ta3 is higher than the power value in the period Ta4. More specifically, in the period Ta3, the duty ratio of the gate signal Gx is increased compared to the period Ta4, so that the power supplied to the discharge lamp 10 in the period Ta3 is increased compared to the period Ta4.

  The power control unit 42 appropriately changes the duty ratio of the gate signal Gx based on the value of the current flowing through the resistor Rx of the power supply unit 3 and the voltage value indicated by the voltage dividing resistor Vx, and sets the input power value as a target power value ( Feedback control for maintaining the control power value). In addition, when the control unit 4 receives a signal related to the switching timing of the period Ta1 and the period Ta2 or a signal related to the switching timing of the period Ta3 and the period Ta4, the power control unit 42 controls the control power based on the signal. Change the value. The power control unit 42 changes the duty ratio of the gate signal Gx so that the power value input by the feedback control matches the set control power value. Note that information on the control power value in the period Ta1 (information on the current value Ia1 to be increased), information on the control power value in the period Ta2, information on the control power value in the period Ta3 (information on the current value Ia2 to be increased), and the period Information regarding the control power value in Ta4 may be stored in advance by the power control unit 42. At this time, information regarding the control power value itself in each period (period Ta1, period Ta2, period Ta3, period Ta4) may be stored, or control power between one period and another period may be stored. Information regarding the ratio of values may be stored.

  The frequency control unit 43 outputs information related to the frequency of the pulse wave P to the pulse generation unit 41 at a predetermined timing so that the pulse wave P exhibits frequency fluctuation as shown in FIG. For example, the frequency control unit 43 includes a timer that measures an elapsed time since the output of the pulse wave P is started, a frequency f1 of the pulse wave P1, a continuous output period T1 of the pulse wave P1, a frequency f2 of the pulse wave P2, And the memory which memorize | stored the information regarding the continuous output period T2 of the pulse wave P2 can be provided. At this time, the frequency control unit 43 determines the frequency of the pulse wave P based on the information related to the elapsed time given from the timer and the information stored in the memory, and outputs it to the pulse generation unit 41. The pulse generator 41 outputs a pulse wave P having a frequency determined based on a control signal from the frequency controller 43 to the power feeder 3.

  For example, the frequency control unit 43 first sets the pulse generation unit 41 to output a pulse wave having the frequency f1 at the start of pulse generation. Next, when the elapse of the period T1 is detected by the timer, the frequency control unit 43 reads information related to the frequency f2 of the pulse wave P2 from the memory, and sets the pulse wave of the frequency f2 to be output. Further, when the elapse of the period T2 is detected by the timer, information related to the frequency f1 of the pulse wave P1 is read from the memory, and the pulse wave having the frequency f1 is set to be output again. The frequency control unit 43 repeats such control below.

  When the frequency control unit 43 includes the timer as described above, the power control unit 42 is also notified of the period T1 at the timing when a signal for changing the frequency is output to the pulse generation unit 41. A signal related to the switching timing of the period T2 may be output.

  The frequency (fundamental frequency) of the pulse wave P1 corresponds to the fundamental frequency when the discharge lamp 10 is steadily turned on, and is one frequency selected from the range of 60 to 1000 Hz, for example. The pulse wave P2 is a low frequency that is intermittently inserted after the lapse of the period T1, and the frequency is a frequency that is lower than the fundamental frequency, for example, selected from a range of 5 to 200 Hz.

  In the example of FIG. 3A, the period T2 during which the pulse wave P2 is output is set to one period of the pulse wave P2. That is, in this period T2, the pulse generation unit 41 is configured to output the positive and negative pulse waves P2 once each. However, the output form of the pulse wave P2 is not limited to such a form.

  For example, after the pulse generator 41 outputs the pulse wave P1 only for a predetermined period T1, the low-frequency pulse wave P2 is output only for a half of the period T2 (that is, the pulse wave P2 is output by a half wavelength). In this case, after the pulse wave P1 is further output for the time T1, the polarity of the pulse wave P2 is changed from the previous one and output only for a half period T2. Furthermore, the low-frequency pulse wave P2 included in the pulse signal output from the pulse generator 41 is a period corresponding to 1.5 periods of the pulse wave P2 (that is, a period 1.5 times the period T2), etc. It may be configured to include over a period equal to or longer than a period corresponding to one cycle. However, if the application time of the low-frequency pulse wave P2 is excessively extended, the shape of the protrusion 21 serving as the arc starting point may change due to excessive heating of the electrode. It is preferable to keep P2 within one period.

[Action]
FIG. 3B is a graph showing the change in the light intensity of the projection light in accordance with the lamp current waveform shown in FIG.

  As described above with reference to FIG. 3A, in the lighting device 1 of the present embodiment, the input power from the power supply unit 3 to the discharge lamp 10 is greater than the period Ta2 by the control from the power control unit 42. Is set to be higher. Further, the period Ta3 is set higher than the period Ta4. As a result, as shown in FIG. 3B, the light intensity increases by an amount (integrated value Sa2) corresponding to the current value increased in the period Ta1. Further, the light intensity increases by an amount (integrated value Sa4) corresponding to the current value to be increased in the period Ta3.

As described above with reference to FIG. 10 in the section “Problems to be Solved by the Invention”, since the frequency of polarity inversion is higher in the period T1 than in the period T2, the occurrence frequency of the dip D1 is high. As a result, in the state shown in FIG. 10, the average light intensity in the period T1 is lower than the average light intensity in the period T2, causing flicker. On the other hand, according to the configuration of the present embodiment, the integrated value Sa1 of the light intensity that decreases due to the polarity inversion in the period T1 is canceled by the integrated value Sa2 of the light intensity that corresponds to the current value that is increased in the period Ta1. It is possible to compensate for a decrease in light intensity due to inversion. Thereby, the change of the light intensity accompanying polarity inversion in the period T1 where the frequency of occurrence of polarity inversion is high is alleviated. As a result, the light intensity difference between the period T1 and the period T2 as described above is reduced, and flicker is suppressed.
In this specification, the dip (the integrated value of the light intensity that decreases due to polarity reversal) means that after the light intensity drops to 90% or less of the light intensity immediately before the polarity reversal (1 when stable), after the polarity reversal. The integrated value of the decrease in light intensity compared with (1 at stable time) in the period until the ripple is recovered to 90% or more of the light intensity in the smoothed state (2 at stable time).

  Further, according to the present embodiment, the pulse wave P1 is set so that the current value Ia1 is added to the peak value I1 during the period Ta1 immediately after the polarity inversion. As described above, in the present embodiment, the decrease in the light intensity for each polarity inversion can be offset individually and mitigated in the extremely short period immediately after the decrease. As a result, an instantaneous decrease in light intensity can be compensated each time.

  Further, according to the present embodiment, the fluctuation of the control power value, that is, the addition of the current value Ia1 is set for every polarity inversion in the period T1. Accordingly, it is possible to compensate for a decrease in light intensity for every polarity inversion in the period T1. As a result, it is possible to achieve a state where there is almost no decrease in light intensity due to polarity inversion over the entire period T1.

  Further, according to the present embodiment, the pulse wave P2 is set so that the current value Ia2 is added to the peak value I1 during the period Ta3 immediately after the polarity inversion. Therefore, it is possible to compensate for a decrease in light intensity at each polarity inversion in the period T2 in an extremely short period immediately after the change.

  Further, according to the configuration of the present embodiment, the integrated value Sa3 of the light intensity that decreases due to the polarity inversion in the period T2 is canceled by the integrated value Sa4 of the light intensity that corresponds to the current value that is increased in the period Ta3, so that the polarity is inverted. The accompanying decrease in light intensity can be compensated.

  In particular, in the present embodiment, control for changing the control power value for every polarity inversion in the period T1 is performed, and control for changing the control power value for every polarity inversion in the period T2. . Therefore, the change in the light intensity for each polarity inversion is alleviated at the timing for each polarity inversion. Therefore, it is visually recognized that there is almost no difference in light intensity in the period T1 and the period T2. As a result, the occurrence of flicker can be more suitably suppressed.

  In the above-described embodiment, the case where the control for changing the control power value is performed not only in the period T1 but also in the period T2. However, the present invention is not limited to this example, and control for changing the control power value is performed only during the period T1, and control for changing the control power value may not be performed during the period T2. In the period T2, the frequency of polarity reversal is lower than that in the period T1, and the frequency of light intensity change due to polarity reversal is also small. Therefore, even if control for changing the control power value is not performed in the period T2, flicker is not caused. This is because it can be allowed.

  In the above-described embodiment, the case has been described in which the control power value is changed for every polarity inversion in the period T1. However, in the present invention, the control power value may be changed only at a part of the polarity inversion timing among all the polarity inversions in the period T1. For example, the control power value may be changed in a part of all polarity inversions in the period T1, for example, 60% or more, more preferably 80% or more. This is because flicker can be allowed if the control power value is changed at a certain or higher polarity inversion timing among all polarity inversions in the period T1.

  In the present embodiment, the length of the period Ta1 and the length of the period Ta3 are the same from the viewpoint of facilitating control and more preferably suppressing flicker, and the current value Ia1 and current to be added are the same. The value Ia2 is the same. However, the present invention is not limited to this example. For example, the integrated value Sa1 can be canceled by the integrated value Sa2, and the change in the light intensity accompanying the polarity inversion can be reduced, and the integrated value Sa3 can be canceled by the integrated value Sa4, and the change in the light intensity accompanying the polarity inversion can be reduced. If possible, the length of the period Ta1 may be different from the length of the period Ta3, and the current value Ia1 and the current value Ia2 to be added may be different.

The period Ta1 is preferably 1 to 14 times as long as the period in which the light intensity is changed based on the polarity inversion (in this embodiment, the period Tx of the dip D1). More preferably.
Also, the period Ta3 is preferably 1 to 14 times the period in which the light intensity is changed based on the polarity inversion (the period Tx of the dip D1 in this embodiment), and is 1 to 2 times as long. More preferably, the period.

The current value Ia1 to be added is preferably within ± 20% of the peak value I1, and more preferably within ± 15%.
Further, the current value Ia2 to be added is preferably within a range of ± 20% of the peak value I1, and more preferably within a range of ± 15%.
If the current value Ia1 to be added and the current value Ia2 to be added are too large compared to the peak value I1, the amount of compensation will be too much with respect to the amount of decrease in the light intensity of the dip D1. May increase change.

  The specific period Ta1 is preferably in the range of 50 to 700 μs, and more preferably in the range of 50 to 150 μs. The period Ta2 is a period obtained by subtracting the period Ta1 from the half-cycle period of the pulse wave P1. When the period Ta1 is within the above range, it is possible to more suitably alleviate the change in light intensity associated with polarity inversion.

  The specific period Ta3 is preferably in the range of 50 to 700 μs, and more preferably in the range of 50 to 150 μs. The period Ta4 is a period obtained by subtracting the period Ta3 from the half cycle period of the pulse wave P2.

  It should be noted that the fluctuation amount of the control power value of the present invention is not so great as to melt and evaporate the minute protrusions and irregularities other than the tip of the electrode, and only to moderate the change in light intensity at the time of polarity reversal.

[Setting Method in Power Control Unit 42]
As described above, the power control unit 42 stores the control power values in the periods Ta1, Ta2, Ta3, and Ta4 in advance. Hereinafter, an example of a method for setting the control power value will be described. The setting of the control power value may be performed at a stage before the lighting device 1 and the discharge lamp 10 are shipped.

  FIG. 4 is a schematic diagram for explaining a control power value setting method. The light from the projection device 51 including the discharge lamp 10 and the optical system is irradiated toward the light detection unit 53 including a high-sensitivity sensor and the time change of the light intensity detected by the light detection unit 53 is changed to an oscilloscope. 54. At this time, the lighting device 1 first supplies current to the discharge lamp 10 in a state where the control power value is constant in both the period Ta1 and the period Ta2. The oscilloscope 54 obtains the light intensity change mode under this state, and calculates the integrated value Sa1 of the light intensity reduced by the polarity inversion by calculation.

  Next, while changing the input power from the lighting device 1 to the discharge lamp 10 in the period Ta1, the same processing as described above is performed to calculate the integrated value Sa2 of the light intensity corresponding to the current value increased in the period Ta1, A condition is found such that the difference between the integrated value Sa2 and the integrated value Sa1 is within a predetermined threshold. Then, the value of the input power when this condition is satisfied is stored in the power control unit 42 as the value of the input power in the period Ta1.

Here, the “predetermined threshold value” is preferably within ± 2%, and more preferably within ± 1%. FIG. 5 is a graph showing the relationship between the difference between the integrated value Sa2 and the integrated value Sa1 and the flicker level. Here, the main horizontal axis (lower horizontal axis) is a difference between the integrated value Sa2 and the integrated value Sa1, and is a value calculated by the following (Equation 1).
(Equation 1)
Difference between integrated value Sa2 and integrated value Sa1 = (integrated value Sa2-integrated value Sa1) / integrated value Sa1

  The vertical axis indicates the flicker level, which is a numerical value of the degree of flickering of the screen at a frequency that can be seen by a person. Here, “minor flicker” refers to a level that may be viewed as flicker depending on the person or environment to be viewed, and “severe flicker” refers to a level that is viewed as flicker regardless of the person or environment that has been viewed. Point to. Further, “no flicker” refers to a level that is not visually recognized as flicker regardless of the visually recognized person or environment.

  As can be seen from FIG. 5, when the difference between the integrated value Sa2 and the integrated value Sa1 exceeds ± 2%, it becomes a level (severe flicker) that many viewers can visually recognize as flicker. On the other hand, by keeping this difference within ± 2%, the probability of being visually recognized as flicker can be reduced, and by keeping it within ± 1%, it is possible to make the state completely invisible as flicker.

  Before the shipment, the values of the input power in each of the periods Ta1 and Ta2 are set in each period so that the difference between the integrated value Sa2 and the integrated value Sa1 is within ± 2% by the method described above. The value is stored in the power control unit 42 as a control power value.

  Similarly, in the periods Ta3 and Ta4, the values of the input power in each of the periods Ta3 and Ta4 are controlled in each period so that the difference between the integrated value Sa3 and the integrated value Sa4 is within ± 2%. The power value is stored in the power control unit 42 as a power value.

  According to the lighting device 1 in the state in which such a setting is made in the power control unit 42, even if the lighting control based on the pulse wave P1 and the pulse wave P2 is performed on the discharge lamp 10, the light intensity of the dip D1 and the dip D2 is increased. Since the decrease is mitigated, the light intensity difference between the period T1 during which the pulse wave P1 is output and the period T2 during which the pulse wave P2 is output becomes extremely small, and the light intensity flickers at the location illuminated by the discharge lamp 10 ( Flicker) is suppressed.

  In the first embodiment described above, the case where the control power value is increased immediately after polarity inversion has been described. However, the present invention is not limited to this example. In the present invention, the timing of changing the control power value may be both immediately before and after the polarity inversion. This case will be described in the second embodiment below. Moreover, it may be just before polarity inversion. This case will be described in the following third embodiment. In the first embodiment, the case where the control power value is increased has been described. However, in the present invention, the control power value may be changed and may be decreased in addition to the increase. This case will be described in the following fourth embodiment.

[Second Embodiment]
The second embodiment differs from the lighting device 1 according to the first embodiment in that the period during which the power control unit varies the control power value is two places immediately before and after the polarity inversion, and is common in other respects. . Therefore, only different parts will be described below, and description of common parts will be omitted. In addition, the same reference numerals as those in the first embodiment are used for the common configurations.

  In the second embodiment, the pulse wave P supplied from the power supply unit 3 to the discharge lamp 10 will be described with reference to FIG. FIG. 6A shows an example of the waveform of the pulse signal P, that is, the lamp current waveform of the discharge lamp 10. In the following, the pulse wave P shown in FIG. 6A is added with the current value Ib1 in the periods Tb1 and Tb3, and the current value Ib2 in the periods Tb4 and Tb6, compared with the pulse wave P shown in FIG. Except for the addition of, the case is the same, but FIG. 6A shows the ratio different from that in FIG. 9 for convenience of explanation.

  The pulse wave P supplied from the power supply unit 3 outputs a pulse wave P1 (corresponding to “first pulse wave”) having a fundamental frequency f1 for a predetermined period T1 (corresponding to “first period”), and then the fundamental frequency f1. A cycle of outputting a pulse wave P2 having a lower frequency f2 (corresponding to the “second pulse wave”) for a predetermined period T2 (corresponding to the “second period”) that is shorter than that is repeated. This is the same as the content described above with reference to FIG.

  However, in the present embodiment, the pulse wave P is set so that a constant amount of current value is added to the pulse wave P for a predetermined period immediately before and after the polarity inversion of the supply current. Specifically, the pulse wave P1 is set so that the current value Ib1 is added to the peak value I1 during the period Tb1 immediately after the polarity inversion and during the period Tb3 immediately before the next polarity inversion. Note that the total period of the period Tb1 and the period Tb3 corresponds to the specific period of the present invention. That is, the values of the control power values specified from the power control unit 42 to the power feeding unit 3 are different between the periods Tb1 and Tb3 and the period Tb2 from the period Tb1 to the next period Tb3. In this example, the gate signal Gx is supplied from the power control unit 42 to the switching element Qx so that the power value in the period Tb1 and the period Tb3 is higher than the power value in the period Tb2. More specifically, in the period Tb1 and the period Tb3, the duty ratio of the gate signal Gx is increased compared to the period Tb2, so that the power supplied to the discharge lamp 10 in the period Tb1 and the period Tb3 is increased compared to the period Tb2. .

  Further, in the present embodiment, like the pulse wave P1, the current value of Ib2 is added to the peak value I1 during the period Tb4 immediately after the polarity inversion and during the period Tb6 immediately before the next polarity inversion. It is set to do. That is, the values of the control power values specified from the power control unit 42 to the power feeding unit 3 are different between the periods Tb4 and Tb6 and the period Tb5 from the period Tb4 to the next period Tb6. In this example, the gate signal Gx is supplied from the power control unit 42 to the switching element Qx so that the power value in the period Tb4 and the period Tb6 is higher than the power value in the period Tb5. More specifically, in the period Tb4 and the period Tb6, the duty ratio of the gate signal Gx is increased compared to the period Tb5, so that the power supplied to the discharge lamp 10 in the period Tb4 and the period Tb6 is increased as compared with the period Tb5. .

  The power control unit 42 appropriately changes the duty ratio of the gate signal Gx based on the value of the current flowing through the resistor Rx of the power supply unit 3 and the voltage value indicated by the voltage dividing resistor Vx, and sets the input power value as a target power value ( Feedback control for maintaining the control power value). In the control unit 4, a signal related to the switching timing of the periods Tb1 and Tb2, a signal related to the switching timing of the periods Tb2 and Tb3, a signal related to the switching timing of the periods Tb4 and Tb5, and the switching of the periods Tb5 and Tb6. When a signal related to the timing is given, the power control unit 42 changes the control power value based on the signal. The power control unit 42 changes the duty ratio of the gate signal Gx so that the power value input by the feedback control matches the set control power value. Note that information regarding the control power value in each period (period Tb1 to period Tb6) may be stored in advance by the power control unit 42. At this time, information regarding the control power value itself in each period may be stored, or information regarding the ratio of the control power value between one period and the other period may be stored. I do not care.

  The control of the frequency control unit 43 can be basically the same as in the first embodiment. Therefore, the description here is omitted.

[Action]
FIG. 6B is a graph showing the change in the light intensity of the projection light according to the lamp current waveform shown in FIG.

  In this embodiment, the control power value is changed at two locations immediately before and after the polarity inversion. And the change of the light intensity for 1 time of polarity inversion is relieved by the fluctuation | variation of the control electric power value in these 2 places. Specifically, the light intensity integrated value Sb1 that decreases due to polarity reversal, the light intensity integrated value Sb2 that corresponds to the current value that increases in the immediately preceding period Tb3, and the light that corresponds to the current value that increases in the immediately following period Tb1. The total integrated value with the integrated intensity value Sb3 is canceled out to compensate for the decrease in light intensity caused by polarity inversion. Further, the integrated value Sb4 of the light intensity that decreases due to the polarity inversion is integrated with the integrated value Sb5 of the light intensity corresponding to the current value that is increased in the immediately preceding period Tb6 and the integrated value of the light intensity that is increased in the immediately following period Tb4. The total integrated value with the value Sb6 is canceled out to compensate for the decrease in light intensity due to the polarity inversion. Thereby, the change of the light intensity accompanying polarity inversion is relieved.

  In the present embodiment, the lengths of the period Tb1, the period Tb3, the period Tb4, and the period Tb6 are the same from the viewpoint of facilitating control and more preferably suppressing flicker. The current value Ib1 and the current value Ib2 to be performed are the same. However, the present invention is not limited to this example. For example, the integrated value Sb1 can be canceled by the sum of the integrated value Sb2 and the integrated value Sb3, and the change in the light intensity due to the polarity inversion can be reduced. The integrated value Sa4 can be converted into the integrated value Sb5 and the integrated value Sb6. The lengths of the period Tb1, the period Tb3, the period Tb4, and the period Tb6 may be different as long as they can be canceled out in total and the change in light intensity caused by polarity inversion can be reduced, and the added current value Ib1 It may be different from the current value Ib2.

[Third Embodiment]
The third embodiment differs from the lighting device 1 according to the first embodiment in that the period during which the power control unit varies the control power value is immediately before polarity inversion, and is common in other respects. Therefore, only different parts will be described below, and description of common parts will be omitted. In addition, the same reference numerals as those in the first embodiment are used for the common configurations.

  In the third embodiment, the pulse wave P supplied from the power supply unit 3 to the discharge lamp 10 will be described with reference to FIG. FIG. 7A is a diagram showing an example of the waveform of the pulse signal P, that is, the lamp current waveform of the discharge lamp 10. Hereinafter, a case where the pulse wave P shown in FIG. 7A is the same as the pulse wave P shown in FIG. 9 except that the current value Ic1 is added in the period Tc2 will be described. However, in FIG. 7A, the ratio is different from that in FIG. 9 for convenience of explanation.

  The pulse wave P supplied from the power supply unit 3 outputs a pulse wave P1 (corresponding to “first pulse wave”) having a fundamental frequency f1 for a predetermined period T1 (corresponding to “first period”), and then the fundamental frequency f1. A cycle of outputting a pulse wave P2 having a lower frequency f2 (corresponding to the “second pulse wave”) for a predetermined period T2 (corresponding to the “second period”) that is shorter than that is repeated. This is the same as the content described above with reference to FIG.

  However, in the present embodiment, the pulse wave P is set so that a constant amount of current value is added to the pulse wave P for a predetermined period immediately before the polarity inversion of the supply current. Specifically, the current value of Ic1 is set to be added to the peak value I1 during the period Tc2 immediately before the polarity inversion to the pulse wave P1. Note that the period Tc2 corresponds to a specific period of the present invention. That is, the value of the control power value specified from the power control unit 42 to the power feeding unit 3 is different between the period Tc2 and the period Tc1 until the next period Tc2 after polarity inversion. In this example, the gate signal Gx is supplied from the power control unit 42 to the switching element Qx so that the power value in the period Tc2 is higher than the power value in the period Tc1. More specifically, in the period Tc2, the power supply to the discharge lamp 10 in the period Tc2 is increased more than in the period Tc1 by increasing the duty ratio of the gate signal Gx than in the period Tc1.

  In the present embodiment, similarly to the pulse wave P1, the pulse wave P2 is set so that the current value Ic2 is added to the peak value I1 during the period Tc4 immediately before the polarity inversion. That is, the value of the control power value specified from the power control unit 42 to the power feeding unit 3 is different between the period Tc4 and the period Tc3 from the polarity inversion to the next period Tc4. In this example, the gate signal Gx is supplied from the power control unit 42 to the switching element Qx so that the power value in the period Tc4 is higher than the power value in the period Tc3. More specifically, in the period Tc4, the duty ratio of the gate signal Gx is increased more than in the period Tc3, whereby the power supplied to the discharge lamp 10 in the period Tc4 is increased more than in the period Tc3.

  The power control unit 42 appropriately changes the duty ratio of the gate signal Gx based on the value of the current flowing through the resistor Rx of the power supply unit 3 and the voltage value indicated by the voltage dividing resistor Vx, and sets the input power value as a target power value ( Feedback control for maintaining the control power value). Further, when the control unit 4 receives a signal related to the switching timing of the period Tc1 and the period Tc2 and a signal related to the switching timing of the period Tc3 and the period Tc4, the power control unit 42 controls the control power value based on the signal. To change. The power control unit 42 changes the duty ratio of the gate signal Gx so that the power value input by the feedback control matches the set control power value. Note that information regarding the control power value in each period (period Tc1 to period Tc4) may be stored in advance by the power control unit 42. At this time, information regarding the control power value itself in each period may be stored, or information regarding the ratio of the control power value between one period and the other period may be stored. I do not care.

  The control of the frequency control unit 43 can be basically the same as in the first embodiment. Therefore, the description here is omitted.

[Action]
FIG. 7B is a graph showing the change in the light intensity of the projection light in accordance with the lamp current waveform shown in FIG.

  In the present embodiment, the integrated value Sc1 of the light intensity that decreases due to the polarity inversion is canceled out by the integrated value Sc2 of the light intensity that corresponds to the current value that is increased in the immediately preceding period Tc2 to compensate for the decrease in the light intensity that accompanies the polarity inversion. To do. Further, the integrated value Sc3 of the light intensity that decreases due to the polarity inversion is canceled out by the integrated value Sc4 of the light intensity corresponding to the current value that is increased in the immediately preceding period Tc4 to compensate for the decrease in the light intensity that accompanies the polarity inversion. Thereby, the change of the light intensity accompanying polarity inversion is relieved.

  In the present embodiment, the length of the period Tc2 and the length of the period Tc4 are the same from the viewpoint of facilitating control and more preferably suppressing flicker, and the added current value Ic1 and current The value Ic2 is the same. However, the present invention is not limited to this example. For example, the integrated value Sc1 can be canceled by the integrated value Sc2, and the change in the light intensity due to the polarity inversion can be reduced, and the integrated value Sc3 can be canceled by the integrated value Sc4, and the change in the light intensity due to the polarity inversion can be reduced. If possible, the length of the period Tc2 may be different from the length of the period Tc4, and the current value Ic1 and the current value Ic2 to be added may be different.

[Fourth Embodiment]
In the first embodiment, a case has been described in which the control electrode value is increased in a specific period in order to compensate for the light intensity that decreases due to polarity reversal. In the fourth embodiment, a case where the control power value is reduced in a specific period will be described. As a specific example, the fourth embodiment describes a case where the control power value is decreased in a specific period in order to offset the increase when the light intensity increased by overshoot is larger than the light intensity decreased by polarity inversion. To do.
In the fourth embodiment, the period during which the control power value is changed by the power control unit is immediately before the polarity inversion, and the lighting device 1 according to the first embodiment is different in that the change in the control power value is a change to be reduced. Different and common in other respects. Therefore, only different parts will be described below, and description of common parts will be omitted. In addition, the same reference numerals as those in the first embodiment are used for the common configurations.

  In 4th Embodiment, the pulse wave P supplied to the discharge lamp 10 from the electric power feeding part 3 is demonstrated with reference to Fig.8 (a). FIG. 8A shows an example of the waveform of the pulse signal P, that is, the lamp current waveform of the discharge lamp 10. Hereinafter, the case where the pulse wave P shown in FIG. 8A is the same as the pulse wave P shown in FIG. 9 except that the current value Id1 is added in the period Td2 will be described. However, in FIG. 8A, the ratio is different from that in FIG. 9 for convenience of explanation.

  The pulse wave P supplied from the power supply unit 3 outputs a pulse wave P1 (corresponding to “first pulse wave”) having a fundamental frequency f1 for a predetermined period T1 (corresponding to “first period”), and then the fundamental frequency f1. A cycle of outputting a pulse wave P2 having a lower frequency f2 (corresponding to the “second pulse wave”) for a predetermined period T2 (corresponding to the “second period”) that is shorter than that is repeated. This is the same as the content described above with reference to FIG.

  However, in the present embodiment, the pulse wave P is set so that the current value is decreased by a certain amount for a predetermined period immediately before the polarity inversion of the supply current. Specifically, the pulse wave P1 is set to decrease the current value by the peak value I1 to Id1 during the period Td2 immediately before the polarity inversion. Note that the period Td2 corresponds to a specific period of the present invention. That is, the value of the control power value specified from the power control unit 42 to the power feeding unit 3 is different between the period Td2 and the period Td1 from the polarity inversion to the next period Td2. In this example, the gate signal Gx is supplied from the power control unit 42 to the switching element Qx so that the power value in the period Td2 is lower than the power value in the period Td1. More specifically, in the period Td2, the power supply to the discharge lamp 10 in the period Td2 is lower than that in the period Td1 by lowering the duty ratio of the gate signal Gx than in the period Td1.

  In the present embodiment, similarly to the pulse wave P1, the pulse wave P2 is set such that the current value is decreased by the peak values I1 to Id2 during the period Td4 immediately before the polarity inversion. That is, the value of the control power value designated from the power control unit 42 to the power feeding unit 3 is different between the period Td4 and the period Td3 from the polarity reversal to the next period Td4. In this example, the gate signal Gx is supplied from the power control unit 42 to the switching element Qx so that the power value in the period Td4 is lower than the power value in the period Td3. More specifically, in the period Td4, the duty ratio of the gate signal Gx is made lower than in the period Td3, so that the power supplied to the discharge lamp 10 in the period Td4 is lower than in the period Td3.

  The power control unit 42 appropriately changes the duty ratio of the gate signal Gx based on the value of the current flowing through the resistor Rx of the power supply unit 3 and the voltage value indicated by the voltage dividing resistor Vx, and sets the input power value as a target power value ( Feedback control for maintaining the control power value). In addition, when the control unit 4 receives a signal related to the switching timing of the period Td1 and the period Td2 and a signal related to the switching timing of the period Td3 and the period Td4, the power control unit 42 controls the control power value based on the signal. To change. The power control unit 42 changes the duty ratio of the gate signal Gx so that the power value input by the feedback control matches the set control power value. Note that information regarding the control power value in each period (period Td1 to period Td4) may be stored in advance by the power control unit 42. At this time, information regarding the control power value itself in each period may be stored, or information regarding the ratio of the control power value between one period and the other period may be stored. I do not care.

  The control of the frequency control unit 43 can be basically the same as in the first embodiment. Therefore, the description here is omitted.

[Action]
FIG. 8B is a graph showing a change in the light intensity of the projection light in accordance with the waveform of the lamp current shown in FIG.

  In the present embodiment, the current that decreases the difference (Sd1−Sd2) between the integrated value Sd1 of the light intensity increased by the overshoot at the time of polarity reversal and the integrated value Sd2 of the light intensity decreased by the polarity reversal in the immediately preceding period Td2. It cancels out with the integrated value Sd3 of the light intensity corresponding to the value. Further, the difference (Sd4−Sd5) between the integrated value Sd4 of the light intensity increased by the overshoot at the time of polarity reversal and the integrated value Sd5 of the light intensity decreased by the polarity reversal corresponds to the current value to be decreased in the immediately preceding period Td4. It cancels out with the integrated value Sd6 of the light intensity. Thereby, the change of the light intensity accompanying polarity inversion is relieved.

  In the present embodiment, from the viewpoint of facilitating control and more preferably suppressing flicker, the length of the period Td2 and the length of the period Td4 are the same, and the current value Id1 and the current to be reduced are reduced. The value Id2 is the same. However, the present invention is not limited to this example. For example, the difference (Sd1−Sd2) between the integrated value Sd1 and the integrated value Sd2 can be canceled by the integrated value Sd3, and the change in the light intensity due to the polarity inversion can be reduced, and the difference between the integrated value Sd4 and the integrated value Sd5. As long as (Sd4-Sd5) can be canceled by the integrated value Sd6 and the change in light intensity due to the polarity inversion can be reduced, the length of the period Td2 and the length of the period Td4 may be different and reduced. The current value Id1 and the current value Id2 may be different.

  In the first to fourth embodiments described above, the case where the timing of increasing the control power value is immediately before polarity inversion, immediately after, and both immediately before and after. However, the present invention is not limited to this example, and the control power value may be changed after a certain period of time has elapsed since the polarity inversion, and the change may be returned before the next polarity inversion. Even in such an embodiment, a change (decrease or increase) in light intensity associated with polarity inversion can be mitigated.

DESCRIPTION OF SYMBOLS 1: Lighting device 3: Power supply part 4: Control part 10: Discharge lamp 11: Light emission part 12: Sealing part 13: Metal foil 14: External lead 20a, 20b: Electrode 21: Protrusion 29a, 29b: Electrode head 30a 30b: Electrode shaft 31: Step-down chopper 32: DC / AC converter 33: Starter 35: Driver 41: Pulse generator 42: Power controller 43: Frequency controller 51: Projector 53: Photodetector 54: Oscilloscope

Claims (5)

A power feeding unit for supplying an alternating current to a discharge lamp in which a pair of electrodes are arranged to face each other in a discharge vessel in which a predetermined gas is sealed;
A power control unit that outputs a signal related to a control power value to the power supply unit;
A pulse generation unit that outputs a pulse wave to the power supply unit;
The power feeding unit is configured to convert a supplied DC voltage into an alternating current corresponding to the frequency of the pulse wave and the control power value and supply the alternating current to the discharge lamp,
The pulse generator is configured to repeat a cycle of outputting a first pulse wave over a first period and then outputting a second pulse wave having a frequency lower than that of the first pulse wave,
The power control unit performs control to vary the control power value in a direction to cancel a change in light intensity at the time of polarity reversal of the alternating current in a specific period in a half cycle of the first pulse wave. A discharge lamp lighting device characterized.   The discharge lamp lighting device according to claim 1, wherein the specific period is a period immediately before and / or immediately after the polarity inversion.   The discharge lamp lighting device according to claim 1, wherein the specific period is set for every polarity inversion in the first period. The power control unit sets the control power value so that a difference between the integrated value of the light intensity that changes during the specific period and the integrated value of the light intensity that changes during the polarity inversion is within a range of ± 2%. The discharge lamp lighting device according to any one of claims 1 to 3, wherein control for fluctuation is performed. The specific period is in the range of 50 to 700 μs,
The discharge lamp lighting device according to any one of claims 1 to 4, wherein the fluctuation amount of the control power value is within ± 20%.

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