JP2013164999A - Light source device, driving method of discharge lamp and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source device that can suppress blackening of a discharge lamp, maintain a distance between electrodes within an acceptable range and drive the discharge lamp, and further to provide a driving method of the discharge lamp and a projector.SOLUTION: A light source device 1 includes a discharge lamp 500, a driving device 200, voltage detecting means and time measuring means. The driving device 200 switches from a first alternating current supply section to a second alternating current supply section when an absolute value of an inter-electrode voltage reaches an upper limit value V1, and switches from the second alternating current supply section to the first alternating current supply section when the absolute value of the inter-electrode voltage reaches a lower limit value V2 or a period of the second alternating current supply section reaches a predetermined period T. In a case where the period of the second alternating current supply section reaches the predetermined period T and the second alternating current supply section is switched to the first alternating current supply section, where the absolute value of the inter-electrode voltage when the period of the second alternating current supply section reaches the period T is represented by V3, the driving device 200 changes the upper limit value V1 to a value larger than an initial value thereof by an increased amount ΔV represented by the following expression (1): ΔV=a*(V3-V2), where 0.1≤a≤1.

Description

  The present invention relates to a light source device, a discharge lamp driving method, and a projector.

As a light source of a projector, a discharge lamp (discharge lamp) such as a high-pressure mercury lamp or a metal halide lamp is used.
Such a discharge lamp is driven by, for example, a driving method that supplies a high-frequency alternating current as a driving current (see, for example, Patent Document 1). According to this driving method, discharge stability can be obtained, blackening and devitrification of the discharge lamp body can be prevented, and a reduction in the life of the discharge lamp can be suppressed.

However, in this driving method, when the discharge lamp is lit, an arc discharge is generated between the pair of electrodes, and the electrodes are at a high temperature. come.
For example, in the application of a projector, in order to improve the light utilization efficiency, it is preferable to maintain a narrow state between the electrodes and reduce the size of light emission. Spreading between the electrodes during lighting is not preferable because it reduces light utilization efficiency.

On the other hand, there is also a driving method in which an alternating current (direct current alternating current) having a rectangular waveform at a low frequency is supplied as a driving current (see, for example, Patent Document 2). According to this driving method, when the discharge lamp is lit, the protrusions are formed at the tip portions of the pair of electrodes, thereby maintaining a narrow state between the electrodes.
However, this driving method has a problem that the discharge lamp main body is blackened, devitrified, and the like, and the life of the discharge lamp is reduced.

Further, in Patent Document 3, a pair of alternating currents having a steady lighting frequency of 60 to 1000 Hz and alternating currents having a frequency lower than the steady lighting frequency and a low frequency of 5 to 200 Hz are alternately paired. There is disclosed a lighting device that supplies a discharge lamp to a discharge lamp.
However, in the lighting device described in Patent Document 3, the frequency of both the alternating current with a steady lighting frequency and the alternating current with a low frequency is too low, resulting in blackening or devitrification of the discharge lamp body, and the life of the discharge lamp. There is a problem that decreases. In addition, when the discharge lamp is lit, a protrusion is formed at the tip of the pair of electrodes, but the electrode is gradually consumed while it is lit for a long time, for example, several hundreds or thousands of hours. As a result, the protrusion cannot be enlarged to a predetermined size.

JP 2007-115534 A JP 2010-1114064 A JP 2010-123478 A

  An object of the present invention is to provide a light source device, a discharge lamp driving method, and a projector that can suppress the blackening of the discharge lamp, hold the distance between the electrodes within an allowable range, and drive the discharge lamp. It is in.

Such an object is achieved by the present invention described below.
A light source device of the present invention includes a light emitting container including a hollow portion in which a discharge medium is sealed, a discharge lamp having a pair of electrodes disposed so that the end portions face each other in the hollow portion, and
A driving device for supplying a driving current to the pair of electrodes;
Voltage detecting means for detecting a voltage between the electrodes of the pair of electrodes;
And a time measuring means for measuring time,
The driving device includes a first alternating current supply section for supplying a first alternating current having a frequency higher than 1 kHz to the pair of electrodes, and a second alternating current having a frequency of 1 kHz or less. Configured to alternately repeat the second AC current supply section supplied to
When the absolute value of the inter-electrode voltage of the pair of electrodes detected by the voltage detection means reaches the upper limit value V1, the drive device starts from the first alternating current supply section to the second alternating current supply section. To
In the second AC current supply section, the time measurement means measures the period of the second AC current supply section, and the absolute value of the voltage between the pair of electrodes detected by the voltage detection means is When the lower limit value V2 is reached or the period of the second alternating current supply section measured by the time measuring means reaches a predetermined period T, the first alternating current is supplied from the second alternating current supply section. Change to current supply section,
When the period of the second alternating current supply section reaches the period T and is changed from the second alternating current supply section to the first alternating current supply section, the second alternating current supply section When the absolute value of the inter-electrode voltage of the pair of electrodes when the period reaches the period T is V3, the upper limit value V1 is expressed by the following formula (1) from the initial value of the upper limit value V1. It is characterized in that it is configured to be changed to a value that is larger by the increment ΔV.
ΔV = a · (V3−V2) (1)
However, 0.1 ≦ a ≦ 1

As a result, the blackening of the discharge lamp can be suppressed in the first alternating current supply section, and the blackening of the discharge lamp blackened in the second alternating current supply section described later can be recovered.
On the other hand, in the second AC current supply section, a protrusion is formed at the tip portion of the pair of electrodes, and the protrusion becomes large, and thereby, between the electrodes of the pair of electrodes spread in the first AC current supply section. The distance can be reduced.
By alternately repeating the first AC current supply section and the second AC current supply section, blackening of the discharge lamp is suppressed, and the distance between the electrodes of the pair of electrodes is set within a permissible range. Hold and drive the discharge lamp.

  When the absolute value of the voltage between the electrodes of the pair of electrodes does not reach the lower limit value V2, but changes from the second alternating current supply section to the first alternating current supply section, the upper limit value V1 is set to its initial value. Therefore, the absolute value of the inter-electrode voltage of the pair of electrodes when switching from the second AC current supply section to the first AC current supply section at an early stage is changed. It is possible to prevent the discharge lamp from being unable to be driven because the value V3 coincides or approaches too much, and the life of the light source device can be extended.

In the light source device according to the aspect of the invention, the driving device may be configured such that the absolute value of the inter-electrode voltage of the pair of electrodes reaches the lower limit value V2, and the second alternating current supply section to the first alternating current supply section. When the upper limit value V1 is changed from the initial value, the upper limit value V1 is preferably set back to the initial value.
Thereby, the fluctuation | variation of a light quantity can be suppressed.

In the light source device of the present invention, the lower limit value V2 is an absolute value of the inter-electrode voltage of the pair of electrodes when the power supplied to the pair of electrodes reaches the rated power after the discharge lamp is turned on. It is preferable.
Thereby, the blackening of the discharge lamp can be suppressed more reliably, and the distance between the electrodes of the pair of electrodes can be maintained within the allowable range.
In the light source device of the present invention, the difference between the upper limit value V1 and the lower limit value V2 is preferably 15V or less.
Thereby, the fluctuation | variation of a light quantity can be suppressed.

In the light source device of the present invention, it is preferable that the amplitude of the first alternating current is decreased with time in the first alternating current supply section.
Thereby, the fluctuation | variation of a light quantity can be suppressed.
In the light source device of the present invention, it is preferable that the amplitude of the second alternating current is increased with time in the second alternating current supply section.
Thereby, the fluctuation | variation of a light quantity can be suppressed.

In the light source device of the present invention, it is preferable that the waveform of the first alternating current has a rectangular shape.
Thereby, the blackening of the discharge lamp can be suppressed more reliably.
In the light source device of the present invention, it is preferable that the waveform of the second alternating current has a rectangular shape.
Thereby, the blackening of the discharge lamp can be suppressed more reliably.

In the light source device of the present invention, it is preferable to suppress blackening of the discharge lamp by supplying the first alternating current.
Thereby, blackening of a discharge lamp can be suppressed.
In the light source device of the present invention, it is preferable that the distance between the pair of electrodes is reduced by supplying the second alternating current.
Thereby, the distance between the electrodes of the pair of electrodes widened in the first alternating current supply section can be reduced, and the distance between the electrodes can be maintained at a constant distance.

In the light source device of the present invention, the average value of the amplitude of the first AC current in the first AC current supply section and the average amplitude of the second AC current in the second AC current supply section The value is preferably the same.
Thereby, the light quantity in a 1st alternating current supply area and the light quantity in a 2nd alternating current supply area can be made the same.

A method for driving a discharge lamp according to the present invention is a method for driving a discharge lamp having a light emitting container including a cavity in which a discharge medium is sealed, and a pair of electrodes whose end portions are opposed to each other in the cavity. And
A first alternating current supply section for supplying a first alternating current having a frequency higher than 1 kHz to the pair of electrodes, and a second for supplying a second alternating current having a frequency of 1 kHz or less to the pair of electrodes. When the absolute value of the voltage between the electrodes of the pair of electrodes reaches the upper limit value V1, the second alternating current supply section is changed from the first alternating current supply section. When the absolute value of the inter-electrode voltage of the pair of electrodes reaches the lower limit value V2 or the period of the second AC current supply section reaches a predetermined period T, the second AC The current supply section is changed to the first AC current supply section, the period of the second AC current supply section reaches the period T, and the first AC current supply from the second AC current supply section. When changing to a section, the second intersection When the absolute value of the inter-electrode voltage of the pair of electrodes when the period of the current supply section reaches the period T is V3, the upper limit value V1 is less than the initial value of the upper limit value V1 (1) A drive current configured to be changed to a value larger by the increase amount ΔV shown in the equation is generated,
The driving current is supplied to the pair of electrodes.
ΔV = a · (V3−V2) (1)
However, 0.1 ≦ a ≦ 1

Thereby, the blackening of the discharge lamp can be suppressed, and the distance between the electrodes of the pair of electrodes can be maintained within the allowable range, and the discharge lamp can be driven.
When the absolute value of the voltage between the electrodes of the pair of electrodes does not reach the lower limit value V2, but changes from the second alternating current supply section to the first alternating current supply section, the upper limit value V1 is the initial value. Therefore, the upper limit value V1 and the voltage between the electrodes of the pair of electrodes when switching from the second alternating current supply section to the first alternating current supply section at an early stage are changed. It can be prevented that the absolute value V3 coincides with or approaches the absolute value V3 and the discharge lamp cannot be driven, and the life of the light source device can be extended.

A projector according to the present invention includes the light source device.
Thereby, the blackening of the discharge lamp is suppressed, the distance between the electrodes of the pair of electrodes can be maintained within the allowable range, and the discharge lamp can be driven, thereby reducing the power consumption, A stable and good image can be displayed.
When the absolute value of the voltage between the electrodes of the pair of electrodes does not reach the lower limit value V2, but changes from the second alternating current supply section to the first alternating current supply section, the upper limit value V1 is set to its initial value. Therefore, the absolute value of the inter-electrode voltage of the pair of electrodes when switching from the second AC current supply section to the first AC current supply section at an early stage is changed. It is possible to prevent the discharge lamp from being unable to be driven because the value V3 coincides or approaches too much, and the life of the light source device can be extended.

It is sectional drawing (block diagram is also included) which shows embodiment of the light source device of this invention. It is sectional drawing which shows the discharge lamp of the light source device shown in FIG. It is a block diagram which shows the light source device shown in FIG. It is a figure which shows the drive current of the light source device shown in FIG. It is a figure which shows the absolute value of the voltage between electrodes of the light source device shown in FIG. It is a flowchart which shows the control operation of the light source device shown in FIG. It is a figure which shows typically embodiment of the projector of this invention.

Hereinafter, a light source device, a discharge lamp driving method, and a projector of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
<Light source device>
1 is a cross-sectional view (including a block diagram) showing an embodiment of a light source device of the present invention, FIG. 2 is a cross-sectional view showing a discharge lamp of the light source device shown in FIG. 1, and FIG. 3 is shown in FIG. 4 is a block diagram showing the light source device, FIG. 4 is a diagram showing the drive current of the light source device shown in FIG. 1, FIG. 5 is a diagram showing the absolute value of the interelectrode voltage of the light source device shown in FIG. 1, and FIG. 2 is a flowchart showing a control operation of the light source device shown in FIG. In FIG. 2, the sub-reflecting mirror is not shown.

  As shown in FIGS. 1 and 3, the light source device 1 includes a light source unit 110 having a discharge lamp 500 and a light source device main body 100. The light source device main body 100 includes a discharge lamp driving device (driving device) 200 for driving the discharge lamp 500 and a detector (voltage detection means) for detecting a voltage between electrodes of a pair of electrodes 610 and 710 (to be described later) of the discharge lamp 500. 35 and a time measuring device (time measuring means) 36 for measuring time. The light source device 1 also includes a cooling device (not shown) that cools a light emitting container 511 described later of the discharge lamp 500. The discharge lamp 500 receives electric power from the discharge lamp driving device 200 to discharge and emit light.

The light source unit 110 includes a discharge lamp 500, a main reflecting mirror 112 having a concave reflecting surface, and a collimating lens 114 that makes emitted light substantially parallel. The main reflecting mirror 112 is disposed on one end side of the discharge lamp 500, and the collimating lens 114 is disposed on the other end side of the discharge lamp 500. The main reflecting mirror 112 and the discharge lamp 500 are bonded with an inorganic adhesive 116. Further, the main reflecting mirror 112 has a surface (inner surface) on the discharge lamp 500 side as a reflecting surface, and this reflecting surface forms a spheroidal surface in the illustrated configuration.
Note that the shape of the reflecting surface of the main reflecting mirror 112 is not limited to the above shape, and other examples include a rotating paraboloid. Further, when the reflecting surface of the main reflecting mirror 112 is a rotating paraboloid, the collimating lens 114 can be omitted if the light emitting part of the discharge lamp 500 is arranged at the so-called focal point of the rotating paraboloid.

  The discharge lamp 500 includes a discharge lamp main body 510 and a sub-reflecting mirror 520 having a concave reflecting surface. The sub-reflecting mirror 520 is disposed on the opposite side of the main reflecting mirror 112 of the discharge lamp main body 510, that is, on the parallelizing lens 114 side, and at a position separated from the outer peripheral surface of the discharge lamp main body 510 by a predetermined distance. The discharge lamp main body 510 and the sub-reflecting mirror 520 are bonded by an inorganic adhesive 522 provided between the discharge lamp main body 510 and the sub-reflecting mirror 520. Further, in the sub-reflecting mirror 520, the surface (inner surface) on the discharge lamp 500 side is a reflecting surface, and this reflecting surface is a spherical surface in the illustrated configuration.

At the center of the discharge lamp main body 510, a light emitting container 511 including a discharge space (hollow part) 512 hermetically sealed with a discharge medium described later is formed. At least a portion corresponding to the discharge space 512 of the discharge lamp main body 510 has light transmittance. Examples of the constituent material of the discharge lamp main body 510 include glass such as quartz glass and light-transmitting ceramics.
The discharge lamp main body 510 is provided with a pair of electrodes 610 and 710, a pair of conductive connection members 620 and 720, and a pair of electrode terminals 630 and 730. The electrode 610 and the electrode terminal 630 are electrically connected by a connection member 620. Similarly, the electrode 710 and the electrode terminal 730 are electrically connected by a connection member 720.

Each electrode 610, 710 is accommodated in the discharge space 512. In other words, the electrodes 610 and 710 are arranged such that their tip portions are spaced apart from each other by a predetermined distance in the discharge space 512 of the discharge lamp main body 510 and face each other.
The distance between the electrodes, which is the shortest distance between the electrode 610 and the electrode 710, is preferably 1 μm or more and 5 mm or less, and more preferably 0.5 mm or more and 1.5 mm or less.

  As shown in FIG. 2, the electrode 610 includes a core rod 612, a coil portion 614, and a main body portion 616. The electrode 610 is formed by winding a wire rod of an electrode material (tungsten or the like) around a core rod 612 to form a coil portion 614 before heating and melting the formed coil portion 614 before being enclosed in the discharge lamp main body 510. It is formed by doing. As a result, a body portion 616 having a large heat capacity is formed on the tip side of the electrode 610. Similarly to the electrode 610, the electrode 710 also includes a core rod 712, a coil portion 714, and a main body portion 716, and is formed in the same manner as the electrode 610.

In the state where the discharge lamp 500 has never been lit, the main body portions 616 and 716 are not formed with protrusions 618 and 718. However, if the discharge lamp 500 is lit even once under the conditions described later, the main body portion Protrusions 618 and 718 are formed at the tips of 616 and 716, respectively. The protrusions 618 and 718 are maintained while the discharge lamp 500 is turned on, and are also maintained after the lamp is turned off.
In addition, as a constituent material of each electrode 610,710, high melting point metal materials, such as tungsten, etc. are mentioned, for example.
Further, a discharge medium is enclosed in the discharge space 512. The discharge medium includes, for example, a discharge start gas, a gas that contributes to light emission, and the like. Further, the discharge medium may contain other gas.

Examples of the discharge starting gas include noble gases such as neon, argon, and xenon. Examples of the gas that contributes to light emission include mercury, vaporized metal halide, and the like. Examples of the other gas include a gas having a function of preventing blackening. Examples of the gas having a function of preventing blackening include a halogen (for example, bromine), a halogen compound (for example, hydrogen bromide), or a vaporized product thereof.
The atmospheric pressure in the discharge lamp main body 510 when the discharge lamp is lit is preferably 0.1 atm or more and 300 atm or less, and more preferably 50 atm or more and 300 atm or less.

  As described above, one electrode terminal 730 of the discharge lamp 500 is electrically connected to the discharge lamp main body 510 on the side opposite to the main reflecting mirror 112 via the electrode 710 and the connection member 720 and led out. Yes. Similarly, the other electrode terminal 630 of the discharge lamp 500 is electrically connected to the discharge lamp main body 510 on the main reflecting mirror 112 side via the electrode 610 via the connecting member 620, and the back side of the main reflecting mirror 112. Has been derived. The electrode terminals 630 and 730 of the discharge lamp 500 are connected to the output terminals of the discharge lamp driving device 200, respectively. The discharge lamp driving device 200 includes a high-frequency alternating current (AC power) in the discharge lamp 500. A drive current (drive power) is supplied. In other words, the discharge lamp driving device 200 supplies power to the discharge lamp 500 by supplying the drive current to the electrodes 610 and 710 via the electrode terminals 630 and 730. When the drive current is supplied to the electrodes 610 and 710, arc discharge (arc AR) is generated between the tips of the pair of electrodes 610 and 710 in the discharge space 512. Light (discharge light) generated by the arc discharge is radiated in all directions from the generation position (discharge position) of the arc AR. As described above, the sub-reflecting mirror 520 is disposed so as to cover the curved surface on the side opposite to the side on which the main reflecting mirror 112 is disposed with respect to the discharge lamp main body 510, and thus in the direction of the one electrode 710. The emitted light is reflected toward the main reflecting mirror 112. In this way, by reflecting the light emitted in the direction of the electrode 710 toward the main reflecting mirror 112, the light emitted in the direction of the electrode 710 can be effectively used. In the present embodiment, the discharge lamp 500 includes the sub-reflecting mirror 520, but the discharge lamp 500 may be configured not to include the sub-reflecting mirror 520.

Next, the light source device main body 100 will be described.
As shown in FIG. 3, the discharge lamp driving device 200 includes a direct current generator 31 that generates a direct current, a polarity switch 32 that switches between positive and negative polarities of the direct current output from the direct current generator 31, and a control. Unit (control means) 33, and the polarity switch 32 switches the polarity of the direct current to generate an alternating current having a predetermined frequency (direct current alternating current). The alternating current is used as a drive current for the discharge lamp 500. This is a device that supplies a pair of electrodes 610 and 710. The direct current generator 31, the polarity switch 32, and the control unit 33 constitute a first alternating current supply unit and a second alternating current supply unit.

  The control unit 33 controls the operation of the entire discharge lamp driving device 200 such as the direct current generator 31 and the polarity switch 32 and the operation of the time measuring device 36. The direct current generator 31 can adjust the current value as its output, and the current value of the direct current generator 31 is adjusted under the control of the control unit 33. The timing of switching the polarity of the direct current in the polarity switch 32 is adjusted by the control of the control unit 33.

  Further, a detection result of a detector (interelectrode distance detection unit) 35 described later provided separately on the output side of the discharge lamp driving device 200 (between the electrode terminals 630 and 730 of the discharge lamp 500 and the discharge lamp driving device 200). Is input to the control unit 33. In the present embodiment, the detector 35 is provided separately from the discharge lamp driving device 200, but may be configured to be incorporated in the discharge lamp driving device 200. Further, the time measuring device 36 is provided separately from the discharge lamp driving device 200, but may be configured to be incorporated in the discharge lamp driving device 200. Further, an amplifier (not shown) may be provided, for example, at a subsequent stage of the polarity switch 32, that is, between the polarity switch 32 and the detector 35.

As shown in FIGS. 4 and 5, the discharge lamp driving device 200 generates a first alternating current (high-frequency alternating current) and supplies the first alternating current to a pair of electrodes 610 and 710. A section 41 and a second alternating current supply section 42 that generates a second alternating current having a frequency lower than that of the first alternating current (a low-frequency alternating current) and supplies the second alternating current to the pair of electrodes 610 and 710. The polarity switch 32 switches the polarity of the direct current generated by the direct current generator 31 so as to be repeated alternately. That is, an alternating current, which is a driving current for driving a discharge lamp, in which the first alternating current supply section 41 and the second alternating current supply section 42 are alternately repeated is generated and output. The drive current output from the discharge lamp driving device 200 is supplied to a pair of electrodes 610 and 710 of the discharge lamp 500.
Thereby, as described above, arc discharge occurs between the tip portions of the pair of electrodes 610 and 710, and the discharge lamp 500 is turned on. In addition, while the discharge lamp 500 is lit, the cooling device operates to cool the light emitting container 511.

  Here, in the light source device 1, the discharge lamp 500 is lit using a driving current under the conditions described later. Therefore, when the discharge lamp 500 is lit, the temperature of the electrodes 610 and 710 varies. The projections 618 and 718 are formed at the tip portions of the electrodes 610 and 710, respectively, so that the projections 618 and 718 can be maintained, the blackening of the discharge lamp 500 can be prevented, and the life can be extended. it can.

  That is, in the second alternating current supply section 42, a second alternating current described later is supplied to the electrodes 610 and 710, so that protrusions 618 and 718 are formed at the tips of the electrodes 610 and 710, and the protrusions 618 and 718. As a result, the distance between the electrodes of the pair of electrodes 610 and 710 widened in the first alternating current supply section 41 described later can be reduced (reduced).

  Specifically, in the second alternating current supply section 42, first, in the section where the polarity of the second alternating current is positive, the temperatures of the electrodes 610 and 710 are increased, respectively. A part of the part is melted, and the melted electrode material gathers at the tips of the electrodes 610 and 710 due to surface tension. On the other hand, in the section where the polarity of the second alternating current is negative, the temperature of the electrodes 610 and 710 decreases, so that the molten electrode material is solidified. The protrusions 618 and 718 grow by repeating such a state in which the molten electrode material is collected at the tip portions of the electrodes 610 and 710 and a state in which the molten electrode material is solidified.

Then, as will be described later, by switching between the first alternating current supply section 41 and the second alternating current supply section 42 and restricting the interelectrode distance within a predetermined range, the interelectrode distance is prevented from spreading. It is possible to maintain a narrow state between the electrodes. Thereby, the discharge lamp 500 can be driven efficiently.
However, in the second AC current supply section 42, the discharge lamp 500 is blackened.

On the other hand, in the first alternating current supply section 41, since a first alternating current described later is supplied to the electrodes 610 and 710, blackening of the discharge lamp 500 is suppressed, and in the second alternating current supply section 42, The blackening of the blackened discharge lamp 500 can be recovered.
However, in the first alternating current supply section 41, the protrusions 618 and 718 formed at the tip portions of the electrodes 610 and 710 in the second alternating current supply section 42 are reduced, thereby increasing the distance between the electrodes.

By alternately repeating the first alternating current supply section 41 and the second alternating current supply section 42 as described above, the blackening of the discharge lamp 500 is suppressed, and the distance between the electrodes is maintained within the allowable range. The discharge lamp 500 can be driven.
Here, the rated power of the discharge lamp 500 is appropriately set depending on the application and the like, and is not particularly limited. However, the rated power is preferably 10 W or more and 5 kW or less, and more preferably 100 W or more and 500 W or less.

  Further, the frequency of the first alternating current is greater than 1 kHz. The frequency of the first alternating current is preferably greater than 1 kHz and 10 GHz or less, preferably greater than 1 kHz and 100 kHz or less, more preferably 3 MHz or more and 10 GHz or less, or 3 kHz or more and 100 kHz or less, or It is more preferably 3 MHz or more and 3 GHz or less, and particularly preferably 5 kHz or more and 100 kHz or less, or 3 MHz or more and 3 GHz or less. Further, the frequency of the first alternating current is preferably 3 kHz or more and 100 kHz or less, and more preferably 5 kHz or more and 100 kHz or less.

  When the electrodes 610 and 710 operate as anodes, the electrode temperature is higher than when the electrodes 610 and 710 operate as cathodes respectively. However, by setting the frequency of the first alternating current to be higher than 1 kHz, the first The fluctuation of the electrode temperature within one cycle of the alternating current can be prevented, the blackening of the discharge lamp 500 is suppressed, and the blackening of the discharge lamp 500 blackened in the second alternating current supply section 42 is suppressed. Can be recovered.

However, if the frequency of the first alternating current is 1 kHz or less, the temperature of the electrodes 610 and 710 varies and the discharge lamp 500 is blackened every cycle of the first alternating current.
In addition, if the frequency of the first alternating current is greater than 10 GHz, the cost is high.
If the frequency of the first alternating current is larger than 100 kHz and smaller than 3 MHz, the discharge becomes unstable due to the acoustic resonance effect depending on other conditions.

The frequency of the second alternating current is 1 kHz or less. The frequency of the second alternating current is preferably 500 Hz or less, more preferably 10 Hz or more and 500 Hz or less, and further preferably 30 Hz or more and 300 Hz or less.
When the frequency of the second alternating current exceeds 1 kHz, the protrusions 618 and 718 are not formed. If the frequency of the second alternating current is smaller than 10 Hz, the protrusions 618 and 718 are melted and crushed depending on other conditions, and blackening is more likely to occur.

  In the first alternating current supply section 41, the amplitude of the first alternating current is gradually decreased with time. That is, in the first AC current supply section 41, the protrusions 618 and 718 are reduced, the distance between the electrodes is increased, and the voltage between the electrodes (absolute value of the voltage between the electrodes) gradually increases with time. The amplitude of the first alternating current is gradually decreased over time so that the power supplied to 500 becomes constant. Thereby, the light quantity can be made constant.

Conversely, in the second alternating current supply section 42, the amplitude of the second alternating current is gradually increased over time. That is, in the second AC current supply section 42, the protrusions 618 and 718 are increased, the distance between the electrodes is decreased, and the voltage between the electrodes (absolute value of the voltage between the electrodes) gradually decreases with time. The amplitude of the second alternating current is gradually increased with time so that the power supplied to 500 becomes constant. Thereby, the light quantity can be made constant.
The waveforms of the first alternating current and the first alternating current each have a rectangular shape (rectangular wave). Thereby, the blackening of the discharge lamp 500 can be suppressed more reliably.
Note that the waveforms of the first alternating current and the first alternating current are not limited to rectangular shapes, and may be, for example, wave shapes.

Further, when the period of the first alternating current is a1 and the period of the section 43 in which the current polarity is positive is b1, the ratio b1 / a1 (duty ratio) between the period a1 and the period b1 is 10% or more and 90% or less. Preferably, it is 20% or more and 80% or less, and more preferably 50%.
Further, when the period of the second alternating current is a2 and the period of the section 44 where the current polarity is positive is b2, the ratio b2 / a2 (duty ratio) between the period a2 and the period b2 is 10% or more and 90% or less. Preferably, it is 20% or more and 80% or less, and more preferably 50%. Accordingly, the protrusions 618 and 718 can be formed on the electrodes 610 and 710 symmetrically to each other.
In addition, when the light amount in the first alternating current supply section 41 and the light amount in the second alternating current supply section 42 are made the same, the magnitude of the first alternating current in the first alternating current supply section 41. And the average value of the magnitude of the second alternating current in the second alternating current supply section 42 are set to the same value.

  In the present embodiment, a voltmeter is used as the detector 35 of the light source device 1. The detector 35 detects the interelectrode voltage of the pair of electrodes 610 and 710 of the discharge lamp 500, and uses the detected interelectrode voltage for driving control of the discharge lamp 500, as will be described later. This interelectrode voltage is a value corresponding to the interelectrode distance. Therefore, the interelectrode distance is obtained indirectly by obtaining the interelectrode voltage. In addition, the distance between electrodes is so long that the voltage between electrodes is large. Moreover, in this embodiment, since the voltage between electrodes is measured with a voltmeter, it is preferable to apply when the frequency of a drive current, ie, the frequency of a 1st alternating current, is less than 1 MHz.

  In this light source device 1, in the discharge lamp driving device 200, the threshold value of the absolute value of the interelectrode voltage of the pair of electrodes 610 and 710, that is, the upper limit value V1 and the lower limit value V2 of the allowable range of the absolute value of the interelectrode voltage are set. Has been. Further, the threshold value of the period of the second alternating current supply section 42 of the drive current is set to the period T. The upper limit value V1, the lower limit value V2, and the period T will be described later.

During the lighting of the discharge lamp 500, the detector 35 detects the interelectrode voltage of the pair of electrodes 610 and 710, and the detected interelectrode voltage is sent to the control unit 33. In addition, during the lighting of the discharge lamp 500, the control unit 33 measures the period of the second alternating current supply section 42 using the time measuring device 36.
Then, as shown in FIG. 5, the control unit 33, according to the detected interelectrode voltage and the measured period of the second alternating current supply section 42, the first alternating current supply section 41, The second alternating current supply section 42 is switched.

  That is, in the first alternating current supply section 41, the control unit 33 detects the interelectrode voltage with the detector 35, and when the absolute value of the interelectrode voltage reaches the upper limit value V1, the control section 33 starts from the first alternating current supply section 41. The second AC current supply section 42 is changed. In addition, in the second alternating current supply section 42, the control unit 33 detects the interelectrode voltage by the detector 35, and measures the period of the second alternating current supply section 42 by the time measuring device 36. When the absolute value of the voltage becomes the lower limit value V2 or the period of the second AC current supply section 42 becomes the period T, the second AC current supply section 42 is changed to the first AC current supply section 41. Thereby, the distance between electrodes can be limited within a predetermined allowable range.

  In addition, when the period of the second alternating current supply section 42 becomes the period T and the control unit 33 changes from the second alternating current supply section 42 to the first alternating current supply section 41, the control section 33 When the absolute value of the interelectrode voltage when the period of the current supply section 42 becomes the period T is V3, the upper limit value V1 is increased by the following expression (1) from the initial value of the upper limit value V1. Change to a value larger by ΔV.

ΔV = a · (V3−V2) (1)
However, in the above formula (1), 0.1 ≦ a ≦ 1.
As a result, the upper limit value V1 and the absolute value V3 of the inter-electrode voltage when switching from the second alternating current supply section 42 to the first alternating current supply section 41 are coincident or too close to each other at an early stage. Can be prevented from becoming impossible to drive, and the life of the light source device 1 can be extended.

Here, the coefficient a in the above formula (1) is preferably 0.1 ≦ a <1, and more preferably 0.5 ≦ a ≦ 0.9.
Thereby, the increase amount per unit time of the upper limit value V1 per unit time of the absolute value V3 of the interelectrode voltage when the second AC current supply section 42 is switched to the first AC current supply section 41. Since it becomes smaller than the increase amount, it can be prevented that the inter-electrode voltage becomes too high at an early stage and the illuminance is lowered, and the life of the light source device 1 can be extended.

Further, when the absolute value of the interelectrode voltage becomes the lower limit value V2 and the control unit 33 changes from the second alternating current supply section 42 to the first alternating current supply section 41, the upper limit value V1 is changed from the initial value. When it is changed, the upper limit value V1 is returned to the initial value. Thereby, the light quantity can be made constant.
Further, the initial value and the lower limit value V2 of the upper limit value V1 are not particularly limited, and are appropriately set according to various conditions. In the present embodiment, the lower limit value V2 is set to the absolute value of the interelectrode voltage when the power supplied to the pair of electrodes 610 and 710 reaches the rated power after the discharge lamp 500 is turned on. Needless to say, the lower limit value V2 may be set to other values.

The initial value of the upper limit value V1 is preferably set so that the difference from the lower limit value V2 is 15V or less, more preferably 1V or more and 10V or less, and more preferably 1V or more and 5V. More preferably, it is set to be as follows. Thereby, the light quantity can be made constant.
The period T is not particularly limited and is appropriately set according to various conditions, but is preferably 1 minute or longer and 60 minutes or shorter, and more preferably 5 minutes or longer and 30 minutes or shorter. As a result, the protrusions 618 and 718 can be grown more reliably, and the distance between the electrodes can be maintained within the allowable range.

  The period of the first AC current supply section 41 is determined according to the upper limit value V1, the lower limit value V2, and the like. The period of the second AC voltage supply section is less than the period T and the upper limit value V1. The period of the first alternating current supply section 41 is preferably longer than the period of the second alternating current supply section 42, although it is determined according to the lower limit value V2 and the like. That is, when the period of the first AC current supply section 41 is A and the period of the second AC current supply section 42 is B, A / B is preferably larger than 1, and more preferably 2 or more. preferable. Thereby, the blackening of the discharge lamp 500 can be suppressed more reliably.

In particular, A / B is preferably greater than 1 and 50 or less, more preferably 2 or more and 50 or less, and even more preferably 2 or more and 10 or less. As a result, it is possible to achieve both suppression of blackening of the discharge lamp 500 and keeping the interelectrode distance within an allowable range, and it is possible to suppress blackening of the discharge lamp 500 more reliably.
In addition, the period of the 2nd alternating current supply area 42 may be longer than the period of the 1st alternating current supply area 41, and the period of the 1st alternating current supply area 41 and the 2nd alternating current supply area The period of 42 may be the same.

The period A is preferably 10 minutes or longer and 3 hours or shorter, and more preferably 10 minutes or longer and 1 hour or shorter. Thereby, the blackening of the discharge lamp 500 can be suppressed more reliably, and the blackening of the discharge lamp 500 blackened in the second alternating current supply section 42 can be recovered.
The period B is preferably 1 minute or longer and 60 minutes or shorter, and more preferably 1 minute or longer and 10 minutes or shorter. Thereby, the distance between electrodes can be more reliably maintained at a distance within the allowable range.

Next, a control operation of the discharge lamp driving device 200 of the light source device 1 will be described based on FIG.
First, the drive current is set in the first alternating current supply section 41, the first alternating current is supplied to the pair of electrodes 610 and 710, and the discharge lamp 500 is turned on (step S101). Accordingly, the protrusions 618 and 718 become smaller, and the voltage between the electrodes gradually increases. As described above, the first alternating current is gradually decreased so that the supplied power becomes constant.

Next, the interelectrode voltage is detected (step S102), and it is determined whether or not the detected absolute value of the interelectrode voltage has reached the upper limit value V1 (step S103).
In step S103, when the absolute value of the interelectrode voltage has not reached the upper limit value V1, the process returns to step S102, and step S102 and subsequent steps are executed again.
In step S103, when the absolute value of the interelectrode voltage reaches the upper limit value V1, the drive current is set to the second alternating current supply section 42, and the second alternating current is set to the pair of electrodes 610, 710. (Step S104). Accordingly, the protrusions 618 and 718 become larger, and the voltage between the electrodes gradually decreases. As described above, the second alternating current is gradually increased so that the supplied power becomes constant.

Next, time measurement is started (step S105), the interelectrode voltage is detected (step S106), and it is determined whether or not the absolute value of the detected interelectrode voltage has reached the lower limit value V2 (step S107). .
In step S107, when the absolute value of the interelectrode voltage has not reached the lower limit value V2, it is determined whether or not the period of the second alternating current supply section 42 has reached the period T (step S108).

In step S108, when the period of the 2nd alternating current supply area 42 has not reached the period T, it returns to step S106 and performs again after step S106.
In step S106, when the period of the second alternating current supply section 42 reaches the period T, the interelectrode voltage is detected (step S109), and the absolute value V3 and the lower limit value V2 of the interelectrode voltage are detected. Is added to the above equation (1), the increase amount ΔV is obtained, the increase amount ΔV is added to the initial value of the upper limit value V1, and a new upper limit value V1 larger by the increase amount ΔV than the initial value of the upper limit value V1 is obtained. Obtained (step S110).
Next, the upper limit value V1 is changed to the new upper limit value V1 (step S111), the process returns to step S101, and step S101 and subsequent steps are executed again.

If the absolute value of the interelectrode voltage reaches the lower limit value V2 in step S107, it is determined whether or not the upper limit value V1 is an initial value (step S112).
If the upper limit value V1 is the initial value in step S112, the process returns to step S101, and step S101 and subsequent steps are executed again.
If the upper limit value V1 is not the initial value in step S112, the upper limit value V1 is returned to the initial value, the process returns to step S101, and step S101 and subsequent steps are executed again. As a result, the absolute value of the interelectrode voltage is maintained within the allowable range, and the interelectrode distance is maintained within the allowable range.
As described above, according to the light source device 1, it is possible to suppress the blackening of the discharge lamp 500 and extend the life. Further, the projections 618 and 718 are formed on the electrodes 610 and 710, and the distance between the electrodes can be maintained within the allowable range, and the discharge lamp 500 can be driven efficiently.

  As mentioned above, although the light source device and the discharge lamp driving method of the present invention have been described based on the illustrated embodiment, the present invention is not limited to this, and the configuration of each part is an arbitrary one having the same function. It can be replaced with that of the configuration. In addition, any other component may be added to the present invention.

<Projector>
FIG. 7 is a diagram schematically showing an embodiment of the projector of the present invention.
A projector 300 shown in FIG. 7 includes a light source device 1 described above, an illumination optical system having integrator lenses 302 and 303, a color separation optical system (light guide optical system), and a liquid crystal light corresponding to red (for red). A bulb 84, a liquid crystal light valve 85 corresponding to green (for green), a liquid crystal light valve 86 corresponding to blue (for blue), a dichroic mirror surface 811 reflecting only red light, and reflecting only blue light A dichroic prism (color combining optical system) 81 on which a dichroic mirror surface 812 is formed, and a projection lens (projection optical system) 82.

The color separation optical system includes mirrors 304, 306, and 309, a dichroic mirror 305 that reflects blue light and green light (transmits only red light), a dichroic mirror 307 that reflects only green light, and a dichroic that reflects only blue light. A mirror 308 and condensing lenses 310, 311, 312, 313, and 314 are included.
The liquid crystal light valve 85 includes a liquid crystal panel 16, a first polarizing plate (not shown) disposed on the incident surface side of the liquid crystal panel 16, and a second polarizing plate disposed on the output surface side of the liquid crystal panel 16. (Not shown). The liquid crystal light valves 84 and 86 have the same configuration as the liquid crystal light valve 85. The liquid crystal panels 16 of the liquid crystal light valves 84, 85 and 86 are respectively connected to drive circuits (not shown).
In the projector 300, the liquid crystal light valves 84, 85, 86 and the drive circuit constitute a main part of a modulation device that modulates the light emitted from the light source device 1 based on image information. The main part of the projection apparatus which projects the light modulated by the modulation apparatus is comprised.

Next, the operation of the projector 300 will be described.
First, white light (white light flux) emitted from the light source device 1 passes through the integrator lenses 302 and 303. The light intensity (luminance distribution) of this white light is made uniform by the integrator lenses 302 and 303.
The white light transmitted through the integrator lenses 302 and 303 is reflected to the left side in FIG. 7 by the mirror 304, and blue light (B) and green light (G) of the reflected light are respectively reflected by the dichroic mirror 305 in FIG. The red light (R) is reflected downward and passes through the dichroic mirror 305.

The red light transmitted through the dichroic mirror 305 is reflected downward in FIG. 7 by the mirror 306, and the reflected light is shaped by the condenser lens 310 and enters the liquid crystal light valve 84 for red.
Green light out of blue light and green light reflected by the dichroic mirror 305 is reflected to the left side in FIG. 7 by the dichroic mirror 307, and the blue light passes through the dichroic mirror 307.

The green light reflected by the dichroic mirror 307 is shaped by the condenser lens 311 and enters the green liquid crystal light valve 85.
Further, the blue light transmitted through the dichroic mirror 307 is reflected by the dichroic mirror 308 to the left side in FIG. 7, and the reflected light is reflected by the mirror 309 to the upper side in FIG. The blue light is shaped by the condenser lenses 312, 313 and 314 and enters the blue liquid crystal light valve 86.

As described above, the white light emitted from the light source device 1 is separated into the three primary colors of red, green, and blue by the color separation optical system, and is guided to the corresponding liquid crystal light valves 84, 85, and 86, respectively, and enters. .
At this time, each pixel of the liquid crystal panel 16 of the liquid crystal light valve 84 is switching-controlled (on / off) by a drive circuit that operates based on the image signal for red, and the liquid crystal panel 16 of the liquid crystal light valve 85 is controlled. Each pixel is controlled by a drive circuit that operates based on a green image signal, and each pixel of the liquid crystal panel 16 of the liquid crystal light valve 86 is controlled by a drive circuit that operates based on a blue image signal. The switching is controlled.
Thereby, red light, green light, and blue light are modulated for each color by the liquid crystal light valves 84, 85, and 86, respectively, and a red image, a green image, and a blue image are formed.

The red image formed by the liquid crystal light valve 84, that is, the red light from the liquid crystal light valve 84, is incident on the dichroic prism 81 from the incident surface 813, reflected by the dichroic mirror surface 811 to the left in FIG. The light passes through the mirror surface 812 and exits from the exit surface 816.
Further, the green image formed by the liquid crystal light valve 85, that is, the green light from the liquid crystal light valve 85, enters the dichroic prism 81 from the incident surface 814, and passes through the dichroic mirror surfaces 811 and 812, respectively. The light exits from the exit surface 816.

Further, the blue image formed by the liquid crystal light valve 86, that is, the blue light from the liquid crystal light valve 86 is incident on the dichroic prism 81 from the incident surface 815, and is reflected to the left side in FIG. 7 by the dichroic mirror surface 812. Then, the light passes through the dichroic mirror surface 811 and exits from the exit surface 816.
Thus, the light of each color from the liquid crystal light valves 84, 85 and 86, that is, the images formed by the liquid crystal light valves 84, 85 and 86 are synthesized by the dichroic prism 81, thereby forming a color image. The This image is projected (enlarged projection) onto the screen 320 installed at a predetermined position by the projection lens 82.
As described above, according to the projector 300, since the light source device 1 described above is included, power consumption can be reduced, and a stable and good image can be displayed.

Next, specific examples of the present invention will be described.
Example 1
As shown in FIG. 1, a light source device having the following configuration was produced.
When the discharge lamp is turned on, when the absolute value of the interelectrode voltage reaches the upper limit value V1 in the first alternating current supply section, the first alternating current supply section is changed to the second alternating current supply section. In the second AC current supply section, when the absolute value of the interelectrode voltage reaches the lower limit value V2 or when the period of the second AC current supply section reaches the period T, the second AC current supply section starts from the second AC current supply section. Control to change to the first alternating current supply section 41 was performed. This is designated as control 1.

In addition, when the period of the second alternating current supply section reaches the period T and is changed from the second alternating current supply section to the first alternating current supply section, the period of the second alternating current supply section is the period. Control where the upper limit value V1 is changed to a value larger than the initial value of the upper limit value V1 by the increase amount ΔV shown in the equation (1), where V3 is the absolute value of the interelectrode voltage when T is reached. Went. This is referred to as control 2.
When the absolute value of the interelectrode voltage reaches the lower limit value V2 and is changed from the second alternating current supply section 42 to the first alternating current supply section 41, the upper limit value V1 is changed from the initial value. In this case, control was performed to return the upper limit value V1 to the initial value. This is control 3.

Discharge lamp body material: Quartz glass Inclusion in the discharge lamp body: Argon, mercury, methyl bromine Atmospheric pressure in the discharge lamp body: 200 atm
Electrode constituent material: Tungsten Electrode distance: 1.1 mm
Rated power: 200W
Frequency of first alternating current (high frequency current): 5 kHz
Duty ratio of first alternating current (b1 / a1): 50%
Waveform of the first alternating current: rectangular shape Frequency of the second alternating current (low frequency current): 135 Hz
Duty ratio of second AC current (b2 / a2): 50%
Waveform of second alternating current: rectangular shape Driving current: current is controlled so that electric power is 200 W Initial value of upper limit value V1 of absolute value of interelectrode voltage: 73V
Lower limit of absolute value of voltage between electrodes V2: 68V
Period T: 30 minutes Coefficient a in formula (1): 0.8

(Comparative Example 1)
Among the controls 1 to 3 in the first embodiment, a light source device similar to that of the first embodiment was created except that the control 1 was performed and the controls 2 and 3 were not performed.
[Evaluation]
Each of the light source devices of Example 1 and Comparative Example 1 was used as a light source device of a projector, and the projector was continuously turned on to check the change in illuminance on the screen.
As a result, in Example 1, since blackening did not occur from the beginning, devitrification did not occur, and since the electrode was gradually consumed, the illuminance after 10,000 hours from the start of lighting was It was 50% of the illuminance.
On the other hand, in Comparative Example 1, blackening did not occur until 1000 hours from the start of lighting, and the illuminance was similar to that in Example 1. Thereafter, driving within the lamp control range was caused by electrode consumption. The illuminance declined quickly from there, and it reached 50% of the initial illuminance after 6000 hours from the start of lighting.

  DESCRIPTION OF SYMBOLS 1 ... Light source device 31 ... DC current generator 32 ... Polarity switch 33 ... Control part 35 ... Detector 36 ... Time measuring device 41 ... 1st alternating current supply area 42 ... 2nd alternating current supply area 43, 44 ... Section 100: light source device main body 110: light source unit 112 ... main reflecting mirror 114 ... collimating lens 116 ... inorganic adhesive 200 ... discharge lamp driving device 500 ... discharge lamp 510 ... discharge lamp main body 511 ... light emitting vessel 512 ... discharge space 520 ... Sub-reflection mirror 522 ... Inorganic adhesive 610, 710 ... Electrode 612, 712 ... Core rod 614, 714 ... Coil part 616, 716 ... Body part 618, 718 ... Projection 620, 720 ... Connection member 630, 730 ... Electrode terminal 16 ... Liquid crystal panel 81 ... Dichroic prism 811, 812 ... Dichroic mirror surface 813 to 815 Incident surface 816 ... Output surface 82 ... Projection lens 84 to 86 ... Liquid crystal light valve 300 ... Projector 302, 303 ... Integrator lens 304, 306, 309 ... Mirror 305, 307, 308 ... Dichroic mirror 310 to 314 ... Condensing lens 320 ... Screen S101-S113 ... Step

Claims (13)

A discharge lamp having a light emitting container including a cavity portion in which a discharge medium is enclosed, a pair of electrodes whose end portions are arranged to face each other in the cavity portion, and
A driving device for supplying a driving current to the pair of electrodes;
Voltage detecting means for detecting a voltage between the electrodes of the pair of electrodes;
And a time measuring means for measuring time,
The driving device includes a first alternating current supply section for supplying a first alternating current having a frequency higher than 1 kHz to the pair of electrodes, and a second alternating current having a frequency of 1 kHz or less. Configured to alternately repeat the second AC current supply section supplied to
When the absolute value of the inter-electrode voltage of the pair of electrodes detected by the voltage detection means reaches the upper limit value V1, the drive device starts from the first alternating current supply section to the second alternating current supply section. To
In the second AC current supply section, the time measurement means measures the period of the second AC current supply section, and the absolute value of the voltage between the pair of electrodes detected by the voltage detection means is When the lower limit value V2 is reached or the period of the second alternating current supply section measured by the time measuring means reaches a predetermined period T, the first alternating current is supplied from the second alternating current supply section. Change to current supply section,
When the period of the second alternating current supply section reaches the period T and is changed from the second alternating current supply section to the first alternating current supply section, the second alternating current supply section When the absolute value of the inter-electrode voltage of the pair of electrodes when the period reaches the period T is V3, the upper limit value V1 is expressed by the following formula (1) from the initial value of the upper limit value V1. The light source device is configured to be changed to a value that is increased by an increase amount ΔV.
ΔV = a · (V3−V2) (1)
However, 0.1 ≦ a ≦ 1   When the absolute value of the inter-electrode voltage of the pair of electrodes reaches the lower limit value V2 and changes from the second alternating current supply section to the first alternating current supply section, the driving device The light source device according to claim 1, wherein when the upper limit value V1 is changed from an initial value, the upper limit value V1 is returned to the initial value.   3. The lower limit value V <b> 2 is an absolute value of a voltage between the electrodes of the pair of electrodes when the power supplied to the pair of electrodes reaches a rated power after the discharge lamp is turned on. Light source device.   The light source device according to any one of claims 1 to 3, wherein a difference between the upper limit value V1 and the lower limit value V2 is 15 V or less.   5. The light source device according to claim 1, wherein an amplitude of the first alternating current is decreased with time in the first alternating current supply section.   6. The light source device according to claim 1, wherein an amplitude of the second alternating current is increased with time in the second alternating current supply section.   The light source device according to claim 1, wherein a waveform of the first alternating current has a rectangular shape.   The light source device according to claim 1, wherein a waveform of the second alternating current is rectangular.   The light source device according to claim 1, wherein blackening of the discharge lamp is suppressed by supplying the first alternating current.   The light source device according to any one of claims 1 to 9, wherein an inter-electrode distance between the pair of electrodes is reduced by supplying the second alternating current.   The average value of the amplitude of the first alternating current in the first alternating current supply section and the average value of the amplitude of the second alternating current in the second alternating current supply section are the same. The light source device according to claim 1. A discharge lamp driving method comprising: a light emitting container including a cavity portion in which a discharge medium is sealed; and a pair of electrodes whose end portions are arranged to face each other in the cavity portion,
A first alternating current supply section for supplying a first alternating current having a frequency higher than 1 kHz to the pair of electrodes, and a second for supplying a second alternating current having a frequency of 1 kHz or less to the pair of electrodes. When the absolute value of the voltage between the electrodes of the pair of electrodes reaches the upper limit value V1, the second alternating current supply section is changed from the first alternating current supply section. When the absolute value of the inter-electrode voltage of the pair of electrodes reaches the lower limit value V2 or the period of the second AC current supply section reaches a predetermined period T, the second AC The current supply section is changed to the first AC current supply section, the period of the second AC current supply section reaches the period T, and the first AC current supply from the second AC current supply section. When changing to a section, the second intersection When the absolute value of the inter-electrode voltage of the pair of electrodes when the period of the current supply section reaches the period T is V3, the upper limit value V1 is less than the initial value of the upper limit value V1 (1) A drive current configured to be changed to a value larger by the increase amount ΔV shown in the equation is generated,
A method for driving a discharge lamp, wherein the driving current is supplied to the pair of electrodes.
ΔV = a · (V3−V2) (1)
However, 0.1 ≦ a ≦ 1   A projector comprising the light source device according to claim 1.

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