JP6476991B2 - Discharge lamp driving device, light source device, projector, and discharge lamp driving method - Google Patents

Description

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

When the discharge lamp is deteriorated and the lamp voltage is lowered, the electrode is less likely to be melted, and therefore, the protrusion at the tip of the electrode is narrowed, and it is known that the deterioration of the discharge lamp accelerates.
On the other hand, for example, as shown in Patent Document 1, there is a method of inserting a direct current between alternating current supplied to a discharge lamp, and increasing a direct current component as the deterioration state of the discharge lamp progresses. Proposed.

JP 2011-23288 A

  However, in the method as described above, the amount of melting of the projections of the electrode tip on the anode side is improved by the direct current, while the temperature of the electrode on the cathode side is reduced. There is a problem that the shape of the tip is deformed and flicker occurs. Therefore, the life of the discharge lamp may not be sufficiently improved.

  One aspect of the present invention has been made in view of the above problems, and a discharge lamp driving device capable of improving the life of a discharge lamp, a light source device provided with such a discharge lamp driving device, and such It is an object to provide a projector including a light source device. Another object of one aspect of the present invention is to provide a discharge lamp driving method capable of improving the life of the discharge lamp.

  One aspect of the discharge lamp driving device according to the present invention includes a discharge lamp driving unit that supplies a driving current to a discharge lamp having a first electrode and a second electrode, and a control unit that controls the discharge lamp driving unit. The driving current has a first alternating current period and a second alternating current period in which alternating current is supplied to the discharge lamp, and the first alternating current period includes a first polarity period in which the first electrode is an anode and the first polarity period. A plurality of first unit driving periods, each having a second polarity period in which the second electrode is an anode and having a length of the first polarity period larger than that of the second polarity period, are continuously configured, The period is composed of the first polarity period and the second polarity period, and a plurality of second unit driving periods, each having a length of the second polarity period larger than that of the first polarity period, are continuously formed. It is characterized by

  According to one aspect of the discharge lamp driving device of the present invention, the ratio of the length of the first polarity period to the length of the second polarity period is greater than 1 in the first unit driving period constituting the first AC period. . Therefore, in the first alternating current period, the sum of the lengths of the first polarity period becomes larger than the sum of the lengths of the second polarity period, and the melting of the projection on the tip of the first electrode in the first polarity period becomes the anode. The amount can be improved. On the other hand, since the second polarity period having the opposite polarity for a time shorter than the first polarity period is provided for each of the plurality of first unit driving periods constituting the first alternating current period, the anode in the second polarity period is provided. It can suppress that the temperature of the 2nd electrode which becomes is reduced. As a result, it is possible to suppress the deformation of the protrusion at the tip of the second electrode and to suppress the occurrence of flicker. The same applies to the second alternating current period except that the first electrode and the second electrode are reversed.

Therefore, according to one aspect of the discharge lamp driving device of the present invention, deformation of the protrusion on the tip of the electrode on the side opposite to the heating is performed while improving the melting amount of the protrusion on the tip on the electrode on the heating side. Therefore, the discharge lamp driving device capable of improving the life of the discharge lamp can be obtained.
Note that the electrode to be heated is the first electrode in the first AC period, and the second electrode in the second AC period.

The ratio of the length of the first polarity period to the length of the second polarity period in the first unit driving period is 3.0 or more, and the ratio of the first polarity period in the second unit driving period is The ratio of the length of the second polarity period to the length may be 3.0 or more.
According to this configuration, it is possible to further improve the melting amount of the protrusion of the tip of the electrode on the heating side while suppressing the temperature of the electrode on the opposite side to the heating from being lowered.

The length of the second polarity period in the first unit driving period and the length of the first polarity period in the second unit driving period may be smaller than 1.0 ms.
According to this configuration, it is possible to relatively increase the time during which the electrode on the side to be heated becomes the anode, so that the melting amount of the protrusion at the tip of the electrode on the side to be heated can be further improved.

The length of the second polarity period in the first unit driving period and the length of the first polarity period in the second unit driving period may be 0.16 ms or more.
According to this configuration, it is possible to suppress a decrease in temperature of the electrode on the side opposite to the heating.

The length of the first polarity period in the first unit drive period and the length of the second polarity period in the second unit drive period may be 1.0 ms or more.
According to this configuration, it is possible to further improve the melting amount of the protrusion of the tip of the electrode on the heating side.

The length of the first alternating current period and the length of the second alternating current period may be 5.0 ms or more.
According to this configuration, it is possible to further improve the melting amount of the protrusion of the tip of the electrode on the heating side.

The length of the first alternating current period may be equal to the length of the second alternating current period.
According to this configuration, the first electrode and the second electrode can be heated and melted in a well-balanced manner.

The length of the first alternating current period and the length of the second alternating current period may be different from each other.
According to this configuration, in the longer one of the first AC period and the second AC period, the temperature of the electrode to be heated can be further increased, so that the melting amount of the protrusion can be further improved. .

The driving current has a third alternating current period in which alternating current is supplied to the discharge lamp, and in the third alternating current period, the length of the first polarity period is equal to the length of the second polarity period. A plurality of unit drive periods may be formed continuously, and may be provided immediately after at least one of the first AC period and the second AC period.
According to this configuration, the shape of the protrusion and the degree of growth can be controlled.

The length of the first alternating current period may be set larger as the driving power supplied to the discharge lamp is smaller.
According to this configuration, when the driving power is small, the melting amount of the protrusion in the first electrode can be improved.

The average length of the first polarity period in the first alternating current period may be set to be smaller as the driving power supplied to the discharge lamp is smaller.
According to this configuration, when the drive power is small, when the length of the first AC period is increased, it is possible to suppress a decrease in the temperature of the second electrode on the opposite side to the heating.

The voltage detection unit is further configured to detect an inter-electrode voltage between the first electrode and the second electrode, and a length of the first AC period is set to be larger as the inter-electrode voltage is larger. It is also good.
According to this configuration, when the voltage between the electrodes is large, it is possible to improve the melting amount of the protrusions in the first electrode.

The average length of the first polarity period in the first AC period may be set smaller as the inter-electrode voltage is larger.
According to this configuration, when the voltage between the electrodes is large, when the length of the first alternating current period is increased, it is possible to suppress a decrease in the temperature of the second electrode on the opposite side to the heating.

The lengths of the first unit drive periods adjacent to each other in time may be different from each other.
According to this configuration, for example, when mounted on a projector, it is possible to suppress that an overshoot of the drive current due to the switching of the polarity of the electrodes interferes with the liquid crystal panel of the projector to generate noise.

The lengths of the first polarity periods temporally adjacent to each other across the second polarity period may be different from each other in the first alternating current period.
According to this configuration, in the first alternating current period, the thermal load applied to the first electrode fluctuates every first polarity period, so that the growth of the projections is stabilized.

In the first alternating current period, the lengths of the plurality of first polarity periods may be set to be smaller as the first polarity period provided later in time.
According to this configuration, it is possible to suppress a decrease in the temperature of the second electrode on the side opposite to the heating.

  One aspect of the light source device of the present invention is characterized by comprising the discharge lamp for emitting light and the discharge lamp driving device described above.

  According to one aspect of the light source device of the present invention, since the above-described discharge lamp driving device is provided, a light source device capable of improving the life of the discharge lamp can be obtained.

  One aspect of a projector according to the present invention is a light source device described above, a light modulation element that modulates light emitted from the light source device according to a video signal, and a projection that projects light modulated by the light modulation element And an optical system.

  According to one aspect of the projector of the present invention, since the light source device described above is provided, a projector that can improve the life of the discharge lamp can be obtained.

One aspect of the discharge lamp driving method according to the present invention is a discharge lamp driving method for driving a discharge lamp by supplying a drive current to a discharge lamp having a first electrode and a second electrode, wherein the discharge lamp is driven a first alternating periods alternating current is supplied, the drive current alternating current to the discharge lamp is closed and a second AC period supplied with the step of providing to said discharge lamp, said first AC period A first polarity period in which the first electrode is an anode, and a second polarity period in which the second electrode is an anode, and the first polarity period is longer than the second polarity period; A plurality of unit drive periods are continuously formed, and the second alternating current period includes the first polarity period and the second polarity period, and the length of the second polarity period is longer than the length of the first polarity period. A plurality of large second unit drive periods are continuously formed. To.

  According to one aspect of the discharge lamp driving method of the present invention, the life of the discharge lamp can be improved in the same manner as described above.

It is a schematic block diagram of the projector of 1st Embodiment. It is sectional drawing of the discharge lamp in 1st Embodiment. FIG. 3 is a block diagram showing various components of the projector of the first embodiment. It is a circuit diagram of a discharge lamp lighting device of a 1st embodiment. It is a block diagram showing an example of 1 composition of a control part of a 1st embodiment. It is a figure which shows the appearance of the processus | protrusion of the electrode tip of a discharge lamp. It is a figure which shows the drive current waveform of 1st Embodiment. It is a figure which shows the drive current waveform of 2nd Embodiment. It is a figure which shows the drive current waveform of 3rd Embodiment.

Hereinafter, a projector according to an embodiment of the present invention will be described with reference to the drawings.
The scope of the present invention is not limited to the following embodiments, and can be arbitrarily changed within the scope of the technical idea of the present invention. Moreover, in the following drawings, in order to make each structure intelligible, a scale, the number, etc. in an actual structure and each structure may be varied.

First Embodiment
As shown in FIG. 1, in the projector 500 of this embodiment, a light source device 200, a collimating lens 305, an illumination optical system 310, a color separation optical system 320, and three liquid crystal light valves 330R, 330G, 330B ( A light modulation element), a cross dichroic prism 340, and a projection optical system 350 are provided.

  Light emitted from the light source device 200 passes through the collimating lens 305 and enters the illumination optical system 310. The collimating lens 305 collimates the light from the light source device 200.

  The illumination optical system 310 adjusts the illuminance of the light emitted from the light source device 200 to be uniform on the liquid crystal light valves 330R, 330G, and 330B. Furthermore, the illumination optical system 310 aligns the polarization direction of the light emitted from the light source device 200 in one direction. The reason is that the light emitted from the light source device 200 is effectively used by the liquid crystal light valves 330R, 330G, and 330B.

  The light whose illuminance distribution and polarization direction are adjusted enters the color separation optical system 320. The color separation optical system 320 separates incident light into three color lights of red light (R), green light (G), and blue light (B). The three color lights are respectively modulated by the liquid crystal light valves 330R, 330G, and 330B associated with the respective color lights. The liquid crystal light valves 330R, 330G, and 330B include liquid crystal panels 560R, 560G, and 560B, which will be described later, and polarizing plates (not shown). The polarizing plates are disposed on the light incident side and the light emitting side of the liquid crystal panels 560R, 560G, and 560B, respectively.

  The modulated three color lights are combined by the cross dichroic prism 340. The combined light enters the projection optical system 350. The projection optical system 350 projects incident light onto the screen 700 (see FIG. 3). Thus, an image is displayed on the screen 700. As the configuration of each of the collimating lens 305, the illumination optical system 310, the color separation optical system 320, the cross dichroic prism 340, and the projection optical system 350, a known configuration can be adopted.

  FIG. 2 is a cross-sectional view showing the configuration of the light source device 200. As shown in FIG. The light source device 200 includes a light source unit 210 and a discharge lamp lighting device (discharge lamp driving device) 10. A cross-sectional view of the light source unit 210 is shown in FIG. The light source unit 210 includes a main reflector 112, a discharge lamp 90, and a sub reflector 50.

  The discharge lamp lighting device 10 supplies drive power (drive current) to the discharge lamp 90 to light the discharge lamp 90. The main reflector 112 reflects the light emitted from the discharge lamp 90 in the irradiation direction D. The irradiation direction D is parallel to the optical axis AX of the discharge lamp 90.

  The shape of the discharge lamp 90 is a rod-like shape extending along the irradiation direction D. One end of the discharge lamp 90 is a first end 90 e 1, and the other end of the discharge lamp 90 is a second end 90 e 2. The material of the discharge lamp 90 is, for example, a translucent material such as quartz glass. The central portion of the discharge lamp 90 bulges in a spherical shape, and the inside thereof is a discharge space 91. In the discharge space 91, a gas which is a discharge medium containing a rare gas, a metal halide compound and the like is sealed.

  The tips of the first electrode 92 and the second electrode 93 project into the discharge space 91. The first electrode 92 is disposed on the first end 90 e 1 side of the discharge space 91. The second electrode 93 is disposed on the second end 90 e 2 side of the discharge space 91. The shapes of the first electrode 92 and the second electrode 93 are in the shape of bars extending along the optical axis AX. In the discharge space 91, electrode tip portions of the first electrode 92 and the second electrode 93 are disposed to face each other with a predetermined distance therebetween. The material of the first electrode 92 and the second electrode 93 is, for example, a metal such as tungsten.

  A first terminal 536 is provided at the first end 90 e 1 of the discharge lamp 90. The first terminal 536 and the first electrode 92 are electrically connected by a conductive member 534 penetrating the inside of the discharge lamp 90. Similarly, a second terminal 546 is provided at the second end 90 e 2 of the discharge lamp 90. The second terminal 546 and the second electrode 93 are electrically connected by a conductive member 544 penetrating the inside of the discharge lamp 90. The material of the first terminal 536 and the second terminal 546 is, for example, a metal such as tungsten. As a material of the conductive members 534 and 544, for example, a molybdenum foil is used.

  The first terminal 536 and the second terminal 546 are connected to the discharge lamp lighting device 10. The discharge lamp lighting device 10 supplies drive power Wd for driving the discharge lamp 90 to the first terminal 536 and the second terminal 546. As a result, arc discharge occurs between the first electrode 92 and the second electrode 93. The light (discharge light) generated by the arc discharge is emitted in all directions from the discharge position, as indicated by the broken arrow.

  The main reflecting mirror 112 is fixed to a first end 90 e 1 of the discharge lamp 90 by a fixing member 114. The main reflecting mirror 112 reflects, of the discharge light, light traveling toward the opposite side to the irradiation direction D toward the irradiation direction D. The shape of the reflection surface (surface on the discharge lamp 90 side) of the main reflection mirror 112 is not particularly limited in the range in which the discharge light can be reflected in the irradiation direction D, and for example, even if it is a rotation elliptical shape It may be parabolic. For example, when the shape of the reflecting surface of the main reflecting mirror 112 is a paraboloid of revolution, the main reflecting mirror 112 can convert the discharge light into light substantially parallel to the optical axis AX. Thereby, the collimating lens 305 can be omitted.

  The sub reflection mirror 50 is fixed to the second end 90 e 2 side of the discharge lamp 90 by a fixing member 522. The shape of the reflection surface (surface on the discharge lamp 90 side) of the sub-reflecting mirror 50 is a spherical shape surrounding a portion on the second end 90 e 2 side of the discharge space 91. The sub-reflecting mirror 50 reflects, toward the main reflecting mirror 112, light traveling toward the side opposite to the side where the main reflecting mirror 112 is disposed among the discharge light. Thereby, the utilization efficiency of the light radiated from the discharge space 91 can be enhanced.

  The material of the fixing members 114 and 522 is not particularly limited as long as it is a heat-resistant material that can withstand the heat generation from the discharge lamp 90, and is, for example, an inorganic adhesive. The method of fixing the arrangement of the main reflecting mirror 112 and the sub reflecting mirror 50 and the discharge lamp 90 is not limited to the method of fixing the main reflecting mirror 112 and the sub reflecting mirror 50 to the discharge lamp 90, but any method can be adopted. . For example, the discharge lamp 90 and the main reflecting mirror 112 may be fixed to the housing (not shown) of the projector 500 independently. The same applies to the sub-reflecting mirror 50.

Hereinafter, the circuit configuration of the projector 500 will be described.
FIG. 3 is a diagram showing an example of a circuit configuration of the projector 500 of the present embodiment. The projector 500 includes an image signal conversion unit 510, a DC power supply device 80, liquid crystal panels 560R, 560G and 560B, an image processing device 570, and a CPU (Central Processing Unit) 580, in addition to the optical system shown in FIG. And.

  The image signal conversion unit 510 converts an image signal 502 (such as a luminance-color difference signal or an analog RGB signal) input from the outside into a digital RGB signal of a predetermined word length to generate image signals 512R, 512G, and 512B. The image processing device 570 is supplied.

  The image processing device 570 performs image processing on each of the three image signals 512R, 512G, and 512B. The image processing device 570 supplies drive signals 572R, 572G, 572B for driving the liquid crystal panels 560R, 560G, 560B to the liquid crystal panels 560R, 560G, 560B.

  The DC power supply device 80 converts an AC voltage supplied from the external AC power supply 600 into a constant DC voltage. The DC power supply device 80 includes an image signal conversion unit 510 on the secondary side of a transformer (not shown but included in the DC power supply device 80), an image processing device 570, and the discharge lamp lighting device 10 on the primary side of the transformer. Supply DC voltage.

  The discharge lamp lighting device 10 generates a high voltage between the electrodes of the discharge lamp 90 at start-up to cause dielectric breakdown to form a discharge path. Thereafter, the discharge lamp lighting device 10 supplies the drive current I for the discharge lamp 90 to maintain the discharge.

  The liquid crystal panels 560R, 560G, and 560B are respectively provided in the liquid crystal light valves 330R, 330G, and 330B described above. The liquid crystal panels 560R, 560G, and 560B modulate the transmittance (brightness) of color light incident on the liquid crystal panels 560R, 560G, and 560B via the above-described optical system based on the drive signals 572R, 572G, and 572B, respectively. .

  The CPU 580 controls various operations from the lighting start of the projector 500 to the lighting off. For example, in the example of FIG. 3, the lighting instruction and the lighting off instruction are output to the discharge lamp lighting device 10 via the communication signal 582. The CPU 580 receives lighting information of the discharge lamp 90 from the discharge lamp lighting device 10 via the communication signal 584.

Hereinafter, the configuration of the discharge lamp lighting device 10 will be described.
FIG. 4 is a diagram showing an example of a circuit configuration of the discharge lamp lighting device 10. As shown in FIG.
As shown in FIG. 4, the discharge lamp lighting device 10 includes a power control circuit 20, a polarity inversion circuit 30, a control unit 40, an operation detection unit (voltage detection unit) 60, and an igniter circuit 70. There is.

  The power control circuit 20 generates drive power Wd to be supplied to the discharge lamp 90. In the present embodiment, the power control circuit 20 is configured of a down chopper circuit that receives a voltage from the DC power supply device 80, steps down the input voltage, and outputs a DC current Id.

  The power control circuit 20 includes a switch element 21, a diode 22, a coil 23 and a capacitor 24. The switch element 21 is configured of, for example, a transistor. In the present embodiment, one end of the switch element 21 is connected to the positive voltage side of the DC power supply device 80, and the other end is connected to the cathode terminal of the diode 22 and one end of the coil 23.

  The other end of the coil 23 is connected to one end of the capacitor 24, and the other end of the capacitor 24 is connected to the anode terminal of the diode 22 and the negative voltage side of the DC power supply 80. A current control signal is input to the control terminal of the switch element 21 from the control unit 40 described later to control ON / OFF of the switch element 21. For example, a PWM (Pulse Width Modulation) control signal may be used as the current control signal.

  When the switch element 21 is turned on, a current flows through the coil 23, and energy is stored in the coil 23. Thereafter, when the switch element 21 is turned off, the energy stored in the coil 23 is released along the path passing through the capacitor 24 and the diode 22. As a result, a direct current Id is generated in accordance with the ratio of the time during which the switch element 21 is turned on.

  The polarity inverting circuit 30 inverts the polarity of the direct current Id input from the power control circuit 20 at a predetermined timing. As a result, the polarity inverting circuit 30 generates and outputs a drive current I which is a direct current which lasts for a controlled time, or a drive current I which is an alternating current having an arbitrary frequency. In the present embodiment, the polarity inverting circuit 30 is configured by an inverter bridge circuit (full bridge circuit).

  The polarity inversion circuit 30 includes, for example, a first switch element 31, a second switch element 32, a third switch element 33, and a fourth switch element 34, each of which is a transistor or the like. In the polarity inverting circuit 30, the first switch element 31 and the second switch element 32 connected in series and the third switch element 33 and the fourth switch element 34 connected in series are connected in parallel with each other. It has composition. A polarity inversion control signal from the control unit 40 is input to control terminals of the first switch element 31, the second switch element 32, the third switch element 33, and the fourth switch element 34, respectively. The on / off operation of the first switch element 31, the second switch element 32, the third switch element 33, and the fourth switch element 34 is controlled based on the polarity inversion control signal.

  In the polarity inverting circuit 30, the operation of alternately turning ON / OFF the first switch element 31 and the fourth switch element 34, and the second switch element 32 and the third switch element 33 is repeated. Thereby, the polarity of the direct current Id output from the power control circuit 20 is alternately inverted. The polarity inversion circuit 30 is controlled from the common connection point of the first switch element 31 and the second switch element 32 and the common connection point of the third switch element 33 and the fourth switch element 34. A drive current I which is a direct current which continues the same polarity state only, or a drive current I which is an alternating current having a controlled frequency is generated and output.

  That is, in the polarity inverting circuit 30, when the first switch element 31 and the fourth switch element 34 are ON, the second switch element 32 and the third switch element 33 are OFF, and the first switch element 31 and the third switch element 33 When the fourth switch element 34 is off, control is performed so that the second switch element 32 and the third switch element 33 are on. Therefore, when the first switch element 31 and the fourth switch element 34 are ON, the drive current I flowing from the one end of the capacitor 24 in the order of the first switch element 31, the discharge lamp 90 and the fourth switch element 34 is generated. Do. When the second switch element 32 and the third switch element 33 are ON, a drive current I is generated which flows from the one end of the capacitor 24 in the order of the third switch element 33, the discharge lamp 90 and the second switch element 32.

  In the present embodiment, the combined portion of the power control circuit 20 and the polarity inversion circuit 30 corresponds to the discharge lamp driving unit 230. That is, the discharge lamp driving unit 230 supplies the discharge lamp 90 with a drive current I (drive power) for driving the discharge lamp 90.

  The control unit 40 controls the discharge lamp driving unit 230. In the example of FIG. 4, the control unit 40 controls the power control circuit 20 and the polarity inversion circuit 30 to maintain the drive current I in the same polarity for the holding time, the current value of the drive current I (power of the drive power Wd Control parameters such as value and frequency. The control unit 40 performs polarity inversion control on the polarity inversion circuit 30 to control the holding time in which the drive current I continues with the same polarity and the frequency of the drive current I at the polarity inversion timing of the drive current I. The control unit 40 performs current control on the power control circuit 20 to control the current value of the output direct current Id.

  The configuration of the control unit 40 is not particularly limited. In the present embodiment, the control unit 40 is configured to include a system controller 41, a power control circuit controller 42, and a polarity inversion circuit controller 43. The control unit 40 may be configured partially or entirely by a semiconductor integrated circuit.

  The system controller 41 controls the power control circuit 20 and the polarity inversion circuit 30 by controlling the power control circuit controller 42 and the polarity inversion circuit controller 43. The system controller 41 may control the power control circuit controller 42 and the polarity inversion circuit controller 43 based on the lamp voltage (interelectrode voltage) Vla detected by the operation detection unit 60 and the drive current I.

  In the present embodiment, the system controller 41 is configured to include the storage unit 44. The storage unit 44 may be provided independently of the system controller 41.

  The system controller 41 may control the power control circuit 20 and the polarity inversion circuit 30 based on the information stored in the storage unit 44. The storage unit 44 may store, for example, information on drive parameters such as a retention time in which the drive current I continues with the same polarity, a current value of the drive current I, a frequency, a waveform, and a modulation pattern.

  The power control circuit controller 42 controls the power control circuit 20 by outputting a current control signal to the power control circuit 20 based on a control signal from the system controller 41.

  The polarity inversion circuit controller 43 controls the polarity inversion circuit 30 by outputting a polarity inversion control signal to the polarity inversion circuit 30 based on the control signal from the system controller 41.

  The control unit 40 is realized by using a dedicated circuit, and can perform the above-described control and various controls of processing to be described later. On the other hand, the control unit 40 can function as a computer, for example, by the CPU executing a control program stored in the storage unit 44, and can perform various controls of these processes.

  FIG. 5 is a diagram for explaining another configuration example of the control unit 40. As shown in FIG. As shown in FIG. 5, the control unit 40 is configured to function as a current control unit 40-1 that controls the power control circuit 20 and a polarity inversion control unit 40-2 that controls the polarity inversion circuit 30 according to a control program. It may be done.

  In the example shown in FIG. 4, the control unit 40 is configured as a part of the discharge lamp lighting device 10. On the other hand, the CPU 580 may be configured to be responsible for a part of the functions of the control unit 40.

  In the present embodiment, the operation detection unit 60 includes a voltage detection unit that detects the lamp voltage of the discharge lamp 90 and outputs lamp voltage information to the control unit 40. In addition, the operation detection unit 60 may include a current detection unit that detects the drive current I and outputs drive current information to the control unit 40. In the present embodiment, the operation detection unit 60 is configured to include a first resistor 61, a second resistor 62, and a third resistor 63.

  In the present embodiment, the voltage detection unit of the operation detection unit 60 detects the lamp voltage Vla based on the voltage divided by the first resistor 61 and the second resistor 62 connected in series with each other in parallel with the discharge lamp 90 . Further, in the present embodiment, the current detection unit detects the drive current I by the voltage generated in the third resistor 63 connected in series to the discharge lamp 90.

  The igniter circuit 70 operates only at the start of lighting of the discharge lamp 90. The igniter circuit 70 performs high voltage (discharge) necessary to form a discharge path by dielectric breakdown between the electrodes of the discharge lamp 90 (between the first electrode 92 and the second electrode 93) at the start of lighting of the discharge lamp 90. The voltage (higher than that during normal lighting of the lamp 90) is supplied between the electrodes of the discharge lamp 90 (between the first electrode 92 and the second electrode 93). In the present embodiment, the igniter circuit 70 is connected in parallel with the discharge lamp 90.

  In FIGS. 6A and 6B, tip portions of the first electrode 92 and the second electrode 93 are shown. Protrusions 552 p and 562 p are formed on the tips of the first electrode 92 and the second electrode 93, respectively. The discharge generated between the first electrode 92 and the second electrode 93 mainly occurs between the protrusion 552 p and the protrusion 562 p. When the protrusions 552 p and 562 p are present as in the present embodiment, the movement of the discharge position (arc position) in the first electrode 92 and the second electrode 93 can be suppressed as compared with the case where there are no protrusions.

  FIG. 6A shows a first polarity state in which the first electrode 92 operates as an anode and the second electrode 93 operates as a cathode. In the first polarity state, electrons move from the second electrode 93 (cathode) to the first electrode 92 (anode) by discharge. Electrons are emitted from the cathode (second electrode 93). Electrons emitted from the cathode (second electrode 93) collide with the tip of the anode (first electrode 92). The collision generates heat and the temperature of the tip (protrusion 552p) of the anode (first electrode 92) rises.

  FIG. 6B shows a second polarity state in which the first electrode 92 operates as a cathode and the second electrode 93 operates as an anode. In the second polarity state, electrons move from the first electrode 92 to the second electrode 93 contrary to the first polarity state. As a result, the temperature of the tip (protrusion 562p) of the second electrode 93 rises.

  Thus, by supplying the drive current I to the discharge lamp 90, the temperature of the anode with which the electrons collide increases. On the other hand, the temperature of the cathode emitting electrons decreases while emitting electrons toward the anode.

Next, control of the discharge lamp driving unit 230 by the control unit 40 will be described.
FIG. 7 is a diagram showing a drive current waveform DW1 of the drive current I supplied to the discharge lamp 90 of the present embodiment. In FIG. 7, the vertical axis represents the drive current I, and the horizontal axis represents the time T.
In the present embodiment, the control unit 40 controls the discharge lamp driving unit 230 according to the drive current waveform DW1 shown in FIG.

[Drive current waveform]
As shown in FIG. 7, in the drive current waveform DW1, a plurality of control cycles C1 are continuously formed. The control cycle C1 includes a first AC period PH11 and a second AC period PH21. That is, the drive current waveform DW1 (drive current I) has a first AC period PH11 and a second AC period PH21. The first AC period PH11 and the second AC period PH21 are periods in which an alternating current whose polarity is reversed between the current value Im1 and the current value -Im1 is supplied to the discharge lamp 90 as the drive current I.

(Exchange period)
The first AC period PH11 is a period in which the first electrode 92 is heated. In the first alternating current period PH11, a plurality of first unit driving periods U11 consisting of a first polarity period P11a in which the first electrode 92 becomes an anode and a second polarity period P11b in which the second electrode 93 becomes an anode are continuously configured. ing. In the present embodiment, the first AC period PH11 includes, for example, six first unit driving periods U11, that is, a first unit driving period U11a, a first unit driving period U11b, and a first unit driving period U11c, The first unit drive period U11d, the first unit drive period U11e, and the first unit drive period U11f are continuously configured in this order.

  The second AC period PH21 is a period in which the second electrode 93 is heated. In the second AC period PH21, a plurality of second unit driving periods U21 each consisting of a first polarity period P21a in which the first electrode 92 becomes an anode and a second polarity period P21b in which the second electrode 93 becomes an anode are continuously configured. ing. In the present embodiment, the second AC period PH21 includes, for example, six second unit drive periods U21, that is, a second unit drive period U21a, a second unit drive period U21b, and a second unit drive period U21c, The second unit drive period U21d, the second unit drive period U21e, and the second unit drive period U21f are continuously configured in this order.

  In the drive current waveform DW1 of the present embodiment, the first AC period PH11 and the second AC period PH21 have the same waveforms except that their polarities are reversed. That is, the length t11a of the first polarity period P11a in each of the first unit drive periods U11a to U11f is the same as the length t21b of the second polarity period P21b in each of the second unit drive periods U21a to U21f. The length t11b of the second polarity period P11b in each of the first unit drive periods U11a to U11f is the same as the length t21a of the first polarity period P21a in each of the second unit drive periods U21a to U21f.

Therefore, in the present embodiment, the length t11 of the first AC period PH11 and the length t21 of the second AC period PH21 are equal.
In the present embodiment, the length t11 of the first AC period PH11 and the length t21 of the second AC period PH21 are set to, for example, 5.0 ms (milliseconds) or more. By setting in this manner, it is possible to improve the melting amount of the protrusions 552p and the protrusions 562p in the first electrode 92 and the second electrode 93.

  In the present specification, that the lengths of the two periods are equal not only when the lengths of the two periods are strictly the same but also when the ratio of the lengths of the two periods is 0.9 or more, It includes a range of about 1.1 or less.

  As described above, in the present embodiment, since the first AC period PH11 and the second AC period PH21 have the same waveform except that the polarity is reversed, they are represented in the following description. Only the first exchange period PH11 may be described.

(Unit drive period)
In the first unit drive period U11 of the first AC period PH11, the ratio of the length t11a of the first polarity period P11a to the length t11b of the second polarity period P11b is larger than one. In other words, in the first unit drive period U11, the holding time ratio of the holding time held at the first polarity to the holding time held at the second polarity is set to be a predetermined value X (X> 1) or more. Be done. Therefore, in the first unit drive period U11, the length t11a of the first polarity period P11a is larger than the length t11b of the second polarity period P11b.

  Thus, in the first AC period PH11 in which the plurality of first unit drive periods U11 are continuously configured, the sum of the length t11a of the first polarity period P11a is the length t11b of the second polarity period P11b. Greater than the sum. Therefore, in the first AC period PH11, the first electrode 92 serving as the anode is heated in the first polarity period P11a.

In the present embodiment, for example, the predetermined value X is set to 3.0 or more. In other words, the ratio (holding time ratio) of the length t11a of the first polarity period P11a to the length t11b of the second polarity period P11b in the first AC period PH11 is 3.0 or more.
By setting in this manner, heating is performed in the first AC period PH11 while suppressing the temperature of the second electrode 93 from decreasing in the first AC period PH11, which is the opposite electrode to the heating. The amount of melting of the first electrode 92 can be further improved.

  In the present embodiment, the lengths of the first unit drive periods U11a to U11f are different from each other. Thus, in the present embodiment, the lengths of the first unit drive periods U11 adjacent in time are different from each other.

In the present embodiment, for example, the length t11a of the first polarity period P11a in the first unit drive period U11 is 1.0 ms (milliseconds) or more. In other words, the length t11a of the first polarity period P11a is equal to or more than the half cycle length of the 500 Hz alternating current.
By setting in this manner, it is possible to effectively improve the melting amount of the protrusion 552p at the tip of the first electrode 92.

  The length t11a of the first polarity period P11a in the first unit drive period U11 is preferably 5.0 ms (milliseconds) or less, that is, less than the half cycle length of the alternating current of 100 Hz. This is because the decrease in the temperature of the second electrode 93 which is the cathode in the first polarity period P11a can be effectively suppressed.

  In the present embodiment, for example, the lengths t11a of the first polarity periods P11a included in the first unit driving periods U11a to U11f are different from each other. Thus, in the first AC period PH11, the lengths t11a of the first polarity periods P11a adjacent to each other across the second polarity period P11b are different from each other.

In the present embodiment, the length t11b of the second polarity period P11b in the first unit drive period U11 is, for example, about 0.16 ms (milliseconds) or more and less than 1.0 ms (milliseconds). In other words, the length t11b of the second polarity period P11b is equal to or greater than the half cycle length of the 3 kHz alternating current and smaller than the half cycle length of the 500 Hz alternating current.
By setting in this manner, it is possible to further improve the melting amount of the first electrode 92 while suppressing the temperature of the second electrode 93 from decreasing in the first AC period PH11.

  An example of the length t11a of the first polarity period P11a and the length t11b of the second polarity period P11b of the first unit driving period U11 in the first AC period PH11 is shown in Table 1. Table 1 also shows the ratio of the length t11a of the first polarity period P11a to the length t11b of the second polarity period P11b, that is, the holding time ratio of the holding time of the first polarity to the holding time of the second polarity. ing.

  In Table 1, as an example, the length t11a of the first polarity period P11a is set to be smaller in the order from the first unit driving period U11a to the first unit driving period U11f. In other words, in the first AC period PH11, the lengths t11a of the plurality of first polarity periods P11a are set to be smaller as the first polarity period P11a provided later in time.

  In the second unit driving period U21 of the second AC period PH21, the ratio of the length t21b of the second polarity period P21b to the length t21a of the first polarity period P21a is larger than 1 as in the first unit driving period U11. . In other words, in the second unit driving period U21, the holding time ratio of the holding time held at the second polarity to the holding time held at the first polarity is set to be a predetermined value X (X> 1) or more. Be done. Therefore, in the second unit drive period U21, the length t21b of the second polarity period P21b is larger than the length t21a of the first polarity period P21a.

  Thus, in the second AC period PH21 in which the plurality of second unit drive periods U21 are continuously configured, the sum of the length t21b of the second polarity period P21b is equal to the length t21a of the first polarity period P21a. Greater than the sum. Therefore, in the second AC period PH21, the second electrode 93 serving as the anode is heated in the second polarity period P21b.

As described above, in the present embodiment, the predetermined value X is set to 3.0 or more. That is, the ratio (holding time ratio) of the length t21b of the second polarity period P21b to the length t21a of the first polarity period P21a in the second AC period PH21 is 3.0 or more.
By setting in this manner, it is possible to further improve the melting amount of the second electrode 93 while suppressing the temperature of the first electrode 92 from decreasing in the second AC period PH21.

In the present embodiment, for example, the length t21b of the second polarity period P21b in the second unit driving period U21 is 1.0 ms (the length t11a of the first polarity period P11a in the first unit driving period U11). Ms) or more.
By setting in this manner, it is possible to improve the melting amount of the protrusion of the tip of the electrode on the heating side.

  The length t21b of the second polarity period P21b in the second unit drive period U21 is 5.0 ms (milliseconds) or less, similarly to the length t11a of the first polarity period P11a in the first unit drive period U11. The half cycle length of the alternating current of 100 Hz or less is preferable. This is because the decrease in the temperature of the first electrode 92 which is the cathode can be effectively suppressed in the second polarity period P21b.

  In the present embodiment, the length t21a of the first polarity period P21a in the second unit driving period U21 is, for example, about 0.16 ms (millimeters), similarly to the length t11b of the second polarity period P11b in the first AC period PH11. Seconds) and less than 1.0 ms (milliseconds).

  As described above, the control unit 40 according to the present embodiment causes the discharge lamp driving unit 230 to be supplied such that the drive current I corresponding to each period described above is supplied to the discharge lamp 90 according to the drive current waveform DW1. Control.

  The control of the discharge lamp driving unit 230 by the control unit 40 described above can also be expressed as a discharge lamp driving method. That is, the discharge lamp driving method of the present embodiment is a discharge lamp driving method for driving the discharge lamp 90 by supplying the drive current I to the discharge lamp 90 having the first electrode 92 and the second electrode 93. A first AC period PH11 in which an alternating current is supplied to the lamp 90, and a second AC period PH21 in which an alternating current is supplied to the discharge lamp 90. In the first AC period PH11, the first electrode 92 is an anode. A plurality of first unit driving periods U11 each consisting of a first polarity period P11a and a second polarity period P11b in which the second electrode 93 becomes an anode are continuously configured, and the second AC period PH21 is a first polarity period P21a. And a plurality of second unit driving periods U21 each including the second polarity period P21b are continuously formed, and the first polarity period P11a with respect to the length t11b of the second polarity period P11b in the first unit driving period U11 is The ratio of t11a is greater than 1, the second unit driving period U21, the ratio of the length t21b of the second polarity period P21b to the length t21a of the first polarity period P21a is characterized by greater than 1.

  According to the present embodiment, the ratio of the length t11a of the first polarity period P11a to the length t11b of the second polarity period P11b is larger than 1 in the first unit driving period U11 constituting the first AC period PH11. Therefore, in the first AC period PH11, the sum of the length t11a of the first polarity period P11a is larger than the sum of the length t11b of the second polarity period P11b, and the first electrode serving as the anode in the first polarity period P11a The amount of melting of the protrusions 552p of 92 can be improved.

  On the other hand, since the second polarity period P11b, which has the opposite polarity for a time shorter than the first polarity period P11a, is provided for each of the plurality of first unit driving periods U11 constituting the first AC period PH11, It can suppress that the temperature of the 2nd electrode 93 used as an anode falls in polarity period P11b. Thus, deformation of the protrusion 562p of the second electrode 93 can be suppressed, and flicker can be suppressed. The same applies to the second AC period PH21 except that the polarity is reversed.

  Therefore, according to the present embodiment, it is possible to suppress the deformation of the protrusion on the tip of the electrode on the opposite side to the heated electrode while suppressing the flicker while improving the melting amount of the protrusion on the tip on the heated electrode. Therefore, a discharge lamp driving device capable of improving the life of the discharge lamp 90 can be obtained.

  Further, according to the present embodiment, the predetermined value X is set to 3.0 or more, that is, the ratio of the length t11a of the first polarity period P11a to the length t11b of the second polarity period P11b is 3.0. As described above, the amount of melting of the protrusion 552p of the first electrode 92 can be improved in the first alternating current period PH11 while suppressing the temperature of the second electrode 93 from being lowered. Therefore, the protrusion 562p of the second electrode 93 can be prevented from being deformed and flickering can be suppressed, and the protrusion 552p of the first electrode 92 can be melted and grown, and the shape of the protrusion 552p can be maintained thick.

  Further, according to the present embodiment, the length of the first polarity period P11a in the first unit drive period U11 is 1.0 ms (milliseconds) or more. Therefore, the time for which the first electrode 92 is heated in the first alternating current period PH11 can be sufficiently extended, and the first electrode 92 can be appropriately melted.

  Further, according to the present embodiment, the length t11b of the second polarity period P11b in the first unit drive period U11 is set to 0.16 ms (milliseconds) or more and smaller than 1.0 ms (milliseconds). Be done. Thus, the amount of melting of the first electrode 92 can be further improved while suppressing the temperature of the second electrode 93 from decreasing in the first AC period PH11.

  Further, according to the present embodiment, the length t11 of the first AC period PH11 is set to 5.0 ms (milliseconds) or more. Thereby, the first electrode 92 can be melted appropriately.

  Further, according to the present embodiment, the length t11 of the first AC period PH11 and the length t21 of the second AC period PH21 are set equal. Therefore, the first electrode 92 and the second electrode 93 can be heated and melted with good balance.

  Further, according to the present embodiment, since the lengths of the adjacent first unit drive periods U11 are different from each other, the timing at which the first polarity and the second polarity are switched becomes irregular. Therefore, it is possible to suppress the occurrence of noise due to the overshoot of the drive current I, which occurs when the first polarity and the second polarity are switched, interfering with the liquid crystal panels 560R, 560G, and 560B of the projector 500.

  Further, according to the present embodiment, since the lengths of the first polarity periods P11a adjacent to each other across the second polarity period P11b in the first AC period PH11 are different from each other, the first electrode may be formed every first unit driving period U11. The heat load applied to 92 fluctuates. As a result, the degree of melting of the first electrode 92 fluctuates, and the growth of the protrusion 552p is stabilized.

  In addition, although the second electrode 93, which is a cathode in the first polarity period P11a, is provided with the second polarity period P11b, the temperature decrease is suppressed to some extent, but the temperature of the second electrode 93 is the first alternating period PH11. In the inside, it may fall gradually with progress of time.

  On the other hand, according to an example shown in Table 1 of the present embodiment, in the first AC period PH11, the lengths t11a of the plurality of first polarity periods P11a are first polarity periods provided later in time It is set to be smaller as P11a. Therefore, in the first AC period PH11, as the time passes, the interval switching to the second polarity period P11b becomes shorter, and it is possible to further suppress the decrease in the temperature of the second electrode 93.

  In the present embodiment, the following configurations and methods may be adopted.

In the present embodiment, the number of first unit driving periods U11 included in the first AC period PH11 and the number of second unit driving periods U21 included in the second AC period PH21 may be five or less. , 7 or more.
Further, in the present embodiment, even if the number of first unit drive periods U11 included in the first AC period PH11 and the number of second unit drive periods U21 included in the second AC period PH21 are different from each other. Good.

Further, in the present embodiment, the lengths of the unit drive periods may be different from each other in only one of the first AC period PH11 and the second AC period PH21.
Further, in the present embodiment, in the first AC period PH11 of the first AC period PH11 and the second AC period PH21, the first polarity period P11a that is temporally adjacent to each other with the second polarity period P11b interposed therebetween. The lengths t11a may be different from each other, or the lengths t21b of the second polarity periods P21b adjacent to each other across the first polarity period P21a may be different from each other only in the second AC period PH21.

  Further, in the present embodiment, a length t11a of the first polarity period P11a is provided later in time only in the first AC period PH11 among the first AC period PH11 and the second AC period PH21. The first polarity period P11a may be set to be smaller, or only in the second AC period PH21, the length t21b of the second polarity period P21b may be shorter than the second polarity period P21b. It may be set to be smaller.

Furthermore, in the present embodiment, the lengths of the plurality of first unit drive periods U11 included in the first AC period PH11 may be the same or may be randomly changed.
Further, in the present embodiment, the lengths of the first polarity periods P11a included in the first unit drive period U11 may be the same or may be randomly changed.

In the present embodiment, the predetermined value X may be larger than 1 and smaller than 3.0.
Furthermore, in the present embodiment, the length t11 of the first alternating current period PH11 may be smaller than 5.0 ms (milliseconds).

Further, in the present embodiment, the length t11a of the first polarity period P11a may be smaller than 1.0 ms (milliseconds).
Further, in the present embodiment, the length t11b of the second polarity period P11b may be smaller than 0.16 ms (milliseconds), or may be 1.0 ms (milliseconds) or more.

  Further, in the present embodiment, the length of each period in the drive current waveform DW1 may be changed according to the change of the drive power Wd or the lamp voltage Vla. The details will be described below.

  Table 2 is a table showing an example in which the length t11 of the first alternating current period PH11 is changed according to the change of the drive power Wd.

  As shown in Table 2, in this configuration, the length t11 of the first AC period PH11 is set larger as the drive power Wd supplied to the discharge lamp 90 is smaller.

  When the drive power Wd supplied to the discharge lamp 90 decreases, the drive current I supplied to the discharge lamp 90 decreases, so the heat load applied to the first electrode 92 and the second electrode 93 decreases, and the first electrode The protrusions 552p, 562p of the 92 and the second electrode 93 are less likely to be melted. Therefore, the protrusions 552p and 562p may be deformed to cause flicker.

  On the other hand, according to this configuration, the length t11 of the first AC period PH11 is set to be larger as the drive power Wd supplied to the discharge lamp 90 is smaller. Therefore, the total time of the first polarity period P11a, that is, the time during which the first electrode 92 is heated can be increased, and the melting amount of the protrusion 552p of the first electrode 92 can be improved. Thus, according to this configuration, when the drive power Wd decreases, the shape of the protrusion 552p of the first electrode 92 can be easily maintained, and the occurrence of flicker can be suppressed. The same applies to the second exchange period PH21.

  Further, as shown in Table 2, in this configuration, the average lengths of the first polarity period P11a and the second polarity period P11b are set smaller as the driving power Wd is smaller.

  When the drive power Wd decreases, if the length t11 of the first AC period PH11 is set large as described above, the heating time of the first electrode 92 increases, while the temperature of the second electrode 93 decreases. The time to do Therefore, the protrusions 562p of the second electrode 93 may be deformed to cause flicker.

  On the other hand, according to this configuration, the average length of the first polarity period P11a and the second polarity period P11b is set smaller as the driving power Wd supplied to the discharge lamp 90 is smaller. Therefore, the interval at which the first polarity is switched to the second polarity can be shortened, and the frequency at which the second electrode 93 is heated can be improved. Therefore, according to this configuration, when the length t11 of the first alternating current period PH11 is set large along with the decrease of the drive power Wd, the temperature of the second electrode 93 can be suppressed from being lowered and deformed. .

  Table 3 is a table showing an example in which the length t11 of the first alternating current period PH11 is changed according to the change of the lamp voltage Vla.

  As shown in Table 3, in this configuration, the length t11 of the first AC period PH11 is larger as the lamp voltage Vla applied between the first electrode 92 and the second electrode 93 of the discharge lamp 90 is larger. It is set large.

  When the discharge lamp 90 is deteriorated due to aging or the like, the distance between the first electrode 92 and the second electrode 93 is increased, and the lamp voltage Vla is increased. In the constant power drive, when the lamp voltage Vla increases, the drive current I decreases, so the thermal load applied to the first electrode 92 and the second electrode 93 decreases, and the protrusions of the first electrode 92 and the second electrode 93 It becomes difficult to melt 552p and 562p. Therefore, the protrusions 552p, 562p of the first electrode 92 and the second electrode 93 can not be melted sufficiently, and the thickness of the protrusions 552p, 562p may not be maintained.

  On the other hand, according to this configuration, the length t11 of the first AC period PH11 is set larger as the lamp voltage Vla applied to the discharge lamp 90 is larger. Therefore, the time for which the first electrode 92 is heated can be increased as the first electrode 92 is less likely to be melted, and the fact that the first electrode 92 is not melted can be suppressed.

  In this configuration, the average length of the first polarity period P11a and the second polarity period P11b in the first AC period PH11 is set smaller as the lamp voltage Vla is larger.

  In the same manner as described above, when the length t11 of the first AC period PH11 is increased, the time for the temperature of the second electrode 93 to decrease becomes longer, so the protrusion 562p of the second electrode 93 is deformed and flicker occurs. There is.

  On the other hand, according to this configuration, as the average length of each of the first polarity period P11a and the second polarity period P11b in the first AC period PH11 increases, the lamp voltage Vla applied to the discharge lamp 90 increases. , Set small. Therefore, as described above, when the length t11 of the first alternating current period PH11 is set large as the lamp voltage Vla increases, the temperature of the second electrode 93 is lowered and deformed. It can be suppressed.

Second Embodiment
The second embodiment differs from the first embodiment in the length of the first AC period and the length of the second AC period.
In the following description, the same components as those in the above embodiment may be omitted by the same reference numerals.

FIG. 8 is a diagram showing a drive current waveform DW2 of the drive current I supplied to the discharge lamp 90 of the present embodiment. In FIG. 8, the vertical axis represents the drive current I, and the horizontal axis represents the time T.
In the present embodiment, the control unit 40 controls the discharge lamp driving unit 230 according to the drive current waveform DW2 shown in FIG.

  As shown in FIG. 8, in the drive current waveform DW2, a plurality of control cycles C2 are continuously formed. The control cycle C2 includes a first alternating current period PH11 and a second alternating current period PH22. That is, the drive current waveform DW2 (drive current I) has a first alternating current period PH11 and a second alternating current period PH22. The second alternating current period PH22 is a period in which an alternating current whose polarity is reversed between the current value Im1 and the current value -Im1 is supplied to the discharge lamp 90 as the driving current I.

  The second AC period PH22 is a period in which the second electrode 93 is heated. In the second AC period PH22, a plurality of second unit driving periods U22 each consisting of a first polarity period P22a in which the first electrode 92 becomes an anode and a second polarity period P22b in which the second electrode 93 becomes an anode are continuously configured. ing. In the present embodiment, the second AC period PH22 includes, for example, three second unit drive periods U22, that is, a second unit drive period U22a, a second unit drive period U22b, and a second unit drive period U22c, Are continuously configured in this order.

  In the present embodiment, the second unit drive periods U22a to U22c of the second AC period PH22 are the same as the second unit drive periods U21a to U21c of the second AC period PH21 in the first embodiment.

  In the present embodiment, the length t11 of the first AC period PH11 and the length t22 of the second AC period PH22 are different. More specifically, the length t22 of the second AC period PH22 is smaller than the length t11 of the first AC period PH11.

  According to the present embodiment, since the length t11 of the first AC period PH11 is larger than the length t22 of the second AC period PH22, the direction of the first electrode 92 is smaller than that of the second electrode 93 in the control cycle C2. Is more heated. Therefore, by repeating the control cycle C2, the temperature of the entire first electrode 92 becomes high, and the protrusion 552p is more easily melted. The total time in which the control cycle C2 is repeated is, for example, 0.25 seconds (seconds) or more, whereby the first electrode 92 can be effectively heated.

  Note that after repeating the control cycle C2 to some extent, the control cycle with the polarity reversed is repeated a plurality of times with respect to the control cycle C2, so that the protrusions 552p, both of the first electrode 92 and the second electrode 93 The 562p can be melted to promote the growth of the protrusions 552p and 562p.

In the above description, the second unit driving period U22a to U22a to similar to the second unit driving periods U21a to U21c in the second AC period PH21 of the first embodiment are the second AC period PH22 shorter than the first AC period PH11. Although it was set as the period comprised by U22c, it is not restricted to this.
In the present embodiment, as the second AC period shorter than the first AC period PH11, in the same manner as the first embodiment, it is possible to select a period composed of various second unit drive periods.

Third Embodiment
The third embodiment is different from the first embodiment in that a third AC period is provided immediately after the first AC period and the second AC period.
In the following description, the same components as those in the above embodiment may be omitted by the same reference numerals.

FIG. 9 is a diagram showing a drive current waveform DW3 of the drive current I supplied to the discharge lamp 90 of the present embodiment. In FIG. 9, the vertical axis indicates the drive current I, and the horizontal axis indicates the time T.
In the present embodiment, the control unit 40 controls the discharge lamp driving unit 230 in accordance with the drive current waveform DW3 shown in FIG.

  As shown in FIG. 9, in the drive current waveform DW3, a plurality of control cycles C3 are continuously formed. The control cycle C3 includes a first AC period PH11, a third AC period PH31, a second AC period PH21, and a third AC period PH32 in this order. That is, the drive current waveform DW3 (drive current I) has a first AC period PH11, a third AC period PH31, a second AC period PH21, and a third AC period PH32. The third alternating current period PH31 and the third alternating current period PH32 are periods in which an alternating current whose polarity is reversed between the current value Im1 and the current value -Im1 is supplied to the discharge lamp 90 as the driving current I.

  The third AC period PH31 is provided immediately after the first AC period PH11. In the third AC period PH31, a plurality of third unit drive periods U31 each consisting of a first polarity period P31a in which the first electrode 92 becomes an anode and a second polarity period P31b in which the second electrode 93 becomes an anode ing. In the present embodiment, in the third AC period PH31, for example, two third unit drive periods U31, that is, a third unit drive period U31a and a third unit drive period U31b are continuously configured in this order. ing.

  The third AC period PH32 is provided immediately after the second AC period PH21. In the third AC period PH32, a plurality of third unit driving periods U32 each consisting of a first polarity period P32a in which the first electrode 92 becomes an anode and a second polarity period P32b in which the second electrode 93 becomes an anode are continuously configured. ing. In the present embodiment, in the third AC period PH32, for example, two third unit drive periods U32, that is, a third unit drive period U32a and a third unit drive period U32b are continuously configured in this order. ing.

  In the present specification, the fact that the third AC period is provided immediately after the first AC period or the second AC period means that after the first AC period or the second AC period has ended, the third AC period is otherwise It is provided continuously with the 1st exchange period or the 2nd exchange period, without putting the period of a.

In the third unit drive period U31, the length t31a of the first polarity period P31a is equal to the length t31b of the second polarity period P31b.
In the third unit drive period U32, the length t32a of the first polarity period P32a and the length t32b of the second polarity period P32b are equal.

In the drive current waveform DW3 of the present embodiment, the third AC period PH31 and the third AC period PH32 have similar waveforms except that their polarities are reversed.
Therefore, the length t31 of the third AC period PH31 and the length t32 of the third AC period PH32 are equal. In the present embodiment, the length t31 of the third AC period PH31 and the length t32 of the third AC period PH32 are smaller than the length t11 of the first AC period PH11 and the length t21 of the second AC period PH21.

  The frequency of the drive current I in the third AC period PH31, 32 is set according to the purpose. For example, when the electrodes heated in the third AC period PH31, 32 are further heated to have a high temperature, the frequency of the drive current I in the third AC period PH31, 32 is, for example, larger than 10 Hz and about 300 Hz or less Set to a relatively low frequency. By setting in this manner, the electrodes heated in the third AC periods PH 31 and 32 can be further heated, and the temperature of the electrodes can be increased.

  Further, for example, in the case of promoting the growth of the protrusions of the electrode heated and melted in the third AC period PH31, 32, the frequency of the drive current I in the third AC period PH31, 32 is, for example, 600 Hz or more and 1000 Hz. Set to the following relatively high frequency. By setting in this manner, the projections of the electrode heated and melted in the third AC period PH31, 32 solidify, and the growth of the projections is promoted.

  Further, for example, the frequency of the drive current I in the third AC period PH31, 32 can be set to a frequency used to drive the discharge lamp 90 for the purpose of adjusting the shape of the projections of the electrodes.

  Thus, according to the present embodiment, since the third AC period PH31 and the third AC period PH32 are provided immediately after the first AC period PH11 and the second AC period PH21, respectively, as described above By adjusting the frequency of the drive current I in the third AC period PH31, 32, the shapes and growth degree of the protrusions 552p, 562p of the first electrode 92 and the second electrode 93 can be controlled.

  Also, for example, in the case of selecting a method of supplying direct current to the discharge lamp 90 and repeating melting and solidification of the electrode by a combination of direct current and alternating current having a relatively high frequency to promote the growth of protrusions There has been a problem that the temperature of the electrode serving as the cathode is lowered when supplying a direct current. In addition, since the length of the period for supplying the DC current is limited by the polarity inverting circuit 30 of the discharge lamp lighting device 10, it is difficult to increase the time for driving the discharge lamp 90 with a bias of polarity There was a problem.

  On the other hand, according to the present embodiment, since the first alternating current period PH11 and the second alternating current period PH21 are used instead of the direct current, as described in the first embodiment and the second embodiment, In the first alternating current period PH11 and the second alternating current period PH21, a decrease in the temperature of the other electrode with respect to the one electrode to be heated can be suppressed.

  Further, since the drive current waveform DW3 is formed of a combination of alternating current periods, it is hard to be restricted by the polarity inversion circuit 30, and it is easy to extend the time for driving the discharge lamp 90 with a bias of polarity. .

  In the present embodiment, the following configuration can also be adopted.

  In the above description, although the third AC period PH31 is provided immediately after the first AC period PH11 and the third AC period PH32 is provided immediately after the second AC period PH21, the present invention is not limited thereto. In the present embodiment, the third AC period may be provided only immediately after one of the first AC period PH11 and the second AC period PH21. That is, the third AC period may be provided immediately after at least one of the first AC period PH11 and the second AC period PH21.

  In the present embodiment, the lengths t31 and t32 of the third AC periods PH31 and PH32 may be larger than the length t11 of the first AC period PH11 and the length t21 of the second AC period PH21.

  The configurations of the respective periods described in the first to third embodiments can be combined with each other, and the order of the combination, the number of repetitions, and the like are not particularly limited.

  Further, in the above-described embodiment, although an example in which the present invention is applied to a transmissive projector is described, the present invention can also be applied to a reflective projector. Here, the “transmission type” means that the liquid crystal light valve including the liquid crystal panel or the like is of a type that transmits light. "Reflective" means that the liquid crystal light valve is of the type that reflects light. The light modulation device is not limited to a liquid crystal panel or the like, and may be, for example, a light modulation device using a micro mirror.

  In the above embodiment, the example of the projector 500 using the three liquid crystal panels 560R, 560G, 560B (liquid crystal light valves 330R, 330G, 330B) has been described, but the present invention uses only one liquid crystal panel The present invention is also applicable to a projector that has been used or a projector that uses four or more liquid crystal panels.

  As an example, a discharge lamp rated at 200 W was driven in accordance with the drive current waveform DW1 of the first embodiment. The parameters for each period in the examples were as shown in Table 1 above. In Table 1, the lengths of the first AC period PH11 and the second AC period PH21 correspond to 12.54 ms (milliseconds), that is, the half cycle length of the AC current of about 40 Hz, and in each AC period The proportion of the polarity period in which the electrode on the heating side becomes an anode is about 81%. That is, in the first AC period PH11 and the second AC period PH21, the total of the polarity periods in which the electrode on the heating side becomes an anode is 10.14 ms (milliseconds).

  As a comparative example, in the first AC period PH11 and the second AC period PH21, rated 200 W by the alternating current whose polarity is switched every 10.14 ms (milliseconds) which is the total of the polarity period in which the electrode on the heating side becomes an anode. The discharge lamp was driven. An alternating current whose polarity is switched every 10.14 ms (milliseconds) is a square wave alternating current having a frequency of about 49 Hz.

In both the example and the comparative example, the discharge state was observed when the discharge lamp was driven with a driving power of 140 W for 1 hour, and the shape of the projection of the electrode was observed.
As a result, in the comparative example, it was confirmed that the protrusions were deformed and flattened, and flicker was generated.
On the other hand, in the example, it was confirmed that the protrusions were kept thick and the stable discharge was sustained.

  The utility of the present invention has been confirmed by the above examples.

  DESCRIPTION OF SYMBOLS 40 Control part 90 Discharge lamp 92 1st electrode 93 2nd electrode Wd Drive power 200 Light source device 230 Discharge lamp drive part 350 Projection optical system 500 Projector 10 ... Discharge lamp lighting device (discharge lamp drive device), 60 ... Operation detection unit (voltage detection unit), I ... Drive current, Vla ... Lamp voltage (inter-electrode voltage), DW1, DW2, DW3 ... Drive current waveform, PH11 ... 1st alternating current period, P11a, P21a, P22a, P31a, P32a first polarity period, P11b, P21b, P22b, P31b, P32b second polarity period, PH21, PH22 second alternating period, PH31, PH32 third AC period, U11, U11a, U11b, U11c, U11d, U11e, U11f ... 1st unit driving period, U21, U21a, U21b, U21c, U2 d, U21e, U21f, U22, U22a, U22b, U22c ... second unit driving time, U31, U31a, U31b, U32, U32a, U32b ... third unit driving period

Claims (21)

A discharge lamp driver for supplying a drive current to a discharge lamp having a first electrode and a second electrode;
A control unit that controls the discharge lamp driving unit;
Equipped with
The driving current has a first alternating current period and a second alternating current period in which alternating current is supplied to the discharge lamp,
The first alternating current period includes a first polarity period in which the first electrode is an anode and a second polarity period in which the second electrode is an anode, and the length of the first polarity period is the second polarity period. A plurality of first unit drive periods longer than the length are continuously configured,
The second alternating current period includes the first polarity period and the second polarity period, and a plurality of second unit driving periods having a length of the second polarity period larger than a length of the first polarity period are continuously provided. Configured and
The lengths of the first unit drive periods adjacent in time are different from each other,
Wherein temporally adjacent length of the second unit driving period, the discharge lamp driving apparatus according to claim Rukoto different from each other. A discharge lamp driver for supplying a drive current to a discharge lamp having a first electrode and a second electrode;
A control unit that controls the discharge lamp driving unit;
Equipped with
The driving current has a first alternating current period and a second alternating current period in which alternating current is supplied to the discharge lamp,
The first alternating current period includes a first polarity period in which the first electrode is an anode and a second polarity period in which the second electrode is an anode, and the length of the first polarity period is the second polarity period. A plurality of first unit drive periods longer than the length are continuously configured,
The second alternating current period includes the first polarity period and the second polarity period, and a plurality of second unit driving periods having a length of the second polarity period larger than a length of the first polarity period are continuously provided. Configured and
The average length of the first polarity period in the first AC period and the average length of the second polarity period in the second AC period are smaller as the drive power supplied to the discharge lamp is smaller. set the discharge lamp driving apparatus according to claim Rukoto.
A discharge lamp driver for supplying a drive current to a discharge lamp having a first electrode and a second electrode;
A control unit that controls the discharge lamp driving unit;
Equipped with
The driving current has a first alternating current period and a second alternating current period in which alternating current is supplied to the discharge lamp,
The first alternating current period includes a first polarity period in which the first electrode is an anode and a second polarity period in which the second electrode is an anode, and the length of the first polarity period is the second polarity period. A plurality of first unit drive periods longer than the length are continuously configured,
The second alternating current period includes the first polarity period and the second polarity period, and a plurality of second unit driving periods having a length of the second polarity period larger than a length of the first polarity period are continuously provided. Configured and
In the first AC period, the lengths of the plurality of first polarity periods are set to be smaller as the first polarity period provided later in time,
In said second alternating periods, the length of the plurality of the second polarity periods, as the second polarity period provided after time, the discharge lamp driving apparatus according to claim Rukoto is set smaller. The ratio of the length of the first polarity period to the length of the second polarity period in the first unit driving period is 3.0 or more,
The discharge according to any one of claims 1 to 3, wherein a ratio of a length of the second polarity period to a length of the first polarity period in the second unit driving period is 3.0 or more. Light drive. The length of the said 2nd polarity period in the said 1st unit drive period, and the length of the said 1st polarity period in the said 2nd unit drive period are smaller than 1.0 ms, Any one of Claim 1 to 4 The discharge lamp drive device according to claim 1. The discharge lamp drive according to claim 5 , wherein a length of the second polarity period in the first unit driving period and a length of the first polarity period in the second unit driving period are 0.16 ms or more. apparatus. The length of the said 1st polarity period in the said 1st unit drive period and the length of the said 2nd polarity period in the said 2nd unit drive period are 1.0 ms or more, Any one of Claim 1 to 6 The discharge lamp drive device as described in a term. The discharge lamp driving device according to any one of claims 1 to 7 , wherein a length of the first AC period and a length of the second AC period are 5.0 ms or more. The discharge lamp driving device according to any one of claims 1 to 8 , wherein a length of the first AC period and a length of the second AC period are equal. The discharge lamp driving device according to any one of claims 1 to 8 , wherein a length of the first AC period and a length of the second AC period are different from each other. The driving current has a third alternating current period in which alternating current is supplied to the discharge lamp,
The third exchange period is
A plurality of third unit drive periods, each having the same length as the first polarity period and the length of the second polarity period, are continuously formed.
The discharge lamp driving device according to any one of claims 1 to 10 , which is provided immediately after at least one of the first alternating current period and the second alternating current period. The length of the first AC period, and the length of the second alternating periods, as the driving power supplied to the discharge lamp is small, is largely set, according to any one of claims 1 to 11 Discharge lamp drive device. It further comprises a voltage detection unit that detects an inter-electrode voltage between the first electrode and the second electrode,
The discharge lamp driving device according to any one of claims 1 to 12 , wherein a length of the first AC period and a length of the second AC period are set larger as the voltage between the electrodes is larger. . It further comprises a voltage detection unit that detects an inter-electrode voltage between the first electrode and the second electrode,
The average length of the first polarity period in the first AC period and the average length of the second polarity period in the second AC period are set smaller as the inter-electrode voltage is larger. The discharge lamp driving device according to any one of Items 1 to 12 . In the first AC period, lengths of the first polarity periods temporally adjacent to each other across the second polarity period are different from each other.
The discharge lamp drive according to any one of claims 1 to 13 , wherein lengths of the second polarity periods temporally adjacent to each other across the first polarity period in the second AC period are different from each other. apparatus. The ratio of the length of the first polarity period to the length of the second polarity period in the temporally adjacent first unit drive periods is different from each other.
The ratio of the length of the relative length second polarity period of the first polarity period in the second unit driving period temporally adjacent are different from each other, release according to any one of claims 1 to 15 Light drive. The discharge lamp emitting light;
The discharge lamp driving device according to any one of claims 1 to 16 ,
A light source device comprising: A light source device according to claim 17 ;
A light modulation element that modulates light emitted from the light source device according to a video signal;
A projection optical system that projects the light modulated by the light modulation element;
A projector comprising: A discharge lamp driving method for driving a discharge lamp by supplying a drive current to a discharge lamp having a first electrode and a second electrode, comprising:
Supplying a driving current having a first alternating current period in which alternating current is supplied to the discharge lamp and a second alternating current period in which alternating current is supplied to the discharge lamp to the discharge lamp;
The first alternating current period includes a first polarity period in which the first electrode is an anode and a second polarity period in which the second electrode is an anode, and the length of the first polarity period is the second polarity period. A plurality of first unit drive periods longer than the length are continuously configured,
The second alternating current period includes the first polarity period and the second polarity period, and a plurality of second unit driving periods having a length of the second polarity period larger than a length of the first polarity period are continuously provided. Configured and
The lengths of the first unit drive periods adjacent in time are different from each other,
The length of the second unit driving period, the discharge lamp driving method according to claim Rukoto different from one another temporally adjacent. A discharge lamp driving method for driving a discharge lamp by supplying a drive current to a discharge lamp having a first electrode and a second electrode, comprising:
Supplying a driving current having a first alternating current period in which alternating current is supplied to the discharge lamp and a second alternating current period in which alternating current is supplied to the discharge lamp to the discharge lamp;
The first alternating current period includes a first polarity period in which the first electrode is an anode and a second polarity period in which the second electrode is an anode, and the length of the first polarity period is the second polarity period. A plurality of first unit drive periods longer than the length are continuously configured,
The second alternating current period includes the first polarity period and the second polarity period, and a plurality of second unit driving periods having a length of the second polarity period larger than a length of the first polarity period are continuously provided. Configured and
The average length of the first polarity period in the first AC period and the average length of the second polarity period in the second AC period are smaller as the drive power supplied to the discharge lamp is smaller. set to the discharge lamp driving method comprising Rukoto. A discharge lamp driving method for driving a discharge lamp by supplying a drive current to a discharge lamp having a first electrode and a second electrode, comprising:
Supplying a driving current having a first alternating current period in which alternating current is supplied to the discharge lamp and a second alternating current period in which alternating current is supplied to the discharge lamp to the discharge lamp;
The first alternating current period includes a first polarity period in which the first electrode is an anode and a second polarity period in which the second electrode is an anode, and the length of the first polarity period is the second polarity period. A plurality of first unit drive periods longer than the length are continuously configured,
The second alternating current period includes the first polarity period and the second polarity period, and a plurality of second unit driving periods having a length of the second polarity period larger than a length of the first polarity period are continuously provided. Configured and
In the first alternating current period, lengths of the plurality of first polarity periods are set to be smaller as the first polarity period provided later in time,
In said second alternating periods, the length of the plurality of the second polarity period, the more the second polarity period provided after time, the discharge lamp driving method characterized that you set smaller.

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