JP5773025B2 - Projector and projector system - Google Patents

Description

  The present invention relates to a projector.

  Projectors using discharge lamps such as high-pressure mercury lamps and metal halide lamps have been put into practical use. As such a projector, for example, Patent Document 1 discloses a projector having means for changing the intensity of a light source in accordance with a color separation means in synchronization with a video signal. However, Patent Document 2 describes a problem that if the intensity of the light source is simply changed, the electrodes of the discharge lamp are significantly consumed.

  In recent years, projectors that output stereoscopic images using discharge lamps such as high-pressure mercury lamps and metal halide lamps have been put into practical use.

  One of the three-dimensional video output methods is a method of switching the right-eye video and the left-eye video alternately and outputting them alternately (for example, an active shutter glasses method such as “XPAND beond cinema (trademark of X6D Limited)”) There is. In this method, using active shutter glasses synchronized with the video signal, the right-eye video is shown to the right eye and the left-eye video is shown to the left eye, so that the video is shown in three dimensions using the parallax of the left and right eyes. .

JP 2003-102030 A JP 2009-237302 A

  When three-dimensional images are projected by alternately outputting right-eye and left-eye images, the amount of light entering the right and left eyes is less than half compared to the case of projecting conventional planar images (two-dimensional images). It becomes. In addition, when a crosstalk occurs in which the right-eye video enters the left eye or the left-eye video enters the right eye, the video is not perceived as a three-dimensional image, so a period in which both active shutters are closed is required. Therefore, when a stereoscopic video is projected by a method of alternately outputting a right-eye video and a left-eye video, there is a problem that the video looks darker than when a conventional planar video is projected. In order to make the image look brighter, it may be possible to simply increase the driving power, but there are problems such as increasing the power consumption of the projector and promoting the deterioration of peripheral parts caused by increasing the driving power. .

  In order to make the image appear brighter, if the brightness of the discharge lamp is reduced while both active shutters are closed and the brightness of the discharge lamp is increased while either active shutter is open, the discharge lamp Since the temperature of the electrode of the discharge lamp is lowered during the period when the brightness of the lamp is lowered and the meltability of the electrode tip becomes insufficient, the electrode may be deformed. If the electrode is deformed, it may cause flicker.

  In particular, when the driving current of the discharge lamp decreases with the progress of the deterioration state of the discharge lamp, the brightness of the discharge lamp decreases and the meltability of the electrode tip becomes insufficient and the electrode tends to be deformed. Therefore, special consideration is required to project a stereoscopic image so as to look bright while suppressing deformation of the electrodes.

  The present invention has been made in view of the above problems. According to some aspects of the present invention, it is possible to provide a projector capable of projecting an image so as to appear bright while suppressing deformation of the electrodes.

  The projector according to the present invention is a projector that switches between a first video and a second video alternately at a given switching timing, and outputs a discharge lamp and a driving current for driving the discharge lamp to the discharge lamp. Including a discharge lamp driving unit that supplies power, a state detection unit that detects a deterioration state of the discharge lamp, and a control unit that controls the discharge lamp driving unit, and is sandwiched between the switching timings that are temporally adjacent to each other Starts in the first period and ends in the second period, and the control unit causes the absolute value of the drive current to be relatively small in the first period and relatively large in the second period. The discharge lamp drive unit is controlled, and in the second period, the discharge lamp drive unit is controlled to supply an alternating current to the discharge lamp as the drive current, and as the deterioration state progresses The drive power At least a portion of the frequency for controlling the discharge lamp driving unit to be lower in the.

  The state detection unit, for example, as a value indicating the degree of the deterioration state, for example, the discharge lamp drive voltage, the discharge lamp drive voltage change over time, the discharge lamp light quantity, the discharge lamp light quantity change over time, the discharge lamp cumulative lighting time Etc. may be detected.

  When the deterioration state progresses, the meltability of the electrode decreases, and the electrode may be deformed. According to the present invention, the discharge lamp drive unit is controlled so that the frequency of at least a part of the drive current in the second period decreases as the deterioration state of the discharge lamp progresses. The time for the current to flow becomes longer. Therefore, the meltability of the electrode in the second period can be improved. Therefore, deformation of the electrode can be suppressed.

  According to the present invention, the control unit controls the discharge lamp driving unit so that the absolute value of the driving current is relatively small in the first period and relatively large in the second period. A projector that can project the image so that it looks bright.

  In the projector, the control unit controls the discharge lamp driving unit so that an alternating current is supplied to the discharge lamp as the driving current in the first period, and with the progress of the deterioration state, The discharge lamp driving unit may be controlled such that at least a part of the driving current has a higher frequency.

  This shortens the time during which currents of the same polarity flow in the first period. Therefore, the time during which the low temperature state continues in the first period is shortened. Therefore, deformation of the electrode can be suppressed.

  In the projector, the control unit may control the discharge lamp driving unit so that an average value of driving power throughout the first period and the second period is constant.

  Thereby, deterioration of the components which comprise a discharge lamp drive part can be suppressed.

Explanatory drawing which shows the optical system of the projector 500 which concerns on this embodiment. 4 is an explanatory diagram illustrating a configuration of a light source device 200. FIG. FIG. 3 is a diagram illustrating an example of a circuit configuration of a projector according to the present embodiment. The figure which shows an example of the circuit structure of the discharge lamp lighting device. The figure for demonstrating the other structural example of the control part. 6A to 6D are explanatory diagrams showing the relationship between the polarity of the drive current I supplied to the discharge lamp 90 and the electrode temperature. The figure for demonstrating a 1st period, a 2nd period, and switching timing. 6 is a flowchart showing a control example of the projector 500 according to the present embodiment. A table showing an example of a table of driving conditions. FIG. 10 is a timing chart showing an example of waveforms under the driving conditions shown in FIG. FIG. 10 is a timing chart showing an example of waveforms under the driving conditions shown in FIG. FIG. 10 is a timing chart showing an example of waveforms under the driving conditions shown in FIG. FIG. 10 is a timing chart showing an example of waveforms under the driving conditions shown in FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. Also, not all of the configurations described below are essential constituent requirements of the present invention.

1. FIG. 1 is an explanatory diagram showing an optical system of a projector 500 according to the present embodiment. The projector 500 includes a light source device 200, a collimating lens 305, an illumination optical system 310, a color separation optical system 320, three liquid crystal light valves 330R, 330G, and 330B, a cross dichroic prism 340, and a projection optical system 350. And have.

  The light source device 200 includes a light source unit 210 and a discharge lamp lighting device 10. The light source unit 210 includes a main reflecting mirror 112, a sub reflecting mirror 50 (described later), and a discharge lamp 90. The discharge lamp lighting device 10 supplies power to the discharge lamp 90 to light the discharge lamp 90. The main reflecting mirror 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. Light from the light source unit 210 passes through the collimating lens 305 and enters the illumination optical system 310. The collimating lens 305 collimates the light from the light source unit 210.

  The illumination optical system 310 makes the illuminance of light from the light source device 200 uniform in the liquid crystal light valves 330R, 330G, and 330B. The illumination optical system 310 aligns the polarization direction of light from the light source device 200 in one direction. This is because the light 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 (R), green (G), and blue (B). The three color lights are respectively modulated by the liquid crystal light valves 330R, 330G, and 330B associated with the respective colors. The liquid crystal light valves 330R, 330G, and 330B include liquid crystal panels 560R, 560G, and 560B (described later) and polarizing plates (not shown) disposed on the light incident side and the emission 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 a screen (not shown). Thereby, an image is displayed on the screen.

  Note that various well-known configurations can be adopted as the configurations 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.

  FIG. 2 is an explanatory diagram showing the configuration of the light source device 200. The light source device 200 includes a light source unit 210 and a discharge lamp lighting device 10. In the drawing, a cross-sectional view of the light source unit 210 is shown. The light source unit 210 includes a main reflecting mirror 112, a discharge lamp 90, and a sub reflecting mirror 50.

  The shape of the discharge lamp 90 is a rod shape extending along the irradiation direction D from the first end 90e1 to the second end 90e2. The material of the discharge lamp 90 is a translucent material such as quartz glass, for example. A central portion of the discharge lamp 90 swells in a spherical shape, and a discharge space 91 is formed therein. The discharge space 91 is filled with a gas that is a discharge medium containing mercury, a rare gas, a metal halogen compound, and the like.

  The discharge lamp 90 includes a first electrode 92 and a second electrode 93. In the example shown in FIG. 2, the first electrode 92 and the second electrode 93 are provided so as to protrude into the discharge space 91. The first electrode 92 is disposed on the first end 90 e 1 side of the discharge space 91, and the second electrode 93 is disposed on the second end 90 e 2 side of the discharge space 91. The shape of the first electrode 92 and the second electrode 93 is a rod shape extending along the optical axis AX. In the discharge space 91, the electrode tip portions (also referred to as “discharge ends”) of the first electrode 92 and the second electrode 93 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 that passes through 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 that passes through 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. Further, as each 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 a drive current 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. Light (discharge light) generated by the arc discharge is radiated in all directions from the discharge position, as indicated by the dashed arrows.

  The main reflecting mirror 112 is fixed to the first end 90 e 1 of the discharge lamp 90 by a fixing member 114. The shape of the reflecting surface (the surface on the discharge lamp 90 side) of the main reflecting mirror 112 is a spheroid shape. The main reflecting mirror 112 reflects the discharge light in the irradiation direction D. The shape of the reflecting surface of the main reflecting mirror 112 is not limited to the spheroid shape, and various shapes that reflect the discharge light toward the irradiation direction D can be employed. For example, a rotating parabolic shape may be adopted. In this case, the main reflecting mirror 112 can convert the discharge light into light substantially parallel to the optical axis AX. Therefore, the collimating lens 305 can be omitted.

  The sub-reflecting 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 reflective surface (surface on the discharge lamp 90 side) of the sub-reflecting mirror 50 is a spherical shape that surrounds the second end 90e2 side of the discharge space 91. The sub-reflecting mirror 50 reflects the discharge light toward the main reflecting mirror 112. Thereby, the utilization efficiency of the light radiated | emitted from the discharge space 91 can be improved.

  As a material for the fixing members 114 and 522, any heat-resistant material (for example, an inorganic adhesive) that can withstand the heat generated by the discharge lamp 90 can be used. Further, 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, and any method can be used. It can be adopted. For example, the discharge lamp 90 and the main reflecting mirror 112 may be independently fixed to a housing (not shown) of the projector. The same applies to the sub-reflecting mirror 50.

2. FIG. 3 is a diagram illustrating an example of a circuit configuration of the projector according to the present embodiment. In addition to the optical system described above, the projector 500 includes an image signal conversion unit 510, a DC power supply device 80, a discharge lamp lighting device 10, a discharge lamp 90, liquid crystal panels 560R, 560G, 560B, an image processing device 570, a CPU ( Central Processing Unit) 580 may be included. Further, the projector system 400 including the projector 500 and the active shutter glasses 410 may be configured.

  The image signal converter 510 converts an externally input image signal 502 (such as a luminance-color difference signal or an analog RGB signal) into a digital RGB signal having a predetermined word length to generate image signals 512R, 512G, and 512B. This is supplied to the image processing device 570. In addition, when a stereoscopic video signal in which the first video and the second video are alternately switched at a given switching timing is input as the image signal 502, the image signal conversion unit 510 receives the first video and the second video. The synchronization signal 514 is supplied to the CPU 580 based on the switching timing.

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

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

  The discharge lamp lighting device 10 generates a high voltage between the electrodes of the discharge lamp 90 at the time of startup to cause a dielectric breakdown to form a discharge path, and thereafter supplies a driving current I for the discharge lamp 90 to maintain a discharge.

  The liquid crystal panels 560R, 560G, and 560B modulate the luminance of the color light incident on each liquid crystal panel via the optical system described above based on the drive signals 572R, 572G, and 572B, respectively.

  The CPU 580 controls the operation from the start of lighting of the projector to the turning off of the projector. For example, a lighting command or a lighting command may be output to the discharge lamp lighting device 10 via the communication signal 582. Further, the CPU 580 may receive lighting information of the discharge lamp 90 from the discharge lamp lighting device 10 via the communication signal 584. Further, based on the synchronization signal 514, the CPU 580 outputs a control signal 586 for controlling the active shutter glasses 410 in synchronization with the image signal 502 to the active shutter glasses 410 via wired or wireless communication means. Also good.

  The active shutter glasses 410 may include a right shutter 412 and a left shutter 414. The right shutter 412 and the left shutter 414 are controlled to open and close based on a control signal 586. When the user wears the active shutter glasses 410, the right shutter 412 is closed, so that the visual field on the right eye side can be blocked. Further, when the user wears the active shutter glasses 410, the left shutter 414 is closed so that the visual field on the left eye side can be blocked. The right shutter 412 and the left shutter 414 may be configured with, for example, a liquid crystal shutter.

3. Configuration of Discharge Lamp Lighting Device in the Present Embodiment FIG. 4 is a diagram illustrating an example of a circuit configuration of the discharge lamp lighting device 10.

  The discharge lamp lighting device 10 includes a power control circuit 20. The power control circuit 20 generates driving power to be supplied to the discharge lamp 90. In the present embodiment, the power control circuit 20 includes a down chopper circuit that receives the DC power supply 80 and steps down the input voltage to output a DC current Id.

  The power control circuit 20 can include a switch element 21, a diode 22, a coil 23, and a capacitor 24. The switch element 21 can be composed 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 80, and the other end is connected to the cathode terminal of the diode 22 and one end of the coil 23. One end of a capacitor 24 is connected to the other end of the coil 23, 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 a control terminal of the switch element 21 from a control unit 40 (described later), and ON / OFF of the switch element 21 is controlled. For example, a PWM (Pulse Width Modulation) control signal may be used as the current control signal.

  Here, 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 through a path passing through the capacitor 24 and the diode 22. As a result, a direct current Id corresponding to the proportion of time during which the switch element 21 is turned on is generated.

  The discharge lamp lighting device 10 includes a polarity inversion circuit 30. The polarity inversion circuit 30 receives the direct current Id output from the power control circuit 20 and reverses the polarity at a given timing, so that the polarity inversion circuit 30 can be a direct current that lasts for a controlled time or has an arbitrary frequency. The drive current I is generated and output. 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 configured by transistors, and the first switch element 31 connected in series. The switch element 31 and the second switch element 32, and the third switch element 33 and the fourth switch element 34 connected in series are connected in parallel to each other. The polarity inversion control signal is input from the control unit 40 to the 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. Based on this, ON / OFF of the first switch element 31, the second switch element 32, the third switch element 33, and the fourth switch element 34 is controlled.

  The polarity inversion circuit 30 repeats the ON / OFF operation of the first switch element 31 and the fourth switch element 34, and the second switch element 32 and the third switch element 33 alternately. The polarity of the direct current Id to be output is alternately inverted, and the common connection point between the first switch element 31 and the second switch element 32 and the common connection between the third switch element 33 and the fourth switch element 34. From this point, a drive current I that is a direct current that lasts for a controlled time or an alternating current that has a controlled frequency is generated and output.

  That is, 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 turned OFF, and the first switch element 31 and the fourth switch element 34 are When the switch is OFF, the second switch element 32 and the third switch element 33 are controlled to be turned 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. To do. In addition, when the second switch element 32 and the third switch element 33 are ON, a drive current I flowing from the one end of the capacitor 24 to the third switch element 33, the discharge lamp 90, and the second switch element 32 is generated. To do.

  In the present embodiment, the power control circuit 20 and the polarity inversion circuit 30 are combined to correspond to the discharge lamp driving unit 230. That is, the discharge lamp driving unit 230 supplies the driving current I for driving the discharge lamp 90 to the discharge lamp 90.

  The discharge lamp lighting device 10 includes a control unit 40. The control unit 40 controls the discharge lamp driving unit 230. In the example shown in FIG. 4, the control unit 40 controls the power control circuit 20 and the polarity inversion circuit 30 to determine the holding time during which the drive current I continues with the same polarity, the current value of the drive current I, the frequency, etc. Control. The control unit 40 performs polarity reversal control for controlling the holding time for the drive current I to remain the same polarity, the frequency of the drive current I, and the like based on the polarity reversal timing of the drive current I with respect to the polarity reversal circuit 30. Further, the control unit 40 performs current control for controlling the current value of the output direct current Id to the power control circuit 20.

  Although the configuration of the control unit 40 is not particularly limited, in the present embodiment, the control unit 40 includes a system controller 41, a power control circuit controller 42, and a polarity inversion circuit controller 43. Note that a part or all of the control unit 40 may be configured by a semiconductor integrated circuit.

  The system controller 41 controls the power control circuit 20 and the polarity reversing circuit 30 by controlling the power control circuit controller 42 and the polarity reversing circuit controller 43. The system controller 41 controls the power control circuit controller 42 and the polarity inversion circuit controller 43 based on the drive voltage Vla and the drive current I detected by the voltage detection unit 60 provided in the discharge lamp lighting device 10 described later. Good.

  In the present embodiment, the system controller 41 includes a 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 information stored in the storage unit 44. The storage unit 44 may store information on drive parameters such as a holding time during 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 the 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.

  Note that the control unit 40 can be realized by a dedicated circuit to perform the above-described control and various kinds of control of processing to be described later. For example, a control in which a CPU (Central Processing Unit) is stored in the storage unit 44 or the like. It is also possible to function as a computer by executing the program and to 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. 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 reversal control unit 40-2 that controls the polarity reversing circuit 30 according to a control program. May be.

  In the example shown in FIG. 4, the control unit 40 is configured as a part of the discharge lamp lighting device 10. However, the CPU 580 may be configured to perform a part of the function of the control unit 40. .

  The discharge lamp lighting device 10 may include an operation detection unit. The operation detection unit may include, for example, a voltage detection unit 60 that detects the drive voltage Vla of the discharge lamp 90 and outputs drive voltage information, and a current detection unit that detects the drive current I and outputs drive current information. In the present embodiment, the voltage detection unit 60 includes first and second resistors 61 and 62.

  The voltage detector 60 corresponds to the state detector in the present invention. That is, the state detection unit (voltage detection unit 60) detects the drive voltage Vla as a value representing the degree of deterioration of the electrode.

  In the present embodiment, the voltage detection unit 60 detects the drive voltage Vla by 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. In the present embodiment, the current detection unit detects the drive current I based on the voltage generated in the third resistor 63 connected in series to the discharge lamp 90.

  The discharge lamp lighting device 10 may include an igniter circuit 70. The igniter circuit 70 operates only at the start of lighting of the discharge lamp 90. At the start of lighting of the discharge lamp 90, the igniter circuit 70 breaks down the insulation between the electrodes of the discharge lamp 90 (between the first electrode 92 and the second electrode 93). 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.

4). Relationship between Polarity of Driving Current and Electrode Temperature FIGS. 6A to 6D are explanatory diagrams showing the relationship between the polarity of the driving current I supplied to the discharge lamp 90 and the electrode temperature. 6A and 6B show the operating state of the first electrode 92 and the second electrode 93. FIG. In the drawing, the tip portions of the first electrode 92 and the second electrode 93 are shown. Protrusions 552p and 562p are provided at 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 is mainly generated between the protrusion 552p and the protrusion 562p. In this 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 is no protrusion. However, such protrusions may be omitted.

  FIG. 6A shows a first polarity state P1 in which the first electrode 92 operates as an anode and the second electrode 93 operates as a cathode. In the first polarity state P1, 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). Heat is generated by this collision, and the temperature of the tip (projection 552p) of the anode (first electrode 92) rises.

  FIG. 6B shows a second polarity state P2 in which the first electrode 92 operates as a cathode and the second electrode 93 operates as an anode. In the second polarity state P2, electrons move from the first electrode 92 to the second electrode 93, contrary to the first polarity state P1. As a result, the temperature of the tip (projection 562p) of the second electrode 93 rises.

  Thus, the temperature of the anode tends to be higher than that of the cathode. Here, the continued high state of the temperature of one electrode compared to the other electrode can cause various problems. For example, when the tip of the high temperature electrode melts excessively, unintended electrode deformation may occur. As a result, the arc length may deviate from an appropriate value. Moreover, when the melting | fusing of the front-end | tip of a low-temperature electrode is inadequate, the fine unevenness | corrugation produced at the front-end | tip may remain without melting. As a result, a so-called arc jump may occur (the arc position moves without being stable).

  As a technique for suppressing such inconvenience, AC driving in which the polarity of each electrode is repeatedly changed can be used. FIG. 6C is a timing chart showing an example of the drive current I supplied to the discharge lamp 90 (FIG. 2). The horizontal axis indicates time T, and the vertical axis indicates the current value of the drive current I. The drive current I indicates the current flowing through the discharge lamp 90. A positive value indicates the first polarity state P1, and a negative value indicates the second polarity state P2. In the example shown in FIG. 6C, a rectangular wave alternating current is used as the drive current I. In the example shown in FIG. 6C, the first polarity state P1 and the second polarity state P2 are alternately repeated. Here, the first polarity section Tp indicates the time that the first polarity state P1 continues, and the second polarity section Tn indicates the time that the second polarity state P2 continues. In the example shown in FIG. 6C, the average current value in the first polarity section Tp is Im1, and the average current value in the second polarity section Tn is -Im2. The frequency of the drive current I suitable for driving the discharge lamp 90 can be determined experimentally according to the characteristics of the discharge lamp 90 (for example, a value in the range of 30 Hz to 1 kHz is adopted). Other values Im1, −Im2, Tp, and Tn can be determined experimentally in the same manner.

  FIG. 6D is a timing chart showing the temperature change of the first electrode 92. The horizontal axis represents time T, and the vertical axis represents temperature H. In the first polarity state P1, the temperature H of the first electrode 92 increases, and in the second polarity state P2, the temperature H of the first electrode 92 decreases. Further, since the first polarity state P1 and the second polarity state P2 state are repeated, the temperature H periodically changes between the minimum value Hmin and the maximum value Hmax. Although illustration is omitted, the temperature of the second electrode 93 changes in a phase opposite to the temperature H of the first electrode 92. That is, in the first polarity state P1, the temperature of the second electrode 93 decreases, and in the second polarity state P2, the temperature of the second electrode 93 increases.

  In the first polarity state P1, the tip of the first electrode 92 (projection 552p) is melted, so that the tip of the first electrode 92 (projection 552p) is smooth. Thereby, the movement of the discharge position in the 1st electrode 92 can be suppressed. In addition, since the temperature at the tip of the second electrode 93 (projection 562p) falls, excessive melting of the second electrode 93 (projection 562p) is suppressed. Thereby, unintended electrode deformation can be suppressed. In the second polarity state P2, the positions of the first electrode 92 and the second electrode 93 are reversed. Therefore, by repeating the two states P1 and P2, problems in each of the first electrode 92 and the second electrode 93 can be suppressed.

  Here, when the waveform of the current I is symmetric, that is, when the waveform of the current I satisfies the condition “| Im1 | = | −Im2 |, Tp = Tn”, the first electrode 92 and the second electrode 93, the condition of the supplied power is the same. Therefore, if the first electrode 92 and the second electrode 93 have the same thermal conditions (ease of temperature rise and fall), the temperature difference between the first electrode 92 and the second electrode 93 is estimated to be small. Is done.

  Further, if the electrode is heated too much over a wide range (an arc spot (a hot spot on the electrode surface accompanying arc discharge) becomes large), the shape of the electrode is destroyed due to excessive melting. On the other hand, if the electrode is too cold (the arc spot is small), the tip of the electrode cannot be melted sufficiently, and the tip cannot be returned smoothly, that is, the tip of the electrode is easily deformed. Therefore, when the uniform energy supply state is continued with respect to the electrode, the tip of the electrode (the protrusion 552p and the protrusion 562p) easily deforms into an unintended shape.

5. Next, a specific example of control of the drive current I in the projector 500 according to this embodiment will be described.

  FIG. 7 is a diagram for describing the first period, the second period, and the switching timing. FIG. 7 shows the contents of the drive signals 572R, 572G, and 572B, the opening / closing state of the right shutter 412, the opening / closing state of the left shutter 414, the first period and the second period, and the switching timing in order from the top. Yes. The horizontal axis in FIG. 7 is time. In the following, an example will be described in which the viewer is stereoscopically viewed with the first video and the second video as the left-eye video and the right-eye video, respectively.

  In the example shown in FIG. 7, the drive signals 572R, 572G, and 572B are the right-eye video as the first video from time t1 to time t3, and the left-eye as the second video from time t3 to time t5. The driving signal corresponds to the right-eye video as the first video from time t5 to time t7, and the left-eye video as the second video from time t7 to time t9. Therefore, in the example shown in FIG. 7, the projector 500 uses the time t1, the time t3, the time t5, the time t7, and the time t9 as switching timings, and the right-eye video as the first video and the left-eye video as the second video. And output alternately.

  The period between the temporally adjacent switching timings starts with the first period and ends with the second period. In the example illustrated in FIG. 7, for example, the period between the time t1 and the time t3 that is the switching timing starts with a first period from the time t1 to the time t2, and is between the time t2 and the time t3. Ends in the second period. The same applies to a period sandwiched between time t3 and time t5 serving as switching timing, a period sandwiched between time t5 and time t7 serving as switching timing, and a period sandwiched between time t7 and time t9 serving as switching timing. In the example shown in FIG. 7, the length of the first period is the same as the length of the second period, but the length of the first period and the length of the second period are appropriately set as necessary. Can be set. In addition, a third period may exist between the first period and the second period. In the third period, control different from the control of the drive current I in the first period and the second period described later may be performed.

  The right shutter 412 is in an open state during at least a part of the period in which the drive signals 572R, 572G, and 572B corresponding to the right-eye video as the first video are input to the liquid crystal panels 560R, 560G, and 560B. In the example shown in FIG. 7, the right shutter 412 is in a closed state from time t1 to time t2, and is in an open state from time t2 to time t3. In the example shown in FIG. 7, the right shutter 412 is set to the time when the drive signals 572R, 572G, and 572B corresponding to the left-eye video as the second video are input to the liquid crystal panels 560R, 560G, and 560B. It begins to close from t3, finishes closing between time t3 and time t4, and is closed from time t4 to time t5. The change in the open / close state of the right shutter 412 from time t5 to time t9 is the same as the change in the open / close state from time t1 to time t5.

  The left shutter 414 is in an open state during at least a part of the period in which the drive signals 572R, 572G, and 572B corresponding to the left-eye video as the second video are input to the liquid crystal panels 560R, 560G, and 560B. In the example shown in FIG. 7, the left shutter 414 is in a closed state from time t3 to time t4, and is in an open state from time t4 to time t5. In the example shown in FIG. 7, the left shutter 414 is set to the time during the period in which the drive signals 572R, 572G, and 572B corresponding to the right-eye video as the first video are input to the liquid crystal panels 560R, 560G, and 560B. It starts to close from t1, finishes closing between time t1 and time t2, and is closed from time t2 to time t3. The change in the open / close state of the left shutter 414 between the time t5 and the time t9 is the same as the change in the open / close state between the time t1 and the time t5.

  In the example shown in FIG. 7, the right shutter 412 is closed during a period in which the drive signals 572R, 572G, and 572B corresponding to the right-eye video as the first video are input to the liquid crystal panels 560R, 560G, and 560B. The period corresponds to the first period, and the period in which the right shutter 412 is open corresponds to the second period. In the example shown in FIG. 7, the left shutter 414 is closed during the period in which the drive signals 572R, 572G, and 572B corresponding to the left-eye video as the second video are input to the liquid crystal panels 560R, 560G, and 560B. The period during which the left shutter 414 is open corresponds to the first period, and the period during which the left shutter 414 is open corresponds to the second period. In the example shown in FIG. 7, in the first period, there is a period in which both the right shutter 412 and the left shutter 414 are closed.

  In the projector 500 according to the present embodiment, the control unit 40 controls the discharge lamp driving unit 230 so that the absolute value of the driving current I is relatively small in the first period and relatively large in the second period. In the second period, the discharge lamp driving unit 230 is controlled so that an alternating current is supplied to the discharge lamp 90 as the driving current I, and the driving current I is increased as the deterioration state of the discharge lamp 90 progresses. The discharge lamp driving unit 230 is controlled so as to reduce the frequency of.

  The state detection unit, for example, as a value representing the degree of the deterioration state, for example, the drive voltage Vla of the discharge lamp 90, the time change of the drive voltage Vla of the discharge lamp 90, the light quantity of the discharge lamp 90, the time change of the light quantity of the discharge lamp 90, The accumulated lighting time of the discharge lamp 90 may be detected. In the present embodiment, the voltage detection unit 60 (state detection unit) detects the drive voltage Vla of the discharge lamp 90 as the deterioration state of the discharge lamp 90.

  When the deterioration state of the first electrode 92 and the second electrode 93 of the discharge lamp 90 progresses, the distance between the first electrode 92 and the second electrode 93 (interelectrode distance) increases. As the interelectrode distance increases, the drive voltage Vla increases. That is, the drive voltage Vla increases as the deterioration state of the discharge lamp 90 progresses.

  FIG. 8 is a flowchart illustrating a control example of the projector 500 according to the present embodiment. In the flowchart shown in FIG. 8, control from when the discharge lamp 90 is steadily lit until it is turned off is shown.

  First, the voltage detector 60 detects the drive voltage Vla (step S100). Next, the control unit 40 selects a drive condition corresponding to the drive voltage Vla detected in step S100 from the table stored in the storage unit 44 (step S102).

  FIG. 9 is a table showing an example of a drive condition table. In the example shown in FIG. 9, the “waveform” is a waveform example shown in FIGS. 10A to 10D described later, f2 is the frequency of the drive current I in the second period, and f1 is the frequency of the drive current I in the first period. Represents.

  After selecting the drive condition in step S102 of FIG. 8, the control unit 40 determines whether or not the drive condition needs to be changed (step S104). When the control unit 40 determines that the drive condition needs to be changed (YES in step S104), the drive unit 90 is changed to the drive condition selected in step S102 and the discharge lamp 90 is driven (step S106). . When the control unit 40 determines that it is not necessary to change the driving condition (NO in step S104), the discharge lamp 90 is continuously driven under the previous driving condition.

  In the case of NO in step S104 and after step S106, the control unit 40 determines whether or not there is an instruction to turn off the discharge lamp 90 (step S108). When the control unit 40 determines that there is a turn-off command (YES in step S108), the lighting of the discharge lamp 90 is ended (turned off). When the control unit 40 determines that there is no turn-off command (NO in step S108), the control from step S100 to step S108 is repeated until there is a turn-off command.

  10A to 10D are timing charts showing examples of waveforms under the driving conditions shown in FIG. 10A shows the waveform A shown in FIG. 9 when the driving voltage Vla is 60V, FIG. 10B shows the waveform B shown in FIG. 9 when the driving voltage Vla is 80V, and FIG. 10C shows the driving voltage Vla of 100V. 9 corresponds to the waveform D shown in FIG. 9 when the drive voltage Vla is 110V. In the example shown in FIGS. 10A to 10D, the absolute value of the drive current I in the first period is I1, the absolute value of the drive current I in the second period is I2, and I1 <I2. In the example shown in FIGS. 10A to 10D, the length of the first period and the length of the second period are the same length.

  In the example illustrated in FIGS. 10A to 10D, the control unit 40 controls the discharge lamp driving unit 230 so that the average value of the driving power throughout the first period and the second period is constant. Thereby, deterioration of the components which comprise a discharge lamp drive part can be suppressed.

  In the second period, the control unit 40 controls the discharge lamp driving unit 230 so that an alternating current is supplied to the discharge lamp 90 as the driving current I, and the driving current increases as the deterioration state of the discharge lamp 90 progresses. The discharge lamp driving unit is controlled so that at least a part of the frequency of I is low. In the example shown in FIG. 9 and FIGS. 10A to 10D, the control unit 40 causes the discharge lamp 90 to supply an alternating current having a constant frequency during the second period as the drive current I during the second period. The drive unit 230 is controlled, and the discharge lamp drive unit 230 is controlled so that the frequency of the drive current I decreases as the deterioration state of the discharge lamp 90 progresses.

  As a result, the time during which currents of the same polarity flow in the second period becomes longer. Therefore, the meltability of the electrode in the second period can be improved. Therefore, deformation of the electrode can be suppressed. In addition, when the deterioration state of the discharge lamp 90 is not progressing, it is possible to suppress adverse effects such as blackening caused by the excessively high meltability of the electrode by not increasing the meltability of the electrode more than necessary.

  In the example shown in FIGS. 10A to 10C, the control unit 40 causes the discharge lamp driving unit 230 to supply the discharge lamp 90 with an alternating current that is an integral multiple of one cycle as the driving current I in the second period. Is controlling. Thereby, the heat load balance of the electrode of a discharge lamp can be maintained. Therefore, it can suppress that the electrode of a discharge lamp wears out unevenly.

  In the example shown in FIG. 10D, since the frequency of the drive current I is low, the polarity is not inverted in the second period. That is, paying attention to one second period, the drive current I can be regarded as a direct current. In such a case, currents having opposite polarities may be used as the drive current I in two second periods sandwiching one first period in time. Thereby, the heat load balance of the electrode of a discharge lamp can be maintained. Therefore, it can suppress that the electrode of a discharge lamp wears out unevenly.

  Further, the control unit 40 may control the discharge lamp driving unit 230 such that an alternating current having a plurality of types of frequencies is supplied to the discharge lamp 90 as the driving current I in the second period. In this case, the control unit 40 controls the discharge lamp driving unit 230 so that the frequency of at least a part of the alternating currents having a plurality of types of frequencies in the second period of the driving current I decreases as the discharge lamp 90 deteriorates. May be. In other words, as the discharge lamp 90 is deteriorated, the control unit 40 uses the discharge lamp 90 to generate an alternating current having a lower average frequency (for example, a frequency per one period of the drive current I) during the second period as the drive current I. The discharge lamp drive 230 may be controlled so as to be supplied.

  As a result, the time during which currents of the same polarity flow in the second period becomes longer. Therefore, the meltability of the electrode in the second period can be improved. Therefore, deformation of the electrode can be suppressed. In addition, when the deterioration state of the discharge lamp 90 is not progressing, it is possible to suppress adverse effects such as blackening caused by the excessively high meltability of the electrode by not increasing the meltability of the electrode more than necessary.

  In the first period, the control unit 40 controls the discharge lamp driving unit 230 so that an alternating current is supplied to the discharge lamp 90 as the driving current I, and the driving current is increased as the deterioration state of the discharge lamp 90 progresses. The discharge lamp driving unit 230 may be controlled so that the frequency of at least a part of I is increased. In the example shown in FIGS. 9 and 10A to 10D, the control unit 40 causes the discharge lamp 90 to supply an alternating current having a constant frequency during the first period as the drive current I in the first period. The drive unit 230 is controlled, and the discharge lamp drive unit 230 is controlled such that the frequency of the drive current I increases as the deterioration state of the discharge lamp 90 progresses.

  This shortens the time during which currents of the same polarity flow in the first period. Therefore, the time during which the low temperature state continues in the first period is shortened. Therefore, deformation of the electrode can be suppressed.

  In the example shown in FIGS. 10A to 10D, the control unit 40 causes the discharge lamp driving unit 230 to supply the discharge lamp 90 with an alternating current that is an integral multiple of one cycle as the driving current I in the first period. Is controlling. Thereby, the heat load balance of the electrode of a discharge lamp can be maintained. Therefore, it can suppress that the electrode of a discharge lamp wears out unevenly.

  Note that the drive current I in the first period can be set to a low frequency that does not reverse the polarity in the first period. That is, when focusing on one first period, the driving current I may be regarded as the same as the direct current. In such a case, currents having opposite polarities may be used as the drive current I in two first periods sandwiching one second period in time. Thereby, the heat load balance of the electrode of a discharge lamp can be maintained. Therefore, it can suppress that the electrode of a discharge lamp wears out unevenly.

  Further, the control unit 40 may control the discharge lamp driving unit 230 such that an alternating current having a plurality of types of frequencies is supplied to the discharge lamp 90 as the driving current I during the first period. In this case, the control unit 40 causes the discharge lamp driving unit 230 to increase the frequency of at least a part of the AC currents having a plurality of types of frequencies during the first period of the driving current I as the discharge lamp 90 deteriorates. You may control. In other words, the control unit 40 causes the discharge lamp drive 230 so that the average frequency (for example, the frequency per one period of the drive current I) during the first period increases as the drive current I as the discharge lamp 90 deteriorates. To control.

  This shortens the time during which currents of the same polarity flow in the first period. Therefore, the time during which the low temperature state continues in the first period is shortened. Therefore, deformation of the electrode can be suppressed.

  Further, according to the projector 500 according to the present embodiment, the control unit 40 drives the discharge lamp so that the absolute value of the drive current I is relatively small in the first period and relatively large in the second period. Since the unit 230 is controlled, a projector capable of projecting an image so as to appear bright can be realized.

  In the examples shown in FIGS. 10A to 10D, the absolute value of the drive current I in the first period and the absolute value of the drive current I in the second period are constant within each period, but are not limited thereto. Absent. For example, when the absolute value of the drive current I in the first period and the absolute value of the drive current I in the second period change in each period, the control unit 40 determines the drive current I in each period. The discharge lamp driving unit 230 may be controlled such that the average absolute value is relatively small in the first period and relatively large in the second period. Further, for example, when the absolute value of the drive current I in the first period and the absolute value of the drive current I in the second period change within the respective periods, the control unit 40 determines the drive current I in the first period. The discharge lamp driving unit 230 may be controlled to take the minimum absolute value and take the maximum absolute value of the driving current I in the second period.

  In each of the embodiments described above, the projector 500 is configured to cause the viewer to stereoscopically display the first video and the second video as the left-eye video and the right-eye video, respectively, but is not limited thereto. For example, the projector may adopt a configuration in which the first video and the second video are videos having different contents, and two display videos (first video and second video) are visually recognized by different viewers.

  When configured in this manner, the active shutter glasses are provided with left and right shutters that operate in the same manner as the right shutter 412 described above, and left and right shutters that operate in the same manner as the left shutter 414 described above. Two types of glasses may be provided.

  In each of the above embodiments, a projector using three liquid crystal panels has been described as an example. However, the present invention is not limited to this, and one, two, four or more liquid crystal panels are used. It can also be applied to projectors.

  In each of the above embodiments, a transmissive projector has been described as an example. However, the present invention is not limited to this, and can be applied to a reflective projector. Here, “transmission type” means that an electro-optic modulation device as a light modulation means such as a transmission type liquid crystal panel transmits light, and “reflection type” means This means that an electro-optic modulator as a light modulator such as a reflective liquid crystal panel or a micromirror type light modulator is a type that reflects light. As the micromirror light modulator, for example, DMD (digital micromirror device; trademark of Texas Instruments) can be used. Even when the present invention is applied to a reflective projector, the same effect as that of a transmissive projector can be obtained.

  The present invention can be applied to a front projection type projector that projects from the side that observes the projected image, or to a rear projection type projector that projects from the side opposite to the side that observes the projected image. is there.

  In addition, this invention is not limited to the above-mentioned embodiment, A various deformation | transformation implementation is possible within the range of the summary of this invention.

  The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

  DESCRIPTION OF SYMBOLS 10 Discharge lamp lighting device, 20 Power control circuit, 21 Switch element, 22 Diode, 23 Coil, 24 Capacitor, 30 Polarity inversion circuit, 31 1st switch element, 32 2nd switch element, 33 3rd switch element, 34 Fourth switch element, 40 control unit, 41 system controller, 42 power control circuit controller, 43 polarity inversion circuit controller, 44 storage unit, 50 sub-reflecting mirror, 60 voltage detection unit, 61 first resistor, 62 second Resistance, 63 third resistance, 70 igniter circuit, 80 DC power supply, 90 discharge lamp, 90e1 first end, 90e2 second end, 91 discharge space, 92 first electrode, 93 second electrode, 112 main Reflector, 114 fixing member, 200 light source device, 210 light source unit, 230 discharge lamp Moving part, 305 Parallelizing lens, 310 Illumination optical system, 320 Color separation optical system, 330R, 330G, 330B Liquid crystal light valve, 340 Cross dichroic prism, 350 Projection optical system, 400 Projector system, 410 Active shutter glasses, 412 Right shutter 414 Left shutter, 500 Projector, 502 Image signal, 510 Image signal converter 512R, 512G, 512B Image signal 514 Synchronization signal 522 Fixing member 534 Conductive member 536 First terminal 544 Conductive member 546 Second terminal, 552p protrusion, 560R, 560G, 560B liquid crystal panel, 562p protrusion, 570 image processing device, 572R, 572G, 572B drive signal, 582 communication signal, 584 communication signal, 600 AC power supply, 700 screens.

Claims (6)

A projector that switches between a first video and a second video at a given switching timing and alternately outputs them,
A discharge lamp,
A discharge lamp driving unit that supplies a driving current for driving the discharge lamp to the discharge lamp;
A state detector for detecting a deterioration state of the discharge lamp;
A control unit for controlling the discharge lamp driving unit,
The period between the switching timings adjacent in time starts with the first period and ends with the second period,
The control unit controls the discharge lamp driving unit so that the absolute value of the driving current is relatively small in the first period and relatively large in the second period;
In the first period, the control unit
Controlling the discharge lamp drive unit to supply an alternating current to the discharge lamp as the drive current; and
A projector that controls the discharge lamp driving unit such that at least a part of the frequency of the driving current increases as the deterioration state progresses. The projector according to claim 1 .
The control unit is a projector that controls the discharge lamp driving unit so that an average value of driving power throughout the first period and the second period is constant. In a given switching timing, a projector and, including projector systems and shutter glasses, a having a first shutter and a second shutter for alternately outputted by switching the right eye image and left-eye video,
The projector is
A discharge lamp,
A discharge lamp driving unit that supplies a driving current for driving the discharge lamp to the discharge lamp;
A state detector for detecting a deterioration state of the discharge lamp;
A control unit for controlling the discharge lamp driving unit;
With
The period between the switching timings adjacent in time includes a first period and a second period adjacent in time after the first period,
The control unit controls the discharge lamp driving unit so that an absolute value of the driving current in the second period is larger than an absolute value of the driving current in the first period;
In the first period, the control unit
Controlling the discharge lamp drive unit to supply an alternating current to the discharge lamp as the drive current; and
As the deterioration state progresses, the discharge lamp driving unit is controlled so that the frequency of at least a part of the driving current is increased,
The first shutter and the second shutter are switched between an open state and a closed state based on a signal from the control unit,
In the first period, the first shutter and the second shutter are in the closed state,
In the second period, one of the first shutter and the second shutter is in the open state, and the other is in the closed state. The projector system according to claim 3,
In the second period, the control unit
Controlling the discharge lamp drive unit to supply an alternating current to the discharge lamp as the drive current; and
The projector system which controls the said discharge lamp drive part so that the frequency of at least one part of the said drive current may become low with the progress of the said deterioration state. A projector system including a projector that switches between a right-eye image and a left-eye image at a given switching timing and alternately outputs the shutter glasses having a first shutter and a second shutter,
The projector is
A discharge lamp,
A discharge lamp driving unit that supplies a driving current for driving the discharge lamp to the discharge lamp;
A state detector for detecting a deterioration state of the discharge lamp;
A control unit for controlling the discharge lamp driving unit;
With
The period between the switching timings adjacent in time includes a first period and a second period adjacent in time after the first period,
The control unit controls the discharge lamp driving unit so that an absolute value of the driving current in the second period is larger than an absolute value of the driving current in the first period;
In the second period, the control unit
Controlling the discharge lamp drive unit to supply an alternating current to the discharge lamp as the drive current; and
As the deterioration state progresses, the discharge lamp driving unit is controlled so that the frequency of at least a part of the driving current is lowered,
The first shutter and the second shutter are switched between an open state and a closed state based on a signal from the control unit,
In the first period, the first shutter and the second shutter are in the closed state,
In the second period, one of the first shutter and the second shutter is in the open state, and the other is in the closed state. In the projector system according to any one of claims 3 to 5,
The said control part is a projector system which controls the said discharge lamp drive part so that the average value of the drive electric power through the said 1st period and the said 2nd period may become fixed.

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