JP2018045927A - Discharge lamp driving device, light source device, projector, and method for controlling discharge lamp driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp driving device capable of reducing an amount of overshoot.SOLUTION: In one aspect of a discharge lamp driving device of the present invention, a current adjustment unit comprises a first switch element connected between a power supply device which supplies power to the current adjustment unit and a polarity inversion unit. The polarity inversion unit comprises a second switch element and a third switch element connected between the first switch element and a discharge lamp. A control unit subjects the first switch element to PWM control, and synchronizes the current adjustment unit with the polarity inversion unit so that the first switch element enters an OFF state in first timing and second timing. In the first timing, when one switch element of the second switch element and the third switch element is in the OFF state, the other switch element enters the OFF state from an ON state. In the second timing, when one switch element is in the OFF state, other switch element enters the ON state from the OFF state.SELECTED DRAWING: Figure 6

Description

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

  There is known a discharge lamp lighting device having a DC-DC conversion circuit including a switching element and a polarity inversion circuit including a plurality of switching elements and converting a DC voltage output from the DC-DC conversion circuit into an AC voltage. (For example, refer to Patent Document 1).

JP 2006-120654 A

  In the discharge lamp lighting device (discharge lamp driving device) as described above, when the switching elements (second switch element and third switch element) are switched between ON / OFF states in the polarity inversion circuit (polarity inversion unit), the discharge lamp Overshoot occurs in the drive current supplied to. As a result, there is a problem in that the driving current is excessively supplied to the discharge lamp and the life of the discharge lamp is likely to be reduced. In addition, there is a problem that the driving power supplied to the discharge lamp temporarily increases due to overshoot, and the discharge lamp flickers.

  One aspect of the present invention is made in view of the above problems, and is a discharge lamp driving device capable of reducing the amount of overshoot, a light source device including such a discharge lamp driving device, and such An object is to provide a projector including a light source device. Another object of one embodiment of the present invention is to provide a control method for a discharge lamp driving device that can reduce the amount of overshoot.

  One aspect of the discharge lamp driving device of the present invention includes a discharge lamp driving unit that supplies a driving current to the discharge lamp, and a control unit that controls the discharge lamp driving unit, and the discharge lamp driving unit includes: A current adjustment unit that adjusts a current value of the drive current supplied to the discharge lamp; and a polarity inversion unit that reverses the polarity of the drive current input from the current adjustment unit at a predetermined timing. And a first switching element connected between the power supply device that supplies power to the current adjusting unit and the polarity reversing unit, and one end connected between the first switch element and the polarity reversing unit. The polarity reversing unit includes a second switch element and a third switch element connected between the first switch element and the discharge lamp, and the second switch element is turned on. And the third switch The discharge lamp is supplied with the drive current having the first polarity when the child is in the OFF state, the discharge is performed when the second switch element is in the OFF state and the third switch element is in the ON state. The drive current of the second polarity is supplied to the electric lamp, the control unit performs PWM control of the first switch element, and the control unit switches one of the second switch element and the third switch element. A first timing at which the other switch element changes from the ON state to the OFF state when the element is in the OFF state; and a second timing at which the other switch element changes from the OFF state to the ON state when the one switch element is in the OFF state. In the timing, the current adjustment unit and the polarity inversion unit are synchronized so that the first switch element is in an OFF state.

  According to one aspect of the discharge lamp driving device of the present invention, the pulse of the first switch element is not provided across the first timing and the second timing, and both the second switch element and the third switch element are provided. It is easy to suppress an increase in the total length of the period in which the first switch element is in the ON state during the switching period in which is in the OFF state. Thereby, it is easy to reduce the amount of voltage increase applied to the capacitor during the switching period. Therefore, according to one aspect of the discharge lamp driving device of the present invention, the amount of overshoot can be reduced. Thereby, it can suppress that an excessively large drive current is supplied to a discharge lamp, and can improve the lifetime of a discharge lamp. Moreover, it can suppress that a discharge lamp flickers.

In the switching period in which both the second switch element and the third switch element are in the OFF state, the control unit sets the duty ratio during the period in which the first switch element is in the ON state to the second switch element and It is good also as a structure made smaller than the said duty ratio in the period when one of the said 3rd switch elements becomes an ON state.
According to this configuration, the total length of the period in which the first switch element is in the ON state in the switching period can be reduced. Thereby, the amount of voltage increase applied to the capacitor during the switching period can be reduced, and the amount of overshoot can be reduced.

The controller adjusts a duty ratio during a period in which the first switch element is in an ON state, so that the first switch element is in an OFF state at the first timing and the second timing. It is good also as a structure which controls a switch element.
According to this configuration, the first switch element can be easily turned off at the first timing and the second timing while performing PWM control of the first switch element.

A voltage detection unit configured to detect a voltage between the electrodes of the discharge lamp; and the control unit includes the first switch element in a switching period in which both the second switch element and the third switch element are in an OFF state. It is good also as a structure which changes the duty ratio of the period used as an ON state according to the detected said voltage between electrodes.
According to this configuration, it is possible to more suitably reduce the overshoot amount.

The said control part is good also as a structure which makes the said duty ratio in the said switching period small, so that the detected said voltage between electrodes is large.
According to this configuration, it is possible to more suitably reduce the overshoot amount.

The control unit determines a duty ratio of a period in which the first switch element is in an ON state during a switching period in which both the second switch element and the third switch element are in an OFF state according to the frequency of the drive current. It is good also as a structure to change.
According to this structure, it can suppress that average drive electric power falls, and can suppress that the brightness of a discharge lamp changes.

The control unit sets the duty ratio in the switching period when the frequency of the driving current is a first frequency, and the duty ratio in the switching period when the frequency is a second frequency lower than the first frequency. It may be configured to be larger than the duty ratio.
According to this structure, it can suppress that average drive electric power falls, and can suppress that the brightness of a discharge lamp changes.

  One aspect of the light source device of the present invention includes a discharge lamp that emits light and the discharge lamp driving device.

  According to one aspect of the light source device of the present invention, since the discharge lamp driving device is provided, the amount of overshoot can be reduced.

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

  According to one aspect of the projector of the present invention, since the light source device is provided, the amount of overshoot can be reduced.

A second control unit configured to output a command to the control unit of the discharge lamp driving device via an electric signal, wherein both the second switch element and the third switch element are in an OFF state; The command output from the second control unit may not be executed from a predetermined time before the switching period starts until at least the switching period ends.
According to this configuration, it is possible to suppress the execution of the instruction from the second control unit from overlapping with the timing at which the first switch element is turned off immediately before the first timing and immediately before the second timing. Thereby, it can suppress that the timing which makes a 1st switch element OFF state delays, and can make a 1st switch element OFF state more reliably in a 1st timing and a 2nd timing.

  One aspect of the control method of the discharge lamp driving device of the present invention includes a discharge lamp driving unit that supplies a driving current to the discharge lamp, and the discharge lamp driving unit includes a current of the driving current that is supplied to the discharge lamp. A current adjusting unit that adjusts the value; and a polarity reversing unit that reverses the polarity of the drive current from the current adjusting unit at a predetermined timing, and the current adjusting unit supplies power to the current adjusting unit. A first switch element connected between the device and the polarity reversing unit; and a capacitor having one end connected between the first switch element and the polarity reversing unit. , A control method for a discharge lamp driving device having a second switch element and a third switch element connected between the first switch element and the discharge lamp, wherein the first switch element is PWM-controlled, Second switch element and A first timing at which one of the third switch elements is OFF when the other switch element is OFF; and the other switch element is OFF when the one switch element is OFF. The current adjusting unit and the polarity inverting unit are synchronized so that the first switch element is in the OFF state at the second timing when the OFF state is turned on.

  According to one aspect of the control method of the discharge lamp driving device of the present invention, the amount of overshoot can be reduced in the same manner as described above.

It is a schematic block diagram of the projector of this embodiment. It is a figure which shows the discharge lamp in this embodiment. It is a block diagram which shows the various components of the projector of this embodiment. It is a circuit diagram of the discharge lamp lighting device of this embodiment. It is a figure which shows an example of the drive current supplied to a discharge lamp in this embodiment, and the relationship between the ON / OFF state of the 2nd switch element in this embodiment, and the ON / OFF state of a 3rd switch element. It is a figure for demonstrating the switching timing of the 2nd switch element in this embodiment, a 3rd switch element, and a 1st switch element. It is a figure which shows an example of the drive current of this embodiment.

Hereinafter, a projector according to an embodiment of the invention will be described with reference to the drawings.
The scope of the present invention is not limited to the following embodiment, 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 easy to understand, the actual structure may be different from the scale, number, or the like in each structure.

  As shown in FIG. 1, the projector 500 of the present embodiment includes 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 (light modulation devices) 330R. , 330G, 330B, 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 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 according to the video signal 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 three modulated 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). As a result, an image is displayed on the screen 700. As each configuration 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 well-known configuration can be adopted.

  FIG. 2 is a cross-sectional view 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 (discharge lamp driving device) 10. FIG. 2 shows a cross-sectional view of the light source unit 210. The light source unit 210 includes a main reflecting mirror 112, a discharge lamp 90, and a sub reflecting mirror 113.

  The discharge lamp lighting device 10 supplies the drive current I 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 of the discharge lamp 90.

  The shape of the discharge lamp 90 is a rod shape extending along the irradiation direction D. One end of the discharge lamp 90 is a first end 90e1, and the other end of the discharge lamp 90 is a second end 90e2. The material of the discharge lamp 90 is a translucent material such as quartz glass, for example. The central portion of the discharge lamp 90 swells in a spherical shape, and the inside is a discharge space 91. The discharge space 91 is filled with a gas that is a discharge medium containing a rare gas, a metal halide, or the like.

  In the discharge space 91, the tips of the first electrode 92 and the second electrode 93 protrude. The first electrode 92 is disposed on the first end portion 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 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 of the first electrode 92 and the second electrode 93 are arranged to face each other with a predetermined distance. 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 penetrates the inside of the discharge lamp 90. Similarly, a second terminal 546 is provided at the second end 90e2 of the discharge lamp 90. The second terminal 546 and the second electrode 93 are electrically connected by a conductive member 544 that penetrates 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 a driving current I 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 90e1 of the discharge lamp 90 by a fixing member 114. The main reflecting mirror 112 reflects the light traveling toward the opposite side of the irradiation direction D in the discharge light toward the irradiation direction D. The shape of the reflecting surface (the surface on the discharge lamp 90 side) of the main reflecting mirror 112 is not particularly limited as long as the discharge light can be reflected in the irradiation direction D. Parabolic shape may be sufficient. For example, when the shape of the reflecting surface of the main reflecting mirror 112 is a parabolic shape, 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-reflecting mirror 113 is fixed to the second end 90 e 2 side of the discharge lamp 90 by a fixing member 522. The shape of the reflecting surface (surface on the discharge lamp 90 side) of the sub-reflecting mirror 113 is a spherical shape surrounding the portion of the discharge space 91 on the second end 90e2 side. The sub-reflecting mirror 113 reflects the light traveling toward the side opposite to the side on which the main reflecting mirror 112 is disposed in 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.

  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 generated 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 113 and the discharge lamp 90 is not limited to the method of fixing the main reflecting mirror 112 and the sub reflecting mirror 113 to the discharge lamp 90, and any method can be adopted. . For example, the discharge lamp 90 and the main reflecting mirror 112 may be independently fixed to the housing (not shown) of the projector 500. The same applies to the sub-reflecting mirror 113.

Hereinafter, the circuit configuration of the projector 500 will be described.
FIG. 3 is a diagram illustrating an example of a circuit configuration of the projector 500 according to the present embodiment. In addition to the optical system shown in FIG. 1, 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. It is equipped with.

  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 having a predetermined word length to generate image signals 512R, 512G, and 512B. This is supplied to the image processing device 570.

  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, and 572B for driving the liquid crystal panels 560R, 560G, and 560B to the liquid crystal panels 560R, 560G, and 560B, respectively.

  The DC power supply device 80 converts an AC voltage supplied from an 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 a 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 the time of startup, and causes a 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.

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

  The CPU (second control unit) 580 controls various operations from the start of lighting of the projector 500 to the extinction thereof. For example, in FIG. 3, the CPU 580 outputs a command (for example, a lighting command or a turn-off command) to the control unit 40 (see FIG. 4) described later of the discharge lamp lighting device 10 via a communication signal (electrical signal) 582. The CPU 580 receives lighting information of the discharge lamp 90 from the control unit 40 of 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 illustrating an example of a circuit configuration of the discharge lamp lighting device 10.
As shown in FIG. 4, the discharge lamp lighting device 10 includes a power control circuit (current adjustment unit) 20, a polarity inversion circuit (polarity inversion unit) 30, a control unit 40, an operation detection unit 60, and an igniter circuit 70. And.

  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 by a down chopper circuit that receives the voltage from the DC power supply device (power supply device) 80 as an input, steps down the input voltage, and outputs a DC current Id. The DC power supply device 80 is a power supply device that supplies power to the power control circuit 20.

  The power control circuit 20 includes a first switch element SW1, a diode 22, a coil 23, and a capacitor 24. The first switch element SW1 is constituted by, for example, a transistor. In the present embodiment, one end of the first switch element SW1 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 first switch element SW <b> 1 is connected between the DC power supply device 80 and the polarity inversion circuit 30.

  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 device 80. One end of the capacitor 24 is connected between the first switch element SW <b> 1 and the polarity inversion circuit 30. The capacitor 24 is connected in parallel with the discharge lamp 90. A current control signal is input to the control terminal of the first switch element SW1 from the control unit 40 described later, and the ON / OFF operation of the first switch element SW1 is controlled. A PWM (Pulse Width Modulation) control signal is used as a current control signal for controlling the first switch element SW1. That is, the first switch element SW1 is PWM-controlled by the control unit 40 described later.

  When the first switch element SW <b> 1 is turned on, a current flows through the coil 23 and energy is stored in the coil 23. Thereafter, when the first switch element SW1 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 first switch element SW1 is turned on is generated. The power control circuit 20 adjusts the current value of the drive current I supplied to the discharge lamp 90 by the PWM control of the first switch element SW1 in this way. The direct current Id output from the power control circuit 20 is input to the polarity inversion circuit 30 via the operation detection unit 60.

  The polarity inversion 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 inversion circuit 30 generates and outputs a drive current I that is a direct current that lasts for a controlled time, or a drive current I that 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 second switch element SW2 and a third switch element SW3 configured by transistors. The second switch element SW2 and the third switch element SW3 are connected between the first switch element SW1 and the discharge lamp 90. In the present embodiment, the second switch element SW2 is composed of two switch elements, a second switch element SW2a and a second switch element SW2b. In the present embodiment, the third switch element SW3 is composed of two switch elements, a third switch element SW3a and a third switch element SW3b. The polarity inverting circuit 30 has a configuration in which a second switch element SW2a and a third switch element SW3a connected in series and a second switch element SW2b and a third switch element SW3b connected in series are connected in parallel to each other. The second switch element SW2a and the third switch element SW3a connected in series and the second switch element SW2b and the third switch element SW3b connected in series are connected in parallel with the discharge lamp 90.

  The polarity inversion control signal is input from the control unit 40 to the control terminals of the second switch elements SW2a and SW2b and the third switch elements SW3a and SW3b. Based on this polarity inversion control signal, the ON / OFF operations of the second switch elements SW2a, SW2b and the third switch elements SW3a, SW3b are controlled.

  In the polarity inverting circuit 30, the operation of alternately turning on / off the second switch elements SW2a, SW2b and the third switch elements SW3a, SW3b 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 in the same polarity state for a controlled time from the common connection point of the second switch element SW2a and the third switch element SW3a and the common connection point of the second switch element SW2b and the third switch element SW3b. Is generated and output, or a drive current I that is an alternating current having a controlled frequency is output.

  The polarity inversion circuit 30 has the third switch elements SW3a and SW3b in the OFF state when the second switch elements SW2a and SW2b are in the ON state, and the third switch elements SW3a and SW3b when the second switch elements SW2a and SW2b are in the OFF state. Is controlled to be in the ON state. Therefore, when the second switch elements SW2a and SW2b are in the ON state, a drive current I that flows from the one end of the capacitor 24 in the order of the second switch element SW2a, the discharge lamp 90, and the second switch element SW2b is generated. When the third switch elements SW3a and SW3b are in the ON state, a drive current I that flows from one end of the capacitor 24 in the order of the third switch element SW3b, the discharge lamp 90, and the third switch element SW3a is generated.

  What is the polarity of the drive current I that flows through the discharge lamp 90 when the second switch elements SW2a and SW2b are in the ON state and the polarity of the drive current I that flows through the discharge lamp 90 when the third switch elements SW3a and SW3b are in the ON state? , Different from each other. In the present embodiment, the polarity of the drive current I flowing through the discharge lamp 90 when the second switch elements SW2a and SW2b are in the ON state is the first polarity, and the discharge lamp is when the third switch elements SW3a and SW3b are in the ON state. The polarity of the drive current I flowing through 90 is the second polarity.

  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 driving current I for driving the discharge lamp 90 to 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, so that the holding time during which the drive current I continues the same polarity, the current value of the drive current I, and the power of the drive power Wd Control parameters such as value and frequency. The control unit 40 performs polarity reversal control for the polarity reversing circuit 30 to control the holding time during which the drive current I continues at the same polarity, the frequency of the drive current I, and the like according to the polarity reversal timing of the drive current I. The control unit 40 performs current control for controlling the current value of the output direct current Id on the power control circuit 20.

  In the present embodiment, the control unit 40 includes a system controller 41 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 by controlling the ON / OFF state of the first switch element SW1. The system controller 41 controls the polarity inversion circuit 30 by controlling the ON / OFF state of the second switch element SW2 and the ON / OFF state of the third switch element SW3 via the polarity inversion circuit controller 43. The system controller 41 inputs a control signal to the polarity inversion circuit controller 43. The polarity inversion circuit controller 43 switches the ON / OFF state of the second switch element SW2 and the ON / OFF state of the third switch element SW3 based on the input control signal. The system controller 41 may control the ON / OFF state of each switch element based on the lamp voltage Vla and the drive current I detected by the operation detection unit 60.

  The system controller 41 (control unit 40) always keeps track of the ON / OFF state of the first switch element SW1, the ON / OFF state of the second switch element SW2, and the ON / OFF state of the third switch element SW3. Switching of the ON / OFF state of the element is performed according to the ON / OFF state of each switch element. As a result, the system controller 41 (control unit 40) synchronizes the power control circuit 20 and the polarity inversion circuit 30.

In the present embodiment, a storage unit 44 is connected to 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, for example, information related to 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.
A communication signal 582 from the CPU 580 is input to the system controller 41. The system controller 41 outputs a communication signal 584 to the CPU 580. As a result, the control unit 40 executes the command output from the CPU 580 via the communication signals 582 and 584.

  In the present embodiment, the operation detection unit 60 includes a voltage detection unit that detects the lamp voltage Vla of the discharge lamp 90 and outputs lamp voltage information to the control unit 40. Further, 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 in parallel with the discharge lamp 90 using the voltage divided by the first resistor 61 and the second resistor 62 connected in series with each other. . 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. Information on the lamp voltage Vla and the drive current I detected by the operation detector 60 is input to the system controller 41.

  The igniter circuit 70 operates only when the discharge lamp 90 starts to be lit. The igniter circuit 70 is a high voltage (discharge) necessary for forming 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. (A 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.

Next, control of the discharge lamp driving unit 230 by the control unit 40 will be described.
FIG. 5 is a diagram showing a relationship between an example of the drive current I supplied to the discharge lamp 90 in the present embodiment and the ON / OFF state of the second switch element SW2 and the ON / OFF state of the third switch element SW3. is there. In the upper diagram in FIG. 5, the vertical axis indicates the drive current I, and the horizontal axis indicates time T. The drive current I is shown as positive when it is in the first polarity state and negative when it is in the second polarity state. The middle diagram of FIG. 5 is a diagram showing the ON / OFF state of the second switch element SW2, and the horizontal axis shows time T. The lower diagram of FIG. 5 is a diagram illustrating the ON / OFF state of the third switch element SW3, and the horizontal axis represents the time T.

  As described above, in the present embodiment, when the second switch element SW2 is in the ON state and the third switch element SW3 is in the OFF state, the driving current I having the first polarity is supplied to the discharge lamp 90. The On the other hand, when the second switch element SW2 is in the OFF state and the third switch element SW3 is in the ON state, the driving current I having the second polarity is supplied to the discharge lamp 90. In the middle diagram of FIG. 5, the second switch element SW2 is switched between ON / OFF states at a constant cycle. In the lower diagram of FIG. 5, the third switch element SW3 is switched between ON / OFF states at a constant cycle. The frequency at which the second switch element SW2 is switched is the same as the frequency at which the third switch element SW3 is switched.

  By switching the second switch element SW2 and the third switch element SW3 as described above, as shown in the upper diagram of FIG. 5, the first polarity period in which the drive current I having the first polarity is supplied to the discharge lamp 90. A driving current I having alternately P1 and a second polarity period P2 in which the second polarity driving current I is supplied to the discharge lamp 90 is supplied to the discharge lamp 90. The drive current I shown in the upper diagram of FIG. 5 is, for example, a rectangular wave alternating current whose polarity is inverted between the current value Im1 and the current value −Im1. The frequency of the drive current I is the same as the frequency at which the second switch element SW2 is switched and the frequency at which the third switch element SW3 is switched. The frequency of the drive current I is, for example, about several hundred Hz. For example, the length of the first polarity period P1 and the length of the second polarity period P2 are the same.

  FIG. 6 is a diagram for explaining the switching timing of the second switch element SW2, the third switch element SW3, and the first switch element SW1. The upper part of FIG. 6 is a partially enlarged view showing the ON / OFF state of the second switch element SW2, and the horizontal axis shows time T. The middle diagram of FIG. 6 is a partially enlarged view showing the ON / OFF state of the third switch element SW3, and the horizontal axis shows time T. The lower diagram of FIG. 6 is a diagram illustrating the ON / OFF state of the first switch element SW1, and the horizontal axis represents time T.

  As shown in FIG. 6, a switching period Pc is provided between each of the first polarity period P1 and the second polarity period P2. The switching period Pc is a period during which both the second switch element SW2 and the third switch element SW3 are in the OFF state. The length tc of the switching period Pc is smaller than the length of the first polarity period P1 and the length of the second polarity period P2. The length tc of the switching period Pc is, for example, about 0.2 ms (milliseconds) to 3.0 ms (milliseconds). In FIG. 5, the switching period Pc is not shown.

In the present embodiment, the control unit 40 performs PWM control on the first switch element SW1. The PWM frequency for switching the ON / OFF state of the first switch element SW1 is, for example, several tens of kHz. In the first polarity period P1, the second polarity period P2, and the switching period Pc, the control unit 40 determines the length of the period in which the first switch element SW1 is in the ON state, that is, the pulse length in PWM control (hereinafter referred to as pulse (Referred to as width tw). That is, the control unit 40 changes the duty ratio DR of the pulse (period) in which the first switch element SW1 is in the ON state between the first polarity period P1, the second polarity period P2, and the switching period Pc. The duty ratio DR of the pulse at which the first switch element SW1 is turned on is the ratio of the pulse width tw to the PWM cycle tp for switching the ON / OFF state of the first switch element SW1. The PWM cycle tp is, for example, 20 μs (microseconds).
In the following description, a pulse that turns on the first switch element SW1 may be simply referred to as a pulse of the first switch element SW1.

  As shown in the lower diagram of FIG. 6, the duty ratio DR is set to the first predetermined value d1 in the first polarity period P1 and the second polarity period P2. In the switching period Pc, the duty ratio DR is set to the second predetermined value d2. The second predetermined value d2 is smaller than the first predetermined value d1. That is, in the present embodiment, the control unit 40 determines the duty ratio DR of the pulse in which the first switch element SW1 is in the ON state during the switching period Pc in which both the second switch element SW2 and the third switch element SW3 are in the OFF state. Is made smaller than the duty ratio DR in the period (first polarity period P1, second polarity period P2) in which one of the second switch element SW2 and the third switch element SW3 is in the ON state.

  The duty ratio DR in the first polarity period P1 and the second polarity period P2, that is, the first predetermined value d1, is, for example, 50%. The duty ratio DR in the switching period Pc, that is, the second predetermined value d2 is, for example, 5%. The pulse width tw in the first polarity period P1 and the second polarity period P2 is, for example, 10 μs (microseconds). The pulse width tw in the switching period Pc is, for example, 1 μs (microseconds).

  In the present embodiment, the total length of the period in which the first switch element SW1 is in the ON state in the switching period Pc is constant. The total length of the period in which the first switch element SW1 is in the ON state in the switching period Pc is the sum of the pulse widths tw of the pulses of the first switch element SW1 included in the switching period Pc. When the duty ratio DR is constant in each switching period Pc, the number of pulses of the first switch element SW1 included in one switching period Pc is constant. In the example of FIG. 6, the number of pulses of the first switch element SW1 included in one switching period Pc is three.

  In the present embodiment, the control unit 40 changes the duty ratio DR in the switching period Pc according to the detected lamp voltage Vla. Specifically, the control unit 40 decreases the duty ratio DR in the switching period Pc as the detected lamp voltage Vla increases.

  In the present embodiment, the control unit 40 includes a first timing T1 at which one of the second switch element SW2 and the third switch element SW3 is turned off when the other switch element is turned off, and The power control circuit 20 and the polarity inversion circuit 30 are set so that the first switch element SW1 is in the OFF state at the second timing T2 when the other switch element is turned from the OFF state to the ON state when one switch element is in the OFF state. Synchronize with. That is, the first timing T1 is the timing at which the second switch element SW2 changes from the ON state to the OFF state when the third switch element SW3 is in the OFF state, and the third switch element SW2 when the second switch element SW2 is in the OFF state. And the timing at which SW3 changes from the ON state to the OFF state. The second timing T2 is the timing at which the third switch element SW3 changes from the OFF state to the ON state when the second switch element SW2 is OFF, and the second switch element SW3 when the third switch element SW3 is OFF. And the timing at which SW2 changes from the OFF state to the ON state. In other words, the first timing T1 is a timing at which the first polarity period P1 or the second polarity period P2 shifts to the switching period Pc, and the second timing T2 is the first polarity period P1 or the second polarity period P2 from the switching period Pc. This is the timing for shifting to the polarity period P2. A first timing T1 shown in FIG. 6 is a timing at which the second switch element SW2 changes from the ON state to the OFF state when the third switch element SW3 is in the OFF state. The second timing T2 shown in FIG. 6 is a timing at which the third switch element SW3 changes from the OFF state to the ON state when the second switch element SW2 is in the OFF state.

  In the present embodiment, the control unit 40 adjusts the duty ratio DR of the pulse (period) during which the first switch element SW1 is turned on, so that the first switch element SW1 is turned off at the first timing T1 and the second timing T2. The first switch element SW1 is controlled so as to be in the state. Specifically, the control unit 40 sets the ON / OFF state of the first switch element SW1 at the currently set duty ratio DR (first predetermined value d1) at a predetermined timing T0 that is a predetermined time before the first timing T1. When switching is performed, it is calculated whether the first switch element SW1 is turned on or turned off at the first timing T1.

  When it is calculated that the first switch element SW1 is turned on at the first timing T1, the control unit 40 reduces the duty ratio DR of the first switch element SW1 immediately before the first timing T1 and It is determined that the first switch element SW1 is turned off at one timing T1. In the lower diagram of FIG. 6, the control unit 40 sets the duty ratio DR of the pulse of the first switch element SW1 immediately before the first timing T1 to a third predetermined value d3 smaller than the first predetermined value d1, The first switch element SW1 is turned off before the timing T1. That is, the control unit 40 sets the duty ratio DR of the first switch element SW1 to the third predetermined value d3 before the second switch element SW2 changes from the ON state to the OFF state. Then, after the first timing T1 is passed and the switching period Pc is reached, the duty ratio DR of the first switch element SW1 is set to a second predetermined value d2 that is smaller than the first predetermined value d1. In the lower diagram of FIG. 6, the third predetermined value d3 is larger than the second predetermined value d2. The third predetermined value d3 may be equal to or less than the second predetermined value d2.

  On the other hand, when it is calculated that the first switch element SW1 is turned off at the first timing T1, the control unit 40 does not decrease the currently set duty ratio DR (first predetermined value d1). Transition to the switching period Pc. Then, after the switching period Pc is reached, the duty ratio DR of the first switch element SW1 is set to a second predetermined value d2 that is smaller than the first predetermined value d1.

  Then, the control unit 40 switches the ON / OFF state of the first switch element SW1 at the currently set duty ratio DR (second predetermined value d2) before the time T reaches the second timing T2. Then, it is calculated whether the first switch element SW1 is turned on or turned off at the second timing T2. When it is calculated that the first switch element SW1 is turned off at the second timing T2, the control unit 40 determines the duty ratio DR of the pulse of the first switch element SW1 after the second timing T2 has elapsed. 2 The first predetermined value d1 is set from the predetermined value d2. That is, the control unit 40 sets the duty ratio DR of the first switch element SW1 to the first predetermined value d1 after the third switch element SW3 changes from the OFF state to the ON state.

  On the other hand, when it is calculated that the first switch element SW1 is turned on at the second timing T2, the control unit 40 does not output a pulse that turns the first switch element SW1 on at the second timing T2, After the second timing T2 has elapsed, the duty ratio DR of the pulse of the first switch element SW1 is set from the second predetermined value d2 to the first predetermined value d1.

  In the present embodiment, the control unit 40 does not execute a command from the CPU 580 after the predetermined timing T0 until the second timing T2 is passed. That is, the control unit 40 outputs from the CPU 580 from a predetermined time before the switching period Pc when both the second switch element SW2 and the third switch element SW3 are turned off to at least the end of the switching period Pc. Do not execute the specified instruction. In the non-execution period Pn shown in the lower diagram of FIG. 6, the control unit 40 does not execute an instruction from the CPU 580. The non-execution period Pn is a period from a predetermined timing T0 to a third timing T3 that is a predetermined time after the second timing T2.

  The command from the CPU 580 input to the control unit 40 during the non-execution period Pn is stored in the storage unit 44, for example. The control unit 40 executes the instruction from the CPU 580 stored in the storage unit 44 during the non-execution period Pn after the non-execution period Pn, that is, the third timing T3 in the present embodiment.

FIG. 7 is a diagram illustrating an example of the drive current I of the present embodiment. In FIG. 7, the vertical axis indicates the drive current I, and the horizontal axis indicates time T.
As shown in FIG. 7, an overshoot OS occurs immediately after switching from the second polarity period P2 to the first polarity period P1 and immediately after switching from the first polarity period P1 to the second polarity period P2. The overshoot OS is a phenomenon in which the absolute value of the value of the drive current I becomes larger than the target value. In FIG. 7, the absolute value of the drive current I in the overshoot OS is larger than the absolute value of Im1.

  The overshoot OS occurs due to the first switch element SW1 being turned on in the switching period Pc. In the switching period Pc, since both the second switch element SW2 and the third switch element SW3 are in the OFF state, the voltage applied to the capacitor 24 shown in FIG. 4 increases when the first switch element SW1 is in the ON state. To do. The voltage applied to the capacitor 24 increases as the total length of the period in which the first switch element SW1 is in the ON state in the switching period Pc increases. When the switching period Pc ends and the first polarity period P1 or the second polarity period P2 starts with the voltage applied to the capacitor 24 increased, the voltage applied to the capacitor 24 is applied to the discharge lamp 90. The lamp voltage decreases to the lamp voltage Vla. At this time, the electric charge stored in the capacitor 24 is released, and an amount of drive current corresponding to the decreasing voltage of the capacitor 24 flows to the discharge lamp 90. As a result, an overshoot OS occurs.

  For example, when the first switch element SW1 is in the ON state at the first timing T1 and the second timing T2, the pulse of the first switch element SW1 is provided across the first timing T1 and the second timing T2. Therefore, a part of the pulse that turns on the first switch element SW1 is provided in the switching period Pc. As a result, when the first switch element SW1 is subjected to PWM control, the total length of the period in which the first switch element SW1 is in the ON state tends to increase in the switching period Pc. Therefore, there is a problem that the amount of increase in the voltage applied to the capacitor 24 during the switching period Pc tends to increase, and the overshoot amount OSW of the overshoot OS tends to increase.

  On the other hand, according to the present embodiment, the control unit 40 controls the discharge lamp driving unit 230 so that the first switch element SW1 is turned off at the first timing T1 and the second timing T2. Therefore, the pulse of the first switch element SW1 is not provided across the first timing T1 and the second timing T2, and the total length of the period in which the first switch element SW1 is in the ON state in the switching period Pc is increased. It is easy to suppress that. This makes it easy to reduce the amount of increase in the voltage applied to the capacitor 24 during the switching period Pc. Therefore, according to the present embodiment, the overshoot amount OSW can be reduced. As a result, it is possible to suppress an excessively large driving current I from being supplied to the discharge lamp 90 and to improve the life of the discharge lamp 90. Further, the occurrence of flickering in the discharge lamp 90 can be suppressed.

  Further, for example, when the power control circuit 20 and the polarity inversion circuit 30 are asynchronous, depending on the relationship between the frequency of the drive current I and the ON / OFF state switching cycle (PWM cycle tp) of the first switch element SW1. At the first timing T1 and the second timing T2, whether the first switch element SW1 is turned on or turned off is changed. In other words, when the power control circuit 20 and the polarity inversion circuit 30 are asynchronous, it is difficult to always turn off the first switch element SW1 at the first timing T1 and the second timing T2. Even when the first switch element SW1 is in the ON state at the first timing T1 and the second timing T2, the pulse of the first switch element SW1 straddling the first timing T1 and the second timing T2 and the first timing T1. Depending on the temporal positional relationship with the second timing T2, the total length of the period in which the first switch element SW1 is in the ON state in the switching period Pc may change. Therefore, the amount of increase in the voltage applied to the capacitor 24 in the switching period Pc differs for each switching period Pc depending on the relationship between the frequency of the drive current I and the switching cycle of the ON / OFF state of the first switch element SW1. . Therefore, the overshoot amount OSW varies.

  Here, when the overshoot OS occurs, for example, it may be possible to reduce the overshoot amount OSW by performing a control that instantaneously reduces the drive current I in a period (switching period Pc) in which each polarity period is switched. . However, when the overshoot amount OSW varies, it is necessary to change the amount of the drive current I that is reduced in accordance with the overshoot amount OSW, and the control is likely to be complicated. Further, for example, it may be possible to reduce the drive current I uniformly according to the maximum value of the overshoot amount OSW. In this case, however, the drive current I is reduced more than necessary when the overshoot amount OSW is relatively small. As a result, the life of the discharge lamp 90 may be reduced. Note that the control for instantaneously reducing the drive current I corresponds to, for example, control for reducing the duty ratio DR in the switching period Pc in the present embodiment.

  On the other hand, according to the present embodiment, the first switch element SW1 is turned off at the first timing T1 and the second timing T2 by synchronizing the power control circuit 20 and the polarity inversion circuit 30. Can do. Therefore, the total length of the period in which the first switch element SW1 is turned on in the switching period Pc is easily adjusted by adjusting the number of pulses in which the first switch element SW1 provided in the switching period Pc is turned on. . As a result, the amount of increase in the voltage applied to the capacitor 24 during the switching period Pc can be easily made constant, and variations in the overshoot amount OSW can be suppressed. Therefore, for example, by performing control to reduce the drive current I, when reducing the overshoot amount OSW, it is possible to suppress the drive current I from being reduced more than necessary while keeping the amount of drive current I to be reduced uniform. Thereby, it is possible to suppress a reduction in the life of the discharge lamp 90 while simplifying the control for reducing the overshoot amount OSW. In the present embodiment, the total length of the period in which the first switch element SW1 is in the ON state in the switching period Pc is constant. Therefore, the overshoot amount OSW is constant as shown in FIG.

  For example, when the system controller 41 controls the power control circuit 20 via another controller such as a power control circuit controller, the control of the power control circuit 20 by the system controller 41 and the control of the polarity inversion circuit 30 are performed. It was difficult to synchronize. On the other hand, according to this embodiment, since the system controller 41 directly controls the power control circuit 20, it is easy to synchronize the control of the power control circuit 20 and the control of the polarity inversion circuit 30. Can be. In addition, the configuration of the control unit 40 can be simplified because it is not necessary to provide another controller such as a power control circuit controller.

  When the system controller 41 controls the power control circuit 20 via another controller such as a power control circuit controller, for example, from the start of applying the lamp voltage Vla to the discharge lamp 90 until the discharge lamp 90 is lit. In the meantime, a circuit (for example, an operational amplifier) for controlling the lamp voltage Vla is required separately. On the other hand, according to the present embodiment, since the system controller 41 directly controls the power control circuit 20, the system controller 41 can directly control the lamp voltage Vla before the discharge lamp 90 is turned on. Therefore, it is not necessary to separately provide a circuit for controlling the lamp voltage Vla before the discharge lamp 90 is turned on, and the configuration of the control unit 40 can be further simplified.

  In addition, since the lamp voltage Vla rapidly increases from the start of applying the lamp voltage Vla to the discharge lamp 90 until before the discharge lamp 90 is lit, voltage control by the power control circuit 20 is performed in a relatively short cycle. It is necessary to do this, and the control gain needs to be relatively large. On the other hand, after the discharge lamp 90 is lit, voltage control by the power control circuit 20 may be performed with a relatively long cycle, and the control gain may be relatively small. When the system controller 41 controls the power control circuit 20 via another controller such as a power control circuit controller, it is difficult to instantaneously switch the control gain and cycle of voltage control, and the discharge lamp 90 is lit as described above. In some cases, it was not possible to properly cope with changes in control gain and period before and after.

  On the other hand, according to the present embodiment, since the control gain and cycle in voltage control can be switched by the system controller 41, the control gain and cycle of voltage control are preferably switched before and after the discharge lamp 90 is turned on. Is easy.

  Further, according to the present embodiment, the control unit 40 decreases the duty ratio DR of the pulse of the first switch element SW1 during the switching period Pc. Therefore, the total length of the period in which the first switch element SW1 is in the ON state in the switching period Pc can be reduced. Thereby, the increase amount of the voltage applied to the capacitor 24 in the switching period Pc can be reduced, and the overshoot amount OSW can be reduced.

  Here, it is preferable to increase the duty ratio DR to a predetermined value or more while keeping it relatively small. If the first switch element SW1 is always in the OFF state during the switching period Pc, or the total length of the period in which the first switch element SW1 is in the ON state is extremely small, the overshoot amount OSW can be greatly reduced while the power control is performed. This is because the voltage in the circuit 20 may decrease too much.

  When the driving power Wd is constant, the value of the driving current I changes when the lamp voltage Vla changes, so that the ratio of the overshoot OS in the driving current I changes. Therefore, as in the present embodiment, the overshoot amount OSW can be more suitably reduced by changing the duty ratio DR of the pulse of the first switch element SW1 in the switching period Pc according to the lamp voltage Vla. Specifically, the overshoot amount OSW can be more suitably reduced by decreasing the duty ratio DR of the pulse of the first switch element SW1 in the switching period Pc as the lamp voltage Vla increases.

  Further, when the frequency at which the second switch element SW2 and the third switch element SW3 are switched, that is, the frequency of the drive current I changes, the drive current I of each frequency is supplied to the discharge lamp 90 within a predetermined period. The number in which the switching period Pc is provided changes. When the number of switching periods Pc for reducing the duty ratio DR of the pulse in which the first switch element SW1 is turned on changes during the predetermined period, the average drive power during the predetermined period changes, and the brightness (luminance) of the discharge lamp 90 changes. ) Will change. Specifically, when the frequency of the drive current I is relatively high, for example, when the frequency of the drive current I is several hundred Hz or more, 1 kHz or less, or greater than 1 kHz, the switching period Pc provided in the predetermined period The number is larger than the number of switching periods Pc provided in the predetermined period when the frequency of the drive current I is relatively low, for example, when the frequency of the drive current I is several tens of Hz. Therefore, the average drive power when the frequency of the drive current I is relatively high is lower than the average drive power when the frequency of the drive current I is relatively low.

  Therefore, when the drive power Wd is constant by changing the duty ratio DR of the pulse of the first switch element SW1 in the switching period Pc according to the frequency of the drive current I as in the present embodiment. It is possible to prevent the average driving power from changing and the brightness of the discharge lamp 90 from changing. Specifically, the control unit 40 increases the duty ratio DR of the pulse in which the first switch element SW1 is in the ON state in the switching period Pc as the frequency of the drive current I is higher. In other words, the control unit 40 sets the duty ratio DR of the pulse of the first switch element SW1 in the switching period Pc when the frequency of the drive current I is the first frequency, and the frequency of the drive current I is lower than the first frequency. The duty ratio DR of the pulse of the first switch element SW1 in the switching period Pc in the case of the second frequency is made larger.

  As a result, when the frequency of the drive current I is relatively high, the total length of the period in which the first switch element SW1 is in the ON state within one switching period Pc is set as compared with the case where the frequency of the drive current I is relatively low. Can also be larger. Therefore, even when the frequency of the drive current I is relatively high and the number of switching periods Pc provided in the predetermined period is increased, the average drive power can be suppressed from decreasing, and the brightness of the discharge lamp 90 can be reduced. Can be suppressed. For example, the control unit 40 sets the duty ratio DR of the pulse of the first switch element SW1 in the switching period Pc when the frequency of the drive current I is 50 Hz to 3%, while the frequency of the drive current I is 500 Hz. The duty ratio DR of the pulse of the first switch element SW1 in a certain switching period Pc is set to 30%.

  In addition, according to the present embodiment, the control unit 40 adjusts the duty ratio DR of the pulse of the first switch element SW1, thereby turning off the first switch element SW1 at the first timing T1 and the second timing T2. To do. Therefore, the first switch element SW1 can be easily turned off at the first timing T1 and the second timing T2 while PWM-controlling the first switch element SW1.

  Further, for example, if the execution of the instruction from the CPU 580 by the control unit 40 overlaps with the timing of turning off the first switch element SW1 immediately before the first timing T1, the timing of turning off the first switch element SW1 is reached. There may be a delay. In this case, the first switch element SW1 may not be turned off at the first timing T1. Similarly, if the execution of the instruction from the CPU 580 overlaps with the timing at which the first switch element SW1 is turned off immediately before the second timing T2, the timing at which the first switch element SW1 is turned off may be delayed. . In that case, the first switch element SW1 may not be turned off at the second timing T2.

  On the other hand, according to the present embodiment, the control unit 40 does not execute a command output from the CPU 580 from a predetermined time before the switching period Pc starts until at least the switching period Pc ends. Therefore, it can be suppressed that the execution of the instruction from the CPU 580 overlaps with the timing at which the first switch element SW1 is turned off immediately before the first timing T1 and immediately before the second timing T2. Thereby, it can suppress that the timing which makes 1st switch element SW1 OFF state delays, and can make 1st switch element SW1 OFF state more reliably in 1st timing T1 and 2nd timing T2.

  Note that the controller 40 does not have to reduce the duty ratio DR during the switching period Pc. In the above description, the duty ratio DR is constant in the switching period Pc. However, the control unit 40 may change the duty ratio DR in the switching period Pc. Further, the control unit 40 may execute a command from the CPU 580 in the switching period Pc.

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

  In the above-described embodiment, the example of the projector 500 using the three liquid crystal panels 560R, 560G, and 560B (liquid crystal light valves 330R, 330G, and 330B) has been described. However, the present invention uses only one liquid crystal panel. The present invention can also be applied to a projector using four or more liquid crystal panels.

  In addition, the configurations described in the above embodiments can be combined with each other within a consistent range.

  DESCRIPTION OF SYMBOLS 10 ... Discharge lamp lighting device (discharge lamp drive device), 20 ... Electric power control circuit (current adjustment part), 24 ... Capacitor, 30 ... Polarity inversion circuit (polarity inversion part), 40 ... Control part, 80 ... DC power supply device ( Power supply device), 90 ... discharge lamp, 200 ... light source device, 230 ... discharge lamp drive unit, 330R, 330G, 330B ... liquid crystal light valve (light modulation device), 350 ... projection optical system, 500 ... projector, 502, 512R, 512G, 512B: Image signal, 580: CPU (second control unit), 582: Communication signal (electric signal), DR: Duty ratio, I: Driving current, Id: DC current (current), Pc: Switching period, SW1 ... 1st switch element, SW2, SW2a, SW2b ... 2nd switch element, SW3, SW3a, SW3b ... 3rd switch element, T1 ... 1st timing, T2 ... 1st Timing

Claims (11)

A discharge lamp driving section for supplying a driving current to the discharge lamp;
A control unit for controlling the discharge lamp driving unit;
With
The discharge lamp drive unit includes: a current adjustment unit that adjusts a current value of the drive current supplied to the discharge lamp; and a polarity inversion unit that reverses the polarity of the drive current input from the current adjustment unit at a predetermined timing. Have
The current adjustment unit includes a first switch element connected between a power supply device that supplies power to the current adjustment unit and the polarity inversion unit, and one end between the first switch element and the polarity inversion unit. A capacitor connected to
The polarity reversing unit includes a second switch element and a third switch element connected between the first switch element and the discharge lamp,
When the second switch element is in the ON state and the third switch element is in the OFF state, the driving current having the first polarity is supplied to the discharge lamp,
When the second switch element is in an OFF state and the third switch element is in an ON state, the driving current having the second polarity is supplied to the discharge lamp,
The control unit performs PWM control on the first switch element,
The control unit includes a first timing at which one of the second switch element and the third switch element is turned off when the other switch element is turned off, and the one switch element. The current adjustment unit and the polarity inversion unit are synchronized so that the first switch element is in the OFF state at the second timing when the other switch element is in the ON state from the OFF state when is in the OFF state. A discharge lamp driving device characterized by that.   In the switching period in which both the second switch element and the third switch element are in the OFF state, the control unit sets the duty ratio during the period in which the first switch element is in the ON state to the second switch element and The discharge lamp driving device according to claim 1, wherein the duty ratio is smaller than the duty ratio in a period in which one of the third switch elements is in an ON state.   The controller adjusts a duty ratio during a period in which the first switch element is in an ON state, so that the first switch element is in an OFF state at the first timing and the second timing. The discharge lamp drive device according to claim 1, wherein the switch element is controlled. A voltage detector for detecting a voltage between the electrodes of the discharge lamp;
The control unit detects a duty ratio of a period during which the first switch element is in an ON state during a switching period in which both the second switch element and the third switch element are in an OFF state. The discharge lamp drive device according to any one of claims 1 to 3, wherein the discharge lamp drive device is changed in accordance with the above.   The discharge lamp driving device according to claim 4, wherein the control unit decreases the duty ratio in the switching period as the detected inter-electrode voltage is increased.   The control unit determines a duty ratio of a period in which the first switch element is in an ON state during a switching period in which both the second switch element and the third switch element are in an OFF state according to the frequency of the drive current. The discharge lamp driving device according to any one of claims 1 to 5, wherein the discharge lamp driving device is changed.   The control unit sets the duty ratio in the switching period when the frequency of the driving current is a first frequency, and the duty ratio in the switching period when the frequency is a second frequency lower than the first frequency. The discharge lamp driving device according to claim 6, wherein the discharge lamp driving device is larger than the duty ratio. A discharge lamp that emits light;
A discharge lamp driving device according to any one of claims 1 to 7,
A light source device comprising: The light source device according to claim 8;
A light modulation device that modulates light emitted from the light source device according to an image signal;
A projection optical system that projects the light modulated by the light modulation device;
A projector comprising: A second control unit that outputs a command to the control unit of the discharge lamp driving device via an electrical signal;
From the second control unit, the control unit starts from a predetermined time before the switching period in which both the second switch element and the third switch element are turned off, and at least until the switching period ends. The projector according to claim 9, wherein the output instruction is not executed. A discharge lamp driving unit for supplying a driving current to the discharge lamp, wherein the discharge lamp driving unit adjusts a current value of the driving current supplied to the discharge lamp; and a drive from the current adjusting unit A polarity inversion unit that inverts the polarity of the current at a predetermined timing, and the current adjustment unit is connected between a power supply device that supplies power to the current adjustment unit and the polarity inversion unit. And a capacitor having one end connected between the first switch element and the polarity inversion unit, and the polarity inversion unit is connected between the first switch element and the discharge lamp. A control method for a discharge lamp driving device having a second switch element and a third switch element,
PWM controlling the first switch element;
The first timing when one of the second switch element and the third switch element is in the OFF state when the other switch element is in the OFF state, and when the one switch element is in the OFF state At the second timing when the other switch element is switched from the OFF state to the ON state, the current adjusting unit and the polarity inverting unit are synchronized so that the first switch element is in the OFF state. Control method of electric light driving device.

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