JP2008159470A - Discharge lamp lighting device and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device capable of suppressing generation of a flicker caused by movement of a bright point immediately after shifting to a constant power control region, and of preventing decrease of the service life of a lamp; and an image display device. <P>SOLUTION: This discharge lamp lighting device has a power conversion circuit including a step-down chopper circuit 1, and a polarity inversion circuit 2 for converting the output of the step-down chopper circuit 1 to a rectangular-wave alternating voltage to apply it to a discharge lamp La. A control circuit 4 controls a lamp current Ila in lighting the lamp to a waveform where first current peak values Ip1 and second current peak values Ip2 larger than the first current peak values Ip1 are alternately generated at predetermined intervals by controlling turning-on/off of switching elements Q1-Q5 of the step-down chopper circuit 1 and the polarity inversion circuit 2. The product of the second current peak value Ip2 of the lamp current after a switchover time t1 and the time width T2 of the second current peak value Ip2 is set smaller than the product of the second current peak value Ip2 of the lamp current before the switchover time t1 and the time width T2 of the second current peak value Ip2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a discharge lamp lighting device and an image display device using the same.

  In recent years, a discharge lamp lighting device for lighting a high-intensity high-pressure discharge lamp of an image display device such as a projector or a rear projection television is required to be free from flicker due to movement of a bright spot of the discharge lamp.

  Therefore, it has been proposed to suppress flicker by supplying a lamp current as shown in FIGS. 13A to 13E to the discharge lamp at the time of lighting. The lamp current in FIG. 13A is raised to a second amplitude Ip2 before the inversion of the rectangular waveform whose polarity is periodically inverted at the first amplitude Ip1, and is set to Ip1 <Ip2. . The lamp current in FIG. 13B gradually increases to the second amplitude Ip2 before the inversion of the rectangular waveform whose polarity is periodically inverted at the first amplitude Ip1, and is set to Ip1 <Ip2. The lamp current in FIG. 13C forms a pulse waveform of the second amplitude Ip2 continuously for one period of the rectangular wave whose polarity is inverted at the first amplitude Ip1, and is set to Ip1 <Ip2. Further, in the rectangular wave having the first amplitude Ip1, the first half cycle Tf is longer than the second half cycle Tr. The lamp current in FIG. 13 (d) forms a pulse waveform of the second amplitude Ip2 continuously for one period of the rectangular wave whose polarity is inverted at the first amplitude Ip1, and is set to Ip1 <Ip2. Further, in the rectangular wave having the first amplitude Ip1, the first half cycle Tf and the second half cycle Tr have the same cycle. The lamp current in FIG. 13 (e) periodically forms a pulse waveform of the second amplitude Ip2 in the DC current of the first amplitude Ip1, and is set to Ip1 <Ip2.

  That is, as shown in FIGS. 13A to 13E, as a lamp current waveform at the time of lighting, a current having an amplitude Ip1 that is a first peak current (hereinafter referred to as a first current peak value Ip1) and Ip1 The peak value of the lamp current temporarily increases by alternately generating a current having a larger second peak current having an amplitude Ip2 (hereinafter referred to as a second current peak value Ip2) at a predetermined interval. Thus, the temperature of the lamp electrode is increased to suppress flicker. This is because the bright spot position is usually stabilized when the protrusion formed on the surface of the electrode becomes the starting point of the arc. However, when multiple protrusions occur on the electrode, the starting point of the arc is not determined and the bright spot position is determined. It tends to cause a moving phenomenon. Therefore, by raising the temperature of the lamp electrode, the rough portion of the electrode is melted so that a plurality of protrusions are not generated on the electrode.

  FIG. 14A shows a first method for setting the first current peak value Ip1 and the second current peak value Ip2, and FIG. 14B shows a second method. FIG. 14C shows the characteristics of the lamp power with respect to the lamp voltage. Like the characteristic X21 (dashed line) in FIGS. 14A and 14B and the characteristic X22 (dashed line) in FIG. When the lamp current is kept constant up to a predetermined lamp voltage Vs and the lamp power is controlled to be constant above the lamp voltage Vs, the first method shown in FIG. 14A is to keep the second current peak value Ip2 constant. The first current peak value Ip1 is changed so that the effective value of the lamp current matches the characteristic X21. In the second method shown in FIG. 14B, the ratio between the first current peak value Ip1 and the second current peak value Ip2 is constant, and the effective value of the lamp current changes so as to match the characteristic X21. I am letting.

Also, when flickering is detected in a constant power control area where constant power is supplied to the discharge lamp and the lamp is steadily lit, switch to a high power mode that supplies more power than the power supplied in the constant power mode. There is also a discharge lamp lighting device in which flicker is suppressed in the same manner as described above by raising the temperature of the lamp electrode (see, for example, Patent Document 1).
JP 2005-38815 A

  In general, as shown in FIGS. 4 (a) and 4 (b), after the start of lighting, until the temperature of the electrode rises to some extent, the lamp current Ila becomes a current limiting region Ta which is controlled so as not to exceed the limiting current I1. Transition from the region Ta to a constant power control region Tb for controlling the lamp power to be constant results in steady lighting. Then, the characteristics X11 and X12 of the conventional lamp voltage Vla and lamp current Ila, as indicated by the broken line in FIG. 4, after the transition to the constant power control region Tb, the lamp power is increased with respect to the increase of the lamp voltage Vla. In order to make it constant, the lamp current Ila is reduced. As a result, the temperature of the electrodes decreases, the distance between the electrodes increases, and the lamp voltage Vla further increases. Then, after a few minutes to several tens of minutes have passed since the transition to the constant power control region Tb and the electrode temperature rises to a predetermined temperature, the lamp voltage Vla gradually decreases, and stable lighting is obtained after time t10.

  However, the above prior art considers flicker suppression during stable lighting several minutes to several tens of minutes after starting lighting, but considers the decrease in electrode temperature immediately after shifting to the constant power control region. Therefore, particularly in a lamp having a high lamp voltage Vla due to factors such as the end of the lamp life, the lamp current Ila immediately after shifting to the constant power control region does not increase, and the temperature shortage of the electrode cannot be resolved. The occurrence of flicker could not be suppressed.

  Even if the lamp is a normal lamp, the lamp voltage Vla immediately after shifting to the constant power control region fluctuates every time the lamp is lit, so the brightness decreases due to the increase in lamp voltage due to electrode wear, and the electrode material The lamp life is shortened due to a decrease in brightness caused by devitrification caused by scattering and adhering to the inside of the lamp tube.

  The present invention has been made in view of the above-described reasons, and an object of the present invention is to provide a discharge lamp that suppresses generation of flicker due to movement of a bright spot immediately after shifting to a constant power control region and prevents shortening of the lamp life. The object is to provide a lighting device and an image display device.

  According to a first aspect of the present invention, there is provided a power conversion circuit that supplies power to the discharge lamp by turning on / off the switching element, and an on / off control of the switching element of the power conversion circuit to thereby control the lamp current The lamp current supplied to the discharge lamp at the time of lighting is changed from the current limiting area where the lamp current is controlled so as not to exceed the limit current to the constant power control area where the lamp power is controlled to be constant. And a control circuit that controls a waveform in which a larger second amplitude is alternately generated at a predetermined interval. When the first time has elapsed from the start of lighting in the constant power control region, the control circuit The product of the second amplitude of the lamp current and the time width of the second amplitude after the first time is smaller than the product of the second amplitude of the lamp current and the time width of the second amplitude before the first time. To be characterized by That.

  According to the present invention, the temperature of the electrode is sufficiently maintained even immediately after shifting to the constant power control region, and the occurrence of flicker can be suppressed. Also, by suppressing flicker, the brightness decreases due to the increase in lamp voltage due to electrode wear, and the brightness decreases due to devitrification due to scattering of electrode material and adhering to the inside of the lamp tube. It is possible to prevent the lamp life from being shortened. That is, it is possible to provide a discharge lamp lighting device that suppresses the occurrence of flicker due to the movement of a bright spot immediately after shifting to the constant power control region and prevents the lamp life from being shortened.

  According to a second aspect of the present invention, in the first aspect, the control circuit makes the second amplitude of the lamp current after the first time smaller than the second amplitude of the lamp current before the first time. Features.

  According to the present invention, it is possible to suppress the occurrence of flicker due to the movement of the bright spot immediately after shifting to the constant power control region, and to prevent the lamp life from being shortened.

  According to a third aspect of the present invention, in the first aspect, the control circuit determines a ratio of the second amplitude to the first amplitude of the lamp current after the first time, and the first of the lamp current before the first time. The ratio is smaller than the ratio of the second amplitude to the second amplitude.

  According to the present invention, it is possible to suppress the occurrence of flicker due to the movement of the bright spot immediately after shifting to the constant power control region, and to prevent the lamp life from being shortened.

  According to a fourth aspect of the present invention, in the first aspect, the control circuit sets a time width of the second amplitude of the lamp current after the first time to a time width of the second amplitude of the lamp current before the first time. It is characterized by being smaller than the width.

  According to the present invention, it is possible to suppress the occurrence of flicker due to the movement of the bright spot immediately after shifting to the constant power control region, and to prevent the lamp life from being shortened.

  According to a fifth aspect of the present invention, in the first aspect, the control circuit sets the ratio of the second amplitude to the first amplitude of the lamp current and the time width of the second amplitude after the first time as the first amplitude. The ratio of the second amplitude to the first amplitude of the lamp current before time and the time width of the second amplitude are made smaller.

  According to the present invention, it is possible to reduce the stress applied to the components of the power conversion circuit, suppress the occurrence of flicker due to the movement of bright spots immediately after shifting to the constant power control region, and prevent the lamp life from being shortened. it can.

  The invention of claim 6 comprises a lamp voltage detection circuit for detecting a lamp voltage according to any one of claims 1 to 5, wherein the control circuit is configured such that when the variation rate of the detected lamp voltage becomes smaller than a predetermined value, The product of the second amplitude of the lamp current after the first time and the time width of the second amplitude is the product of the second amplitude of the lamp current before the first time and the time width of the second amplitude. It is characterized by being made smaller.

  According to the present invention, the first time can be set appropriately.

  According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the control circuit includes a first amplitude and a second amplitude of the lamp current until a second time elapses from the start of lighting in the current limiting region. It is characterized by making the amplitude of the same value.

  According to the present invention, since a sufficient current is supplied to the electrode of the discharge lamp from the start of lighting to the second time, the second amplitude of the lamp current does not have to be larger than the first amplitude. The temperature of the electrode does not become insufficient, the occurrence of flicker can be suppressed, and the lamp current is not increased more than necessary, so that the deterioration of the electrode can be suppressed.

  The invention of claim 8 is characterized in that, in claim 7, the second time is a timing at which the lamp voltage after starting lighting reaches a predetermined voltage.

  According to the present invention, the second time can be set appropriately.

  The invention according to claim 9 is the discharge lamp lighting device according to any one of claims 1 to 8, the discharge lamp that is lit by the discharge lamp lighting device, and the transmitted light that transmits or reflects light from the discharge lamp. Or an optical means for projecting reflected light onto a screen.

  According to the present invention, it is possible to provide an image display device that suppresses the occurrence of flicker due to the movement of a bright spot immediately after shifting to the constant power control region and prevents the lamp life from being shortened, and the image quality is improved. Furthermore, it becomes possible to maintain a superior image quality for a long time.

  As described above, according to the present invention, there is an effect that it is possible to suppress the occurrence of flicker due to the movement of the bright spot immediately after shifting to the constant power control region, and to prevent the lamp life from being shortened.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a circuit configuration of a discharge lamp lighting device according to this embodiment. A step-down chopper circuit 1 using a DC power source E as a power source and a DC voltage output from the step-down chopper circuit 1 are converted into a rectangular wave alternating voltage. A power conversion circuit comprising a polarity inversion circuit 2 applied to the discharge lamp La, a lamp voltage detection circuit 3 for detecting the lamp voltage Vla of the discharge lamp La, and switching elements Q1 to Q5 provided in the power conversion circuit being turned on A control circuit 4 that controls the turn-off is provided.

  In the step-down chopper circuit 1, the positive electrode of the DC power source E is connected to the positive electrode of the capacitor C1 via the switching element Q1 and the inductor L1, and the negative electrode of the capacitor C1 is connected to the negative electrode of the DC power source E1 via the resistor R1 for current detection. Has been. A diode D1 for energizing regenerative current is connected to both ends of the capacitor C1 via an inductor L1.

  The switching element Q1 is turned on / off at a high frequency by the output of the PWM control circuit 43 provided in the control circuit 4. When the switching element Q1 is on, the switching element Q1, the inductor L1, the capacitor C1, the resistance A chopper current flows through R1. The resistor R1 outputs a voltage at both ends proportional to the chopper current as a current detection signal Yi, and the PWM control circuit 43 turns off the switching element Q1 when the chopper current exceeds a predetermined value based on the current detection signal Yi. When the switching element Q1 is off, a regenerative current flows through the inductor L1, the capacitor C1, and the diode D1. By such an operation, the DC voltage obtained by stepping down the output of the DC power supply E is charged in the capacitor C1. Further, the charging voltage of the capacitor C1 can be controlled by making the ON duty of the switching element Q1 variable (the ratio of the ON time in one switching cycle) by the PWM control circuit 43. Note that the DC power supply E1 may be, for example, an output obtained by rectifying and smoothing a commercial power supply, or an output of a boost chopper circuit that boosts the full-wave rectified voltage of the commercial power supply.

  The polarity inversion circuit 2 includes a series circuit of switching elements Q2 and Q3 connected in parallel between both ends of the capacitor C1, a series circuit of switching elements Q4 and Q5, and a drive circuit 21 for alternately turning on / off the switching elements Q2 and Q3. And a drive circuit 22 for alternately turning on and off the switching elements Q4 and Q5, and a full bridge type inverter circuit. The connection point between the switching elements Q2 and Q3 and the connection point between the switching elements Q4 and Q5 A series circuit of an inductor L2 and a capacitor C2 constituting a resonance circuit is connected between them, and a discharge lamp La is connected between both ends of the capacitor C2.

  The drive circuits 21 and 22 (for example, using IR2111 manufactured by IR) are in a state where the switching elements Q2 and Q5 are turned on and the switching elements Q3 and Q4 are turned off by the full bridge circuit 44 provided in the control circuit 4. The switching elements Q2 to Q5 are driven so that the switching elements Q2 and Q5 are turned off and the switching elements Q3 and Q4 are alternately turned on, and a rectangular wave alternating voltage is applied to the discharge lamp La.

  The discharge lamp La is a high-intensity high-pressure discharge lamp (HID lamp). At startup, the switching elements Q2 to Q5 are switched at a high frequency (several tens KHz to hundreds of tens KHz), and the resonant action of the inductor L2 and the capacitor C2 A high frequency high voltage is applied to the discharge lamp La to cause dielectric breakdown, and energy for shifting from glow discharge to arc discharge is supplied. This starting operation may be configured such that a high voltage is applied to the discharge lamp La by a separately provided igniter circuit. After starting, the switching elements Q2 to Q5 are switched at a low frequency (several Hz to several hundred Hz), and the voltage of the capacitor C1 is alternately inverted in polarity at a low frequency and applied to the discharge lamp La.

  The lamp voltage detection circuit 3 includes a series circuit of resistors R2 and R3 that divides the voltage of the capacitor C1, and a voltage across the resistor R3 is output as a lamp voltage detection signal Yv.

  The control circuit 4 monitors the chopper current and the lamp voltage based on the current detection signal Yi and the lamp voltage detection signal Yv, and outputs a control signal for controlling on / off of the switching elements Q1 to Q5. 4, a microcomputer 41 (hereinafter referred to as a microcomputer 41, for example, using M37540 or M37542 manufactured by Renesas), a switch 42 for switching the output of the two systems of the microcomputer 41, and reception via the switch 42 The PWM control circuit 43 that controls the operation of the switching element Q1 of the step-down chopper circuit 1 based on the command from the microcomputer 41, and the operations of the switching elements Q2 to Q5 of the polarity inversion circuit 2 based on the command from the microcomputer 41 And a full bridge control circuit 44 for controlling.

  The microcomputer 41 includes a lighting frequency setting unit 41a, a power control reference signal generation unit 41b, a data table 41c, an A / D conversion unit 41d, and a time measurement processing unit 41e. The A / D conversion unit 41d converts the lamp voltage detection signal Yv from the lamp voltage detection circuit 3 into a digital signal and outputs the digital signal to the lighting frequency setting unit 41a, the power control reference signal generation unit 41b, and the time measurement processing unit 41e. To do.

  The lighting frequency setting unit 41a refers to the data table 41c based on the lamp voltage detection signal Yv, determines the switching frequency of the switching elements Q2 to Q5 of the polarity inverting circuit 2, and determines the inverter control signal Yf1, based on this switching frequency. Yf2 is output to the full bridge control circuit 44. The full bridge control circuit 44 controls the drive circuits 21 and 22 so as to drive the switching elements Q2 to Q5 of the polarity inverting circuit 2 on and off at the switching frequency indicated by the inverter control signals Yf1 and Yf2.

  The power control reference signal generation unit 41b determines a starting state, a lighting state, and the like based on the switching frequency of the switching elements Q2 to Q5 set by the lighting frequency setting unit 41a, and further, a data table 41c based on the lamp voltage detection signal Yv. The two PWM signals Ym1 and Ym2 are output. The PWM signals Ym1 and Ym2 are controlled in duty so that the lamp current Ila has a desired amplitude.

  In addition, each process associated with the passage of time in the lighting frequency setting unit 41a and the power control reference signal generation unit 41b is performed in conjunction with the time measurement process of the time measurement processing unit 41e.

  The PWM signal Ym1 is smoothed by a filter circuit including a resistor R4 and a capacitor C3, and the DC voltage is input to the switch 42 as a chopper control reference signal Yp1. The PWM signal Ym2 is smoothed by a filter circuit including a resistor R5 and a capacitor C4, and the DC voltage is input to the switch 42 as a chopper control reference signal Yp2. The switch 42 is configured by a MOSFET, a transistor, an analog switch, and the like, and switches the internal contact by a switching signal Ys from the power control reference signal generation unit 41b and outputs the chopper control reference signal Yp1 or Yp2 to the PWM control circuit 43. . The PWM control circuit 43 controls the lamp current Ila by driving the switching element Q1 of the step-down chopper circuit 1 on and off based on the chopper control reference signal Yp1 or Yp2 and the current detection signal Yi. If the microcomputer 41 has a D / A conversion function, the microcomputer 41 may generate and output the chopper control reference signals Yp1 and Yp2.

  Then, the power control reference signal generation unit 41b uses the PWM signal Ym2 during start-up (during high-frequency operation of the switching elements Q2 to Q5) to cause dielectric breakdown of the discharge lamp La, and after the dielectric breakdown, a predetermined value is obtained. The voltage of the capacitor C1 is set to a voltage that can supply a high-frequency current. After lighting (during low frequency operation of the switching elements Q2 to Q5), the voltage of the capacitor C1 is controlled by controlling the step-down chopper circuit 1 using the PWM signals Ym1 and Ym2 so that the lamp current Ila has a desired waveform. Is optimized.

  Next, the waveform control of the lamp current Ila after lighting by the control circuit 4 will be described with reference to FIG. First, as shown in FIG. 13C, the basic waveform of the lamp current Ila after lighting is in one cycle of a rectangular wave whose polarity is inverted at an amplitude Ip1 (hereinafter referred to as a first current peak value Ip1). Continuously, a pulse waveform having an amplitude of Ip2 (hereinafter referred to as a second current peak value Ip2) is formed, and the first current peak value Ip1 and the second current peak value Ip2 are alternately arranged at predetermined intervals. And Ip1 <Ip2. In the rectangular wave of the first current peak value Ip1, the first half period Tf is longer than the second half period Tr.

  Then, as shown in FIG. 2B, from the lighting start t0 of the discharge lamp La to the switching time (first time) t1, the switch 42 is chopped by the switching signal Ys from the power control reference signal generation unit 41b. By switching to the control reference signal Yp2 side, the PWM control circuit 43 changes the lamp current Ila so that the first current peak value Ip11 and the second current peak value Ip21 (Ip11 <Ip21) are obtained by the chopper control reference signal Yp2. Control. That is, the waveform control of the lamp current Ila by the PWM signal Ym2 is performed until the switching time t1.

  After the switching time t1, the switch 42 is switched to the chopper control reference signal Yp1 side by the switching signal Ys from the power control reference signal generation unit 41b, and the PWM control circuit 43 uses the chopper control reference signal Yp1 to generate the first current. The lamp current Ila is controlled so that the peak value Ip12 and the second current peak value Ip22 (Ip12 <Ip22) are obtained. That is, after the switching time t1, the waveform control of the lamp current Ila by the PWM signal Ym1 is performed.

  The PWM signals Ym1 and Ym2 for setting the current peak values Ip11, Ip21, Ip12, and Ip22 are generated by the power control reference signal generation unit 41b based on the lamp voltage detection signal Yv in the data table 41c shown in FIG. It is generated with reference to D1, D2, D3, D5 and D6.

  Further, the lighting frequency setting unit 41a generates inverter control signals Yf1, Yf2 based on the lamp voltage detection signal Yv with reference to data D1, D4, D7 in the data table 41c shown in FIG. By controlling the polarity inversion timing of the polarity inverting circuit 2 by the control signals Yf1 and Yf2, the time widths T21 and T22 of the current peak values Ip21 and Ip22 are set to desired time widths.

  The first current peak value is set to Ip11 = Ip12, the second current peak value is set to Ip21> Ip22, and the time width of the second current peak value is set to T21> T22. That is, both the second current peak value Ip2 and its time width T2 are changed before and after the switching time t1, and as shown in FIG. 2 (a), the second peak from the lighting start t0 to the switching time t1. The product a1 = [Ip21 × T21] of the current peak value Ip21 and the time width T21 is larger than the product a2 = [Ip22 × T22] of the second current peak value Ip22 and the time width T22 after the switching time t1.

  Then, after starting lighting, until the temperature of the electrode rises to some extent, the lamp current Ila becomes a current limiting region Ta that is controlled so as not to exceed the limiting current I1, and the constant power control that controls the lamp power from the current limiting region Ta is constant. The transition time t1 is shifted to the region Tb and steady lighting is performed. However, as shown in FIGS. 4A and 4B, the switching time t1 is after the transition to the constant power control region Tb. It is set in advance from several minutes to several tens of minutes (for example, the timing at which the electrode temperature reaches a predetermined temperature) in the generation unit 41b, and is determined in consideration of variations in the discharge lamp La, current waveforms, and the like.

  Then, while maintaining the relationship that the product a1 = [Ip21 × T21] before the switching time t1 is larger than the product a2 = [Ip22 × T22] after the switching time t1, the constant power control region Tb from the current limiting region Ta is maintained. If the product a1 = [Ip21 × T21] and the product a2 = [Ip22 × T22] are controlled so that the lamp power becomes constant after the transition to, each characteristic of the lamp voltage Vla and the lamp current Ila of this embodiment is controlled. As shown by the solid lines in FIGS. 4A and 4B, X1 and X2 do not increase the lamp voltage Vla as in the conventional characteristic X11 after the transition to the constant power control region Tb. The lamp voltage Ila and the lamp current Ila become substantially constant without a decrease in the lamp current Ila as in the characteristic X12.

  That is, after the transition to the constant power control region Tb, the lamp current Ila is reduced in order to keep the lamp power constant with respect to the increase of the lamp voltage Vla. Since the second current peak value Ip21 having a large amplitude is periodically generated with a long time width T21 until the switching time t1 even after the transition of, the temperature drop of the electrodes can be suppressed and the distance between the electrodes can be widened. In other words, the rise of the lamp voltage Vla is suppressed.

  Thus, when a discharge lamp La having a high lamp voltage Vla is used due to factors such as the end of the lamp life, flicker is likely to occur due to insufficient temperature of the electrode immediately after the transition to the constant power control region Tb. However, in the present embodiment, the temperature of the electrode is sufficiently maintained even after the transition to the constant power control region Tb, and the occurrence of flicker can be suppressed.

  Also, by suppressing flicker, the brightness decreases due to the increase in lamp voltage due to electrode wear, and the brightness decreases due to devitrification due to scattering of electrode material and adhering to the inside of the lamp tube. It is possible to prevent the lamp life from being shortened.

(Embodiment 2)
The circuit configuration of the discharge lamp lighting device of the present embodiment is shown in FIG. 1 as in the first embodiment, and the same components are denoted by the same reference numerals and the description thereof is omitted.

  In the present embodiment, as shown in FIG. 5B, the lamp current Ila from the lighting start t0 of the discharge lamp La to the switching time t1 is a first current peak value Ip11 and a second current peak value Ip21 ( Ip11 <Ip21), the lamp current Ila after the switching time t1 is the first current peak value Ip12 and the second current peak value Ip22 (Ip12 <Ip22), the first current peak value: Ip11 = Ip12, the second Current peak value: Ip21> Ip22. Further, the time widths T21 and T22 of the second current peak values Ip21 and Ip22 are set to T21 = T22, and have the same time width. That is, as shown in FIG. 5A, only the second current peak value Ip2 is changed before and after the switching time t1, and the second current peak value Ip21 from the lighting start t0 to the switching time t1 is changed. The product a1 = [Ip21 × T21] with the time width T21 is larger than the product a2 = [Ip22 × T22] of the second current peak value Ip22 and the time width T22 after the switching time t1.

  Then, after starting lighting, until the temperature of the electrode rises to some extent, the lamp current Ila becomes a current limiting region Ta that is controlled so as not to exceed the limiting current I1, and the constant power control that controls the lamp power from the current limiting region Ta is constant. The transition time t1 is shifted to the region Tb and steady lighting is performed. However, as shown in FIGS. 4A and 4B, the switching time t1 is after the transition to the constant power control region Tb. It is set in advance from several minutes to several tens of minutes (for example, the timing at which the electrode temperature reaches a predetermined temperature) in the generation unit 41b, and is determined in consideration of variations in the discharge lamp La, current waveforms, and the like.

  Then, while maintaining the relationship that the product a1 = [Ip21 × T21] before the switching time t1 is larger than the product a2 = [Ip22 × T22] after the switching time t1, the constant power control region Tb from the current limiting region Ta is maintained. If the second current peak values Ip21 and Ip22 are controlled so that the lamp power becomes constant after shifting to, the characteristics X1 and X2 of the lamp voltage Vla and lamp current Ila of this embodiment are shown in FIG. ) As shown by the solid line in (b), after the transition to the constant power control region Tb, the lamp voltage Vla does not increase as in the conventional characteristic X11, and the lamp current Ila as in the conventional characteristic X12 does not increase. There is no decrease, and the lamp voltage Vla and the lamp current Ila become substantially constant.

  That is, after the transition to the constant power control region Tb, the lamp current Ila is reduced in order to keep the lamp power constant with respect to the increase of the lamp voltage Vla. Since the second current peak value Ip21 having a large amplitude is periodically generated until the switching time t1 even after the transition of, the temperature drop of the electrodes is suppressed, and the lamp voltage Vla is not increased without increasing the distance between the electrodes. The rise of is suppressed.

  Thus, when a discharge lamp La having a high lamp voltage Vla is used due to factors such as the end of the lamp life, flicker is likely to occur due to insufficient temperature of the electrode immediately after the transition to the constant power control region Tb. However, in the present embodiment, the temperature of the electrode is sufficiently maintained even after the transition to the constant power control region Tb, and the occurrence of flicker can be suppressed.

  Also, by suppressing flicker, the brightness decreases due to the increase in lamp voltage due to electrode wear, and the brightness decreases due to devitrification due to scattering of electrode material and adhering to the inside of the lamp tube. It is possible to prevent the lamp life from being shortened.

(Embodiment 3)
The circuit configuration of the discharge lamp lighting device of the present embodiment is shown in FIG. 1 as in the first embodiment, and the same components are denoted by the same reference numerals and the description thereof is omitted.

  In the present embodiment, as shown in FIG. 6B, the lamp current Ila from the lighting start t0 of the discharge lamp La to the switching time t1 is the first current peak value Ip11 and the second current peak value Ip21 ( Ip11 <Ip21), the lamp current Ila after the switching time t1 is the first current peak value Ip12, the second current peak value Ip22 (Ip12 <Ip22), and the first current from the lighting start t0 to the switching time t1. The ratio b1 = [Ip21 / Ip11] between the peak value Ip11 and the second current peak value Ip21 is the ratio b2 = [Ip22] between the first current peak value Ip12 and the second current peak value Ip22 after the switching time t1. / Ip12]. In addition, the time widths T21 and T22 of the second current peak values Ip21 and Ip22 are set to T21 = T22 and have the same time width. That is, as shown in FIG. 6A, the ratio b = (Ip2 / Ip1) between the first current peak value Ip1 and the second current peak value Ip2 is changed before and after the switching time t1. The product a1 = [Ip21 × T21] of the second current peak value Ip21 and the time width T21 from the lighting start t0 to the switching time t1 is the second current peak value Ip22 and the time width T22 after the switching time t1. Product a2 = greater than [Ip22 × T22].

  Then, after starting lighting, until the temperature of the electrode rises to some extent, the lamp current Ila becomes a current limiting region Ta that is controlled so as not to exceed the limiting current I1, and the constant power control that controls the lamp power from the current limiting region Ta is constant. The transition time t1 is shifted to the region Tb and steady lighting is performed. However, as shown in FIGS. 4A and 4B, the switching time t1 is after the transition to the constant power control region Tb. It is set in advance from several minutes to several tens of minutes (for example, the timing at which the electrode temperature reaches a predetermined temperature) in the generation unit 41b, and is determined in consideration of variations in the discharge lamp La, current waveforms, and the like.

  Then, while maintaining the relationship that the product a1 = [Ip21 × T21] before the switching time t1 is larger than the product a2 = [Ip22 × T22] after the switching time t1, the constant power control region Tb from the current limiting region Ta is maintained. If the ratio b1 = [Ip21 / Ip11] and the ratio b2 = [Ip22 / Ip12] are controlled so that the lamp power becomes constant after shifting to, each characteristic X1 of the lamp voltage Vla and the lamp current Ila of the present embodiment. , X2, as shown by the solid lines in FIGS. 4A and 4B, after the transition to the constant power control region Tb, the lamp voltage Vla does not increase as in the conventional characteristic X11, and the conventional characteristic There is no decrease in the lamp current Ila as in X12, and the lamp voltage Vla and the lamp current Ila become substantially constant.

  That is, after the transition to the constant power control region Tb, the lamp current Ila is reduced in order to keep the lamp power constant with respect to the increase of the lamp voltage Vla. Since the second current peak value Ip21 having a large ratio with respect to the first current peak value Ip11 is periodically generated until the switching time t1 even after the transition of, the temperature drop of the electrodes can be suppressed, and the distance between the electrodes Is suppressed, and the rise of the lamp voltage Vla is suppressed.

  Thus, when a discharge lamp La having a high lamp voltage Vla is used due to factors such as the end of the lamp life, flicker is likely to occur due to insufficient temperature of the electrode immediately after the transition to the constant power control region Tb. However, in the present embodiment, the temperature of the electrode is sufficiently maintained even after the transition to the constant power control region Tb, and the occurrence of flicker can be suppressed.

  Also, by suppressing flicker, the brightness decreases due to the increase in lamp voltage due to electrode wear, and the brightness decreases due to devitrification due to scattering of electrode material and adhering to the inside of the lamp tube. It is possible to prevent the lamp life from being shortened.

(Embodiment 4)
The circuit configuration of the discharge lamp lighting device of the present embodiment is shown in FIG. 1 as in the first embodiment, and the same components are denoted by the same reference numerals and the description thereof is omitted.

  In the present embodiment, as shown in FIG. 7B, the lamp current Ila from the lighting start t0 of the discharge lamp La to the switching time t1 is the first current peak value Ip11 and the second current peak value Ip21 ( Ip11 <Ip21), the lamp current Ila after the switching time t1 is the first current peak value Ip12 and the second current peak value Ip22 (Ip12 <Ip22), the first current peak value: Ip11 = Ip12, the second Current peak value: Ip21 = Ip22. The time widths T21 and T22 of the second current peak values Ip21 and Ip22 are set to T21> T22. That is, as shown in FIG. 7A, only the time width T2 of the second current peak value Ip2 is changed before and after the switching time t1, and the second current from the lighting start t0 to the switching time t1. The product a1 = [Ip21 × T21] of the peak value Ip21 and the time width T21 is larger than the product a2 = [Ip22 × T22] of the second current peak value Ip22 and the time width T22 after the switching time t1.

  Then, after starting lighting, until the temperature of the electrode rises to some extent, the lamp current Ila becomes a current limiting region Ta that is controlled so as not to exceed the limiting current I1, and the constant power control that controls the lamp power from the current limiting region Ta is constant. The transition time t1 is shifted to the region Tb and steady lighting is performed. However, as shown in FIGS. 4A and 4B, the switching time t1 is after the transition to the constant power control region Tb. It is set in advance from several minutes to several tens of minutes (for example, the timing at which the electrode temperature reaches a predetermined temperature) in the generation unit 41b, and is determined in consideration of variations in the discharge lamp La, current waveforms, and the like.

  Then, while maintaining the relationship that the product a1 = [Ip21 × T21] before the switching time t1 is larger than the product a2 = [Ip22 × T22] after the switching time t1, the constant power control region Tb from the current limiting region Ta is maintained. If the time width T21 of the second current peak value Ip21 and the time width T22 of the second current peak value Ip22 are controlled so that the lamp power becomes constant after the transition to, the lamp voltage Vla, As shown by the solid lines in FIGS. 4A and 4B, the characteristics X1 and X2 of the lamp current Ila increase after the transition to the constant power control region Tb, as the lamp voltage Vla increases as in the conventional characteristic X11. Further, there is no decrease in the lamp current Ila as in the conventional characteristic X12, and the lamp voltage Vla and the lamp current Ila become substantially constant.

  That is, after the transition to the constant power control region Tb, the lamp current Ila is reduced in order to keep the lamp power constant with respect to the increase of the lamp voltage Vla. Since the second current peak value Ip21 is periodically generated with a long time width T21 until the switching time t1 even after the transition of, the temperature drop of the electrodes is suppressed and the distance between the electrodes is not increased. The increase in voltage Vla is suppressed.

  Thus, when a discharge lamp La having a high lamp voltage Vla is used due to factors such as the end of the lamp life, flicker is likely to occur due to insufficient temperature of the electrode immediately after the transition to the constant power control region Tb. However, in the present embodiment, the temperature of the electrode is sufficiently maintained even after the transition to the constant power control region Tb, and the occurrence of flicker can be suppressed.

  Also, by suppressing flicker, the brightness decreases due to the increase in lamp voltage due to electrode wear, and the brightness decreases due to devitrification due to scattering of electrode material and adhering to the inside of the lamp tube. It is possible to prevent the lamp life from being shortened.

(Embodiment 5)
The circuit configuration of the discharge lamp lighting device of the present embodiment is shown in FIG. 1 as in the first embodiment, and the same components are denoted by the same reference numerals and the description thereof is omitted.

  In the present embodiment, as shown in FIG. 8C, the lamp current Ila in the current limiting region Ta has a first current peak value Ip11 and a second current peak value Ip21 (Ip11 <Ip21), The current peak value Ip11 and the second current peak value Ip21 are controlled to be constant. When the lamp current Ila falls below the limit current I1 from the current limit area Ta to the constant power control area Tb, the first current peak value Ip11 ′ and the second current peak value Ip21 ′ are obtained until the switching time t1. (Ip11 ′ <Ip21 ′), the first current peak value Ip11 ′, and the second current peak value Ip21 ′ are controlled so that the lamp power is constant. The time widths of the second current peak values Ip21 and Ip21 'are the same time width T21.

  Then, the lamp current Ila after the switching time t1 is set as the first current peak value Ip12 and the second current peak value Ip22 (Ip12 <Ip22), and the ratio b1 = [Ip21 / Ip11] before the switching time t1 and the ratio b1 ′ = [Ip21 ′ / Ip11 ′] is set to be larger than the ratio b2 = [Ip22 / Ip12] after the switching time t1. The time width T21 of the second current peak value Ip21, 21 'before the switching time t1 is set to be longer than the time width T22 of the second current peak value Ip22 after the switching time t1.

  That is, before and after the switching time t1, the ratio b = (Ip2 / Ip1) between the first current peak value Ip1 and the second current peak value Ip2 and the time width T2 of the second current peak value Ip2 are changed. The product a1 = [Ip21 × T21] of the second current peak value Ip21 and the time width T21 from the lighting start t0 to the switching time t1, and the second current peak value Ip21 ′ and the time width T21 The product a1 ′ = [Ip21 ′ × T21] is larger than the product a2 = [Ip22 × T22] of the second current peak value Ip22 and the time width T22 after the switching time t1.

  Then, maintaining the relationship that the product a1 = [Ip21 × T21] before the switching time t1 and the product a1 ′ = [Ip21 ′ × T21] are larger than the product a2 = [Ip22 × T22] after the switching time t1. If the lamp power is controlled to be constant after the current limit area Ta is shifted to the constant power control area Tb, the characteristics X1 and X2 of the lamp voltage Vla and the lamp current Ila of this embodiment are shown in FIG. a) As shown in (b), after the transition to the constant power control region Tb, the lamp voltage Vla does not increase as in the conventional characteristic X11, and the lamp current Ila decreases as in the conventional characteristic X12. As a result, the lamp voltage Vla and the lamp current Ila become substantially constant.

  That is, after the transition to the constant power control region Tb, the lamp current Ila is reduced in order to keep the lamp power constant with respect to the increase of the lamp voltage Vla. Since the second current peak value Ip21 ′ having a large ratio with respect to the first current peak value Ip11 ′ is periodically generated with a long time width T21 until the switching time t1 even after the transition of FIG. This suppresses the increase in the lamp voltage Vla without increasing the distance between the electrodes. Further, by switching between two parameters, the ratio b between the first current peak value Ip11 and the second current peak value Ip21 and the time width T2 of the second current peak value Ip2, the components of the step-down chopper circuit 1 can be switched. Such stress can be reduced.

  Thus, when a discharge lamp La having a high lamp voltage Vla is used due to factors such as the end of the lamp life, flicker is likely to occur due to insufficient temperature of the electrode immediately after the transition to the constant power control region Tb. However, in the present embodiment, the temperature of the electrode is sufficiently maintained even after the transition to the constant power control region Tb, and the occurrence of flicker can be suppressed.

  Also, by suppressing flicker, the brightness decreases due to the increase in lamp voltage due to electrode wear, and the brightness decreases due to devitrification due to scattering of electrode material and adhering to the inside of the lamp tube. It is possible to prevent the lamp life from being shortened.

(Embodiment 6)
The circuit configuration of the discharge lamp lighting device of the present embodiment is shown in FIG. 1 similarly to the first embodiment, and the same components are denoted by the same reference numerals and the description thereof is omitted.

  In the present embodiment, in the first to fifth embodiments, the switching time t1 that is the timing for switching the first current peak value Ip1, the second current peak value Ip2, the time width T2, and the like is based on the variation rate of the lamp voltage Vla. The change time of the lamp voltage Vla is small and the lamp voltage is stabilized is set as the switching time t1 (see FIGS. 9A and 9C).

  FIG. 10 shows an operation flowchart thereof. First, the lamp voltage detection circuit 3 detects the lamp voltage and outputs a lamp voltage detection signal Yv (step S1). The power control reference signal generation unit 41b A lamp voltage value is read based on the lamp voltage detection signal Yv converted into a digital signal at the sampling period (step S2). The power control reference signal generation unit 41b calculates the difference | ΔVla | (see FIG. 9B) between the lamp voltage value read this time and the lamp voltage value read last time as a variation rate of the lamp voltage Vla (step S3). ), It is determined whether or not the voltage difference | ΔVla | is equal to or lower than a threshold voltage Va (for example, 10 V) (step S4). If the voltage difference | ΔVla | is equal to or less than the threshold voltage Va, the detection frequency counter in the power control reference signal generation unit 41b is incremented once (step S5), and whether or not the detection frequency has reached N times. Is determined (step S6). If the number of detections has not reached N, the process returns to step S1 (step S9). When the number of times of detection reaches N times, the switch 42 is switched from the chopper control reference signal Yp2 side to the Yp1 side with the switching time t1 (step S7), and the process returns to step S1 (step S9). If the voltage difference | ΔVla | exceeds the threshold voltage Va in step S4, the stored number of detections is reset to 0 (step S8), and the process returns to step S1 (step S9).

  Thus, since the switching time t1 is set based on the variation rate of the lamp voltage, the switching time t1 can be set appropriately even if the state of the discharge lamp La changes. The sampling period for reading the threshold voltage Va, the number of detections N, and the lamp voltage value is set to an optimum value depending on the characteristics of the discharge lamp and the circuit configuration.

(Embodiment 7)
The circuit configuration of the discharge lamp lighting device of the present embodiment is shown in FIG. 1 as in the first embodiment, and the same components are denoted by the same reference numerals and the description thereof is omitted.

  In this embodiment, from the lighting start t0 of the discharge lamp La to the time (second time) t2 when the lamp voltage Vla reaches the threshold voltage Vb, as shown in FIG. Current peak value Ip11 and second current peak value Ip21, and the first current peak value Ip11 and the second current peak value Ip21 are controlled to the same current value (Ip11 = Ip21). This is because the period from the lighting start t0 to the time t2 is included in the current limiting region Ta, and a sufficient current flows to the electrode of the discharge lamp La, so the second current peak value Ip21 is Even if it is not larger than the current peak value Ip11 of 1, the temperature of the electrode does not become insufficient, and further, since the lamp current is not increased more than necessary, there is an effect that the deterioration of the electrode can be suppressed. The comparison process between the ramp voltage Vla and the threshold voltage Vb can be performed without chattering by providing a hysteresis of several volts.

  Next, the lamp current Ila from the time t2 to the switching time t1 is a first current peak value Ip11 ′ and a second current peak value Ip21 ′ (Ip11 ′ <Ip21 ′), and is constant during the current limiting region Ta. Controlled. Then, when the lamp current Ila becomes equal to or less than the limit current I1 from the current limit area Ta to the constant power control area Tb, the first current peak value Ip11 ′ and the second current peak value Ip21 until the switching time t1. 'Is controlled so that the lamp power is constant. The time widths of the second current peak values Ip21 and Ip21 'are the same time width T21.

  Next, the lamp current Ila after the switching time t1 has a first current peak value Ip12 and a second current peak value Ip22 (Ip12 <Ip22), and the ratio b1 = [Ip21 / Ip11], b1 before the switching time t1. '= [Ip21' / Ip11 '] is set to be larger than the ratio b2 = [Ip22 / Ip12] after the switching time t1. The time width T21 of the second current peak value Ip21, 21 'before the switching time t1 is set to be longer than the time width T22 of the second current peak value Ip22 after the switching time t1.

  That is, before and after the switching time t1, the ratio b = (Ip2 / Ip1) between the first current peak value Ip1 and the second current peak value Ip2 and the time width T2 of the second current peak value Ip2 are changed. The product a1 = [Ip21 × T21] of the second current peak value Ip21 and the time width T21 from the lighting start t0 to the switching time t1, and the second current peak value Ip21 ′ and the time width T21 The product a1 ′ = [Ip21 ′ × T21] is larger than the product a2 = [Ip22 × T22] of the second current peak value Ip22 and the time width T22 after the switching time t1.

  Then, maintaining the relationship that the product a1 = [Ip21 × T21] before the switching time t1 and the product a1 ′ = [Ip21 ′ × T21] are larger than the product a2 = [Ip22 × T22] after the switching time t1. If the lamp power is controlled to be constant after the current limit area Ta is shifted to the constant power control area Tb, the characteristics X1 and X2 of the lamp voltage Vla and the lamp current Ila of this embodiment are shown in FIG. a) As shown in (b), after the transition to the constant power control region Tb, the lamp voltage Vla does not increase as in the conventional characteristic X11, and the lamp current Ila decreases as in the conventional characteristic X12. As a result, the lamp voltage Vla and the lamp current Ila become substantially constant.

  That is, after the transition to the constant power control region Tb, the lamp current Ila is reduced in order to keep the lamp power constant with respect to the increase of the lamp voltage Vla. Since the second current peak value Ip21 ′ having a large ratio with respect to the first current peak value Ip11 ′ is periodically generated with a long time width T21 until the switching time t1 even after the transition of FIG. This suppresses the increase in the lamp voltage Vla without increasing the distance between the electrodes.

  Thus, when a discharge lamp La having a high lamp voltage Vla is used due to factors such as the end of the lamp life, flicker is likely to occur due to insufficient temperature of the electrode immediately after the transition to the constant power control region Tb. However, in the present embodiment, the temperature of the electrode is sufficiently maintained even after the transition to the constant power control region Tb, and the occurrence of flicker can be suppressed.

  Also, by suppressing flicker, the brightness decreases due to the increase in lamp voltage due to electrode wear, and the brightness decreases due to devitrification due to scattering of electrode material and adhering to the inside of the lamp tube. It is possible to prevent the lamp life from being shortened.

  In the first to seventh embodiments, the basic waveform of the lamp current Ila is the waveform shown in FIG. 13C. However, the waveform is not limited to this waveform. For example, FIGS. 13A, 13B, and 13D are used. The same effect can be obtained by controlling the waveform in the same manner as described above using the waveform of (e) as the basic waveform.

(Embodiment 8)
This embodiment demonstrates the image display apparatus using the discharge lamp lighting device in any one of the said Embodiments 1-7. FIG. 12 shows the configuration of the image display device. In the housing 5, the discharge lamp lighting device H according to any one of the first to seventh embodiments and the short arc exceeding the lighting control by the discharge lamp lighting device H are shown. A discharge lamp La composed of a high-pressure mercury lamp, an optical device K1, a power supply unit K2, an external signal input unit K3, and three fans K4 are housed, and a discharge lamp lighting device H, an optical device K1, and a power supply unit K2 is mounted on the main control board K5.

  The optical device K1 includes means for transmitting or reflecting light from the discharge lamp La and means for projecting transmitted light or reflected light through the means onto a screen.

  By using the discharge lamp lighting device according to any one of Embodiments 1 to 7 as the image display device, the occurrence of flicker due to the movement of the bright spot immediately after shifting to the constant power control region is suppressed, and the life of the lamp is shortened. Therefore, the image quality can be improved, and a further excellent image quality can be maintained for a long time.

It is a figure which shows the circuit structure of the discharge lamp lighting device of Embodiment 1. FIG. (A) (b) It is a figure which shows lamp current control same as the above. It is a figure which shows a data table same as the above. (A) (b) It is a figure which shows each characteristic of the lamp voltage and lamp current same as the above. (A) (b) It is a figure which shows the lamp current control of Embodiment 2. FIG. (A) (b) It is a figure which shows the lamp current control of Embodiment 3. FIG. (A) (b) It is a figure which shows the lamp current control of Embodiment 4. FIG. (A)-(c) It is a figure which shows the lamp current control of Embodiment 5. FIG. (A)-(c) It is a figure which shows the setting process of the switching time of Embodiment 6. FIG. It is a figure which shows an operation | movement flowchart same as the above. (A)-(c) It is a figure which shows the setting process of the switching time of Embodiment 7. FIG. It is a figure which shows the structure of the image display apparatus of Embodiment 8. (A)-(e) It is a figure which shows the basic waveform of a lamp current. It is a figure which shows the basic operation | movement of (a)-(c) lamp current control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Step-down chopper circuit 2 Polarity inversion circuit 3 Lamp voltage detection circuit 4 Control circuit 41 Microcomputer 42 Switch 43 PWM control circuit 44 Full bridge control circuit Q1-Q5 Switching element La Discharge lamp

Claims (9)

A power conversion circuit for supplying power to the discharge lamp by turning on and off the switching element;
By controlling on / off of the switching elements of the power conversion circuit, after starting lighting, the lamp is shifted from the current limit area where the lamp current does not exceed the limit current to the constant power control area where the lamp power is controlled to be constant. A control circuit for controlling a lamp current supplied to the discharge lamp at the time of lighting into a waveform in which a first amplitude and a second amplitude larger than the first amplitude are alternately generated at a predetermined interval;
With
When the first time has elapsed from the start of lighting in the constant power control region, the control circuit calculates the product of the second amplitude of the lamp current after the first time and the time width of the second amplitude as the first time. The discharge lamp lighting device is characterized by being made smaller than the product of the second amplitude and the time width of the second amplitude of the lamp current before this time.   2. The discharge lamp lighting device according to claim 1, wherein the control circuit makes the second amplitude of the lamp current after the first time smaller than the second amplitude of the lamp current before the first time. .   The control circuit makes the ratio of the second amplitude to the first amplitude of the lamp current after the first time smaller than the ratio of the second amplitude to the first amplitude of the lamp current before the first time. The discharge lamp lighting device according to claim 1.   2. The control circuit according to claim 1, wherein the time width of the second amplitude of the lamp current after the first time is made smaller than the time width of the second amplitude of the lamp current before the first time. The discharge lamp lighting device described.   The control circuit sets the ratio of the second amplitude to the first amplitude of the lamp current and the time width of the second amplitude after the first time, and the first amplitude of the lamp current before the first time. 2. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is smaller than the ratio of the amplitude of 2 and the time width of the second amplitude.   A lamp voltage detection circuit for detecting a lamp voltage is provided, and the control circuit detects the second amplitude and the second amplitude of the lamp current after the first time when the variation rate of the detected lamp voltage becomes smaller than a predetermined value. 6. The product of the amplitude and the time width of the lamp current is made smaller than the product of the second amplitude of the lamp current and the time width of the second amplitude before the first time. Discharge lamp lighting device.   The control circuit sets the first amplitude and the second amplitude of the lamp current to the same value until a second time elapses from the start of lighting in the current limiting region. 6. The discharge lamp lighting device according to any one of 6.   8. The discharge lamp lighting device according to claim 7, wherein the second time is a timing at which the lamp voltage after starting lighting reaches a predetermined voltage.   The discharge lamp lighting device according to any one of claims 1 to 8, the discharge lamp that is lit by the discharge lamp lighting device, and the light from the discharge lamp is transmitted or reflected, and the transmitted light or reflected light is projected onto the screen. An image display device comprising: an optical means for performing the operation.

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