JP2012114009A - Dc lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively suppress evaporative wear of electrode members under increased temperature when lighting a DC lighting type of high pressure discharge lamp.SOLUTION: A DC lamp lighting device (1) includes a PWM control circuit (21) for performing constant power control to maintain a lamp power calculated from a lamp current and a lamp voltage at a preset rated power. The control circuit (21) includes: current priority control means (23) for maintaining the lamp current at a constant target current value set lower than a rated current; power priority control means (24) for compensating for a power drop resulting from the current reduction by the current priority control means (23) to maintain an average power at the rated power; and timing control means (25) for alternately switching between the control means at a preset control period on the order of milliseconds.

Description

  The present invention relates to a direct-current lamp lighting device for lighting a direct-current lighting type high-pressure discharge lamp in which a pair of electrodes are disposed facing each other in a discharge vessel of an arc tube, and a light source device using the direct-current lamp lighting device.

For example, various inspection light source devices use a metal halide lamp having a distance between electrodes of about 2 to 2.5 mm as opposed to the discharge vessel of the arc tube as a high-pressure discharge lamp serving as the light source. In general, recently, the amount of mercury enclosed in the discharge vessel is set to 0.15 mg / mm ³ or more, and the distance between the electrodes arranged opposite to each other in the discharge vessel is set to 1.5 mm or less. Increasingly, a short arc type ultra-high pressure mercury lamp that generates light close to a point light source that is easy to control light distribution with brightness is increasing.

  In particular, an inspection light source device that collects light emitted from a high-pressure discharge lamp as a light source with an elliptical reflector and transmits it to an irradiation position with a light guide is a light emitting point of a lamp disposed at the primary focal position of the elliptical reflector. As the light emitted from the light source becomes brighter and closer to a point light source, the amount of light incident on the light guide increases and the light utilization efficiency improves.At the same time, the light guide has a sufficient amount of light to obtain the required illuminance Therefore, many high-pressure discharge lamps using short arc type ultra-high pressure mercury lamps are used as the light source.

  This type of high-pressure discharge lamp tends to increase the lamp voltage due to the increase in the cumulative lighting time and the evaporation wear at the electrode tip as the cumulative lighting time increases. For this reason, in the case of constant current control, there is a risk that the lamp input power will rise and the lamp may be destroyed. Therefore, the lighting control is generally performed by constant power control except at the start of lighting (see Patent Document 1).

However, according to the inventor's experimental study, when constant power control is performed, when the lamp operating voltage (lamp voltage) is low at the beginning of lighting when the distance between the electrodes is short, that is, the lamp operating current ( When the lamp current is relatively high, the evaporation wear of the electrode member such as the electrode or the tip of the electrode shaft and the coil wound around the electrode shaft is the most significant. It has been confirmed that when the distance between the electrodes increases, the lamp voltage gradually increases and the lamp current decreases, the evaporation wear of the electrode members also decreases.
That is, it was found that when the lamp is lit with constant power control, the evaporation loss of the electrode member becomes most noticeable at the beginning of lighting of the lamp having a relatively high lamp current.

Evaporative wear of electrode members occurs not only at the electrode or the tip of the electrode shaft that is at the highest temperature in contact with the arc, but also at the coil wound around the electrode shaft to ensure startability and prevent overheating of the electrode. For example, a coil made of a tungsten wire wound around an electrode shaft of a tungsten electrode promotes heat dissipation from the electrode shaft when the lamp is lit, but does not increase until its temperature reaches its melting point. It gradually evaporates.
Further, tungsten evaporated from the coil may adhere to the inner surface of the discharge vessel of the arc tube and cause blackening of the arc tube. Further, when the evaporation wear of the coil progresses, the wire diameter of the coil increases. It becomes gradually thinner and part of it may be lost, and these phenomena are factors that deteriorate lamp life characteristics.

In addition, the light source device 31 shown in FIG. 7 places the center (light emission point) of the high pressure discharge lamp 3 and the discharge vessel 5 of the arc tube 4 at the primary focal position, and secondaryly emits light emitted from the lamp 3. A lamp unit 32 composed of an elliptical reflecting mirror 9 for condensing light at the focal point is installed in a housing case 35 provided with a light exit port 34 for connecting a ride guide 33, and between the light exit port 34 and the lamp unit 32. A filter 36 such as a wavelength selection filter and / or a neutral density filter is interposed in the vicinity of the secondary focal point located at the position.
In the light source device 31, when the light collected by the elliptical reflecting mirror 34 is guided to the light guide 33, a part of the light component reflected by the filter 36 returns to the vicinity of the primary focal point of the elliptical reflecting mirror 9. In order to raise the temperature of the electrode member in the discharge vessel arranged near the primary focal position, the evaporation wear of the electrode member becomes more remarkable.

  Therefore, in order to block the light reflected and returned by the wavelength selection filter or the neutral density filter, there is provided means for providing a temperature suppression processing portion with an infrared reflecting film or a frost processing on the surface of the discharge vessel on the reflection mirror opening side. Although it has been proposed (see Patent Document 2), it is not preferable to apply such processing to the surface of the discharge vessel because not only the productivity of the lamp will be lowered but also the reliability thereof may be lowered.

  In addition, in order to suppress / suppress the evaporation loss of the electrode member due to the above causes, if the distance between the electrodes of the short arc type ultra-high pressure mercury lamp is set long in advance, that is, the design value of the distance between the electrodes If it is longer than 1.5 mm, for example, 2 mm, the maximum advantage of the lamp that a point light source with high brightness and easy light distribution control can be obtained is lost, which is also not preferable.

Japanese Patent Laid-Open No. 10-335086 JP 2010-061816 A

  In the present invention, when a direct current lighting type high pressure discharge lamp in which a pair of electrodes are arranged to face each other in a discharge vessel of an arc tube is lit, the high pressure discharge lamp as a light source has a short distance between the electrodes. Even if it exists, it is making it a technical subject to improve the lifetime characteristic by suppressing effectively the evaporation wear by the temperature rise of an electrode member, especially the coil wound around the electrode shaft.

In order to solve the above-described problems, the present invention provides PWM control of DC power supplied during stable lighting to a DC lighting type high-pressure discharge lamp in which a pair of electrodes are opposed to each other in a discharge vessel of an arc tube. And a PWM signal supplied to the switching element so that the lamp operating power calculated based on the lamp operating current and the lamp operating voltage is maintained at a preset rated power. In a DC lamp lighting device including a PWM control circuit that performs constant power control by determining a duty ratio of
The PWM control circuit compensates for the electric power that has fallen due to the current priority control means for maintaining the lamp operating current at a constant target current value set lower than the rated current and the current priority control means. Power priority control means for maintaining the average power at the rated power, and timing control means for alternately switching these control means at a preset control cycle in the millisecond order.

According to the DC lamp lighting device of the present invention, the high-pressure discharge lamp is supplied with current priority control for maintaining the lamp operating current at a constant target current value set lower than the rated current, and the current is reduced by the current priority control means. Constant power control is performed by alternately switching power feeding based on power priority control that compensates for the power that has dropped due to this and maintains the average power at the rated power at a control cycle in the order of milliseconds.
While the power is supplied by the current priority control means, the lamp operating current is maintained at a constant target current value set lower than the rated current regardless of the lamp voltage. In addition, evaporation wear due to the temperature rise of the electrode member is suppressed, and the life characteristics are improved.
Further, while the power is supplied by the power priority control means, the average power is maintained at the rated power by compensating for the reduced power due to the current reduction by the current priority control means. Thus, even if the lamp voltage rises as the cumulative lighting time increases, the lamp input power does not increase and the lamp is not destroyed as in the case of constant current control.
Furthermore, since the power supply by the current priority control unit and the power supply by the power priority control unit are executed in a cycle on the order of milliseconds, and the cycle is extremely short, there is an excellent effect that flicker due to fluctuations in lamp operating current does not occur.

The circuit diagram which shows an example of the DC lamp lighting device which concerns on this invention. The enlarged view of a cathode side electrode. The graph which shows the relationship between a control period and electric current control time. Flow chart showing processing procedure of lighting control device The graph which shows the electric current, voltage, and electric power change in a control period. The graph which shows the relationship between accumulation lighting time and lamp current. Explanatory drawing which shows a light source device.

  The present invention has an effect of evaporative wear due to the temperature rise of the electrode member even when a direct current lighting type high-pressure discharge lamp in which a pair of electrodes are opposed to each other in the discharge vessel of the arc tube is short. In order to achieve the objective of improving the life characteristics by controlling the power supply, the PWM control circuit that performs constant power control on the DC lighting type high-pressure discharge lamp has a constant lamp operating current set lower than the rated current. Current priority control means for maintaining the target current value, power priority control means for maintaining the average power at the rated power by making up for the power that has dropped due to the reduction in current by the current priority control means, and each of these controls And timing control means for switching the means alternately in a preset control cycle of millisecond order.

A DC lamp lighting device 1 according to the present invention shown in FIG. 1 supplies DC power from an AC power source 2 to a DC lighting type high pressure discharge lamp 3.
In the high-pressure discharge lamp 3, a pair of electrodes 6A and 6B are disposed in the discharge vessel 5 of the arc tube 4 so as to face each other, and the electrode 6A serving as a cathode is connected to the tip of an electrode rod 7 made of tungsten. The coil 8 is wound with the 7 exposed for a predetermined length, the electrode 6B serving as the anode is formed of a rounded rod, and the anode side of the arc tube 4 is inserted through the neck portion 10 of the reflecting mirror 9. It is fixed.
As the high-pressure discharge lamp 3 of this example, a lamp having a rated power Pc = 100 W, a rated voltage Ec = 100 V, and a rated current Ic = 1 A was used.

  The lighting device 1 includes an AC / DC converter 12 that converts power supplied from the AC power supply 2 into direct current on a power supply circuit 11 that extends from the AC power supply 2 to the discharge lamp 3, and PWM the DC power supplied during stable lighting. A step-down chopper circuit 14 having a switching element 13 that steps down to a predetermined voltage by control, an igniter circuit 15 that applies a starting pulse at the time of starting, a current detection circuit 16 that detects a lamp operating current (lamp current), and a lamp operating voltage ( And a lamp operating power (lamp power) calculated based on the lamp current and the lamp voltage detected by the detecting circuits 16 and 17 is set to a preset rated power. Constant power control by determining the duty ratio of the PWM signal supplied to the switching element 13 so as to be maintained And a PWM control circuit 21 for performing.

In the PWM control circuit 21, the input side of the I / O port 22 is connected to the current detection circuit 16 and the voltage detection circuit 17, and the output side is connected to the switching element 13.
Then, the current priority control means 23 for maintaining the detected lamp current at a constant target current value set lower than the rated current, and the amount of power that has fallen due to the current reduction by the current priority control means 23 is compensated. The power priority control means 24 for maintaining the average power at the rated power, the timing control means 25 for alternately switching these control means at a preset control cycle of millisecond order, the current priority control means 23 and the power priority A PWM signal generator 26 for generating a PWM signal corresponding to the duty ratio determined by the control means 24 is provided.

The current priority control unit 23, sets the rated current Ic (= 1A) of the lower fixed target current value Id (e.g. 0.8 A), the detected instantaneous lamp current I _L of the target current value by the current detection circuit 16 compared to id, by determining the duty ratio of the PWM signal based on the difference, so as to maintain the lamp current I _L to the target current value id.
The target current value Id preferably satisfies the formula (1).
0.45 Ic ≦ Id ≦ 0.9 Ic (1)
This is because if the target current value Id is less than 0.45 Ic, the discharge may become unstable and extinguishment may occur. If the target current value Id exceeds 0.9 Ic, the effect of suppressing the coil temperature increase due to the current drop cannot be obtained.
Also, the target current value Id satisfies the condition of formula (1), and, when lit to maintain the rated power Pc, the discharge lamp 3 to the lamp voltage E _L is increased in accordance with the accumulated lighting time it is desirable to set below the lamp current I _L at the end of life.

In the power priority control means 24, the integrated power amount when the rated power Pc is continuously supplied during the control cycle of one cycle is set as the target integrated power amount Wc, and the current priority control means 23 reduces the current. The target power Pf is set based on the shortage of power due to this.
Then, the instantaneous lamp power P _L = I _L × E _L is calculated from the product of the instantaneous lamp current I _L and the instantaneous lamp voltage E _L detected by the current detection circuit 16 and the voltage detection circuit 17, and one cycle control is performed. The accumulated power amount Ws until the start or end of the cycle is stored each time.
Duty ratio of the PWM signal, the instantaneous lamp power P _L that has been calculated is compared with the target power Pf, and determines on the basis of the difference, when the instantaneous lamp power P _L reaches the target power Pf is integral power consumption The target power Pf is corrected each time so that Ws matches the target integrated power amount Wc.

In the timing control means 25, one continuous control time (current control time) Td by the current priority control means 23 and one continuous control time (power control time) Tp by the power priority control means 24 are set. One cycle of the control period Ts is defined by Td + Tp (see FIG. 5B).
At this time, it is preferable that these control times satisfy the expressions (2) and (3).
1 ≦ Ts ≦ 10 (msec) (2)
0.1 ≦ Td / Ts <0.5 (3)
This is because if the control period Ts is less than 1 msec, the effect of suppressing the coil temperature increase due to the current drop cannot be obtained, and if it exceeds 10 msec, the flickering feeling increases, which is not practically preferable.
Further, if Td / Ts is less than 0.1, the lamp current cannot be reduced due to the problem of response speed when the control cycle Ts is at the lower limit value. Therefore, the temperature rise suppression effect cannot be obtained, and if it exceeds 0.5, This is because when Ts is the upper limit value, the temperature at the tip of the electrode is too low and the discharge becomes unstable.

In the graph of FIG. 3, the horizontal axis indicates the control cycle Ts, and the vertical axis indicates the current control time Td.
The graph shows the conditions of the equations (2) and (3), and the hatched portion surrounded by four lines of Ts = 1, Td = 0.5Ts, Ts = 10, Td = 0.1Ts is represented by the equation (2). ) And (3) satisfying the conditions (boundary conditions are in accordance with equations (2) and (3)).
Then, the experiment was performed by changing the target current value Id within the range of the condition of the expression (1) and changing the control cycle Ts and the constant current control time Td under the conditions of the expressions (2) and (3). In this way, it was possible to improve the life characteristics by effectively suppressing the evaporation wear due to the temperature rise of the electrode member without becoming unstable, disappearing, or causing flickering.

  Here, the reason why the evaporation wear of the coil wire wound around the electrode shaft can be suppressed is presumed as follows. In the current priority control and the power priority control of the DC lamp lighting device according to the present invention, the contact area between the cathode tip and the discharge arc is relatively reduced during the current priority control (low current period), and the power priority control. Sometimes the contact area increases with increasing current. By alternately switching these two types of control at a control cycle of the order of milliseconds, the contact area between the cathode tip and the discharge arc substantially increases and decreases accordingly. Therefore, it is considered that the way of heat transfer to the coil body wound away from the tip of the cathode is suppressed as compared with the case where the light is turned on by normal constant power control.

FIG. 4 is a flowchart showing a control procedure in the PWM control circuit 21.
When a switch (not shown) is turned on, a starting pulse is issued from the igniter circuit 15 and the high pressure discharge lamp 3 is turned on, the processing is started.
First, measuring time _{t n} from the control start by starting the timer in step STP1, it detects the lamp current _{I L} and the lamp voltage _{E L} from the current detection circuit 16 and the voltage detection circuit 17 at step STP2, at step STP3 The lamp power P _L = I _L × E _L is calculated, and in step STP4, the integrated power amount Wn at the time t _n from the start of the control cycle Ts of one cycle to the present time is calculated and stored in a predetermined storage area. .
The amount of power ΔW at time ΔT is
ΔW = lamp power P _L × data detection time ΔT
Therefore, the integrated power amount Wn is
Wn = Σ (P _L × ΔT)
It can be calculated by

Next, in step STP5, it is determined whether to perform current priority control or power priority control. This determination is made based on whether or not time t _n <Td.
If time t _n <Td, the process proceeds to step STP6 in order to perform the current priority control, the preset target current value Id is read from the predetermined storage area, the process proceeds to step STP7, and is detected. compares the instantaneous lamp current _{I L} and the target current value _Id, and maintain the duty ratio of the current PWM signal goes to step STP8 if I L = Id, proceeds to step STP9 if _{I L} ≠ Id The duty ratio of the PWM signal is increased or decreased according to the difference.

In the PWM control, the PWM control circuit 21 controls the on / off time of the switching element 13 so as to keep the lamp current at a predetermined value.
Generally the discharge lamp having a negative characteristic, in order to reduce the lamp current I _L, a high duty ratio of the PWM signal, that it is necessary to lengthen the ON time.
Therefore, when the lamp current is decreased in step STP9, the duty ratio of the PWM signal is adjusted to be increased according to the difference from the target current value Id, and when the lamp current is increased, the duty ratio is decreased. adjust.

  In step STP10, the PWM signal having the duty ratio set in steps STP8 and STP9 is output to the switching element 13, and the process returns to step STP1.

If it is determined in step STP5 that time t _n ≧ Td, the process proceeds to step STP11 to perform power priority control, and the target lamp power Pf is calculated as follows (see FIG. 5D).
Assuming that the elapsed time from the start of the control cycle Ts of one cycle is t _n , the integrated power amount Wc when assuming that the rated power Pc is supplied is
Wc = Pc × t _n
Since the accumulated power amount Wn so far is calculated in step STP3, the insufficient power amount Wx is
Wx = Wc−Wn = Pc × t _n −Wn
It is represented by Since it is sufficient to add this insufficient power amount Wx with the remaining time of the control cycle Ts of one cycle, the added power amount ΔPn is
ΔPn = Wx / (Ts−t _n )
And the target lamp power Pf is
Pf = Pc + ΔPn
= Pc + (Pc × t _n −Wn) / (Ts−t _n )
It can be calculated by

Next, in step STP12, the lamp power P _L is compared with the target lamp power Pf. If P _L = Pf, the process proceeds to step STP13 to maintain the duty ratio of the current PWM signal, and if P _L ≠ Pf. The process proceeds to step STP14, and the duty ratio of the PWM signal is increased or decreased according to the difference.

When the lamp power is increased in step STP14, the duty ratio of the PWM signal is decreased in accordance with the difference from the target power Pf, and thereby, the control is performed so as to decrease until it matches when the difference from the target power Pf decreases. If the difference from the target power Pf increases due to a decrease in the duty ratio, control is performed to increase the duty ratio.
Conversely, when reducing the lamp power, the duty ratio of the PWM signal is increased in accordance with the difference from the target power Pf, and as a result, if the difference from the target power Pf becomes smaller, control is performed to increase it until it matches. If the difference from the target power Pf increases due to the increase of the duty ratio, the duty ratio may be decreased.
The lamp power is calculated by multiplying the lamp voltage value by the lamp current value.

Next, in step STP15, the PWM signal having the duty ratio set in steps STP13 and STP14 is output to the switching element 13.
In step STP16, it is determined whether or not to continue power priority control at time t _n <Ts. If t _n <Ts, the process returns to step STP2 to continue power priority control, and if t _n ≧ Ts. Is reset to time t _n = 0 at step STP17 to restart the power priority control and execute the current priority control, and then returns to step STP2.

  Here, steps STP6 to 10 are processing in the current priority control means 23, steps STP11 to 15 are processing in the power priority control means 24, and steps STP5 and S16 are processing in the timing control means 25.

The above is an example of the configuration of the present invention. Next, its operation will be described with reference to FIGS.
5A shows the PWM signal, FIG. 5B shows the lamp current I _L , (c) shows the lamp voltage E _L , and (d) shows the lamp power P _L.
When the time t _n is less than Td, the current priority control is executed, the PWM control so detected lamp current I _L is decreased to the target current value Id (0.8 A) is carried out.
When decreasing the lamp current, the duty ratio of the PWM signal is adjusted to be higher according to the difference from the target current value Id.

For example, when the duty ratio d ₁ / d ₀ = 50% of the PWM signal when supplying the rated voltage Ec (100 V) and the rated current (1 A), the duty ratio is changed to change the lamp current _IL to the target current. when reduced to a value Id (0.8 a), while monitoring the lamp current _{I L,} in accordance with the difference between the target current value Id, the higher the duty ratio of the PWM signal is, for example as _d 1 _{/ d} 0 = 60% Is set as follows.
In this case, the lamp voltage E _L is higher than the rated voltage Ec as shown in FIG. 5 (c), the lamp power P _L was lower than the rated power Pc as shown in FIG. 5 (d).
Therefore, since the power is kept low while the current priority control is being performed, in order to achieve constant power control within one cycle of control, it is necessary to compensate for the shortage in the power priority control.

When the time t _n reaches Td, the power priority control is executed, PWM control is performed so calculated lamp power P _L is increased to the target lamp power Pf.
Target lamp power Pf based from the start of the control cycle of one cycle shortage Wx of electric energy up to time t _n is calculated (step STP11), the duty ratio is determined to be the lamp power P _{L =} Pf.
In order to increase the lamp power P _L, it is necessary to increase the product of lamp voltage E _L and the lamp current I _L, while calculating the product by monitoring the lamp voltage E _L and the lamp current I _L, the target Depending on the difference from the current value Id, the duty ratio of the PWM signal is set to be as low as, for example, d ₁ / d ₀ = 40%.

FIG. 6 shows the average lamp power, average lamp voltage, and average lamp current as the cumulative lighting time increases.
The discharge lamp 3 has a tendency that the distance between the electrodes becomes longer and the lamp voltage increases due to the evaporation wear at the tips of the electrodes 6A and 6B as the cumulative lighting time increases.
In the present example, a constant power control as shown in FIG. 6 (a) being carried out, the average lamp voltage E _AV with an increase in the cumulative lighting time, as shown in FIG. 6 (b) gradually increases Although it depends on the type of lamp, it tends to increase by about 10% until the end of its life.
Accordingly, as shown in FIG. 6C, the average lamp current I _AV is approximately the same as the rated current Ic at the beginning of lighting, and gradually decreases as the cumulative lighting time increases, and is about 10 at the end of life. However, as the average lamp current I _AV decreases, the heating of the electrode member is suppressed and the adverse effect of evaporation wear is also reduced.

In this case, in the current priority control according to the present invention, rather than a specific target current value Id is for the lamp current I _L, which is set by the ratio of the rated current Ic is designed value in the initial lighting, for example, the rated current When Ic = 1A, the target current Id = 0.85A is set.
Initial lighting of the average lamp current I _AV is comparable to the rated current Ic, when reduced to 0.9A gradually decreased until the end of life, in the initial lighting, the average lamp current I _AV and the target current larger the difference ΔI ₌ I AV -Id ₌ 0.15A with id, high temperature suppressing effect of current reduction.
On the other hand, when the average lamp current I _AV approaching the end of life comes to decrease not only the heating of the electrode tip is also reduced adverse effects of evaporation wear is suppressed, along with this, the difference between the target current Id ΔI = I AV _-Id be reduced, temperature suppression effect due to lower current is gradually being alleviated automatically.
Accordingly, as the degree of evaporation wear of the electrode member decreases, the heating suppression effect accompanying the decrease in lamp current during current priority control is also automatically mitigated, and the electrode tip is overcooled and discharge occurs. There is no instability.
Further, the power supply by the current priority control means 23 and the power supply by the power priority control means 24 are alternately executed with a cycle of millisecond order (up to 10 msec), and the cycle is sufficiently smaller than the time resolution of human vision. No flickering due to current fluctuations.

Further, as shown in FIG. 7, the light source device 31 incorporating the lighting device 1 is provided with a light emission port 34 to which the lamp unit 32 having the high-pressure discharge lamp 3 mounted on the elliptical reflecting mirror 9 connects the ride guide 33. It is installed in a housing case 35.
In the discharge lamp 3, the center (light emitting point) of the discharge vessel 5 of the arc tube 4 is arranged at the primary focal position of the elliptical reflecting mirror 9, and the light condensed at the secondary focal point is connected to the light exit port 34. The light guide 33 is guided.
A filter 36 such as a wavelength selection filter and / or a neutral density filter is interposed in the vicinity of the secondary focal point located between the light exit 34 and the lamp unit 32.

First, a high-pressure discharge lamp 3 having a rated lamp power Pc = 100 W, a rated lamp voltage Ec = 60 V, a rated lamp current 1.67 A, and an exposed portion length D = 0.5 mm of the electrode rod 7 is connected to the lighting device 1, and The target current value Id at the time of priority control is set to 0.8A, the control cycle of one cycle Ts = 5 msec, the current control time Td = 1 msec, and Td / Ts = 0.2. When the maximum temperature of the coil 8 wound around the tip end of the wire was measured, it was 2000 ° C.
Next, even when the discharge lamp 3 was mounted on the reflecting mirror 9 and incorporated in the light source device 31 to be lit, the coil 8 was not heated to such an extent that the coil 8 was significantly worn over the lifetime (3000 hours).

For comparison, under the same conditions, without the current priority control, when the lamp power P _L is subjected to the conventional constant power control is maintained at the rated power Pc, the maximum temperature of the coil 8 is met 2200 ° C. It was.
That is, according to the lighting device 1 according to the present invention, the temperature difference of the maximum temperature of the coil 8 is as much as 200 ° C. compared with the case where the conventional constant power control is performed, and the coil 8 is wound around the electrode shaft accordingly. The temperature rise of the coil could be suppressed.
Next, when this discharge lamp 3 is mounted on the reflecting mirror 9 and incorporated in the light source device 31 and turned on by the conventional constant power control, the coil 8 is heated to cause evaporation wear and a part thereof is missing. Was found.

  When used as the light source device 31, the reflecting mirror 9 is not limited to an elliptical reflecting mirror, but a parabolic reflecting mirror (not shown) that reflects light emitted from the light emitting point of the high-pressure discharge lamp 3 into parallel light. And a lens system (not shown) for condensing the parallel light may be disposed in front of the reflecting mirror.

  INDUSTRIAL APPLICABILITY According to the present invention, the present invention can be applied to the use of a DC lamp lighting device for lighting a DC lighting type high-pressure discharge lamp in which a pair of electrodes are disposed facing each other in a discharge vessel of an arc tube.

DESCRIPTION OF SYMBOLS 1 DC lamp lighting device 2 AC power supply 3 High pressure discharge lamp 4 Arc tube 5 Discharge vessel 6A, 6B Electrode 7 Electrode rod 8 Coil 9 Reflecting mirror 13 Switching element 14 Step-down chopper circuit 15 Igniter circuit 21 PWM control circuit 23 Current priority control means 24 Power priority control means 25 Timing control means 26 PWM signal generator

Claims (7)

A step-down chopper circuit having a switching element that adjusts DC power supplied during stable lighting by PWM control for a DC lighting type high-pressure discharge lamp in which a pair of electrodes are arranged to face each other in a discharge vessel of an arc tube, Constant power control is performed by determining the duty ratio of the PWM signal supplied to the switching element so that the lamp operating power calculated based on the lamp operating current and the lamp operating voltage is maintained at a preset rated power. In a DC lamp lighting device provided with a PWM control circuit,
The PWM control circuit compensates for the electric power that has fallen due to the current priority control means for maintaining the lamp operating current at a constant target current value set lower than the rated current and the current priority control means. A DC lamp lighting device comprising: power priority control means for maintaining average power at rated power; and timing control means for alternately switching each of the control means at a preset control cycle in the order of milliseconds. . When Tp is one continuous control time by the power priority control means, and Ts is one cycle control time defined by one continuous control time Td and Tp + Td by the current priority control means,
1 ≦ Ts ≦ 10 (msec)
0.1 ≦ Td / Ts <0.5
The direct-current lamp lighting device according to claim 1.   3. The DC lamp lighting device according to claim 1, wherein a target current value at which the lamp operating current is maintained by the current priority control means is set to be lower than a rated current and equal to or less than a lamp current value at the end of life. When the target current value at which the lamp operating current is maintained by the current priority control means is Id, and the rated current that is the design value of the lamp is Ic,
0.45 Ic ≦ Id ≦ 0.9 Ic
The DC lamp lighting device according to any one of claims 1 to 3.   A light source is a DC lighting type high-pressure discharge lamp in which a pair of electrodes are arranged opposite to each other in a discharge vessel, and a coil is wound with the electrode rod exposed for a predetermined length on the tip side of the electrode rod serving as a cathode. A light source device comprising the DC lamp lighting device according to claim 1.   6. The light source according to claim 5, wherein the high-pressure discharge lamp is attached with an elliptical reflecting mirror that places a light emitting point of the lamp at a primary focal position and collects light emitted from the light emitting point at a secondary focal point. apparatus.   A parabolic reflector that reflects the light emitted from the light emitting point of the lamp to parallel light is attached to the high-pressure discharge lamp, and a lens system that condenses the parallel light in front of the reflector The light source device according to claim 5, wherein the light source device is disposed.

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