JP2008041588A - High-pressure discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively prevent shortening of arc length, due to growth of an electrode at lighting a high-pressure discharge lamp and prevent degradation of lamp voltage caused by this. <P>SOLUTION: The high-pressure discharge lamp lighting device consists of a power supply means inputting DC or AC power to a high-pressure discharge lamp for making the high-pressure discharge lamp started, and a control means controlling output of a power supply circuit, by detecting the lamp voltage of the high-pressure discharge lamp. When the lamp voltage is higher than a first voltage at the prescribed time passing from start, the control means selects a first control, following the first output characteristic regulating lamp current or lamp power to the lamp voltage; and when the lamp voltage to be less than the first voltage at the prescribed time passing from the start, the control means selects a second control, following a second output characteristic regulating the lamp current or the lamp power to the lamp voltage, until the lamp voltage becomes larger than a second voltage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high pressure discharge lamp lighting device for lighting a high pressure discharge lamp used in a projector or the like.

In recent years, in the case of a high-pressure discharge lamp used for a projector or the like, in order to improve the optical characteristics, shortening of arc (reducing the distance between electrodes) is progressing year by year.
However, in such a short arc type high pressure discharge lamp, since a large lamp current flows until the lamp voltage shifts to a stable state, the tip of the electrode is overheated at a high temperature, and tungsten constituting the electrode evaporates, and the arc length is increased. Is a long life before the lamp voltage becomes stable, causing a short life. In order to avoid such a situation, the lamp voltage is stabilized while the lamp current until the lamp voltage shifts to a stable state is controlled by the control circuit of the step-down chopper circuit section with a constant current control or a lower current. And the tip of the electrode is heated at a relatively low temperature to minimize tungsten evaporation, and the rated lamp power can be output while suppressing the increase in arc length.

By the way, Patent Document 1 discloses that the electrode grows in a protruding shape depending on the lighting frequency or the like even when the high pressure discharge lamp is in the rectangular wave lighting.
The phenomenon that the electrode grows in a protruding shape is not necessarily clear, but is estimated as follows.
When the heated tungsten is evaporated, it is combined with halogen or the like present in the arc tube to form a tungsten compound. This tungsten compound diffuses from the vicinity of the tube wall to the vicinity of the tip of the electrode by convection or the like, and is decomposed into tungsten atoms at a high temperature portion. Tungsten atoms become cations when ionized in the arc. Both electrodes that are lit with alternating current repeat the anode and cathode at each lighting frequency, but when this cathode is operating, the cations in the arc are attracted to the cathode side by the electric field and deposited at the tips of both electrodes, It is believed that it forms a protrusion.
Note that Patent Document 1 discloses a configuration in which a steady frequency and a low frequency are modulated with respect to a lighting frequency in order to form a protrusion.

  Thus, although the electrode grows in a protruding shape, the arc length is shortened and the lamp voltage is gradually lowered by the growth. And when the lamp voltage is lower than the rated lamp voltage, it is controlled with constant current control or lower current, so tungsten hardly evaporates and it lights up with no rated power output, that is, the illuminance is low. A function to stop the circuit operation when the lamp voltage falls below a certain lamp voltage by turning on the lamp, detecting the lamp voltage with a resistance voltage divider, etc., and inputting the divided lamp voltage to a microcomputer (not shown) (Hereinafter referred to as “low lamp voltage protection / operation stop function”) has been a problem.

Patent Documents 2 and 3 disclose lighting methods in consideration of suppressing the growth of the electrodes.
In Patent Document 2, for the purpose of suppressing electrode growth and repairing the electrode surface, a period for lowering the lighting frequency than usual (for example, a period of a lighting frequency of 5 Hz) is provided, or the lamp current is set from the rated value during stable lighting. In other words, a configuration is disclosed in which a period of time (1 second or more, usually about 10 seconds) is provided. Specifically, the thermal concentration at the electrode portion is increased by the low frequency period to melt the protrusions, and the electrode surface is restored by the high lamp current period. In particular, the high lamp current period is provided for stable lighting. Is preferred.

Patent Document 3 discloses a control method for the purpose of balancing the increase in arc length due to electrode wear and the decrease in arc length due to electrode growth. . In this patent document, the arc voltage (distance between electrodes) is detected by detecting the lamp voltage. If the arc length increases, the pulse current is superimposed on the normal lamp current to grow the electrode. The superposition of the pulse current is stopped and the electrodes are consumed, thereby maintaining the arc length within an appropriate range. The principle and idea of electrode growth and suppression are opposite to those of Patent Document 2.
JP 2006-059790 A JP 2002-175890 A JP 2004-158273 A

  However, according to the method of Patent Document 2, there is a problem that the disclosed control is not suitable for application to a light source device such as a projector before mentioning whether there is an effect of appropriately maintaining the state of the electrode surface. When the lighting is performed with an alternating current, flickering due to the polarity reversal of the lamp current becomes visible when the frequency is 50 Hz or less. Therefore, lighting at a lower frequency is appropriate for the light source device. Absent. Therefore, the lighting method of the same document that lights at a low frequency of, for example, 5 Hz during stable lighting is not suitable for the light source device. In addition, when a period for increasing the lamp current for a predetermined period (for example, 1 second) is provided during stable lighting, the light output is brightened only during that period, which gives a visually uncomfortable feeling, and is also suitable for the light source device. It's not a good lighting method.

  Further, as described in Patent Document 3, for the control to repeat the growth of the electrode by the operation of superimposing the pulse on the normal lamp current and the consumption of the electrode by the operation of stopping the pulse superposition (electrode growth) It is unclear whether the growth of the electrode can be effectively suppressed by the technique disclosed in Patent Document 3). As a result, the electrode protrusion may continue to grow in the same patent document, and in any case, it will continue to light without the rated power being output, lighting in a low illuminance state, or the low lamp voltage protection operation function will work. There was a possibility of circuit operation being stopped.

  According to a first aspect of the present invention, there is provided a power supply means for starting a high-pressure discharge lamp and supplying DC or AC power to the high-pressure discharge lamp, and detecting a lamp voltage of the high-pressure discharge lamp to output the power supply circuit. A high pressure discharge lamp lighting device comprising control means for controlling, wherein the control means defines a lamp current or a lamp power with respect to the lamp voltage when the lamp voltage is equal to or higher than the first voltage when a predetermined time has elapsed since the start. When the first control according to the first output characteristic is selected and the lamp voltage is less than the first voltage at the elapse of a predetermined time from the start, the lamp with respect to the lamp voltage is increased until the lamp voltage becomes equal to or higher than the second voltage. A high pressure discharge lamp lighting device that selects a second control according to a second output characteristic that defines a current or a lamp power.

In the first aspect, the second control is constant power control that keeps the lamp power constant at the rated power. Further, the lamp current or lamp power having the second output characteristic may be higher than the lamp current or lamp power having the first output characteristic for the same lamp voltage.
Further, the first voltage and the second voltage are made the same, and this is set as the lower limit value of the rated lamp voltage.
Further, the control means performs the first control until a predetermined time has elapsed.
Here, regarding the lamp current waveform, the presence / absence of pulse superposition and the lighting frequency may or may not be constant.

  Further, in the first aspect, when the power input to the high pressure discharge lamp is AC power, the power supply means receives the output from the DC power supply unit and limits the current supplied to the high pressure discharge lamp. And a full-bridge circuit that converts a direct current limited by the step-down chopper circuit into an alternating current and supplies the high-pressure discharge lamp to a detection circuit that detects the lamp voltage, and a transistor that forms the step-down chopper circuit The control circuit is configured to control the duty ratio.

  A second aspect of the present invention is a light source device including a high pressure discharge lamp lighting device, a casing containing the high pressure discharge lamp lighting device, a high pressure discharge lamp, and a reflector to which the high pressure discharge lamp is attached.

  According to the present invention, in addition to the configuration for preventing the electrode from being consumed, it is possible to effectively prevent the arc length from being reduced due to the growth of the electrode with a simple configuration. Therefore, the lamp voltage can be prevented from lowering due to the growth of the electrode while protecting the electrode, and the influence on the illuminance reduction can be effectively prevented.

  FIG. 1 is a circuit diagram of a high pressure discharge lamp lighting device according to the present invention. In the following description, the current, voltage, and power supplied to the high-pressure discharge lamp 60 (hereinafter referred to as “lamp 60”) are referred to as lamp current, lamp voltage, and lamp power, respectively. The high pressure discharge lamp lighting device shown in FIG. 1 includes a circuit that constitutes a power supply unit including a DC power source 10, a step-down chopper circuit 20, a full bridge circuit 40, and an igniter circuit 50, and a circuit that constitutes a control unit including a control circuit 30. Become.

More specifically, the output current of the DC power supply 10 is limited by the step-down chopper circuit 20 and input to the full bridge circuit 40. This restriction is performed by on-duty control of the switching transistor 21 of the step-down chopper circuit 20 by the PWM control circuit 33. Specifically, in the control circuit 30, the output voltage (lamp voltage) of the step-down chopper circuit 20 is detected by the resistors 31a and 31b, the output current (lamp current) is detected by the resistor 32, and a microcomputer is mounted. Input to the PWM control circuit 33. The lamp power is calculated by multiplying the lamp voltage and the lamp current in the PWM control circuit 33.
The PWM control circuit 33 controls the on-duty of the transistor 21 based on the lamp voltage and the lamp current or the lamp power. That is, in this embodiment, the PWM control circuit 33 serves as a processor and a driver. Of course, they may be configured independently.

  In the full bridge circuit 40, the transistors 41 and 44 and the transistors 42 and 43 are alternately turned on and off at about several hundreds Hz, so that the input direct current is converted into a rectangular wave alternating current of that frequency to generate a high voltage. It is inserted into the discharge lamp 60. Note that the igniter circuit 50 is for starting the high-pressure discharge lamp 60, and a known one may be used (the present invention relates to the operation after the start of lighting, so a detailed description of the starting igniter circuit will be given). (Omitted). Since the present invention is characterized by control of lamp power or lamp current, the circuit configuration itself may be general.

Next, control of lamp power after starting will be described.
FIG. 2 shows changes in lamp voltage after starting (after starting discharge). As shown in the figure, in a general high-pressure discharge lamp, the lamp voltage continues to be low for several tens of seconds after starting, and then the lamp voltage rises, reaching stable lighting several minutes after starting. Note that “after several minutes” depends on the type of lamp and the rated power, but is about 1.5 to 20 minutes later.

Example 1.
Under the above premise, in the first embodiment, the PWM control circuit 33 controls the lamp power according to the flowchart shown in FIG. The lamp 60 is an ultra-high pressure mercury lamp with a rated power of 275 W and an arc length of 1.2 mm.

First, power is turned on in step S1, and the lamp is started (starts discharging) in step S2. In step S3, the lamp 60 is lit by control according to the power characteristics shown in the column (1) of Table 1 (hereinafter referred to as “normal lighting control”). The time for starting the normal lighting control may be immediately after step S2 or after a predetermined period has elapsed. Although not shown in the flowchart, the detected value of the lamp voltage and the lamp current is always taken into the PWM control circuit 33, whereby the lamp power is calculated and can be used in each step. As can be seen from Table 1, in normal lighting control, constant power control is performed when the lamp voltage is 65 V or higher, and control is performed with characteristics such that when the lamp voltage decreases, the lamp current and lamp power decrease. .

  In step S4, if the elapsed time t from the start does not reach t1, the normal lighting control (step S3) is continued, and if the elapsed time t reaches t1, the process proceeds to step S5. In this example, t1 was 3 minutes. In addition, t1 should just be an appropriate time before the stable lighting transition shown in FIG.

In step S5, if the lamp voltage V _L is equal to or higher than V1, the process proceeds to step S6 and the normal lighting control is continued. If the detected lamp voltage V _L is less than V1, the process proceeds to step S7, and (2) in Table 1 The lamp 60 is turned on by switching to control according to the power characteristics shown in the column (hereinafter referred to as “low voltage control”). Here, in this embodiment, V1 is set to 65V which is the lower limit value of the rated lamp voltage. As can be seen from Table 1, in the low voltage control, constant power control is performed regardless of whether the lamp voltage is 65 V or higher or less than 65 V. The “low voltage protection / stop” in column (2) of Table 1 will be described later.

FIG. 4 is a diagram comparing the characteristics (1) and (2) in Table 1 as described above. As is apparent from the figure, assuming that the lamp current and lamp power in the normal lighting control are I ₁ and P ₁ respectively, and the lamp current and lamp power in the low voltage control are I ₂ and P ₂ , respectively, V _L ≧ At 65 V, I ₁ = I ₂ and P ₁ = P ₂ , but at 40 V <V _L <65 V, I ₁ <I ₂ , P ₁ <P ₂ , and at 40 V <V _L the entire range in a _{P 2} is constant.

In steps S7 and S5, when the lamp voltage _VL becomes equal to or higher than V1 (65V) during the low voltage control, the process proceeds to step S6 and shifts to the normal lighting control.

  Further, at the time of the control switching at t1, the transition may be made smoothly over a period of about 1 second to 10 seconds so as not to cause a step difference in luminous flux change that is visually uncomfortable. For example, when the lamp voltage V is 50 V at the time t1, the lamp current is 3.8 A since the normal lighting control was performed before t1, and the current is 3.8 A from 5.5 A in the low voltage control. In the case of shifting to, the purpose is that 3.8A to 5.5A may be changed over about 1 to 10 seconds.

  In the event that there is an abnormality in the lamp or the like, the circuit operation is stopped when the lamp voltage is 40 V or less after the elapse of a predetermined period after power-on (after 4 minutes in this embodiment). A protection function may be added. The column (2) in Table 1 reflects the protection function. Of course, the protection function may be applied in the normal lighting control of (1).

Table 2 shows the lamp A that is lit using only the normal lighting control of Table 1 (1) and the normal lighting control and low voltage control of Tables 1 (1) and (2) as shown in FIG. The change in lamp voltage with respect to the cumulative lighting time is compared for the lamp B that is turned on using a simple flow. The lamp is the above-described ultra-high pressure mercury lamp with a rated power of 275 W and a high-pressure discharge lamp with an arc length of 1.2 mm, and the supplied lamp current is a rectangular wave.

  As can be seen from Table 2, the difference in lamp voltage becomes significant when the cumulative lighting time exceeds 300 hours. When the cumulative lighting time is 600 hours, the lamp voltage of the lamp A has decreased by about 35%, while the lamp B to which the present invention is applied has an increase of about 10%. This is a level at which there is no problem in using the lamp. Since the lamp voltage is almost proportional to the distance between the electrodes, the same comparison / consideration holds for the growth of the electrodes. That is, the electrode is not grown.

  In addition, a present Example is an example for implement | achieving the basic concept of this invention. The basic concept is summarized here: “For lamps that do not reach the lamp voltage that should be reached by a predetermined time after the start of lamp start-up, ie for lamps with electrodes growing, a relatively early period after start-up. In addition, a higher power than the normal control for a lamp with no electrode grown is performed, which prevents or reverses the electrode growth and prevents the arc length from being reduced. " Is.

Example 2
In the first embodiment, the switching determination of each control is shown for a single voltage (V1). However, in this embodiment, the voltage for determining the transition from the normal lighting control to the low voltage control is reduced. A voltage different from the voltage for determining the transition from the on-voltage control to the normal lighting control is shown.
As shown in FIG. 3B, in step S5, the voltage for determining switching from the normal lighting control to the low voltage control is set to V1, and in step 8, the switching determination from the low voltage control to the normal lighting control is performed. The voltage may be given as V2 and hysteresis may be given as V1 <V2. As described above, when the lamp voltage V ≧ 65V, the output is the same in both the normal lighting control and the low voltage control, but due to this hysteresis, the lamp 60 that was initially in the low voltage state was turned on by the low voltage control. Then, after the state where the normal lighting can be performed is surely established, it is possible to return to the normal lighting control.

  On the other hand, in FIG. 3B, it may be possible to shift from the low voltage control to the normal lighting control as early as V1> V2. In this case, it is inferior to the case of V1 ≦ V2 from the viewpoint of suppressing the growth of the electrode, but conversely, the effect of the present invention can be obtained while further ensuring the effect of suppressing the consumption of the electrode.

  Further, the value of V1 or V2 may be variable according to the state of the lamp. For example, if the lamp voltage tends to decrease in the process of accumulating lamp lighting, the "growth" is more advanced than the "consumption" of the electrode, so the low voltage has the effect of suppressing electrode growth. In order to increase the effectiveness of the time control, V1 may be decreased (before) or V2 may be increased (before). If it does so, it will become easy to transfer to the control at the time of low voltage at the time of t1, and even if it transfers, it will become difficult to return to normal lighting control, and the opportunity of the control at the time of low voltage will increase.

  Conversely, if the lamp voltage tends to increase in the process of accumulating lamp lighting, it means that “consumption” is more advanced than “growth” of the electrode. In order to loosen the effect, V1 may be increased (before) or V2 may be decreased (before). If it does so, it will become difficult to transfer to low voltage control at the time of t1, or it will become easy to return to normal lighting control even if it transfers, and the opportunity of low voltage control will decrease.

Example 3
In the first and second embodiments, a high pressure discharge lamp lighting device that preferably prevents a decrease in arc length is shown. In this embodiment, a light source device using the high pressure discharge lamp lighting device is shown.
FIG. 5 is a diagram showing a light source device according to the third embodiment. In the figure, 71 is the high pressure discharge lamp lighting device described above, 72 is a reflector to which the high pressure discharge lamp 60 is attached, and 73 is a housing containing the high pressure discharge lamp lighting device 71, the high pressure discharge lamp 60 and the reflector 72 as necessary. Is the body. In addition, the figure is a schematic illustration of the embodiment, and the dimensions, arrangement, and the like are not as illustrated. In addition, a projector can be configured by appropriately arranging a video system member or the like (not shown) in the housing 73.

  As described above, since the high-pressure discharge lamp lighting device that can reliably prevent the arc length from decreasing as shown in the first and second embodiments is incorporated, a light source device having improved optical characteristics can be obtained.

The above embodiment is shown as the most preferable example of the present invention, but can be modified as follows, for example, without departing from the spirit of the present invention.
(1) In Examples 1 and 2, the lamp current is a rectangular wave alternating current, but the lamp current may be a direct current, sine wave, triangular wave, other waveform, or a combination thereof, or a low frequency, high frequency, The principle of the present invention can be applied to a regular wave or a combination thereof. This is because the effect of the present invention can be obtained if the effective value of the lamp power in a relatively long period (several seconds to several minutes) can be controlled. In addition, a known circuit configuration may be used as a circuit configuration for realizing the above modification.

  (2) In Examples 1 and 2, constant power control is used as low voltage control. However, if a corresponding lamp power (higher lamp power than normal lighting control) can be input at low voltage, control other than constant power control is possible. Even if a method (for example, constant current control, control according to a predetermined table, etc.) is used, a corresponding effect can be obtained.

  (3) In the first and second embodiments, the normal lighting control is used for the control before t1, but other control (that is, a dedicated control before reaching stable lighting) may be used.

  The utilization of the present invention is mainly used in light source devices such as projectors, projection TVs, and projectors.

The figure which shows the circuit structure of the high pressure discharge lamp lighting device of this invention Diagram showing the behavior of the lamp voltage of a general high-pressure discharge lamp Flowchart showing the control of the present invention The figure which shows the lamp power characteristic of this invention The figure which shows the light source device of this invention

Explanation of symbols

10: DC power supply 11: AC power supply 12: Full-wave rectifier circuit 13: Capacitor 20: Step-down chopper circuit 21: Transistor 22: Diode 23: Choke coil 24: Capacitor 30: Control circuits 31a, 31b, 32: Resistor 33: PWM control Circuit 40: Full bridge circuit 41, 42, 43, 44: Transistor 50: Igniter circuit 60: High pressure discharge lamp 71. High pressure discharge lamp lighting device 72. Reflector 73. Enclosure

Claims (7)

Power supply means for starting a high pressure discharge lamp and supplying DC or AC power to the high pressure discharge lamp, and control means for detecting the lamp voltage of the high pressure discharge lamp and controlling the output of the power supply circuit A high pressure discharge lamp lighting device,
The control means is
When the lamp voltage is equal to or higher than the first voltage after a predetermined time has elapsed from the start, the first control according to the first output characteristic defining the lamp current or the lamp power with respect to the lamp voltage is selected,
When the lamp voltage is less than the first voltage when a predetermined time has elapsed from the start, a second output characteristic defining a lamp current or a lamp power with respect to the lamp voltage until the lamp voltage becomes equal to or higher than the second voltage. The high pressure discharge lamp lighting device, wherein the second control according to the above is selected.   2. The high pressure discharge lamp lighting device according to claim 1, wherein the second control is a constant power control for keeping the lamp power constant at the rated power.   2. The high pressure discharge lamp lighting device according to claim 1, wherein a lamp current or lamp power of the second output characteristic is higher than a lamp current or lamp power of the first output characteristic for the same lamp voltage. High pressure discharge lamp lighting device.   The high pressure discharge lamp lighting device according to any one of claims 1 to 3, wherein the first voltage and the second voltage are the same and both are lower limit values of a rated lamp voltage. apparatus.   5. The high pressure discharge lamp lighting device according to claim 1, wherein the control unit performs the first control until the predetermined time has elapsed. 6. In the high pressure discharge lamp lighting device according to any one of claims 1 to 5, the electric power supplied to the high pressure discharge lamp is alternating current power,
The power supply means receives the output from the DC power supply unit and limits the current supplied to the high-pressure discharge lamp, and converts the DC current limited by the step-down chopper circuit into an AC current, and converts the DC current to the high-pressure discharge lamp. It consists of a full bridge circuit that supplies
The high-pressure discharge lamp lighting device, wherein the control means includes a detection circuit for detecting a lamp voltage and a control circuit for controlling a duty ratio of a transistor constituting the step-down chopper circuit. A light source device comprising the high-pressure discharge lamp lighting device according to any one of claims 1 to 6, a casing containing the high-pressure discharge lamp lighting device, a high-pressure discharge lamp, and a reflector to which the high-pressure discharge lamp is attached.

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