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EP1280387A2 - Electronic circuit for operating an HID lamp and an associated image projecting apparatus - Google Patents

Electronic circuit for operating an HID lamp and an associated image projecting apparatus Download PDF

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Publication number
EP1280387A2
EP1280387A2 EP02016738A EP02016738A EP1280387A2 EP 1280387 A2 EP1280387 A2 EP 1280387A2 EP 02016738 A EP02016738 A EP 02016738A EP 02016738 A EP02016738 A EP 02016738A EP 1280387 A2 EP1280387 A2 EP 1280387A2
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EP
European Patent Office
Prior art keywords
lamp
electronic circuit
hid lamp
brightness
sensor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP02016738A
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German (de)
French (fr)
Other versions
EP1280387B1 (en
EP1280387A3 (en
Inventor
Peter Dr. Philips Corp. Int. Prop. GmbH Lürkens
Carsten Philips Corp. Inte. Prop. GmbH Deppe
Holger Dr. Philips Corp. Inte. Prop. GmbH Mönch
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Philips Intellectual Property and Standards GmbH
Koninklijke Philips NV
Original Assignee
Philips Intellectual Property and Standards GmbH
Philips Corporate Intellectual Property GmbH
Koninklijke Philips Electronics NV
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Publication of EP1280387A2 publication Critical patent/EP1280387A2/en
Publication of EP1280387A3 publication Critical patent/EP1280387A3/en
Application granted granted Critical
Publication of EP1280387B1 publication Critical patent/EP1280387B1/en
Anticipated expiration legal-status Critical
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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/16—Circuit arrangements in which the lamp is fed by DC or by low-frequency AC, e.g. by 50 cycles/sec AC, or with network frequencies
    • H05B41/20—Circuit arrangements in which the lamp is fed by DC or by low-frequency AC, e.g. by 50 cycles/sec AC, or with network frequencies having no starting switch
    • H05B41/23—Circuit arrangements in which the lamp is fed by DC or by low-frequency AC, e.g. by 50 cycles/sec AC, or with network frequencies having no starting switch for lamps not having an auxiliary starting electrode
    • H05B41/231—Circuit arrangements in which the lamp is fed by DC or by low-frequency AC, e.g. by 50 cycles/sec AC, or with network frequencies having no starting switch for lamps not having an auxiliary starting electrode for high-pressure lamps
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • H05B41/38—Controlling the intensity of light
    • H05B41/39—Controlling the intensity of light continuously
    • H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/20—Responsive to malfunctions or to light source life; for protection

Definitions

  • the invention relates to an electronic circuit for operating a high-intensity discharge HID lamp, in particular an ultra-high-pressure UHP lamp according to the preamble of patent claim 1.
  • the invention further relates to an image projector with the electronic circuit according to claim 1.
  • HID and UHP lamps are generally known in the prior art. They are preferably used for projection purposes, but also e.g. used to operate car headlights. They are characterized by a very small arc and a high luminous efficacy, which advantageously leads to a very good overall efficiency. The brightness of these lamps is about two to four times that of other gas discharge lamps.
  • HID lamps have the effect of archery, i.e. a change in the position of the arc while these lamps are operating.
  • the change in the arc position changes the proportion of the light generated by the lamp as a whole, which reaches the imaging system, so that the brightness of the projected image fluctuates.
  • This effect also leads to undesirable fluctuations in the brightness distribution on the image generator.
  • a flicker effect is perceptible to the viewer.
  • a first approach provides for an additional high current pulse in the course of the lamp current before it is commutated. Due to this special form of lamp current, archery and thus the flicker effect can be effectively suppressed.
  • the provision of the high current pulse has the disadvantage, on the one hand, that the lamp driver becomes larger and more expensive than with a different lamp current, and, on the other hand, that the service life of the HID lamp is significantly reduced.
  • JP-2000028988 A discloses an LCD projector with an optical system 420 and an electrical circuit.
  • the optical system 420 comprises a gas discharge lamp 422 with a reflector 421 and, downstream of the lamp, an integrator 423, an image generator 424 and an objective 425b.
  • the integrator 423 together with a condenser 425a ensures a uniform brightness distribution when illuminating the image generator 424 and thus in the image generated by the image generator.
  • the electrical circuit is used to operate the lamp 422. It comprises a lamp driver 410 for providing a regulated lamp current for the lamp 422 in response to a control signal and a brightness sensor 430 for generating and outputting a sensor signal.
  • the sensor signal represents the amount of light emitted by the lamp at the location of the brightness sensor.
  • the quantity of light represented by the sensor signal is compared in a microprocessor 440 with a predetermined reference quantity of light, in order then to generate the control signal in accordance with the measured quantity of light deviation and to output it to the lamp driver. In this way, the amount of light emitted is adjusted to the reference value. A flicker effect can be prevented if the light quantity control is done quickly enough.
  • this second approach has the following disadvantages: Due to the fact that the lamp is operated with a lower than the nominal power from the outset, the brightness generated is significantly lower than at nominal power, i.e. such a projector system requires a larger lamp to generate the same brightness from the start as a system without it Type of scheme.
  • HID lamps are also characterized by a sensitive thermal equilibrium that can only be maintained sufficiently at rated power. In the event of deviations, disadvantages in the service life are to be expected, so that the regulation in the manner of JP-2000028988 A can be expected to have a shorter service life.
  • the brightness sensor in the known circuit should not only work reliably at room temperature, but also at high temperatures inside an image projector.
  • the high-pass filter filters out very low frequency components of the brightness fluctuations and in particular their direct components from the sensor signal. These frequency components are therefore also missing in the control signal and are not taken into account when regulating the HID lamp.
  • the remaining alternating components of the brightness fluctuations are regulated to zero instead of - as in the prior art - regulating the absolute brightness to a predetermined reference value.
  • this has the advantage that effects of faulty offsets or faulty sensitivities of the brightness sensor are filtered out of the sensor signal and thus have no undesired effect on the control.
  • Simple and inexpensive sensors can therefore very well be used in the implementation of the circuit claimed, without the quality of the control being adversely affected.
  • the high-pass filter advantageously enables the brightness fluctuations to be regulated by the circuit during the entire life of the HID lamp.
  • the regulation is possible according to the invention, particularly in the case of nominal power operation, both in the positive and in the negative direction.
  • a control unit within the lamp driver is also designed to control the electrical power generated at the output of the control unit in such a way that the HID lamp is constantly operated at the nominal power level in the long term.
  • this maximizes the service life of the lamp and, on the other hand, it ensures that the luminous efficacy of the lamp is at a maximum during its entire service life.
  • the object of the invention is further achieved by the subject matter of claim 7.
  • the advantages of the image projector claimed there essentially correspond to the advantages mentioned above with regard to the electronic circuit.
  • the human eye is particularly sensitive to flicker effects when displaying still images with large, monochrome areas. Suppression of this effect is therefore particularly advantageous here.
  • FIG. 1 shows an electronic circuit for operating an HID lamp, in particular a UHP lamp, according to the invention. It comprises a lamp driver 110, a brightness sensor 130 and a filter 140.
  • the lamp driver 110 is designed as a control unit and serves to provide and control a lamp current for the operation of the HID lamp 322 in response to a control signal, so that the amount of light emitted by the HID lamp at the location of the brightness sensor 130 is constant in the medium term.
  • the sensor signal generated by the brightness sensor 130 in FIG. 1 represents the amount of light emitted by the HID lamp at the location of the brightness sensor 130.
  • Filtering in a filter 140 converts the sensor signal into the control signal.
  • the filter 140 is preferably designed as a high-pass filter, so that in particular the direct component is filtered out of the sensor signal and thus also from the control signal.
  • this has the advantage that certain measurement errors of the brightness sensor 130 do not have a negative effect on the result of the control.
  • the control signal which is high-pass filtered according to the invention only represents the alternating component in the original sensor signal, ie only the actual brightness fluctuations.
  • the brightness fluctuations can be caused, for example, by the arc jumping described above or by a transition of the lamp from a diffuse arc state to a concentrated arc state (spot mode).
  • the primary aim of the control by the lamp driver 110 is to generate a stabilized brightness without rapid fluctuations, in particular at the location of the brightness sensor 130. This is achieved in that the lamp driver 110 designed as a control unit strives to keep the control signal at zero or zero internregeln.
  • the lamp driver 110 is able at any time to carry out a positive or negative correction / regulation of the brightness if this should be necessary in order to keep the brightness essentially constant.
  • the filter 140 can also be designed as a band pass filter, ie as a combined high and low pass filter. It then preferably has a lower cut-off frequency of less than 1 Hz and an upper cut-off frequency of more than 100 Hz, depending on the lamp type and projection system.
  • the upper limit frequency is advantageously above the brightness fluctuation frequency which is perceptible to the human eye.
  • the bandpass filter advantageously also results in a limitation in the upper frequency range. This simplifies the requirements for the design of the lamp driver 110 in that the stability can be achieved much more easily with high quality than with a control signal that is only high-pass filtered.
  • the transfer function of the filter 110 can also be designed such that the filter not only enables low-pass or high-pass filtering, but also amplification of the sensor signal to generate the control signal.
  • the lamp driver 110 is also designed to regulate the electrical power at its output - and thus also the electrical power consumption of the lamp - in the long term constantly at the nominal power level. This is usually done by monitoring the product of lamp current and lamp voltage at the output of lamp driver 110. The power control is superimposed on the lamp current control described above for the purpose of keeping the average lamp power constant.
  • the lamp driver 110 In order to counteract a drop in the brightness of the HID lamp 322 suddenly registered by the brightness sensor 130, the lamp driver 110 first increases the lamp current as part of the brightness control so that the brightness initially remains constant. This increase in lamp current leads to an increase in electrical power provided for the lamp 322 at the output of the lamp driver 110 and is recognized by the power control.
  • the power delivered to the HID lamp 322 may briefly exceed its nominal power, but not for a long time. If the increased lamp current is not returned by the brightness control within a certain time, e.g.
  • the power control intervenes and reduces the lamp current, although the lamp then only emits a reduced brightness , In this way, the higher-level power control ensures that the lamp is not operated above its nominal power level in the long term.
  • the reduction in lamp current caused by the power control and the resulting reduction in the brightness of the lamp light is advantageously not perceived by a human viewer because it takes place particularly slowly. The insensitivity of the human eye to slow changes in brightness is exploited.
  • control signal of the flicker control also disappears after some time due to the high-pass characteristic, so that the lamp power returns to the initial value, even if the power control is not effective.
  • the circuit according to the invention ensures that the lamp is always operated at nominal power level on average throughout its entire service life. This has the advantage that the lamp has a maximum service life and that the luminous efficacy of the lamp is always optimal from the start of its life.
  • FIGS. 1, 3 and 2 shows an image projector with HID lamps as a preferred application example for the electronic circuit according to the invention.
  • the image projector essentially comprises the electronic circuit acc. Fig. 1 and the optical system as described above with reference to Fig. 3. Components with the same reference numerals in FIGS. 1, 3 and 2 are to be regarded as identical or with the same effect.
  • the image generator 424 is installed between two lens systems 425a, 425b and the brightness sensor 130 in the vicinity of the image generator 424 or arranged in such a way that it detects the amount of light incident on the image generator.
  • the electronic circuit in the projector therefore ensures that the image generator 424 is illuminated only with light of medium-term constant brightness and that the image projected onto a screen 426 by the image generator 424 is therefore not subject to any brightness fluctuations visible to the human eye.

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  • Projection Apparatus (AREA)
  • Circuit Arrangement For Electric Light Sources In General (AREA)
  • Circuit Arrangements For Discharge Lamps (AREA)

Abstract

The circuit has a lamp driver (110) for providing a regulated lamp current to operate the HID lamp (322) in response to a control signal and an intensity sensor (130) for producing and outputting a sensor signal representing the light output at the sensor position. A high pass filter (140) provides the control signal by filtering the sensor signal. Independent claims are also included for the following: an electrical circuit and an image projector with an HID lamp.

Description

Die Erfindung betrifft einen elektronischen Schaltkreis zum Betreiben einer High-Intensity-Discharge HID-Lampe, insbesondere einer Ultra-High-Pressure UHP-Lampe gemäß dem Oberbegriff des Patentanspruchs 1.The invention relates to an electronic circuit for operating a high-intensity discharge HID lamp, in particular an ultra-high-pressure UHP lamp according to the preamble of patent claim 1.

Die Erfindung betrifft weiterhin einen Bildprojektor mit dem elektronischen Schaltkreis nach Anspruch 1.The invention further relates to an image projector with the electronic circuit according to claim 1.

HID- und UHP-Lampen sind im Stand der Technik grundsätzlich bekannt. Sie werden vorzugsweise für Projektionszwecke, aber auch z.B. zum Betrieb von Autoscheinwerfern verwendet. Sie zeichnen sich durch einen sehr kleinen Lichtbogen und eine zugleich hohe Lichtausbeute aus, was vorteilhafterweise zu einem sehr guten Gesamtwirkungsgrad führt. Die Helligkeit dieser Lampen liegt bei etwa dem zwei bis vierfachen anderer Gasentladungslampen.HID and UHP lamps are generally known in the prior art. They are preferably used for projection purposes, but also e.g. used to operate car headlights. They are characterized by a very small arc and a high luminous efficacy, which advantageously leads to a very good overall efficiency. The brightness of these lamps is about two to four times that of other gas discharge lamps.

Nachteilig bei diesen HID-Lampen ist jedoch der Effekt des Bogenspringens, d.h. einer Veränderung der Position des Lichtbogens, während des Betriebs dieser Lampen. Durch die Veränderung der Bogenposition ändert sich der Anteil des von der Lampe insgesamt erzeugten Lichtes, welches auf das bilderzeugende System gelangt, so dass die Helligkeit des projizierten Bildes schwankt. Auch führt dieser Effekt zu unerwünschten Schwankungen der Helligkeitsverteilung auf dem Bilderzeuger. Es entsteht ein vom Betrachter wahrnehmbarer Flickereffekt.However, the disadvantage of these HID lamps is the effect of archery, i.e. a change in the position of the arc while these lamps are operating. The change in the arc position changes the proportion of the light generated by the lamp as a whole, which reaches the imaging system, so that the brightness of the projected image fluctuates. This effect also leads to undesirable fluctuations in the brightness distribution on the image generator. A flicker effect is perceptible to the viewer.

Zur Reduktion des Flickereffektes sind im Stand der Technik verschiedene Ansätze bekannt.Various approaches are known in the prior art for reducing the flicker effect.

Ein erster Ansatz sieht einen zusätzlichen hohen Strompuls im Verlauf des Lampenstromes vor dessen Kommutierung vor. Aufgrund dieser speziellen Form des Lampenstromes kann das Bogenspringen und damit der Flickereffekt wirkungsvoll unterdrückt werden.A first approach provides for an additional high current pulse in the course of the lamp current before it is commutated. Due to this special form of lamp current, archery and thus the flicker effect can be effectively suppressed.

Das Vorsehen des hohen Strompulses hat jedoch zum einen den Nachteil, dass der Lampentreiber größer und teurer wird als bei einem andersförmigen Lampenstrom, und zum anderen, dass die Lebensdauer der HID-Lampe deutlich reduziert wird.The provision of the high current pulse has the disadvantage, on the one hand, that the lamp driver becomes larger and more expensive than with a different lamp current, and, on the other hand, that the service life of the HID lamp is significantly reduced.

Ein zweiter Ansatz, der auch zur Reduktion des Flickereffektes geeignet sein kann, ist in der JP-2000028988 A offenbart und in der Fig. 3 dargestellt. Die JP beschreibt zwar primär die Lösung eines anderen Problems, nämlich einer allmählichen Veränderung der Lampenhelligkeit über die gesamte Lebensdauer, auch offenbart sie nicht explizit die Kriterien, die für eine Unterdrückung des Flickereffektes erfüllt sein müssen. Allerdings entnimmt der Fachmann der JP dennoch zumindest indirekt auch geeignete Maßnahmen zur Reduktion des Flickereffektes. In der JP-200028988 A ist ein LCD-Projektor mit einem optischem System 420 und einem elektrischen Schaltkreis offenbart. Das optische System 420 umfasst eine Gasentladungslampe 422 mit einem Reflektor 421 sowie der Lampe nachgeschaltet einen Integrator 423, einen Bilderzeuger 424 und ein Objektiv 425b. Der Integrator 423 gewährleistet zusammen mit einem Kondensor 425a eine gleichmäßige Helligkeitsverteilung bei der Beleuchtung des Bilderzeugers 424 und damit in dem von dem Bilderzeuger erzeugten Bild. Der elektrische Schaltkreis dient zum Betreiben der Lampe 422. Er umfasst einen Lampentreiber 410 zum Bereitstellen eines geregelten Lampenstromes für die Lampe 422 im Ansprechen auf ein Steuersignal und einen Helligkeitssensor 430 zum Erzeugen und Ausgeben eines Sensorsignals. Das Sensorsignal repräsentiert dabei die von der Lampe abgegebene Lichtmenge am Ort des Helligkeitssensors. Die durch das Sensorsignal repräsentierte Lichtmenge wird in einem Mikroprozessor 440 mit einer vorgegebenen Referenzlichtmenge verglichen, um dann nach Maßgabe durch die gemessene Lichtmengenabweichung das Steuersignal zu erzeugen und an den Lampentreiber auszugeben. Auf diese Weise wird die abgegebene Lichtmenge auf den Referenzwert eingeregelt. Ein Flickereffekt kann unterbunden werden, wenn die Lichtmengenregelung schnell genug erfolgt.A second approach, which can also be suitable for reducing the flicker effect, is disclosed in JP-2000028988 A and shown in FIG. 3. Although the JP primarily describes the solution to another problem, namely a gradual change in the lamp brightness over the entire service life, it also does not explicitly disclose the criteria that must be met to suppress the flicker effect. However, the person skilled in the art nevertheless at least indirectly also takes suitable measures for reducing the flicker effect. JP-200028988 A discloses an LCD projector with an optical system 420 and an electrical circuit. The optical system 420 comprises a gas discharge lamp 422 with a reflector 421 and, downstream of the lamp, an integrator 423, an image generator 424 and an objective 425b. The integrator 423 together with a condenser 425a ensures a uniform brightness distribution when illuminating the image generator 424 and thus in the image generated by the image generator. The electrical circuit is used to operate the lamp 422. It comprises a lamp driver 410 for providing a regulated lamp current for the lamp 422 in response to a control signal and a brightness sensor 430 for generating and outputting a sensor signal. The sensor signal represents the amount of light emitted by the lamp at the location of the brightness sensor. The quantity of light represented by the sensor signal is compared in a microprocessor 440 with a predetermined reference quantity of light, in order then to generate the control signal in accordance with the measured quantity of light deviation and to output it to the lamp driver. In this way, the amount of light emitted is adjusted to the reference value. A flicker effect can be prevented if the light quantity control is done quickly enough.

Die von Gasentladungslampen bei gleicher Leistung abgegebene Lichtmenge nimmt im Laufe ihres Lebens aufgrund verschiedener Ursachen ab. Um jedoch über die gesamte Lebensdauer der Lampe eine gleichbleibende Helligkeit gewährleisten zu können, wird gemäß der japanischen Druckschrift JP-2000028988 A vorgeschlagen, die Lampe zu Beginn ihres Lebens bei einer Leistung deutlich unterhalb ihrer Nennleistung zu betrieben und mit zunehmendem Betriebsalter die Betriebsleistung immer weiter zu erhöhen, um eine konstante Helligkeit des von der Lampe erzeugten Lichtes zu gewährleisten. Das ist jedoch nur solange möglich, bis die Nennleistung erreicht ist.The amount of light emitted by gas discharge lamps with the same power decreases over the course of their life due to various causes. However, in order to be able to guarantee a constant brightness over the entire life of the lamp, it is proposed according to Japanese publication JP-2000028988 A to start with the lamp of their life at a power significantly below their nominal power and increasing the operating power with increasing operating age to ensure a constant brightness of the light generated by the lamp. However, this is only possible until the nominal power is reached.

Allerdings bringt dieser zweite Ansatz folgende Nachteile mit sich:
Dadurch, dass von vornherein die Lampe mit einer geringeren als der Nennleistung betrieben wird, ist die erzeugte Helligkeit wesentlich geringer als bei Nennleistung, d.h. ein solches Projektorsystem benötigt eine größere Lampe, um von Beginn an die gleiche Helligkeit zu erzeugen, wie ein System ohne diese Art der Regelung.However, this second approach has the following disadvantages:
Due to the fact that the lamp is operated with a lower than the nominal power from the outset, the brightness generated is significantly lower than at nominal power, i.e. such a projector system requires a larger lamp to generate the same brightness from the start as a system without it Type of scheme.

HID-Lampen sind außerdem durch ein empfindliches thermisches Gleichgewicht gekennzeichnet, dass nur bei Nennleistung ausreichend gut eingehalten wird. Bei Abweichungen sind Nachteile bei der Lebensdauer zu erwarten, so dass die Regelung nach Art der JP-2000028988 A eine verkürzte Lebensdauer erwarten lässt.HID lamps are also characterized by a sensitive thermal equilibrium that can only be maintained sufficiently at rated power. In the event of deviations, disadvantages in the service life are to be expected, so that the regulation in the manner of JP-2000028988 A can be expected to have a shorter service life.

Weiterhin ist nur im Anfang eine positive und negative Ausregelung der Helligkeit möglich. Diese Möglichkeit wird mit steigender Betriebsleistung geringer und verschwindet schließlich ganz, wenn die Lampe mit Nennleistung betrieben wird. Schließlich sei erwähnt, dass bei der offenbarten Schaltung Sensorfehler, z.B. ein falscher sensorinterner Verstärkungsfaktor, unmittelbar zu einem fehlerhaften Steuersignal und damit zu einem unerwünschten Regelverhalten führen. Deshalb erfordert die offenbarte Schaltung i.d.R. besonders teuere u. aufwendige Sensoren, um Sensorfehler zu vermeiden.Furthermore, a positive and negative adjustment of the brightness is only possible at the beginning. This possibility diminishes with increasing operating power and finally disappears completely when the lamp is operated at nominal power. Finally, it should be mentioned that in the circuit disclosed, sensor errors, e.g. an incorrect sensor-internal gain factor, which leads directly to a faulty control signal and thus to an undesirable control behavior. Therefore, the disclosed circuit usually requires. particularly expensive and elaborate sensors to avoid sensor errors.

Insbesondere sollte der Helligkeitssensor bei der bekannten Schaltung nicht nur bei Raumtemperatur, sondern auch bei hohen Temperaturen im Inneren eines Bildprojektors noch zuverlässig arbeiten.In particular, the brightness sensor in the known circuit should not only work reliably at room temperature, but also at high temperatures inside an image projector.

Ausgehend von diesem Stand der Technik ist es die Aufgabe der vorliegenden Erfindung, einen elektronischen Schaltkreis zum Betreiben einer HID-Lampe sowie einen Bildprojektor mit einem derartigen elektronischen Schaltkreis so weiterzuentwickeln, dass eine Regelung der Helligkeit über die gesamte Lebensdauer der Lampe und eine Verwendung von einfacher aufgebauten und damit preisgünstigeren Sensoren möglich wird.Starting from this prior art, it is the object of the present invention to further develop an electronic circuit for operating an HID lamp and an image projector with such an electronic circuit in such a way that a regulation of the brightness over the entire life of the lamp and the use of simpler and therefore cheaper sensors.

Diese Aufgabe wird durch den Gegenstand des Patentanspruchs 1 gelöst. Genauer gesagt wird diese Aufgabe bei dem eingangs beschriebenen elektronischen Schaltkreis dadurch gelöst, dass er ein Hochpassfilter zum Bereitstellen des Steuersignals durch Hochpassfiltern des Sensorsignals aufweist.This object is achieved by the subject matter of patent claim 1. More precisely, this object is achieved in the electronic circuit described at the outset in that it has a high-pass filter for providing the control signal by high-pass filtering the sensor signal.

Durch das Hochpassfilter werden sehr niedrige Frequenzanteile der Helligkeitsschwankungen und insbesondere deren Gleichanteil, aus dem Sensorsignal herausgefiltert. Damit fehlen diese Frequenzanteile auch in dem Steuersignal und werden bei der Regelung der HID-Lampe nicht berücksichtigt.The high-pass filter filters out very low frequency components of the brightness fluctuations and in particular their direct components from the sensor signal. These frequency components are therefore also missing in the control signal and are not taken into account when regulating the HID lamp.

Die verbleibenden Wechselanteile der Helligkeitsschwankungen werden erfindungsgemäß auf Null geregelt, anstatt - wie im Stand der Technik - die absolute Helligkeit auf einen vorgegebenen Referenzwert zu regeln.According to the invention, the remaining alternating components of the brightness fluctuations are regulated to zero instead of - as in the prior art - regulating the absolute brightness to a predetermined reference value.

Dies hat zum einen den Vorteil, dass Auswirkungen von fehlerhaften Offsets oder fehlerhafte Empfindlichkeiten des Helligkeitssensors aus dem Sensorsignal herausgefiltert werden und somit keinen unerwünschten Effekt auf die Regelung ausüben. Es können deshalb bei der Realisierung des beanspruchten Schaltkreises sehr wohl einfache und preisgünstige Sensoren verwendet werden, ohne dass die Qualität der Regelung darunter leiden würde.On the one hand, this has the advantage that effects of faulty offsets or faulty sensitivities of the brightness sensor are filtered out of the sensor signal and thus have no undesired effect on the control. Simple and inexpensive sensors can therefore very well be used in the implementation of the circuit claimed, without the quality of the control being adversely affected.

Zum anderen ermöglicht das Hochpassfilter vorteilhafterweise eine Ausregelung der Helligkeitsschwankungen durch den Schaltkreis während der gesamten Lebensdauer der HID-Lampe. Die Ausregelung ist erfindungsgemäß insbesondere auch bei Nennleistungsbetrieb sowohl in positiver wie auch in negativer Richtung möglich.On the other hand, the high-pass filter advantageously enables the brightness fluctuations to be regulated by the circuit during the entire life of the HID lamp. The regulation is possible according to the invention, particularly in the case of nominal power operation, both in the positive and in the negative direction.

Bei der erfindungsgemäßen Ansteuerung der Lampe wird der Flickereffekt für das menschliche Auge wirkungsvoll unterbunden.When the lamp is actuated according to the invention, the flicker effect is effectively prevented for the human eye.

Gemäß einer vorteilhaften Ausführungsform ist eine Regelungseinheit innerhalb des Lampentreibers weiterhin ausgebildet, die am Ausgang der Regelungseinheit erzeugte elektrische Leistung so zu regeln, dass die HID-Lampe langfristig konstant auf Nennleistungsniveau betrieben wird. Dadurch wird zum einen die Lebensdauer der Lampe maximiert und zum anderen gewährleistet, dass die Lichtausbeute der Lampe während ihrer gesamten Lebensdauer maximal ist.According to an advantageous embodiment, a control unit within the lamp driver is also designed to control the electrical power generated at the output of the control unit in such a way that the HID lamp is constantly operated at the nominal power level in the long term. On the one hand, this maximizes the service life of the lamp and, on the other hand, it ensures that the luminous efficacy of the lamp is at a maximum during its entire service life.

Weitere vorteilhafte Ausführungsformen sind Gegenstand der Unteransprüche.Further advantageous embodiments are the subject of the dependent claims.

Die Aufgabe der Erfindung wird weiterhin durch den Gegenstand des Patentanspruchs 7 gelöst. Die Vorteile des dort beanspruchten Bildprojektors entsprechen im wesentlichen den oben im Hinblick auf den elektronischen Schaltkreis genannten Vorteilen. Besonders bei der Darstellung von unbewegten Bildern mit großen, einfarbigen Flächen reagiert das menschliche Auge empfindlich auf Flickereffekte. Daher ist die Unterdrückung dieses Effektes hier besonders vorteilhaft.The object of the invention is further achieved by the subject matter of claim 7. The advantages of the image projector claimed there essentially correspond to the advantages mentioned above with regard to the electronic circuit. The human eye is particularly sensitive to flicker effects when displaying still images with large, monochrome areas. Suppression of this effect is therefore particularly advantageous here.

Der Beschreibung sind insgesamt drei Figuren beigefügt, wobei

Fig. 1:
einen elektronischen Schaltkreis gemäß der Erfindung;
Fig. 2:
einen Bildprojektor mit optischem System und elektronischem Schaltkreis gemäß der Erfindung; und
Fig. 3:
einen Bildprojektor nach dem Stand der Technik;
zeigt.A total of three figures are attached to the description
Fig. 1:
an electronic circuit according to the invention;
Fig. 2:
an image projector with optical system and electronic circuit according to the invention; and
Fig. 3:
a prior art image projector;
shows.

Im folgenden wird ein bevorzugtes Ausführungsbeispiel der Erfindung unter Bezugnahme auf die Figuren 1 -3 detailliert beschrieben.A preferred embodiment of the invention is described in detail below with reference to FIGS. 1-3.

Fig. 1 zeigt einen elektronischen Schaltkreis zum Betreiben einer HID-Lampe, insbesondere einer UHP-Lampe, gemäß der Erfindung. Er umfasst einen Lampentreiber 110, einen Helligkeitssensor 130 und ein Filter 140.1 shows an electronic circuit for operating an HID lamp, in particular a UHP lamp, according to the invention. It comprises a lamp driver 110, a brightness sensor 130 and a filter 140.

Der Lampentreiber 110 ist als Regelungseinheit ausgebildet und dient zum Bereitstellen und Regeln eines Lampenstromes für den Betrieb der HID-Lampe 322 im Ansprechen auf ein Steuersignal, so dass die von der HID-Lampe abgegebene Lichtmenge am Ort des Helligkeitssensors 130 mittelfristig konstant ist.The lamp driver 110 is designed as a control unit and serves to provide and control a lamp current for the operation of the HID lamp 322 in response to a control signal, so that the amount of light emitted by the HID lamp at the location of the brightness sensor 130 is constant in the medium term.

Das von dem Helligkeitssensor 130 in Fig. 1 erzeugte Sensorsignal repräsentiert die von der HID-Lampe abgegebene Lichtmenge am Ort des Helligkeitssensors 130. Durch Filterung in einem Filter 140 wird das Sensorsignal in das Steuersignal umgewandelt. Das Filter 140 ist vorzugsweise als Hochpassfilter mit ausgebildet, so dass insbesondere der Gleichanteil aus dem Sensorsignal und damit auch aus dem Steuersignal herausgefiltert wird.The sensor signal generated by the brightness sensor 130 in FIG. 1 represents the amount of light emitted by the HID lamp at the location of the brightness sensor 130. Filtering in a filter 140 converts the sensor signal into the control signal. The filter 140 is preferably designed as a high-pass filter, so that in particular the direct component is filtered out of the sensor signal and thus also from the control signal.

Dies hat, wie oben im allgemeinen Teil der Beschreibung beschrieben, den Vorteil, dass sich bestimmte Messfehler des Helligkeitssensors 130 nicht negativ auf das Ergebnis der Regelung auswirken.As described above in the general part of the description, this has the advantage that certain measurement errors of the brightness sensor 130 do not have a negative effect on the result of the control.

Das erfindungsgemäß hochpassgefilterte Steuersignal repräsentiert lediglich den Wechselanteil im ursprünglichen Sensorsignal, d.h. nur die eigentlichen Helligkeitsschwankungen. Die Helligkeitsschwankungen können z.B. durch das oben beschriebene Bogenspringen oder durch einen Übergang der Lampe von einem diffusen Bogenzustand in einen konzentrierten Bogenzustand (Spot-mode) verursacht werden. Primäres Ziel der Regelung durch den Lampentreiber 110 ist die Erzeugung einer stabilisierten Helligkeit ohne schnelle Schwankungen, insbesondere am Ort des Helligkeitssensors 130. Dies wird dadurch erreicht, dass der als Regelungseinheit ausgebildete Lampentreiber 110 bestrebt ist, das Steuersignal auf Null zu halten bzw. zu Null auszuregeln.The control signal which is high-pass filtered according to the invention only represents the alternating component in the original sensor signal, ie only the actual brightness fluctuations. The brightness fluctuations can be caused, for example, by the arc jumping described above or by a transition of the lamp from a diffuse arc state to a concentrated arc state (spot mode). The primary aim of the control by the lamp driver 110 is to generate a stabilized brightness without rapid fluctuations, in particular at the location of the brightness sensor 130. This is achieved in that the lamp driver 110 designed as a control unit strives to keep the control signal at zero or zero auszuregeln.

Der Lampentreiber 110 ist erfindungsgemäß jederzeit in der Lage, eine positive oder negative Korrektur / Regelung der Helligkeit vorzunehmen, wenn dies erforderlich sein sollte, um die Helligkeit im wesentlichen konstant zu halten.According to the invention, the lamp driver 110 is able at any time to carry out a positive or negative correction / regulation of the brightness if this should be necessary in order to keep the brightness essentially constant.

Alternativ zur Ausbildung als Hochpassfilter kann das Filter 140 auch als Bandpassfilter, d.h. als kombinierter Hoch- und Tiefpassfilter ausgebildet sein. Es weist dann vorzugsweise eine untere Grenzfrequenz von weniger als
1 Hz und eine obere Grenzfrequenz von mehr als 100 Hz, je nach Lampentyp und Projektionssystem auf. Die obere Grenzfrequenz liegt vorteilhafterweise oberhalb der für das menschliche Auge wahrnehmbaren Helligkeitsschwankungsfrequenz. Im Unterschied zum Hochpassfilter bewirkt das Bandpassfilter neben einer Kappung des Gleichanteils vorteilhafterweise zusätzlich eine Beschränkung im oberen Frequenzbereich. Das vereinfacht die Anforderungen an die Ausbildung des Lampentreibers 110 insofern, als dass die Stabilität bei gleichzeitig hoher Qualität viel einfacher erreicht werden kann, als bei einem nur hochpassgefilterten Steuersignal.As an alternative to the design as a high pass filter, the filter 140 can also be designed as a band pass filter, ie as a combined high and low pass filter. It then preferably has a lower cut-off frequency of less than
1 Hz and an upper cut-off frequency of more than 100 Hz, depending on the lamp type and projection system. The upper limit frequency is advantageously above the brightness fluctuation frequency which is perceptible to the human eye. In contrast to the high-pass filter, in addition to capping the direct component, the bandpass filter advantageously also results in a limitation in the upper frequency range. This simplifies the requirements for the design of the lamp driver 110 in that the stability can be achieved much more easily with high quality than with a control signal that is only high-pass filtered.

Die Übertragungsfunktion des Filters 110 kann weiterhin so ausgebildet sein, dass der Filter neben der Tief- bzw. Hochpassfilterung auch eine Verstärkung des Sensorsignals zur Erzeugung des Steuersignals ermöglicht.The transfer function of the filter 110 can also be designed such that the filter not only enables low-pass or high-pass filtering, but also amplification of the sensor signal to generate the control signal.

Üblicherweise ist der Lampentreiber 110 weiterhin ausgebildet, die elektrische Leistung an seinem Ausgang - und damit auch die elektrische Leistungsaufnahme der Lampe - langfristig konstant auf Nennleistungsniveau einzuregeln. Dies geschieht in der Regel durch Überwachung des Produktes aus Lampenstrom und Lampenspannung am Ausgang des Lampentreibers 110. Die Leistungsregelung ist der oben beschriebenen Lampenstromregelung zwecks Konstanthaltung der mittleren Lampenleistung überlagert.Usually, the lamp driver 110 is also designed to regulate the electrical power at its output - and thus also the electrical power consumption of the lamp - in the long term constantly at the nominal power level. This is usually done by monitoring the product of lamp current and lamp voltage at the output of lamp driver 110. The power control is superimposed on the lamp current control described above for the purpose of keeping the average lamp power constant.

Zwischen beiden Regelungen findet eine Wechselwirkung z.B. in folgender Weise statt:
Um einem von dem Helligkeitssensor 130 plötzlich registrierten Abfall der Helligkeit der HID-Lampe 322 entgegenzuwirken, veranlasst der Lampentreiber 110 zunächst im Rahmen der Helligkeitsregelung eine Erhöhung des Lampenstromes so, dass die Helligkeit zunächst konstant bleibt. Diese Erhöhung des Lampenstromes führt zu einer Erhöhung der am Ausgang des Lampentreibers 110 bereitgestellten elektrischen Leistung für die Lampe 322 und wird von der Leistungsregelung erkannt. Kurzzeitig darf die an die HID-Lampe 322 abgegebene Leistung durchaus deren Nennleistung übersteigen, allerdings nicht für längere Zeit. Wird der erhöhte Lampenstrom nicht innerhalb einer gewissen Zeit wieder von der Helligkeitsregelung zurückgefahren, z.B. weil die Lampe aufgrund einer veränderten Bogenposition wieder ein helleres Licht abgibt, dann greift die Leistungsregelung ein und fährt den Lampenstrom, obwohl die Lampe dann nur eine reduzierte Helligkeit abgibt, zurück. Auf diese Weise stellt die überlagerte Leistungsregelung sicher, dass die Lampe langfristig nicht über ihrem Nennleistungsniveau betrieben wird. Die durch die Leistungsregelung verursachte Verringerung des Lampenstromes und die daraus resultierende Verringerung der Helligkeit des Lampenlichtes wird vorteilhafterweise von einem menschlichen Betrachter nicht wahrgenommen, weil sie besonders langsam erfolgt. Dabei wird die Unempfindlichkeit des menschlichen Auges gegenüber langsamen Helligkeitsänderungen ausgenutzt.There is an interaction between the two regulations, for example in the following way:
In order to counteract a drop in the brightness of the HID lamp 322 suddenly registered by the brightness sensor 130, the lamp driver 110 first increases the lamp current as part of the brightness control so that the brightness initially remains constant. This increase in lamp current leads to an increase in electrical power provided for the lamp 322 at the output of the lamp driver 110 and is recognized by the power control. The power delivered to the HID lamp 322 may briefly exceed its nominal power, but not for a long time. If the increased lamp current is not returned by the brightness control within a certain time, e.g. because the lamp emits a brighter light due to a changed arc position, the power control intervenes and reduces the lamp current, although the lamp then only emits a reduced brightness , In this way, the higher-level power control ensures that the lamp is not operated above its nominal power level in the long term. The reduction in lamp current caused by the power control and the resulting reduction in the brightness of the lamp light is advantageously not perceived by a human viewer because it takes place particularly slowly. The insensitivity of the human eye to slow changes in brightness is exploited.

Außerdem verschwindet durch die Hochpasscharakteristik das Steuersignal der Flickerregelung ebenfalls nach einiger Zeit, so dass die Lampenleistung wieder auf den Ausgangswert zurückgeht, auch wenn die Leistungsregelung nicht wirksam wird.In addition, the control signal of the flicker control also disappears after some time due to the high-pass characteristic, so that the lamp power returns to the initial value, even if the power control is not effective.

Durch den erfindungsgemäßen Schaltkreis wird gewährleistet, dass die Lampe während ihrer gesamten Lebensdauer durchschnittlich immer auf Nennleistungsniveau betrieben wird. Das hat den Vorteil, dass die Lebensdauer der Lampe maximal ist und dass die Lichtausbeute der Lampe von Beginn ihrer Laufzeit an immer optimal ist.The circuit according to the invention ensures that the lamp is always operated at nominal power level on average throughout its entire service life. This has the advantage that the lamp has a maximum service life and that the luminous efficacy of the lamp is always optimal from the start of its life.

Fig. 2 zeigt einen Bildprojektor mit HID-Lampen als bevorzugtes Anwendungsbeispiel für den erfindungsgemäßen elektronischen Schaltkreis. Der Bildprojektor umfasst im wesentlichen den elektronischen Schaltkreis gem. Fig. 1 und das optische System wie es oben unter Bezugnahme auf Fig. 3 beschrieben wurde. Komponenten mit gleichen Bezugszeichen in den Fig. 1, 3 und 2 sind als identisch bzw. wirkungsgleich anzusehen.2 shows an image projector with HID lamps as a preferred application example for the electronic circuit according to the invention. The image projector essentially comprises the electronic circuit acc. Fig. 1 and the optical system as described above with reference to Fig. 3. Components with the same reference numerals in FIGS. 1, 3 and 2 are to be regarded as identical or with the same effect.

In dem Bildprojektor gem. Fig. 2 ist der Bilderzeuger 424 zwischen zwei Linsensysteme 425a, 425b eingebaut und der Helligkeitssensor 130 in der Umgebung des Bilderzeugers 424 oder in diesem selber so angeordnet, dass er die auf den Bilderzeuger einfallende Lichtmenge erfasst. Der elektronische Schaltkreis in dem Projektor stellt deshalb sicher, dass der Bilderzeuger 424 lediglich mit Licht von mittelfristig konstanter Helligkeit beleuchtet wird und dass somit auch das durch den Bilderzeuger 424 auf einen Bildschirm 426 projizierte Bild keinen für das menschliche Auge sichtbaren Helligkeitsschwankungen unterliegt.In the image projector acc. 2, the image generator 424 is installed between two lens systems 425a, 425b and the brightness sensor 130 in the vicinity of the image generator 424 or arranged in such a way that it detects the amount of light incident on the image generator. The electronic circuit in the projector therefore ensures that the image generator 424 is illuminated only with light of medium-term constant brightness and that the image projected onto a screen 426 by the image generator 424 is therefore not subject to any brightness fluctuations visible to the human eye.

Claims (7)

Elektronischer Schaltkreis zum Betreiben einer High-Intensity-Discharge HID-Lampe (422), insbesondere einer Ultra-High-Pressure UHP-Lampe, umfassend: einen Lampentreiber (110) zum Bereitstellen eines geregelten Lampenstromes für den Betrieb der HID-Lampe (422) im Ansprechen auf ein Steuersignal; und einen Helligkeitssensor (130) zum Erzeugen und Ausgeben eines Sensorsignals, wobei das Sensorsignal die von der HID-Lampe (422) abgegebene Lichtmenge am Ort des Helligkeitssensors (130) repräsentiert; gekennzeichnet durch ein Filter (140), welches als Hochpassfilter ausgebildet ist, zum Bereitstellen des Steuersignals durch Hochpassfiltern des Sensorsignals.Electronic circuit for operating a high-intensity discharge HID lamp (422), in particular an ultra-high-pressure UHP lamp, comprising: a lamp driver (110) for providing a regulated lamp current to operate the HID lamp (422) in response to a control signal; and a brightness sensor (130) for generating and outputting a sensor signal, the sensor signal representing the amount of light emitted by the HID lamp (422) at the location of the brightness sensor (130); characterized by a filter (140), which is designed as a high-pass filter, for providing the control signal by high-pass filtering the sensor signal. Elektrischer Schaltkreis nach Anspruch 1,
dadurch gekennzeichnet,
dass die Grenzfrequenz des Hochpassfilters unterhalb von 1 Hz liegt.Electrical circuit according to claim 1,
characterized,
that the cut-off frequency of the high-pass filter is below 1 Hz. Elektronischer Schaltkreis nach Anspruch 1,
dadurch gekennzeichnet,
dass das Filter (140) als Bandpassfilter ausgebildet ist.Electronic circuit according to claim 1,
characterized,
that the filter (140) is designed as a bandpass filter. Elektronischer Schaltkreis nach Anspruch 3,
dadurch gekennzeichnet,
dass die untere Grenzfrequenz des Bandpassfilters bei weniger als 1 Hz und dessen obere Grenzfrequenz bei über 100 Hz liegt.Electronic circuit according to claim 3,
characterized,
that the lower limit frequency of the bandpass filter is less than 1 Hz and its upper limit frequency is above 100 Hz. Elektronischer Schaltkreis nach Anspruch 1,
dadurch gekennzeichnet,
dass der Lampentreiber (110) als eine Regelungseinheit ausgebildet ist zum Bereitstellen und Regeln des Lampenstromes im Ansprechen auf das Steuersignal so, dass die von der HID-Lampe (422) abgegebene Lichtmenge am Ort des Helligkeitssensors mittelfristig konstant ist.Electronic circuit according to claim 1,
characterized,
that the lamp driver (110) is designed as a control unit for providing and controlling the lamp current in response to the control signal such that the amount of light emitted by the HID lamp (422) is constant at the location of the brightness sensor in the medium term. Elektronischer Schaltkreis nach Anspruch 5,
dadurch gekennzeichnet,
dass der Lampentreiber (110) weiterhin ausgebildet ist, die am Ausgang der Regelungseinheit erzeugte elektrische Leistung so zu regeln, dass die HID-Lampe (422) langfristig konstant auf Nennleistungsniveau betrieben wird.Electronic circuit according to claim 5,
characterized,
that the lamp driver (110) is further designed to regulate the electrical power generated at the output of the control unit in such a way that the HID lamp (422) is operated constantly at the nominal power level in the long term. Bildprojektor mit einer High-Intensity-Discharge HID-Lampe, insbesondere mit einer Ultra-High-Pressure UHP-Lampe, umfassend: ein optisches System (420) umfassend die HID-Lampe (422) sowie der HID-Lampe nachgeschaltet einen Bilderzeuger (424) zum Erzeugen eines Bildes; und den elektronischen Schaltkreis nach Anspruch 1, wobei der Helligkeitssensor (130) in dem optischen System (420) positioniert ist, so dass das Sensorsignal die von der HID-Lampe erzeugte und auf den Bilderzeuger (424) einfallende Lichtmenge repräsentiertImage projector with a high-intensity discharge HID lamp, in particular with an ultra-high-pressure UHP lamp, comprising: an optical system (420) comprising the HID lamp (422) and, downstream of the HID lamp, an image generator (424) for generating an image; and the electronic circuit according to claim 1, wherein the brightness sensor (130) is positioned in the optical system (420) so that the sensor signal represents the amount of light generated by the HID lamp and incident on the image generator (424)
EP02016738A 2001-07-27 2002-07-26 Electronic circuit for operating an HID lamp and an associated image projecting apparatus Expired - Lifetime EP1280387B1 (en)

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PATENT ABSTRACTS OF JAPAN Bd. 2000, Nr. 04, 31. August 2000 (2000-08-31) & JP 2000 028988 A (TOSHIBA CORP), 28. Januar 2000 (2000-01-28) *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003056817A1 (en) * 2002-01-02 2003-07-10 Philips Intellectual Property & Standards Gmbh Image projector and method of operating same
WO2004010710A2 (en) * 2002-07-18 2004-01-29 Philips Intellectual Property & Standards Gmbh Projection system
WO2004010710A3 (en) * 2002-07-18 2004-06-03 Philips Intellectual Property Projection system
US7425932B2 (en) 2002-07-18 2008-09-16 Koninklijke Philips Electronics, N.V. Projection system featuring light source luminuous flux sensing and compensation
EP1554891A1 (en) * 2002-10-17 2005-07-20 Philips Intellectual Property & Standards GmbH Image projector with intensity-controlled light source

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KR20030011622A (en) 2003-02-11
CN1407843A (en) 2003-04-02
US6779896B2 (en) 2004-08-24
KR100906624B1 (en) 2009-07-09
DE50208237D1 (en) 2006-11-09
TW552828B (en) 2003-09-11
CN100339760C (en) 2007-09-26
EP1280387B1 (en) 2006-09-27
US20030020412A1 (en) 2003-01-30
JP4198408B2 (en) 2008-12-17
EP1280387A3 (en) 2004-04-28
JP2003123991A (en) 2003-04-25
DE10136474A1 (en) 2003-02-13

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