EP1152645A1 - Method and device to control a gas discharge lamp circuit - Google Patents

Abstract

The method involves continuously or discontinuously measuring the value of at least one operating parameter of the gas discharge lamp that varies over time and selecting the frequency of the alternating voltage or current (the operating frequency) depending on the measured value, e.g. of the total operating duration, the burn voltage, the emitted or tapped power, the arc length and the electrode separation. Independent claims are also included for the following: an arrangement for operating a gas discharge lamp, a gas discharge lamp with two electrodes, a projector with a gas discharge lamp, a vehicle with a gas discharge lamp, a projector with a device for operating a gas discharge lamp, a vehicle with a device for operating a gas discharge lamp, a method of machining an electrode and a machine-readable data medium with a control program for controlling a device for operating a gas discharge lamp.

Description

The invention relates to a method and a device for operating a AC voltage or AC-powered gas discharge lamp, being in certain Time intervals the instantaneous power of the lamp is increased (pulsed Business). In addition, the invention relates to such lamps and devices provided devices as well as processing methods based on the operating method an electrode.

Such operating methods and devices are known, for example from WO 96/174724 or US 5,608,294. In the aforementioned WO document, a device described with a power supply circuit for operating a gas discharge lamp, wherein the power supply circuit is an AC voltage or an AC current predetermined period for feeding the gas discharge lamp with a provides predetermined power in such a way that with a reduction of the average Lamp power compared to the nominal power immediately before reversing the polarity of the AC voltage or an increase in the alternating current within half a period the current performance. This brief increase in current performance before the polarity reversal process causes the necessary re-ignition voltage after the The polarity reversal process cannot be significantly increased compared to the voltage during nominal operation got to.

A method for operating a gas discharge lamp is known from the cited US document known with a short arc, in which the lamp determines an alternating current Period duration supplied and a short current pulse to the lamp current in each half period is superimposed on the same polarity as the lamp current in the respective half-period has what the constancy of the arc and the durability of the electrodes of the Gas discharge lamp significantly improved.

The variation of the current strength or the voltage known from the cited documents, which is hereinafter referred to as "pulsed operation" or "pulsed operation" has in the Proven in practice. It should be emphasized at this point that the terms "pulsed Operation "and" pulse operation "here all forms of current and voltage curve denote by the time at which the operating current or operating voltage especially for the purpose of stabilizing the lamp arc additional current or Voltage pulses are superimposed (in some documents (see e.g. EP 0 865 210 A2, WO 97/247871 or US 5,428,408), however, is called "pulsed operation" understood only a lamp operating mode in which a lamp repeated quickly, is operated in very short periods of time and for a large part of the Time no light emits).

Due to the pulsed operation, the constancy of the arc can be significantly improved However, the service life is particularly high-pressure gas discharge lamps with a very short arc, e.g. with data and video projectors with LC or mirror displays (Deformable Mirror Device), but also with various other applications an important one? Play role, not yet satisfactory. The shorter the required arcs, the stronger a burning back of the lamp electrodes and the consequent extension of the arc that arises between the electrodes disadvantageously noticeable. This is how the lamp electrodes burn back with gas discharge lamps with short and very short arcs, it is not uncommon already in the first 100 hours of operation, for example, in a drop in efficiency Projection system of 20%.

In addition, the production of gas discharge lamps with a very short electrode spacing is extremely difficult, because the electrodes are usually melted in a quartz tube and positioned in the tube before melting, so that their position deviates from the original adjustment due to the manufacturing process, both in terms of the manufacturing process the distance as well as the lateral alignment to each other. The positioning tolerances of the electrodes can only be reduced at considerable expense.
Another problem that can only be solved with great effort is the geometric shape of the electrodes themselves. Although it is entirely possible to cut desired electrode geometries out of solid material, electrodes are preferred for cost reasons, which consist of an electrode rod (drawn tungsten wire) and a tungsten spiral pushed over it exist, although with such a construction the geometry and the internal structure of the electrodes, which ultimately determines the heat distribution, are less controllable. In the case of lamps with a short arc, the enormous thermal load on the electrodes leads to rapid transport of the electrode material (e.g. vaporization of tungsten), which can, for example, completely change the front face of the electrodes in a few hours in the case of high-pressure gas discharge lamps with an arc length of approximately 1 mm . Even an ideally shaped electrode usually retains its original functional properties for less than 100 hours.

Proceeding from this, the object of the invention is a method and a device to operate a gas discharge lamp, which allow the transport processes taking place when operating a gas charge lamp advantageously for Forming the electrodes.

The object is achieved by a method according to claim 1 or by a device According to claim 11. Advantageous embodiments are Subject of the subclaims. The secondary claims relate to this Machining methods and devices based on methods and devices.

In particular, the object is achieved by a method of the type mentioned at the outset, in which the values of at least one operating date which changes over time Lamp can be measured continuously or discontinuously and the frequency of the AC voltage or alternating current (operating frequency) depending on the measured values is selected. The operating frequency is expediently in Dependence on the measured values of at least one operating date from which the Total operating time of the lamp, the burning voltage, the delivered or received Performance, the arc length and the electrode spacing comprehensive group of operating data chosen, because all these data allow direct or indirect conclusions to be drawn State of the electrodes, in particular the distance between the electrodes (for example, from the operating time even for a new lamp with zero operating time based on Experience based on the approximate condition of the electrodes and thus on the Need to be closed for a certain operating frequency selection).

The invention is based on the new finding that the size of when operating with AC current or voltage on the structures growing on the electrodes and the operating frequency of the current or voltage are proportional to each other It has It has been shown that the diameter of the grown structures is the smaller, each the basic frequency of the operating current or the operating voltage is higher. Typical Frequencies in high pressure gas discharge lamps are between approximately 40 and 600 Hz For lamps of a certain type (e.g. according to DE 38 13 421 A), e.g. the approximate diameter of the grown structures = a / f1 / 2, where f the operating frequency in Hertz and a is a lamp-specific proportionality constant, which is typically between about 2000 and 5000 µm Hz1 / 2, so that at 100 Hz Basic frequency form structures with a diameter of approximately 200 to 500 µm. In general this constant can be between 1000 and 10,000 µm Hz1 / 2. The The resulting structures are usually smaller than their diameter and is usually about 0.4 to 0.8 times the diameter. The relationship can however, experience has shown that it varies between 0.2 and 1.2. This connection will exploited according to the invention in a controllable manner protruding electrode tips to generate during lamp operation.

The invention allows the electrode to be shaped during operation, within certain limits regardless of the production-related initial shape of the electrodes. The one you want Electrode spacing or the desired operating voltage can be exploited by Transport operations can be set within certain limits. Upon reaching the The conditioning process is interrupted and the lamp at the then current frequency operated.

A particular advantage of the method according to the invention is that during the Operating time of the lamp can be used again and again and so to speak "Regeneration" of the electrodes allowed, so that excellent results over a very long life can be achieved.

The electrode structures built up during operation are due to the physical laws of transport processes practically exactly opposite, so that no lateral offset occurs. If you start with sufficiently low frequencies, the structure is in the middle of the electrode.

For this purpose, the measured values are advantageous for fulfilling specified boundary conditions monitors and upon fulfillment of a first boundary condition (start condition) Lamp operated at a low operating frequency (start frequency) until a second Boundary condition is met, whereupon the operating frequency is increased. Such starting conditions can, for example, commission a new lamp for the first time or The required burning voltage increases beyond a predetermined limit his. In particular, it is also possible to have different starting conditions with different ones Define start frequencies so that, for example, the first time Commissioning of a new lamp successive structures with diminishing Diameter can be built up on the electrodes, with a relative low start frequency is started, while it is only for electrodes whose shape should be changed slightly, it may be sufficient to immediately build very small structures and start with a relatively high start frequency.

The operating frequency can be increased continuously for the successive construction of the structures become. However, it has proven to be particularly advantageous to set the operating frequency in increment discrete steps until a predetermined termination condition is reached. Such termination conditions can be: reaching a predetermined operating frequency (Maximum frequency), reaching a predetermined minimum burning voltage, constancy of the electrode gap over a predetermined period.

In the case of a device for operating that is provided for solving the stated task a gas discharge lamp are measuring devices for continuous or discontinuous Measuring the values of at least one operating date that changes over time Lamp and means for changing the frequency of the alternating voltage or alternating current (Operating frequency) depending on the measured values. A Such a device can also be used for gas discharge lamps and gas discharge lamps that have already been produced all types of lighting devices used, such as projectors in particular, Automotive lighting systems, etc., easily applied or retrofitted.

In a preferred embodiment, the device has at least one Compact processor and control unit for controlling the microprocessor Operating frequency, the operating voltage and that supplied to the gas discharge lamp Alternating current and for evaluating and monitoring the measured values for the Fulfillment of predefined or predefinable boundary conditions, advantageously from the in existing devices for the pulsed operation of gas discharge lamps existing processors and units can be used.

Further details and advantages of the invention result from the following purely exemplary and non-limiting description of advantageous embodiments inventive method, reference being made to the drawing.

Show it:

Fig. 1

a typical time course of a gas discharge lamp in the pulsed Operation supplied operating current

Fig. 2

is a schematic representation of the side profile of a with a erfindungsge shaped electrode.

In the already mentioned US 5,608,294 an electronic ballast is described by means of which a current form according to FIG. 1 with an extra current pulse of height I3 and the duration tp at the end of the respective half-wave of the total duration t1 / 2 and Basic height I2 can be generated. This is preferably controlled by a microprocessor Ballast implemented that can also control the lamp operating frequency. This can also include a data carrier that executes a control program contains the process steps described below. A reading device can also be used be provided, by means of which a machine-readable data carrier is read and the Data can be transmitted to the ballast.

To build an electrode with the desired shape shown in profile in FIG the lamp starting from a low starting frequency in pulse mode with slow increasing frequency operated. A low frequency at the beginning of the sequence ensures a broad structure 1 as a basis on which then always narrower at higher frequencies Structures 2 and 3 are built. The transition can be continuous or in discrete levels. Practical results were e.g. with an operation of each a few hours at 45, 65, 90 and 130 Hz in this ascending order achieved. With this operating mode it was possible to determine the electrode spacing in a high pressure gas discharge lamp to reduce the usual design from 1.3 mm to 0.7 mm. At prolonged operation (a few 100 hours) of the lamp conditioned in this way with the highest Frequency then gradually burn the electrodes back to the starting distance, which can easily be observed by an increase in the burning voltage.

If the burning voltage increases, the electrode can, according to the invention, increase slowly Frequencies are treated again until the tip structures of the electrodes are almost are completely rebuilt. After each such regeneration process, the Lamp operated for about 100 hours on the highest selected frequency.

The invention has the advantage that the light from the lamp can also be used during the regeneration phases. Overall, as the distance between the electrodes increases, there is usually a decrease in the optical efficiency (for example a decrease in the screen brightness in the case of video projection, which then increases again during the regeneration). This system efficiency, which fluctuates on a time scale of 100 hours, is in any case a great advantage over a continuously decreasing efficiency.
The need for renewed regeneration can easily be determined from the voltage increase in the lamp. If the burning voltage rises above a specified value, a new regeneration is started.

The following explains how the method according to the invention operates during operation of a gas discharge lamp of a video projector:

A first-time operation of the lamp is recognized by an operating hours counter, which at a lamp change is automatically reset. This is common with many on the market Projectors already realized.

The lamp is initially operated at the lowest possible frequency (e.g. 45 Hz). This operation can take place over a fixed period (e.g. 1 operating hour). Alternatively the frequency can also be held until there is no significant drop in voltage (which indicates the growth of structures) more can be observed. advantage This type of procedure is that individual differences are better taken into account than when operating for fixed periods.

Then the frequency is increased. It has been shown that increasing the Frequency approximately 1.2 to 1.8 times the previous frequency recommended is. The operating time with the new frequency can then again be a fixed one Period of time or until there is no longer any noticeable drop in voltage is.

Overall, the frequency is increased until either a) a fixed frequency limit is reached, b) a set voltage has been reached, or c) nothing of note Growth can be observed after increasing the frequency.

The frequency determined in this way is recorded and can be used for as long as this until the tension becomes significant again, e.g. has risen to the initial level. However, the electrodes preferably become new even before they rise to the initial level "regenerates", which is why the lamp is operated again with the lowest possible frequency becomes.

With the method according to the invention, the operating voltage and arc length or Significantly reduce the gap between electrodes in gas discharge lamps. For example, could in a gas discharge lamp of conventional design with electrodes of the type described at the beginning simple and inexpensive design, in which the lamp current I2 for controlling the Power was set and the pulse current I3 was 2.8 A, with an operating frequency sequence from 45, 65, 90 and 130 Hz the burning voltage from initially 85 V to 52 V and the arc length was reduced from 1.3 mm initially to 0.7 mm, this being astonishing Reduction, mind you, not in a separate machining process, but instead during the "normal" use of the lamp, for example in projection mode.

Numerous modifications and further developments are within the scope of the inventive concept possible, for example, on the boundary conditions at which the operating frequencies be increased or decreased, or relate to the choice of operating frequencies. It is essential that the method involves machining the electrodes during operation of the gas discharge lamp This enables controlled changes in the operating frequency Transport phenomena used to deposit material on the electrodes become.

Claims (26)

Method for operating a gas discharge lamp fed with alternating voltage or alternating current, the instantaneous power of the lamp being increased at certain time intervals,
characterized in that the values of at least one lamp operating date which changes over time are measured continuously or discontinuously and the frequency of the alternating voltage or alternating current (operating frequency) is selected as a function of the measured values Method according to claim 1,
characterized in that the operating frequency is selected as a function of the measured values of at least one operating date from the following group of operating data:
Total operating time of the lamp, burning voltage, power delivered or consumed arc length, electrode spacing. The method of claim 1 or 2,
characterized in that the measured values are monitored for compliance with specified boundary conditions and that when a first boundary condition (start condition) is met, the lamp is operated at a low operating frequency (start frequency) until a second boundary condition is met, whereupon the operating frequency is increased. Method according to claim 3,
characterized in that the operating frequency is increased continuously or preferably in discrete steps from the starting frequency after the starting condition is met, until a predetermined third boundary condition (termination condition) is reached. Method according to claim 3 or 4,
characterized in that the starting condition is considered to be fulfilled when a certain operating time is present or has been reached and / or the necessary operating voltage has risen to a predetermined value and / or the electrical distance has increased to a predetermined value. Method according to one of claims 3 to 5,
characterized in that the second boundary condition is considered to be fulfilled if the lamp has been operated at the starting frequency for a certain period of time or if no change can be ascertained over a predetermined period in the direct or indirect measurement of the electrode spacing. Method according to one of claims 4 to 6,
characterized in that the termination condition is considered to be fulfilled if a predetermined operating frequency (maximum frequency) has been reached or if the necessary operating voltage has dropped to a predetermined minimum value or if no change can be determined in the direct or indirect measurement of the electrode spacing over a predetermined period of time . Method according to one of claims 3 to 7,
characterized in that the start condition and start frequency is selected depending on the operating state Method according to one of claims 1 to 8,
characterized in that the selected operating frequencies are between about 40 and 600 Hz. Method according to one of claims 1 to 9, wherein the operating frequency is increased in discrete steps,
characterized in that the frequency is increased by approximately 1.2 and 1.8 times. Device for operating a gas discharge lamp with alternating voltage or alternating current in such a way that the instantaneous power of the lamp is increased at certain time intervals,
characterized in that measuring means are provided for the continuous or discontinuous measurement of the values of at least one operating date of the lamp changing over time and means for changing the frequency of the alternating voltage or alternating current (operating frequency) as a function of the measured values. Device according to claim 11,
characterized in that the measuring means are designed to measure the values of at least one operating date from the following group of operating data: total operating time of the lamp, operating voltage, output or absorbed power, arc length, electrode spacing. Device according to claim 11 or 12,
characterized in that at least one monitoring unit coupled to the means for changing the operating frequency is provided for monitoring the measured values for the fulfillment of predetermined or predeterminable boundary conditions. Device according to claim one of claims 11 to 13,
characterized in that a compact evaluation and control unit having at least one microprocessor is provided for controlling the operating frequency, the operating voltage and the alternating current supplied to the gas discharge lamp and for evaluating and monitoring the measured values for the fulfillment of predetermined or predeterminable boundary conditions. Device according to one of claims 11 to 14,
characterized in that lying between about 40 and 600 Hz frequencies of operation can be generated. Method for processing the electrodes of a gas discharge lamp while the lamp is in operation, the lamp being operated with alternating voltage or alternating current and the instantaneous power of the lamp being increased at certain time intervals,
characterized in that the frequency of the alternating voltage or alternating current (operating frequency) is changed in order to make targeted use of the transport of electrode material that occurs during operation of the lamp. A method according to claim 16,
characterized in that, starting from a certain starting frequency , the operating frequency is increased continuously or preferably in discrete steps until a predetermined boundary condition is met. Method according to one of claims 16 or 17,
characterized in that the operating frequencies are between about 40 and 600 Hz. Method according to one of claims 16 to 18,
characterized in that the operating frequency is preferably increased in discrete steps by approximately 1.2 and 1.8 times, respectively. Gas discharge lamp with two electrodes,
characterized in that the electrodes were processed by gradually increasing the frequency of the lamp operating current or the lamp operating voltage. A projector with a gas discharge lamp according to claim 20. Vehicle with a gas discharge lamp according to claim 20. Projector with a device for operating a gas discharge lamp according to a of claims 11 to 15. Vehicle with a device for operating a gas discharge lamp according to a of claims 11 to 15. Using the relationship D = a / f1 / 2 for machining an electrode of a gas discharge lamp during the pulsed operation of the lamp with an alternating current Frequency f, where D is the approximate diameter of one on the electrode when pulsed Operation growing structure, a lamp-specific, especially of electrode material and geometry-dependent constant of the unit [Meter Hertzl / 2] and f the Frequency is in Hertz. Machine-readable data carrier with a control program for controlling a Device for operating a gas discharge lamp containing machine-readable Instructions for performing a method according to any one of claims 1 to 10.

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