EP1722610B1 - Monitoring of the status of a discharge lamp filament - Google Patents

Abstract

The method involves heating of the filament (3,3') with a defined current simultaneously during the measurement of a parameter which directly or indirectly displays the temperature of the filament. Heat the filament with the second defined filament current different from the first filament current simultaneously with the measurement of the parameter. Which directly or indirectly display the temperature of the filament. Calculate the difference of temperature variation by heating with first and second filament current as parameters for the status of the filament. Independent claims are also included for the following: (A) Computer program product; and (B) Operating device for a lamp.

Description

The present invention relates to the field of lamps with heating coils, such as gas discharge lamps. More particularly, the invention relates to techniques for assessing the condition, in particular the aging state, of a heating coil of such a lamp.

For example, gas discharge lamps have heating coils coated with an emitter material such as BaO. As is known, such heating coils are heated prior to the ignition of the lamp and possibly also during lamp operation. The emitter material guarantees the emissivity of the heating coil during lamp operation. However, this emitter material is sputtered off the filament during lamp operating time. With increasing aging of the heating coil thus thus decreases the mass of the heating coil. On the other hand, since the heating coil is a main criterion for the life of the lamp as a whole, can be concluded by the determination of the filament mass on the remaining emitter material and thus indirectly on the expected life of the lamp.

The relationship between the remaining emitter mass and the expected service life of a lamp can, for example, be measured experimentally in advance in experimental series.

Out US 6,243,017 B1 It is known to determine the amount of the remaining active material of a cathode of a fluorescent lamp by measuring the cathode voltage loss. Optionally, then, depending on the detected amount of the remaining active material of the cathode, an alarm signal can be output.

From the US 6,538,448 B1 It is known to determine the remaining operating time of a fluorescent lamp as a function of a phase difference of a voltage at the cathode with respect to the current or voltage phase at another point of the fluorescent lamp.

Already from the US 2,664,543 It is known that the mass of a heating coil can be determined indirectly via their heat capacity.

• Die Messung des steilsten Anstiegs der Temperaturveränderung in der Heizphase setzt eine Präzision voraus, wie sie eben nur unter Laborbedingungen ausgeführt werden kann. Somit lässt sich das Verfahren von Wharmby kaum auf eine Durchführung in installierten Leuchten anwenden.
• Grund dafür ist, dass zur genauen Bestimmung des steilsten Anstiegs der Temperaturveränderung beispielsweise Parameter wie die Umgebungstemperatur bekannt sein müssen, was wiederum im eingebauten Zustand einer Lampe vor Ort nur schwer mit der notwendigen Präzision durchführbar ist.

The article of Wharmby 'Cathode heating rate and life prediction in fluorescent lamps', Light Sources 2004 . Proceedings of the Tenth International Symposium on the Science and Technology of Light Sources Toulouse, France, 18-22 July 2004 proposes now to heat to determine the heat capacity of a heating coil (and thus the mass of the heating coils) with an impressed heating current through helix and thereby measure exactly the resulting temperature change. As a parameter for the heat capacity of the cathode and thus for the remaining emitter material Wharmby suggests to use the maximum temporal change, ie the steepest increase in the temperature change in the heating phase. Whilst this procedure may be carried out under laboratory conditions according to Wharmby, it nevertheless has the following disadvantages:

• The measurement of the steepest increase in the temperature change in the heating phase requires a precision that can only be carried out under laboratory conditions. As a result, Wharmby's process is hardly applicable to the implementation of installed luminaires.
• The reason for this is that for the exact determination of the steepest rise in the temperature change, for example, parameters such as the ambient temperature must be known, which in turn is difficult to carry out with the necessary precision in the installed state of a lamp on site.

The invention has now set itself the task to improve such a method for indirect detection of the helical state on the heat capacity of the heating coil to the effect that it can be performed more efficiently and outside of laboratory conditions, especially in the installed state of the lamp.

Thus, while Wharmby's method of detecting defects, for example, can only be subsequently applied to the heating coil in the laboratory, the invention proposes a solution which, for example, automatically by an electronic ballast (ECG) as an example of a control gear for lamps with heating coils in the installed state can be carried out.

This object is achieved by the features of the independent claims. The dependent claims form the central idea of the invention in a particularly advantageous manner on.

According to a first aspect of the present invention, a method for assessing the state of a heating coil of a lamp is proposed, wherein first the heating coil is heated with a first defined heating current while measuring a parameter, the parameter directly or indirectly reflecting the temperature of the heating coil.

In a subsequent step, the heating coil is then heated, if necessary after cooling, with a second defined, different from the first heating current heating current and in turn measured the parameter that directly or indirectly reflects the temperature of the heating coil. As a parameter for the state of the heating coil, i. As a parameter for the remaining emitter material on the heating coil according to the invention, the difference in the temperature change speeds is used in the heating with the first and the second heating current.

According to another aspect of the present invention, in a first step, a heating current is used to heat the parameter, which directly or indirectly reflects the temperature of the heating coil. Subsequently, the same parameter is measured in a cooling phase. As a parameter for the state of the heating coil, the difference of the temperature change speeds during the heating phase or during the cooling phase is used.

The heating can be done in particular with an impressed constant current.

According to a further aspect of the present invention, the number of available data per heating cycle can be increased by optionally measuring the temperature change of a cooling phase in addition to a heating phase and evaluating this temperature change in the cooling phase as a parameter for the state of the heating coil.

The temperature of the heating coil can be detected in particular indirectly via the electrical resistance of the heating coil. For this purpose, if necessary, in the cooling phase with a minimum heating current 'to be heated' to continuously measure by means of this known minimum current and the voltage dropping at the heating coil electrical resistance.

The invention also relates to a computer software program product which executes such a method when running on a computing device or implemented in the form of hard-wiring.

In accordance with yet another aspect of the present invention, an operating device for heating coil lamps is provided, with an example of an electronic ballast (ECG) for gas discharge lamps. This operating device is designed to carry out a method of the type mentioned above.

The operating device can display the detected helical state, send a corresponding message and / or store the helical state in a memory for later analysis.

The message can be sent, for example, by a connected bus.

The control of a connected lamp can be carried out depending on the detected helix state, that is, when the aging of the heating coil, if necessary, the heating current increases ('run over') is.

The operating device may carry out the detection of the helical state, for example at periodic intervals, automatically or in response to a supplied command.

Fig. 1

zeigt eine schematische Ansicht eines erfindungsgemäßen Systems,

Fig. 2

zeigt eine Darstellung zur Erläuterung der Wärmeflüsse einer Heizwendel,

Fig. 3

zeigt Temperaturverläufe (Heizen und Abkühlen) für Heizwendeln mit unterschiedlicher Wärmekapazität, und

Fig. 4

zeigt ein mittels einer Messung gemäss Figur 3 erstelltes Diagramm, aus dem sich erfindungsgemäss die Massen zweier unterschiedlicher Heizwendeln ermitteln lässt.

Further features, advantages and features of the present invention will become apparent from the following detailed description of an embodiment with reference to the figures of the accompanying drawings.

Fig. 1

shows a schematic view of a system according to the invention,

Fig. 2

shows a representation for explaining the heat flows of a heating coil,

Fig. 3

shows temperature curves (heating and cooling) for heating coils with different heat capacity, and

Fig. 4

shows a diagram prepared by means of a measurement according to Figure 3, from which according to the invention the masses of two different heating coils can be determined.

Referring to Fig. 1, an operating device for lighting means with heating coils 3, 3 'is explained, which can apply the present invention.

Shown is an operating device 1, such as an electronic ballast (ECG) for gas discharge lamps 4, are connected to the light emitting means 4 with at least one heating coil 3, 3 '. In principle, the invention can be applied to all lamps with heating coils. A typical example is gas discharge lamps. The lighting means 4 with the at least one heating coil 3, 3 'are connected to a power output circuit 2 with the operating device 1.

The operating device 1 may have a control unit 5, which outputs necessary for the operation of the lighting means 4 drive signals. These control signals and possibly also incoming measuring signals can relate to different operating phases of the lighting means (preheat, start, operation, erase). In the meantime, however, only those functions are to be explained which the control unit 5 for carrying out the method according to the invention, i. to determine the aging state of the at least one heating coil can perform.

As shown schematically, the control unit 5 can for this purpose impress a constant heating current I _HSOLL as setpoint value of at least one connected heating coil 3. Furthermore, the control device 5 can be designed to detect the voltage U _H arising at the heating coil together with the actual current through the heating coil I _H , thus to calculate the current electrical resistance of the heating coil 3. For example, by means of a table (or also by means of an analytical function), the electrical resistance value, calculated using the aforementioned parameters, can then be converted into the current temperature of the relevant heating coil 3, 3 '.

The control device 5 is functionally connected to a memory 7 which, as shown by way of example in FIG. 1, can be received, for example, within the operating device 1. In the memory 7 different setpoints and measured actual values can be stored. With regard to the present invention, it is particularly relevant that the operating device 1 can store in the memory 7 parameters that represent one or more different aging states of a connected coil 3, 3 '. This memory 7 can be used for example for subsequent error analysis. Furthermore, the control device 5 depending on a detected state of the heating coils 3, 3 'change their control. In particular, the heating current can be increased if aging of the coil, i. a sputtering of emitter material on the coil was detected.

The detected helical state can continue to be visually displayed 6. This can be represented, for example, in the form of a display or a type of traffic light circuit, the display in each case reproducing which current aging state the heating coil 3, 3 'currently has.

Alternatively or additionally, a detected aging state of the helix and in particular a Inadmissible aging state of a helix via an interface 8 and a connected bus 9 wired or wireless, for example, are transmitted to a central point. Thus, for example, can be detected centrally in time, an impending failure of the lamp due to impermissible aging of the heating coil.

• Veränderung der Ansteuerung der Leuchtmittel, insbesondere der Heizwendeln, abhängig von dem erfassten Alterungszustand,
• Anzeige, beispielsweise optisch oder akustisch des Alterungszustands am Betriebsgerät selbst,
• Ablegen eines gemessenen Alterungszustands in einem Speicher, insbesondere zur nachträglichen Fehleranalyse, und/oder
• Aussendung einer Meldung betreffend den Alterungszustand der gemessenen Heizwendel.

It should be noted that the method described in more detail below according to the present invention for determining the state of a heating coil in a light source in the installed state of the lamp can be performed. In particular, an operating device 1 can periodically detect the state of the heating coil according to this method in order to evaluate it in one of the following ways:

• Change in the control of the lighting means, in particular the heating coils, depending on the detected state of aging,
• Display, for example visually or acoustically, of the aging state on the operating device itself,
• Storing a measured aging state in a memory, in particular for subsequent error analysis, and / or
• Transmission of a message regarding the state of aging of the measured heating coil.

Alternatively, or in addition to the periodic automatic measurement of the aging state of the heating coil by the operating device 1, such a measurement, for example, by a corresponding command of outside, for example via a connected bus line are triggered. For example, when using the well-known DALI standard, which allows a bidirectional communication between a control center and connected operating devices, thus the aging states of heating coils can be queried, which are present in connected to the bus lights.

Before describing a test method according to the invention for a heating coil, the physical principles of the temperature conditions of a heated coil are briefly explained.

wird die Wendel aufgeheizt. Dabei wird von der Wendel Energie in Form von Strahlung und Wärmeleitung an das Gas sowie in Form von Wärmeleitung über die Wendelanschlüsse abgegeben. Betrachtet man die Temperaturzunahme der Wendel über die Zeit, ergibt sich folgende Bilanzgleichung: $$\frac{d{T}_w}{dt}=\frac{P_{\mathit{in}}\left(T_w\right)-{\mathrm{\Phi }}_{\mathit{rad}}\left(T_w^4\right)-{\mathrm{\Phi }}_{\mathit{cond},G}\left(T_w\right)-{\mathrm{\Phi }}_{\mathit{cond},F}\left(T_w\right)}{m_{\mathit{Wo}}{C}_{\mathit{Wo}}-m_{\mathit{BaO}}{C}_{\mathit{BaO}}}$$

FIG. 2 diagrammatically shows a helix with the relevant physical variables. When heating a coil with the electric power $${\mathrm{P}}_{\mathrm{in}}\mathrm{=}{\mathrm{U}}_{\mathrm{H}}\mathrm{\cdot }{\mathrm{I}}_{\mathrm{H}}$$

the coil is heated up. In this case, energy is emitted by the helix in the form of radiation and heat conduction to the gas and in the form of heat conduction via the helical connections. Looking at the temperature increase of the helix over time, the following balance equation results: $$\frac{d{T}_w}{dt}=\frac{P_{\mathit{in}}\left(T_w\right)-{\mathrm{\Phi }}_{\mathit{wheel}}\left(T_w^4\right)-{\mathrm{\Phi }}_{\mathit{cond}.G}\left(T_w\right)-{\mathrm{\Phi }}_{\mathit{cond}.F}\left(T_w\right)}{m_{\mathit{Where}}{C}_{\mathit{Where}}-m_{\mathit{BaO}}{C}_{\mathit{BaO}}}$$

den über Strahlung abgegebenen Wärmefluss. Weiteres tritt Wärmeleitung in Form von Wärmeleitung an das Lampengas mit $${\mathrm{\Phi }}_{\mathit{cond},G}\left(T_w\right)=\frac{T_w-T_G}{R_{\mathit{th},G}}$$

und Wärmeleitung an die Wendelanschlüsse auf, was durch den folgenden Term ausgedrückt werden kann: $${\mathrm{\Phi }}_{\mathit{cond},F}\left(T_w\right)=\frac{T_w-T_F}{R_{\mathit{th},F}}$$

Where the term denotes $${\mathrm{\Phi }}_{\mathit{wheel}}\left(T_w\right)=\mathit{\epsilon \sigma }{A}_{\mathit{wheel}}\left(T_w^4-{\mathrm{<figure-callout\; id="4"\; label="T\; G"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">T\; </figure-callout>}}_G^{}\right)$$

the radiation emitted by radiation heat flow. Further occurs heat conduction in the form of heat conduction to the lamp gas $${\mathrm{\Phi }}_{\mathit{cond}.G}\left(T_w\right)=\frac{T_w-T_G}{R_{\mathit{th}.G}}$$

and heat conduction to the helical connections, which can be expressed by the following term: $${\mathrm{\Phi }}_{\mathit{cond}.F}\left(T_w\right)=\frac{T_w-T_F}{R_{\mathit{th}.F}}$$

In principle, different approaches are conceivable for carrying out the measurement of the temperature profile during heating. The heating of the helix is preferably carried out with constant current (however, the invention also encompasses time-varying heating currents). When heating with constant current results for the impressed electrical power with the temperature dependence of the specific electrical resistance $$P_{\mathit{in}}\left(T_w\right)=I_{\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">H</figure-callout>}}^{2}R\left(T_w\right)=I_{\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">H</figure-callout>}}^2{R}_{w.0}\lfloor 1+\mathit{\alpha }\left(T_w-T_G\right)+\mathit{\beta }{\left(T_w-{\mathrm{<figure-callout\; id="2"\; label="T\; G"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">T\; </figure-callout>}}_G\right)}^2\rfloor$$

The physical relationship between emitter mass and rate of temperature increase is given in relation 1.1 above. (According to the known technique of D. Wharmby, the maximum velocity is used as parameter for the emitter ground, which corresponds to the first derivative of the relation 1.1).

According to one aspect of the invention, it is proposed to use as the parameter for the emitter ground the difference in the To use rates of temperature increase from two measurements with different impressed powers. Then results: $$\frac{d{T}_w\left(P_1\right)}{dt}\frac{d{T}_w\left(P_2\right)}{dt}=\frac{P_{\mathit{in}}^1-{\mathrm{\Phi }}_{\mathit{wheel}}^1-{\mathrm{\Phi }}_{\mathit{cond}\mathit{.}\mathit{G}}^1-{\mathrm{\Phi }}_{\mathit{cond}\mathit{.}\mathit{F}}^1-\left(P_{\mathit{in}}^2-{\mathrm{\Phi }}_{\mathit{wheel}}^2-{\mathrm{\Phi }}_{\mathit{cond}\mathit{.}\mathit{G}}^2-{\mathrm{\Phi }}_{\mathit{cond}\mathit{.}\mathit{F}}^2\right)}{m_{\mathit{Where}}{C}_{\mathit{Where}}-m_{\mathit{BaO}}{C}_{\mathit{BaO}}}$$

Assuming that the measurements are feasible with negligible increase in ambient temperatures (this may be assumed if the measurements can be made sufficiently fast), then the heat flows from the filament are the same for different impressed powers at a given filament temperature.

This means that these unknowns cancel each other out when determining the emitter mass. This leads to the relationship $$\frac{d{T}_w\left(P_{\mathit{in}.1},,T_w\right)}{dt}\frac{d{T}_w\left(P_{\mathit{in}.2},,T_w\right)}{dt}=\frac{P_{\mathit{in}.2}-P_{\mathit{in}.2}}{m_{\mathit{Where}}{C}_{\mathit{Where}}-m_{\mathit{BaO}}{C}_{\mathit{BaO}}}$$

der die Differenz der Geschwindigkeiten der Temperaturveränderungen aus zwei Messungen mit unterschiedlich eingeprägten Leistungen wiedergibt, ist dann die Messgröße, die der Emittermasse proportional ist.The parameter $$\mathrm{\Delta }\left(\frac{d{T}_w}{dt}\right)=\frac{d{T}_w\left(P_{\mathit{in}.1},,T_w\right)}{dt}-\frac{d{T}_w\left(P_{\mathit{in}.2},,T_w\right)}{dt}$$

which reproduces the difference in the speeds of the temperature changes from two measurements with differently impressed powers is then the measured variable which is proportional to the emitter mass.

Then (1.7) results in subtraction at the same resistance or same spiral temperature: $$\mathrm{\Delta }\left(\frac{d{T}_w}{dt}\right)=\frac{\left(I_{H.\mathit{high}}^2-I_{H.\mathit{low}}^2\right)\cdot R_{w.0}\lfloor 1+\mathit{\alpha }\left(T_w-T_G\right)+\mathit{\beta }{\left(T_w-{\mathrm{<figure-callout\; id="2"\; label="T\; G"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">T\; </figure-callout>}}_G\right)}^2\rfloor }{m_{\mathit{Where}}{C}_{\mathit{Where}}-m_{\mathit{BaO}}{C}_{\mathit{BaO}}}$$

This means that the difference of the resistance changes can be determined for each resistance value. This can be transferred to a diagram like FIG. 4, which represents this gradient for an emitter mass of 100% (= new helix) or 10% (= aged helix). The gradient (slope) of this curve is proportional to the mass assignment of the filament with emitter. Figure 4 is for illustration only; The control unit calculates, for example, the mean slope and takes this value as a parameter representing the helical state.

1. 1. Da durch die Wahl des "richtigen" Parameters die kritischen Unbekannten (bpsw. Umgebungstemperatur) herausfallen, ist die Genauigkeit der Messung der Emittermasse (verglichen mit der Methode von Wharmby) potentiell höher.
2. 2. Es können mehr Messpunkte aus der Einzelmessung zur Bestimmung des Parameters herangezogen werden. Dies führt zu genaueren und kürzeren Messzyklen. Eventuell genügt eine einzige Messung, d.h. ein einziger Heiz-/Abkühlzyklus.
3. 3. Die Messungen können daher von einem Betriebsgerät im eingebauten Zustand der Leuchte, bspw. selbsttätig oder auf einen empfangenen Befehl hin, ausgeführt werden.

Advantages of the invention:

1. 1. Since selecting the "right" parameter drops out the critical unknowns (bpsw ambient temperature), the accuracy of the emitter mass measurement (compared to the Wharmby method) is potentially higher.
2. 2. More measuring points from the single measurement can be used to determine the parameter. This leads to more accurate and shorter measurement cycles. Eventually, a single measurement, ie a single heating / cooling cycle, will suffice.
3. 3. The measurements can therefore be of an operating device in the installed state of the lamp, for example. Automatically or upon a received command.

Claims (13)

1. Method of assessing the condition of a heating coil of a lamp,
   wherein the method has the following steps:

   - heating the heating coil with a first defined heating current with simultaneous measurement of a parameter which directly or indirectly represents the temperature of the heating coil,

   - in a step following upon this, heating the heating coil with a second defined heating current, different from the first heating current, again with simultaneous measurement of a parameter which directly or indirectly represents the temperature of the heating coil, and

   - calculation of the difference of the rates of change of temperature upon heating with the first and the second heating current as parameter for the condition of the heating coil.
2. Method of assessing the condition of a heating coil of a lamp,
   wherein the method has the following steps:

   - heating the heating coil with a first defined heating current with simultaneous measurement of a parameter which directly or indirectly represents the temperature of the heating coil,

   - in a step following upon this, measuring the parameter which directly or indirectly represents the temperature of the heating coil, in a cooling phase, and

   - calculation of the difference of the rates of change of temperature upon heating with the first heating current and during the cooling phase.
3. Method in accordance with any preceding claim, in which the heating is effected with an impressed constant current.
4. Method in accordance with any preceding claim, in which the temperature of the heating coil is detected indirectly via the electrical resistance of the heating coil.
5. Computer software programme product,
   which executes a method in accordance with any preceding claim when it runs on a computer device.
6. Operating device for lamps with heating coils, in particular electronic ballast (EVG) for gas-discharge lamps,
   which is programmed to execute a method in accordance with any of claims 1 to 4.
7. Operating device according to claim 6,
   characterised in that,
   it is programmed to indicate the detected coil condition, to send a corresponding report and/or store this in a memory.
8. Operating device according to any of claims 6 or 7,
   characterised in that,
   it is programmed to send the report via a connected bus.
9. Operating device according to any of claims 6 to 8,
   characterised in that,
   it is programmed to execute control of a connected lamp in dependence upon the detected coil condition.
10. Operating device according to any of claims 6 to 9,
    characterised in that,
    it carries out the detection of the coil condition automatically or in response to a command.
11. Operating device for lamps with heating coils according to any of claims 6 to 10,
    characterised in that,
    it has a control unit which automatically or in response to a received command carries out a test of the condition of a heating coil of a connected lamp.
12. Operating device according to claim 11,
    characterised in that,
    the control unit evaluates as follows a parameter which represents the coil condition:

    - storing in a memory,

    - control of the lamp depending on the detected Coil condition, and/or

    - indication or report of the coil condition, in particular a critical coil condition which gives reason to fear a failure in the near future.
13. Operating device according to claim 11 or 12,
    characterised in that,
    it sends the report via a connected bus.

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