WO2012109687A1

WO2012109687A1 - Method for detecting a rectifier effect for a dimmable gas discharge lamp

Info

Publication number: WO2012109687A1
Application number: PCT/AT2012/000035
Authority: WO
Inventors: Daniel Salzmann
Original assignee: Tridonic Gmbh & Co. Kg
Priority date: 2011-02-18
Filing date: 2012-02-20
Publication date: 2012-08-23
Also published as: DE102011004351A1

Abstract

The invention relates to a method for detecting a rectifier effect for a dimmable gas discharge lamp (L), wherein the rectifier effect is detected by comparing a measurement signal (M) fed back from the load circuit (L, C1, C2, R2, R3, R4, L) containing the gas discharge lamp (1) with a reference value (PREF), wherein the reference value (PREF) is adjusted as a discrete or continuous function depending on a parameter that directly or indirectly represents the dimming value (D) of the gas discharge lamp (L).

Description

Method for detecting a rectifier effect in a dimmable gas discharge lamp

During operation of gas discharge lamps, the emitter material at the electrodes is consumed. At the end of lamp life, the emitter of the filament is consumed. This has the consequence that the exit energy of the electrons is increased. Since the operating devices for gas discharge lamps act as a constant current source, the increased voltage drop (also referred to as "cathode drop") results in an increase in power, which leads to an increase in the surface temperature to that in the region of the electrodes As a result of the mentioned voltage drop, ions accelerate and strike the gas from the gas in the direction of the helix, resulting in the risk of melting the lamp socket end of life), ie they turn off the lamp as it approaches the end of its life, before the risk described above becomes reality.

The above-described cathode case mostly occurs on a helix first and results in a rectifier effect. This means that although the lamp is operated with AC voltage, a DC component can still be detected in a measuring signal derived from the load circuit of the lamp. By detecting this DC component, a reliable shutdown of the lamp can be ensured at the right time. For the EoL shutdown of gas discharge lamps, there are standard provisions, which are specified in section 17 of DIN EN 61347-2-3.

The subject of recognition of the rectifier effect is also dealt with by EP 1 066 739 B1 and WO 2008/116561 A9.

However, the previous proposals are limited to the case that the gas discharge lamps work at full power, ie in the undimmed state. It is understood, however, that an EoL shutdown u. It may not or must be done later, when the lamp with reduced power so in dimmed state works. The invention is therefore based on the object of specifying EoL shutdown rules for dimmable gas discharge lamps.

To achieve the object, it is proposed for a dimmable gas discharge lamp according to the independent claim 1 to make the rectifier effect recognizable by comparing a measuring signal fed back from the load circuit containing the gas discharge lamp with a reference value,

wherein the reference value is set as a discrete or continuous function depending on a parameter directly or indirectly representing the dimming value of the gas discharge lamp.

It can be concluded that an existing rectifier effect if the measurement signal exceeds the reference value, and wherein the reference value for the ratio DC component / total lamp voltage is selected to be higher the lower the dimming value. The reference value function may preferably have a curve profile obtained by interpolation of measured reference values.

To solve the problem, a method for operating a gas discharge lamp with EoL shutdown is also proposed according to independent claim 5,

in which an AC operating voltage is supplied to the lamp,

in which a measurement signal is derived from the lamp voltage, the lamp current or the lamp power, which contains a corresponding DC component, if a rectifier effect occurs in the lamp,

in which a DC component signal is obtained from the measurement signal,

in which the DC component signal is compared with a stored reference signal which, depending on the respective dimming value, corresponds to an admissible limit value for the DC component signals, and

where the lamp is turned off when the DC

Share signal deviates in a predetermined manner from the reference signal.

The reference signals can be used as a table of discrete individual reference values or as the discrete ones

Single reference values formed staircase function or as a non-continuous function in which the individual Reference values are connected by respective straight line sections, or stored as a continuous function of continuously successive reference values.

In this case, the straight-line sections of the non-continuous function can be determined by interpolation of the limiting individual reference values.

The individual reference values or the function formed by them are expediently chosen such that a reference value corresponding to a higher dimming value is greater than or equal to a reference value corresponding to a lower dimming value.

To solve the problem, an operating device for a gas discharge lamp with EoL function according to the independent claim 9 is also proposed,

full

Means for generating an AC supply voltage for the lamp,

Means which are connected to a load circuit enclosing the lamp and serve to generate a measurement signal which corresponds to the lamp current of the lamp voltage or the lamp power,

Means for evaluating the measurement signal and for generating a DC component signal which corresponds to the DC component in the lamp current, the lamp voltage or the lamp power, which is caused by a rectifier effect, Storage means for reference values representing maximum permitted values for the DC component signals as a function of the respective dimming values, and

Means for comparing a reference value corresponding to the current dimming value of the lamp with the currently generated DC component signal and for switching off the lamp when the DC component signal deviates in a predetermined manner from the reference value. The storage means may be connected to a bus delivering the dimming values.

The reference value can additionally be selected depending on the type of the connected gas discharge lamp.

The reference values stored in the storage means can be individual values which correspond to certain spaced dimming values and form a staircase function. Alternatively, the reference values may also form a non-continuous function dependent on the dimming values, which consists of straight line sections,

wherein each straight line section extends between in each case two individual reference values,

where the individual reference values correspond to spaced dimming values, and

wherein the straight line sections have been obtained by interpolation of the limiting single reference values. Other refinement features are the subject of the dependent claims, which are intended to be exhaustive in describing the description. An embodiment will be described below with reference to the drawings. Show it

1 is a schematic block diagram of a gas discharge lamp with detection of the rectifier effect and EoL shutdown,

FIG. 2 shows a graphical representation of the reference values as a function of the dimming values.

In FIG. 1, a gas discharge lamp L is operated with a high-frequency AC voltage U _A c. This is generated from an operating voltage U _D c by means of a switch half bridge 1. The operating voltage U _D c is generated for example by rectification of the mains voltage. The rectifier is not shown here.

The switch half-bridge 1 consists of two series-connected electronic switch elements Sl, S2 in the form of FETs. The two switch elements Sl and S2 are connected as a series circuit together with a resistor Rl between the positive terminal + U _D c and ground. The two switch elements Sl and S2 are switched in a push-pull by a control unit 3 conductive and non-conductive. This produces at the bridge point between the two switch elements Sl and S2 required for the operation of the gas discharge lamp L high-frequency

AC voltage. This is supplied to a series resonant circuit consisting of a resonance inductance L and a Resonance capacitor Cl consists. The series resonant circuit L, Cl is guided from the bridge point of the switch half-bridge 1 to ground. The frequency with which the two switch elements Sl, S2 are alternately opened and closed, is close to the resonance frequency of the series resonant circuit L, Cl, which is formed at the resonance inductance L, but especially at the resonant capacitor Cl an excessive resonance voltage, the Ignition and subsequent operation of the gas discharge lamp L is suitable.

The excessive resonant voltage occurring across the resonant capacitor C1 is supplied via a coupling capacitor C2 of the one electrode of the gas discharge lamp L, whose other electrode is grounded via a shunt resistor R4 (current measuring resistor). The lamp current I _L flowing through the shunt resistor R4 causes a voltage drop at the shunt resistor R4, which is supplied as an actual value signal S to a control unit 3 controlling the switch elements S1 and S2.

In parallel with the series connection of the gas discharge lamp L and the shunt resistor R4 is also a voltage divider, which is formed by two resistors R2 and R3. The voltage drop across the voltage divider R2, R3 corresponds to the AC lamp voltage υ _Αα . The voltage R3 of this voltage is _fed as measurement signal M to the control unit 3 on the one hand and to a DC evaluation circuit part 5 on the other hand. Towards the end of its lifetime, one electrode of the gas discharge lamp L wears off more than the other. This results in a rectifier effect, which manifests itself in that the measurement signal M contains a DC component. This is detected by the DC evaluation circuit part 5. At the output of the DC-Auswertungs- circuit part is formed in this way a DC share signal P _D c- This signal is a power value, which is indicated in watts.

The control unit 3 is connected to a bus, preferably a DALI bus. Via the DALI bus, digital dimming signals D (not shown) are transmitted to the control unit 3. The dimming signals D are formed by eight bits. The eight bits defining a number between 0 and 256 yields.

If there is no dimming, then the dimming value D corresponds to the maximum number 2 ⁸ = 256. In this case, the lamp L operates at full power and maximum brightness. The greatest possible dimming is when the dimming value D reaches about 85. The greatest possible dimming leads to the lowest possible brightness with the L lamp. That's the brightness that you just have not extinguished.

The control unit evaluates the dimming values D by changing the repetition frequency of the switching signals for the two switch elements Sl and S2 and / or the pulse width representing the switch-on duration. The further the repetition frequency of the resonance frequency of the Series resonant circuit L, Cl deviates, the lower is the excessive voltage across the resonant capacitor Cl and thus the lamp L supplied for operation AC voltage U _AC and thus the lamp L made available power. The same applies to a lower duty cycle of the switch elements Sl and S2.

However, the dimming values D sent by the control center via the bus are also fed to an EoL reference value memory 6. In this memory, reference values P _REF corresponding to the dimming values are stored, either in the form of a table or a function curve. Each reference value P _REF represents a maximum permissible value for a DC component value P _D c at a certain dimming value.

FIG. 2 shows two possibilities for a function curve. It can be seen that numerical values corresponding to dimming values D are plotted on the abscissa. The numbers are between 85 and 256. The ordinate plots reference values P _REF in watts. The reference values P _D c are between ^" o and 60 W. In each case, corresponding reference values P _REF in watt are entered for discrete dimming values D, which are each spaced 15 watts apart.

The corner points of the staircase function are additionally connected by straight line sections with which the areas between the corner points have been bridged by extrapolation.

For a specific value of a DC component signal P _D cr, which is dependent on the respective dimming value, that of the DC evaluation signal Output circuit part 5, appears at the output of the EoL reference value memory 6, a corresponding also dependent on the current dimming value reference signal PREF · Both

Signals are compared in a turn-off comparator 4 with each other. When the numerical value in watts of the DC component signal P _D c exceeds the numerical value of the reference signal P _REF in watts, the turn-off comparator 4 causes the control unit 3 to turn off the lamp.

In the curves shown in FIG. 2, the higher the dimming value, or the smaller the numerical value representing the dimming value, the higher are the reference values P _REF in watts. The higher the dimming value, the lower the power with which the lamp L is operated. Accordingly, the risk of overheating of the electrodes is less than when the lamp is operated at full power. This, in turn, makes it possible to allow a higher DC component in the lamp voltage, the lamp current or the lamp power at lower lamp power.

In the case of the stepped curve shown in FIG. 2, it can not be ruled out that the shutdown occurs too early or too late due to tolerances of the lamp voltage divider R2 / R3 or the lamp L. This problem can no longer occur with the interpolated curve.

Also, it is thus possible by the invention to use non-linear functions as curves the reference values P _REF . In this way, an improved fault shutdown and a higher reliability for the operation of the gas discharge lamp is given. This is This is particularly important because the gas discharge lamp has a non-linear characteristic and the characteristic values of the gas discharge lamp can change in the case of different operating conditions. This may just occur in the ^'operating at very low dimming levels.

Several curves for the reference values P _REF for different types of gas discharge lamps may also be stored in the EoL reference value memory 6. In this way, depending on the type of the connected gas discharge lamp, the corresponding reference values P _RE F can be selected as a function of the dimming value and the lamp type. The type of the connected gas discharge lamp can be carried out, for example, by means of a helix identification or a measurement of the power characteristic of the connected gas discharge lamp. For example, such a determination of the type of gas discharge lamp may be made at each restart or after each lamp replacement. In this way, an adaptation of the permissible DC component to the actual actual power of the gas discharge lamp is to be allowed in accordance with the dimming value. Thus, the reference value (PREF) can additionally be selected depending on the type of the connected gas discharge lamp.

The DC component can be determined, for example, by supplying the measurement signal M to the DC evaluation circuit part 5. Within the DC evaluation

Circuit parts 5, the measurement signal M of it with a reference voltage Vref (not shown) compared. The result of the comparison is supplied to a duty cycle evaluation unit, which is a system clock is clocked. The duty cycle can be determined, for example, by providing a digital counter which, for example, counts downwards in the case of a measuring signal M which is smaller than the reference voltage Vref and counts upwards in the case of a measuring signal M which is greater than the reference voltage Vref. At the end of a period of activation of the switch half-bridge 1, then the deviation of the count from its output level is a measure of the DC component of the lamp voltage. Such a determination of the DC component can also take place over several periods of the control of the switch half-bridge 1. Thus, an evaluation and a comparison of the positive and negative half-wave of the lamp voltage to each other to determine the DC component.

However, the DC component can also be effected, for example, by comparing the positive and the negative peak value of the lamp voltage or by integrating the lamp voltage over one or more periods of the activation of the switch half-bridge 1.

Claims

Claims :

Method for detecting a rectifier effect in the case of a dimmable gas lamp operated with an AC voltage (L),

wherein the rectifier effect is detected by a feedback from the load circuit (L, C1, C2, R2, R3, R4, L), which contains the gas discharge lamp (L)

Measuring signal (M) is compared with a reference value (P _REF ),

wherein the reference value (P _REF ) as a discrete or continuous function depending on a dimming value (D) of the

Gas discharge lamp (L) directly or indirectly

setting parameter is set.

Method according to claim 1,

wherein the measurement signal (M) the DC component of

Lamp voltage absolute or normalized to the

Total _{lamp voltage} (U _ÄC ).

The method of claim 2, wherein it is concluded that an existing rectifier effect when the measurement signal (M) exceeds the reference value (P _REF ), and wherein the reference value (P _REF ) for the ratio DC component / total lamp voltage, the higher, the lower the dimming value (D) is.

Method according to one of the preceding claims, wherein the reference value function has a curve obtained by interpolation of measured supporting values. Method for operating a gas discharge lamp with EoL cut-off,

in which an AC operating voltage (U _A c) is supplied to the lamp (L),

in which a measurement signal (M) is derived from the lamp voltage, the lamp current or the lamp power, which contains a corresponding DC component if the lamp experiences a rectifier effect in which a DC component signal (PDC) results from the measurement signal (M) is won,

in which the DC component signal (PDC) is compared with a stored reference signal (PREF) which, depending on the respective dimming value (D), reaches a permissible limit value for the DC

Proportional signals (PDC), and

wherein the lamp (L) is turned off when the DC component signal (PDC) deviates in a predetermined manner from the reference signal (PREF).

Method according to claim 5,

where the reference signals (P _RE F)

as a table of discrete single reference values

or

as a step function formed from the discrete single reference values

or

as a non-continuous function in which the individual reference values are connected by corresponding straight line sections,

or

as a continuous function of continuously successive reference values

is stored. Method according to claim 5 or 6,

^• in which the straight line sections of the non-continuous function are determined by interpolation of the limiting individual reference values.

Method according to claim 6 or 7,

in which the individual reference values or the function formed by them are selected such that a reference value (P _REF ) corresponding to a higher dimming value (D) is greater than or equal to a reference value (P _REF ) corresponding to a lower dimming value (D).

Method for EoL disconnection of a gas discharge lamp (L) operated with an AC operating voltage, in which it is determined whether and at what level a measurement signal derived from a lamp parameter, such as one or more of lamp voltage, lamp current or lamp power, has a DC Proportion in which the DC component has a reference value (P _REF )

is compared and the lamp (L) is turned off when the DC component in a predetermined manner of the

Reference value (PREF) deviates, and

in which a plurality of reference values (P _REF ) are set for different dimming values (D), wherein a reference value for a higher dimming value is greater than a reference value for a lower dimming value.

10. Operating device for a gas discharge lamp with EoL function, comprising

Means (U _D c _/ S 1, S 2, R 1) for generating an AC supply voltage for the lamp (L),

Means (R2, R3) connected to a load circuit (L, C1, C2, R4, L) enclosing the lamp (L) and serving to generate a measuring signal (M) corresponding to the lamp current (I _L ) of the lamp voltage ( U _A c) or corresponds to the lamp power,

Means (5) for evaluating the measurement signal (M) and for generating a DC component signal (PDC) which corresponds to the DC component in the lamp current (I _L ), the lamp voltage (U _A c) or the lamp power caused by a rectifier effect,

Reference value storage means (6) (PREF) which, depending on the respective dimming values (D), represent allowable maximum values for the DC component signals (P _DC ),

Means (4) for comparing a reference value (PREF) corresponding to the current dimming value (D) of the lamp (L) with the currently generated DC component signal (PDC) and for switching off the lamp (L) if the DC component signal (PDC) deviates in a predetermined manner from the reference value (PREF).

11. Operating device according to claim 10,

in which the storage means (6) are connected to a bus (2) supplying the dimming values (D).

12. Operating device according to claim 10 or 11, wherein the reference values (PREF) is additionally selected depending on the type of the connected gas discharge lamp.

13. Operating device according to claim 10, 11 or 12,

in which the reference values (PREF) stored in the memory means (6) are individual values which correspond to certain spaced dimming values (D) and form a step function.

14. Operating device according to claim 10, 11 or 12,

in which the reference values (PREF) form a non-continuous function which is dependent on the dimming values (D) and which consists of straight line sections,

in which each straight line section extends between in each case two individual reference values (PREF),

wherein the individual reference values (PREF) correspond to certain spaced dimming values (D), and

in which the straight line sections have been obtained by interpolation of the limiting individual reference values (PREF).