EP2274960B1 - Method and circuit arrangement for operating at least one discharge lamp - Google Patents

Description

Technical area

The present invention relates to a method for operating at least one discharge lamp on a circuit arrangement having an input with a first and a second input terminal for connecting a DC supply voltage, an output with at least a first and a second output terminal for connecting the at least one discharge lamp, an inverter with at least a first and a second electronic switch coupled in series between the first and second input terminals, wherein a center of the inverter is formed between the first and second switches, an ignition device comprising a lamp choke and a resonance capacitor, a preheater, which comprises the series connection of a primary inductance, a third electronic switch and a current measuring resistor, which is coupled between the center of the inverter and the second input terminal, as well as a first and a second secondary inductance coupled to the primary winding, wherein the first secondary inductance is coupled to the first output terminal and the second secondary inductance is coupled to the second output terminal, a control device coupled to the current measuring resistor, in which at least two different types of operating parameter sets assigned to different discharge lamps are stored, wherein an operating parameter set is a current operating parameter set wherein the control device is designed to control at least the first, the second and the third electronic switches according to the current operating parameter set, wherein in the preheating phase a first value of the voltage drop over the voltage correlated with the reciprocal of the electrical resistance of at least one coil of the at least one discharge lamp Current measuring resistor is determined at a first time and a second value of the voltage drop across the current measuring resistor correlated with the reciprocal of the electrical resistance of the at least one coil of the at least one discharge lamp at a second time, wherein the second time is after the first time. It also relates to a corresponding circuit arrangement for operating at least one discharge lamp.

State of the art

Such a circuit arrangement is known from the DE 103 45 610 A1 and is to facilitate understanding in Fig. 1 shown. This shows a circuit arrangement with two field effect transistors T1, T2, which are arranged in the manner of a half-bridge inverter. Both field effect transistors receive their control signal from a microcontroller MC. Parallel to the DC voltage input of the half-bridge inverter T1, T2, a DC link capacitor C1 is arranged with a comparatively large capacity. The intermediate circuit capacitor C1 serves as a DC voltage source and provides the so-called intermediate _circuit voltage U _Zw for the half-bridge inverter. The intermediate _circuit voltage U _Zw is usually about 400 V and is from the Mains AC voltage generated by a mains voltage rectifier (not shown) and a boost converter (not shown). The DC link capacitor C1 is arranged parallel to the voltage output of the boost converter. Connected to the output M of the half-bridge inverter is a load circuit formed as a series resonant circuit, which essentially consists of the lamp inductor L1 and the ignition capacitor C2. Parallel to the ignition capacitor C2, the discharge path of the fluorescent lamp LP and the capacitor C3 are connected, which is charged during operation of the lamp in the steady state of the half-bridge inverter to half the supply voltage of the half-bridge inverter. The lamp electrodes E1, E2 of the fluorescent lamp LP are formed as electrode filaments each having two electrical terminals. Parallel to the electrode coils E1, E2, a secondary winding SI1, SI2 of a transformer is in each case connected, which serves for the inductive heating of the electrode filaments E1, E2. The primary winding P1 of this transformer is connected in series with the switching path of a further field effect transistor T3, whose control electrode is also acted upon by the microcontroller MC with control signals, and a measuring resistor R1, wherein above the measuring resistor R1, a voltage Res decreases, with the reciprocal of the electrical Resistance of a helix E1, E2 of the discharge lamp LP is correlated. The series circuit of the components P1, T3 and R1 is connected to the output M of the half-bridge inverter. A first terminal of the primary winding P1 is connected to the output or center tap M of the half-bridge inverter and to the lamp inductor L1, while the second Terminal of the primary winding P1 is connected to the field effect transistor T3 and DC in the forward direction via a diode D1 to the high potential terminal (+) of the DC link capacitor C1. A first terminal of the measuring resistor R1 is connected to the ground potential (-), while the second terminal of the measuring resistor is connected to the field effect transistor T3 and via a low-pass filter R2, C4 to the voltage input A of the microcontroller MC.

By means of half-voltage supply of the half-bridge inverter charged coupling capacitor C3 and the alternating switching transistors T1, T2 of the half-bridge inverter, the load circuit L1, C2, LP acted upon in a known manner with a high-frequency AC voltage whose frequency is determined by the switching clock of the transistors T1, T2 and in the range of about 50 kHz to about 150 kHz. Before igniting the gas discharge in the fluorescent lamp LB whose lamp electrodes E1, E2 are inductively acted upon by means of the transformer P1, SI1, SI2 with a heating current. For this purpose, the transistor T3 is turned on and off by the microcontroller MC in synchronism with the transistor T1. During the turn-on of the transistors T1, T3 therefore flows through the primary winding P1 and the measuring resistor R1, a current. During the turn-off of the transistors T1, T3, the current flow through the measuring resistor R1 is interrupted. The stored in the magnetic field of the primary winding P1 energy is supplied during the turn-off of the transistors T1, T3 and the duty cycle of the transistor T2 via the diode D1 to the DC link capacitor C1. Due to the alternating switching transistors T1, T2 and of the transistor T3 switching in synchronism with the transistor T1, a high-frequency current flows through the primary winding P1 and induces corresponding heating currents for the electrode filaments E1, E2 in the secondary windings SI1, SI2. By means of the low-pass filter R2, C4, the voltage drop across the measuring resistor R1 is averaged over a time interval of a plurality of switching cycles of the transistor T3 and supplied to the voltage input A of the microcontroller MC. The input voltage at terminal A of the microcontroller MC is converted by means of an analog-to-digital converter into a digital signal and evaluated in the microcontroller MC.

The microcontroller MC detects the voltage drop across the capacitor C4 the first time after about 30 ms after the start of the heating phase and the second time about 600 ms after the start of the heating phase. If the absolute value of the difference of the two voltage values exceeds a predetermined threshold value, the voltage value at the end of the heating phase is compared with a reference value stored in the microcontroller MC and used for lamp type detection. Here, the voltage value, as mentioned, correlates with the inverse of the coil resistance. If the absolute value of the difference between the two voltage values lies below the threshold value, the lamp is still operated with the current data record, ie no lamp type recognition is performed. The latter is according to the cited document the case when the electrode filaments E1, E2 were not completely cooled at the beginning of the heating phase due to the last lamp operation, or if the circuit arrangement with a dummy ohmic resistor instead of the electrode filaments E1 or E2 of the fluorescent lamp LP is operated.

According to a further prior art, which is used by the applicant in already distributed circuit arrangements, is based on the prior art according to the DE 103 45 610 A1 made a further evaluation of the measured helical resistors, as related to Fig. 2 is shown. The aim of this approach is the detection of one or more Wendelkurzschlüsse by miswiring of the lamp in electronic circuitry. By this procedure is to be avoided that it comes in operation to spiral blackening or damage to the circuit arrangement.

gegen einen Schwellwert X1 verglichen, wobei Res2neu den aktuell gemessenen Wert des Spannungsabfalls am Messwiderstand R1 darstellt und Res2alt den Wert der vorangegangenen Messung. Liegt der Wert des Absolutbetrags $\left|\frac{\mathrm{Re}s2\mathit{neu}}{\mathrm{Re}s2\mathit{alt}}-1\right|$

unter der Schwelle X1, wird die Lampe im Schritt 160 mit dem aktuellen Betriebsparametersatz betrieben. Der neue Wert Res2neu unterscheidet sich nur sehr wenig von dem alten Wert Res2alt, so dass zweifelsfrei dieselbe Lampe an der Schaltungsanordnung angeschlossen ist. Deshalb kann diese im Schritt 160 unverändert mit dem aktuellen Datensatz betrieben werden. Liegt hingegen der Wert von $\left|\frac{\mathrm{Re}s2\mathit{neu}}{\mathrm{Re}s2\mathit{alt}}-1\right|$

über der Schwelle X1, wird im Schritt 170 bestimmt, ob der Wert $\left|\frac{\mathrm{Re}s2\mathit{neu}}{\mathrm{Re}s2\mathit{alt}}-1\right|$

zwischen der Schwelle X1 und einer Schwelle X2 liegt, wobei X2 größer als X1 ist. Ist dies zu bejahen, wird davon ausgegangen, dass es sich weiterhin um dieselbe Lampe handelt, diese nur etwas gealtert ist. Daher wird im Schritt 180 der alte Wert Res2alt durch den neuen Wert Res2neu überschrieben. Die Lampe wird danach im Schritt 190 weiterhin mit dem aktuellen Datensatz betrieben.In step 100, the known method starts. Subsequently, in step 110, it is checked whether the intermediate _{circuit voltage} U _{Zw has reached} its setpoint value U _Zwsoll . If this is not the case, the intermediate _{circuit voltage} U _{Zw is} increased in step 120. If it is determined in step 110 that the intermediate _{circuit voltage} U _{Zw has reached} its setpoint value U _Zwsoll , in step 130 at a first time t ₁ a first value Reslnew of the voltage drop across the measuring resistor R1 correlated with the filament resistance of one filament of the fluorescent lamp LP and to a second one Time t _{2 determines} a second value Res2neu this voltage drop. In step 140, the difference (Reslnew - Res2new) against a first threshold S1 is compared. If the difference is above the threshold, an algorithm for lamp type detection is performed. This includes the steps 150 to 230. This is first in step 150, the absolute amount $\left|\frac{\mathrm{re}s2\mathit{New}}{\mathrm{re}s2\mathit{old}}-1\right|$

compared with a threshold value X1, where Res2new represents the currently measured value of the voltage drop across the measuring resistor R1 and Res2old represents the value of the previous measurement. Is the value of the absolute value $\left|\frac{\mathrm{re}s2\mathit{New}}{\mathrm{re}s2\mathit{old}}-1\right|$

below the threshold X1, the lamp is operated in step 160 with the current operating parameter set. The new value Res2new differs very little from the old value Res2alt, so that the same lamp is unquestionably connected to the circuit arrangement. Therefore, it can be operated in step 160 unchanged with the current record. On the other hand, the value of $\left|\frac{\mathrm{re}s2\mathit{New}}{\mathrm{re}s2\mathit{old}}-1\right|$

above the threshold X1, it is determined in step 170 whether the value $\left|\frac{\mathrm{re}s2\mathit{New}}{\mathrm{re}s2\mathit{old}}-1\right|$

between the threshold X1 and a threshold X2, where X2 is greater than X1. If this is in the affirmative, it is assumed that it is still the same lamp that has only aged a little bit. Therefore, in step 180, the old value Res2old is overwritten by the new value Res2new. The lamp is then further operated in step 190 with the current record.

nicht zwischen X1 und X2 liegt, wird der Wert von Res2neu in einer Tabelle nachgesehen, um daraus zu entnehmen, welchem Lampentyp dieser Res2neu zugeordnet ist. Wird dabei im Schritt 200 der entsprechende Lampendatensatz erkannt, wird die Lampe im Schritt 210 mit dem erkannten Lampendatensatz i betrieben. Im Schritt 220 wird Res2alt durch Res2neu überschrieben. Wird im Schritt 200 kein dem Res2neu geordneter Lampendatensatz gefunden, wird die Lampe im Schritt 230 mit einem Default-Datensatz betrieben.On the other hand, in step 170, it is determined that the value $\left|\frac{\mathrm{re}s2\mathit{New}}{\mathrm{re}s2\mathit{old}}-1\right|$

is not between X1 and X2, the value of Res2new is looked up in a table to see which lamp type this Res2new is assigned to. If the corresponding lamp data record is detected in step 200, the lamp is in step 210 with the detected lamp data i operated. In step 220, Res2alt is overwritten by Res2new. If no lamp data set ordered to the Res2 ref found in step 200, the lamp is operated in step 230 with a default data set.

If it is determined in step 140 that the difference between Reslnew and Res2new is below the threshold value S1, it is checked in step 240 whether the difference (Reslnew - Res2new) is below a second threshold value S2 which is smaller than the threshold value S1. If this is the case, in step 250 a dummy coil is assumed or a coil short circuit. If a dummy coil can be excluded (it is recognizably a lamp used), then there is a coil short circuit and the circuit is switched off. If it is determined in step 240 that the difference between Reslnew and Res2new is greater than the threshold S2, the lamp will continue to operate in step 260 with the current record.

It has now been found that in the described procedure again and again damage to the circuit arrangement occurs when several lights are operated simultaneously on a single circuit arrangement.

Presentation of the invention

The object of the present invention is to further develop the method mentioned at the outset or the circuit arrangement mentioned at the outset in such a way that reliable operation of a plurality of luminaires on a circuit arrangement is made possible.

This object is achieved by a method having the features of patent claim 1 and by a circuit arrangement having the features of patent claim 7.

The present invention is based on the finding that, in the procedure according to the prior art, damage to the circuit arrangements therefore occurs because, although they occur in short lines, but not in long lines, such as occur when operating a plurality of luminaires with a circuit arrangement , can recognize. Spiral short circuits with long lines are characterized by the fact that the difference between the first measured value of the voltage drop across the measuring resistor and the second measured value of the voltage drop across the measuring resistor is greater than with a short-circuited short-circuit.

If, for the detection of helical short circuits, the threshold S2 was raised in step 240 for longer lines, then this would lead to a false detection of a short-circuit of the filament and to a false and thus undesired disconnection in the case of a lamp whose filaments were not completely cooled due to previous operation lead the circuit. In a further development of the prior art, it is therefore provided according to the invention, after determining that the difference (Res1new - Res2new) is greater than the threshold value S2, that a further case distinction is necessary, since otherwise a switched-on lamp would not be operated.

The present invention therefore provides that if it is determined in step 240 that the difference (Reslnew - Res2new) is greater than the threshold value S2, another case distinction is made: If Res2new is greater than a third threshold, with the third threshold being less than the first and greater than the second threshold, a coil short is detected. However, if Res2new is not greater than the third threshold, the lamp will continue to operate with the current operating parameter set. This measure takes into account that the value Res2new at power up is small compared to the value Res2new for a short circuit on longer lines.

With this procedure, filament short-circuits are reliably detected with longer lines, but again switched-on lamps are operated with the current data set. This makes it possible to provide two- and multi-lamp devices with circuitry, i. with a single ballast, since now the resulting longer lines can be safely monitored for filament short circuits. Damage to the circuitry used in this case are thus safely excluded.

A preferred embodiment is characterized in that it comprises the following further steps: If the difference (Res1new - Res2new) is less than the second threshold value, the following steps are carried out: If the second measured value lies between a fourth and a fifth threshold value, the fifth Threshold is less than the fourth threshold, the lamp type detection is locked. If the second reading is above the fourth threshold, a filament short is detected. If the second reading is below the fifth threshold, a dummy helix is detected. The locking of the lamp type detection, as shown in Fig. 2 in connection with steps 150 to 230, allows a luminaire manufacturer to ensure operation of a deployed lamp with a set of parameters that he has specified. For example, a luminaire manufacturer can design a luminaire for 50 W, thereby ensuring that even an 80-watt lamp used only operates like a 50-watt lamp. This allows in particular a weaker dimensioning of the performance-relevant elements of the lamp.

In a further preferred embodiment, it is provided that upon detection of a short-circuit of the filament when the lamp type detection is locked, the lamp type identification is unlocked. By this measure, a lock can be released again, for example by a dummy coil is used with a resistance of near zero.

Preferably, after determining a helix short circuit, a shutdown is performed, i. H. a shutdown of the circuitry to avoid damage to the circuitry. Advantageously, information about the occurrence of a shutdown is generated, which facilitates troubleshooting.

It is furthermore preferred if the first and / or the second threshold value are formed by the product of a factor a and the second value Res2new, where 0 <a <2. As a result, the first and second threshold values become dependent on the measured voltage value Res2new. This has proven to be more advantageous in practice than if using absolute values at this point would. For example, the threshold S1 may be Res2new (factor a = 1), the threshold S2 may be, for example, Res2new / 16.

The third threshold value S3 is preferably formed by the product of a factor b having the fourth threshold value S4, where 0 <b <1, the fourth threshold value S4 being greater than the second value Res2new caused by the lowest-resistance coil, and the fifth threshold value S5 being smaller is the fourth threshold.

Further advantageous embodiments will become apparent from the dependent claims.

The preferred embodiments presented with reference to the method according to the invention and their advantages apply correspondingly, as far as applicable, to the circuit arrangement according to the invention.

Short description of the drawing (s)

Fig. 1

in schematischer Darstellung eine aus dem Stand der Technik bekannte Schaltungsanordnung;

Fig. 2

ein Flussdiagramm zur Darstellung eines aus dem Stand der Technik bekannten Verfahrens;

Fig. 3

ein Flussdiagramm zur Darstellung einer Ausführungsform eines erfindungsgemäßen Verfahrens; und

Fig. 4

den zeitlichen Verlauf der mit dem Kehrwert des Wendelwiderstands korrelierten, über dem Strommesswiderstand R1 abfallenden Spannung Res in unterschiedlichen Situationen.

In the following, an embodiment of a method according to the invention will be described in more detail with reference to the accompanying drawings. Show it:

Fig. 1

a schematic representation of a known from the prior art circuit arrangement;

Fig. 2

a flow chart illustrating a known from the prior art method;

Fig. 3

a flowchart illustrating an embodiment of a method according to the invention; and

Fig. 4

the time course of the correlated with the reciprocal of the helical resistance, across the current measuring resistor R1 decreasing voltage Res in different situations.

Preferred embodiment of the invention

In the following, only the differences from the prior art will be discussed. The related to Fig. 2 The statements made thus apply, as far as the flowchart of Fig. 2 with the of Fig. 3 matches, even for the inventive method and are therefore not repeated again.

According to Fig. 3 For example, if it is determined in step 240 that the difference (Res1new - Res2new) is greater than a second threshold S2, the second threshold being less than the first threshold S1, another case distinction is made in step 270: If it is determined that if the value Res2new is greater than a third threshold S3, in step 280 a helical short circuit is detected, or if there has been a locking of the lamp type identifier according to steps 150 to 230, this is unlocked. If it is determined in step 270 that Res2new is not greater than the third threshold value S3, the lamp is operated in step 290 with the current operating parameter set.

If it is determined in step 240 that the difference (Res1new - Res2new) is smaller than the second threshold value S2, a further case distinction is made in step 300. In this case, it is checked whether the value Res2new is greater than a fourth threshold value S4. If this is answered in the affirmative, Thus, in step 310, a short-circuited circuit is detected, or if the lamp type detection was locked in accordance with steps 150 to 230, this unlocked. If, on the other hand, it is determined in step 300 that the value Res2new is smaller than the fourth threshold value S4, a further case distinction is made in step 310. In this case, it is checked whether Res2new is greater than a fifth threshold value S5, the fifth threshold value being smaller than the fourth threshold value S4. If this is the case, the lamp type detection is locked according to steps 150 to 230 in step 320. If this is not the case, however, a dummy coil is assumed in step 330.

In a preferred embodiment, the following threshold values have been selected: S1 = Res2new, S2 = 1/16 Res2new, S3> S4 / 4, S4> S5, S4> Res2new caused by the lowest resistance coil, X1 = 6.33 and X2 = 12.5.

The algorithm of the method according to the invention is in the microcontroller MC of Fig. 1 implemented. This has in particular the required storage and comparison devices.

Fig. 4 shows, for further understanding, the time course of the voltage drop Res across the current measuring resistor R1, which is correlated with the reciprocal of the helical resistance, for different situations: Curve a) indicates the time course in the case of a dummy helix, curve b) in the case of a short-circuited helix, curve c ) in the case of a short-circuited coil for longer lines, curve d) in the case of intact helices and curve e) when restarting, ie the coils were not cooled from the previous operation.

The present invention makes it possible to detect a short-circuit of the filament both for short (curve b) and for longer lines (curve c). It allows operation of the fluorescent lamp when switched on in the cooled state (curve d) as well as when switching on in the not yet cooled state (curve e). Finally, an inserted dummy coil (curve a) is still reliably detected.

Claims (7)

1. Method for operating at least one discharge lamp (LP) in a circuit arrangement having an input with a first and a second input connection for connecting a DC supply voltage (U_Zw); an output with at least a first and a second output connection for connecting the at least one discharge lamp (LP); an inverter with at least a first (T1) and a second electronic switch (T2) that are coupled in series between the first and the second input connection, wherein a midpoint (M) of the inverter is formed between the first (T1) and the second switch (T2); an ignition device that comprises a lamp inductor (L1) and a resonant capacitor (C2); a preheating device that comprises the series connection of a primary inductor (P1), a third electronic switch (T3) and a current measurement resistor (R1) that is coupled between the midpoint (M) of the inverter and the second input connection, and a first (SI1) and a second (SI2) secondary inductor coupled to the primary winding (P1), wherein the first (SI1) secondary inductor is coupled to the first output connection and the second secondary inductor (SI2) is coupled to the second output connection; a control device (MC) that is coupled to the current measurement resistor (R1) in which at least two sets of operating parameters assigned to different types of discharge lamps are stored, wherein one set of operating parameters constitutes a current set of operating parameters, wherein the control device (MC) is designed to actuate at least the first (T1), the second (T2) and the third (T3) electronic switch in accordance with the current set of operating parameters; wherein in the preheating phase a first value (Res1new) of the voltage drop correlated with the reciprocal of the electrical resistance of at least one coil (E1) of the at least one discharge lamp (LP) is determined across the current measurement resistor (R1) at a first instant (t₁), and a second value (Res2new) of the voltage drop correlated with the reciprocal of the electrical resistance of the at least one coil (E1) of the at least one discharge lamp (LP) is determined across the current measurement resistor (R1) at a second instant (t₂), wherein the second instant (t₂) is after the first instant (t₁);
   characterized by the following steps:

   a) determining the difference between the first (Res1new) and the second value (Res2new) (step 140);

   b)

   b1) if the difference is greater than a first threshold value (S1):

   carrying out an algorithm for lamp-type recognition (150 to 230);

   b2) if the difference is not greater than the first threshold value (S2):

   c1) if the difference is greater than a second threshold value (S2), wherein the second threshold value (S2) is less than the first threshold value (S1) (step 240):

   d1) if the second value is greater than a third threshold value (S3) (step 270):

   determining a coil short circuit (step 280);

   d2) if the second value is not greater than the third threshold value (S3):

   operating the lamp with the current set of operating parameters (step 290).
2. Method according to Claim 1, characterized in that it comprises the following further steps:

   c2) if the difference is less than the second threshold value (S2):

   d1) if the second measured value is between a fourth (S4) and a fifth threshold value (S5), wherein the fifth threshold value (S5) is less than the fourth threshold value (S4):

   disabling the lamp-type recognition (step 320);

   d2) if the second measured value is greater than the fourth threshold value (S4):

   determining a coil short circuit (step 310);

   d3) if the second measured value is less than the fifth threshold value (S5):

   determining a dummy coil (step 330).
3. Method according to either of Claims 1 and 2, characterized in that the lamp-type recognition is enabled upon determination of a coil short circuit given disabled lamp-type recognition (steps 280, 310).
4. Method according to one of the preceding claims, characterized in that a shutdown is carried out after determination of a coil short circuit.
5. Method according to one of the preceding claims, characterized in that the first (S1) and/or the second threshold value (S2) is formed by the product of a factor a and the second value, wherein 0 < a < 2.
6. Method according to one of the preceding claims, characterized in that the third threshold value (S3) is formed by the product of a factor b with the fourth threshold value (S4), where 0 < b < 1, wherein the fourth threshold value (S4) is greater than the second value (Res2new) caused by the coil of least resistance, and the fifth threshold value (S5) is less than the fourth threshold value.
7. Circuit arrangement for operating at least one discharge lamp (LP), having

   - an input of a first and a second input connection for connecting a DC supply voltage (U_Zw);

   - an output with at least a first and a second output connection for connecting the at least one discharge lamp (LP);

   - an inverter with at least a first (T1) and a second (T2) electronic switch that are coupled in series between the first and
   the second input connection, wherein a midpoint of the inverter is formed between the first (T1) and the second switch (T2);

   - an ignition device that comprises a lamp inductor (L1) and a resonant capacitor (C2);

   - a preheating device that preheating device that comprises the series connection of a primary inductor (P1), a third electronic switch (T3) and a current measurement resistor (R1) that is coupled between the midpoint (M) of the inverter and the second input connection, and a first (SI1) and a second (SI2) secondary inductor coupled to the primary winding (P1), wherein the first secondary inductor (SI1) is coupled to the first output connection and the second secondary inductor (SI2) is coupled to the second output connection;

   - a control device (MC) that is coupled to the current measurement resistor (R1) in which at least two sets of operating parameters assigned to different types of discharge lamps are stored, wherein one set of operating parameters constitutes a current set of operating parameters, wherein the control device (MC) is designed to actuate at least the first (T1), the second (T2) and the third (T3) electronic switch in accordance with the current set of operating parameters; wherein the control device (MC) is, furthermore, designed to determine in the preheating phase a first value (Res1new) of the voltage drop correlated with the electrical resistance of at least one coil (E1) of the at least one discharge lamp (LP) via the current measurement resistor (R1) at a first instant (t₁), and to determine
   a second value (Res2new) of the voltage drop correlated with the electrical resistance of the at least one coil (E1) of the at least one discharge lamp (LP) via the current measurement resistor (R1) at a second instant (t₂), wherein the second instant (t₂) is after the first instant (t₁);

   characterized in that the control device (MC) is, furthermore, designed to carry out the following algorithm:

   a) determining the difference between the first (Res1new) and the second value (Res2new) (step 140);

   b)

   b1) if the difference is greater than a first threshold value (S1) (steps 150 to 230):

   carrying out an algorithm for lamp-type recognition;

   b2) if the difference is not greater than the first threshold value (S2):

   c1) if the difference is greater than a second threshold value (S2), wherein the second threshold value (S2) is less than the first threshold value (S1) (step 240):

   d1) if the second value is greater than a third threshold value (step 270):

   determining a coil short circuit (step 280);

   d2) if the second value is not greater than the third threshold value (S3):

   operating the lamp with the current set of operating parameters (step 290).

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