EP2796012B1 - Method, operating device and lighting system with integrated lamp rectifier effect detection - Google Patents

Description

The present invention relates to control gear for lamps, in particular for gas discharge lamps, as well as to a lighting system.

In document US2011 / 0084613 A1 An apparatus for operating a high performance gas discharge lamp with EOL detection is described. The document US2006 / 0170327 A1 describes a circuit arrangement with a driver circuit that allows the determination of an EOL state.

It is an object of the invention to efficiently perform a control or a misrecognition in the operation of bulbs.

This object is achieved by the features of the independent claims. The dependent claims further form the central idea of the invention particularly advantageous.

A first aspect of the invention relates to a method for operating at least one luminous means, such as, for example, a gas discharge lamp, starting from a clocked circuit. For detecting a state, in particular an error state, of the operation of the luminous means, a measurement signal which reproduces a first electrical parameter with respect to the luminous means operation is compared with a threshold value. The threshold value can be set as a function of a rectifier effect having the luminous means.

A further aspect of the invention relates to a method for operating at least one luminous means, such as. Gas discharge lamp, starting from a clocked circuit. To detect a fault condition of the operation of the bulb is a measurement signal, the one reproduces electrical parameter with respect to the lighting mode, with a. Threshold compared. The threshold value can be set as a function of the DC component of the luminous flux.

Another aspect of the invention relates to a method for operating at least one light source, such as. Gas discharge lamp. A rectifier effect of the luminous means is determined in such a way that an error state (EOL) can be derived from a comparison of a value (Sbase) that reproduces this rectifier effect with a threshold value (SEOL +). The determined rectifier effect is taken into account when monitoring another fault condition.

Another aspect of the invention relates to a control circuit, in particular ASIC or microcontroller, which is designed for such a method.

Another aspect of the invention relates to an operating device for lighting means, in particular for gas discharge lamps, comprising such a control circuit.

Another aspect of the invention relates to a lighting system, comprising a control unit and at least one such preferably connected via a bus line such operating device.

A further aspect of the invention relates to a circuit for operating a luminous means, such as, for example, a gas discharge lamp, comprising a half-bridge or full-bridge circuit for providing a supply voltage for the at least one luminous means, and a control circuit for controlling the operation of the lighting means and / or error detection. In order to detect a fault state of the operation of the luminous means, a measurement signal which reproduces a first electrical parameter with regard to the luminous means operation is compared with a threshold value. The threshold value can be set as a function of a rectifier effect having the luminous means.

These aspects can be further developed as follows.

The rectifier effect can be detected by directly or indirectly monitoring a rectifier effect parameter. The rectifier effect parameter can map the voltage dropping at the light source, the luminous flux, the luminous flux impedance and / or the power consumed by the luminous means.

The rectifier effect can be detected by directly or indirectly monitoring a rectifier effect parameter. The rectifier effect parameter can reflect the DC voltage drop across the lamp or the unbalance of the lamp current.

The threshold may be adjustable such that a variation of the rectifier effect parameter results in a corresponding variation of the threshold.

The threshold may be adjustable at each clock or period of the clocked circuit.

A detected change in the rectifier effect parameter may result in the adjustment of the threshold in the next clock of the clocked circuit.

Within a cycle, the maximum permissible change of the threshold value can be limited.

An error condition can be triggered as soon as the rectifier effect parameter reaches or reaches several times.

The measurement signal can reproduce the current through a switch of the clocked circuit, and be compared to detect an overcurrent with a threshold value.

The threshold can be used to detect a dead reset of a switch of the clocked circuit.

The threshold value can serve to detect a capacitive operation of the luminous means.

Further advantages, characteristics and features of the invention will now be explained with reference to the figures of the accompanying drawings.

• Figur 1 eine schematische Darstellung eines ersten Ausführungsbeispiels der Erfindung bzw, einer Abwandlung davon,
• Figur 2 den zeitlichen Verlauf von unterschiedlichen Signalen bzw. Spannungen innerhalb vom Betriebsgerät.
• Figur 3 ein Ausführungsbeispiel der Anpassung des Schwellenwerts gemäß der vorliegenden Erfindung.
• Figur 4 einen erfindungsgemäßen Filter.
• Figur 5, 6 die Eingangs- und Ausgangssignale eines erfindungsgemäßen Filters.

Showing:

• FIG. 1 a schematic representation of a first embodiment of the invention or, a modification thereof,
• FIG. 2 the time course of different signals or voltages within the operating device.
• FIG. 3 an embodiment of the adjustment of the threshold according to the present invention.
• FIG. 4 a filter according to the invention.
• FIG. 5, 6 the input and output signals of a filter according to the invention.

First of all, a first exemplary embodiment of a measuring circuit for an operating device 1 for at least one luminous means is to be described schematically on the basis of FIG Fig. 1 be explained.

The AC line voltage is fed via a filter 8 to an AC / DC converter 7. In the AC / DC converter 7, the AC line voltage is converted into a DC voltage and set to a higher voltage, preferably between 300V and 400V. This is accordingly also at the storage capacitor 6. The AC / DC converter 7 may include a rectifier and also an active (PFC) circuit (clocked by a switch controlled by a control unit or formed by a charge pump circuit (Active or Passive Valley Fill)).

An inverter 2, in this case a half-bridge, alternately drives the switches Q1 and Q2, preferably power transistors. This is used to provide a supply voltage for at least one light-emitting element 4. The luminous element or luminous means may be a gas discharge lamp, but also any other type of luminaire, for example an LED or OLED or LED / OLED arrangement.

For simplicity, in Fig. 1 the load 5, including the light-emitting element 4 and other necessary for the pre-circuit electrical components, only indicated.

The half-bridge current is detected via a measuring resistor R102 in series with the lower-potential switch Q2 of the half-bridge. The lamp voltage is detected via a resistor divider R104. Both measurement signals are preferably fed via a single pin SDV_lamp a control circuit 3, preferably an ASIC. However, any other form of integrated circuit, such as a microcontroller or hybrid solution, or a conventional (discrete) circuit may be used as an alternative to the ASIC.

The ASIC 3 also controls the AC / DC converter and the clock frequency of the half bridge 2.

The pin SDV_lamp is therefore an addition of the voltages of the lamp voltage resistance divider R104 and the measuring resistor R102. However, it is also possible to connect the 2 signals to different terminals of the ASIC. The ASIC 3 has an internal constant current source A. This supplies the incoming signal with a DC level, so that negative voltages at the pin SDVlamp are avoided. Instead of the internal constant current source A can also be an external power source, in the simplest case, a to a supply voltage (eg, the bus voltage or low-voltage supply) connected resistor or it can also be an internal or external voltage source can be used.

The signal of the half-bridge current has a regular time interval, with preferably half a period length in which it is zero. The reason for this is that during this period, the switch Q2 is open and therefore no half-bridge current is measured. In this period, therefore, only the lamp voltage is applied to the pin SDV _lamp . This circumstance can be exploited to discriminate the two signals.

The signal of the lamp voltage has a sinusoid, which can be sufficiently determined by measuring frequency and amplitude.

Furthermore, it can be used to discriminate that lamp voltage error conditions are relatively slow phenomena, while the error conditions in the half-bridge current with a relatively large amplitude and for a short time occur.

With the aid of the two signals, as described in more detail below, an overcurrent, for example at throttle saturation in the lamp ignition process or an overcurrent during lamp operation, can be determined. Furthermore, a capacitive operation of the lamp and an EOL effect (end of lamp life) of the lamp can be detected.

The attenuation of the AC component of the lamp voltage takes place in the circuit according to Fig. 1 regardless of their DC component. Preferably, the AC component is attenuated more than the DC component. This is achieved by the parallel connection of capacitor C10X and resistor R102. This parallel connection has a strong damping effect on higher frequencies. The capacitor C10X serves as a filter for the AC component. Thus, the DC component is less dampened relative to the AC component.

This has the advantage that both values can be damped in areas suitable for the ASIC. This is necessary because the voltage spikes of the AC component in the firing process are many times higher than the DC component whose DC offset is used to identify an EOL. If the capacitor C10X has a sufficiently large value, the high-frequency AC voltage component of the lamp voltage can be filtered out, so that the detected signal at the input SDV _Lamp is composed of the DC voltage component of the lamp voltage and the half-bridge current. Thus, during the phase in which no half-bridge current is detected, the DC component of the lamp voltage can be measured, while in the phase in which a half-bridge current flows, the half-bridge current is detected, taking into account the determined DC voltage component of the lamp voltage.

The AC signal of the half-bridge current can be used, for example, to identify a saturation of the throttle as well as to detect an overcurrent, a capacitive operation or for preheat control.

In the ignition detection, for example, additionally monitors whether the throttle is no longer in saturation. It can also be an ignition control, in which the throttle is driven to saturation. When igniting an ignitible or defective lamp, the circuit is driven into saturation because the frequency is very close. is pushed to resonance). In case of saturation can at least one half-bridge switch is opened earlier, but preferably the next switching clock is initiated with the previous switch-on time. The omission of the saturation, or a high ignition current, can also be used as an ignition detection signal

• Eine Halbbrückenstrommessung und/oder Lampenstrommessung kann zur "Closed Loop"-Regelung (d.h. Regelung mit geschlossener Regelschleife) der Lampenleistung oder der Vorheizenergie verwendet werden.
• Außerdem kann eine Messung zur Erkennung der Lampenwendeln anhand der übermittelten Vorheizenergie, bzw. des Glühdrahts durchgeführt werden. Somit kann eine Lampenerkennung durchgeführt werden.
• Es kann eine "Relamp"-Erkennung durchgeführt werden, d.h. ob eine (neue) Lampe eingesetzt worden ist, nämlich an dem Verhalten des Ausgangskreises
• Eine Halbbrückenstrommessung und/oder Lampenstrommessung kann zur Fehler Erkennung eingesetzt werden: Es kann die Gefahr einer Sättigung während der Zündung oder eines zu hohen Stroms auch während des Betriebs verringert werden.
• Außerdem kann ein Schutz vor einem kapazitiven Lampenbetrieb und/ oder einer Überlastung der Schalter beim Einschalten erreicht werden.
• Eine Halbbrückenstrommessung und/oder Lampenstrommessung kann zur Stromregelung verwendet werden.
• Der Halbbrückenstrom kann auch zur Regelung der Heizenergie, insbesondere der Vorheizenergie, verwendet werden.
• Der Lampenstrom kann zur Regelung der Lampenleistung oder zur Regelung der Vorheizenergie verwendet werden.
• Es kann auch eine Sättigung (insbesondere während der Zündung) oder eine Überspannung im Lastkreis anhand der Spannungsmessung erkannt werden.

Further advantageous evaluation possibilities of the current signal are shown below. For this purpose, the half-bridge current and / or the lamp current can be detected. So that the lamp current can be used for a measurement during preheating, it requires a special pre-circuit, so that even when preheating this lamp current can be measured. The lamp current signal can be measured at the point "lamp voltage". The half-bridge current can be detected via the measuring voltage at the half-bridge shunt R101:

• A half-bridge current measurement and / or lamp current measurement may be used for "closed-loop" regulation of lamp power or preheat energy.
• In addition, a measurement for detecting the lamp filaments can be carried out on the basis of the transmitted preheating energy or of the filament. Thus, a lamp detection can be performed.
• A "relamp" detection can be carried out, ie whether a (new) lamp has been used, namely on the behavior of the output circuit
• A half-bridge current measurement and / or lamp current measurement can be used for fault detection: there may be a risk of saturation be reduced during ignition or too high a current even during operation.
• In addition, protection against capacitive lamp operation and / or overload of the switches at power up can be achieved.
• A half-bridge current measurement and / or lamp current measurement can be used to control the current.
• The half-bridge current can also be used to control the heating energy, in particular the preheating energy.
• The lamp current can be used to control the lamp power or to control the preheat energy.
• It is also possible to detect a saturation (in particular during ignition) or an overvoltage in the load circuit on the basis of the voltage measurement.

• Eine Spannungsmessung kann zur End-Of-Life-Erkennung der Lampe eingesetzt werden.
• Eine Lampenspannungsmessung kann durchgeführt werden
• Es kann eine Erkennung des Heizdrahts durchgeführt werden, beispielsweise bei Vorhandensein eines zusätzlichen DC-Pfads von der Bus-Spannung über eine Wendel. Dadurch kann ebenfalls erkannt werden, ob überhaupt eine Lampe eingesetzt ist.
• Es kann eine "Relamp"-Erkennung durchgeführt werden, d.h. ob eine neue Lampe eingesetzt worden ist.
• Es kann eine Lampenzündung erkannt werden.

Further advantageous applications of the voltage evaluation are shown below.

• A voltage measurement can be used for the end-of-life detection of the lamp.
• A lamp voltage measurement can be performed
• A detection of the heating wire can be carried out, for example in the presence of an additional DC path from the bus voltage via a helix. As a result, it can also be recognized whether a lamp is used at all.
• It can be performed a "Relamp" detection, ie, whether a new lamp has been used.
• It can be detected a lamp ignition.

It should be noted that any evaluation options of the current measurement can be combined with those of the voltage measurement.

To start a lamp, the heating coils of the lamp 4 are first preheated. For this purpose, the half-bridge 2 generates an AC voltage which is above the resonant frequency of the resonant circuit. The resulting voltage is too low to cause the ignition of the lamp 4. The pin SDVI _Lamp may be in standby at this time if none of the measurements described above is used, such as lamp filament detection or preheat control.

At the end of preheating, the ignition of the lamp 4 is achieved in that the switch-on time of the two switches Q1 and _Q2 of the inverter is gradually increased. Accordingly, the operating frequency of the inverter is reduced.

In the preheating phase, a small current flows through the lamp. The DC offset caused by the EOL effect is very low. This can therefore be ignored here. Therefore, no compensation of a DC offset by an internal DC power source A is necessary here. Thus, it is possible to turn on the internal power source A only after the ignition of the lamp with a preset value.

The internal current source A can also be realized as a stepwise switchable current source or as a parallel connection of two current sources. As a result, different currents to compensate for a DC offset can be impressed by the internal power source A and Thus, during the different phases of operation different compensations or Abschaltempfindlichkeiten be achieved. Preferably, a lower current for the internal power source A can be set during ignition, so that a lower sensitivity can be set according to the expected high voltages.

The detection of errors such as the detection of the EOL effect can be activated depending on the operating state of the lamp or the circuit.

The following is an example of a method for avoiding overcurrent in lamp ignition.

After starting the process in a first step, the heating coils are preheated. In the next step, switch Q1 of the inverter is closed. Switch Q2 is open at this time. After a time t _R , the switch Q1 is opened again. At t _R , it is preferably half the period of the current operating frequency of the inverter, but it may also be a shorter period of time.

In the following step, the switch Q2 is closed. There may be a delay time t _D between the opening of the switch Q1 and the closing of the switch Q2.

In the next step, the signal applied to Pin SDV _{lamp is} measured. If it is above a threshold value V _{lamp peak} (pk), the lamp is supplied with an excessively high current. However, it is also conceivable, an inadmissible high current only when the threshold has been exceeded several times, for example five times.

In addition, the increase in the current can also be assessed and an inadmissibly high rise can be used as an additional assessment criterion.

When determining the threshold value, the signal to be analyzed by the AC voltage must always be taken into account in the characteristic to be analyzed in the ASIC. For this purpose, the signal of the lamp voltage from the ASIC must be compensated analogously without delay. By means of the time window in which switch Q2 is opened and, accordingly, the measured half-bridge current is zero, the lamp voltage signal can be determined.

In a smoothing or damping of the AC component of the lamp voltage through a capacitor (s. Fig. 1 ) it may be sufficient that only the DC component of the lamp voltage has to be considered.

For returning the half-bridge current to permissible ranges, the switch Q2 is now opened again immediately. This is equivalent to an increase in the current switching frequency. The actual operating frequency of the inverter is not changed. The process is instead repeated with keeping the current operating frequency, preferably after a dead time, by a return to the step of closing the switch Q1. However, it is also possible to return the half-bridge current to allowable ranges reach by increasing the operating frequency of the inverter in the short term.

If the signal applied to pin SDV _{lamp is} at a threshold value V _{lamp_peak} (pk), then after time t _R the switch Q2 is opened again. However, the switch Q2 can also be opened again in a time t <t _R.

In a subsequent step, the duty cycle t _{R is} increased. Thus, the operating frequency of the inverter is reduced.
The process is repeated several times in succession. There may be a delay time t _D between the steps of opening and closing the switches.

During normal operation of the lamp, the inadmissible state may occur that the lamp is operated capacitively. In this state, a current flows through the switch when switching on. This can destroy the switch. Furthermore, in capacitive operation, the regulation of the lamp by the ASIC no longer works.

The following example shows a method of avoiding capacitive operation of the lamp. To identify a capacitive operation, a gradient measurement is made here between the phase of the lamp voltage and the half-bridge current. (Instead of the lamp voltage, it is also possible to monitor another voltage in the load circuit, for example the voltage across the choke or via a transformer, if present).

After a successful ignition, the lamp is in normal operation. At least two measurements are now taken at successive times at the pin SDV _lamp . The measurements are samples. The measurements are taken at a time when switch Q2 has just not been opened.

The difference of the at least 2 measurements is then calculated.

If the subsequent sample is lower than the previous one, then there is an inductive operation of the lamp. This operation is permissible.

The measuring process is repeated several times. However, the possibility also exists after a time interval, or only after the change of parameters, e.g. the lamp dimming, make another measurement.

If the subsequent sample value is higher than the previous one, then there is a capacitive operation of the lamp. This operation is prohibited.

However, it is also conceivable to detect an impermissibly capacitive operation only when the subsequent sample value has been higher than the previous one several times, for example five times in succession.

Then the switch Q2 is opened.

After a dead time, the switch Q1 is closed again. The dead time is preferably a predetermined value, but it is also conceivable to use an adaptive method for determining the dead time. For example, an extension of the dead time would be possible with a single or renewed occurrence of a capacitive operation. The dead time can also be adjusted by measuring and checking the half-bridge current shortly before switching on the switch Q2 (ie while a current is already flowing through the free-wheeling diode from the switch Q2). With an impermissible value for the half-bridge current, the dead time can be increased and thus the switch Q2 can be protected from an overcurrent or an overload.

After closing the switch Q1 jumps back and the measuring process is repeated.

Another method for avoiding capacitive operation of the lamp is explained below. To identify a capacitive operation, a differential measurement of absolute values is made here.

However, an absolute value detection is also conceivable instead of the difference measurement. Here, a comparison of the current value is made before turning off switch Q2 with a threshold.

After a successful ignition, the lamp is in normal operation. A measurement S1 is made immediately before switching off switch Q2 on pin SDV _lamp .

Another measurement S2 is made immediately after switching on switch Q1.

Then the threshold value is compared with the difference S1-S2.

If the difference S1 S2 is greater than the threshold, then there is an inductive operation of the lamp. This operation is permissible. It will jump back and the measurement process repeated. However, the possibility also exists after a time interval, or only after the change of parameters, e.g. the lamp dimming, make another measurement.

If the difference S1 - S2 is smaller than the threshold, then there is a capacitive operation of the lamp. This operation is prohibited. However, it is also conceivable to detect an impermissibly capacitive operation only when the difference has been smaller than the threshold value several times, for example five times in succession.

The driving frequency of the half-bridge is subsequently increased. As a result, the lamp operation returns to the inductive branch of the resonance curve.

If an inadmissible capacitive operation is detected beyond a predetermined number of measurements, the lamp is turned off.

For this purpose, a counter x can be used, which is increased by one.

The value of the counter x is compared with a reference value X _max .

If x ≥ X _max , the lamp is switched off. In this case, the counter x can be reset to 0.

Instead of an immediate shutdown, any other measure is conceivable, for example, a signal that warns of a capacitive operation.

It should be noted that, of course, the approaches of the above examples can be reversed. This means that in a gradient measurement also a frequency increase of the half-bridge, and in an absolute value measurement, an early opening of switch 2 is possible. Other combinations of features from the above examples are conceivable.

After a successful ignition of the lamp, the charge in capacitor C101 slowly becomes smaller. This charge was caused by a high half-bridge current during the ignition phase. However, the internal DC power source and the DC component of the lamp voltage recharge the capacitor C101 at the same time due to an EOL (End of Lamp Life) effect. In this way, the charge stabilizes at a certain level.

By means of a measurement before or during the switching off of the switch Q1, the DC component of the lamp voltage can be easily monitored.

Fig. 2 shows the time course of different signals or voltages within the operating device. 1

The signal Vgs / Q1 indicates the gate-source voltage or the control voltage of the higher-potential switch Q1 of the inverter 2. The signal Vgs / Q2 is the gate-source voltage or the control voltage of the potential-low Switch Q2. Both switches are turned on and off periodically. In each period TP, each switch Q1, Q2 is turned on once. The higher-potential switch Q1 is turned on at a time T0, T4 and turned off again at a later time T1. The potential-low switch Q2 is turned on at a time T2 and turned off again at a later time T3. Between switching off one of the switches and turning on the other switch, there is preferably a delay time T2-T1 and T4-T3. The control voltages Vgs / Q1, Vgs / Q2 for the switches are preferably PWM signals.

With regard to the low-potential switch Q2 is in Fig. 2 also shows the voltage Vds / Q2 between drain and source. When switch Q2 is on, this voltage Vds / Q2 is at a low voltage level, preferably zero. After turning off the switch Q2, this voltage Vds / Q2 rises to a constant value and, after turning off the higher-potential switch Q1, it goes back to the low voltage level.

The signal SDEOL corresponds to the signal SDV _Lamp described above, which is present at the pin of ASIC and which represents the measurement of the half-bridge current and the lamp voltage.

According to the invention, as described above, a rectifier effect can be deduced. In particular, this effect is detected on the basis of the signal SDEOL, for example if the DC component of the lamp voltage is higher than a first threshold value SEOL +. Alternatively or additionally, a rectifier effect is detected if the DC component of the lamp voltage is smaller than a second threshold value SEOL-.

The rectifier effect may e.g. occur on older gas discharge lamps or fluorescent lamps and lead to an overload of the operating device 1. Because of the uneven emission surfaces of the two lamp electrodes, the lamp current flowing over the gas discharge path of the gas discharge lamp concerned can then be higher in one direction than in the other. The fluorescent lamp then acts in a similar way to a rectifier, preferentially passing the lamp current in one direction while being less well transmitted in the opposite direction.

A slower occurring rectifier effect is recognized according to the invention. This is done e.g. by means of the signal SDEOL, in which the value of this signal SDEOL is detected during the switch-off time of the higher-potential switch Q1 or during the switch-on time of the low-potential switch Q2. The only measured DC component of the signal SDEOL indeed comes from the lamp voltage during this period. If the measured value of the DC lamp voltage is not between the two prescribed threshold values SEOL + and SEOL-, an inadmissible rectifier effect is detected and appropriate measures are taken.

Alternatively, the rectifier effect can also be recognized by the fact that asymmetries in the lamp current occur. An excessive asymmetry would then lead to a fault condition. As a monitoring signal so can also serve the lamp current. According to one exemplary embodiment of the invention, the measurement of the lamp current takes place with the aid of the above-described signal SDVI _lamp . This signal SDVI _lamp is connected to a pin of the ASIC present, to which the measurement of the half-bridge current, the lamp voltage and the lamp current are supplied. Alternatively, a measuring resistor (not shown) may be provided for measuring the lamp current.

Alternatively, a current shift occurring between individual lamp branches due to the rectifier effect can also be detected by evaluating the impedance or the power of the lamp 4, the impedance or the power being measured in a known manner.

When the potential-low switch Q2 is switched on, the above-described method for avoiding overcurrent, which has already been described above, is carried out with the aid of the signal SDEOL. During this period, the lamp current is compared with a threshold for the lamp current SOCP. If the measured lamp current exceeds this threshold SOCP, an error condition OCP (Overcurrent Protection) is triggered, i. too high a current flows through the resistor in series with the lower-potential switch of the half-bridge. Preferably, the above-described corresponding measures are to be taken.

According to the invention, this threshold value for the lamp current SOCP is set as a function of a detected rectifier effect. In the embodiment of Fig. 2 the DC component of the lamp voltage Sbase is taken into account when setting the threshold value for the lamp current SOCP. If the DC lamp voltage Sbase increases, the control circuit 3 causes the threshold value for the lamp current SOCP to increase.

Similarly, according to the invention, the threshold value SCCD for the error state with respect capacitive state, and the threshold for the switching of the switches of the half-bridge inverter at zero voltage state adjusted according to the DC lamp voltage.

Fig. 3 shows an embodiment of the adaptation of the threshold value SOCP for detecting a fault condition due to an excessive current through the low-potential switch Q2. The low-potential switch Q2 of the half-bridge is turned on and off once per period TP. A period can also be called a clock.

In the first period between 0 and TP, the control circuit 3 measures a DC lamp current of 0. At the same time, the control circuit 3 performs overcurrent monitoring. For this purpose, as already described, it compares the current through the switch Q2 with the set threshold SOCP / 0. Since no DC lamp voltage has been measured, the threshold for detecting an overcurrent in the second period remains the same.

In this second period between TP and 2TP, a DC lamp voltage Δ1 is measured. This value is taken into account according to the invention for adapting the threshold value SOCP. Thus, in the third period between 2TP and 3TP, the threshold SOCP is increased accordingly, preferably to SOCP / 0 + Δ2.

From the Fig. 3 It follows that the adjustment of the threshold value SOCP preferably takes place already one period after detection of a DC lamp voltage. As soon as a variation of the DC lamp voltage is measured by the control circuit 3, in the next clock or in the next Period of threshold SOCP adjusted and recalculated.

A variation Δ1 in the DC lamp voltage causes the new threshold value to be changed by the value Δ2. According to one embodiment, the threshold increases or decreases according to the variation of the DC lamp voltage. In this case, Δ2 = Δ1. Alternatively, the adjustment of the threshold value may be made proportional to the variation Δ1 of the DC lamp voltage: Δ2 = k.Δ1, where k is a preferably positive value. Preferably, the variation Δ2 of the threshold SOCP is a function of the variation Δ1 in the DC lamp voltage.

OCP

(Overcurrent Protection), d.h. zu hoher Strom durch den Shunt in Serie zu dem potentialniedrigeren Schalter der Halbbrücke,

EOL

(End of Lifetime), Gleichrichtereffekt der Lampe,

CCD

(Capacitive Current Detection), kapazitiver Strom bzw. kapazitiver Betrieb,

SättigungThe invention thus preferably proposes to detect a multiplicity of possible fault states during operation of a gas discharge lamp at a pin of an ASIC. The detection on different pins is also provided. These error conditions are, as already mentioned:

OCP

(Overcurrent Protection), ie too high current through the shunt in series with the lower-potential switch of the half-bridge,

EOL

(End of Lifetime), rectifier effect of the lamp,

CCD

(Capacitive Current Detection), Capacitive Current or Capacitive Operation,

saturation

It would also be conceivable to detect a switching of the switches of the half-bridge inverter in the zero-voltage state.

Meanwhile, OCP and CCD thresholds as well as optional other errors such as zero saturation saturation or switching are adaptively adjusted. For this purpose, the reference value (SOCP, SCCD) is reset in each cycle in which the higher-potential switch Q1 is turned on.

Upon manipulation of the voltage on the sense pin during the period during which higher potential switch Q1 is turned on, the corresponding thresholds (SOCP, SCCD) may be changed in the subsequent cycle.

According to the invention, therefore, a shutdown due to an OCP, CCD, and / or another fault condition is dependent on a DC lamp voltage. For example, the shutdown can be done only at a higher (SOCP / 0 + Δ2) or even at a much lower switch current (OCP state).

The DC lamp voltage, in Fig. 2 also called baseline or zero line, or this level is at the same time also the level which is related to the non-relative, but absolute thresholds SEOL +, SEOL- for the error states EOL. This means that the corresponding error states are reached when the baseline level reaches the corresponding absolutely predefined switch-off thresholds SEOL +, SEOL-.

However, interference can also be coupled in, for example by clocking other switches in the operating device, PFC switches, heating switches, etc. A further development of the invention thus proposes such short-term disturbances in the adaptation of the various Threshold values SOCP, SCCD should be ignored or not taken into account as far as possible. According to the invention, such disturbances are taken into account only stepwise or clockwise to a certain extent in which, in the course of the adaptation, a maximum variation of a threshold per cycle is determined.

Fig. 4 shows a corresponding embodiment of a filter 170. In each switching cycle of the half-bridge, the threshold values SOCP, SCCD are adaptively changed so that it can be prevented that the coupling of said interference due to misinterpretation leads to premature shutdown of the half-bridge or the operating device.

The filter 170 prevents such abrupt changes in the DC lamp voltage from leading to undesired error conditions OCP, CCD. The detected signal of the pin SDV lamp is supplied to the filter, for example via a low-pass filter. Optionally, an analog-to-digital converter (174) may detect and relay the signal. An input comparator 171 feeds an increment-decrement counter 172. A sampling unit 173 is preferably clocked with the clocked inverter 2, e.g. at a period of 50 μs. The sampling unit 173 provides the adaptation for the threshold values SOCP, SCCD to the output of the filter 170.

The input and output signals INPUT, OUTPUT of the filter 170 are in the Fig. 5, 6 shown. The input signal INPUT preferably corresponds to the detected DC component of the lamp voltage or outputs this value again. The output signal OUTPUT corresponds to the adjusted threshold value SOCP, SCCD or Variation of the threshold Δ2 or reflects these values.

On Fig. 5 takes the input signal INPUT at t = 0 s 20 and then remains constant until the time t = 0.010 s. At this time, the input signal INPUT rises to the value 30.

According to the invention, the maximum variation of the threshold value SOCP, SCCD is limited for each cycle. For example, the filter 170 limits the variation to the value 1 for each cycle. In other words, the thresholds can increase or decrease by a maximum of 1 within 50 μs, which corresponds to the clock speed of the inverter. At the in Fig. 5, 6 The values given for the input and output signals are preferably voltages in volts.

At the exit, after only 0.001 seconds, i. after 20 cycles, the input value of 20 is taken into account.

In Fig. 6 Meanwhile, an input signal is shown, which remains almost constant from t = 0 to t = 0.020 s. Only at t = 0.010 s results in a short-term erratic increase in the DC lamp voltage, which is due for example to a fault.

The value of the output signal increases rapidly, ie already after 0.0025 s, to the predetermined input value of 50. Thereafter, the output signal and thus also the threshold value SOCP, SCCD remain stable at the desired value. The erratic disturbance at t = 0.010 merely results in the output signal being increased by the maximum permissible value 1 for two cycles. After two cycles If the fault is over and the input signal drops back to the value 50. Accordingly, the output falls within two additional cycles to the desired value. The short-term disturbance thus has no negative influence on the error detection OCP, CCD.

The adaptive tracking of the threshold values SOCP, SCCD proposed by the invention is particularly advantageous in a state in which a certain EOL contribution is already delivered, but the EOL switch-off thresholds SEOL +, SEOLaber have not yet been reached.

The DC offset of the lamp voltage may be subject to certain fluctuations. However, according to the present invention, it is contemplated that these variations adaptively result in the corresponding shift of the turn-off threshold SOCP, SCCD in the next cycle.

Additionally or alternatively, also a possible DC offset at the input SDV lamp can be determined already in the phase before the ignition of the lamp and then taken into account in the operation of the lamp, ie after ignition, in the evaluations of the measurements and when setting the thresholds ,

LIST OF REFERENCE NUMBERS

1

control gear

2

inverter

3

Control circuit with internal DC power source

4

light element

5

load

6

storage capacitor

7

AC / DC converter

8th

filter

Q1

higher potential switch (HS = High Side)

Q2

potential lower switch (LS = low side)

R102

Measuring resistor in series with the half-bridge for measuring the half-bridge current

R104

Voltage divider resistor parallel to the light element for measuring the lamp voltage

SDV _lamp

Pin of the ASIC to which the measurement of the half-bridge current and the lamp voltage are supplied

SDVI _lamp

Pin of the ASIC to which the measurement of the half-bridge current, the lamp voltage and the lamp current are supplied

A

internal DC power source of the ASIC

R101

Measuring resistor ("shunt")

C101

AC filter

R107

Measuring resistor in series with the luminous element for measuring the lamp current

C62

coupling capacitor

L60

Throttle of the series resonant circuit

C63

Capacitor of the series resonant circuit

I _SW

Half-bridge current

iLamp

lamp current

Vlamp

lamp voltage

Claims (15)

1. Method for the operation of at least one light-emitting means (4), such as a gas discharge lamp, based on a clocked circuit (2), wherein, in order to detect a state, in particular an error state of the light-emitting means (4), a measuring signal, which represents a first electrical parameter with respect to the light-emitting means operation, is compared with a threshold value (SOCP), wherein the threshold value (SOCP) may be set as a function of a rectifier effect of the light-emitting means (4),
   characterized in that
   the measurement signal represents the current through a switch (Q2) of the clocked circuit (2) that is compared with the threshold value (SOCP) in order to detect an overcurrent (OCP), or that the threshold value (SCCD) serves to detect a capacitive operation of the light-emitting means (4).
2. Method according to claim 1,
   wherein the rectifier effect is determined by direct or indirect monitoring of the rectifier effect parameter, and
   the rectifier effect parameter represents the voltage over the light-emitting means (4), the light-emitting means current, the light-emitting means impedance and/or the power supplied by the light-emitting means (4).
3. Method according to claim 1,
   wherein the rectifier effect is detected by direct or indirect monitoring of a rectifier effect parameter, and
   the rectifier effect parameter represents the DC voltage (Sbase) over the light-emitting means (4), or the asymmetry of the lamp current.
4. Method according to one of the claims 2 to 3,
   wherein the threshold value (SOCP) is adjustable so that a variation (Δ1) of the rectifier effect parameter results in a corresponding variation (Δ2) of the threshold value (SOCP).
5. Method according to one of the claims 2 to 4,
   wherein the threshold value (SOCP) is adjustable at each clock pulse or at each period of the clocked circuit (2).
6. Method according to one of the claims 2 to 5,
   wherein a detected change of the rectifier effect parameter results in the adjustment of the threshold value (SOCP) in the next clock pulse of the clocked circuit (2).
7. Method according to one of the claims 2 to 6,
   wherein the maximum change in the threshold value (SOCP) is limited within a clock pulse.
8. Method according to one of the claims 2 to 7,
   wherein an error status (EOL) is triggered as soon as the rectifier effect parameter (Sbase) reaches a threshold value (SEOL+, SEOL-), or reaches it several times.
9. Method according to one of the preceding claims,
   wherein the threshold value serves to detect a voltage-free switching of the clocked circuit.
10. Method for operating at least one light-emitting means (4), such as a gas discharge lamp, based on a clocked circuit (2),
    wherein to detect an error state of the operation of the light-emitting means (4), a measuring signal representing an electrical parameter with respect to the light-emitting means operation, is compared with a threshold value (SOCP, SCCD),
    wherein the threshold value is adjustable as a function of a constant component of the light-emitting means voltage (Sbase)
    characterized in that
    the measurement signal represents the current through a switch (Q2) of the clocked circuit (2) that is compared with the threshold value (SOCP) in order to detect an overcurrent (OCP), or that the threshold value (SCCD) serves to detect a capacitive operation of the light-emitting means (4).
11. Method for operating at least one light-emitting means (4), such as, for example, a gas discharge lamp, wherein

    - a rectifier effect of the light-emitting means (4) is determined in such a way that an error state (EOL) may be derived from a comparison of a value (Sbase) representing this rectifier effect with a threshold value (SEOL+),

    - the determined rectifier effect is taken into account when monitoring a further error state.
12. Control circuit (3), in particular an ASIC or microcontroller, which is designed for a method according to one of the preceding claims.
13. Operating apparatus for light-emitting means, in particular for gas discharge lamps, comprising a control circuit according to claim 12.
14. Lighting system, comprising a control unit and at least one operating device, which is preferably connected thereto via a bus line, according to claim 13.
15. Circuit (1) for operating a light-emitting means (4), such as, for example, a gas discharge lamp, comprising

    - a half-bridge or full-bridge circuit (2) for providing a supply voltage for the at least one light-emitting means (4), and

    - a control circuit (3) for controlling the operation of the light-emitting means (4) and/or error detection,

    wherein a threshold value (SOCP) is compared with a threshold value (SOCP) to detect an error state of the operation of the light-emitting means (4), and the threshold value (SOCP) is adjustable as a function of a rectifier effect of the light-emitting means
    characterized in that
    the measuring signal represents the current through a switch (Q2) of the half-bridge or full-bridge circuit (2), that is compared with the threshold value (SOCP) in order to detect an overcurrent (OCP), or the threshold value (SCCD) serves to detect a capacitive operation of the light-emitting means (4).

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