EP2380408B1 - Detector circuit and method for controlling a fluorescent lamp - Google Patents

Description

The invention relates to a detector circuit, an electronic ballast and a method for controlling at least one fluorescent lamp.

A possible cause of failure of fluorescent lamps is a reduced emissivity of the electrodes (so-called "end-of-life" effect). This effect occurs at the end of the life of a fluorescent lamp on one of the two electrodes. As a result, the discharge current through the lamp flows more easily in one direction than in the opposite direction. The fluorescent lamp works in this case as a rectifier. In doing so, the emission-impoverished electrode heats up so much that high temperatures can occur at the lamp surface. In extreme cases, the glass bulb can melt in fluorescent lamps of small diameter.

An electronic ballast (ECG) to control the fluorescent lamp must detect this one such fault in time and either limit output current and output voltage to a non-critical value or turn off the fluorescent lamp.

The TOE must fulfill various control and monitoring tasks beyond the actual lamp operation. Separate circuit parts are required for such control and monitoring tasks, in particular depending on the wiring of the electronic ballast.

The object of the invention is to avoid the above-mentioned disadvantages and in particular an approach for an efficient and flexible electronic To provide ballast or a versatile detector circuit for controlling a lamp that perceives, for example, depending on the wiring control and / or monitoring tasks.

This object is achieved according to the features of the independent claims. Further developments of the invention will become apparent from the dependent claims.

To achieve the object, a detector circuit for controlling a fluorescent lamp is indicated, in which an inactive fluorescent lamp is detectable if after a start-up phase, a first signal at a first input and / or a second signal at a second input in a detection interval is / lie.

The fluorescent lamp is particularly inactive if it has not been ignited or extinguished.

This approach to detector circuitry allows for flexible deployment, e.g. in electronic ballasts of different wiring and / or with a different number of fluorescent lamps.

By way of example, the detection interval corresponds to a voltage interval in a range of approximately 2V to approximately 3V.

It is a further development that during the start-up phase it can be determined whether a fluorescent lamp or two fluorescent lamps are connected by the detector circuit comparing the voltages at the inputs.

It should be noted that the start-up phase comprises a period for filament monitoring and / or a time duration for preheating the at least one fluorescent lamp. During this start-up phase, preparatory measurements and Monitoring be performed before it comes to the ignition of at least one fluorescent lamp.

• dass zwei Leuchtstofflampen angeschlossen sind, falls die während der Anlaufphase verglichenen beiden Spannung an den Eingängen in.etwa gleich groß sind,
• wobei ansonsten nur eine Leuchtstofflampe angeschlossen ist.

It is also a development that the detector circuit is set up in such a way that it can be established that

• that two fluorescent lamps are connected if the two voltages compared at the inputs are approximately the same during the start-up phase,
• otherwise only one fluorescent lamp is connected.

Thus, the detector circuit can automatically detect whether it is used in one or the other case.

In particular, in the event that the voltages at the inputs differ by about a factor of two, the use of only one fluorescent lamp can be deduced. Accordingly, both comparisons (voltages at the inputs approximately equal or voltages at the inputs can be significantly different (about a factor of 2)) or only one of the two measurements can be used to determine if a fluorescent lamp is connected or if two fluorescent lamps are connected are.

• abhängig von dem ersten Signal an dem ersten Eingang und abhängig von dem zweiten Signal an dem zweiten Eingang eine Ansteuerung nach der Anlaufphase für den Fall einer angeschlossenen Leuchtstofflampe nach mindestens einem der folgenden Kriterien durchführbar ist:
• Falls das erste Signal oder das zweite Signal jeweils in einem ersten Spannungsintervall liegt, wird eine Ausgangsspannung verringert oder eine Frequenz der Ansteuerung erhöht;
• falls das erste Signal oder das zweite Signal jeweils in einem zweiten Spannungsintervall liegt und das jeweils andere Signal in einem zweiten oder dritten Spannungsintervall liegt, erfolgt eine Ansteuerung der Leuchtstofflampe mit einer Zündspannung;
• falls das erste Signal und das zweite Signal in dem dritten Spannungsintervall liegen, wird die Leuchtstofflampe angesteuert, insbesondere wird eine Ausgangsspannung an der Leuchtstofflampe überwacht;
• falls das erste Signal oder das zweite Signal jeweils in einem vierten Spannungsintervall liegen, wird die Ausgangsspannung verringert oder die Frequenz der Ansteuerung erhöht.

A next development is that

• depending on the first signal at the first input and depending on the second signal at the second input, a control after the start-up phase in the case of a connected fluorescent lamp according to at least one of the following criteria is feasible:
• If the first signal or the second signal is each in a first voltage interval, an output voltage is reduced or a frequency of the drive is increased;
• if the first signal or the second signal is in each case in a second voltage interval and the respective other signal lies in a second or third voltage interval, the fluorescent lamp is actuated with an ignition voltage;
• if the first signal and the second signal are in the third voltage interval, the fluorescent lamp is driven, in particular an output voltage is monitored on the fluorescent lamp;
• if the first signal or the second signal are each in a fourth voltage interval, the output voltage is reduced or the frequency of the control increases.

It should be noted that the above criteria may be used individually or in combination with each other.

• abhängig von dem ersten Signal an dem ersten Eingang und abhängig von dem zweiten Signal an dem zweiten Eingang eine Ansteuerung nach der Anlaufphase für den Fall zweier angeschlossener Leuchtstofflampen nach mindestens einem der folgenden Kriterien durchführbar ist:
  • Falls das erste Signal oder das zweite Signal jeweils in einem ersten Spannungsintervall liegt, wird eine Ausgangsspannung verringert oder eine Frequenz der Ansteuerung erhöht;
  • falls das erste Signal und das zweite Signal in einem zweiten Spannungsintervall liegt, erfolgt eine Ansteuerung der Leuchtstofflampe mit einer Zündspannung;
  • falls exklusiv das erste Signal oder exklusiv das zweite Signal in dem zweiten Spannungsintervall liegt und das jeweils andere Signal in einem dritten Spannungsintervall liegt, erfolgt eine Ansteuerung der Leuchtstofflampe mit einer reduzierten Zündspannung;
  • falls das erste Signal und das zweite Signal in dem dritten Spannungsintervall liegen, wird die Leuchtstofflampe angesteuert, insbesondere wird eine Ausgangsspannung an der Leuchtstofflampe überwacht;
  • falls das erste Signal oder das zweite Signal jeweils in einem vierten Spannungsintervall liegen, wird die Ausgangsspannung verringert oder die Frequenz der Ansteuerung erhöht.

One embodiment is that

• depending on the first signal at the first input and depending on the second signal at the second input, a control after the start-up phase for the case of two connected fluorescent lamps according to at least one of the following criteria is feasible:
  • If the first signal or the second signal is each in a first voltage interval, an output voltage is reduced or a frequency of the drive is increased;
  • if the first signal and the second signal is in a second voltage interval, the fluorescent lamp is actuated with an ignition voltage;
  • if exclusive the first signal or exclusive the second signal in the second voltage interval is and the other signal is in a third voltage interval, there is a control of the fluorescent lamp with a reduced ignition voltage;
  • if the first signal and the second signal are in the third voltage interval, the fluorescent lamp is driven, in particular an output voltage is monitored on the fluorescent lamp;
  • if the first signal or the second signal are each in a fourth voltage interval, the output voltage is reduced or the frequency of the control increases.

It should be noted here that the expression "exclusively the first signal or exclusively the second signal" corresponds to an EXOR combination of the first and the second signal.

The above-mentioned reduction of the output voltage may also include the possibility that an activation of the at least one fluorescent lamp is omitted or the detector circuit and / or the electronic ballast is / are switched off.

It should be noted that the above criteria may be used individually or in combination with each other.

• Erstes Spannungsintervall: Die Spannung ist größer als 3V;
• Zweites Spannungsintervall: Die Spannung liegt in einem Bereich von 2V bis 3V (jeweils einschließlich);
• Drittes Spannungsintervall: Die Spannung liegt in einem Bereich von 0,5V (einschließlich) bis 2V;
• Viertes Spannungsintervall: Die Spannung ist kleiner als 0,5V.

In particular, the voltage intervals are arranged adjacent to one another. For example, the following voltage intervals could be used:

• First voltage interval: The voltage is greater than 3V;
• Second voltage interval: The voltage is in a range of 2V to 3V (inclusive);
• Third voltage interval: The voltage is in a range of 0.5V (inclusive) to 2V;
• Fourth voltage interval: The voltage is less than 0.5V.

It is also a development that, depending on the first signal at the first input and depending on the second signal at the second input, the activation of the at least one fluorescent lamp, in particular via at least one half-bridge inverter, if during a start-up phase, the first signal and the second Signal are each greater than a first predetermined voltage and less than a second predetermined voltage.

The start-up phase is, in particular, a period of time before the activation of the at least one fluorescent lamp. Such a drive may e.g. by means of a half-bridge circuit (or by means of a half-bridge inverter), by means of a full-bridge circuit or by means of a push-pull circuit.

It should be noted that the first predetermined voltage is preferably smaller than the second predetermined voltage. In other words, the activation of the at least one fluorescent lamp takes place directly or indirectly (for example via the at least one half-bridge inverter) if the first and the second signal lie in an interval between the first predetermined voltage and the second predetermined voltage.

Thus, advantageously at least one coil of the at least one fluorescent lamp can be detected, wherein the detector circuit in different ECG topologies ("lamp-to-ground" or "Capacitor-to-ground" circuits) and in particular in combination with a fluorescent lamp or with two Fluorescent lamps can be used.

It should also be noted that the upper threshold corresponding to a high voltage (e.g., greater than the second predetermined voltage) on at least one of the two inputs may be equivalent to a high current flow in the detector circuit. By way of example, the detector circuit may have a current source which, in accordance with such a high voltage, loads a supply voltage of the detector circuit such that activation of the at least one fluorescent lamp can no longer take place. Thus, the high voltage at at least one of the two inputs alternatively or additionally corresponds to a high current, which is converted by the power source from the supply voltage and prevents activation of the at least one fluorescent lamp.

Another advantage of the present approach is that the detector circuit can be used flexibly and thus a large number of otherwise necessary circuit parts for control and monitoring tasks can be omitted.

So it is a development that the second predetermined voltage is predetermined by a power source.

In particular, it is a further development that at least one of the inputs is connected to the current source, wherein the current source loads a supply voltage as a function of at least one voltage at at least one of the inputs.

For example, the power source is designed as a controllable power source.

A further development is that the detector circuit for controlling the at least one fluorescent lamp in front of the Starting an electronic ballast is used.

The helix recognition is preferably used before an electronic ballast starts or before igniting a fluorescent lamp.

Another development is that no activation of the at least one fluorescent lamp, in particular via the at least one half-bridge inverter, takes place if during a start-up phase, the first signal or the second signal is greater than the second predetermined voltage is / if the first signal or second signal is less than the first predetermined voltage is / are.

In this case, the coils were (still) not recognized correctly, the at least one fluorescent lamp is not yet activated, or waiting for the ECG in particular until the coils are contacted correctly.

This has the particular advantage that ignition of the fluorescent lamp does not take place if it is inserted only on one side in a socket and thus, e.g. when changing the fluorescent lamp, the user can not get an electric shock.

• im Fall einer Beschaltung mit einer Leuchtstofflampe das erste Signal über einen Spannungsteiler einer Spannung an der Leuchtstofflampe entspricht und das zweite Signal über einen Spannungsteiler einer Vergleichsspannung entspricht;
• im Fall einer Beschaltung mit zwei Leuchtstofflampen das erste Signal über einen Spannungsteiler einer Spannung an der ersten Leuchtstofflampe entspricht und das zweite Signal über einen Spannungsteiler einer Spannung an einer zweiten Leuchtstofflampe entspricht.

In particular, it is a training that

• in the case of a circuit with a fluorescent lamp, the first signal via a voltage divider corresponds to a voltage at the fluorescent lamp and the second signal via a voltage divider corresponds to a comparison voltage;
• in the case of a circuit with two fluorescent lamps, the first signal via a voltage divider corresponds to a voltage at the first fluorescent lamp and the second signal via a voltage divider corresponds to a voltage at a second fluorescent lamp.

Thus, advantageously, the detector circuit can be used in a circuit with a fluorescent lamp or in a circuit with two fluorescent lamps.

It is also a development that the at least one fluorescent lamp in a Capacitor-to-Ground topology or in a lamp-to-ground topology is operable.

Thus, it is possible to have the detector circuit in different topologies, i. Connections of at least one fluorescent lamp to use. The detector circuit derives the necessary behavior, or the required control and monitoring tasks, in both forms of wiring correctly.

An alternative embodiment is that comparators are provided for determining the voltage intervals.

A next embodiment is that by means of a microcontroller, the signals of the inputs can be determined.

Accordingly, the comparators with associated switching logic can be used to detect the threshold values. Alternatively or additionally, at least one microcontroller, possibly in conjunction with at least one analog-to-digital converter (A / D converter), can be used to detect the signals applied to the inputs and to evaluate them appropriately.

It is also an embodiment that the at least one fluorescent lamp can be controlled by means of at least one half-bridge via a voltage-controlled oscillator.

For example, the at least one half-bridge or the voltage-controlled oscillator can be part of the detector circuit or part of the electronic ballast for operating the at least one fluorescent lamp. In particular, the detector circuit may be a part of the electronic ballast or associated with this.

A development consists in that at least one input is connected to a controllable current source, wherein the controllable current source loads a supply voltage as a function of at least one voltage at at least one input.

In this respect, depending on a voltage applied to at least one of the inputs, the current source can load the supply voltage with a correspondingly high current, so that, for example, activation of the at least one fluorescent lamp does not occur due to the high voltage at the affected input (or can no longer occur).

Another embodiment is that the detector circuit is formed at least partially in the form of an integrated circuit.

The above object is also achieved by an electronic ballast for controlling at least one fluorescent lamp comprising a detector circuit as described herein.

The ECG in particular provides functions for dimming the at least one fluorescent lamp and for end-of-life detection. On the basis of the detector circuit can be detected in time a fault in the operation of a fluorescent lamp and another Control of this lamp is omitted (ie the fluorescent lamp are switched inactive).

Furthermore, it is an embodiment that the circuit arrangement can be used for end-of-life detection and for switching off the fluorescent lamp.

• Einen Halbbrückenwechselrichter mit mindestens einem nachgeschalteten Lastkreis,
• mindestens einen Koppelkondensator, der mit dem Lastkreis und mit dem Halbbrückenwechselrichter verbunden ist,
• wobei der Lastkreis Anschlüsse für die mindestens eine Leuchtstofflampe aufweist,
• eine Detektorschaltung nach einem der Ansprüche 1 bis 15 zur Ansteuerung des Halbbrückenwechselrichters.

Furthermore, the above-mentioned object is achieved by a circuit arrangement for controlling at least one fluorescent lamp, comprising:

• A half-bridge inverter with at least one downstream load circuit,
• at least one coupling capacitor, which is connected to the load circuit and to the half-bridge inverter,
• wherein the load circuit has connections for the at least one fluorescent lamp,
• a detector circuit according to one of claims 1 to 15 for driving the half-bridge inverter.

The above object is also achieved by a method for operating the detector circuit according to the embodiments made herein.

Embodiments of the invention are illustrated and explained below with reference to the drawings.

Fig.1

beispielhaft einen Aufbau einer Kontrollschaltung zur Ansteuerung mindestens einer Leuchtstofflampe;

Fig.2

ein EVG mit einer Leuchtstofflampe in einer "Capacitor-to-Ground" (Kondensator-nach-Masse) Topologie;

Fig.3

ein EVG mit zwei Leuchtstofflampen in einer "Capacitor-to-Ground" (Kondensator-nach-Masse) Topologie;

Fig.4

ein EVG mit einer Leuchtstofflampe in einer "Lamp-to-Ground" (Lampe-nach-Masse) Topologie;

Fig.5

ein EVG mit zwei Leuchtstofflampen in einer "Lamp-to-Ground" (Lampe-nach-Masse) Topologie.

Show it:

Fig.1

exemplified a structure of a control circuit for controlling at least one fluorescent lamp;

Fig.2

an ECG with a fluorescent lamp in a Capacitor-to-Ground topology;

Figure 3

an ECG with two fluorescent lamps in a Capacitor-to-Ground topology;

Figure 4

an ECG with a fluorescent lamp in a "lamp-to-ground"topology;

Figure 5

an ECG with two fluorescent lamps in a "lamp-to-ground" topology.

Fig.1 shows an example of a structure of a control circuit for controlling at least one fluorescent lamp.

Fig.1 comprises a plurality of comparators Comp11, Comp12, Comp13, Comp21, Comp22, Comp23, Comp31 and Comp32, the outputs of which are connected to a logic unit 101. The logic unit 101 controls a voltage-controlled oscillator VCO 102, at the output of which two control signals LSG, HSG, for example for controlling electronic switches of a half-bridge circuit or of a half-bridge inverter, are provided.

The control circuit may be part of an end-of-life circuit, in particular an end-of-life detector circuit for operating and / or monitoring at least one fluorescent lamp.

The control circuit may be part of an integrated circuit that can be used to control an electronic ballast (ECG) or at least one half-bridge.

The control circuit according to Fig.1 has two inputs EOL1, EOL2, and an input for a supply voltage VCC. The two inputs EOL1 and EOL2 are suitable for applying a voltage to or in connection with a Fluorescent lamp to detect. The respectively detected per input EOL1 and / or EOL2 voltage can be suitably evaluated by the control circuit.

Exemplary for this purpose is the control circuit according to Fig.1 is configured as follows: The input EOL1 is connected to an input of the comparator Comp31, the other input of the comparator Comp31 is connected to a node 108. The node 108 is connected via a resistor 106 to the input EOL2. Also, the node 108 is connected through a resistor 105 to ground. Furthermore, the input EOL2 is connected to an input of the comparator Comp32 whose other input is connected to a node 109. The node 109 is connected via a resistor 104 to ground and connected via a resistor to the input EOL1.

Input EOL1 is connected to one input each of comparators Comp11, Comp12 and Comp13. The other input of the comparator Comp11 is at a potential of 3V, the other input of the comparator Comp12 is at a potential of 2V and the other input of the comparator Comp13 is at a potential of 0.5V.

The input EOL2 is connected to one input each of the comparators Comp21, Comp22 and Comp23. The other input of the comparator Comp21 is at a potential of 3V, the other input of the comparator Comp22 is at a potential of 2V and the other input of the comparator Comp23 is at a potential of 0.5V.

It can be determined by means of the comparators in which of at least four voltage ranges the input voltages are located at the inputs EOL1 and EOL2.

The input EOL1 is connected to one input of a current source 107 and the input EOL2 is connected to another input of the Power source 107 connected. The power source is further connected to the supply voltage VCC. The supply voltage VCC is connected to the logic unit 101 via a Zener diode D1 and a Zener diode D2 is arranged between the supply voltage VCC and ground.

Thus, both inputs EOL1 and EOL2 or only one of the two inputs can be connected to the controllable current source 107, which charges the supply VCC depending on the voltages at the inputs EOL1 and EOL2. About the Zener diode D1, the logic unit 101 is enabled to drive the VCO 102 when the supply voltage VCC exceeds a predetermined value. The Zener diode D2 prevents further increase of this supply voltage VCC.

In the following, exemplary circuit arrangements of electronic ballasts (ECG) with one or with two fluorescent lamps in different circuits will be described. Each of the circuit arrangements has the in Fig.1 shown and explained above control circuit in the form of a so-called "control circuit" on.

Basically, with regard to the circuit arrangements, the fluorescent lamps shown need not be part of the electronic ballast, but preferably terminals (for example sockets) are provided which can be contacted with the fluorescent lamps.

ECG with a fluorescent lamp and "Capacitor-to-Ground" circuit

Fig.2 shows an ECG with a fluorescent lamp in a "Capacitor-to-Ground" topology.

Fig.2 shows a circuit block 201, which is also found in the subsequent circuits and there is designated as circuit block 201. By way of example, the circuit block 201 will be described below.

A supply voltage or intermediate circuit voltage VBus is connected between ground and a node 202. The node 202 is connected to the drain terminal of an n-channel MOSFET Q1, its source terminal to a node HB and to the drain terminal of an n-channel MOSFET Q2 connected is. The source terminal of the Mosfet Q2 is connected to ground. The gate terminal of the MOSFET Q1 is connected to the output LSG of the control circuit 204, and the gate terminal of the MOSFET Q2 is connected to the output HSG of the control circuit 204. The node HB is connected to a node 203 via a coil L1 and the node 203 is connected to ground via a capacitor C1.

Thus, the circuit block 201 is connected on the one hand to the control circuit 204 and on the other hand it is connected via the nodes 202 and 203 with the remaining circuitry.

According to Fig.2 The node 202 is connected via a resistor R11 to the input for the supply voltage VCC of the control circuit 204. The node 202 is connected via a resistor R21 to a terminal 205 of the filament of the lamp Lamp1. The other terminal 206 of the coil is connected via a resistor R22 to the input EOL1 and the input EOL1 is connected via a resistor R23 to ground. Also, the terminal 206 is connected to ground via a capacitor C2. The node 202 is connected via a resistor R31 to the input EOL2 and the input EOL2 is connected via a resistor R32 to ground. The node 203 is connected to a terminal 207 of a filament of the lamp Lamp1.

ECG with two fluorescent lamps and "Capacitor-to-Ground" circuit

Figure 3 shows an ECG with two fluorescent lamps in a "Capacitor-to-Ground" topology.

According to the comments to Fig.2 the circuit block 201 is provided with the two nodes 202 and 203.

The electronic ballast is shown as an example with two fluorescent lamps Lamp1 and Lamp2. These may be versions for inserting the fluorescent lamps. The fluorescent lamps each have two coils each with two terminals. Thus, the fluorescent lamp Lamp1 has terminals 301 and 302 for connection to a first coil, and terminals 303 and 304 for connection to a second coil. Accordingly, the fluorescent lamp Lamp2 has terminals 305 and 306 for connection to a first coil and terminals 307 and 308 for connection to a second coil.

The node 202 is connected to the terminal 306 via a resistor R11, to the terminal 301 via a resistor R12, to the terminal 307 via a resistor R21, and to the terminal 303 via a resistor R31.

The node 203 is connected to the terminal 302, to the terminal 305 and via a resistor R13 to the input for the supply voltage VCC of the control circuit 204.

The terminal 304 is connected to a node 309 via the first coil of a transformer T1, and the terminal 308 is connected to a node 310 via the second coil of the transformer T1.

The node 309 is connected to ground via a capacitor C3. Furthermore, the node 309 is connected via a resistor R32 to the input EOL1, wherein the input EOL1 is connected via a resistor R33 to ground.

The node 310 is connected to ground via a capacitor C2. Furthermore, the node 310 is connected via a resistor R22 to the input EOL2, wherein the input EOL2 is connected via a resistor R23 to ground.

ECG with a fluorescent lamp and "lamp-to-ground" circuit

Figure 4 shows an ECG with a fluorescent lamp in a "lamp-to-ground" topology.

According to the comments to Fig.2 the circuit block 201 is provided with the two nodes 202 and 203.

The node 202 is connected via a resistor R11 to the input for the supply voltage VCC of the control circuit 204.

The input of the supply voltage VCC is connected via a resistor R23 to a node 401 and via a resistor R33 to the input EOL2. The input EOL2 is connected to ground via a resistor R34.

The node 203 is connected via a parallel connection of a resistor R21 and a capacitor C2 to a terminal 402 for a first filament of a fluorescent lamp Lamp1 and via a resistor R22 to the node 401. The node 401 is connected to the input EOL1 and via a resistor R24 to a terminal 404 for a second one Spiral of the fluorescent lamp Lamp2 connected. A terminal 403 for the second filament of the fluorescent lamp is connected to ground.

ECG with two fluorescent lamps and "lamp-to-ground" circuit

Figure 5 shows an ECG with two fluorescent lamps in a "lamp-to-ground" topology.

According to the comments to Fig.2 the circuit block 201 is provided with the two nodes 202 and 203.

The electronic ballast is shown as an example with two fluorescent lamps Lamp1 and Lamp2. These may be versions for inserting the fluorescent lamps. The fluorescent lamps each have two coils each with two terminals. Thus, the fluorescent lamp Lamp1 has terminals 501 and 502 for connection to a first coil, and terminals 503 and 504 for connection to a second coil. Accordingly, the fluorescent lamp Lamp2 has terminals 505 and 506 for connection to a first coil and terminals 507 and 508 for connection to a second coil.

The node 202 is connected via a resistor R11 to the input for the supply voltage VCC of the control circuit 204.

The input for the supply voltage VCC of the control circuit 204 is connected via a resistor R23 to the input EOL1 and via a resistor R33 to the input EOL2.

The node 203 is connected in parallel with a resistor R31 and a capacitor C3 with a node 510 and connected via a parallel connection of a resistor R21 and a capacitor C2 to a node 509.

The node 509 is connected via a resistor R22 to the input EOL1. The node 510 is connected to the input EOL2 via a resistor R32.

Furthermore, the node 509 is connected to the terminal 502 via a first coil of a transformer T1. The node 510 is connected to the terminal 506 via a second coil of the transformer T1.

The input EOL1 is connected to the terminal 503 via a resistor R24 and the input EOL2 is connected to the terminal 508 via a resistor R34. The two terminals 504 and 507 are connected to ground.

Dimensioning of the voltage divider

The voltage dividers (R21, R22 or R31, R32) connected to a filament of the fluorescent lamp and to a coupling capacitor (C2, C3) are set so that the potential of this filament during operation of the electronic ballast (Vbus = 400 V, half-bridge transistors are driven, Potential at the node HB is about 200V on average over time) as long as the lamp is not burning, well above the potential of the node HB, eg in about 360V.

The potential of this coil is further divided down and fed to an EOL input, that the voltage at this EOL input in the operation of the ECG is above 2V when the lamp is not burning (in this case, the resistance of the lamp is infinitely large) and under 2V drops when the lamp is lit (in this case, the lamp resistance is in a range of 100ΩΩ to 100kΩ, for example).

In the circuit arrangements with only one fluorescent lamp ( Fig.2 . Figure 4 ), the input EOL2 is connected to a voltage divider that divides a fixed voltage so that when operating at high lamp power (resistance of the lamp, for example, in a range of 100Ω to 1kΩ), both inputs EOL1 and EOL2 will have (approximately) the same input voltage.

In the circuit arrangement according to Fig.2 For this purpose, the intermediate circuit voltage Vbus is used, because the voltage at the input EOL1 also depends on the intermediate circuit voltage Vbus. Accordingly, in the circuit according to Figure 4 divided the supply voltage VCC, because here the voltage at EOL1 depends on this supply voltage VCC.

Wendel query

An ECG that has shut down due to a lamp failure should re-start automatically after the lamp has been replaced.

For this purpose, the electrical continuity of at least one of the two lamp filaments is controlled: If the filament is interrupted, the switch-off function can be reset, and the ECG can be started again if the filament is turned again.

For safety reasons, it is advantageous that the electronic ballast does not start if the lamp is only inserted on one side into a socket on which ignition voltage is generated. Otherwise, if the terminals on the other side of the lamp are touched, the lamp would ignite and could cause an electric shock.

The ignition voltage is generated on a socket which is connected to the resonant circuit (L1, C1). In the case of the TOE with two fluorescent lamps ( Figure 3 . Figure 5 ) also on a socket which is connected to the transformer T1 (balancing transformer). The respective lamp sockets opposite these sockets are preferably tested for electrical continuity.

The helical interrogation is preferably carried out before or at the start of the TOE. In this case, the half-bridge transistors (Q1, Q2) are not yet activated, the intermediate circuit voltage (Vbus) is, for example, in a range of 176V to 375V depending on the mains voltage. The lamps (Lamp1, Lamp2) are not yet burning (i.e., the resistance of the respective lamp is infinite).

When the coils are inserted and in order, the voltage at the inputs EOL1 and EOL2 is in the range of about 0.5V to about 3V.

If, on the other hand, a helix is missing, the corresponding voltage at the inputs EOL1 and EOL2 in the circuits according to FIG Fig.2 and Figure 3 each OV, in the circuits according to Figure 4 and Figure 5 the voltage at the inputs EOL1 and EOL2 is greater than 3V. In both cases (0V and greater than 3V), the TOE should not start. Only when the voltages at the inputs EOL1 and EOL2 are within a range of 0.5V to 3V, the electronic ballast starts.

The following table summarizes the helical interrogation before starting the TOE: inputs condition reason reaction EOL1 OR EOL2 > 3V Wendel is missing waiting EOL1 AND EOL2 0,5V - 3V Filing ok start EOL1 OR EOL2 <0, 5V Wendel is missing waiting

The first column of the above table shows which inputs EOL1 and / or EOL2 the Meet conditions according to the second voltage. Depending on the state of the voltages at the inputs EOL1 and / or EOL2, the third column shows the cause and the fourth column comprises the reaction of the detector circuit or the ECG.

A special feature includes the circuit according to Figure 3 : Here it is advisable to monitor all four coils of both lamps. For this purpose, the supply current of the control circuit via the resistors R11 and R12 and via both coils (terminals 301, 302 and 305, 306) of the resonant circuit lamp side out. In order to minimize the losses, the resistors R11 and R12 may be made equal and twice as large as the resistor R13. If one of the two coils is missing, the supply current drops to 2/3 of its normal value. So that this small change can be evaluated with a large mains voltage range between 176V and 375V, the supply current of the control circuit is made independent of the mains voltage. This is achieved by the current source 107, which additionally loads the supply depending on the mains voltage (see Fig.1 and related description). The ECG starts only when the remaining supply current of the control circuit does not fall below a certain minimum value (eg 150μA).

The current source 107 is controlled either by the greater of the voltages at the inputs EOL1 and EOL2, which are respectively proportional to the intermediate circuit voltage VBus, or by the voltage at the input EOL1.

Thus, it is advantageous that at least one missing filament of a fluorescent lamp can be detected in a lower and in an upper voltage range and thus the control circuit can be used universally for different ECG topologies ("lamp-to-ground" circuit, "Capacitor"). to-Ground "-Beschaltung).

ignition

If a lamp is not burning or if a lamp goes out during operation for any reason, it should be ignited.

For this, the ECG must provide the required ignition voltage, depending on the lamp, up to 750V. A non-burning lamp is detected by the fact that the voltage at the corresponding input EOL1 and / or EOL2 is more than 2V but less than 3V.

In a particular dimmable electronic ballast with two lamps, the ignition voltage of a lamp is almost doubled by the balancing transformer T1 when the other lamp is already burning. In this state, the balancing transformer T1 is heavily loaded due to the high voltage and the high level of control of the core. Therefore, a reduction of the ignition voltage is appropriate for the duration of this condition.

In this case, the voltage at one of the inputs EOL1 or EOL2 is in a range of 0.5V to 2V, the voltage at the other input EOL2 or EOL1 is in a range between 2V and 3V (comparable to the case of the single-lamp ECG if this one lamp does not burn).

In order to allow a correct reaction, it is preferable to determine whether the control circuit is operated with one lamp or with two lamps. This can be determined, in particular, as long as no lamp is burning, ie during a preheating phase: in the case of the electronic ballast with one lamp, the voltages at the inputs EOL1 and EOL2 differ approximately by a factor of two, for the electronic ballast with two lamps Voltages at the inputs EOL1 and EOL2 during the pre-heating phase are approximately the same. The determination of Voltages and their relation to one another can be determined by means of the control circuit, eg using the comparators Comp31 and Comp32 (see Fig.1 ) respectively.

Monitoring the output voltage U _out

In normal operation of the ECG (lamp burning) its output voltage should have a certain value, e.g. 300V or 430V, do not exceed permanently.

To ensure this, the same controlled variable as used for ignition control, but the sensitivity can be increased accordingly.

The "normal operation" state can be detected by means of the voltages at the inputs EOL1 and EOL2, and both are then in the range of 0.5V to 2V.

A special burden for the electronic ballast is the hard rectifying operation as tested according to EN 61000-3-2. Here the lamp is a diode connected in series and thus the coupling capacitor (C2, C3) heavily reloaded. In this operating mode, the electronic ballast can be relieved by increasing the operating frequency (far) above the resonance frequency of the output resonant circuit (L1, C1).

The following tables show a possibility for ignition control and for monitoring the output voltage of an electronic ballast after starting the electronic ballast in the case of the electronic ballast with a lamp: inputs condition reason reaction 1 OR 2 > 3V hard rectifying Increase frequency 1 OR 2 2V - 3V Lamp does not burn full ignition voltage 1 AND 2 0,5V - 2V normal operation U _out monitoring 1 OR 2 <0, 5V hard rectifying Increase frequency and in the case of the electronic ballast with two lamps: inputs condition reason reaction 1 OR 2 > 3V hard rectifying Increase frequency 1 AND 2 2V - 3V both lamps do not burn full ignition voltage 1 EXOR 2 2V - 3V a lamp does not burn reduced ignition voltage 1 AND 2 0,5V - 2V normal operation U _out monitoring 1 OR 2 <0, 5V hard rectifying Increase frequency The same comparator thresholds can be used for the functions spiral detection, ignition control and monitoring of the output voltage. This simplifies the structure of the respective circuit. It is also possible to provide separate comparator thresholds for each functionality (or parts thereof).

Instead of the comparators and the switching logic, a microcontroller with A / D converter can be provided, which evaluates the signals at the inputs EOL1 and EOL2 suitable and controls the at least one half-bridge or the at least one fluorescent lamp accordingly.

Claims (12)

1. Detector circuit for actuating at least one fluorescent lamp (Lamp1, Lamp2), in which a fluorescent lamp which has not started or has been extinguished can be detected if, after a runup phase, a first signal is present at a first input (EOL1) and/or a second signal is present at a second input (EOL2) in an identification interval,
   wherein

   - in the case of circuitry with only one fluorescent lamp, the first signal via a voltage divider corresponds to a voltage at the fluorescent lamp and the second signal via a voltage divider corresponds to a comparison voltage;

   - and in the case of circuitry with two fluorescent lamps, the first signal via a voltage divider corresponds to a voltage at the first fluorescent lamp and the second signal via a voltage divider corresponds to a voltage at a second fluorescent lamp,

   wherein the detector circuit is characterized in that in the detector circuit, depending on the first signal at the first input (EOL1) and depending on the second signal at the second input (EOL2), actuation after the runup phase for the case of one connected fluorescent lamp can be implemented in accordance with at least one of the following criteria:

   - if the first signal or the second signal is in each case within a first voltage interval, an output voltage is reduced or a frequency of the actuation is increased;

   - if the first signal or the second signal is in each case within a second voltage interval and the respective other signal is within a second or third voltage interval, actuation of the fluorescent lamp with a starting voltage takes place;

   - if the first signal and the second signal are within the third voltage interval, the fluorescent lamp is actuated, in particular an output voltage at the fluorescent lamp is monitored;

   - if the first signal or the second signal is in each case within a fourth voltage interval, the output voltage is reduced or the frequency of the actuation is increased;

   and in that, in the detector circuit, depending on the first signal at the first input (EOL1) and depending on the second signal at the second input (EOL2), actuation after the runup phase for the case of two connected fluorescent lamps can be implemented in accordance with at least one of the following criteria:

   - if the first signal or the second signal is in each case within a first voltage interval, an output voltage is reduced or a frequency of the actuation is increased;

   - if the first signal and the second signal are within a second voltage interval, actuation of the fluorescent lamp with a starting voltage takes place;

   - if exclusively the first signal or exclusively the second signal is within the second voltage interval and the respective other signal is within a third voltage interval, actuation of the fluorescent lamp with a reduced starting voltage takes place;

   - if the first signal and the second signal are within the third voltage interval, the fluorescent lamp is actuated, in particular an output voltage at the fluorescent lamp is monitored;

   - if the first signal or the second signal is in each case within a fourth voltage interval, the output voltage is reduced or the frequency of the actuation is increased.
2. Detector circuit according to Claim 1, in which it is possible to establish during the runup phase whether one fluorescent lamp or two fluorescent lamps are connected by virtue of the detector circuit comparing the voltages at the inputs with one another.
3. Detector circuit according to Claim 2, which is designed in such a way that it is possible to establish

   - that two fluorescent lamps are connected if the two voltages, compared during the runup phase, at the inputs are approximately equal in value,

   - wherein otherwise only one fluorescent lamp is connected.
4. Detector circuit according to one of the preceding claims,

   - in which, depending on the first signal at the first input (EOL1) and depending on the second signal at the second input (EOL2), actuation of the at least one fluorescent lamp is performed, in particular via at least one half-bridge inverter (Q1, Q2), if, during a runup phase, the first signal and the second signal are each greater than a first predetermined voltage and less than a second predetermined voltage.
5. Detector circuit according to Claim 4, in which the second predetermined voltage is predetermined by a current source (107).
6. Detector circuit according to Claim 5, in which at least one of the inputs (EOL1, EOL2) is connected to the current source (107), wherein the current source (107) applies a supply voltage depending on at least one voltage at at least one of the inputs (EOL1, EOL2).
7. Detector circuit according to one of Claims 4 to 6 for actuating the at least one fluorescent lamp prior to starting of an electronic ballast.
8. Detector circuit according to one of Claims 4 to 7, in which there is no actuation of the at least one fluorescent lamp, in particular via the at least one half-bridge inverter, if, during the runup phase, the first signal or the second signal is/are greater than the second predetermined voltage or if the first signal or the second signal is/are less than the first predetermined voltage.
9. Detector circuit according to one of the preceding claims, in which the at least one fluorescent lamp can be operated with a capacitor-to-ground topology or a lamp-to-ground topology.
10. Detector circuit according to one of the preceding claims, in which at least one input (EOL1, EOL2) is connected to a controllable current source (107), wherein the controllable current source loads a supply voltage depending on at least one voltage at at least one input.
11. Circuit arrangement for actuating at least one fluorescent lamp, comprising:

    - a half-bridge inverter with at least one downstream load circuit,

    - at least one coupling capacitor, which is connected to the load circuit and to the half-bridge inverter,

    - wherein the load circuit has connections for the at least one fluorescent lamp,

    - a detector circuit according to one of Claims 1 to 10 for actuating the half-bridge inverter.
12. Method for actuating at least one fluorescent lamp (Lamp1, Lamp2), in which a fluorescent lamp which has not been started or has been extinguished can be detected if, after a runup phase, a first signal is present at a first input (EOL1) and/or a second signal is present at a second input (EOL2) in an identification interval,

    - in the case of circuitry with only one fluorescent lamp, the first signal via a voltage divider corresponds to a voltage at the fluorescent lamp and the second signal via a voltage divider corresponds to a comparison voltage;

    - and in the case of circuitry with two fluorescent lamps, the first signal via a voltage divider corresponds to a voltage at the first fluorescent lamp and the second signal via a voltage divider corresponds to a voltage across a second fluorescent lamp,

    wherein the method is characterized in that
    depending on the first signal at the first input (EOL1) and depending on the second signal at the second input (EOL2), after the runup phase, for the case of one connected fluorescent lamp at least the following steps are implemented:

    - if the first signal or the second signal is in each case within a first voltage interval, an output voltage is reduced or a frequency of the actuation is increased;

    - if the first signal or the second signal is in each case within a second voltage interval and the respective other signal is within a second or third voltage interval, actuation of the fluorescent lamp with a starting voltage takes place;

    - if the first signal and the second signal are within the third voltage interval, the fluorescent lamp is actuated, in particular an output voltage at the fluorescent lamp is monitored;

    - if the first signal or the second signal is in each case within a fourth voltage interval, the output voltage is reduced or the frequency of the actuation is increased;

    and in that, depending on the first signal at the first input (EOL1) and depending on the second signal at the second input (EOL2), after the runup phase, for the case of two connected fluorescent lamps at least the following steps are implemented:

    - if the first signal or the second signal is in each case within a first voltage interval, an output voltage is reduced or a frequency for the actuation is increased;

    - if the first signal and the second signal are in a second voltage interval, actuation of the fluorescent lamp with a starting voltage takes place;

    - if exclusively the first signal or exclusively the second signal is in the second voltage interval and the respective other signal is within a third voltage interval, actuation of the fluorescent lamp is performed with a reduced starting voltage;

    - if the first signal and the second signal are within the third voltage interval, the fluorescent lamp is actuated, in particular an output voltage at the fluorescent lamp is monitored;

    - if the first signal or the second signal is in each case within a fourth voltage interval, the output voltage is reduced or the frequency of the actuation is increased.

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