EP0989786B1 - Process and circuit for controlling the light intensity and the behaviour of gas discharge lamps - Google Patents

Abstract

A variable frequency inverter (30) supplies a load circuit (40), incorporating two fluorescent lamps (LA1, LA2). An integrated control circuit (17) includes a transceiver (10), to which commands are addressed for adjustment of the brightness and operational mode. With the lamps switched off, the inverter (30) is switched by a driver circuit (31) into SLEEP mode either immediately or after a preset delay, to be reactivated by reception of a fresh brightness command. It is fed from the mains via an on/off switch (S1) and a rectifier (20).

Description

The present invention relates to a method and a circuit arrangement for Control of the brightness and operating behavior of gas discharge lamps.

Electronic ballasts of modern design are used to control Fluorescent lamps. On the one hand, the fluorescent lamps are gentler operated and on the other hand, the efficiency of such lamp types be raised. An electronic ballast regularly has the following features:

A supply voltage, which can be a direct or alternating voltage, is fed to a rectifier and an intermediate capacitor via a mains input filter. If the device is operated exclusively with DC voltage, the rectifier can also be omitted. A high intermediate circuit voltage U _{0 is} formed on the intermediate circuit capacitor, which is of the order of magnitude of approximately 300 V with a conventional mains voltage supply of 220 V. An AC voltage generator is connected to the DC link, which is formed by a half-bridge or full-bridge inverter. It outputs a frequency-variable output voltage to an output load circuit which, unless a half-bridge circuit with an artificial voltage means tap is provided, has a series resonance circuit. The discharge path of the gas discharge lamp or fluorescent lamp to be controlled lies in the series with the series resonance circuit.

The output frequency of the inverter is approximately 10 kHz to 50 kHz.

At the frequencies mentioned, the efficiency of the connected Fluorescent lamps increased compared to operation on the 50 Hz supply network. An increased level of yield is achieved with the same electrical power consumption. Furthermore, due to the high frequency, the inverter output side Inductance of the series resonance circuit can be kept small. Finally, the variable frequency control a brightness control of the above - on the normal network Difficult to control (dimmable) fluorescent lamp. Come in addition finally that the frequency control also ignites the fluorescent lamp can be prepared and initiated.

To protect the fluorescent lamps is also part of the aforementioned ignition process a so-called warm start, in which the heating filaments of the fluorescent lamp are preheated before the lamp due to resonance with a high Ignition voltage is applied to the ignition and thus to operate the Gas discharge lamp leads. The variation in frequency, which is the ignition controlled, also allows operation of the gas discharge lamp Frequency shift an almost infinitely variable brightness control within wide limits. Such stepless and continuous control of the brightness requires due to the negative internal resistance of the fluorescent lamp in operation Activities.

An essential point of view for the development of a modern electronic ballast therefore on the one hand the most versatile possible control, in particular one Brightness control. On the other hand, it is a concern of modern electronic ballasts, one Comfortable handling and operation of many decentrally arranged light sources guarantee. This is especially true with regard to large projects where extensive Lighting systems with a large number of light sources must be installed.

A ballast described in US-4,523,128 has one Control device on the over the power supply line using Powerline Carrier Procedure (PLC) digital control commands are supplied. These control commands include u. a. Switch-on commands and dimming value commands for regulating the brightness of the Lamp. They are decrypted in a decoding device and converted into control signals Control of the inverter implemented so that the desired lamp brightness is achieved. Furthermore, the lamp and the inverter are received when a Shutdown command decommissioned in this state (SLEEP operating state) if possible to consume little energy.

FR 2 417 876 shows a ballast that if an operating AC voltage fails, it automatically switches to a emergency power supply passes over and performs an ignition process.

DE 3 518 063 A1 shows an operating circuit for Fluorescent lamps, with an emergency power supply via the usual mains voltage line.

It is therefore an object of the present invention to provide a method for controlling the Holiness and the operating behavior of gas discharge lamps, in which the Lamp even in the event of failure of an AC supply voltage remains operational.

The object is achieved by a method according to claim 1 or by a Circuit arrangement according to claim 2 solved.

The control and / or regulating device is preferably in the presence of the SLEEP operation corresponding switch-off command at the same time as the AC generator or shutdown slightly delayed. Only on receipt a new brightness command is then together with the AC generator reactivated.

In addition to the energy-saving SLEEP operation, the control and Control device also a brightness-controlled dimming (DIMM). In addition to The resulting comfortable brightness control allows the control and Finally, the control device also specifically increases the service life of the Fluorescent lamps and a granting of security interests. With your help For example, the operating behavior and the respective operating state of the fluorescent lamps supplied with an electronic ballast can be precisely controlled and monitored. This is how the warm start, ignition, dimming and switch-off process (IGNITION, DIMM, OFF, A) lined up with high precision and gentle on the lamp. Unacceptable Operating conditions are avoided, before a respective ignition is carried out for a sufficient preheating of the heating coils is ensured.

Based on the drawing, an embodiment of the invention is below explained in more detail.

Fig. 1

ein Blockschaltbild eines EVG's gemäß der vorliegenden Erfindung,

Fig. 2

ein Blockschaltbild eines Systemgedankens, bei dem mehrere dezentrale EVG's mit einem zentralen Steuergerät über eine Busleitung verbunden sind,

Fig. 3

ein Blockschaltbild eines Ausführungsbeispiels der Steuer- und Regeleinrichtung als integrierte Schaltung,

Fig. 4

ein Prinzipschaltbild eines Eingangskreises mit zwei Meßwerterfassungen,

Fig. 5

ein Ausführungsbeispiel der transformatorgekoppelten Wendelbeheizung einer Leuchtstofflampe mit drei Meßfühlern,

Fig. 6

ein Ausführungsbeispiel eines Ausgangskreises mit einem Symmetrierelement für zwei Leuchtstofflampen,

Fig. 7

ein Prinzipschaltbild des Wechselspannungsgenerators mit ihn ansteuernder Treiberschaltung,

Fig. 8a-c

jeweils ein Blockschaltbild der Sende- und Empfangseinrichtung mit verschieden ausgestalteten Koppelschaltungen zur Busleitung,

Fig. 9

ein Helligkeits- Zeitdiagramm zur Erläuterung des Abschalt- und des Notbeleuchtungsbetriebes,

Fig. 10

ein Helligkeits-Zeitdiagramm zur Erläuterung der Softstart- bzw. Softstopfunktion bei einer Systemkonfiguration gemäß Fig. 2.

Show it:

Fig. 1

2 shows a block diagram of an electronic ballast according to the present invention,

Fig. 2

1 shows a block diagram of a system concept in which several decentralized ECGs are connected to a central control device via a bus line,

Fig. 3

2 shows a block diagram of an exemplary embodiment of the control and regulating device as an integrated circuit,

Fig. 4

a basic circuit diagram of an input circuit with two measured value acquisitions,

Fig. 5

an embodiment of the transformer-coupled filament heating of a fluorescent lamp with three sensors,

Fig. 6

an embodiment of an output circuit with a symmetrizing element for two fluorescent lamps,

Fig. 7

2 shows a basic circuit diagram of the AC voltage generator with the driver circuit controlling it,

8a-c

in each case a block diagram of the transmitting and receiving device with differently configured coupling circuits for the bus line,

Fig. 9

a brightness-time diagram to explain the shutdown and emergency lighting operation,

Fig. 10

2 shows a brightness-time diagram to explain the soft start or soft stop function in a system configuration according to FIG. 2.

1 shows a block diagram of an exemplary embodiment of an electronic ballast according to the invention. The mains voltage U _N is supplied to the input circuit 20 (rectifier circuit), possibly via a switch S1. This generates the intermediate circuit voltage U ₀ , U _dc , which is fed to the alternating voltage generator 30 (inverter). The AC voltage generator 30 outputs its high-frequency output voltage U _HF to an output load circuit 40 which contains one or more fluorescent lamps LA1, LA2. A plurality of system measured values (process variables) can be taken from both the AC voltage generator 30 and the load circuit 40. Together, the measured values are fed to a control and regulating circuit 17, which in turn generates the digital control signals for the inverter 30. These are potential-shifted via a driver circuit 31 and fed to the output MOS-FETs of the inverter. The control and regulating device 17 is also assigned a transmitting and receiving device 10, which is connected via a bus line 12 to other electronic ballasts and / or to a central control device 50.

The latter is shown in Fig. 2 . There, a plurality of electronic ballasts 60-1, 60-2, 60-3, ..., 60-i are connected to a common bus line 12. All ECGs are connected via this bus line to the central control device 50, to which a display unit 51 is assigned. Via bus line 12, it is now possible to control one or more of the aforementioned ECGs and to transmit commands to them, such as switching off, switching on, igniting or the like. Brightness values can also be preset and, in return, error information can be queried from the individual devices. The control unit 50 is thus informed of the overall system status at all times, which means that a high degree of operational reliability can be guaranteed and accelerated maintenance of the decentralized ECGs or for their fluorescent lamps is possible.

The functional blocks 20, 30, 40, 10, 17 shown in Fig. 1 are described with reference to the following Figures now explained in more detail.

3 shows the control and regulating device 17 as an integrated circuit. The plurality of measured values m which correspond to the process signals of FIG. 1 are fed to it. It emits two digital control signals for the output stage transistors of the inverter 30, which are amplified and potential-shifted via a driver circuit 31.

In addition to the m measured values, the control and regulating device 17 also receives n target values fed. These influence the predeterminable control behavior. Furthermore is as part of the control and regulating circuit 17 or separately a transmission and Receiving device 10 provided directly or by means of a coupling circuit is connected to the bus line 12. It forms the serial interface that it Control and regulating device enables error and operating status information to be transmitted to the central control unit 50.

The aforementioned n target values can also be transmitted and received by this transmitting and receiving device 10 are fed to the control circuit after appropriate preparation 17 passes on. Setpoints can be, for example, the emergency lighting level (NOT), the minimum brightness level (MIN) and the maximum brightness level (MAX), within the latter two the predefined brightness level (DIMM) in the Moving operations.

Serial and digital are used as command and data words as well as error information words Data words are used, the length of which is 8 bits. Other value lengths are possible. Each decentralized ECGs are assigned an address that enables individual ECGs to be to address the address of the transmitting and receiving device 10 and information to query them or give them orders. The bidirectional way of working the bus line 12 enables problem-free and low-effort cabling Large number of decentralized ECGs with a central control unit (50).

FIG. 4 shows a basic circuit diagram of an input circuit as can be used for supplying the alternating voltage generator 30 from a supply network with the voltage U _N. The input circuit consists of capacitive input filters and possibly a harmonic choke. The Y-circuit capacitors are used for radio interference suppression. A surge arrester or a VDR is connected in parallel. This is followed by a full-wave rectifier, which can be omitted if the device is operated with direct voltage. Downstream of the rectifier is an intermediate circuit capacitor C4, which charges up to approx. 300 V with a residual ripple of approx. 10% at 220 V mains voltage.

Due to a crest factor to be kept low, the intermediate circuit voltage U _{0 should} be smoothed well.

A voltage divider R18, R28 is connected to the intermediate circuit capacitor C4 a measurement signal proportional to the intermediate circuit voltage can be tapped. On one Low pass R21, C25 a signal proportional to the supply voltage is detected and just like the DC link voltage-dependent measurement signal of the control and Control device 17 supplied. Both measurement signals are used for supply voltage monitoring and thus the operational security of the TOE.

5 shows an exemplary embodiment of a load circuit 40 according to the invention with a heat exchanger L5 for preheating the filaments of the fluorescent lamp LA1. In Fig. 5 only one of a pair of lamp circles is shown. The exemplary embodiment of the invention has a pair of these branches, that is to say two fluorescent lamps LA1, LA2 at an AC voltage output which emits the high-frequency AC voltage U _HF between the series-connected power switching transistors V21 and V28. The AC voltage generator is supplied with an intermediate circuit voltage U _dc from the input circuit 20 shown in FIG. 4. Since the fluorescent lamps have a negative internal resistance during operation, they must be supplied with high voltage peaks during the ignition process (ZÜND) and with appropriate heating energy when heating the filaments. Starting from the output connection of the inverter 30, a series resonance circuit L2, C15 leads via a balancing element TR1, which will be explained later, to the discharge path H2, H4 of the fluorescent lamp. Furthermore, a measuring resistor R32 is connected in series with the fluorescent tube, at which a voltage proportional to the lamp current I _L1 is tapped and fed to the control and regulating circuit 17. An ignition capacitor C17 is connected to ground (ZERO) between coil L2 and capacitor C15. With the aid of this arrangement, the dimmer characteristic of the discharge lamp can be made more uniform, since with increasing frequency the resistance of the capacitor C 15 decreases and the resistance of the discharge lamp increases. Parallel to the ignition capacitor C17 there is also the primary winding of the heat exchanger L5 and, in series with this, a Zener diode V15 and a measuring resistor R10. A voltage proportional to the heating coil current I _W1 is tapped from the latter and fed to the control and regulating circuit 17 as a further system measurement variable. Since the inverter 30 impresses an output voltage and the heat exchanger is essentially parallel to the fluorescent lamp LA1, a voltage is impressed on its secondary windings via the heat exchanger. The two secondary windings each supply one of the two heating coils H1, H2 and H3, H4 potential-free. The sum of the heating coil currents I _W1 is thus measured at the primary-side measuring resistor R10.

The Zener diode V 15, which is still connected in series, generates a DC component in the primary winding of L5, which, however, is not transmitted, but is missing in the lamp current I _L1 and thus the discharge of the lamp with an additional DC component in the order of magnitude of approx. 1% of the actual discharge current provided. This prevents the effect of the "running layers" that occur when the lamps are dimmed. The "running layers" consist in particular of light / dark zones which occur during dimming and run along the tube at a predetermined speed. A superimposition of low direct current accelerates this running effect in such a way that it no longer has a disturbing effect.

For heating, the inverter 30 is operated at a high frequency f _max , so that an AC voltage occurs at C17 which is not suitable for igniting the lamp LA1. In this operating state, the filaments of the lamp are heated via L5, the lamp absorbing a high and then a lower heating current due to the thermistor effect of the filaments. After a preheating time of approx. 750 ms, the ignition (IGNITION) of the lamp is initiated.

When the fluorescent lamp is ignited, the frequency f of the inverter 30 reduced so that it is closer to the resonant frequency f of the output series resonant circuit L2, C15 is approaching. This creates a C17 Voltage surge that is on the order of approximately 750 V (peak). This will ignite a functional lamp.

As soon as the lamp LA1 or LA2 has ignited, the series resonance circuit L2, C15 or L3, C16 is strongly damped. On the one hand, this causes a shift in the resonance frequencies f ₀ and, on the other hand, an immediate drop in the AC voltage applied to the respective lamp. The decrease is detected by the control and regulating circuit 17 via the voltage divider R27, R25 connected in parallel to the lamp. This then initiates the actual operating phase (DIMM) of the lamps.

For effective lamp operation, the frequency f of the inverter 30 is regulated so that the lamp output corresponds to the predetermined target value, ie the desired brightness level. The higher the frequency in the operating state, the lower the lamp brightness. The operating frequency of the alternating voltage generator 30 can also be shifted to values which are in the order of magnitude of the heating frequency or above. At a maximum power (MAX), an output frequency can also be set which is below the ignition frequency but still above the resonance frequency of the series resonance circuit L2, C15.
The operating state of the lamp circuit 14 can vary greatly depending on the lamp used, for example argon or krypton lamps, or depending on the lamp power selected.

The combination of the capacitor C24 and the diodes V30, V31 causes a frequency-dependent Damping the output circuit in the event of a voltage surge. It is in front important when high frequencies and high impedances occur, e.g. if there is no lamp or if the filament is already warm. The wiring This type helps the voltage surge when the lamp is not ignited or missing then limit if it is undesirable. C24 is selected so that the damping remains small enough at the time of ignition.

Fig. 6 shows the output circuit of Fig. 5 for the two-lamp - two fluorescent lamps on an inverter - operation. The symmetry transformer TR1 is also shown here in full. Each winding is traversed by one of the two lamp currents. This happens in opposite directions, so that in the event of a deviation in the current amplitude, a resulting magnetization occurs, which induces a voltage in the inductive element which has a symmetrical effect. Such a transformer is advantageous if the two lamps would burn differently bright in the dimmed state due to component tolerances and lamp tolerances as well as different temperature conditions. The symmetry element TR1 avoids this in the case of two-lamp luminaires. If several pairs of lamps are operated at an AC voltage output, such a balancing element TR1 must be provided for each pair.

From Fig. 6 it can also be seen that an individual series resonance circuit is connected upstream of each fluorescent lamp and that an individual ignition capacitor C17, C18 is connected in parallel. This enables a relatively independent ignition phase and synchronization in dimming mode. In parallel with the ignition capacitors C17, C18 there is a voltage divider R25-R28, which feed a signal proportional to the output AC voltage to the control and regulating device 17. In the same way, it is also possible to connect the voltage dividers directly parallel to the fluorescent lamp, ie behind the balancing element TR1. In series with the lamps, this was already explained for a lamp circuit with reference to FIG. 5, there is one current measuring shunt R31, R32 each. A signal which is proportional to the lamp current is obtained from them and can be multiplied in the control and regulating circuit 17 by the aforementioned lamp voltage signal. In this way it is ensured that at any time of the actual lamp power _is P or E brightness proportional signal is available, which can be preset to a precise brightness control as the feedback.

7 shows the inverter 30 in more detail with its output power transistors V28, V21. Between them, the high-frequency AC voltage U _{HF is} output to the load circuit 40 explained above. The two power transistors are controlled via a control circuit 31, which receives its control signals from the control and regulating circuit 17. Possibly. unbalanced turn-off / turn-on delays come into consideration for the respective transistors, so that a common conduction of both transistors V21, V28 can be avoided in principle. The upper transistor is supplied via a bootstrap circuit (not shown), the lower transistor and the system controller 10, 17, 31 receive their drive voltage via a series resistor and a smoothing capacitor C5 from the intermediate circuit voltage U ₀ . In addition to the aforementioned power supply from the intermediate circuit, there is also a low-loss AC voltage coupling from the oscillating inverter 30 via a coupling capacitor C21, the diodes V12, V7 and the inductance L7 into the storage capacitance C5.

The current that can be supplied to the smoothing capacitor C5 through the series resistor or a current source I _q is sufficient to supply the IC31 and the control and regulating circuit 17 in the switched-off mode (SLEEP).

When the inverter is in operation, the supply, coupled out via a capacitor C21, rectified via the named components V12, V7, L7 and smoothly coupled in via C5, is sufficient. This supply voltage generation is almost loss-free since only reactive elements are used to limit the current. A voltage signal U _Kap proportional to the branch current I _max is obtained by means of the anti-parallel diodes V14, V15 connected in the lower inverter half-branch of the transistor V21 and the resistor R34 connected in parallel. Like the other process signals, this is fed to the control and regulating circuit 17. From this, he can determine the current direction of the current flowing through the inverter at the moment before V21 is opened. If this current is negative, the load circuit 40 of the inverter 30 is in an impermissible capacitive range. It represents a danger to the controlling inverter. In addition to the pure amplitude detection, a phase angle analysis can also be used, in which the load current I _{L1 is set} in relation to the inverter branch current I _max and from this the relative phase of both currents Detection of the operating state is used.

The control circuit detects an inadmissible capacitive operating behavior 17 with an increase in the operating frequency f of the inverter 30 answered, with which the load circuit 40 is again operated inductively. The aforementioned capacitive mode of operation mainly occurs with a low supply voltage. With the Branch current detection can reliably avoid the destruction of components.

8 shows the transmitting and receiving device 10 and the coupling filter connected upstream of it, with which the bus coupling to the control line 12 takes place. In this example, the digital interface 10 is given the setpoints for minimum, maximum and emergency lighting brightness (U _NOT , U _MIN , U _MAX ). Furthermore, a digital input DAT is provided, via which both the control signals arrive from a central control device to the decentralized ECG and the error signals are transmitted from the decentralized ECG to the central control device. The serial interface enables remote control of the electronic ballast by means of a digital command signal or command word. An 8 bit data word is provided as such a digital signal. It is differentiated by the two capacitors C22, C23, then potential-shifted by half the supply voltage of the control circuit 17 or of the transmit and receive circuit 10 and then fed to the digital input DAT of the interface 10 via a damping capacitor C12. This means that both the 50 Hz mains frequency can be suppressed and the input currents of each interface can be kept low. 8b shows a further embodiment of the bus coupling. Here, the two bus lines 12 are inductively coupled to the data input of the digital interface. If ECGs are operated with the coupling filter shown in Fig. 8a on different phases of the three-phase network, compensating currents can flow that interfere with the data transmission. Although these compensating currents can also flow in the circuit according to FIG. 8b, they cancel each other out because there is no ground connection on the primary side. An advantageous further development of this circuit is shown in FIG. 8c. The circuit is protected against polarity reversal by using a secondary winding with center tap. Optical coupling can also be used, but this has an increased power consumption.

255 (corresponding to 8 bit) brightness values are provided as control signals. That too Control signal "OFF", represented by the binary word "zero" is possible. By the The aforementioned signal OFF, the entire ECG moves immediately or after a slight one Time period in a power-saving shutdown mode (SLEEP). In him the Measuring current consumption of the entire ballast minimal. The inverter 30 and the control circuit 31 are shut down and, if necessary, after a few more Time delay also the main components of the control and regulating circuit 17. Only the receiving circuit of the transmitting and receiving device 10 and the Monitoring circuit for the detection of an emergency operation (EMERGENCY) remain activated. The total circuit power drops below 1 W. However, it does in such a state a new control signal, the control circuit 17 immediately takes the Switch-on sequence before that with preheating and ignition process (IGNITION) in the stationary Operation transferred and there is an immediate adjustment of the desired Brightness value (DIMM).

In addition to controlling the brightness and the emergency lighting mode as well as the switch-off mode (SLEEP mode), the control and regulating circuit 17 also has the task of to take all the aforementioned process variables the information that for Monitoring and control of the TOE are important.

Versorgungsspannung U_ac, U_N,

Unter-/Überspannung U_Nmin, U_Nmax,

Batteriespannung U_B,

Zwischenkreisspannung U₀,U_dc,

Lampenstrom/Betriebsstrom I_L1,I_L2,

Lampenspannung U_L1, U_L2,

Ausgangsspannung U_HF,

Ausgangsstrom I_HF,

Wendelstrom I_W1, I_W2,

Wechselspannungsgenerator-Zweigstrom I_Kap.

These are voltage monitoring, emergency operation maintenance and monitoring of the fluorescent lamps with regard to filament breakage or gas defects. The various operating states of the fluorescent tube, such as ignition, preheating and stationary operation, can also be distinguished by the measured variables. The measured process variables and those used for checking are summarized below:

Supply voltage U _ac , U _N ,

_Undervoltage / overvoltage U _Nmin , U _Nmax ,

Battery voltage U _B ,

_{DC link voltage} U ₀ , U _dc ,

Lamp current / operating current I _L1 , I _L2 ,

Lamp voltage U _L1 , U _L2 ,

Output voltage U _HF ,

Output current I _HF ,

Spiral current I _W1 , I _W2 ,

AC generator branch current I _chap .

Based on the sizes listed, overvoltage and undervoltage in the DC link and recorded in the supply circuit. The control and regulating circuit 17 switches all functions if the voltage becomes too high and can only be restored The function goes once the voltage has been switched off and on again.

The occurrence of undervoltage - which leads to a dangerous capacitive operation of the inverter leads - is answered by the fact that the control circuit 31st is blocked. As long as the mains supply does not have the necessary voltage to the Guaranteed heating process of the coils and avoiding capacitive operation the control and regulating device 17 does not ignite. Only after exceeding The ignition process is triggered at a predefinable threshold value. This happens automatically.

An emergency mode switchover to a predeterminable emergency lighting brightness takes place, for example, when a DC voltage U _{N is} detected by the control circuit 17 via the usual AC supply input of the switch-on circuit 20 and via the sensors R21, C25 (FIG. 4). A counter logic is used for this purpose, which initiates emergency operation if the specified threshold value is not exceeded or not reached. This can happen after a specified dead time that bridges individual, possibly missing, half-waves.

If the normally feeding AC voltage U _ac , U _N fails in a lighting system, an emergency voltage supply U _B , which is obtained from batteries or a generator, is placed on the mains voltage line. The ECGs recognize this automatically.

In emergency mode, the brightness of the fluorescent lamps is no longer specified by the digitally specified brightness value DIMM, but by a trim value that can be specified locally on the device and can be specified via the input U _NOT . If the ECG is in switch-off mode (SLEEP) when this emergency operation occurs, ie the lamp and inverter are switched off, it will first carry out the normal ignition process (IGNIT) in order to subsequently switch to the emergency operating brightness.

When the end of the emergency operating state is recognized, the ECG returns to the previous state back, this can be the OFF state if the TOE was previously there. This However, it can also be the original brightness value (DIMM), if this is required of the emergency operation.

The detection of the filament current detects whether either a lamp is not inserted or one of the two filaments is broken. In one of these error cases, the inverter 30 is operated at its maximum frequency f _max , which on the one hand results in the heating current still flowing when the defective lamp has been replaced and on the other hand reduces the voltage on the defective lamp to the smallest possible extent , This is important to comply with the safety regulations according to VDE. The inductive part of the series resonance circuit in the output becomes so high at the above-mentioned high frequency f _max with respect to the capacitive resistance of the ignition capacitor C17 that the voltage at the output is limited to harmless values and there is no danger for the maintenance personnel.

If a functional lamp is inserted, no further action is taken after waiting the preheating duration of the ignition process (IGNITION) initiated.

The internal sequence control in the control and regulating circuit 17 also continues to limit the number of start attempts to two and sets (sends) whenever one There is an error if e.g. B. the lamp is missing if a filament break or a There is a gas defect, an error signal via the transmitting and receiving device 10 the bidirectional bus 12. This also applies in emergency mode because the lamp is defective emergency operation cannot be maintained.

Wiring errors that lead to a short circuit in the discharge path of the lamp can be detected on the basis of the process signals when the lamp voltages be monitored for a predetermined minimum value. One leads Falling below this specified value, as in the case of mains overvoltage monitoring to switch off the entire ECG.

The unwillingness to ignite the lamp, e.g. B. by gas defect, is from the control and Control circuit 17 detected. If the lamp is within a predetermined ignition timing cannot be ignited, d. H. when there is a drop in voltage across the ignition capacitor C17 does not occur within this period, the lock mentioned applies on.

In addition to a complete shutdown and an error message, a repeat time can also be waited for after which a new attempt to start and start is made. If no ignition success is achieved here either, the control and regulating circuit 17 reacts as in the case of a broken heating coil and sets the frequency of the inverter 30 to the maximum value f _max .

When replacing the lamp, what the control and regulating circuit 17 on one Rise in the lamp voltage or a change in the heating coil current detects, a new attempt is made to insert a new lamp.

The following is explained for the brightness control of the fluorescent lamps. A real brightness control is used, since this guarantees the same lamp outputs regardless of the lamp type - with essentially the same lamp efficiency. The measured values determining the actual value, lamp current and lamp voltage, are multiplied and compared in analog or digital form with the setpoints predetermined by remote control via the transmitting and receiving device 10. The comparison result controls the frequency f of the alternating voltage generator 30 directly or via a controller. If a more precise gradation of brightness is desired, a logarithmic setpoint adjustment can take place. Exponential actual value weighting can be carried out in the same way. In addition to the independence of the lamp type, compensation is also achieved for lamp age, the existing operating temperature and also the possibly fluctuating mains voltage U _N.

With the process signal-controlled operating state monitoring, it is also possible to ignite the lamps to small brightness values, whereby the normally occurring light pulse can be avoided. The latter is due to the energy stored in the output circuit by the ignition process, which is then suddenly discharged into the lamp after ignition. For suppression or elimination, a quick ignition detection - by changing the lamp lamp voltage U _L1 , U _L2 - is provided, as well as a quick reduction of the lamp current after ignition. The latter by instantly shifting the inverter output frequency towards higher frequencies. As a result, the glow area between the ignition and the stationary gas discharge is artificially extended. This would result in a reduction in lamp life under normal circumstances. This is according to the embodiment avoided, however, since the extension of the glow phase is used only for the critical low brightness values. For large brightness values, the current is kept at a higher level, which shortens the glow phase. This can be set via digital control words and the transmitting and receiving device 10 via software.

FIG. 9 shows a brightness-time diagram in which the brightness of the lamp controlled by the electronic ballast according to FIG. 1 is varied as a function of time. First, maximum brightness is provided, followed by a switch-off cycle specified via the bus line 12 and the digital interface 10. The brightness is acc. a predetermined slope reduced to zero, then the inverter 30, its driver circuit 31 and essential parts of the control IC 17 turn off to save electricity. A subsequent emergency lighting state leads - despite the system being switched off - to controlled ignition and a build-up of the brightness of the lamp to the preset emergency lighting brightness (EMERGENCY). This can be changed via the setpoint specification U _NOT for each decentralized ECG. Likewise, the maximum and minimum brightness value (MIN, MAX) shown in FIG. 9 can be set or adjusted via a corresponding setpoint value.

10 shows a program-controlled "soft start" as a brightness-time diagram shown schematically. The ECG 60 is initially in the switched-off state (OUT). The "Softstart" command now either leads to an automatic one slope-controlled increase in lamp brightness - after ignition - or closed a program-controlled incremental increase in lamp brightness levels. in the the latter case are determined by the central control device 50 Periods of incrementally increasing brightness values are sent. The decentralized ECGs follow the requirements almost instantaneously. This will make a rate of change-controlled (regulated) rise and fall of the decentralized light sources possible.

Claims (2)

1. Method for the control of the brightness and the operating behaviour of gas discharge lamps via an electronic ballast (EVG), wherein the electronic ballast has:

   an a.c. voltage generator (30) which can be varied in its output frequency (f),

   a rectifier circuit (20), fed from a supply a.c. voltage (U_N, U_ac), which feeds the a. c. voltage generator (30),

   a load circuit (40), which has at least one series oscillation circuit (L3, C18, L2, C17) having at least one gas discharge lamp (LA1, LA2), and which is fed from the a.c. voltage generator (30) with an a.c. voltage (U_HF) which can be varied,

   a control and/or regulation device (17), wherein there are delivered to the control and/or regulation device (17) commands for the control and/or regulation of the brightness and the operating condition of the at least one gas discharge lamp (LA1, LA2),

   wherein upon receipt of a switch-off command corresponding to a SLEEP operating condition, the at least one gas discharge lamp (LA1, LA2) is switched off and the a.c. voltage generator halted after a predetermined period of time,
   characterised in that,
   also in the switch-off mode the electronic ballast recognises with the aid of a measurement sensor (R21, C25) a failure of the supply a.c. voltage (U_ac) and the switching of an emergency d.c. voltage (U_b), obtained from batteries or from a generator, onto the line of the supply a.c. voltage, and thereupon carries out the normal ignition procedure and sets the at least one gas discharge lamp (LA1, LA2), to an emergency operation brightness which can be preset at the ballast by means of a trimming value.
2. Circuit arrangement for the control of the brightness and the operating behaviour of the gas discharge lamp via an electronic ballast (EVG),
      wherein the electronic ballast has:

   an a.c. voltage generator (30) which can be varied in its output frequency (f),

   a rectifier circuit (20), fed from a supply a.c. voltage (U_N, U_ac), which feeds the a.c. voltage generator (30),

   a load circuit (40), which has at least one series oscillation circuit (L3, C18, L2, C17) having at least one gas discharge lamp (LA1, LA2), and which is fed from the a.c. voltage generator (30) with an a.c. voltage (U_HF) which can be varied,

   a control and/or regulation device (17), wherein there can be delivered to the control and/or regulation device (17) digital commands for the control and/or regulation of the brightness and the operating condition of the at least one gas discharge lamp (LA1, LA2),

   a driver circuit (31) via which, upon receipt of a switch-off command corresponding to a SLEEP operating condition, in which the at least one gas discharge lamp (LA1, LA2) is switched off, halts the a.c. voltage generator after a predetermined period of time;

   characterised in that,
   the electronic ballast has further a measurement sensor (R21, C25) which upon a failure of the supply a.c. voltage (U_ac) and the switching of an emergency d.c. voltage (U_E), obtained from batteries or from a generator, onto the mains voltage line, delivers a voltage to the control and/or regulation device (17) which also during a switch-off mode recognises a d.c. voltage and thereupon carries out the normal ignition procedure and sets the at least one gas discharge lamp (LA1, LA2) to an emergency operating brightness which can be predetermined at the ballast by means of a trimming value.

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