EP1601237A2 - Ballast with control circuit for the permanent operation of a discharge lamp - Google Patents

Abstract

The circuit can act as a starter for two gas discharge lamps (LA1,LA2). The terminals of the lamp electrodes (KL2-1 to KL2-4) are connected to two transformers (TR1,TR2) with a PTC resistor (R1) connected between them. The supply voltage (L,N) is connected to terminals (KL1-1,KL1-2) of a filter with two capacitors (C1,C2) and two coupled coils (FI1). There are connections via diodes (D1-D6) and capacitors (C8,C10) to first (V1) and second (V2) differential transistors. The circuit includes a choke (LD1) for controlling the lamp current. Preheating time may be controlled during starting of the lamps.

Description

Technical area

The present invention relates to a ballast for discharge lamps, specifically, such discharge lamps, the preheatable electrodes exhibit

State of the art

Such ballasts are known per se. Often they have half-bridge inverter circuits on. However, the invention also relates on other ballasts. Basically generates an inverter circuit from a rectified AC power supply or a DC power supply a power supply for the lamp, the has a higher frequency than the mains frequency. In many cases it is included a control circuit for controlling the lamp current or the lamp power provided in Lampendauerbetrieb, hereinafter referred to as continuous operation control circuit referred to as. This continuous operation control circuit influences the operating frequency at which the inverter uses the Lamp supplies, and regulates about the lamp current or the lamp power. This is done by approximating or removing the operating frequency resonant frequencies of the lamp resonant circuits containing the lamp.

Before the lamp can be operated, it must go through a relatively high Voltage to be ignited. Again, this is in many cases a resonant stimulus the lamp resonant circuit use. For discharge lamps with preheatable electrodes, the electrodes are first for a preheated certain time before the actual ignition voltage applied becomes. The preheating time is determined by a preheating time, in the In the most general sense, a physical process takes place that is a temporal one Delay defined, and must run back after the preheat time, to run again at a later turn on the lamp again to be able to. The preheating timer has the function of a switch. The Details of the realization of such a preheating timer and the physical Operations are not relevant to the principle of the invention, therefore the above general formulations are chosen.

The ignition of the lamp takes place in such cases, regardless of the continuous operation control circuit after expiration of the mentioned physical process. For this purpose, the ignition voltage must be achieved in some way, for example, by a resonance excitation in the lamp resonant circuit. It would disturb the influence of the continuous operation control circuit.

Presentation of the invention

The invention has the technical problem as a basis, an improved Ballast and an improved method of operation of discharge lamps specify with preheatable electrodes with a continuous operation control circuit.

It refers to an electronic ballast for at least one Discharge lamp with preheatable electrodes, which has ballast a continuous operation control circuit for controlling the lamp current or the lamp power in Lampendauerbetrieb over the operating frequency the lamp, a preheating timer defining a preheating time for the electrodes, which is adapted to the preheating by a with a temporal Define delays running physical process and this Process afterwards with a time lag, wherein the ballast is adapted to the lamp then independently from the continuous operation control circuit to ignite when the physical Operation of the preheating timer has expired, characterized that the ballast is further adapted to the continuous operation control circuit then put out of action for lamp standby, if the preheater after a service interruption of the lamp due an unfinished return of its physical process can not define a complete new preheat process, so that the lamp then ignited independently of the continuous operation control circuit can be.

The invention is further directed to a corresponding method of operation.

Preferred embodiments of the invention are defined in the dependent claims specified.

The inventor has found that the starting point of the invention is that Problems arise with the time delays of the preheating timer can. As a rule, the preheating time defining physical run Operations also with a certain time delay again back.

This applies, for example, for the here also preferred case during the Preheating time by ohmic heat loss heated PTC resistor as Vorheizzeitglied, wherein the PTC resistor thereby its electrical resistance increased as a result of increasing temperature. An important and Here preferred mechanism is one with increasing PTC resistance decreasing attenuation of the lamp resonant circuit and Ignition as a result of a resonance stimulation in it. If now the PTC resistor is warmed up, it then cools down slowly. It is In addition, even with a permanent warming of the PTC resistor during Lampendauerbetriebes to count, because constantly small currents flow through it. The cooling process therefore begins only after switching off the lamp. He takes in the used for electronic ballasts PTC resistors typically several tens of seconds to a few Minutes and is thus much slower than the typical cooling time of the electrodes of about a few 100 ms. Will the discharge lamp So after a relatively short time turned on again, so is the PTC resistor not sufficiently cooled or, more generally, the physical Operation of preheating timer has not sufficiently run back. In such cases, malfunctions may occur due to the apparent sequence of preheating the continuous operation control circuit in Function comes or stays. This disturbs or prevents a rule Re-ignition of the lamp.

The above description would apply mutatis mutandis to the case that the physical operation of the Vorheizzeitgliedes during lamp endurance operation already running back, so has run back after a long operation. For then situations are still possible in which the lamp only is turned on briefly, immediately turned off again and then relatively is quickly turned back on. For example, this can be done during reinstallation a lamp, luminaire or lighting system happen at the functionality should be "repeatedly tested". The operators know in such cases the background of the failure of one Restarts i. d. R. and do not hold the lamp or light for broken.

Therefore, the invention proposes, in the event of not yet sufficient returned physical process in the preheat timer, the continuous operation control circuit to turn off to re-ignition regardless of the continuous operation control circuit.

Preferably, this is done by the lamp voltage, one of them derived potential or another variable correlating therewith to one Input of a control amplifier or switching transistor of the continuous operation control circuit is created. Of course it can be enough, just one temporal portion of the continuous operation control circuit or the correlating Size to use. Reference is made to the embodiments.

It has already been stated above that a PTC resistor is a common and is the preferred preheat timer here. In principle, but also come Other Vorheizzeitglieder into consideration, in particular on timers, such as RC elements, switches to be controlled.

In the case of a PTC resistor, the invention further provides that in series with the PTC resistor, preferably a threshold device such as a so-called TISP or SIDAC, ie a threshold value component, that does not conduct electricity below a certain voltage threshold. This results in the already discussed possibility that the PTC resistor, which is usually parallel to the lamp, in continuous operation no electricity, but only in the preheating and ignition phases, while which are subject to higher voltages.

I. d. R. must be a lamp current measurement for the continuous operation control circuit be provided, either because the lamp current regulated itself or from the lamp current, the lamp power is determined. The invention proposes here various preferred variants. For one thing, the Lamp current to a serial one of the lamp electrodes with one of the Supply branches of the ballast connecting coupling capacitor measured become. The term "coupling capacitor" are commonly used Capacitors referred to in series with the lamp or lamps switched and prevent steady state DC current through the lamp (s).

In this case, preferably with at least one diode pair a branch provided in which only during a half-wave is measured and thus during the other half wave no energy is consumed. This is one Current measuring resistor in series with one of the diodes. It is based on the embodiments directed.

A likewise favorable, however somewhat more complex solution lies in one Measuring transformer. In particular, a differential current transformer is preferred here. with a correction of the total lamp current to the preheating or through the electrodes and, for example, the PTC resistor also occur during continuous operation flowing stream can. Thus, as the lamp current only the actually by the discharge in the current flowing through the lamp.

A further preferred embodiment of the invention provides a voltage regulation circuit , which serves the ignition voltage of the lamp resonant circuit on the frequency of the half-bridge or another converter of the Ballast. This voltage regulation circuit is advantageous because at an ignition via a resonant excitation as a result of the required Quality of the lamp resonant circuit a relatively accurate frequency setting is required. The control circuit can now change the frequency to the resonance behavior adapt the lamp resonant circuit or "nachfahren" and in particular via a limitation of the ignition voltage by frequency change work.

The aforementioned continuous operation control circuit may be connected to the voltage regulation circuit be combined so far, as both on the same control input for controlling the operating frequency of the converter. there may be preferably provided that the circuit as current or Power control circuit (ie continuous operation control circuit) works, as soon as appreciable lamp currents flow, the lamp has ignited, and in the other case, the voltage control has priority. The already mentioned Consideration of the preheating current or PTC resistance current in the lamp current measurement is important here. It is, however possible, a realistic lamp current measurement without differential transformer perform, for example, by the current control by a voltage measurement via the PTC resistor (or via a measuring resistor parallel or serial to the PTC resistor) during the preheat phase is blocked.

In some cases, ballasts are designed to be a plurality To operate lamps. If these are connected in series, they result in the above, no significant additions, such as corresponding embodiment shows. If they are connected in parallel, is It makes particular sense, the corresponding lamp voltages or so correlating quantities in the sense of an exclusive-or link to the Input of the control amplifier or switching transistor in the continuous operation control circuit to lay.

Brief description of the drawings

Figur 1

zeigt ein Schaltdiagramm zu einem ersten erfindungsgemäßen Ausführungsbeispiel.

Figur 2

zeigt ein Schaltdiagramm zu einem zweiten erfindungsgemäßen Ausführungsbeispiel.

Figur 3

zeigt ein Schaltdiagramm zu einem dritten erfindungsgemäßen Ausführungsbeispiel.

The invention will be explained in more detail below with reference to three exemplary embodiments. The individual features disclosed may also be essential to the invention in other combinations. The above and following description refers to the device category and the method category of the invention, without explicitly mentioning it in detail.

FIG. 1

shows a circuit diagram of a first embodiment of the invention.

FIG. 2

shows a circuit diagram of a second embodiment of the invention.

FIG. 3

shows a circuit diagram of a third embodiment of the invention.

Preferred embodiment of the invention

FIG. 1 shows a first exemplary embodiment. On the left are two connections KL1-1 and KL1-2 are marked on which a mains voltage is connected shall be. A filter of two capacitors C1 and C2 and two with F11 designated coupled coils connects the mains voltage terminals with a full-bridge rectifier from the diodes D1 - D4. The rectified supply voltage is about to two pump branches to computing diodes D5-D8 to an intermediate circuit storage capacitor C6 placed in the figure on the far right.

To comply with relevant regulations regarding mains current harmonics, For example, IEC 1000-3-2, so-called pump circuits are also used. which prepare a comparatively small circuit complexity. In principle, the rectifier is thereby via an electronic Pump switch with the main energy storage, the DC link capacitor C6, coupled. The between the diodes D5 and D7 on the one hand and D6 and D8, on the other hand, are pumping via a pump network coupled to the output of an inverter explained in more detail. Thereby is during the half-period of the inverter frequency over the Pump node energy taken from the mains voltage and in one Pump network cached. In the following half-period is the cached energy via the electronic pump switch, here the diodes D8 and D7, the intermediate circuit storage capacitor C6 fed. This is in time with the inverter frequency energy from the Taken from the net. The mentioned filter elements suppress the corresponding ones Spectral components, so that ultimately a quasi-sinusoidal power consumption he follows.

The details of the pumping circuit are not for the present invention relevant. Here is the state of the art and in particular the applications DE 103 03 276.2 and DE 103 03 277.0 of the same Applicant directed.

The DC link capacitor C6 feeds this as a half bridge of two Switching transistors V1 and V2 constructed converter. The half-bridge transistors V1 and V2 generate by corresponding antiphase clocking their center tap an alternating potential that between the two potentials of the rectifier output oscillates. This alternating potential is over a lamp inductor LD1 and, in this case, a series circuit two discharge lamps LA1 and LA2 and one in the following even closer explained differential transformer TR2 via two coupling capacitors C15, C16 connected to the utility berths.

FIG. 1 shows that not only a current through the discharge plasma in FIG can flow the lamps LA1 and LA2, but also a Vorheizstrom through the upper electrode of the upper lamp LA1 and a winding of a Heating transformer TR1 and a PTC resistor R1 and the lower electrode the lower lamp LA2 can flow. The preheating current for the upper Electrode of the lower lamp LA2 and the lower electrode of the upper Lamp LA1 is generated via the heating transformer TR1. One recognizes in 1 that the differential current transformer TR2 in its lowest in Figure 1 Winding ultimately the difference of the total lamp current through the uppermost winding of the differential transformer TR2 and the preheating current determined by the mean winding. In the case of only a single discharge lamp would the heating transformer TR1 with its circuit eliminated by the internal electrodes.

The preheating results during the preheating u. a. by the value of the PTC resistor R1. During the preheat phase, the value of R1 initially so small that a given by the lamp data current is reached. After the preheat phase, the value of R1 increases, so that finally a negligible compared to the actual discharge current Heating current flows.

The described arrangement for preheating causes during the preheating phase a strong attenuation of a lamp resonant circuit described below and thus a reduction in the natural frequency significantly below the resonant frequency of the undamped lamp resonant circuit. While the preheat phase is operated with an inverter frequency, the below the resonant frequency of the undamped lamp resonant circuit thus ensuring high heating currents and a short preheating phase.

The lamp resonant circuit has, in addition to the already mentioned lamp inductor LD1 resonant capacitors C5 and C9. The determination of the resonance frequency results from an effective capacity of C9 or the series connection from C5 and C9.

If the described lamp resonant circuit after the preheat phase due the attenuation decreasing due to the high resistance of R1 and the correspondingly increased quality near its resonance frequency stimulated, a high ignition voltage is produced across the lamps LA1 and LA2, to ignite the discharge lamps using the preheated electrodes leads. After ignition, the lamp resonant circuit acts as a matching network, that the output impedance of the inverter in a to Operation of the discharge lamps transforms appropriate impedance.

Incidentally, the lamp resonant circuit also acts as a pump network. Is this Potential at the already mentioned pump node lower than the current one Mains voltage, the pumping network draws energy from the grid. in the reversed case, the absorbed energy to the DC link capacitor C6 delivered. Another pumping action goes from the condenser C8 off. The capacitor C8 continues to act as a so-called trapezoidal capacitor for switching discharge of the half-bridge transistors V1 and V2. The Pump network for the second pump branch consists of a series circuit a pumping inductor L1 and a pumping capacitor C10.

The half-bridge transistors V1 and V2, which are designed as MOSFET, be at their gates through an integrated circuit, for example of the type International Rectifier IR2153. This control circuit also contains a highside driver to control the "high-level" Half-bridge transistor V1. In this context, the diode D9 and the capacitor C4 provided.

Except the driver circuits for the half-bridge transistors V1 and V2 the control circuit contains only one oscillator whose frequency over the connections 2 and 3 (RT and CT) can be set. This frequency corresponds to the operating frequency of the half-bridge. Between the connections 2 and 3, a frequency-determining resistor R12 is connected. Between port 3 and the lower potential serving as the reference potential Supply branch is a frequency-determining capacitor C12 and serial to the emitter-collector path of a bipolar transistor T3 connected. Parallel to the emitter-collector path, a diode D15 is connected to C12 load and unload. By a tension between the Base terminal of the bipolar transistor T3 and the reference potential, the Half-bridge frequency can be adjusted and thus forms a manipulated variable for a control loop. The base terminal of the bipolar transistor T3 is continued from controlled on the right in Figure 1 circuit parts. The bipolar transistor and the control circuit and associated circuitry thus form a regulator.

The functions of the control circuit and the associated circuitry can also by any voltage or current controlled oscillator circuit can be realized, the drive via driver circuits accomplish of converter transistors.

In the exemplary embodiment, the controller detects the lamp current as a controlled variable, and more specifically, the discharge current. This one will be at the lowest winding of the already mentioned differential transformer TR2 detected. A full-bridge rectifier GL1 rectifies and conducts the current him over a low-impedance measuring resistor R21 to the reference potential. Via a low pass of the resistors R22 and R32 and the capacitor C21, which is used for averaging, becomes the voltage drop at R21 in the input of a non-inverting measuring amplifier in the form of a Operational amplifier U2-A given. This is in a known manner the resistors R23-R25 connected and outputs its output signal the diode D23 to the already described controller input (manipulated variable node). Thus, the current control loop is closed, previously as a continuous-operation control circuit was designated. The diode D23 decouples the output of the measuring amplifier U2-A from the voltage divider D24, C20, R20, D16, R11 when the potential at the connection point LD1-D21 is high enough. According to the circuit arrangement is designed so that without Discharge current the potential at the anode of diode D23 the starting value accepts. This is below a minimum value that defines the work area of the transistor T3 and thus the controller limited. potential fluctuations thus have no effect on the half-bridge frequency, as long as the potential remains below the minimum value. The control loop is not closed. The starting value causes a half-bridge frequency, that of the starting frequency equivalent. Via C12 and R12, a relatively low frequency is selected, which ensures high heating currents and short preheating phases.

Since the subsequent to the preheating ignition phase for the half-bridge switch V1 and V2 and the lamp resonant circuit (LD1, C5, C9) one high load, here is a protection circuit to avoid provided high ignition voltages. This protection circuit forms simultaneously but also a voltage regulation circuit for setting the ignition voltage to a suitable value. This is done by a varistor D24 on the lamp side Connection of lamp inductor LD1. Instead of a metal oxide varistor could also be a suppressor diode or zener diode used here. So it's about a threshold. Via a series connection with a capacitor C20 and a resistor R20 becomes the lamp voltage given at a certain threshold between two diodes D16. The anode of the left diode represents a second regulator input Value of the resistor R20 influences the strength of the effect of the below described intervention on the control loop.

The tapped via the varistor D24 lamp voltage forms a measure of the reactive energy oscillating in the lamp resonant circuit and for the ignition voltage. If this voltage exceeds the threshold value of the varistor D24, so the half-bridge frequency is increased and thus in the resonant circuit oscillating reactive energy reduces and on the other hand the lamp voltage reduced.

A typical value for the threshold value of the varistor D24 is z. B. 250 V The voltage regulation circuit then regulates above this voltage.

After ignition, a lamp current flows, the potential at the anode the diode D23 raises to a value in the working range of the bipolar transistor T3 is and thus the control loop of the continuous operation control circuit (for the lamp current) closes.

On the other hand, in the case of one above the threshold value of the varistor D24 lying lamp voltage via the right diode D16, the one tap between the resistors R22 and R32 at the positive input of the control amplifier U2-A drives, raised the potential at this input. Thus, the continuous operation control circuit according to the invention out of operation be set if the already described situation of a new Ignition test without cooled PTC resistor R1 occurs.

In such a case, because of the lack of preheating, only an "abnormal" Set the glow discharge in the discharge lamps LA1 and LA2, occur at the relatively high lamp voltages. This abnormal glow discharge However, generates a significant discharge current over the differential current transformer TR2 is measured and the continuous operation control circuit brings to function. However, this would now on the half-bridge frequency Influence and thus ultimately a reignition of the Disturb lamp by removing it from resonance frequency.

By applying a (negative) portion of the high lamp voltage via the components D24, C20, R20, D16 to the non-inverting input However, the control amplifier U2-A is the continuous operation control circuit blocked, so that the already described voltage regulation circuit in Function remains. This sets a suitable ignition voltage, so that the Ignite the lamp despite a lack of regular preheat operation can. Such an ignition process is exhausting for the electrodes but ultimately for the functioning of the lamp. D24 represents a bidirectional one Zener diode (or suppressor diode or a varistor) is and serves as a threshold value component for decoupling in various operating states.

FIG. 2 shows a second embodiment and differs from FIG the first embodiment of Figure 1 as follows. For simplification are reference numerals to already designated in Figure 1 elements to whose Function has changed nothing essential, omitted.

Notwithstanding the serial connection of the two lamps LA1 and LA2 in Figure 1, here are the two lamps LA1 and LA2 in parallel load circuits connected. Therefore, no preheating transformer is necessary; rather, it is done Direct preheating of the respective lamp electrodes via the PTC resistor R1 for the lamp LA1 and the PTC resistor R111 for the Lamp LA2.

As a device for lamp current measurement of the differential current transformer is used TR2, which here, however, in deviation to Figure 1, only the lamp current the lamp LA1 measures. In lamp operation so acts the lamp current the lamp LA1 as a controlled variable, wherein the separate resonant circuit the lamp LA2 runs on the regulated for the lamp LA1 frequency. It but would also be conceivable, the regulated lamp current from shares of (in this case) to form two lamp currents.

The voltage divider circuit of D24, C20 and R20 in Figure 1 correspond here the separate voltage divider circuits on the one hand C22, R2, R9, D51 and on the other hand C20, R17, R20, D50 on the each greater potential dominates, via the diodes D5 and D13 for blocking the continuous operation control circuit and via the diodes D70 and D101 with the resistor R7 for the voltage regulation circuit. It is a matter of an exclusive OR link.

In place of the two balanced coupling capacitors C15 and C16 from Figure 1 occur here the coupling capacitors C17 and C160. In difference to Figure 1 is here only one coupling capacitor to a lamp terminal connected. However, this is a parallel connection two lamps (more generally an even parallel connection) of lamps), this is also a symmetrical solution as a result, not to disadvantageous current loads of the storage capacitor C6 (see Figure 1) leads.

Figure 3 shows a third embodiment, which differs from the first embodiment differs from Figure 1 as follows. Again, reference numerals omitted.

First, only a single discharge lamp LA1 is provided here, so that the heating transformer TR1 of Figure 1 can be omitted.

Furthermore, there is only one pump branch, which eliminates the components D6-D8, C10, L1. In addition, there is no differential current transformer here. Instead the lamp current is connected in series to the coupling capacitor C16 via a Measuring resistor R21 measured (and that with the factor C16 / (C15 + C16) multiplied load circuit current) and a resistor R22 to the Base of the operational amplifier U2-A replacing bipolar transistor T4 (impedance converter) given. This bipolar transistor functions here as Control amplifier of the continuous operation control circuit. The diodes D7 provide ensure that only the positive half-wave is taken into account in the lamp current measurement is to gain a suitable potential for the variable gain amplifier.

The lamp electrodes of the single lamp LA1 are directly without Pre-heating transformer via the TISP / SIDAC D17 and the PTC resistor R3 preheated. To the regulation of the preheating and igniting the Lamp LA1 flowing load circuit current to suppress and the voltage regulation over C20, D24, R20, D16 will be the one in these operating modes exploited large voltage drop across the PTC resistor R3, to inject a negative current via C17 and D8 and thus the bipolar transistor T4 lock.

The RC element R22 / C21 forms analogous to Figure 1, the arithmetic mean the voltage proportional to the lamp current via R21, which exceeds the Emitter follower T4 is given to the VCO input (base T3). The diode D16 limits the negative voltage at the base of T4 to its forward voltage, the series connection D10 / D11 passes the positive current half-wave by D17 against the reference potential (ground), without the positive voltage at the base of T4 in the burning operation of the lamp limit.

Claims (11)

Electronic ballast for at least one discharge lamp (LA1, LA2) with preheatable electrodes having ballast
a continuous duty control circuit (TR2, GL1, R21-25, 32, C21, U2-A, D23, C4, D9, RT, CT, R12, C12, T3, D15, D7, T4) for controlling the lamp current or the lamp power in Lampendauerbetrieb over the operating frequency of the lamp,
a preheat timer (R1, R111, R3) defining a preheat time for the electrodes, which is arranged to define the preheat time by a physical process occurring with a time delay, and then to retrace this process with a time delay thereafter;
wherein the ballast is adapted to ignite the lamp independently of the continuous duty control circuit when the physical operation of the preheat timer has expired,
characterized in that the ballast is further adapted to operate the continuous duty control circuit (TR2, GL1, R21-25, 32, C21, U2-A, D23, C4, D9, RT, CT, R12, C12, T3, D15; D7, T4) for the Lampendauerbetrieb then put out of action when the preheating (R1, R111, R3) after a service interruption of the lamp (LA1, LA2) due to a not yet completed return of its physical process can not define a complete new preheating, so that the lamp can then be ignited independently of the continuous operation control circuit. Ballast according to Claim 1, in which the non-operational setting of the continuous operation control circuit (TR2, GL1, R21-25, 32, C21, U2-A, D23, C4, D9, RT, CT, R12, C12, T3, D15, D7, T4) is effected in that at least a temporal portion of the lamp voltage or a value directly correlated therewith is applied to an input of a control amplifier (U2-A) or switching transistor (T4) of the continuous operation control circuit. Ballast according to claim 1 or 2, wherein the preheating timer a PTC resistor (R1, R111, R3) contains. A preheat timer as claimed in claim 3, in which the PTC resistor is connected in series (R3) is a threshold device (D17) located below does not conduct a certain voltage threshold. Ballast according to one of the preceding claims, in which a Lamp current measurement for continuous operation control circuit (R21, 22, D7, T4, C4, D9, RT, CT, R12, C12, T3, D15) in series with a lamp electrode with a supply branch connecting coupling capacitor (C 16) takes place. Ballast according to Claim 5, in which a diode (D7) is provided for this purpose is, in the serial lamp current measurement only one each Half-wave of the lamp current to be considered. Ballast according to one of claims 1-4, wherein a lamp current measurement for continuous operation control circuit (TR2, GL1, R21-25, 32, C21, U2-A, D23, C4, D9, RT, CT, R12, C12, T3, D15) via a Differential transformer (TR2) takes place, the differential transformer when measuring, the difference between the total lamp current and forms the Elektrodenheizstrom. Ballast according to one of the preceding claims, with a Voltage regulation circuit (D24, C20, R20, D16, C4, D9, RT, CT, R12, C12, T3, D15; D50, D51, R9, R2, R17, R7, C22, D101, D70) for adjustment the ignition voltage of a lamp resonant circuit (LD1, C5, C9; LD2; L1) by influencing the frequency with which the lamp resonant circuit is supplied: Ballast according to claim 2, also in conjunction with one of the claims 3-8, which is designed to have a plurality of parallel connected Operate lamps (LA1, LA2), wherein the temporal portion of the lamp voltage or the directly correlated size of the parallel switched lamps by an exclusive-OR operation (D5, D13) applied to the input of the control amplifier (U2-A) or switching transistor becomes. Method for operating a discharge lamp (LA1, LA2) with preheatable electrodes, in which
with a preheat timer (R1, R111, R3) in which a physical process expires with a time delay, to define a preheat time, and then to retrace the physical process with a time delay thereafter,
preheat the electrodes during the preheating time,
to ignite the lamp when the physical operation of the preheating timer has expired,
lamp operation or lamp power over the operating frequency of the lamp in continuous lamp operation with a continuous operation control circuit (TR2, GL1, R21-25, 32, C21, U2-A, D23, C4, D9, RT, CT, R12, C12, T3, D15; D7, T4),
characterized in that in the method, the continuous duty control circuit (TR2, GL1, R21-25, 32, C21, U2-A, D23, C4, D9, RT, CT, R12, C12, T3, D15, D7, T4) is disabled for the Lampendauerbetrieb if the preheating (R1, R111, R3) after a turn off the lamp (LA1, LA2) due to an incomplete return of its physical process can not define a new preheat, and then the lamp regardless of the Continuous operation control circuit is ignited. The method of claim 10, wherein a ballast after a of claims 1-9 is used.

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