EP0247218A1 - Supply circuit for gaseous discharge lamps - Google Patents

Abstract

In order to supply gas discharge lamps, a regulated operating AC voltage is applied to the gas discharge lamp, the gas discharge lamp circuit is interrupted with respect to DC, a DC voltage is furthermore superimposed on the operating AC voltage, and the DC voltage is increased until the voltage resulting from the superimposition exceeds the ignition voltage of the gas discharge lamp and the gas discharge lamp is ignited. A circuit arrangement is used for carrying out this process which has a transformer whose inputs are connected to a regulated operating AC voltage. The transformer (TR1) is provided with high-voltage outputs which are fed to a rectifier (G1) whose output is fed via a current limiter (B) to a connecting terminal (a) of the gas discharge lamp (L), this connecting terminal (a) furthermore being connected via an isolating capacitor (TC) to a terminal or to a coil of a transformer (TR1) protecting the operating current, while the other connecting terminal (b) of the gas discharge lamp (L) is connected directly to the other terminal of the coil of the transformer (TR1) protecting the operating current. <IMAGE>

Description

The invention relates to a method and a circuit arrangement for feeding gas discharge light sources.

The invention can be used in particular in the case of high-frequency feeding of gas discharge light sources by means of electronic voltage converters.

Up to now, only high-voltage, high-frequency pulses have been used for the ignition of light sources which require a high ignition voltage, in such a way that they have been superimposed on an operating voltage or have been synchronized therewith in order to ensure that the operating current is formed immediately after the ignition . The various known methods differ from one another only in the generation of the pulses, in the superimposition on the operating voltage or in the synchronization that takes place for this purpose. The lack of superimposition and synchronization often lead to unsuccessful attempts to ignite, which accelerates the decay, the aging of the cathodes.

The ignition pulse is generated in most cases by means of a transformer connected in series in the lamp circuit in such a way that a capacitor is discharged via the primary coil, such a solution is known from GB-PS 1397031, in which a capacitor is operated by means of a manually operated switch is discharged via the primary coil of a transformer connected in series with its secondary coil to the discharge lamp. The energy of an ignition pulse generated in this way is constant and be Damages the new lamp unnecessarily, since its ignition voltage requirement is lower. After ignition, this solution uses serial, passive control to ensure the appropriate power supply to the light source.

The ignition circuits generally repeat the ignition process until an operating current begins to flow or until a defective element (e.g. a bimetal glow discharge igniter) of the ignition circuit fails. In the event of circuit faults (if the operating current cannot develop as a result of a fault in the supply circuit), such ignition attempts also damage the cathode of the lamp which is still intact. In the case of the ignition of gas discharge light sources, the large re-ignition voltage which arises in the unloaded state of the feed transformers is used in a significant part of the known solutions. This re-ignition voltage depends to a large extent on the supply voltage and the excitation.

For the ignition of gas discharge lamps, e.g. a solution is known from US Pat. No. 4,004,188 in which the ignition takes place by means of a separate ignition electrode, an ignition transformer. This technical solution contains a high-voltage pulse generator and is supplemented by a synchronization unit. This patent document deals with the synchronization by means of an inverter.

Methods are known from the literature which limit those at the collector of the output transistor of (fly back voltage) in order to avoid that the voltage increases to an impermissible degree. The common feature of these methods is that they derive the additional energy which is produced by means of some circuit arrangement, so the span peak, but it also causes a significant loss. For this purpose, the methods and circuit arrangements serve, for example, to implement a slow voltage rise.

Several different methods are also known for regulating the power supplied to the gas discharge light source. In self-oscillating converters, a magnetic circuit controlled to the saturation state realizes an approximately power-proportional control based on the saturation current, but this depends to a large extent on the supply voltage and the impedance of the light source. A brief increase in the supply voltage therefore leads to a significant overload, which leads to a reduction in the life of the light sources. Since the impedance of the gas discharge light sources is negative and depends on many factors (gas pressure, temperature, burning voltage and current, etc.), the deviations in manufacture and the environmental effects lead to significant differences and instabilities.

In regulated voltage transformers, the current of the light source is generally stabilized (see e.g. the above GB-PS), however, the power fluctuations due to the environmental influences and the spread of the operating voltage cannot be prevented. In the last third of the life of the light sources, there is a significant increase in the operating voltage and the steadily increasing lamp output accelerates the damage of the lamps.

A common disadvantage of the known solutions is that they require relatively complicated and costly circuit units or that manual operation is required. When using high-frequency operating voltage, the disadvantages are exacerbated by the fact that, in the additive superimposition of the ignition pulse, the separation from the type drive circuits can no longer be completely secured due to the proximity of the frequencies, so the reaction of the ignition pulse leads to further disadvantages. The comparability of the impedances results in high losses.

The aim of the invention is to eliminate the disadvantages of the known solutions and to develop a method and a circuit arrangement by means of which the disadvantageous effect of the factors which lead to a reduction in the service life of the gas discharge light sources can be reduced.

The invention is based on the knowledge that, in particular in the high-frequency range (20-100 kHz), the ignition pulses, which contain frequency components of 100-1 MHz, cannot be separated from the primary circuit in terms of their effect, but the pulses which are opposite to the Period time have significantly lower time constant, can be separated effectively and with this the ignition can also take place with greater certainty. The invention is further based on the knowledge that the capacitor storing the ignition pulse can be connected directly to the operating circuit of the light source, which can thus simultaneously perform the function of separating the low frequency.

Another finding made it possible to simplify the implementation of the circuit arrangement, namely that the ratio of the direct current component which the light source endures without damaging the light source to the operating current can be substantially greater than the ratio of the operating impedance of the light source to the cold resistance of the light source. This means that the internal impedance of the high-voltage circuit used to charge the ignition capacitor can be chosen to be so great that during operation, even without switching off the high voltage, the light source flowing direct current and the losses occurring in the ignition circuit are negligible.

A further finding of the invention is based on the fact that by improving the functional parameters of the voltage converters, keeping the ignition voltage constant in the entire range of the supply voltage and / or by stabilizing the power delivered to the light source in a wide range of environmental influences, the service life of the gas discharge light sources is significantly increased can be. It was recognized that in the unloaded or lightly loaded output transformers of the voltage transformers, the re-ignition voltage can be changed within extremely wide limits by changing the excitation time. (In the other parts of the description, the term "unloaded" also includes the lightly loaded circuits.)

It was also recognized that the ignition characteristic of the gas discharge lamp does not deteriorate when the frequency of the ignition pulses increases.

This fact is surprising since a reduction in the readiness to ignite would be expected on the basis of the Penning effect due to the service life and the excitation energy of the metastable state of the filling gas.

It was also recognized that for the stabilization of the output power, the stabilization of the power consumed by the voltage converter by changing the operating factor of the output voltage - the operating factor means the switch-on time expressed as a percentage of the period - is sufficient, i.e. one can disregard the fluctuation in the efficiency of the voltage converter caused by the environmental change.

The object of the invention is therefore the increase in the service life of the gas discharge light sources by reducing the unsuccessful ignition attempts and / or by avoiding overloading during operation. Unsuccessful ignition attempts can be reduced by increasing the readiness to ignite.

The invention relates to a method for igniting gas discharge light sources, in which a regulated alternating operating voltage is applied to the gas discharge light source and, according to the invention, the circuit of the gas discharge light source is interrupted with regard to the direct current, and furthermore a direct voltage is superimposed on the alternating operating voltage, the direct voltage being increased as long as until the voltage resulting from the superimposition of the alternating operating voltage and the direct voltage, including a direct voltage component and an alternating voltage component, exceeds the ignition voltage of the gas discharge light source and the gas discharge light source is ignited.

In one embodiment of the invention, the current required to generate the DC voltage component is switched off after the gas discharge light source has been ignited.

In a further preferred embodiment of the invention, the current required to generate the DC voltage component is selected to be several orders of magnitude smaller than the operating current of the gas discharge light source and is maintained after ignition.

In order to carry out the method according to the invention, a circuit arrangement was also formed which has a transformer, the inputs of which are applied to a regulated operating AC voltage and, according to the invention, the transformer is designed with high-voltage outputs which are connected to a Rectifiers are guided, while the output of the rectifier is led via a current limiter to a connection terminal of the gas discharge light source, a connection terminal of the coil securing the operating current of the transformer being connected via an isolating capacitor, while the other connection terminal of the gas discharge light source is connected directly to the other Terminal of the coil securing the operating current of the transformer is connected.

To carry out the method, a further circuit arrangement was created in which an impedance that limits the operating current is applied to one terminal of an operating alternating voltage, wherein according to the invention the impedance is connected to a connecting terminal of the gas discharge light source via a separating capacitor, while the other connecting terminal of the gas discharge light source is connected to the another terminal of the regulated operating AC voltage is guided, a primary coil of a transformer being connected between the common switching point of the impedance and the isolating capacitor and the other terminal of the operating AC voltage, the secondary coil of which is connected to a rectifier, while the output of the rectifier is connected to the one via a current limiter Connection terminal of the gas discharge light source is connected.

The invention further relates to a method for generating a regulated alternating operating voltage suitable for supplying gas discharge light sources, the re-ignition voltage occurring in unloaded drive transformers being used to increase the readiness for ignition of the gas discharge light source and / or the power given to the gas discharge light source by changing the operating factor (DUTY CYCLE) the output voltage is regulated and according to the invention, the optimum ignition voltage of the light source and the re-ignition voltage required to achieve the optimum ignition voltage are determined, to which a predetermined reference voltage value is assigned, and furthermore the drive transformer is excited for any period of time at a selected supply voltage in the frequencies corresponding to the frequencies customary in voltage converters, then the current of the primary circuit is interrupted at high speed and a signal proportional to the re-ignition voltage is derived from the drive transformer, then the signal proportional to the re-ignition voltage is compared with the reference voltage value and, in the event of a deviation, the excitation time of the transformer - by means of a value control system known per se - is changed in such a way that when the signal value is lower than the reference voltage value, the excitation period increases and when the signal value is lower it increases compared to the reference voltage value Ren signal value the duration of excitation is reduced and / or the output power of the voltage converter is regulated in such a way that the output power is added to the power loss and as a result the nominal input power to be received from the supply source is obtained, which is assigned an internal reference value that continues during the operation of the voltage converter will compare the instantaneously absorbed power or an associated value of an electrical quantity with the internal reference value; if there is a deviation, the operating factor of the output voltage is changed by means of a value control system known per se.

In one embodiment of the method, the instantaneous power of the voltage converter is determined in such a way that the instantaneous supply voltage of the voltage converter and the current consumed are measured and the product of these measured Values is formed.

In a further exemplary embodiment, a nominal signal value determined when the voltage converter is supplied with nominal power is assigned, the current supply voltage and the current are measured, and proportional signals are formed, the circuit elements measuring the current supply voltage and the current being selected in this way that at a nominal value the proportional signals agree with each other - and with half of the signal value assigned to the nominal power - furthermore the sum of the signals corresponds to the power currently consumed.

For better understanding, this exemplary embodiment will also be explained in more detail below using a numerical example. It is assumed that the nominal parameters of the voltage transformer are as follows: 20V, 1A is determined as the internal reference value 1V, then in this embodiment of the invention the circuit elements measuring the current supply voltage and the current consumed are selected in such a way that they have a nominal value The value of the signal value proportional to the current supply voltage and the absorbed current is 0.5 V. If the nominal current is increased to 2H (double), the value of the circuit element measuring the current must be reduced by half in order to ensure that the signal generated is also 0.5 V at nominal value.

In this embodiment of the invention, the percentage size of the error made is greater than that of the actual power control, which is based on the product of current and voltage, but this embodiment is significant because of the simpler design of the circuit and the lower manufacturing costs extremely advantageous.

In order to carry out the method for generating a regulated alternating operating voltage suitable for supplying gas discharge light sources, a circuit arrangement was created which has a control unit, a drive unit connected to the control unit and a transformer connected to the drive unit, the outputs of the transformer being the outputs of the circuit arrangement (voltage converter ) form. According to the invention, the transformer is provided with a further output terminal, to which a feedback unit is connected, the output of which is led to an input of a control unit, while the output of the control unit is connected to an input of the drive unit and / or the control unit is a unit for formation of a power proportional signal.

In an advantageous embodiment of the invention, the transformer is provided with a feedback coil, while the feedback unit has a diode and a filter capacitor, an output terminal of the feedback coil is connected to the filter capacitor via the diode, and the common switching point of the diode and the filter capacitor forms the output of the feedback unit . It is furthermore advantageous if a zener diode is arranged in the control unit, one connection of which is connected to the input of the control unit and the other connection of which is connected to the output of the control unit.

In a further embodiment of the invention, the unit for forming a power-proportional signal has a control transistor whose emitter is connected to the other input terminal, which is led to the combined circuit point via a current monitoring resistor. The base of the control transistor is at the common point of a voltage divider lers connected, one resistor is connected to the combined node, while the other resistor is connected to another input terminal of the voltage converter. The collector of the control transistor is connected to the output of the unit to form a power-proportional signal.

Further explanations are given in the claims below. The invention is explained in more detail below on the basis of preferred exemplary embodiments with reference to the accompanying drawings.

• Fig. 1 eine Ausführungsform der erfindungsgemässen Schaltungsanordnung zur Zündung von Gasentla­dungslichtquellen mit Transformatoranpassung,
• Fig. 2 eine weitere Ausführungsform der erfindungs­gemässen Schaltungsanordnung zur Zündung von Gasentladungslichtquellen mit in Reihe geschal­teter Impedanz,
• Fig. 3 ein Blockschema der erfindungsgemässen Schal­tungsanordnung zur Erzeugung einer zur Spei­sung von Gasentladungslichtquellen geeigneten, geregelten Betriebswechselspannung,
• Fig. 4 eine Ausführungsform eines eintaktigen selbst­schwingenden Umformers, und
• Fig. 5 eine weitere Ausführungsform der mit einer speziellen Einheit zur Bildung eines leistungs­proportionalen Signals, sowie mit einem gesteuer­ten Generator ausgebildeten erfindungsgemässen Schaltungsanordnung.

The drawings show:

• 1 shows an embodiment of the circuit arrangement according to the invention for igniting gas discharge light sources with transformer adaptation,
• 2 shows a further embodiment of the circuit arrangement according to the invention for igniting gas discharge light sources with an impedance connected in series,
• 3 shows a block diagram of the circuit arrangement according to the invention for generating a regulated operating alternating voltage suitable for supplying gas discharge light sources,
• Fig. 4 shows an embodiment of a single-stroke self-oscillating converter, and
• 5 shows a further embodiment of the circuit arrangement according to the invention, which is designed with a special unit for forming a power-proportional signal and with a controlled generator.

As can be seen from FIG. 1, an operating alternating voltage is applied to the inputs of a transformer TR1, the high-voltage outputs of which are led to a rectifier G1. The output of the rectifier G1 is led via a current limiter B to a connection terminal a of a light source L. This to Terminal a is also connected via a isolating capacitor TC to one terminal of the coil of the transformer TR1 ensuring the operating current of the light source, while the other connecting terminal b of the light source L is directly connected to the other terminal of the coil of the transformer TR1 ensuring the operating current.

The embodiment shown in Figure 1 works as follows:

An operating alternating voltage is connected to the inputs of the transformer, whereupon an idling operating voltage appears at the terminals of the coil of the transformer TR1 that secures the operating current, which voltage reaches the connection terminals a, b of the light source L via the isolating capacitor TC. A highly transformed voltage appears at the high-voltage outputs of the transformer TR1, which, rectified via the current limiter B, feeds the isolating capacitor TC with charging current. Since no current flows through the light source L, a voltage rise proportional to the capacitance and the current can be seen at the isolating capacitor TC.

Since the time constant of the voltage rise is a multiple of the period of the operating AC voltage, a continuously increasing voltage appears at the connection terminals a, b of the light source L, which voltage is superimposed on the open circuit operating voltage. When the composite voltage reaches the ignition voltage of the light source, the light source L ignites and the open circuit operating voltage drops to the level of the burning voltage. By using a switch in the ignition circuit, the ignition voltage can be switched off and no DC component reaches the output. In a preferred embodiment, if the current limiter has a very high internal resistance, the direct current that has reached the output is DC component negligible even without interruption.

In the embodiment according to FIG. 2, the double function of the transformer used to adapt the light source was separated. A series-connected impedance I serves to limit the current, while the high voltage is generated by the transformer TR2.

Accordingly, the one input terminal of the operating AC voltage is connected via the impedance and the isolating capacitor TC to the one connection terminal a of the light source L, while the other input terminal of the operating AC voltage is connected directly to the other connection terminal b of the light source L.

A primary coil of a transformer TR2 is connected between the common circuit point of the impedance I and the isolating capacitor and the other input terminal of the operating AC voltage, while the secondary coil of the transformer TR2 is connected to a rectifier G1, the output of which is connected via a current limiter B to the one connecting terminal b of the light source L is connected.

The function of the embodiment shown in FIG. 2 differs from that shown in FIG. 1 in that the operating AC voltage applied to the input reaches the light source L practically without reduction and this only decreases to the value of the burning voltage after the light source L has been ignited , and that the ignition voltage is generated by a separate transformer TR2. In a further embodiment, the transformer TR2 can be designed with a large internal impedance and thus the impedance of the current limiter B can be built into the transformer TR2 in part or in full.

Both the embodiment shown in FIG. 1 and the embodiment in FIG. 2 can also be implemented in this way is that an interrupter is inserted in any element of the ignition circuit or between the elements at any point, which is controlled by means of a comparator which detects the ignition of the light source L in any known manner (for example by current monitoring, voltage monitoring) and then likewise interrupts the circuit in a known manner.

The above-described embodiments of the invention enable the ignition of light sources which require a high ignition voltage (for example high-pressure gas discharge lamps) primarily in the case of high-frequency supply in a simple manner in such a way that minimal losses occur and there is no adverse reaction in the supply circuit .

3 shows a block diagram of the circuit arrangement according to the invention for generating a regulated alternating operating voltage suitable for supplying gas discharge light sources. In this circuit arrangement, a supply voltage U is _an applied while the gas discharge light source can be connected to the outputs 27,28 of the input terminals 1,2. The input terminal 2 is connected via an input 4 to a control unit S, the output 7 of which is connected to an input 14 of a drive unit A.

The output 17 of the drive unit A is connected to the connection 22 of the transformer TR3. The outputs 25, 26 of the transformer TR3 form the outputs 25, 26 of the voltage converter, at which the voltage U _out appears. The transformer TR3 is provided with a further output terminal 24, to which an input 20 of a feedback unit K is connected. An output 18 of the feedback unit K is connected to an input 12 of a control unit R, while an output 10 of the controller tion unit R is connected to an input 15 of the drive unit A and a further output 8 of the control unit R to an input 6 of the control unit S. The input terminal 1 is connected to a connection 3 of the control unit S, a connection 21 of the transformer TR3, and - if necessary - to a connection 11 of the control unit R and a connection 13 of the drive unit A.

The connections 5, 9, 16, 19 of the individual units of the voltage converter according to FIG. 3 are routed to a combined circuit point of the circuit arrangement, to which the output terminal 23 of the transformer TR3 is also routed.

The embodiment of the invention shown in FIG. 3 functions as follows:

The control unit S switches off the excitation from the transformer TR3 after a predetermined time at high speed with the aid of the drive unit A, and since no current can flow via the cold light source connected to the outputs 25, 26 of the transformer TR3, the inductance is induced in all coils Transformer TR3 a re-ignition voltage with a large peak value.

The voltage appearing at the output terminal 24 of the transformer TR3 arrives in the feedback unit K via its input 20, which rectifies, filters, transforms and passes this on from its output 18 to the input 12 of the control unit R. The control unit R compares the signal received at its input 12 with its internal reference signal and delivers a signal proportional to the deviation via its outputs 8 and 10 to the input 6 of the control unit S and to the input 15 of the drive unit A. On the effect of the signals the control unit S and the drive unit A increase or decrease the duration of the next excitation cycle. About the on The effect of the ignition pulses when the light source is switched on, a current flows and takes up a significant amount of power from the transformer TR3 and loads the drive unit A in the ratio of the transmission ratio, thus producing a significant supply current.

A signal proportional to the power consumed is supplied by the unit E shown in FIGS. 4 and 5 to form a power-proportional signal or by the transistor T2, with this signal the internal circuits of the control unit S in a known manner the operating factor of Regulate control voltage appearing at output 7 of control unit S.

4 shows an exemplary embodiment for the application of the new methods in self-oscillating single-ended converters. 4 shows, with the exception of the control unit S, a detailed circuit arrangement of the voltage converter designed according to the invention, this circuit arrangement representing a possible, single-cycle, self-oscillating embodiment.

4, the transformer TR3 is formed with a primary coil L1, a feedback coil L2 and a secondary coil L3. The terminal 24 of the feedback coil L2 is connected to the filter capacitor C2 via a diode D2. In the present exemplary embodiment, the feedback unit K shown in FIG. 3 corresponds to the diode D2 and the filter capacitor C2. The common point of the diode D2 and the filter capacitor C2 forms the output 18 of the feedback unit K.

4, a Zener diode D1 is arranged, one terminal of which forms the input 12 of the control unit R, while the other terminal of the Zener diode D1 forms the output 10 of the control unit R. According to the output 10 Fig. 3, the corresponding input 15 of the drive unit A is connected. 4, the drive unit A is formed with a transistor T1, the base b1 of which is connected to the output 10, the output 7 of the control unit S and, via a capacitor C1, to an output 26 of the secondary coil L3. The collector c1 of the transistor T1 is connected to a terminal 22 of the primary coil L1 of the transformer TR3, while the emitter e1 of the transistor T1 is led to the combined circuit point of the filter capacitor C2, the other output terminal 23 of the feedback coil L2 and the output 16 of the drive unit A. . This combined circuit point simultaneously forms the one output 28 of the voltage converter in the present exemplary embodiment, while the other output 27 forms the other output of the secondary coil L3 of the transformer TR3. The output terminal 24 of the feedback coil L2 is connected to the capacitor C1 via a resistor R1. Another connection 21 of the primary coil L1 is connected to the one input terminal 1 of the voltage converter, while the other input terminal 2 is connected to the input 4 of the control unit S. The unit E in the control unit S for forming a power-proportional signal, with its connections 29, 30, 31, 32 and its output 33, is connected in a corresponding sequence to the connection 3, the input 4, the connection 5, the input 6 and the Output 7 of the control unit S out.

The voltage converter shown in Fig. 4 works as follows:

A signal proportional to the re-ignition voltage is taken from the transformer TR3 by the feedback coil L2, which signal is rectified by the diode D2 and filtered by the capacitor C2. When this tension passes through let voltage of the Zener diode D1 exceeds, this conducts a negative current into the base b1 of the transistor T1. As a result, the transistor T1 is biased in the negative direction, as a result of which its opening time is reduced and the value of the re-ignition voltage U _CEV generated is reduced. The current that begins to flow via the Zener diode D1 simultaneously increases the load on the transformer TR3 due to the coupling with the feedback coil L2, thereby contributing to the limitation of the re-ignition voltage. The output 26 of the secondary coil L3 connected at the common point of the resistor R1 and the capacitor C1, which is required for the self-oscillating basic circuit, also contributes to the regulation, by means of which a positive feedback is realized and the number of turns of the secondary coil L3 can be selected to be low .

A further advantage can be ensured in that the resistor R1 is designed with a negative temperature coefficient. The operating factor can be changed to a limited extent by regulating the operating point base current of the transistor T1. During the ignition process, the base current output at the output 7 is increased to the signal appearing at the input 6 of the control unit S when the re-ignition voltage is low and is reduced when the re-ignition voltage is high, which also supports the back regulation.

After the ignition, the unit E regulates the base current of the transistor to the desired extent to form a power-proportional signal.

A possible embodiment of the control unit S and its connection to the other units of this exemplary embodiment is illustrated in more detail with reference to FIG. 5.

The unit arranged in the control unit S. E to form a power-proportional signal is provided with a control transistor T2, the emitter e2 of which is connected directly to the other input terminal 2, which is led to the combined switching point via a current monitoring resistor R2. The base b2 of the control transistor T2 is connected to the common point of a voltage divider, the one resistor R4 of the voltage divider being connected to the combined circuit point, while the other resistor R3 of the voltage divider is connected to the one input terminal 1 of the voltage converter. The collector c2 of the control transistor T2 is connected to the input 34 of a generator G designed with a variable operating factor. Another input 36 of the generator G is led to the output 8 of the control unit R, while an output 35 of the generator G - which also forms the output 7 of the control unit S - is connected to the input 14 of the drive unit A.

The embodiment of the circuit arrangement according to the invention shown in FIG. 5 functions as follows:

The transformer TR3 is excited by the drive unit A in accordance with the control voltage obtained from the output 35 of the generator G. During the ignition cycle, the generator G receives a control voltage corresponding to the ratio of the re-ignition voltage to the internal reference value via its input 6 from the output 8 of the control unit, and accordingly controls the excitation time.

After the ignition, the generator G is controlled via its input 34 by the collector c2 of the control transistor T2 by comparing the sum of the voltage across the resistor R2 (which is proportional to the current flowing through the resistor R2) and the voltage proportional to the supply voltage the voltage consisting of resistors R3 and R4 divider, with the forward voltage between the base b2 and the emitter e2. Based on the signal resulting from the comparison, the generator G changes the operating factor of the control voltage appearing at its output 35 in a known manner.

The method according to the invention and the circuit arrangement designed to carry out the method enable the light sources to ignite when the supply voltage is low and there are no losses when the supply voltage is high, and the converter does not become defective. The power control secures the supply of the light source with the set power in a wide supply voltage and temperature range. A disadvantageous effect that appears with the power control is the power loss that occurs at the current monitoring resistor R2. This loss can be reduced on the one hand by increasing the sensitivity of the unit E to form a power-proportional signal and on the other hand is compensated for by the significant improvement in the functional properties of the circuit arrangement, since the power stabilization can be implemented much better than the previously known solutions.

Claims (14)

1. A method for igniting gas discharge light sources, wherein a regulated alternating voltage is applied to the gas discharge light source, characterized in that the circuit of the gas discharge light source is interrupted with respect to the direct current, that a direct voltage is superimposed on the operating voltage that the direct voltage is increased until the due to the superimposition of the operating alternating voltage and the direct voltage resulting, having a direct voltage component and an alternating voltage component, the ignition voltage of the gas discharge light source exceeds and the gas discharge light source is ignited. 2. The method according to claim 1, characterized in that after ignition of the gas discharge light source, the current required to generate the DC voltage component is switched off. 3. The method according to claim 1, characterized in that the current required to generate the DC voltage component is selected by several orders of magnitude smaller than the operating current of the gas discharge light source and is maintained after the gas discharge light source has been ignited. 4. A method for producing a suitable operating AC voltage suitable for supplying gas discharge light sources, in particular according to claim 1, wherein the re-ignition voltage occurring in unloaded drive transformers is used to increase the readiness for ignition of the gas discharge light source and / or the power given to the gas discharge light source by changing the operating factor of the output voltage is regulated, characterized in that the optimum ignition voltage of the light source and the re-ignition voltage required to achieve the optimum ignition voltage are determined, to which a predetermined reference voltage value is assigned, that the drive transformer is energized for any period of time at a selected supply voltage, within the limits corresponding to those common in voltage converters, so that Current of the primary circuit of the transformer is interrupted at high speed and a signal proportional to the re-ignition voltage is derived from the drive transformer, that the signal proportional to the re-ignition voltage is then compared with the reference voltage value and, in the event of a deviation, by means of a value control system known per se, the duration of excitation of the transformer is changed in such a way that the excitation duration increases when the signal value is lower than the reference voltage value and when the signal value is higher than the reference voltage value the excitation duration is reduced, and / or the output power of the voltage converter is regulated in such a way that the output power is added to the power loss of the converter, so that as a result the nominal input power to be taken up by the supply source is obtained, to which an internal reference value is assigned, that during operation of the voltage converter, the instantaneously consumed power or an associated value of an electrical quantity is determined, that the instantaneously absorbed power or the associated value of an electric quantity is then compared with the internal reference value, and that if there is a deviation, the operating factor of Output voltage - by means of a value control known per se - is changed. 5. The method according to claim 4, characterized in that the current Power of the voltage converter is determined in such a way that the current supply voltage of the voltage converter and the current consumed are measured and the product of the measured values is formed. 6. The method according to claim 4, characterized in that a nominal signal value of the nominal power value determined with nominal supply of the voltage converter is assigned to the inner reference value, the instantaneous supply voltage and the instantaneously consumed current are measured, signals proportional thereto being formed, the instantaneous Supply voltage and the current measuring circuit elements are selected such that at nominal value, the signals proportional to each other - and half of the signal value belonging to the nominal power - match, furthermore, the sum of the signals is assigned to the power currently being consumed. 7. Circuit arrangement for performing the method according to claim 1, which has a transformer, the inputs of which are applied to a regulated operating AC voltage, characterized in that the transformer (TR1) is provided with high-voltage outputs, which are led to a rectifier (G1), the Output is led via a current limiter (B) to a connection terminal (a) of a gas discharge light source (L), this connection terminal (a) being further connected via an isolating capacitor (TC) to a terminal of the coil of the transformer (TR1) securing the operating current, while the other connection terminal (b) of the gas discharge light source (L) is directly connected to the other terminal of the coil of the transformer (TR1) which ensures the operating current. 8. A circuit arrangement for carrying out the method according to claim 1, which has an impedance (I) which is applied to a terminal of an operating alternating voltage and which limits the operating current, characterized in that the impedance (I) via an isolating capacitor (TC) with a connecting terminal (a) a gas discharge light source (L) is connected, while the other connection terminal (b) of the gas discharge light source (L) is connected to the other terminal of the operating alternating voltage, whereby between the common switching point of the impedance (I) and the isolating capacitor (TC) and the other terminal of the Operating alternating voltage, a primary coil of a transformer (TR2) is connected, the secondary coil of which is connected to a rectifier (G1), while the output of the rectifier (G1) is connected via a current limiter (B) to one connection terminal (a) of the gas discharge light source (L) . 9. Circuit arrangement for carrying out the method according to claim 4, which has a control unit, a drive unit following the control unit and a transformer connected to the output of the drive unit, the outputs of the transformer forming the outputs of the circuit arrangement, characterized in that the transformer ( TR3) has a further output terminal (24) to which a feedback unit (K) is connected, the output (18) of which is led to an input (12) of a control unit (R), while the output (10) of the control unit (R) is connected to an input (15) of the drive unit (A), and / or the control unit (S) has a unit (E) for forming a power-proportional signal. 10. Circuit arrangement according to claim 9, characterized in that the transformer (TR3) has a feedback coil (L2), while the feedback unit (K) has a diode (D2) and a filter capacitor (C2), wherein an output terminal (23) of the feedback coil (L2) is connected to the filter capacitor (C2) via a diode (D2) and the common switching point of the diode (D2) and the filter capacitor (C2) forms the output (18) of the feedback unit (K). 11. Circuit arrangement according to claim 10, characterized in that in the control unit (R) a Zener diode (D1) is arranged, one connection to the input (12) of the control unit (R) and the other connection to the output (10) of the Control unit (R) are connected. 12. Circuit arrangement according to claim 11, characterized in that the drive unit (A) has a transistor (T1) whose base (b1) to the output (7) of the control unit (S) to the output (10) of the control unit (R) and via a capacitor (C1) to an output (26) of the secondary coil (L3) of the transformer (TR3), while the collector (c1) of the transistor (T1) is connected to a terminal (22) of the primary coil (L1) of the transformer (TR3) is connected, furthermore the emitter (e1) of the transistor (T1) is applied to the combined circuit point of the filter capacitor (c2), another output terminal (23) of the feedback coil (L2) and the output (16) of the drive unit (A) is, this combined circuit point simultaneously forms an output (28) of the voltage converter, while the other output (27) is formed by another output (25) of the secondary coil (L3), that the one output terminal (24) of the feedback coil (L2 ) about a resistor (R1) is connected to the capacitor (C1), another An Circuit (21) of the primary coil (L1) is connected to one input terminal (1) of the voltage converter, while another input terminal (2) of the voltage converter is connected to the input (4) of the control unit (S). 13. Circuit arrangement according to claim 9 or 12, characterized in that the unit (E) for forming a power-proportional signal contains a control transistor (T2) whose emitter (e2) is connected directly to the other input terminal (2), which via a current monitoring resistor (R2) is led to the combined circuit point, furthermore the base (b2) of the control transistor (T2) is connected to the common point of a voltage divider, wboei a resistor (R4) of the voltage divider to the combined circuit point and a second resistor (R3) of the Voltage divider to which an input terminal (1) is connected, furthermore the collector (c2) of the control transistor (T2) is connected to the output (33) of the unit (E) to form a power-proportional signal. 14. Circuit arrangement according to claim 13, characterized in that the control unit (S) is provided with a generator (G) with a variable operating factor, one input (6) of which is connected to a further output (8) of the control unit (R) and the latter Another input (34) is connected to the output (33) of the unit (E) to form a power-proportional signal, while the output (35) - which also represents the output (7) of the control unit (S) - of the generator (G ) is connected to another input (14) of the drive unit (A).

Images