EP1654913B1 - Ballast for at least one high pressure discharge lamp, method for operating said lamp and lighting system comprising said lamp - Google Patents

Abstract

The invention relates to a ballast for a high-pressure discharge lamp, in particular for a motor vehicle headlight lamp or a projection lamp, which ballast is, according to the invention, in the form of a Class E converter.

Description

The invention relates to a ballast for at least one high-pressure discharge lamp according to the preamble of patent claim 1 and an operating method for at least one high-pressure discharge lamp and a lighting system.

I. State of the art

Such a ballast is for example in the European patent application EP 0 386 990 A2 disclosed. This document describes a ballast, which allows the operation of a metal halide high-pressure discharge lamp with a frequency-modulated voltage, which may be formed, among other things, substantially sinusoidal and whose carrier frequency is in the range of 20 kilohertz to 80 kilohertz. The ballast is designed in two stages. It consists essentially of a boost converter with a downstream inverter, which acts on the lamp with an alternating current. The ignition device consists essentially of a built-up of several diodes and capacitors cascade circuit for voltage multiplication.

The FR 2 674 723 discloses a circuit arrangement for operating a high-pressure discharge lamp, in particular a vehicle headlamp. This circuit arrangement enables the operation of the high-pressure discharge lamp with a reduced number of high-voltage-carrying components.

II. Presentation of the invention

It is the object of the invention to provide a ballast for operating at least one high-pressure discharge lamp, which has a simpler structure. In addition, it is the object of the invention to provide a simplified operating method for a high-pressure discharge lamp. Another object of the invention is to provide an improved lighting system.

This object is achieved by the features of claim 1 and 14, respectively. Particularly advantageous embodiments of the invention are described in the dependent claims.

The ballast according to the invention for operating at least one high-pressure discharge lamp has a voltage converter for generating a substantially sinusoidal alternating current, which is designed according to the invention as a class E converter. Under a class E converter is here a converter according to the publication " Class E - A New Class of High-Efficiency Tuned Single-Ended Switching Power Amplifiers "by Nathan O. Sokal and Alan D. Sokal in the IEEE Journal of Solid-State Circuits, Vol. SC-10, No. 3, June 1975 Understood. The basic scheme of such a class E-converter is in FIG. 20 displayed. The construction and the function of the class E converter, in particular for the so-called non-optimal operation, that is, with a non-optimized load resistance, is on Pages 271 to 273 of the book "Power electronics: converters, applications, and design" by the authors Ned Mohan, Tore M. Undeland and William P. Robbins, second edition 1995, John Wiley & Sons, Inc. described.

By means of the class E converter, a largely sinusoidal alternating current for the at least one high-pressure discharge lamp can be generated in a simple manner. It requires no complex bridge circuits with two or more electronic switches and their control required. The operation of the at least one high-pressure discharge lamp with a substantially sinusoidal alternating current has the advantage that it has no or only a very small harmonic content and therefore no acoustic resonances are excited in the discharge medium of the high-pressure discharge lamp when the frequency of the alternating current is outside the acoustic resonances , Due to the very low harmonic content of the largely sinusoidal alternating current, the effort in the radio interference suppression of the ballast is also low. The sinusoidal lamp current allows a stable, in particular flicker-free lamp operation. The operation of the high-pressure discharge lamp with an alternating current of high frequency of preferably greater than 100 kilohertz allows miniaturization of the ballast according to the invention, so that it can be accommodated in the lamp base. At very high operating frequencies, however, the ignition of the gas discharge in the high-pressure discharge lamp is problematic because the inductance of the ignition transformer is on the order of the lamp impedance and is no longer negligible. It is known in such a case to ignite the gas discharge by means of a pulse ignition device via an auxiliary electrode of the high-pressure discharge lamp, as for example in the European published patent application EP-A 0 868 833 disclosed. According to a preferred embodiment of the ballast according to the invention, the inductance of the secondary winding of the ignition transformer no longer forms a parasitic element, but a functional part of the designed as a class E converter voltage converter and not only during the ignition phase of the high pressure discharge lamp, but during the entire lamp operation. The ballast according to the invention is particularly well suited to the operation of low-pressure discharge lamps, such as high-pressure discharge lamps in motor vehicle headlights or in projection applications, the electrical power between 25 watts and 35 watts, and in particular of high pressure discharge lamps comparatively low burning voltage of less than or equal to 100 volts, or even less than or equal to 50 volts, as with mercury-free metal halide high pressure discharge lamps for power vehicle headlights. The ballasts of these lamps are operated on the vehicle electrical system voltage of the motor vehicle. The voltage load of the controllable switch of the invention designed as a class E converter voltage converter can be kept correspondingly low during operation of the aforementioned high-pressure discharge lamps with low burning voltage, although at a duty cycle of 0.5 of the controllable switch about 3.6 times the value reaches the input voltage of the voltage converter.

The inventively designed as a class E converter voltage converter of the ballast according to the invention is supplied with a DC voltage and advantageously has the features described below. Between the DC voltage inputs of this voltage converter or between its positive DC voltage input and the ground potential, an inductance and the switching path of a controllable switch are connected. Antiparallel to the switching path of this switch, a diode is arranged. Anti-parallel means that the diode is reverse-connected with respect to the direct current provided by the DC voltage source at the DC input of the class E converter.

Parallel to the switching path of the switch and also to the diode, a capacitor is arranged. A parallel circuit to the capacitance is designed as a series resonant circuit, to which the load to be operated is coupled. The series resonant circuit consists in the simplest case of a coil and a capacitor. The aforementioned inductance at the DC voltage input of the voltage converter is preferably dimensioned such that it operates as a constant current source and the current flowing in the closed state over the switching path of the controllable switch or in the open state via the capacitance current from a direct current and a sinusoidal alternating current, of the Series resonant circuit is generated, composed. The controllable switch is preferably switched with a clock frequency which is greater than the resonance frequency of the series resonant circuit to ensure that no voltage is applied to the controllable switch during the switching operations and the switching losses of the switch are correspondingly low. The antiparallel arranged diode prevents a negative voltage builds up over the switching path of the controllable switch of the class E converter.

The ballast according to the invention preferably also comprises an ignition device for igniting the gas discharge in the high-pressure discharge lamp. This ignition device can be arranged in the same housing as all other components of the ballast or spatially separated, for example, in the lamp base of the high-pressure discharge lamp. In order to avoid its own voltage source for the ignition device and additional components, the ignition device is advantageously coupled to its power supply to an inductor, preferably to the operating during lamp operation as a constant current source inductance of the class E converter. This inductance of the class E converter is advantageously designed for this purpose as an autotransformer, in particular if a high supply voltage is required for the ignition device.

According to the particularly preferred embodiments, the ignition device is designed as a pulse ignition device, often referred to in the literature as overlay ignition device. The pulse ignition device has a compact construction and can therefore easily into the lamp base of the high pressure discharge lamp to get integrated. In addition, the secondary winding of the ignition transformer of the pulse ignition device can be formed as part of the series resonant circuit of the class E converter. The inductance of the aforementioned secondary winding is thus also utilized for the series resonant circuit of the class E converter. The capacitance of the class E converter connected in parallel to the switching path of the controllable switch and the capacitance of the series resonant circuit keep the ignition voltage pulses away from the switch of the class E converter, because they can be regarded as short-circuiting for the ignition voltage pulses. If the capacitances are very small, a voltage-limiting component can additionally be used in parallel with the switch or in parallel with the series connection of secondary winding of the ignition transformer and lamp. As a voltage-limiting component, for example, a Zener diode, a suppressor diode or a gas-filled surge arrester can be used. Alternatively, however, the ignition device can also be designed as a DC voltage ignition device or as a resonance ignition device. The aforementioned Gleichspannungszündvorrichtung is advantageously used for very high operating frequencies of the class E converter and also has the advantage that it can be coupled during the ignition phase of the high pressure discharge lamp to the capacitance of the series resonant circuit of the class E converter.

The electrical connections of the at least one high-pressure discharge lamp can be arranged directly in the series resonant circuit of the class E converter or can be inductively coupled to the aforementioned series resonant circuit by means of a transformer. By means of this transformer, an impedance matching of the high pressure discharge lamp can be made to the class E converter and also a galvanic isolation between the high pressure discharge lamp and the class E converter can be achieved.

For DC voltage supply of the inventively designed as a class E converter voltage converter, any DC voltage source can be used, for example, in the case of a motor vehicle headlight high-pressure discharge lamp, the battery or the alternator of a motor vehicle.

Preferably, however, the converter designed as a class E converter is preceded by a step-up converter in order to supply the Class E converter with a stable DC input voltage and regulate the electrical power consumption of the high-pressure discharge lamp via the regulation of the DC input voltage of the class E converter can. If the DC voltage supply of the class E converter obtained, for example, by rectification of the AC line voltage, instead of a boost converter and a buck converter for stabilizing the supply voltage of the class E converter can be used. During the transition from the ignition phase to the stationary operating state of the high-pressure discharge lamp, the power consumption of the high-pressure discharge lamp is advantageously regulated via the height of the supply voltage of the class E converter, in order to ensure the formation of a stable discharge arc. During the transition phase, the components of the ionizable filling of the high pressure discharge lamp evaporate. In order to ensure the shortest possible transition phase and a possible immediate light emission, the high pressure discharge lamp can be operated in this way with significantly increased power during the transition phase. In addition, by varying the supply voltage of the class E converter and / or the switching frequency and / or the Ta ratio of the switching means of the class E converter, an adaptation of the class E converter to the changing during the different phases of operation impedance of the high pressure discharge lamp is achieved become.

A power control of the high-pressure discharge lamp is also possible via the switching frequency or the duty cycle of the controllable switch of the class E converter. However, to avoid high switching losses, the switching frequency and the duty cycle should be selected such that no voltage is applied to the controllable switch of the class E converter during the switching operations.

During the ignition phase of the high-pressure discharge lamp, the switch of the class-E converter is advantageously switched such that a resonance-elevated voltage is provided at the inductance, which is arranged at the DC input becomes. This resonance-boosted voltage can advantageously be used to supply the ignition device.

The ballast according to the invention makes it possible with simple means to generate a largely sinusoidal alternating lamp current. During steady state operation of the high pressure discharge lamp, the lamp is operated with a substantially sinusoidal alternating current whose frequency is slightly above the resonant frequency of the series resonant circuit of the class E converter. The components of the series resonant circuit of the class E converter are preferably matched to the geometry of the discharge vessel and the distance of the electrodes of the high pressure discharge lamp, that the resonance frequency of the series resonant circuit of the class E converter is in a frequency range, free of acoustic resonances of the high pressure discharge lamp is. That is, the resonant frequency lies in a frequency window that is either above the acoustic resonances or located between two adjacent acoustic resonances. This ensures that no acoustic resonances are excited in the high-pressure discharge lamp, because the switching frequency of the class E converter is slightly above the resonant frequency during stationary lamp operation. As a result, a frequency modulation of the lamp current is not necessarily required. In order to obtain the largest possible frequency ranges, which are free of acoustic resonances, the discharge vessel is cylindrical at least in the region of the gas discharge. The aspect ratio, that is, the ratio of electrode spacing and inner diameter of the cylindrical portion of the discharge vessel, is preferably greater than 0.86, and more preferably greater than 2. This shifts the longitudinal acoustic resonance to a low frequency and provides sufficiently wide frequency ranges that are free from acoustic resonances.

III. Description of the preferred embodiments

Figur 1

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des ersten Ausführungsbeispiels der Erfindung

Figur 2

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des zweiten Ausführungsbeispiels der Erfindung

Figur 3

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des dritten Ausführungsbeispiels der Erfindung

Figur 4

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des vierten Ausführungsbeispiels der Erfindung

Figur 5

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des fünften Ausführungsbeispiels der Erfindung

Figur 6

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des sechsten Ausführungsbeispiels der Erfindung

Figur 7

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des siebten Ausführungsbeispiels der Erfindung

Figur 8

Das Steuersignal für den MOSFET und die Drain-Source-Spannung am MOSFET während der Zündphase der Hochdruckentladungslampe für das in Figur 7 dargestellte Ausführungsbeispiel

Figur 9

Das Steuersignal für den MOSFET, die Drain-Source-Spannung am MOSFET sowie den Lampenwechselstrom und den Spannungsabfall über der Hochdnickentladungslampe während des stationären Lampenbetriebs für das in Figur 7 dargestellte Ausführungsbeispiel

Figur 10

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des achten Ausführungsbeispiels der Erfindung

Figur 11

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des neunten Ausführungsbeispiels der Erfindung

Figur 12

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des zehnten Ausfiihrungsbeispiels der Erfindung

Figur 13

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des elften Ausführungsbeispiels der Erfindung

Figur 14

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des zwölften Ausführungsbeispiels der Erfindung

Figur 15

Eine Schaltskizze der Schalttmgsanordnung des Vorschaltgerätes gemäß des dreizehnten Ausführungsbeispiels der Erfindung

Figur 16

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des vierzehnten Ausführungsbeispiels der Erfindung

Figur 17

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des fünfzehnten Ausführungsbeispiels der Erfindung

Figur 18

Eine Seitenansicht einer Hochdruckentladungslampe, die an dem erfindungsgemäßen Vorschaltgerät betrieben wird, in schematischer, teilweise geschnittener Darstellung

Figur 19

Eine Seitenansicht einer Hochdruckentladungslampe, die an dem erfindungsgemäßen Vorschaltgerät betrieben wird und die eine im Sockel integrierte Zündvorrichtung aufweist, in schematischer, teilweise geschnittener Darstellung

Figur 20

Die Schaltskizze eines Klasse-E-Konverters (Stand der Technik)

Figur 21

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des sechzehnten Ausführungsbeispiels der Erfindung

Figur 22

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des siebzehnten Ausführungsbeispiels der Erfindung

Figur 23

Eine Schaltskizze der Schaltungsanordnung des Vorschaltgerätes gemäß des achtzehnten Ausführungsbeispiels der Erfindung

The invention will be explained in more detail below with reference to a preferred embodiment. Show it:

FIG. 1

A circuit diagram of the circuit arrangement of the ballast according to the first embodiment of the invention

FIG. 2

A circuit diagram of the circuit arrangement of the ballast according to the second embodiment of the invention

FIG. 3

A circuit diagram of the circuit arrangement of the ballast according to the third embodiment of the invention

FIG. 4

A circuit diagram of the circuit arrangement of the ballast according to the fourth embodiment of the invention

FIG. 5

A circuit diagram of the circuit arrangement of the ballast according to the fifth embodiment of the invention

FIG. 6

A circuit diagram of the circuit arrangement of the ballast according to the sixth embodiment of the invention

FIG. 7

A circuit diagram of the circuit arrangement of the ballast according to the seventh embodiment of the invention

FIG. 8

The control signal for the MOSFET and the drain-source voltage at the MOSFET during the ignition phase of the high-pressure discharge lamp for the in FIG. 7 illustrated embodiment

FIG. 9

The control signal for the MOSFET, the drain-source voltage at the MOSFET and the lamp AC current and the voltage drop across the high-intensity discharge lamp during stationary lamp operation for the in FIG. 7 illustrated embodiment

FIG. 10

A circuit diagram of the circuit arrangement of the ballast according to the eighth embodiment of the invention

FIG. 11

A circuit diagram of the circuit arrangement of the ballast according to the ninth embodiment of the invention

FIG. 12

A circuit diagram of the circuit arrangement of the ballast according to the tenth embodiment of the invention

FIG. 13

A circuit diagram of the circuit arrangement of the ballast according to the eleventh embodiment of the invention

FIG. 14

A circuit diagram of the circuit arrangement of the ballast according to the twelfth embodiment of the invention

FIG. 15

A circuit diagram of Schalttmgsanordnung the ballast according to the thirteenth embodiment of the invention

FIG. 16

A circuit diagram of the circuit arrangement of the ballast according to the fourteenth embodiment of the invention

FIG. 17

A circuit diagram of the circuit arrangement of the ballast according to the fifteenth embodiment of the invention

FIG. 18

A side view of a high-pressure discharge lamp, which is operated on the ballast according to the invention, in a schematic, partially sectioned illustration

FIG. 19

A side view of a high-pressure discharge lamp which is operated on the ballast according to the invention and which has an ignition device integrated in the base, in a schematic, partially sectioned illustration

FIG. 20

The circuit diagram of a class E converter (prior art)

FIG. 21

A circuit diagram of the circuit arrangement of the ballast according to the sixteenth embodiment of the invention

FIG. 22

A circuit diagram of the circuit arrangement of the ballast according to the seventeenth embodiment of the invention

FIG. 23

A circuit diagram of the circuit arrangement of the ballast according to the eighteenth embodiment of the invention

In FIG. 1 schematically shows the circuit diagram of the ballast according to the first embodiment of the invention. This ballast has a DC input with two DC voltage terminals which are connected to the voltage output of a DC voltage source 100. The positive DC voltage connection is connected via an inductance 101 and the switching path of a controllable switch 102 to the negative DC voltage connection or to the internal circuit ground potential. Antiparallel to the switching path of the switch 102, a diode 103 is connected. Parallel to the switching path of the switch 102 and also in parallel with the diode 103, a capacitor 104 is connected. In a parallel circuit to the capacitor 104, the capacitor 105 and the secondary winding 106 b of a transformer 106 are arranged. The capacitor 105 and the secondary winding 106b form a series resonant circuit. In the series resonant circuit, electrical connections for a high-pressure discharge lamp LP1 are arranged, so that when the lamp LP1 is connected, its discharge path is connected serially in the series resonant circuit. For igniting the gas discharge in the high-pressure discharge lamp LP1, an ignition device 107 is provided which has an ignition transformer 106 with a primary winding 106a and a secondary winding 106b. During the ignition phase of the high-pressure discharge lamp, the required ignition voltage is provided at the electrode of the high-pressure discharge lamp connected to the secondary winding 106b. The ignition device 107 may be formed, for example, as a pulse ignition device.

This in FIG. 2 illustrated second embodiment of the ballast according to the invention differs from the first embodiment in that the high-pressure discharge lamp LP2 is not directly connected in the series resonant circuit of the class E converter, but is coupled via a transformer 208 to the aforementioned series resonant circuit. The transformer 208 with primary winding 208a and secondary winding 208b serves to match the impedance of the lamp LP2 to the class E converter and to electrically isolate the lamp LP2 from the class E converter. Due to the impedance matching, it is also possible to operate high-pressure discharge lamps, which have an operating voltage that deviates greatly from the supply voltage of the class E converter, on the class E converter. The arrangement and function of the components 200, 201, 202, 203, 204 and 205 corresponds to the arrangement and function of the components 100, 101, 102, 103, 104 and 105 of the first embodiment. The ignition device 207 may also be formed as a pulse ignition device. It has an ignition transformer 206 with a primary winding 206a and a secondary winding 206b, wherein the secondary winding 206b is connected together with the high-pressure discharge lamp LP2 in the secondary circuit of the transformer 208. The connected to the secondary winding 206b electrode of the high pressure discharge lamp LP2 is applied during the ignition phase with high voltage pulses. When calculating the resonant frequency of the series resonant circuit of the class E converter, the transmission ratio of the transformer 208 and the value of the capacitance 205 and the inductance of the secondary winding 206b of the ignition transformer 206 must be taken into account.

The transformer 208 may be used for impedance matching in different ways in the circuit according to the FIG. 1 are inserted to get to the second embodiment. For example, the primary winding 208a of the transformer 208 may be inserted at the node between the capacitor 105 and the secondary winding 106b and the node between the capacitor 104 and the high pressure discharge lamp LP1, as in FIG FIG. 2 is shown. Alternatively, the primary winding 208a of the transformer 208 may be inserted at the node between the secondary winding 106b and the high pressure discharge lamp LP1 and the node between the capacitor 104 and the high pressure discharge lamp LP1 (not shown). In the latter case, the transformer 208 may contribute to an increase in the ignition voltage.

This in FIG. 3 illustrated third embodiment of the ballast according to the invention is largely identical to the first embodiment. In particular, the arrangement and the function of the components 300, 301, 302, 303, 304, 305, 306, 306a, 306b and LP3 of the arrangement and function of the respective components 100, 101, 102, 103, 104, 105, 106, 106a, 106b and LP1 of the first embodiment. The only difference between the two embodiments is in the voltage supply of the igniter 307. The igniter 307 is powered by the class E converter. For this purpose, a voltage input of the ignition device 307 is connected to the node between the inductance 301, the controllable switch 302 and capacitor 304 and the other voltage input connected to the ground potential or to the negative DC input of the class E converter.

This in FIG. 4 Illustrated fourth embodiment of the ballast according to the invention differs from the third Ausfühnmgsbeispiel only by the use of an autotransformer 401 instead of the inductor 301. The autotransformer has only one winding with two winding sections 401a and 401b. The first winding section 401a is connected in the class E converter and performs the same function as the inductance 301 of the third embodiment. The second winding section 401b is connected to a voltage input of the ignition device 407 and serves to supply voltage to the ignition device 407. The center tap between the two winding sections 401a, 401b is connected to the node between the switch 402, the cathode of the diode 403 and the capacitor 404. The other voltage input of the ignition device is connected to the ground potential or to the negative DC voltage connection of the DC voltage source 400. The arrangement and function of the components 400, 402, 403, 404, 405, 406, 406a, 406b and LP4 are identical to the arrangement and function of the corresponding components 300, 302, 303, 304, 305, 306, 306a, 306b and LP3 of the third embodiment.

In Embodiment Examples 3 and 4, a symmetrical voltage doubler circuit or a cascade circuit for supplying power to the ignition device may be connected in front of the ignition device if the voltage generated by the class E converter is insufficient.

This in FIG. 5 Illustrated fifth exemplary embodiment of the ballast according to the invention is largely identical to the fourth embodiment. It shows in contrast to the fourth embodiment details of a pulse ignition device and has an additional capacitor 511, which is connected in parallel with the DC input of the class E converter. The capacitor 511 substantially prevents a current from being fed back to the DC power source 500 from the autotransformer 501. During the ignition phase of the high-pressure discharge lamp LP5, the primary winding 501a of the autotransformer 501 and the capacitor 504 form a series resonant circuit because the circuit is interrupted in parallel with the capacitor 504 consisting of the components 505, 506b and LP5 due to the non-conductive discharge path of the high-pressure discharge lamp LP5 , Since the voltage across the capacitor 504 during the ignition phase of the high-pressure discharge lamp LP5 in the blocking phase of the switch 502 can become greater than the supply voltage, there may be a temporary reversal of the current flow in the inductor 501a. The Impulszündvorrichtung consists of the ignition transformer 506, the ignition capacitor 507, the spark gap 508, the resistor 509 and the rectifier diode 510th The voltage input of the pulse igniter is via the winding 501b of the autotransformer with the node between the switch 502, the diode 503 and the capacitor 504th connected. The other voltage input, that is, the node between the ignition capacitor and the primary winding 506a of the ignition transformer 506 is connected to the ground potential or to the negative DC voltage terminal of the DC voltage source 500. The arrangement and function of the components 500, 501, 501a, 501b, 502, 503, 504, 505, 506, 506a, 506b and LP5 agrees with the arrangement and function of the corresponding components 400, 401, 401a, 401b, 402, 403 , 404, 405, 406, 406a, 406b and LP4 of the fourth embodiment. During the ignition phase of the high-pressure discharge lamp LP5, the ignition capacitor 507 is charged by means of the DC voltage source and the autotransformer 501 via the diode 510 and the resistor 509 to the breakdown voltage of the spark gap 508. Upon reaching the breakdown voltage, the capacitor 507 discharges intermittently across the spark gap 508, the discharge current flowing through the primary winding 506a of the ignition transformer 506. Due to the high gear ratio In the secondary winding 506b high-voltage pulses are induced for the electrode of the high-pressure discharge lamp LP5 which is connected to the secondary winding 506b and lead to the ignition of the gas discharge in the lamp LP5. During steady state lamp operation, the firing capacitor 507 is not charged sufficiently to initiate a spark gap 508 breakthrough.

This in FIG. 6 illustrated sixth embodiment of the ballast according to the invention is identical to the fifth embodiment. In particular, the arrangement and function of the components 600, 601, 601a, 601b, 602, 603, 604, 605, 606, 606a, 606b, 607, 608, 609, 610, 611 and LP6 are identical to the corresponding components 500, 501, 501a, 501b, 502, 503, 504, 505, 506, 506a, 506b, 507, 508, 509, 510, 511 and LP5 of the fifth embodiment. In contrast to the fifth exemplary embodiment, the sixth exemplary embodiment shows details of the controllable switch 602. The controllable switch 602 is embodied here as a field-effect transistor, in particular as a MOSFET. The antiparallel to its switching path connected diode 603 is already integrated as a body diode in the MOSFET 602 here. The MOSFET 602 has a parasitic capacitance 612, which results from the internal structure of the MOSFET in parallel with the drain-source path and at sufficiently high switching frequencies of the field effect transistor 602, that is, when operating the high-pressure discharge lamp LP6 with an alternating current of sufficiently high frequency. instead of the capacitor 604 can be used or must be taken into account in the dimensioning of the capacitor 604. The gate terminal of the field effect transistor 602 is connected to a control circuit 613 which serves to control the switching operations of the transistor 602. Table 1 shows the dimensioning of the individual components of the circuit arrangement according to the sixth exemplary embodiment of the invention.

During the ignition phase of the high pressure discharge lamp LP6, a DC voltage of 120 volts is provided by the DC power source 600 at the voltage input of the class E converter. The field effect transistor 602 is controlled by the control circuit 613 with a switching frequency of about 87 kilohertz and a Duty cycle of 0.5 switched. By means of the DC voltage source 600 and the autotransformer 601, the ignition capacitor 607 is charged to the breakdown voltage of the spark gap 608 via the diode 610 and the resistor 609. Upon reaching the breakdown voltage of the spark gap 608, the firing capacitor 607 is discharged intermittently via the primary winding 606a of the ignition transformer 606 and in its secondary winding 606b high voltage pulses of up to 40000 volts are induced to ignite the gas discharge in the high pressure discharge lamp. Immediately after the ignition of the gas discharge in the high pressure discharge lamp, the gas discharge is carried mainly by the xenon in the ionizable filling. During the transition from the ignition phase to the stationary lamp operating state, the other filling components, the metal halides, evaporate and contribute to the discharge and the emission of light. During this time, the supply voltage of 120 volts provided by the DC power source 600 is continuously reduced to a value of 70 volts so as to set the desired lamp power. The electrical properties, in particular the impedance of the high-pressure discharge lamp LP6, change considerably during the transition from the ignition phase to the stationary operating state. During the transition phase, the LP6 lamp is operated at increased power to ensure the fastest possible transition to steady-state lamp operation. After the onset of the lamp current, the switching frequency of the field effect transistor 602 is increased from approximately 87 kilohertz to approximately 360 kilohertz. After ignition of the gas discharge in the high-pressure discharge lamp LP6, the voltage drop across the ignition capacitor 607 no longer reaches the breakdown voltage of the spark gap 608. The secondary winding 606 of the ignition transformer 606b serves as resonance inductance 606b of the series resonant circuit of the class E converter after completion of the ignition phase. The high-pressure discharge lamp LP6 is a mercury-free metal halide high-pressure discharge lamp with an electrical power consumption of 30 watts and a burning voltage of about 30 volts. It serves as a motor vehicle headlight bulb. The DC voltage source 600 includes a step-up converter whose voltage output forms the DC output of the DC voltage source 600 and which supplies the supply voltage generated for the class E converter from the vehicle electrical system voltage of the motor vehicle.

This in FIG. 7 Illustrated seventh embodiment is largely identical to that in FIG. 2 illustrated second embodiment of the ballast according to the invention. In contrast to the second embodiment, the seventh embodiment also shows details of the pulse ignition device and the controllable switch. The controllable switch is designed here as a field-effect transistor, in particular as a MOSFET 1602. It is controlled by the control circuit 1613. In addition, the inductance at the positive DC voltage terminal of the DC voltage source 1600 is formed as autotransformer 1601 and connected in parallel to the DC voltage output of the DC voltage source 1600, a capacitor 1661 comparatively high capacity to prevent repercussions of the autotransformer 1601 on the DC voltage source 1600, as already in the fifth embodiment with reference to the corresponding Component 511 and the FIG. 5 was explained. The first winding section 1601a of the autotransformer 1601 is connected in the class E converter, so that the positive DC voltage terminal of the DC voltage source 1600 via the first winding section 1601 a and the drain-source path of the field effect transistor 1602 with the negative DC voltage terminal of the DC voltage source 1600 and connected to the ground potential. The second winding section 1602b of the autotransformer 1602 serves to supply power to the pulse ignition device. Antiparallel to the switching path, that is, to the drain-source path, the transistor 1602, a diode 1603 is connected, which is integrated here as a so-called body diode of the transistor 1602 in the transistor 1602. Parallel to the diode 1603 and also to the drain-source path of the transistor 1602, a capacitor 1604 is connected, in the dimensioning of the parasitic capacitance 1612 of the transistor 1602 is taken into account, as already in the sixth embodiment with reference to the transistor 602 and the FIG. 6 was explained. The parallel circuit to the capacitor 1604 consisting of the capacitance 1605 and the primary winding 1614a of the transformer 1614 is designed as a series resonant circuit. The secondary winding 1614b of the transformer 1614 supplies the connected thereto from the secondary winding 1606b of the ignition transformer 1606 and the high pressure discharge lamp LP16, or the electrical connections of the Hochdmckentladungslanipe, existing circuit with energy. For supplying power to the pulse ignition device, the second winding section 1601b of the autotransformer 1601 is connected to the node between the source terminal of the transistor 1602, the cathode of the diode 1603 and the capacitor 1604 and the capacitor 1605. By means of the winding section 1601b, the ignition capacitor 1607 is charged via the diode 1610 and the resistor 1609 to the breakdown voltage of the spark gap 1608 connected in parallel to the ignition capacitor 1607. Upon reaching the breakdown voltage of the spark gap 1608, the ignition capacitor 1607 discharges intermittently across the primary winding 1606a of the ignition transformer 1606. As a result, high-voltage pulses for igniting the gas discharge in the high-pressure discharge lamp are induced in the secondary winding 1606b of the ignition transformer 1606. The node between the firing capacitor 1607 and the primary winding 1606a of the ignition transformer 1606 is connected to the ground potential and to the negative terminal of the DC voltage source 1600, respectively. The transformer 1614 is for impedance matching of the high pressure discharge lamp LP16 to the class E converter and for galvanic isolation from the class E converter. The transformer 1614 can also be designed as an autotransformer, if a galvanic isolation is not required. A dimensioning of the components used is given in Table 2.

During the ignition phase of the high pressure discharge lamp LP 16, a DC voltage of 80 volts is provided by the DC power source 1600 at the voltage input of the class E converter. The field effect transistor 1602 is switched by the control circuit 1613 with a switching frequency of approximately 59 kilohertz and a duty cycle of 0.5. By means of the DC voltage source 1600 and the autotransformer 1601, the ignition capacitor 1607 is charged to the breakdown voltage of the spark gap 1608 via the diode 1610 and the resistor 1609. Upon reaching the breakdown voltage of the spark gap 1608, the firing capacitor 1607 is discharged intermittently across the primary winding 1606a of the ignition transformer 1606 and high voltage pulses in its secondary winding 1606b of up to 40000 volts for igniting the gas discharge in the high pressure discharge lamp. Immediately after the ignition of the gas discharge in the high-pressure discharge lamp LP 16, the gas discharge is carried mainly by the xenon in the ionizable filling. During the transition from the ignition phase to the stationary lamp operating state, the other filling components, the metal halides, evaporate and contribute to the discharge and the emission of light. During this time, the supply voltage of 80 volts provided by the DC power source 1600 is continuously reduced to a value of 40 volts so as to adjust the desired lamp power. The electrical properties, in particular the impedance of the high-pressure discharge lamp LP16, change considerably during the transition from the ignition phase to the stationary operating state. During the transition phase, the LP16 lamp is operated at increased power to ensure the fastest possible transition to steady-state lamp operation. After the lamp current has started, the switching frequency of the field effect transistor 1602 is increased from approximately 59 kilohertz to approximately 215 kilohertz. After ignition of the gas discharge in the high-pressure discharge lamp LP 16, the voltage drop across the ignition capacitor 1607 no longer reaches the breakdown voltage of the spark gap 1608.

The high-pressure discharge lamp LP 16 is a mercury-free metal halide high-pressure discharge lamp with an electrical power consumption of 30 watts and a burning voltage of about 30 volts, as already described in the sixth exemplary embodiment. It serves as a motor vehicle headlight bulb. The DC voltage source 1600 includes a step-up converter whose voltage output forms the DC voltage output of the DC voltage source 1600 and which generates the supply voltage for the class E converter from the vehicle electrical system voltage of the motor vehicle. However, the step-up converter can be dispensed with if the vehicle electrical system voltage is sufficiently high or if the transformer 1614 is suitably dimensioned.

In the FIG. 8 is as a curve A, the timing of the during the ignition phase of the high pressure discharge lamp LP6 from the control circuit 1613 to the gate of Transistor 1602 supplied substantially rectangular control voltage and curve B as the time course of the voltage drop across the switching path, that is, the drain-source path of the transistor 1602 shown. The zero level of the two voltage curves is indicated in each case by the number 1 or 2 with an adjoining horizontal arrow. The voltage across the drain-source path reaches a maximum value of 216 volts. Transistor 1602 is turned on and off only while the voltage drop across the drain-source path is zero. The duty cycle of the control voltage for the gate of the transistor 1602 is 0.5. The switching frequency of the transistor 1602 is 59 kilohertz.

The stationary operating state, after completion of the ignition phase of the high pressure discharge lamp LP6 is in FIG. 9 shown. The curve C shows the time profile of the supplied by the control circuit 1613 to the gate of the transistor 1602, substantially rectangular control voltage. The drain-source path of transistor 1602 is electrically conductive while the gate control voltage of transistor 1602 is greater than zero volts. The duty cycle of the control voltage is 0.5. The switching frequency of the transistor 1602 is 215 kilohertz. The curve F shows the corresponding temporal voltage curve over the drain-source path of the transistor 1602. The zero levels of the two voltage waveforms are indicated by the numeral 1 and 2, respectively, with a trailing horizontal arrow. The curve D shows the time profile of the lamp current and the curve E the time profile of the voltage across the discharge path of the high pressure discharge lamp LP6. The zero levels of curves D and E are indicated by the numeral 3 with the trailing horizontal arrow. The lamp current D and the lamp voltage E are in a very good approximation sinusoidal. The rms value of the lamp current is 932 mA and the rms value of the lamp voltage, that is, the burning voltage of the lamp LP6, is 32.7 volts. Lamp current D and lamp voltage E are in phase and their frequency is 215 kilohertz.

Further embodiments of the ballast according to the invention are in the FIGS. 10 to 17 shown. The embodiments according to the FIGS. 10 to 16 differ essentially only by the ignition device.

This in FIG. 10 illustrated eighth embodiment of the ballast according to the invention is largely identical to the first embodiment of the invention. In particular, the arrangement and function of the components 700, 701, 702, 703 and 704 of the eighth embodiment correspond to the arrangement and function of the components 100, 101, 102, 103 and 104 of the first embodiment. The diode 703 is designed as a Zener diode, wherein the breakdown voltage is chosen to be smaller than the maximum permissible voltage of the switch 702 and greater than the voltage occurring during operation at the switch 702. It serves as an overvoltage protection for the switch 702 during the onset of the lamp current. Connected in parallel with the capacitor 704 is a series resonant circuit consisting of the capacitance 705 and the inductance 706. In the series resonant circuit, the electrical connections of the high pressure discharge lamp LP7 are also connected. The ignition device is designed here as Gleichspannungszündvorrichtung 707. The DC output of the ignitor 707 is connected either directly in parallel with the resonant capacitance 705 or in parallel with the series connection of one or both components 701 and 706 with the resonant capacitance 705, as in FIG FIG. 10 indicated by dashed lines. During the ignition phase of the high-pressure discharge lamp LP7, a DC voltage is superimposed on the capacitor 705 or via the aforementioned series connection, which leads to the ignition of the gas discharge in the high-pressure discharge lamp LP7. After ignition of the gas discharge, the ignition device is deactivated.

This in FIG. 11 Illustrated ninth embodiment of the ballast according to the invention is identical to the eighth embodiment of the invention. Specifically, the arrangement and function of the components 800, 801, 802, 803, 804, 805 and 806 of the ninth embodiment correspond to the arrangement and function of the respective components 700, 701, 702, 703, 704, 705 and 706 of the eighth embodiment. The ninth embodiment shows details of the DC ignition ignition direction. The DC voltage ignition device comprises a controllable switch 809, a transformer 808 with primary winding 808a and oppositely wound secondary winding 808b and a diode 807. This ignition device is fed by the DC voltage source 800. The primary winding 808 a and the switching path of the switch 809 are connected in a circuit connected to the DC voltage terminals of the DC voltage source 800. The serially arranged secondary winding 808b and diode 807 are connected in parallel with the resonant capacitance 805 of the series resonant circuit of the class E converter. This ignition device operates essentially on the principle of a flyback converter. During the ignition phase of the high pressure discharge lamp LP8, the switch 809 is clocked at high frequency. In the conducting phase of switch 809, current flows through the primary winding 808a, resulting in the build-up of a magnetic field in the transformer 808. However, due to the polarity of the diode 807 and the sense of winding of the secondary winding 808b, no energy transfer from the transformer 808 to the resonant capacitance 805 occurs. In the blocking phase of switch 809, the energy stored in the magnetic field of transformer 808 is delivered to resonant capacitance 805. The voltage induced in the secondary winding 808b charges the resonant capacitance 805 via the diode 807 to the ignition voltage required to ignite the gas discharge in the lamp. At the end of the ignition phase, the ignition device is deactivated by switching off the switch 809. The secondary winding 808b is dimensioned to have a very large inductance, so that due to its high reactance in operation, after ignition of the gas discharge in the lamp, no appreciable current flows through it. If this dimensioning rule for the secondary winding 808b can not be fulfilled, an asymmetry of the lamp current caused by the diode 807 can be determined by means of the in FIG. 22 mapped Zener diode 810 whose Zener voltage is higher than the voltage applied during the lamp operation (after completion of the ignition phase) across the capacitor 805 voltage. As a result, no appreciable current flows through the secondary winding 808b during stationary lamp operation (after completion of the ignition phase). In all other details, the circuits are in accordance with the Figures 11 and 22 match.

This in FIG. 12 Illustrated tenth embodiment of the ballast according to the invention is identical to the eighth embodiment of the invention. Specifically, the arrangement and function of the components 900, 901, 902, 903, 904, 905 and 906 of the tenth embodiment correspond to the arrangement and function of the respective components 700, 701, 702, 703, 704, 705 and 706 of the eighth embodiment. The tenth embodiment shows details of the DC voltage ignition device. The DC voltage ignition device comprises a controllable switch 909, a transformer 908 with primary winding 908a and a co-wound secondary winding 908b and a diode 907. This ignition device is fed by the DC voltage source 900. The primary winding 908 a and the switching path of the switch 909 are connected in a circuit connected to the DC voltage terminals of the DC voltage source 900. The serially arranged secondary winding 908b and diode 907 are connected in parallel with the series connection of the resonance capacitance 905 and the resonance inductance 906 of the series resonant circuit of the class E converter. This ignition device operates during the ignition phase of the high pressure discharge lamp LP9 essentially according to the principle of a forward converter. In the conducting phase of the high frequency clocked switch 909, current flowing through the primary winding 908a of the transformer 908 induces an induction voltage in the co-wound secondary winding 908b. Induction voltage in secondary winding 908b drives a charging current into resonant capacitance 905 via diode 907 and resonant inductor 906. Resonant inductor 906 serves to limit the charging current of resonant capacitance 905 during the firing phase of high pressure discharge lamp LP9. Resonant capacitance 905 becomes high during the firing phase of high pressure discharge lamp LP9 charged to the required ignition voltage. The secondary winding 908b is dimensioned to have a very large inductance, so that due to its high reactance in operation, after ignition of the gas discharge in the lamp, no appreciable current flows through it. If this dimensioning rule for the secondary winding 908b can not be fulfilled, an asymmetry of the lamp current caused by the diode 907 can occur by means of the in FIG. 23 Zener diode 910 can be prevented whose Zener voltage is higher than that during lamp operation (after Termination of the ignition phase) across the capacitor 905 and the resonance inductance 906 pending voltage. As a result, no appreciable current flows through the secondary winding 908b during stationary lamp operation (after completion of the ignition phase). In all other details, the circuits are in accordance with the Figures 12 and 23 match.

The FIGS. 13 to 16 show embodiments of the ballast according to the invention with a resonance ignition device.

This in FIG. 13 illustrated eleventh embodiment of the ballast according to the invention is largely identical to the first embodiment of the invention. In particular, the arrangement and function of the components 1000, 1001, 1002, 1003 and 1004 of the eleventh embodiment correspond to the arrangement and function of the components 100, 101, 102, 103 and 104 of the first embodiment. Connected in parallel with the capacitor 1004 is a series resonant circuit consisting of the capacitances 1005, 1007 and the inductance 1006. In the series resonant circuit, the electrical connections of the high-pressure discharge lamp LP10 are also connected. The ignition device is designed here as a resonance ignition device. The capacitance 1007 is connected in parallel with the discharge path of the high-pressure discharge lamp LP10. During the ignition phase of the high pressure discharge lamp LP10, the switch 1002 is clocked at a frequency near the resonant frequency of the series resonant circuit 1005, 1006, 1007 of the class E converter, so that the required ignition voltage for the high pressure discharge lamp LP 10 is provided to the capacitor 1007 by resonant overshoot. After ignition of the gas discharge in the high pressure discharge lamp LP10, the switch 1002 is clocked at a frequency above the resonant frequency of the series resonant circuit consisting of the components 1005 and 1006, since after ignition of the gas discharge, the capacitance 1007 is short-circuited by the discharge path of the high pressure discharge lamp LP 10 ,

This in FIG. 14 illustrated twelfth embodiment of the ballast according to the invention is almost identical to the eleventh embodiment. Especially The arrangement and function of the components 1100, 1101, 1102, 1103, 1104, 1105 and 1106 of the twelfth embodiment correspond to the arrangement and function of the respective components 1000, 1001, 1002, 1003, 1004, 1005 and 1006 of the eleventh embodiment. In contrast to the eleventh embodiment, the series resonant circuit of the class E converter instead of the additional capacitance 1007 has an additional inductance 1107 which is connected in parallel to the discharge path of the high-pressure discharge lamp LP11. During the ignition phase of the high pressure discharge lamp LP11, the switch 1102 is clocked at frequency near the resonant frequency of the series resonant circuit 1105, 1106, 1107 of the class E converter, so that the required ignition voltage for the high pressure discharge lamp LP11 is provided by the resonant overshoot at the inductor 1107. After ignition of the gas discharge in the high-pressure discharge lamp LP 11, the switch 1102 is clocked at a frequency above the resonance frequency of the series resonant circuit consisting of the components 1105 and 1106.

This in FIG. 15 illustrated thirteenth embodiment of the ballast according to the invention is almost identical to the eleventh embodiment. Specifically, the arrangement and function of the components 1200, 1201, 1202, 1203, 1204, 1205, 1206 and 1207 of the thirteenth embodiment correspond to the arrangement and function of the corresponding components 1000, 1001, 1002, 1003, 1004, 1005, 1006 and 1007 of FIG Eleventh embodiment. The diode 1203 may be formed as a Zener diode to ensure overvoltage protection for the switch 1202. Unlike the eleventh embodiment, during the ignition phase of the high pressure discharge lamp LP12, the resonant circuit components 1206 and 1207 are excited by an external AC power source 1208 and not by the DC power source of the class E converter.

This in FIG. 16 illustrated fourteenth embodiment of the ballast according to the invention is almost identical to the twelfth embodiment. In particular, the arrangement and function of the components 1300, 1301, 1302, 1303, 1304, 1305, 1306 and 1307 of the fourteenth embodiment correspond to the arrangement and the function of the corresponding components 1100, 1101, 1102, 1103, 1104, 1105, 1106 and 1107 of the twelfth embodiment. In contrast to the twelfth embodiment, the resonant circuit components 1306 and 1307 are excited during the ignition phase of the high-pressure discharge lamp LP 13 by an external AC voltage source 1308 and not by the DC voltage source of the class E converter.

In FIG. 17 is schematically shown the circuit diagram of the ballast according to the fifteenth embodiment of the invention. This ballast has a DC input with two DC voltage terminals connected to the voltage output of a DC voltage source 1400. The positive DC voltage terminal is connected via the primary winding 1401 b of a transformer 1401 and the switching path of a controllable switch 1402 to the negative DC voltage terminal or to the internal circuit ground potential. Antiparallel to the switching path of the switch 1402, a diode 1403 is connected. Parallel to the switching path of the switch 1402 and also in parallel with the diode 1403, a capacitor 1404 is connected. In a parallel circuit to the capacitor 1404, the capacitor 1405 and the inductance 1406 are arranged. The capacitor 1405 and the inductor 1406 form a series resonant circuit. In the series resonant circuit, electrical connections for a high-pressure discharge lamp LP14 are arranged, so that when the lamp LP14 is connected, its discharge path is connected serially in the series resonant circuit. By means of the secondary winding 1401 a, an auxiliary voltage is generated which can be used, for example, to supply power to the control circuit of the switch 1402 or to supply power to one of the ignition devices described above.
In FIG. 18 a preferred embodiment of a high-pressure discharge lamp is shown, which is operated with the ballast according to the invention. This lamp is a mercury-free high-pressure discharge lamp with a power consumption of 25 watts to 35 watts, which is intended for use in a motor vehicle headlight. The discharge vessel 1 of this lamp has a tubular, cylindrical central portion 10, which consists of sapphire. The open ends of the section 10 are each through a ceramic plug 11 and 12 closed from polycrystalline alumina. The inner diameter of the circular cylindrical portion 10 is 1.5 millimeters. In the longitudinal axis of the discharge vessel 1, two electrodes 2, 3 are arranged so that their discharge-side ends protrude into the interior of the central, cylindrical portion 10 and have a spacing of 4.2 millimeters. The ionizable filling enclosed in the discharge vessel 1 consists of xenon with a cold filling pressure of 5000 hectopascal and a total of 4 milligrams of the iodides of sodium, dysprosium, holmium, thulium and thallium. The electrodes 2 and 3 are each connected via a power supply 4 or 5 with an electrical connection 16 or 17 of the lamp cap 15. The discharge vessel 1 is surrounded by a translucent outer bulb 14.

From the electrode gap, the inner diameter of the cylindrical portion 10 and the switching speed in the discharge medium, which is about 560 m / s, the acoustic resonance frequencies of the high-pressure discharge lamp can be calculated. The fundamental frequency of the longitudinal acoustic resonance is 70 kilohertz. The fundamental frequency of the azimuthal acoustic resonance is 230 kilohertz and the fundamental frequency of the radial acoustic resonance is 476 kilohertz. This means that the fundamental frequency of the aforementioned acoustic resonances in the discharge space would each be excited by an alternating current with a frequency that is half as large as that of the aforementioned resonances. Due to the large aspect ratio of 2.8 and the small inner diameter, the acoustic resonances are far apart. Between each of the aforementioned acoustic resonances is a resonance-free frequency range, in which a stable lamp operation without frequency modulation of the lamp AC current is possible. The switching frequencies of the MOSFET switch and AC frequencies of 360 kilohertz or 215 kilohertz disclosed in the sixth and seventh embodiments of the ballast according to the invention are thus in a resonance-free frequency range.

The FIG. 19 shows the in FIG. 18 Pictured high-pressure discharge lamp with a arranged in the lamp base 15 circuitry 18. This circuit 18 includes either the complete ballast of the high pressure discharge lamp including ignition device or only the ignition device of the high pressure discharge lamp.

In FIG. 20 the construction of a class E-converter according to the prior art is shown. The structure and function of this class E converter are on the Pages 271 to 273 of the book "Power electronics: converters, applications, and design" by the authors Ned Mohan, Tore M. Undeland and William P. Robbins, second edition 1995, John Wiley & Sons, Inc. described.

This class E converter has a DC input with two DC voltage terminals connected to the voltage output of a DC voltage source 1500. The positive DC voltage connection is connected via an inductance 1501 and the switching path of a controllable switch 1502 to the negative DC voltage connection or to the internal circuit ground potential. Antiparallel to the switching path of the switch 1502, a diode 1503 is connected. Parallel to the switching path of the switch 1502 and also in parallel with the diode 1503, a capacitor 1504 is connected. In a parallel circuit to the capacitor 1504, the capacitor 1505 and the inductor 1506 are arranged. The capacitor 1505 and the inductor 1506 are dimensioned so that the parallel circuit is a series resonant circuit. The load RL is connected in series in the series resonant circuit.

The protective diodes P6KE440 mentioned in Tables 1 and 2 can also be dispensed with.

In FIG. 21 is schematically illustrated the circuit diagram of the ballast according to the sixteenth embodiment of the invention. This ballast has a DC input with two DC voltage terminals +, - connected to the voltage output of a DC voltage source. The DC voltage source generates an input voltage of 42 volts for the class E converter on capacitor C4 connected in parallel with the voltage input of the class E converter. The positive DC voltage connection is via a first Winding portion of the autotransformer L2 and the switching path of the controllable field effect transistor T to the negative DC voltage terminal or connected to the internal circuit ground potential. The antiparallel to the switching path of the transistor T switched body diode of the MOSFET transistor T assumes the function of the diode 1503 of in FIG. 20 pictured class e-converter. Parallel to the switching path of the transistor T and also in parallel with its body diode, a capacitor C2 is connected. In a parallel circuit to the capacitor C2, the capacitor C5 and the primary winding n1 of a transformer Tr1 are arranged. The transformer Tr1 is for impedance matching of the lamp La to the class E convector. The secondary winding n2 of the transformer Tr1 is connected in series with the capacitor C1, the secondary winding of the ignition transformer L1, the discharge path of the high-pressure discharge lamp La and the resistor R3. Parallel to the series circuit consisting of the secondary winding of the ignition transformer L1 and the discharge path of the lamp La, a suppressor diode D5, for example a transil diode, is connected, which serves to limit the voltage.

Connected to the second winding section L2b of the autotransformer L2 is the pulse ignition device consisting of the diode D2, the resistor R2, the spark gap FS, the ignition capacitor C3 and the ignition transformer L1. The ignition capacitor C3 is connected in parallel with the series circuit consisting of the spark gap FS and the primary winding L1b of the ignition transformer L1. The voltage drop across the ignition capacitor C3 is monitored by the control circuit of the transistor T by means of the voltage divider resistors R4, R5. In addition, the control circuit of the transistor T also monitors the lamp current by means of the resistor R3. The control circuit of the transistor T consists of a logic part and driver circuits for the transistor T. In Table 3, a dimensioning of the components of the sixteenth embodiment is given. The lamp La is a mercury-free metal halide high-pressure discharge lamp with a discharge vessel made of quartz glass, which has an electrical power consumption of about 35 watts and a burning voltage of about 45 volts. This mercury-free metal halide high-pressure discharge lamp is by means of the class E converter operated with an AC voltage whose frequency is above the acoustic resonances of the lamp.

The class E converter is powered by the DC power source with an input voltage of 42 volts. During the ignition phase of the high-pressure discharge lamp La, the transistor T is operated by means of the control circuit with a switching frequency of 230 kilohertz. That is, the control circuit of the transistor T reduces the switching frequency of the transistor T from a value slightly above 230 kilohertz slowly until the required breakdown voltage of the spark gap FS has built up on the ignition capacitor C3, which means of the voltage divider R4, R5 from the control circuit of Transistor T is detected. When breakthrough of the spark gap FS, the ignition capacitor C3 discharges via the primary winding L1b of the ignition transformer L1. High-voltage pulses for igniting the gas discharge in the high-pressure discharge lamp La are generated in the secondary winding of the ignition transformer L1. After ignition of the gas discharge in the lamp La, a current flows through the discharge path of the high-pressure discharge lamp La. This lamp current is detected by means of the resistor R3 from the control circuit of the transistor T and the switching frequency of the transistor T is then increased abruptly to a value of 925 kilohertz. There is the so-called power start of the lamp La, during which the lamp La is operated with about three times the rated power to achieve a rapid evaporation of the metal halides. During power up, the switching frequency of the transistor T is increased to the steady state final value of 955 kilohertz to operate the lamp La at a power close to its rated power of 35 watts.

During lamp operation, the voltage drop across the resistor R3, which is proportional to the lamp current, is monitored by means of the control device of the transistor T. If this falls below a predetermined value, this is interpreted by the control circuit as a extinction of the lamp La and it is automatically set again the switching frequency of the transistor T to a value of about 230 kilohertz to re-initiate the ignition phase of the lamp La.

Alternatively, the extinction of the lamp La can also be detected by means of the voltage divider resistors R4, R5 by a voltage increase at the ignition capacitor C3. Alternatively, the ignition of the lamp La can also be detected by means of the voltage divider resistors R4, R5 in that the voltage drop across the ignition capacitor C3 remains well below the breakdown voltage of the spark gap FS over an extended period of time, for example 100 ms or 10 period lengths.

The invention is not limited to the embodiments explained in more detail above. For example, to better match the lamp to the class E converter, the capacitor 1504 or the respective capacitors 104, 204, 304, 404, 504, 604, 1604, 704, 804, 904, 1004, 1104, 1204, 1304, 1404 and C2 of the embodiments described above may be configured as capacitors with variable capacitance. The capacity can either be changed continuously between a minimum and maximum value, or switched between a few discrete, for example two, values. Thus, a high efficiency can be ensured despite a change in the lamp resistance, for example caused by the ignition of the gas discharge in the lamp or the evaporation of the metal halides in the discharge vessel of the lamp, with only a small variation of the switching frequency is required. In particular, in the embodiments with resonance ignition according to the FIGS. 13 and 14 For example, adjusting the resonant circuit by adjusting the capacitance of the capacitor 1004 or 1104 to a first value during ignition and switching to a second value after the ignition of the lamp is advantageous. This can be realized, for example, by designing the capacitor 1004 or 1104 as a parallel connection of two capacitors, one of which is activated or deactivated by means of a switching means.

As already explained, the ignition device 107 may include a pulse source providing one or a series of voltage pulses for igniting the gas discharge in the high pressure discharge lamp. This may also contain any AC voltage source, the longer lasting AC voltage instead of the pulse source provides. The frequency of this AC voltage is set so high that the capacitors 104, 105 and 204, 205 and 304, 305 and 404, 405 have a very low reactance at this frequency and can be regarded as a short circuit. Parallel to one of the two aforementioned capacitors or to both capacitors may be connected to the voltage limiting a suppressor diode, especially if the very low reactance can not be guaranteed.

As an alternative to the ignition devices explained above, a piezotransformer can also be used to generate the ignition voltage for the high-pressure discharge lamp. FIG. 24 shows an embodiment of the class E converter with a DC ignition in analogy to the embodiment of the FIG. 10 , Here, the class E converter is constituted by the components L200, S100, D100, C200, L100 and C100 having the same function as the corresponding components 701, 702, 703, 704, 705 and 706 in FIG FIG. 10 to have. According to the embodiment of FIG. 24 a piezo transformer PT is connected in parallel with the switch S100, which generates the high voltage for charging the capacitor C100 by means of the voltage doubler consisting of the diodes D700 and D800. The Zener diode D900 prevents a one-sided short circuit of the L100 and C100 resonant circuit during operation, and has the same function as the Zener diode 910 in FIG FIG. 23 , Thus, a single half-circuit switch S100 suffices for ignition and for operation of the high-pressure discharge lamp La. For example, by the according to the FIG. 23 required to generate the ignition voltage switch 909 can be saved. Due to the input capacitance of the piezo transformer PT, this can take over the function of the capacitor C200 partially or completely. The shutdown of the high voltage generation is done by changing the switching frequency of S100. It is sufficient a small change in the switching frequency, since piezotransformers have very narrow band resonances due to their high quality.

The ballast according to the invention is preferably used for operating a high-pressure discharge lamp for motor vehicle headlights, in particular a metal halide high-pressure discharge lamp with a translucent discharge vessel made of ceramic, as in FIGS. 18 and 19 shown as well as for example in the German patent application DE 102 42 740 or a metal halide high-pressure discharge lamp with a translucent quartz glass discharge vessel, as described, for example, in the patent application DE 103 12 290 is disclosed. Table 1: Dimensioning of the components according to the sixth embodiment of the invention module dimensioning Autotransformer 601 ETD29, N67 Primary winding 601a 49 turns, 300 μH Secondary winding 601 b 131 turns Field effect transistor 602 with integrated IRF830, International Rectifier Diode 603 Capacity 604 4.7 nF, 600V Capacity 605 1.5 nF, 1500V Transformer 606 150 μH, Primary winding 606a 1 turn Secondary winding 606b 40 turns Ignition capacitor 607 70 nF, 1000V Spark gap 608 800V, EPCOS FS08X-1JM Resistance 609 110 kOhm, 0.5W Diode 610 1500 V, two US1M in series, parallel to every US1M two P6KE440 in series Capacity 611 11 μF, electrolytic capacitor 10 μF / 100 V parallel to 1 μF / 630 V. film capacitor High pressure discharge lamp LP6 30 volts, 30 watts (nominal data) module dimensioning Auto-transformer 1601 ETD39, N67 Primary winding 1601a 39 turns, 300 μH Secondary winding 1601 b 190 turns Field effect transistor 1602 with integrated IRF740, International Rectifier Diode 1603 Capacity 1604 14.1 nF Capacity 1605 17.4 nF Capacity 1661 10 μF, 100V film capacitor Ignition transformer 1606 150 μH, Primary winding 1606a 1 turn Secondary winding 1606b 40 turns Ignition capacitor 1607 70 nF, 1000V Spark gap 1608 800V, EPCOS FS08X-1JM Resistance 1609 110 kOhm, 0.5W Diode 1610 1500 V, two US 1 M in row, parallel to every US1M two P6KE440 in series Transformer 1614 ETD29, N67 Primary winding 1614a 26 turns Secondary winding 1614b 52 turns High pressure discharge lamp LP 16 30 volts, 30 watts (nominal data) module dimensioning C1 200 pF C2 1.0 nF C3 70 nF C4 10 μF C5 680 nF D2 2000 V, twice US1M in series D5 2000 V, bidirectional voltage limitation four times P6KE520C in series FS 800V, EPCOS FS08X -1JM L1 Secondary winding 40 Wdg., 150 μH L1b Wdg. L2 10 weeks, EFD20, N59, 18 μH L2b 33 wdg. R2 10 kilo-ohms R3 0.5 ohms R4 10 megohms R5 47 kilo-ohms T IRFP460LC, 400V, 10A, 0.55 ohms (International Rectifier) TR1 nl = 8 cycles, n2 = 45 cycles, EFD25, N59

Claims (32)

1. Ballast for operation of at least one high-pressure discharge lamp, with the ballast having a voltage converter for production of an essentially sinusoidal alternating current, the voltage converter being in the form of a Class E converter which has DC voltage inputs (+, -), characterized in that an inductance (101) and the switch path of a controllable switching means (102) are connected between the DC voltage inputs, and a diode (103) is arranged back-to-back in parallel with the switching path of the switching means (102), and a capacitance (104) is arranged in parallel with the switching path of the switching means (102) and in parallel with the diode (103), with the inductance (101) being of such a magnitude that it acts as a constant-current source, and a parallel circuit, which is in the form of a series resonant circuit (105, 106b), is provided for the capacitance (104), to which parallel circuit the high-pressure discharge lamp (LP1) to be operated is coupled, the current which flows in the closed state via the switching path of the switching means (102) and in the open state via the capacitance (104) being composed of a direct current and a sinusoidal alternating current, which is generated by the series resonant circuit (105, 106b).
2. Ballast according to Claim 1, characterized in that

   - the positive DC voltage input (+) is connected via the inductance (101) and the switching path of the switching means (102) to the negative DC voltage input (-) and to the earth potential, and

   - electrical connections are provided for at least one high-pressure discharge lamp (LP1), and are coupled to the series resonant circuit (105, 106b).
3. Ballast according to Claim 1 or 2, characterized in that the ballast has a starting apparatus (107) for starting a gas discharge in the high-pressure discharge lamp (LP1).
4. Ballast according to Claim 3, characterized in that the starting apparatus (107) is coupled to an inductance (301) in the Class E converter for its voltage supply.
5. Ballast according to Claim 3, characterized in that the starting apparatus is in the form of a pulse starting apparatus (107).
6. Ballast according to Claim 3, characterized in that the starting apparatus is in the form of a DC voltage starting apparatus (707).
7. Ballast according to Claim 3, characterized in that the starting apparatus is in the form of a resonant starting apparatus.
8. Ballast according to Claim 3, characterized in that the starting apparatus contains a piezo transformer (PT).
9. Ballast according to Claim 8, characterized in that the input or the primary of the piezo transformer (PT) is connected in parallel with the switch (S100) of the Class E converter.
10. Ballast according to Claim 4, characterized in that the inductance is in the form of an autotransformer (401).
11. Ballast according to Claim 5, characterized in that the secondary winding (306b) of the starting transformer (306) of the pulse starting apparatus (307) is in the form of a component of a series resonant circuit of the Class E converter.
12. Ballast according to Claim 6, characterized in that the DC voltage starting apparatus (707) is coupled to a capacitance (705) in a series resonant circuit of the Class E converter.
13. Ballast according to Claim 1 or 2, characterized in that a transformer (208) is provided for impedance matching of the at least one high-pressure discharge lamp (LP2).
14. Method for operation of at least one high-pressure discharge lamp by means of an essentially sinusoidal alternating current, with this alternating current being produced by means of a Class E converter characterized in that an inductance (101) and the switch path of a controllable switching means (102) are connected between the DC voltage inputs, and a diode (103) is arranged back-to-back in parallel with the switching path of the switching means (102), and a capacitance (104) is arranged in parallel with the switching path of the switching means (102) and in parallel with the diode (103), with the inductance (101) acting as a constant-current source, and a parallel circuit, which is in the form of a series resonant circuit (105, 106b), is provided for the capacitance (104), to which parallel circuit the high-pressure discharge lamp (LP1) to be operated is coupled, the current which flows in the closed state via the switching path of the switching means (102) and in the open state via the capacitance (104) being composed of a direct current and a sinusoidal alternating current, which is generated by the series resonant circuit.
15. Method according to Claim 14, characterized in that the frequency of the essentially sinusoidal alternating current is in a frequency range which is free of acoustic resonances of the high-pressure discharge lamp.
16. Method according to Claim 14, characterized in that the high-pressure discharge lamp is operated with an electrical power in the range from 25 watts to 35 watts.
17. Method according to Claim 14 or 15, characterized in that the at least one high-pressure discharge lamp is operated during steady-state lamp operation with a burning voltage of not more than 100 volts once the gas discharge has been started.
18. Method according to Claim 14, characterized in that high-voltage starting pulses are produced for the at least one high-pressure discharge lamp, in order to start a gas discharge in the at least one high-pressure discharge lamp by means of a pulse starting apparatus which is coupled to an inductance in the Class E converter.
19. Method according to Claim 14, characterized in that, during the starting phase of the at least one high-pressure discharge lamp, the switching means of the Class E converter is switched such that a resonant voltage peak is produced on the inductance which is arranged at the DC voltage input of the Class E converter.
20. Method according to Claim 14, characterized in that the power consumption of the at least one high-pressure discharge lamp is adjusted by variation of the supply voltage for the Class E converter.
21. Method according to Claim 14, characterized in that the power consumption of the at least one high-pressure discharge lamp is adjusted by varying the switching frequency of the switching means for the Class E converter.
22. Method according to Claim 14, characterized in that the switching frequency of the switch for the Class E converter is lower before the breakdown of the discharge gap in the high-pressure discharge lamp than during steady-state operation.
23. Lighting system having a high-pressure discharge lamp and having a ballast according to one or more of Claims 1 to 13, for operation of the high-pressure discharge lamp, with the high-pressure discharge lamp having a discharge vessel with electrodes (2, 3) arranged in it and with a filling, which can be ionized in order to produce a gas discharge.
24. Lighting system as claimed in Claim 23, characterized in that the inductance (106b) and the capacitance (105) in the series resonant circuit of the Class E converter are matched to the distance between the electrodes (2, 3) and to the geometry of the discharge vessel (1) such that the resonant frequency of the series resonant circuit is in a frequency range which is free of acoustic resonances of the high-pressure discharge lamp.
25. Lighting system according to Claim 24, characterized in that the discharge vessel (1) has a cylindrical geometry, at least in the area of the gas discharge.
26. Lighting system according to Claim 23 or 24, characterized in that the ballast has a starting apparatus for starting a gas discharge in the high-pressure discharge lamp.
27. Lighting system according to Claim 26, characterized in that the starting apparatus is in the form of a pulse starting apparatus, with the secondary winding of the starting transformer of the starting apparatus being arranged in the Class E converter.
28. Lighting system according to Claim 26 or 27, characterized in that the starting apparatus is arranged in the cap of the high-pressure discharge lamp.
29. Lighting system according to Claim 23, characterized in that the ballast is arranged in the cap of the high-pressure discharge lamp.
30. Lighting system according to Claim 23, characterized in that the high-pressure discharge lamp has a rating in the range from 25 watts to 35 watts.
31. Lighting system according to Claim 23, characterized in that the burning voltage of the high-pressure discharge lamp is not more than 100 volts.
32. Lighting system according to one or more of Claims 23 to 31, characterized in that the lighting system is a motor vehicle headlight.

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