Electric lamp and discharge devices: systems – Surge generator or inductance in the supply circuit
Reexamination Certificate
2000-03-01
2001-02-27
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Surge generator or inductance in the supply circuit
C315S290000, C315S291000, C315S244000, C315S278000, C315S2090SC, C315SDIG005
Reexamination Certificate
active
06194844
ABSTRACT:
The invention relates to a circuit arrangement for operating at least one high-pressure discharge lamp and to an operating method for a high-pressure discharge lamp.
I. BACKGROUND OF THE INVENTION
A circuit arrangement of this type is disclosed for example in the international patent application with the publication number WO 98/18297. This laid-open specification describes a circuit arrangement for the high-frequency operation of a high-pressure discharge lamp, that is to say for operating the high-pressure discharge lamp on an alternating voltage at a frequency above 200 kHz and preferably even above 500 kHz. The circuit arrangement has a voltage converter which generates a high-frequency alternating voltage at its output. The output of this voltage converter is formed by the two secondary windings of a transformer. The first secondary winding is connected into a load circuit which is designed as a series resonant circuit and is provided with the lamp terminals, while the second secondary winding is connected to the voltage input of a starter. The starter is a pulse starter, which applies unipolar high-voltage pulses to the high-pressure discharge lamp during the starting phase by means of an auxiliary starting electrode. In the case of lamp operation with high alternating voltage frequencies of this type, it is difficult to generate the necessary starting voltage for the high-pressure discharge lamp with the aid of a Tesla transformer, since the secondary windings of the transformer must have only a low inductance at such high frequencies—because of their otherwise excessively high internal impedance and the inadequately low transfer of power which results from this.
II. SUMMARY OF THE INVENTION
The object of the invention is to provide a circuit arrangement for operating at least one high-pressure discharge lamp with a high-frequency alternating voltage, which has an improved starter for starting a gas discharge in the at least one high-pressure discharge lamp, and to specify an improved operating and starting method for a high-pressure discharge lamp fed with a high-frequency alternating voltage.
The circuit arrangement according to the invention has a voltage converter for generating a high-frequency alternating voltage at its alternating voltage output, a load circuit which is connected to the alternating voltage output and which has at least one lamp inductor, a coupling capacitor and terminals for at least one high-pressure discharge lamp, and a starter for starting a gas discharge in the at least one high-pressure discharge lamp, the starter being provided with a high-voltage source and a high-voltage DC output. The coupling capacitor is connected to the high-voltage DC output via a charging resistor. As a result of this measure, during the starting phase the coupling capacitor is charged with the high DC voltage generated by the starter and, during the starting phase, serves as a voltage source for the load circuit and in particular for the at least one high-pressure discharge lamp. After the gas discharge has been started in the at least one high-pressure discharge lamp, the coupling capacitor is discharged via the electrically conductive discharge path in the at least one high-pressure discharge lamp. The discharge current flowing via the at least one high-pressure discharge lamp from the coupling capacitor contributes significantly to the production and stabilization of the discharge arc in the at least one high-pressure discharge lamp. In particular, the discharge current flowing through the at least one high-pressure discharge lamp from the coupling capacitor shortens the transition time from the undesired glow discharge, which damages the lamp electrodes, to the arc discharge.
The high-voltage source of the starter is advantageously designed as a cascade circuit for voltage multiplication of the output voltage of the voltage converter, or as a secondary winding coupled inductively to the lamp inductor, possibly with a downstream cascade circuit for voltage multiplication. In order to prevent the voltage converter being destroyed by excessively high starting voltages, a voltage-limiting component is advantageously connected in parallel with the alternating voltage output of the voltage converter. The voltage-limiting components used are advantageously bidirectional diodes, for example Transil diodes, or varistors, because they can be loaded with high electrical outputs.
The load circuit of the voltage converter advantageously also has a resonance capacitor which, with the lamp inductor, forms a series resonant circuit. As a result, the method of resonance enhancement can also be used for providing the discharge arc transfer energy and for generating the operating voltage for the at least one high-pressure discharge lamp. In the particularly preferred exemplary embodiments, the resonance capacitor is connected in parallel with the series circuit comprising the coupling capacitor and the at least one high-pressure discharge lamp. As a result, the starting voltage for the at least one high-pressure discharge lamp is formed from the additive superimposition of the high DC voltage present across the coupling capacitor and the resonance-enhanced high-frequency alternating voltage from the voltage converter, which is present across the resonance capacitor.
The voltage converter is advantageously designed as a single-ended converter or as a push-pull converter, for example as a push-pull inverter. These voltage converters are particularly suitable for converting a comparatively low DC voltage of, for example, 12 V or 24 V, which is usual in motor vehicles, into a high-frequency alternating voltage having an amplitude of about 500 V and a frequency of more than 500 kHz.
REFERENCES:
patent: 4724360 (1988-02-01), Luursema
patent: 4893061 (1990-01-01), Linssen
patent: 5036256 (1991-07-01), Garrison et al.
patent: 5142203 (1992-08-01), Oda et al.
patent: 5821696 (1998-10-01), Fromm et al.
patent: 5990633 (1999-11-01), Hirschmann et al.
Hirschmann Guenther
Rupp Arnulf
Thiel Gerwin
Bessone Carlo S.
Patent-Treuhand-Gesellschaft Fuer Elektrische Gluehlampen MBH
Philogene Haissa
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