Operating circuit for a discharge lamp with preheatable electrodes
AssigneePatent-Treuhand Gesellschaft fur Elektrische Gluhlampen GmbH
InventorThomas Neidlinger
Life of this patent
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Abstract
The invention relates to a novel operating circuit for a discharge lamp, in the case of which the lamp electrodes are preheated by driving switching transistors of an oscillator circuit such that their frequencies are detuned with reference to the resonant frequency of the lamp circuit. The drive frequency is defined by an independent resonant circuit.
Claims15
An operating circuit for a discharge lamp with preheatable electrodes, which operating circuit has an oscillator circuit with at least one switching transistor for generating an output power at an RF frequency for the discharge lamp, to be connected to the oscillator circuit, by means of a switching operation corresponding to the RF frequency, the operating circuit being designed such that after the operating circuit has been started the RF frequency of the oscillator circuit is varied such that the discharge lamp does not initially ignite, but a preheating current for preheating the electrodes flows through the electrodes, and after a preheating time, the RF frequency being returned to an operating frequency in the vicinity of a resonant frequency of the oscillator circuit in order to ignite the discharge lamp, the RF frequency of the oscillator circuit being determined by at least one dedicated resonant circuit which is connected to a control electrode of the switching transistor, in order to apply control signals at the RF frequency determined by the resonant circuit to the control electrode, the variation in the RF frequency for preheating purposes being performed by a detuning of the natural frequency of the resonant circuit with reference to the resonant frequency of the oscillator circuit.
The operating circuit as claimed in one of the preceding claims, in which the oscillator circuit has MOSFETs as switching transistors.
The operating circuit as claimed in one of the preceding claims, in which the oscillator circuit is a bridge circuit, and the resonant circuit is situated between the control electrode and a bridge midpoint.
The operating circuit as claimed in one of the preceding claims, in which the resonant circuit is an LC resonant circuit.
The operating circuit as claimed in one of the preceding claims, in which detuning of the natural frequency of the resonant circuit is performed by switching a junction connected to a capacitance in the resonant circuit.
The operating circuit as claimed in one of the preceding claims, in which the preheating time is determined by a charging operation of a preheating capacitance.
Dependencies are inferred from the claim text.