Patent ID: 7157867
Filing Date: 2007-01-02
Classification: H01J,H05B,Y02B

Abstract:
1. An operating method for acoustic resonant operation of a metal halide lamp using a radio frequency carrier frequency which is frequency-modulated (FM) by means of a sweep signal and which is amplitude-modulated (AM) at the same time, with a fundamental frequency first of all being set for the AM signal, which is derived from an i th , preferably the second, longitudinal resonance, wherein at least the following steps are carried out successively after starting of the lamp and after waiting for a stabilization time: a) Preparation step: during this step, a first resonance of the impedance value (Z) of the lamp, that is to say (ZEXT b) Step 1: the measurement interval (MI) is passed through during this step; a family of characteristics is thus determined which is obtained by passing through different AM levels, which are changed in steps, in a maximum range (AMI)=5 to 45%, in particular 10 to 40%, with the measurement interval (MI) in each case always being passed through from top to bottom, that is to say from (SM) to (ST); c) Step 2: determination derived from the family of characteristics, of an optimum AM level (AMI)=(AMopt) by comparison of a change in the lamp impedance as a function of the frequency for various AM levels; determination of a maximum of a change in the lamp impedance for an associated value of (AMI) equal to (AMmd); definition of (AMopt) by the rule (AMopt)=(AMmd)+(W) where (W)=3 to 10%; d) Step 3: search for a frequency (FMmin) associated with (AMopt); e) Step 4: definition of the operating frequency (FMopt) by passing through a frequency interval (OPT) between (FMmin) and a value which is 20% of (FM