| 摘要 |
<p>The invention relates to a circuit arrangement for operating a discharge lamp, comprising a DC-AC converter provided with a switching element for generating a current whose polarity changes with a frequency f, a current sensor (SE), a drive circuit (III) for generating a drive signal to make the switching elements alternately conducting with the frequency f, a measuring circuit (I) coupled to the current sensor and having at least one switching element for generating a control signal which is dependent on a phase difference between a voltage across the load circuit B and a current through the load circuit B and on a second signal which is a measure for a minimum required phase difference, and a control circuit (II) for effecting a change in an operating condition of the DC-AC converter, this change being dependent on the control signal. According to the invention, the change in the operating condition of the DC-AC converter is that the switching element is made non-conducting during the remainder of a period belonging to the frequency f of the switching element. It is made possible in this way that, even in the case of a comparatively quick change in the operating conditions, capacitive operation will take place for a very short duration only, or not at all. <IMAGE></p> |
