Abstract: A circuit for igniting and operating a discharge lamp includes a DC-AC converter provided with a first branch coupled to a DC voltage source and including at least one switching element for generating an alternating current at a frequency f. A load branch is coupled to the first branch and includes inductive means, capacitive means, and an inductor for coupling the lamp to the load branch. A control circuit switches the switching element at the frequency f and includes a resonant circuit of a further inductor and a further capacitor. An ignition voltage limiter includes a second branch coupled to the resonant circuit and comprising a series arrangement of a frequency-dependent impedance and a semiconductor element of variable impedance as a function of its control electrode potential. A third branch is coupled to the load branch and to the control electrode of the semiconductor element for influencing the potential of the control electrode dependent upon the lamp voltage.

Abstract: A circuit arrangement for operating a discharge lamp by means of a high-frequency current includes a switching device for generating the high-frequency current from a supply voltage, a modulator for the substantially square-wave modulation of the amplitude of the high-frequency current at a modulation frequency f, and an apparatus (M) for limiting the interference with infrared systems caused by the discharge lamp. The limiting apparatus (M) comprise a circuit N for providing a gradual increase in the rate at which the amplitude of the high-frequency current decreases at the end of a square wave of the square-wave modulation. This provides a considerable reduction in the interference with infrared systems caused by a lamp operated by the circuit arrangement.

Abstract: A circuit for igniting and operating a discharge lamp includes a DC-AC converter provided with a first branch coupled to a DC voltage source and including at least one switching element for generating an alternating current at a frequency f. A load branch is coupled to the first branch A and includes inductive means (L), capacitive means, and an inductor for coupling the lamp to the load branch. A control circuit switches the switching element at the frequency f and includes a resonant circuit of a further inductor and a further capacitor. An ignition voltage limiter includes a second branch coupled to the resonant circuit and comprising a series arrangement of a frequency-dependent impedance and a semiconductor element of varible impedance as a function of its control electrodes potential at its control. A third branch is coupled to the load branch and to the control electrode of the semiconductor element for influencing the potential of the control electrode dependent upon the lamp voltage.

Abstract: A circuit arrangement for operating a low-pressure mercury discharge lamp by a high-frequency current which includes a DC component and a high-frequency AC component. The circuit arrangement has a switching device for generating the high-frequency AC component from a supply voltage, an asymmetry device for rendering a first amplitude of the high-frequency AC component in a first polarization direction and a second amplitude of the high-frequency AC component in a second polarization direction unequal to one another, and a DC device for generating the DC component. The polarity of the DC component coincides with the polarization direction of the greater of the two amplitudes. Thus, striations in a low-pressure mercury discharge lamp operated on the circuit arrangement can be rendered invisible over a wide range of powers consumed by the lamp.