Importance

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Abstract

In an electrodeless discharge lamp of the type including an ionizable medium within a sealed envelope capable of emitting radiant energy when subjected to a radio frequency field, an oscillator for generating an output signal at a given radio frequency of 13.56 MHz, an RF amplifier responsive to the oscillator output signal, and an induction coil and a capacitor connected in series and responsive to the output of the amplifier, the coil being positioned in close physical proximity to the medium in the envelope for coupling to the medium an electric field having a magnitude sufficient to initiate ionization of the medium and a magnetic field for maintaining ionization, there is disclosed an improvement wherein a Class D amplifier drives the series connected coil and capacitor without a separate load circuit connected in the output circuit of the amplifier. A specially selected filter and matching network coupled between the Class D amplifier and the series connected coil and capacitor reduces CV.sup.2 f losses, filters the output of the Class D amplifier to minimize harmonics, and matches the output impedance of the amplifier to the input impedance of the discharge to set the desired light level. The filter and matching network include specially designed induction coils for reducing radio frequency interference. Elements of the filter and matching network are variable to adjust the light level output of the lamp.

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First Claim