Circuit means for efficiently driving an electrodeless discharge lamp
First Claim
1. 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, an RF amplifier responsive to said oscillator output signal, and an induction coil and a capacitor connected in series and responsive to the output of said amplifier, said coil being positioned in close physical proximity to said medium in said envelope for coupling to said medium an electric field having a magnitude sufficient to initiate ionization of said medium and a magnetic field for maintaining said ionization, the improvement wherein:
- said amplifier is a Class D amplifier including first and second transistors connected in series and driven alternately on and off by said oscillator output signal, the junction between said transistors being coupled to said series connected induction coil and capacitor, there being no separate, discrete load circuit connected in the output circuit of said amplifier.
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Accused Products
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 CV2 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.
54 Citations
21 Claims
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1. 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, an RF amplifier responsive to said oscillator output signal, and an induction coil and a capacitor connected in series and responsive to the output of said amplifier, said coil being positioned in close physical proximity to said medium in said envelope for coupling to said medium an electric field having a magnitude sufficient to initiate ionization of said medium and a magnetic field for maintaining said ionization, the improvement wherein:
said amplifier is a Class D amplifier including first and second transistors connected in series and driven alternately on and off by said oscillator output signal, the junction between said transistors being coupled to said series connected induction coil and capacitor, there being no separate, discrete load circuit connected in the output circuit of said amplifier. - View Dependent Claims (2)
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3. 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, an RF amplifier responsive to said oscillator output signal, and an induction coil responsive to the output of said amplifier, said coil being positioned in close physical proximity to said medium in said envelope for coupling to said medium an electric field having a magnitude sufficient to initiate ionization of said medium and a magnetic field for maintaining said ionization, the improvement wherein:
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said amplifier is a Class D amplifier including first and second transistors connected in series and driven alternately on and off by said oscillator output signal, and further comprising; a filter network positioned between the junction between said transistors and said induction coil for presenting a low impedance to said given radio frequency and a higher impedance to all other frequencies. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. 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, an RF amplifier responsive to said oscillator output signal, and an induction coil responsive to the output of said amplifier, said coil being positioned in close physical proximity to said medium in said envelope for coupling to said medium an electric field having a magnitude sufficient to initiate ionization of said medium and a magnetic field for maintaining said ionization, the improvement wherein said amplifier is a Class D amplifier including first and second transistors connected in series and driven alternately on and off by said oscillator output signal, and further comprising:
a combination filter and matching network operatively coupled between the junction between said transistors and said induction coil for presenting a low impedance to said given radio frequency and a higher impedance to all other frequencies and for matching the impedance of the output of said RF amplifier to the reflected resistance of said discharge in said envelope. - View Dependent Claims (18, 19)
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20. A filter network comprising:
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a tuned circuit including an inductor and a capacitor tuned to a given frequency so as to present a low impedance to said given frequency and a higher impedance to all other frequencies, said inductor comprising a first coil wound on a toroidal magnetic core; and a second coil wound on said core in out-of-phase relationship with said first coil, a first end only of said second coil being connected to one end of said first coil, the length of said second coil being adjusted to form a parallel resonant circuit at any frequency less than the self resonant frequency of said first coil. - View Dependent Claims (21)
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Specification