Importance

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Abstract

An illumination control system for gas discharge lamps which can be dimmed is provided in which a central inverter produces sinusoidal output voltage at about 23 kHz. The amplitude of the inverter output is adjustable to dim the lamps. A transmission line consisting of spaced wires having respective thick insulation sheaths distributes the high frequency power to remotely located assemblies of ballasts and lamps. A high power factor rectifier network is disclosed for providing a d-c input to the inverter from the 50/60 Hz mains. Several ballasts are disclosed, which consist principally of circuits using passive linear components. Some of the ballasts disclosed are conjugate ballasts which are those made of complex conjugate impedances which resonate with or near the input power frequency. Some ballasts disclosed are non-linear when the lamp is out in order to limit the open circuit voltage. The ballasts disclosed all have the following characteristics: (a) good power factor (above 0.8) and include at least one capacitor and one inductor; (b) are dimmable by at least 50% by a variable amplitude input having a substantially continuous wave form; (c) use only two input wires; (d) operate at a relatively high frequency (at least an order of magnitude above line frequency); (e) a good current crest factor.

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First Claim