Compact fluorescent light source and method of excitation thereof

Abstract

Method an apparatus for general illumination wherein high frequency power is capacitively coupled to a low pressure discharge. A discharge lamp includes an envelope which is typically pear-shaped with a re-entrant cavity. The lamp envelope encloses a fill material which forms during discharge a plasma which emits ultraviolet radiation and has an effective electrical impedance. The lamp envelope typically includes on its inner surface a phosphor coating. An outer conductor, typically a conductive mesh, is disposed around the outer surface of the lamp envelope. A solid or hollow inner conductor is disposed in the re-entrant cavity. The apparatus is configured so that the capacitive impedance associated with coupling of high frequency power from the conductors to the discharge is much less than the plasma impedance. Low capacitive impedance is achieved by utilizing high frequencies and conductors with large surface areas and by maintaining the conductors in close contact with the lamp envelope. Substantially all of the induced electric field is confined within the discharge lamp. The inner conductor can have a shiny surface which is operative to reflect emitted light back to and through the discharge lamp. A high frequency power source can be included in the apparatus.