The present invention relates to a compact 3-way
fluorescent lamp that is designed to serve as a replacement for a 3-way incandescent
bulb. This novel compact 3-way
fluorescent lamp uses only two fluorescent tubes, where one tube has twice the wattage rating of the smaller rated tube. The lower wattage unit is a single U-shaped tube and the higher wattage unit is comprised of a pair of U-shaped tubes, having a
cross connection at the base of the tubes, giving a continuous gas
discharge path through a first U-shaped tube, a cross connecting element, and a second U-shaped tube. Therefore, this lamp gives the appearance of a triple biaxial
fluorescent lamp having three U-shaped units, spaced 120 degrees apart, and mounted to the top surface of a
ballast housing cover. Two electronic ballasts ignite and operate the two lamp units-a low wattage
ballast operates the low wattage unit, the medium wattage
ballast operates the dual U-shaped medium wattage unit, and when both units are operational, the highest wattage level is attained. Each of the ballast circuits is optimized to give an enhanced
high voltage ignition, thereby eliminating the need for an auxiliary ignition
electrode. A pi-section EMI filter suppresses the
electromagnetic interference that emanates from the MOSFETs as a result of their switching.
Fire hazard protection is given by an internal
fusible link.