Remote control of fluorescent lamp ballast using power flow interruption coding with means to maintain filament voltage substantially constant as the lamp voltage decreases

A dimmable fluorescent lamp ballast system comprising:

• means for providing a first AC voltage signal;
• means responsive to said first AC voltage signal for providing a DC voltage signal having a magnitude which is adjustable between first and second levels, said first level being higher than said second level;
• a fluorescent lamp having filament means associated therewith;
• first circuit means responsive to said first level DC voltage signal for generating a second AC voltage signal having a magnitude proportional to the magnitude of said first level DC voltage signal, said second AC voltage signal being coupled to said fluorescent lamp;
• and
• second circuit means responsive to said first level DC voltage signal for generating a third AC voltage signal having a magnitude proportional to the resonant frequency of said second circuit means, said third AC voltage signal being applied to said lamp filament means, the magnitude of said second AC voltage signal decreasing as said DC voltage signal is adjusted to said second level from said first level, the magnitude of said third AC voltage signal when said DC voltage signal attains said second level remaining at a value at least equal to its value when said DC voltage signal is at said first level.