Sidebar 3: Electronic Circuitry Adds Efficiency
An electronic linear fluorescent dimming ballast changes the 60 cycle waveform from the power source into a high frequency AC waveform while also regulating the current flow. Constant current pulse width modulation is used for the dimming function, which is expressed as a factor (percentage) of relative lamp output, or power. The dimming range extends from full output (100%) to the lowest level, typically 1%. Full output, in turn, is based on the ballast factor (e.g. 0.88, 1.00 or 1.18). Generally, the change in light output — either raising or lowering — is not noticeable to the occupants. Interestingly, when fluorescent lamps are dimmed, the human eye may perceive a higher light level than is actually being produced, because of adaptation.