EVLB001 Datasheet, PDF (3/35 Pages) ATMEL Corporation – Automatic microcontroller dimmable ballast

Section 1
Introduction
Efficient fluorescent lamps and magnetic ballasts have been the standard lighting fixture
in commercial and industrial lighting for many years. Several lamp types, rapid start,
high output, and others are available for cost effective and special applications. But
incandescent lamps, in spite of the poor light to power ratio, typically one fourth of fluo-
rescent, offer one feature - dimming - that hasn’t been available in fluorescent lamps
until now. Dimming allows the user to conserve electrical power under natural ambient
light or create effects to enhance mood or image presentation and projection for
example.
Typical rapid start fluorescent lamps have two pins at each end with a filament across
the pins. The lamp has argon gas under low pressure and a small amount of mercury in
the phosphor coated glass tube. As an AC voltage is applied at each end and the fila-
ments are heated, electrons are driven off the filaments that collide with mercury atoms
in the gas mixture. A mercury electron reaches a higher energy level then falls back to a
normal state releasing a photon of ultraviolet (UV) wavelength. This photon collides with
both argon assisting ionization and the phosphor coated glass tube. High voltage and
UV photons ionize the argon, increasing gas conduction and releasing more UV pho-
tons. UV photons collide with the phosphor atoms increasing their electron energy state
and releasing heat. Phosphor electron state decreases and releases a visible light pho-
ton. Different phosphor and gas materials can modify some of the lamp characteristics.
ATAVRFBKIT / EVLB001 User Guide
1-1
7597B–AVR–10/07