Fluorescent ballast topology usually includes line conditioning for CE and UL compliance, a power factor correction block including a boost converter to 380 V for universal input applications and a half bridge inverter. By varying the frequency of the inverter, the controller will preheat the filaments (high frequency), then ignite the tube (reducing the frequency). Once the tube is lit, varying the frequency will dim the light. The Atmel AT90PWMx microcontroller can be programmed to perform all these functions.
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