Brightness controlled fluorescent lamp preheat circuitry - uses capacitor charging current as preheat current in filaments

摘要

The preheat circuit, is used for starting a brightness-controlled fluorescent lamp. It heats both electrodes without using preheat transformers. The circuit contains a capacitor which is charged during each half wave via both heating filaments. This charging current provides the preheating and is used as discharge voltage for the tube. The capacitor is connected in series with a resistor (or a PTC resistor) between the two heating filaments.