Patent ID: 6348769
Filing Date: 2002-02-19
Classification: H05B,Y10S

Abstract:
An electronic ballast for providing electrical energy to at least one fluorescent lamp having first and second electrical discharge filaments, each with a resistive-heating portion and a pair of electrical in leads, said ballast comprising:a pre-heating circuit having a first resonant frequency, coupled to pre-heat the filaments; an ignition driver circuit having a second resonant frequency, coupled to ignite an electrical discharge through a gas between the filaments; and power controller circuitry, which provides power to the pre-heating and ignition driver circuits in succession so as to ignite the at least one lamp by first providing power to the pre-heating circuit substantially at the first resonant frequency in a pre-heating phase and subsequently providing power to the ignition driver circuit substantially at the second resonant frequency in an ignition phase, such that the frequency at which power is provided from said first resonant frequency to said second resonant frequency is smoothly varied so as to avoid resonance of said pre-heating and ignition driver circuits simultaneously, thereby avoiding pre-ignition of the at least one lamp, wherein said pre-heating circuit is operated in a predetermined interval for heating the filaments.