Abstract: An electronic ballast for providing electrical energy to one or more fluorescent lamps having electrical discharge filaments. The ballast includes a pre-heating circuit having a first resonant frequency, coupled to pre-heat the filaments. An ignition driver circuit having a second resonant frequency is coupled to ignite an electrical discharge through a gas between the filaments. Power controller circuitry provides power to the pre-heating and ignition driver circuits in succession, so as to ignite the one or more lamps. The power controller circuitry first provides power to the pre-heating circuit substantially at the first resonant frequency and subsequently provides power to the ignition driver circuit substantially at the second resonant frequency, by a smooth operating frequency transition from pre-heating to ignition. The ballast also features a voltage-controlled pre-heating circuit, and circuit configuration capable of igniting the lamps even in the case where one or both of the filaments are broken.

Abstract: A ballast for providing electrical energy to one or more fluorescent bulbs having electrical discharge filaments. The ballast includes a pre-heating circuit having a first resonant frequency, coupled to pre-heat the filaments. An electron-discharge circuit having a second resonant frequency is coupled to ignite an electrical discharge through a gas between the filaments. Driver circuitry provides power to the pre-heating and electron-discharge circuits in succession, so as to ignite the one or more bulbs. The driver circuitry first provides power to the pre-heating circuit substantially at the first resonant frequency and subsequently provides power to the electron-discharge circuit substantially at the second resonant frequency.