Solid state ballast for a 40W circular fluorescent lamp

A fluorescent lamp ballast with a switching circuit for 40W lamp wattage and 100V line voltage is described. The ballast is composed of a series choke and a perallel switching circuit which operates in every half cycle of a.c. voltage. Silicon controlled rectifiers, that cut off the current in a low level by the reverse gate cnrrent, are used in the switching circuit. The ballast consumes 15% less energy and is 50% lighter than conventional ballast.