Integrated Circuit Control for Two-Lamp Electronic Ballast

Circuitry is described for a solid-state, high-frequency fluorescent ballast designed to operate two F40 T-12 rapid-start lamps. The circuits are designed to be produced by hybrid integrated circuit (IC) technology. The signal components are produced on a single IC chip; the power transistors are attached to an alumina substrate. The initial IC version reduces the component count by about 50%. The cost of each IC in 500 K lots is $0.70, replacing discrete parts costing $2.25. Additional savings of more than $1.00 per unit are realized by the decreased assembly time and improved reliability of the ICs. The system performance (two-lamp F40) was compared to the discrete version of the ballast and to an efficient core-coil ballast and found to be 6% less and 20% more efficient, respectively. The decrease in efficiency relative to the discrete version of the ballast is due to retaining some power to the filament during operation in order to maintain normal lamp life.