Using PSpice to determine lamp current variation due to electronic ballast component tolerances

This paper studies the relationship between component tolerance and: (1) total lamp current variation; and (2) lamp current imbalance between lamps on one ballast. PSpice simulator and a four-lamp fluorescent current-fed push pull inverter is used in the study. The concept of component quality level (CQL) is introduced. Components with different quality level and tolerance are selected and a normal distribution is assumed. The studies indicate that to meet lamp current tolerance specifications and to produce lowest cost products, it is not enough to just tighten the component tolerances. Both CQL and tolerance have to be considered.