High pressure sodium lamp ballast circuit

摘要

A ballast circuit for limiting the kilovolt-ampere rating of a ballast required to operate a high pressure sodium lamp during starting, hot restart and lamp out conditions. The ballast circuit includes a voltage limiting or clamping circuit across the secondary of a ballast transformer which responds to the voltage level and the rate of change of voltage across the secondary to activate a switch during each half cycle that the lamp is not conducting current.