Lamp control and lamp switch circuit

Claim 1

A lamp switch circuit for minimizing effects of cataphoresis in long multi-vapor arc lamps comprising: a. a long multi-vapor arc lamp mounted for exposure; b. silicon controlled rectifier bridge means connected across said lamp for establishing polarity of current flow through said lamp; c. control circuit means for triggering said silicon controlled rectifier means on and off when cataphoresis effect causes said lamp light intensity to become imbalanced end-to-end, said silicon controlled rectifier bridge means comprises, i. first and second pairs of silicon controlled rectifiers connected in a bridge configuration across said lamp, said first pair of silicon controlled rectifiers for establishing polarity of current flow through said lamp in a first direction when triggered by said control circuit means, said second pair of silicon controlled rectifiers for establishing polarity of current flow through said lamp in a second direction when triggered by said control circuit means; ii. commutating means for preventing more than two silicon controlled rectifiers in said bridge from getting triggered on at the same time, said commutating means comprise first and second commutating compacitors, said first commutating compacitor wired between cathodes of said first pair of silicon controlled rectifiers, said second commutating compacitor wired between anodes of said second pair of silicon controlled rectifiers; and iii. current inhibiting means in series with said commutating means for pReventing a rapid high current flow.