Control circuit with protection circuit for discharge lamp

摘要

The supply circuit for a discharge lamp includes a protection against abnormalities i.e. to switch off the supply if there is a failure. To cover temporary abnormalities two protection circuits are connected in parallel. One circuit isolates the supply when the abnormality persists over a set period and the other circuit operates for short abnormalities, during which time the first circuit maintains the supply. The two systems provide protection without the whole circuit supply tripping out because of transient problems. The supply circuit has a constant voltage supply which is blocked when the two protection circuits identify a problem.