| 摘要 |
PROBLEM TO BE SOLVED: To completely melt fuses of a plurality of short-circuited discharge tubes in a resonant inverter of which the resonant circuit is composed of the plurality of tubes and reactors. SOLUTION: When a short circuit detecting circuit 30 detects a short circuit in any of the discharge tubes, the drive frequency of an inverter 10 is changed into a lower fusing frequency fERR, which can supply a current capable of melting the fuse of the short-circuited discharge tube. If any of the discharge tubes is short-circuited, an inverter output current IL is decreased, because a current flows through the short-circuited discharge tube and no resonance is produced, so that there is a possibility that the fuse may not be melted. However, by decreasing the drive frequency of the inverter 10, the inverter output current IL increases and is supplied to the fuse of the short-circuited discharge tube, thus completely melting the fuse. |
