| 摘要 |
PROBLEM TO BE SOLVED: To prevent a lighting circuit from being broken by the flow of an excessive lamp current at the time of an input voltage drop and also prevent a discharge lamp from being left not lit due to a lighting failure when an input voltage rises to start lighting in the case that a D.C.-D.C. converter and a D.C.-A.C. inverter are provided for the lighting circuit. SOLUTION: An input voltage from a D.C. power source 1 is boosted by a D.C. boosting circuit 2, then converted into an A.C. voltage by a D.C.-A.C. inverter 3, and supplied to a discharge lamp 5. When the input voltage drops and the discharge lamp 5 goes out at that time, the stop state of the circuit operation is maintained by outputting a set signal to a latch circuit 10, and thereafter, when the input voltage rises and reaches a starting voltage lower than a rated voltage, a reset signal is output to the latch circuit 10 and the maintenance of the stop state is thereby canceled to perform a lighting start operation. If the lighting operation fails at that time, the lighting start operation is performed again when the input voltage further rises and approaches the rated voltage. |
