| 摘要 |
PURPOSE:To permit inverter output to be limited only for a discharge lamp nearing its end of life by preventing output of a life detection circuit from being inputted to an output limiting means, in response to output from a no-load detection circuit. CONSTITUTION:The voltage of a discharge lamp l1 increases at both ends of it as it is nearing the end of life, at which time the output of a life detection circuit 41 also increases. This also results in increased output of a no-load detection circuit 61 over that at the time of its normal activation, but not sufficiently enough to open a switching means S1. Thus, output from the circuit 41 is supplied to an abnormality discrimination circuit 5, the output of which is then routed to an oscillation control section 3, which limits the output of an inverter 1. When the discharge lamp l1 is placed in a no-load condition with the remaining discharge lamps ln being all kept ON normally, the output of the circuit 41 releases the means S1, checking the output of the circuit 41. This, in turn, cancels the output limit imposed on the inverter 1 by the control section 3. |
