| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a power supply wherein the end of life is decided appropriately regardless of the use environment. <P>SOLUTION: The power supply includes a DC power supply circuit, a resonance circuit to which a discharge lamp is connected, a switching circuit which outputs an AC power to the discharge lamp by switching connection of the DC power supply circuit and the resonance circuit periodically, and a control circuit which controls the switching circuit. The control circuit determines whether the resonance circuit is at the end of life or not based on the drop of a voltage value Vo2 from a design value Vo1 while the operating frequency f of the switching circuit has a prescribed value fo. Since it is determined whether the end of life has reached or not based on the impedance of the resonance circuit, the end of life is decided appropriately regardless of whether the circuit components deteriorate fast or slowly in the use environment, on contrary to a case where the end of life is decided when the operating time reaches a prescribed time. <P>COPYRIGHT: (C)2011,JPO&INPIT |
