| 摘要 |
<P>PROBLEM TO BE SOLVED: To detect smoothed voltages at both potential sides with a simple circuit configuration to obtain detection voltages at both potential sides and a difference voltage between both the detected smoothed voltages through computational processing for more accurate determination of lifetime end stage. <P>SOLUTION: The voltages across a discharge lamp FL are rectified to the positive and negative potentials using diodes D11 and D12. The positive potential-side rectified voltage is smoothed by a capacitor C12, and is divided by voltage divider resistors R14 and R15 to be output to an output terminal P01, while the negative potential-side rectified voltage is smoothed by a capacitor C14, and the resulting smoothed voltage is placed into a positive pole state through voltage division using voltage divider resistors R16-R18 between the smoothed voltage and the positive supply voltage ei to be output to an output terminal P02. A microcomputer 12 converts the voltage input from the output terminal P02 to correspond to a variation range of the detection voltage for the voltage from the output terminal P01. The voltage on the output terminal P01 is compared with a threshold V1, and the output from the output terminal P02, that is, the voltage after conversion, is compared with a threshold V2, while a difference between both voltages is compared with a threshold V3. If any one of the voltages exceeds the threshold, this is determined to be a lifetime end stage. <P>COPYRIGHT: (C)2010,JPO&INPIT |
