| 摘要 |
PROBLEM TO BE SOLVED: To prevent rupture of a discharge lamp and break of a lighting circuit even if resistance element constituting a current sensor for detecting lamp current is short-circuited in a discharge lamp lighting device having a non- insulated type DC-DC converter. SOLUTION: A current sensor 16 detects current flowing through a switching element 7, between a terminal on the GND side of a switching element 7 and the GND side of a power source line. A peak value detecting circuit 17 detects a peak value of the detected current values with the current sensor 16 and holds it. A comparing circuit 18 compares the held peak value with a detected lamp current value. A level decision circuit 19 reduces supply power to a high- pressure discharge lamp 2 by a specified degree when difference between compared both values is larger than the specified degree. When the difference of both values compared with the comparing circuit 18 is enlarged to the specified degree exceeding the value obtained by reducing power supplying to the high- pressure discharge lamp 2, the high pressure discharge lamp 2 stops lighting. |
