| 摘要 |
PROBLEM TO BE SOLVED: To provide a miniaturized and inexpensive lighting system, while preventing a base part from having high temperature in the last stage of its life time. SOLUTION: A comparator CP1 in a disconnection detecting circuit 6 detects that a base part becomes high temperature by an over current at the last stage of a life time of a lamp 1, a thermal fuse TF is used, and no electric current passes through a preheating circuit of the lamp 1, by sensing that a secondary voltage of an electric current transformer CT becomes 0 volt and a voltage of a capacitor C3 becomes lower than a reference voltage Vref. A control circuit 5 receives an 'L' output from the comparator CP1 and stops driving switching elements Q1 , Q2 to switch the lamp 1 off. |
