| 摘要 |
PURPOSE:To protect an element such as a switching transistor with an excellent follow up characteristic to overvoltage input such as a surge as well as to eliminate flickering of a discharge lamp at overvoltage input time. CONSTITUTION:A parallel circuit 81 of a resistance 79 and a switching element 80 is connected in series to a switching transistor 56, and an input voltage detecting circuit 59 is arranged to detect high voltage input to an inverter circuit 58. The switching element 80 is opened by an action of a switch control circuit 60 in response to high voltage detecting output from this detecting circuit 59, and a collector current of the switching transistor 56 is reduced by connecting the resistance 79 in series to the switching transistor 56. An element such as the switching transistor 56 is protected from overvoltage input by restraining an increase in voltage between an collector and an emittor of the switching transistor 56. |
