| 摘要 |
PURPOSE:To prevent the generation of a beat stripe phenomenon by conducting a frequency control to dimming chopper oscillation so as to avoid beat frequency relation. CONSTITUTION:The oscillating frequency of a fluorescent lamp oscillation/drive circuit 5 is inputted, comparative operation with a dimming oscillating frequency is conducted, and a dimming oscillating frequency control never generating a disturbance corresponding to beat frequency relation on a display screen or in a high frequency signal system is conducted. In the chopper type dimming of a fluorescent lamp 7, the dimming frequency can be optionally set by a key input means 1, an optionally set data can be stored in and read from an nonvolatile memory 2, the fluorescent lamp oscillating frequency (inverter oscillating frequency) is detected, whether it has the beat relation with the dimming chopper frequency or not is judged, and frequency variable control to avoid the beat frequency relation is conducted to the dimming chopper oscillation, whereby the beat stripe phenomenon appearing on the display screen of a liquid crystal television and the like can be prevented. |
