| 摘要 |
PURPOSE:To improve quality of a picture. CONSTITUTION:A detection output from an I-V converter 11 is compared with a set output from a volume control 4, and an output of a DC-DC converter 7 is controlled so that the current running in a cold cathode electric discharge tube 8 is set to a value determined by the volume control 4. The output of the DC-DC converter 7 is controlled by feedback control based on the detection output from the I-V converter 11. Generation of power source noise can be prevented by changing the output variation in the DC-DC converter 7, unlike in a PWM method. Since the output of the DC-DC converter 7 is controlled by the feedback control based on the detection output from the I-V converter 11, stable dimming control is carried out constantly without being affected by the variation in the impedance characteristic of each circuit element due to the change in the environmental temperature, and the quality of the picture is thus improved. |
