| 摘要 |
PROBLEM TO BE SOLVED: To save electric power while reducing noise by generating random data on the basis of a supplied clock, comparing this data with a prescribed threshold, and controlling lighting of a back light on the basis of a comparing result. SOLUTION: When lighting a back light by applying variable voltage on the back light 11 by boosting the variable voltage Unreg inputted to a back light driving device 1 by a transformer 7, an electric current value of the back light 11 is detected by an electric current detecting circuit 12, and detecting data D1 is compared with random data D2 on the basis of a horizontal synchronizing signal Sp as a threshold. A pulse signal Sran is generated on the basis of a comparing result, and a voltage value applied on the back light 11 and the timing are set by this signal. Thus, the back. light 11 can be lighted in response to a fluctuation in the variable voltage Unreg, a specific interval of respective pulses of the horizontal synchronizing signal Sp is designed at random, and a peak value of a spectrum of the horizontal synchronizing signal Sp can be dispersed. |
