| 摘要 |
PURPOSE:To ensure that two lamps forming backlight are stably lighted without either of them being turned off by controlling lighting of the lamps through detection of a lamp current after a delay time at which the two lamps are surely lighted. CONSTITUTION:If the voltage of a lamp current detecting resistance 4 does not exist when DC power is inputted, a control circuit 1 maximizes the ON ratio of a switching transistor(TR)Tr1 and a node (a) is kept at a maximum voltage determined by a Zener diode ZD, to ensure that backlights 13L1, BL2 are lighted. When a lamp current flows through the lamp current detecting resistance R4 via the TRTr 11, an N-type TRTr 12 is turned on, and a P-type TRTr 11 is also turned on, and after a delay time after which the lights BL1, BL2 are surely lighted the lamp current is detected by the resistance R4 and the circuit 1 performs steady-state operation control. Therefore, steady-state lighting of the two lights is ensured without either of the lights being turned off. |
