| 摘要 |
PURPOSE:To enlarge the dimming range of the backlight of a liquid crystal display device. CONSTITUTION:A dimmer has an oscillating circuit portion 1 for generating alternating current A and a dimming portion 2 which interrupts the alternating current A in response to the supply of a dimming signal D generated by a dimming control signal C, to produce a pulse-modulated alternating current E of a variable pulse width and period. The dimming portion 2 includes a dimming control portion 24 which generates a period control signal CP and a duty control signal CD in response to the supply of the dimming control signal C; a dimming-signal generating portion 21 which generates pulse signals P whose pulse period is controlled by the period control signal CP; a duty cycle control portion 22 which controls the pulse width according to the duty cycle control signal CD and generates a dimming signal D synchronous with the pulse signal P; and a switching circuit 23 which interrupts the alternating current A according to the dimming signal D to generate a pulse-modulated alternating current E. |
