| 摘要 |
PROBLEM TO BE SOLVED: To provide a liquid crystal display having a brightness adjusting device in which the frequency of the dimming synchronization signal is synchronized with the frequency of the brightness adjusting pulse at a fixed magnification to prevent interference noise, while the duty ratio of the pulse is not changed even if the frequency of the dimming synchronization signal is changed, and the frequency of the brightness adjusting pulse may be changed under the control of a multiplication circuit. SOLUTION: The brightness adjusting device includes: a multiplication circuit, which multiplies a vertical signal by a predetermined multiplication ratio to output a multiplication signal; a differential circuit that distinguishes between different multiplication signals; a circuit of a serrated wave generator that charges/discharges a condenser according to a signal output from the differential circuit and generates a serrated wave having constant amplitude independently of a frequency of the multiplication signal; a circuit of a brightness adjusting voltage generator that generates a reference voltage to determine a pulse duty; and a comparator cicuit that outputs a pulse signal by comparing a voltage of the serrated wave with the brightness adjusting voltage. The circuit of the brightness adjusting voltage generator includes a circuit that outputs a variable voltage, and the multiplication circuit includes a circuit having a variable multiplication ratio. COPYRIGHT: (C)2008,JPO&INPIT |
