Digital drive systems for TFT-LCDs generally require multi gray-scale voltage sources. This paper proposes a multi-gray-scale drive method with binary values using an alternating voltage drive method : in place of gray-scale voltage sources, gray-scale signals that are digital signals are input to the drivers. A gray-scale signal is the signal that has a duty ratio whose average value is equal to the gray-scale voltage in the conventional drive system. A drive composes waveforms whose average values correspond to the data by combining the gray-scale signals and outputs them via output buffers. As the gray-scale signals can be generated by the same ASIC generating control signals, the circuitry of the drive system can be greatly simplified. We have developed a 4-bit drive system by using this method and have applied it to mass-produced modules. We have also developed a prototype 6-bit drive system and have showed that this method is applicable to generating 64 gray scales.
