Drive system for liquid crystal display device

A drive system for a matrix type liquid crystal display device having a plurality of segment electrodes positioned to define a plurality of display figures and first and second digit electrodes, with each of said first and second digit electrodes being common to all of said display figures, comprising:

• a periodic signal source providing a plurality of periodic signals of fixed frequency, each of said periodic signals being mutually different in frequency;
• a control circuit responsive to selected ones of said periodic signals for producing a control signal composed of a rectangular wave signal;
• means for supplying first, second and third reference voltages, with the difference in potential between said second and first reference voltages being greater than a threshold voltage level for excitation of said liquid crystal display device, and with the difference between said third and first reference voltages being less than said threshold voltage level;
• a digit signal generating circuit having a distribution circuit coupled to receive said first, second and third reference voltages and responsive to said control signal for alternately providing said first and second reference voltages at a first output terminal thereof and for alternately providing said first and third reference voltages at a second output terminal thereof, a switch control circuit responsive to selected ones of said periodic signals for producing control signals, and a plurality of switching elements comprising a first pair of switching elements each having an input terminal coupled to receive said first reference voltage and a control terminal coupled to receive a selected one of said control signals, a second pair of switching elements each having an input terminal coupled to said first output terminal of the distribution circuit, and a control terminal coupled to receive a selected one of said control signals, and a third pair of switching elements each having an input terminal coupled to said second output terminal of the distribution circuit and a control terminal coupled to receive a selected one of said control signals, with output terminals of a first one of said first pair of switching elements, a first one of said second pair of switching elements and a first one of said third pair of switching elements being connected in common to a first output terminal of said digit signal generating circuit for thereby producing a first digit signal, and a second one of said first pair of switching elements, a second one of said second pair of switching elements and a second one of said third pair of switching elements being connected in common to a second output terminal of said digit signal generating circuit, for thereby producing a second digit signal, with each of said first and second digit signals thereby comprising a square wave signal alternating between said first, second and third voltage levels in a predetermined sequence, said predetermined sequence being periodically repeated, and with the periodic repetitions of said predetermined sequence in said first and second digit signals differing in phase, said first and second digit signals being applied to said first and second digit electrodes respectively;
• a segment signal generating circuit composed of a display data source for producing a pair of display data signals, a first selector circuit responsive to selected ones of said periodic signals and to first, second, third and fourth combinations of voltage levels of said pair of display data signals for producing first, second, third and fourth output signals respectively, a gate circuit controlled by said control signal for selectively passing said selected ones of the periodic signals, and a second selector circuit responsive to said periodic signals passed by said gate circuit in conjunction with said first, second, third and fourth output signals of the first gate means for producing first, second, third and fourth segment signals respectively, each of said segment signals comprising a rectangular wave signal alternating between said first and third reference voltage levels in a periodically repeated sequence, with the periodic repetitions of said first, second, third and fourth segment signals being mutually different in phase;
• said segment signals being applied in common to a pair of segment electrodes of said liquid crystal display device comprising a first segment electrode disposed adjacent and opposite to said first digit electrode and a second segment electrode disposed adjacent and opposite to said second digit electrode, whereby first and second display segments corresponding to said first and second segment electrodes are both periodically excited by said first segment signal in conjunction with said digit signals, only said first display segment is periodically excited by said second segment signal in conjunction with said digit signals, and only said second display segment is periodically excited by said third segment signal in conjunction with said digit signals.

A drive system for a liquid crystal display device in which a plurality of digit electrodes and a plurality of segment electrodes are arrayed in a matrix configuration, comprising:

• a periodic signal source providing a plurality of periodic signals;
• a control circuit responsive to selected ones of said plurality of periodic signals to provide a control signal;
• a digit signal generating circuit including a distribution circuit responsive to said control signal and providing a plurality of reference voltages, a switch control circuit responsive to the other selected ones of said periodic signals to provide a plurality of switch control signals, and a plurality of switching elements responsive to said switch control signals and selected ones of said reference voltages to provide a plurality of digit drive signals to be applied to said digit electrodes, respectively, said digit drive signals being different in phase from one another and each having said reference voltages in a predetermined sequence;
• and
• a segment signal generating circuit composed of a display data source generating a plurality of display information signals, first selector circuit means responsive to said display information signals and first and second ones of said other selected ones of said periodic signals to select one of said display information signals and provide first output signals, gate circuit means responsive to said control signal and third and fourth ones of said other selected ones of said periodic signals to provide second output signals, and second selector circuit means responsive to said first output signals to select one of said third and fourth ones of said selected ones of said periodic signals and provide segment drive signals to be applied to said segment electrodes said segment drive signal being different in phase from one another.