System for driving liquid crystal display device

• US 4,027,305 A
• Filed: 04/08/1975
• Issued: 05/31/1977
• Est. Priority Date: 08/09/1973
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kishimoto, Juji
• Primary Examiner(s): Trafton, David L.
• Application Number:
  US05/566,064
• Time in Patent Office: 784 Days
• Field of Search: 340/324 R, 340/336, 350/160 LC
• US Class Current: 345/54
• CPC Class Codes: G09G 3/18 using liquid crystals

Abstract

A liquid crystal display device is driven by alternating current applied thereto by a switching circuit comprising a group of MOS transistors. The transistors are switched in response to display signals applied to the respective gate electrodes by a control circuit such as the output circuitry of a computer.

Claims

1. A system for driving a liquid crystal display device comprising in combination:

a liquid crystal display device having a plurality of liquid crystal digit display units each comprising a common electrode, a plurality of display segments opposed to and spaced from said common electrode, and a liquid crystal material interposed between said common electrode and said plurality of display segments;

means for electrically connecting corresponding ones of said display segments in each of said liquid crystal digit display units;

a timing enable signal generator for generating signals to sequentially and cyclically drive the respective said common electrodes of said liquid crystal digit display units;

a code converter for producing signals to selectively drive said display segments;

a recirculating register adapted to be recirculated in one cycle period of said timing enable signal generator for providing numerical information to said code converter; and

means for altering polarities of the signals from said timing enable signal generator and of the signals from said code converter every integral multiple of one recirculating period of said recirculating register, said means including a polarity alternating pulse generator, a plurality of first groups of gating means to which are supplied the signals from said polarity altering pulse generator and the signals from said timing enable signal generator and from which output signals are respectively appled to said common electrodes of said digit display units, and a plurality of second groups of gating means to which are supplied the signals from said polarity altering pulse generator and the signals from said code converter and from which output signals are respectively applied to said display segments of said digit display units.

2. A system as defined in claim 1, wherein the system further comprises means for applying high frequency pulses sufficient to provide an erasing effect to all display units other than the said unit to which a said timing enable signal is being applied.

3. A system as defined in claim 2, further comprising means for providing said timing enable pulses at a level less than a peak value level of said high frequency pulses.

4. A system as defined in claim 1, wherein the system further comprises means for applying a DC voltage having a magnitude less than that required to provide a display effect to all display units other than that to which a said timing enable signal is being applied.

5. A system as defined in claim 1, wherein said first and second groups of gating means comprise MOS transistors.

6. A system as defined in claim 1, wherein each of said gating means includes input terminals for receiving said signals applied thereto, an output teminal, and at least one additional input terminal to which is applied a DC voltage having a magnitude less than required to provide a display effect to said digit display units.

7. A system as defined in claim 6, wherein each of said gating means includes a second additional input terminal to which is applied a DC voltage having a level different than that applied to said one terminal thereof.

8. A system for driving a liquid crystal display device comprising in combination:

a liquid crystal display device having a plurality of liquid crystal digit display units each comprising a common electrode, a plurality of display segments opposed to and spaced from said common electrode, and a liquid crystal material interposed between said common electrode and said plurality of display segments;

means for electrically connecting corresponding ones of said display segments in each of said liquid crystal digit display units;

a timing enable signal generator for generating signals to sequentially and cyclically drive the respective said common electrodes of said liquid crystal digit display units;

a code converter for producing signals to selectively drive said display segments;

a recirculating register adapted to be recirculated in one cycle period of said timing enable signal generator for providing numerical information to said code converter;

means for altering polarities of the signals from said timing enable signal generator and of the signals from said code converter every integral multiple of one recirculating period of said recirculating register, said means including a polarity alternating pulse generator, a plurality of first groups of gating means to which are supplied the signals from said polarity altering pulse generator and the signals from said timing enable signal generator and from which output signals are respectively applied to said common electrode of each of said digit display units, and a plurality of second groups of gating means to which are supplied the signals from said polarity altering pulse generator and the signals from said code converter and from which output signals are respectively applied to said display segments of each of said digit display units;

wherein each of said gating means comprises;

first and second pairs of MOS transistors having gate electrodes to which are applied the signals from said timing enable signal generator or the signals from said code converter, the MOS transistors of said first pair each having respective main electrodes connected to DC voltages having a magnitude less than that required to cause said digit display units to be displayed;

a third pair of MOS transistors having gate electrodes to which are applied the signals from said polarity altering pulse generator;

means for electrically connecting the other main electrode of one of said first pair MOS transistors with one of two main electrodes of one of said third pair of MOS transistors;

means for electrically connecting the other main electrode of said one of the third pair of MOS transistors with one of two main electrodes of the other of said third pair of MOS transistors;

means for electrically connecting the other main electrode of the other of said third pair of MOS transistors with one of the two main electrodes of one MOS transistor of the second pair;

means for electrically coupling the other main electrode of said one MOS transistor of the second pair to a reference potential;

means for electrically connecting the other main electrode of the other MOS transistor of said first pair with one of two main electrodes of the other of said second pair of MOS transistors;

means for electrically connecting the other main electrode of the other said second pair of MOS transistors with one main electrode of the other of said first pair of MOS transistors; and

means for electrically connecting said output terminal to a junction between the other main electrode of the other of said first pair of MOS transistors and one main electrode of the other of said second pair of MOS transistors.

9. A system for driving a liquid crystal display device comprising in combination:

a liquid crystal display device having a plurality of liquid crystal digit display units each comprising a common electrode, a plurality of display segments opposed to and spaced from said common electrode, and a liquid crystal material interposed between said common electrode and said plurality of display segments;

means for electrically connecting corresponding ones of said display segments in each of said liquid crystal digit display units;

a timing enable signal generator for generating signals to cyclically drive the respective said common electrodes of said liquid crystal digit display units;

a code converter for producing signals to selectively drive said display segments;

a register for providing numerical information to said code converter;

means for changing levels of the signals from said timing enable signal generator and of the signals from said code converter every integral multiple of one cycle period of said timing enable signal generator;

a plurality of first groups of gating means to which are supplied the signals from said signal level changing means and the signals from said timing enable signal generator and from which output signals are applied to said common electrode of each of said digit display units; and

a plurality of second groups of gating means to which are supplied the signals from said signal level changing means and the signals from said code converter and from which output signals are applied to said display segments of each of said digit display units;

wherein each of said gating means includes input terminals for receiving said respective signals, an output terminal, and at least one additional input terminal to which is applied a DC voltage having a magnitude less than that required to provide a display effect to said digit display units.

10. A system as defined in claim 9, wherein each of said gating means includes a second additional input terminal to which is applied a DC voltage having a level different than that applied to said one additional terminal thereof.