Claims
- 1. An electrode drive circuit for driving an electrode of a matrix liquid crystal display comprising:
- switching circuit means for developing a switching waveform having first, second and third voltage levels at an output thereof, said switching means having a first and second supply input terminal;
- power supply means for supplying power to said switching circuit means, said power supply means supplying a constant supply voltage across [to] said first and second supply input terminals of said switching circuit means;
- a circuit ground; and
- pulse voltage generator means, connected between said circuit ground and said first supply input terminals, for supplying a periodic voltage pulse waveform having a pulse voltage amplitude of Vm and for varying the voltage supplied to said switching circuit means with respect to said ground, thereby [vary] varying the voltage developed by said switching circuit means with respect to said ground.
- 2. The drive circuit of claim 1 wherein said constant supply voltage comprises a voltage Vb supplied across said first and second supply input terminals of said switching circuit means, said voltage Vb being substantially equal to said pulse voltage amplitude Vm of said pulse voltage generator means.
- 3. A selecting electrode drive circuit for a matrix liquid crystal display comprising:
- power supply means for supplying a constant power supply voltage across first and second power supply output terminals of said power supply means;
- a circuit ground;
- switching circuit means, having first and second power input terminals operatively connected to said first and second power supply output terminals, for developing an output voltage signal at least one output terminal of said switching means; and
- pulse generating means, operatively connected to one of said output supply terminals, for supplying reference voltage pulses to said first and second power supply output terminals and for varying the voltage level at each power supply output terminal with respect to ground, said reference voltage pulses having a voltage amplitude of Vm;
- said pulse generating means, in cooperation with said power supply means, providing first, second and third voltage levels with respect to ground to said first and second power input terminals of said switching circuit means;
- said switching circuit means including
- selecting means, operatively connected to said first and second power input terminals, for selecting one of said first or second power input terminals, said selection means timing the selection of one of said first or second input terminals so that a desired one of said first, second, or third voltage levels present at said selected power input terminal is provided to at least one of said output [terminal] terminals, [to develop] thereby enabling said output voltage signal to have at one of said three voltage levels as its amplitude.
- 4. The selecting electrode drive circuit as claimed in claim 3, wherein said selection means comprises:
- inverter means, having a positive power terminal, a negative power terminal, an output terminal and an input terminal, for providing said output voltage signal at said output terminal, said positive power terminal connected to said first power input terminal, said negative power terminal connected to said second power input terminal; and
- counter means, operatively connected to said in terminal of said inverter means, for providing a digital control signal, said output voltage signal being the voltage level present at said first power input terminal with respect to said circuit ground when said digital control signal is low and said output voltage signal being the voltage level present at said second power input terminal with respect to said circuit ground when said digital signal is high.
- 5. The selecting electrode drive circuit as claimed in claim 4, wherein said power supply means is a clamping circuit comprising:
- a capacitor connected in parallel to said first and second power input terminals, a first end of said capacitor being connected to said first power input terminal and a second end being connected to said second power input terminal; and
- a diode having a cathode and an anode, said cathode being connected to said circuit ground and said anode being connected to said second power input terminal.
- 6. The selecting electrode drive circuit as claimed in claim 4, wherein said power supply means is a clamping circuit comprising:
- a first capacitor, connected in series between said first power input terminal and said pulse generating means;
- a second capacitor, connected in series between said second power input terminal and said pulse generating means;
- a first diode having a first cathode and a first anode, said first cathode being connected to said circuit ground and said first anode being connected to said second power input terminal;
- a second diode having a second cathode and a second anode, said second anode being connected to said circuit ground and said second cathode being connected to said first power input terminal.
- 7. The selecting electrode drive circuit as claimed in claim 4, wherein said power supply means is a clamping circuit comprising:
- a first capacitor connected in parallel to said first and second input terminals;
- a transistor having a collector, base, and emitter, said collector connected to said second power input terminal of said switching circuit means and said emitter connected to said circuit ground;
- a second capacitor connected to said base of said transistor; and
- an inverter connected between said second capacitor and said pulse generating means.
- 8. The selecting electrode drive circuit as claimed in claim 4, wherein said power supply means is a clamping circuit comprising:
- a capacitor connected in parallel to said first and second input terminals of said switching circuit means;
- an inverter, having an input and output terminal, its input terminal connected to said circuit ground; and
- a field effect transistor having a source, gate, and drain, said source connected to said second power input terminal of said switching circuit means, said gate connected to the output terminal of said inverter, and said drain connected to said circuit ground.
- 9. A selecting electrode drive circuit for a matrix liquid crystal display comprising:
- a circuit ground;
- power supply means having first and second power supply terminals, operatively connected to said circuit ground, for supplying a constant power supply voltage across said first and second power supply terminals, said power supply means supplying to said first and second power supply terminals a first difference voltage being measured with respect to said first power supply terminal and said circuit ground and a second difference being measured with respect to said second power supply terminal and said circuit ground and supplying across said first and second power supply terminals a third difference voltage being measured with respect to said first and second power supply terminals;
- said power supply means varying said first difference voltage between two possible levels and varying said second difference voltage between two possible levels, said first and second difference voltages having a common difference voltage to collectively define three possible with respect to said circuit ground voltage levels, thereby supplying two of said three possible voltage levels to said first and second power supply terminals, respectively, while maintaining said third difference voltage constant across said first and second power supply terminals; and
- switching circuit means, having first and second input power terminals operatively connected to said first and second power supply terminals, for supplying only one desired voltage level, from said two voltage levels being supplied to said first and second input power terminals, to an output terminal to develop an output voltage signal, said output voltage signal having a voltage level equal to one of said three possible voltage levels being supplied to said power supply terminals.
- 10. The selecting electrode drive circuit as claimed in claim 9, wherein said switching circuit means comprises;
- selection means, operatively connected to said first and second power input terminals, for selecting one of said first or second power input terminals;
- said selection means including,
- inverter means, having a positive power terminal, a negative power terminal, an output terminal and an input terminal, for providing said output voltage signal at said output terminal, said positive power terminal connected to said first power input terminal, said negative power terminal connected to said second power input terminal, and
- counter means, operatively connected to said input terminal of said inverter means, for providing a digital control signal said output voltage signal being the voltage level present at said first power input terminal with respect to said circuit ground when said digital control signal is low and said output voltage signal being the voltage level present at said second power input terminal with respect to said circuit ground when said digital signal is high.
- 11. The selecting electrode drive circuit as claimed in claim 9, wherein said power supply means comprises:
- pulse generating means, operatively connected to one of said power supply terminals, for supplying reference voltage pulses to said first and second power supply terminals to vary the voltage level at each power supply terminal with respect to ground, said reference voltage pulses having a voltage amplitude of Vm.
- 12. The selecting electrode drive circuit as claimed in claim 11, wherein said power supply means further comprises:
- a clamping circuit;
- said clamping circuit including,
- a capacitor connected in parallel to said first and second power input terminals, a first end of said capacitor being connected to said first power input terminal and a second end being connected to said second power input terminal, and
- a diode having a cathode an anode, said cathode being connected to said circuit ground and said anode being connected to said second power input terminal.
- 13. The selecting electrode drive circuit as claimed in claim 11, wherein said power supply means further comprises:
- a clamping circuit;
- said clamping circuit including,
- a first capacitor, connected in series between said first power input terminal and said pulse generating means,
- a second capacitor, connected in series between said second power input terminal and said pulse generating means,
- a first diode having a first cathode and a first anode, said first cathode being connected to said circuit ground and said first anode being connected to said second power input terminal, and
- a second diode having a second cathode and a second anode; said second anode being connected to said circuit ground and said second cathode being connected to said first power input terminal.
- 14. The selecting electrode drive circuit as claimed in claim 11, wherein said power supply means further comprises:
- a clamping circuit;
- said clamping circuit including,
- a first capacitor connected in parallel to said first and second input terminals,
- a transistor having a collector, base, and emitter, said collector connected to said second power input terminal of said switching circuit means and said emitter connected to said circuit ground,
- a second capacitor connected to said base of said transistor, and
- an inverter connected between said second capacitor and said pulse generating means.
- 15. The selecting electrode drive circuit as claimed in claim 11, wherein said power supply means further comprises:
- a clamping circuit;
- said clamping circuit including,
- a capacitor connected in parallel to said first and second input terminals of said switching circuit means,
- an inverter, having an input and out terminal, its input terminal connected to said circuit ground, and
- a field effect transistor having a source, gate, and drain, said source connected to said second power input terminal of said switching circuit means, said gate connected to the output terminal of said inverter, and said drain connected to said circuit ground.
- 16. A method of developing a drive voltage for driving an electrode of a matrix liquid crystal display comprising the steps of:
- supplying a first voltage to a first power input terminal of a switching circuit;
- supplying a second voltage to a second power input terminal of the switching circuit;
- maintaining a constant voltage difference across the first and second power input terminals;
- varying said first and second voltages with respect to ground to make available three possible voltage levels at the first and second power input terminals;
- providing only two of said three possible voltage levels at the first and second power input terminals of the switching circuit;
- selecting a single desired voltage at each instant in time from the voltages provided at the first and second power input terminals of the switching circuit, said desired voltage having a voltage level equal to one of said three possible voltage levels; and
- outputting from the switching circuit a signal having said desired voltage selected at each instant in time to the electrode of the matrix liquid crystal display to aid the driving thereof.
- 17. The method as claimed in claim 16 wherein said three possible voltage levels have values Vm Volts, O volts, and -Vm volts.
- 18. A selecting electrode drive circuit for a matrix liquid crystal display comprising:
- power supply means for producing first, second and third voltages and for supplying only two of said first, second, and third voltages to first and second power supply terminals thereof at any instant of time and for maintaining a constant voltage difference across said first and second power supply terminals; and
- switching circuit means, having first and second power input terminals operatively connected to said first and second power supply terminals, for selecting one of said first or second power input terminals and for supplying the voltage present at said selected power input terminal to an output terminal to provide an output voltage signal having the voltage present at said selected power input terminal.
- 19. The switching electrode drive circuit as claimed in claim 18 further comprising:
- a circuit ground for grounding said power supply means;
- the voltage presented to said first and second power input terminals floating with respect to said circuit ground.
- 20. The selecting electrode drive circuit as claimed in claim 19 wherein said switching circuit means comprises:
- selection means, operatively connected to said first and second power input terminals, for selecting one of said first or second power input terminals;
- said selection means including,
- inverter means, having a positive power terminal, a negative power terminal, an output terminal and an input terminal, for providing said output voltage signal at said output terminal, said positive power terminal being connected to said first power input terminal, said negative power terminal being connected to said second power input terminal, and
- counter means, operatively connected to said input terminal of said inverter means, for providing a digital control signal, said output voltage signal being the voltage presents at said first power input terminal with respect to said circuit ground when said digital control signal is low and said output voltage signal being the voltage present at said second power input terminal with respect to said circuit ground when said digital signal is high.
- 21. The selecting electrode drive circuit as claimed in claim 19, wherein said power supply means comprises:
- pulse generating means, operatively connected to one of said power supply terminals, for supplying reference voltage pulses to said first and second power supply terminals to vary the voltage level at each power supply terminal with respect to ground, said reference voltage pulses having a voltage amplitude of Vm.
- 22. The selecting electrode drive circuit as claimed in claim 21, wherein said power supply means further comprises:
- a clamping circuit;
- said clamping circuit including,
- a capacitor connected in parallel to said first and second power input terminals, a first end of said capacitor being connected to said first power input terminal and a second end being connected to said second power input terminal, and
- a diode having a cathode and an anode, said cathode being connected to said circuit ground and said anode being connected to said second power input terminal.
- 23. The selecting electrode drive circuit as claimed in claim 21, wherein said power supply means further comprises:
- a clamping circuit;
- said clamping circuit including,
- a first capacitor, connected in series between said first power input terminal and said pulse generating means,
- a second capacitor, connected in series between said second power input terminal and said pulse generating means,
- a first diode having a first cathode and first anode, said first cathode being connected to said circuit ground and said first anode being connected to said second power input terminal, and
- a second diode having a second cathode and second anode, said second anode being connected to said circuit ground and said second cathode being connected to said first power input terminal.
- 24. The selecting electrode drive circuit as claimed in claim 21, wherein said power supply means further comprises:
- a clamping circuit;
- said clamping circuit including,
- a first capacitor connected in parallel to said first and second input terminals,
- a transistor having a collector, base, and emitter, said collector connected to said second power input terminal of said switching circuit means and said emitter connected to said circuit ground,
- a second capacitor connected to said base of said transistor, and
- an inverter connected between said second capacitor and said pulse generating means.
- 25. The selecting electrode drive circuit as claimed in claim 21, wherein said power supply means further comprises:
- a clamping circuit;
- said clamping circuit including,
- a capacitor connected in parallel to said first and second input terminals of said switching circuit means,
- an inverter, having an input and output terminal, its input terminal connected to said circuit ground, and
- a field effect transistor having a source, gate, and drain, said source connected to said second power input terminal of said switching circuit means, said gate connected to the output terminal of said inverter, and said drain connected to said circuit ground.
Priority Claims (1)
Number |
Date |
Country |
Kind |
59-105586 |
May 1984 |
JPX |
|
Parent Case Info
This application is a continuation of application Ser. No. 737,421 filed on May 24, 1985, now abandoned.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
4000412 |
Rosenthal et al. |
Dec 1976 |
|
4123671 |
Aihara et al. |
Oct 1978 |
|
4145872 |
Portmann |
Mar 1979 |
|
Continuations (1)
|
Number |
Date |
Country |
Parent |
737421 |
May 1985 |
|