Actuating circuit for a liquid crystal display

• US 5,206,632 A
• Filed: 09/11/1990
• Issued: 04/27/1993
• Est. Priority Date: 09/11/1989
• Status: Expired due to Term

• Current Assignee: Deutsche Thomson-Brandt Gmbh (Vantiva SA)
• Original Assignee: Deutsche Thomson-Brandt Gmbh (Vantiva SA)
• Inventors: Maier, Michael, Benoit, Eric, Dupont, Antoine, Hepp, Bernard
• Primary Examiner(s): Weldon, Ulysses
• Application Number:
  US07/580,462
• Time in Patent Office: 959 Days
• Field of Search: 340/784, 340/805, 340/825, 340/79, 340/825.8, 350/332, 350/333
• US Class Current: 345/92
• CPC Class Codes: G09G 2310/0259 with use of an analog or digital ramp generator in the column driver or in the pixel circuit
• CPC Class Codes: G09G 2310/0297 Special arrangements with multiplexing or demultiplexing of display data in the drivers for data electrodes, in a pre-processing circuitry delivering display data to said drivers or in the matrix panel, e.g. multiplexing plural data signals to one D/A converter or demultiplexing the D/A converter output to multiple columns
• CPC Class Codes: G09G 2310/066 Waveforms comprising a gently increasing or decreasing portion, e.g. ramp
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3688 suitable for active matrices only
• CPC Class Codes: H03K 7/08 Duration or width modulation ; Duty cycle modulation
• CPC Class Codes: H03K 9/08 of duration- or width-mudulated pulses or of duty-cycle modulated pulses
• CPC Class Codes: H04N 3/127 using liquid crystals

Abstract

An actuation circuit for a liquid crystal display includes a plurality of pixel elements constructed in the form of a matrix of columns and rows and a plurality of column capacitors connected to respective columns of the liquid crystal display that can be charged to store a signal to be displayed. The activation circuit comprises a number of blocks which each comprise a separate group of the columns forming the matrix of pixel elements, a corresponding number of column capacitors, and a plurality of data lines. The individual data lines receive respective signals and are connected to the column capacitors. A switch device is connected to each respective block for successively switching between the number of blocks. The signal to be displayed is fed in parallel through the data lines of the columns of a first block to charge respective column capacitors of the first block and after the charging of the column capacitors in the first block, the input lines are switched by the switch device to the data lines of the columns of the next-following block.

Claims

1. An actuation circuit for a liquid crystal display, comprising:

a plurality of actuation lines arranged in columns and a plurality of selection lines arranged in rows intersecting the columns;

a matrix of pixel elements each being operatively connected at an intersection of the columns and rows of said actuation and selection lines, respectively, said columns of actuation lines being grouped in a number of separate blocks of actuation lines;

a plurality of column capacitors each coupled to a respective one of said actuation lines;

a plurality of data lines for receiving data signals and feeding the data signals in parallel to the actuation lines of a respective block of actuation lines;

a plurality of storage capacitor means each connected to an actuation line and coupled with a respective one of said data lines for intermediately storing data signals to be displayed;

first switch means coupled between said data lines and said plurality of storage capacitor means for successively switching data signals on said data lines to the respective storage capacitor means of one block of actuation lines and then to the respective storage capacitor means of a following block of actuation lines until all storage capacitor means are charged with data signals; and

second switch means coupled between the respective storage capacitor means and said column capacitors for charging all column capacitors simultaneously in parallel after all storage capacitor means of all blocks of actuation lines have been charged by data signals.

2. An actuation circuit as defined in claim 1, further comprising voltage/time conversion means, operatively connected to the output of each storage capacitor means, for converting the signal received by the storage capacitor means into a pulse width modulator signal which is fed to the respective column capacitor by way of said second switch means.

3. An actuation circuit as defined in claim 1, wherein the first switch means comprises a first transistor arrangement having a first transistor for each column of a block;

and each column of said actuation circuit further comprises second, third, fourth and fifth transistors, each transistor having a gate electrode and input and output electrodes, the output electrodes of said first transistor and said second transistor being connected together at a first connection point and one terminal of the storage capacitor means being connected to the first connection point;

the other terminal of the storage capacitor means being connected to a second connection point, and the input electrode of said third transistor and the gate electrode of said fourth transistor are connected to the second connection point; and

the output electrode of said third transistor and the input electrode of said fourth transistor are connected together at a third connection point which is coupled to the output electrode of the fifth transistor, the input electrode and gate electrode of the fifth transistor being connected to a supply voltage,

wherein the signal to be displayed is input to the input electrode of said first transistor of a block when the gate electrode of said first transistor receives a block switching signal turning that block on, and the signal to be displayed charges the storage capacitor means.

4. An actuation circuit as defined in claim 3, wherein the first transistor arrangement is a transistor.

5. An actuation circuit as defined in claim 3, wherein the transistors are FET transistors.

6. An actuation circuit as defined in claim 3, wherein the transistors are TFT transistors

7. An actuation circuit as defined in claim 3, wherein the fifth transistor has a channel which is selected to be as small as possible and the fourth transistor a channel which is selected to be as large as possible.

8. An actuation circuit as defined in claim 3, wherein, after charging the storage capacitor means, the first and third transistors are switched off and the reference voltage applied by the second transistor is a ramp voltage.

9. An actuation circuit as defined in claim 3, wherein the first transistor arrangement for each column of a block further comprises a sixth transistor having an output electrode coupled to the input electrode of the first transistor and an associated capacitor connected at one terminal to the output electrode of the sixth transistor, the other terminal of which being coupled to ground;

and during a charging period determined by the block switching signal, the signal to be displayed for each data line is fed block by block via the sixth transistor to the associated capacitor of each column; and

after the associated capacitors of each block have been charged block by block, the stored data are fed line by line to the input of the first transistor.

10. An actuation circuit as defined in claim 3, wherein the first transistor arrangement comprises a parallel circuit including a first branch comprising the first transistor, a sixth transistor having an output electrode coupled to the input electrode of the first transistor, and a first associated capacitor coupled between the sixth transistor and the input electrode of the first transistor, one terminal of the first associated capacitor being connected to the output electrode of the sixth transistor, the other terminal being connected to ground;

and a second branch including a seventh transistor, a second associated capacitor having one terminal connected to the output electrode of the seventh transistor, the other terminal being coupled to ground, and an eighth transistor having an input electrode coupled to the output electrode of said seventh transistor and connected to the one terminal of the second associated capacitor and an output electrode coupled to the output electrode of said first transistor,

wherein the gate electrodes of the first, sixth, seventh and eighth transistors are coupled to receive switching signals, and the signal to be displayed is input to the input electrodes of said sixth and seventh transistors, the first and second associated capacitors being respectively charged with the data signal when the sixth and seventh transistor respectively receive a switching signal, the first and second associated capacitors being respectively discharged to charge the storage capacitor means when the first and eighth transistors respectively receive a switching signal.

11. An actuation circuit as defined in claim 1, wherein said column capacitors comprise stray capacitances present in the respective columns of the matrix.