Power-saving circuit and method for driving liquid crystal display

A power-saving column driver circuit for applying driving voltages to a plurality of columns in a liquid crystal display, the liquid crystal display including an array of pixels arranged in rows and columns, and the liquid crystal display including row driver circuitry for selecting at least one row in the pixel array during a row drive period, the row driver circuitry selecting all rows in the pixel array at least once during a display cycle, said column driver circuit comprising in combination:

• a. clocking means for providing a control signal switching between a first state and a second state during at least one row drive period of each display cycle;
• b. a plurality of analog voltage drivers each having an output terminal coupled to a column of the liquid crystal display, each of said plurality of analog voltage drivers providing an analog driving voltage to be applied to a given column of the liquid crystal display during a given row drive period for controlling the pixel located at the given column within the selected row and for establishing a desired gray shade at such pixel corresponding to said analog driving voltage, each such voltage driver having a control input for receiving the control signal and selectively disabling the output terminal of said analog voltage driver when the control signal is in its first state, and enabling the output terminal of said analog voltage driver when the control signal is in its second state;
• c. a plurality of transmission gates, each of such transmission gates having a control terminal coupled to said clocking means for receiving the control signal, each of such transmission gates having a column terminal coupled to one of the columns of the liquid crystal display, each of such transmission gates having a common terminal, each of such transmission gates electrically coupling the column terminal thereof to the common terminal thereof when the control signal is in the first state, and each of such transmission gates decoupling the column terminal thereof from the common terminal thereof when the control signal is in the second state;
• and
• d. a common node coupled to the common terminal of each of said plurality of transmission gates;
• e. said plurality of transmission gates electrically coupling each of the columns of the liquid crystal display to said common node when the control signal is in its first state, and said plurality of analog voltage drivers providing analog driving voltages to the columns when the control signal is in its second state.

A power-saving column driver circuit for applying driving voltages to a plurality of columns in a liquid crystal display, the liquid crystal display including an array of pixels arranged in rows and columns, and the liquid crystal display including row driver circuitry for selecting at least one row in the pixel array during a row drive period, the row driver circuitry selecting all rows in the pixel array at least once during a display cycle, said column driver circuit comprising in combination:

• a. first and second analog voltage drivers for providing first and second analog driving voltages to be applied to first and second columns, respectively, of the liquid crystal display during a given row drive period for controlling the pixels locate at said first and second columns within the selected row and for establishing a desired gray shade at such pixels corresponding to said first and second analog driving voltages;
• b. clocking means for providing a control signal switching between a first state and a second state during at least one row drive period of each display cycle;
• c. first and second multiplexers each having a control terminal coupled to said clocking means for receiving the control signal, said first and second multiplexers each having a column terminal coupled to said first and second columns, respectively, of the liquid crystal display, said first and second multiplexers each having an input terminal coupled to said first and second analog voltage drivers, respectively, for receiving the first and second analog driving voltages to be applied to said first and second columns, respectively, of the liquid crystal display during a given row drive period, and each of said first and second multiplexers having a common terminal, each of said first and second multiplexers electrically coupling the column terminal thereof to the common terminal thereof when the control signal is in the first state, and each of such multiplexers electrically coupling the column terminal thereof to the input terminal thereof when the control signal is in the second state;
• d. a common node coupled to the common terminal of each of said first and second multiplexers,
• e. said first and second multiplexers electrically coupling the first and second columns of the liquid crystal display to said common node when the control signal is in its first state, and said first and second multiplexers coupling said first and second analog driving voltages produced by said first and second analog voltage drivers to said first and second columns, respectively, when the control signal is in its second state.

A power-saving column driver circuit for applying driving voltages to a plurality of columns in a liquid crystal display, the liquid crystal display including an array of pixels arranged in rows and columns, and the liquid crystal display including row driver circuitry for selecting at least one row in the pixel array during a row drive period, the row driver circuitry selecting all rows in the pixel array at least once during a display cycle, said column driver circuit comprising in combination:

• a. clocking means for providing a control signal switching between a first state and a second state during at least one row drive period of each display cycle;
• b. first and second analog voltage drivers each having an output terminal coupled to first and second columns, respectively, of the liquid crystal display, said first and second analog voltage drivers providing first and second analog driving voltages to be applied to said first and second columns of the liquid crystal display during a given row drive period for controlling the pixels located at said first and second columns, respectively, within the selected row and for establishing a desired gray shade at such pixels corresponding to said first and second analog driving voltages, respectively, each such analog voltage driver having a control input for receiving the control signal and selectively disabling the output terminal of said analog voltage driver when the control signal is in its first state, and enabling the output terminal of said analog voltage driver when the control signal is in its second state;
• c. first and second transmission gates each having a control terminal coupled to said clocking means for receiving the control signal, said first and second transmission gates each having a column terminal coupled to said first and second columns, respectively, of the liquid crystal display, each of such transmission gates having a common terminal, each of such transmission gates electrically coupling the column terminal thereof to the common terminal thereof when the control signal is in the first state, and each of such transmission gates decoupling the column terminal thereof from the common terminal thereof when the control signal is in the second state;
• and
• d. a common node coupled to the common terminal of said first and second transmission gates;
• e. said first and second transmission gates electrically coupling said first and second columns of the liquid crystal display to said common node when the control signal is in its first state, and said first and second voltage drivers providing first and second analog driving voltages to said first and second columns, respectively, when the control signal is in its second state.

A method of driving columns in a liquid crystal display while conserving power, the liquid crystal display including an array of pixels arranged in rows and columns, the liquid crystal display including a backplane, said method including the steps of:

• a. applying a bias voltage to the backplane of the liquid crystal display;
• b. providing a first common node;
• c. temporarily electrically coupling at least first and second columns of the array to the first common node a first time;
• d. applying first and second driving voltages to the first and second columns, respectively, of the array, the first driving voltage being of a first polarity relative to the backplane bias voltage, and the second driving voltage being of a second opposing polarity relative to the backplane bias voltage;
• e. transferring the first and second driving voltages applied to the first and second columns, respectively, onto corresponding first and second pixels, respectively, of a first row of pixels within the array of pixels;
• f. decoupling the first row of pixels from the first and second columns;
• g. temporarily electrically coupling the first and second columns of the array to the first common node a second time;
• h. applying third and fourth driving voltages to the first and second columns, respectively, of the array, the third driving voltage being of the second polarity relative to the backplane bias voltage, and the fourth driving voltage being of the first polarity relative to the backplane bias voltage;
• i. transferring the third and fourth driving voltages applied to the first and second columns, respectively, onto corresponding first and second pixels, respectively, of a second row of pixels within the array of pixels;
• j. decoupling the second row of pixels from the first and second columns;
• and
• k. repeating steps c. through j. for remaining pairs of rows within the array.

A method of driving columns in a liquid crystal display while conserving power, the liquid crystal display including an array of pixels arranged in rows and columns, the rows of pixels being arranged in pairs of rows, said method including the steps of:

• a. providing a first common node;
• b. temporarily electrically coupling at least first and second columns of the array to the first common node a first time;
• c. applying first and second driving voltages to the first and second columns, respectively, of the array;
• d. transferring the first and second driving voltages applied to the first and second columns, respectively, onto corresponding first and second pixels, respectively, of a first row of pixels within the array of pixels;
• e. decoupling the first row of pixels from the first and second columns;
• f. temporarily electrically coupling the first and second columns of the array to the first common node a second time;
• g. applying third and fourth driving voltages to the first and second columns, respectively, of the array;
• h. transferring the third and fourth driving voltages applied to the first and second columns, respectively, onto corresponding first and second pixels, respectively, of a second row of pixels within the array of pixels, the second row being paired with the first row;
• i. decoupling the second row of pixels from the first and second columns;
• and
• j. repeating steps b. through i. for remaining pairs of rows within the array;
• k. the first driving voltage, second driving voltage, third driving voltage, and fourth driving voltage each being an analog voltage for allowing the first and second pixels within the first row and the first and second pixels in the second row to display varying shades of gray.