Systems and methods for driving a bi-stable display element

• US 20060066594A1
• Filed: 02/18/2005
• Published: 03/30/2006
• Est. Priority Date: 09/27/2004
• Status: Abandoned Application

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Inventors: Tyger, Karen
• Application Number:
  US11/062,143
• Publication Number:
  US 20060066594A1
• Time in Patent Office: Days
• US Class Current: 345/204
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G09G 2300/06 Passive matrix structure, i.e. with direct application of both column and row voltages to the light emitting or modulating elements, other than LCD or OLED
• CPC Class Codes: G09G 2310/0267 Details of drivers for scan electrodes, other than drivers for liquid crystal, plasma or OLED displays
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2310/0289 Details of voltage level shifters arranged for use in a driving circuit
• CPC Class Codes: G09G 2310/065 Waveforms comprising zero voltage phase or pause
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3466 based on interferometric effect

Abstract

Due to the bi-stable nature of interferometric modulator elements, the state of each modulator element may be held at either an actuated or a released state with a common voltage difference. Because modulator elements often require less time to change states than is allotted in a line time, power drawn by an array of modulator elements may be reduced by disabling one or both of a row and column voltage boost module, which are configured to amplify an input power source to a level that is suitable for driving modulator elements. If the column voltage is removed during the latter portion of a line time, for example, the row voltage is set to a level that is sufficient to maintain a voltage difference between the row voltage and the floating column voltage within a stability voltage range during the remainder of the line time.

Claims

1. A method of updating a display region, the display region comprising a plurality of modulator elements arranged in a row and column configuration, wherein the modulator elements each have an actuated and a released state that may be selected by a voltage difference between a row electrode and a column electrode that are electronically coupled to respective modulator elements, each of the modulator elements being configured to maintain the state of the modulator element when a voltage within a stability window is applied between the row electrode and the column electrode of the respective modulator element, wherein each row of the modulator element is allotted a line time for changing states of the modulator elements of the respective row, the method comprising:

generating at least one row voltage with a row level shifter;

generating at least one column voltage with a column level shifter;

applying at least one row voltage to a selected row of modulator elements;

applying at least one column voltage to selected columns of modulator elements according to a desired state for the modulator elements; and

disabling the column level shifter prior to the completion of the line time, wherein the state of the modulator elements in the selected row are maintained by a voltage difference between the row voltage and a reference voltage, wherein the voltage difference is within the stability window.

2. The method of claim 1, wherein the reference voltage is provided by a data enable module.

3. The method of claim 1, further comprising enabling the column level shifter at about a start of a next line time.

4. A display comprising:

a row booster configured to generate a row voltage;

a column booster configured to generate a column voltage;

an array comprising a plurality of modulator elements, each of the modulator elements being connected to a column electrode and a row electrode and being configured to be driven by the row voltage and the column voltage, wherein a state of the modulator elements in a respective row of the array may be modified during a line time in which the row voltage is connected to the respective row electrode; and

a disable module configured to disable one of the boosters during a portion of the line time.

5. The display of claim 4, wherein the disable module is configured to disable the column booster during the portion of the line time.

6. The display of claim 5, wherein the row booster remains active during the disable portion of the line time and provides a bias voltage on each of the row electrodes.

7. The display of claim 6, wherein the bias voltage is about 5 volts.

8. The display of claim 5, further comprising a data enable module configured to output a reference voltage to the column electrodes of the array during the portion of the line time.

9. The display of claim 4, wherein the disable module is configured to disable the row booster during the portion of the line time.

10. The display of claim 9, wherein the column booster remains active during the portion of the line time and provides a bias voltage on each of the column electrodes.

11. The display of claim 10, wherein the bias voltage is about 5 volts.

12. A method of reducing power consumption of a display driver configured to drive each of a plurality of modulator elements in an array of modulator elements, wherein the display driver comprises a level shifter configured to generate an amplified voltage for driving the modulator elements, the method comprising:

(a) selecting a set of the modulator elements to be refreshed;

(b) refreshing the selected set of modulator elements, wherein the amplified voltage is applied to certain of the selected set of modulator elements in order to change a state of the certain modulator elements;

(c) after refreshing the selected set of modulator elements, disabling the level shifter for a predetermined time;

(d) after the predetermined time, enabling the level shifter; and

(d) repeating steps (a)-(d).

13. The method of claim 12, wherein the set of modulator elements comprises a row of modulator elements.

14. The method of claim 12, wherein the set of modulator elements comprises a column of modulator elements.

15. The method of claim 12, wherein the predetermined time is substantially equal to a line time of the display driver minus a time required for changing states of any of the modulator elements.

16. The method of claim 12, wherein a time allotted for the step of refreshing is greater than a time required for any of the modulator elements to change states.

17. The method of claim 16, wherein the time allotted for the step of refreshing is about 10 milliseconds.

18. A display driver configured to drive each of a plurality of modulator elements in an array of modulator elements, the display driver comprising

a voltage level shifter;

and

means for disabling the voltage level shifter for a predetermined time after refreshing a selected set of modulator elements.

19. The display driver of claim 18, further comprising:

means for enabling the level shifter after the predetermined time.

20. A display comprising:

a row booster configured to generate a row voltage;

a column booster configured to generate a column voltage;

an array comprising a plurality of bi-stable display elements, each of the display elements being connected to a column electrode and a row electrode and being configured to be driven by the row voltage and the column voltage, wherein a state of the display elements in a respective row of the array may be modified during a line time in which the row voltage is connected to the respective row electrode; and

a disable module configured to disable one of the boosters during a portion of the line time.