DIGITAL DRIVING CIRCUITS, METHODS AND SYSTEMS FOR LIQUID CRYSTAL DISPLAY DEVICES

• US 20130141416A1
• Filed: 01/31/2013
• Published: 06/06/2013
• Est. Priority Date: 01/14/2010
• Status: Active Grant

• Current Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Van Ess, David, Keeser, Christopher C., Wright, David G., Murphy, Robert L.
• Granted Patent: US 8,704,818 B2
• Time in Patent Office: Days
• US Class Current: 345/212
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2320/0204 Compensation of DC component across the pixels in flat panels
• CPC Class Codes: G09G 3/04 for presentation of a single character by selection from a plurality of characters, or by composing the character by combination of individual elements, e.g. segments using a combination of such display devices for composing words, rows or the like, in a frame with fixed character positions
• CPC Class Codes: G09G 3/18 using liquid crystals
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

A method may include generating display driver signals that vary between only two levels and applying the display driver signals to opposing electrodes of a display segment within a display device. The method varies a correlation between the display driver signals to select or de-select the display segment based on an average voltage magnitude across the display segment over a time period. The display segment is activated when the average voltage magnitude exceeds a threshold value.

Claims

1. A method, comprising:

generating display driver signals that vary between only two levels;

applying the display driver signals to opposing electrodes of a display segment within a display device; and

varying a correlation between the display driver signals to select or de-select the display segment based on an average voltage magnitude across the display segment over a time period, wherein the display segment is activated when the average voltage magnitude exceeds a threshold value.

2. The method of claim 1, wherein the varying the correlation between display driver signals comprises generating a plurality of common driver signals that each includes frames of N timeslots, including one selection time slot and N−

1 de-selection timeslots, the selection timeslot being different for each common driver signal.

3. The method of claim 2, wherein the varying the correlation between display driver signals comprises generating at least one segment driver signal having frames of N timeslots corresponding to the common driver signals, wherein the segment is activated when the average voltage magnitude between corresponding common and segment driver signals exceeds a voltage threshold in a timeslot.

4. The method of claim 2, further comprising:

repeating each common driver signal every frame; and

generating at least one segment driver signal having frames of N timeslots corresponding to the common driver signal, the segment driver signal varying a correlation to at least one common driver signals in response to display data.

7. The method of claim 1, wherein the varying the pulse density is performed in a second mode, and wherein the method further comprises:

varying a correlation between the display driver signals to select or de-select the display segment based on a second average voltage magnitude across the display segment over a second time period in a first mode, wherein the display segment is activated when the second average voltage magnitude exceeds a second threshold value; and

switching between the first mode and the second mode in response to a mode indication.

8. The method of claim 7, wherein the first mode is a low power mode and the second mode is a higher power mode.

9. The method of claim 7, further comprising:

generating a plurality of time division multiplexed common driver signals and segment driver signals that vary substantially between the two levels;

in the first mode, activating display segments by varying a correlation between common and segment driver signals connected to such display segments; and

in the second mode, activating display segments by at least varying voltage levels of a common driver signal as received by the display segments.

10. The method of claim 9, further comprising:

in the first mode,

generating common driver signals that vary according to a predetermined sequence; and

generating segment driver signals that selectively correlates with at least one common driver signal in response to display data to exceed a minimum average voltage over a time period, wherein

a display segment is activated or not activated depending upon whether a voltage exceeds exceed the minimum average voltage over the time period.

11. The method of claim 10, wherein the common and segment driver signals include frames, each having a plurality of timeslots, and the time period comprises one of the time slots.

12. The method of claim 9, further comprising:

in the second mode,

generating common driver signals having a variable pulse density, and

filtering the variable pulse density signals to generate the varying voltage levels received by the display segments.

13. The method of claim 12, wherein the filtering the variable pulse density signals comprises forming a frequency filter that includes at least a portion of the display device, wherein the display device is a liquid crystal display.

14. The method of claim 9, further comprising further varying a pulse density of at least the common driver signals or the segment driver signals in response to an intensity value.

5. A method comprising:

generating display driver signals that vary between only two levels;

applying the display driver signals to electrodes of display segments within a display device;

varying a pulse density of the display driver signals; and

filtering the display driver signals to provide voltage levels across the display segments that vary according to pulse density, wherein the display segment is activated when an average voltage magnitude across the display segment over a time period exceeds a threshold value.

6. The method of claim 5, wherein the filtering the display driver signals comprises filtering with a frequency filter that includes at least a portion of the display device, wherein the display device is a liquid crystal display device.

15. A system, comprising:

a plurality of programmable digital blocks to be coupled to display segments of a display device, wherein the plurality of programmable digital blocks are configured into the following circuits;

a first signal generator circuit that generates control signals that vary between substantially only two levels and have predetermined correlations with respect to one another; and

a selection driver circuit coupled to the first signal generator circuit, wherein the selection driver circuit comprises a first mode that selectively couples selected controls signals to common display connection points and couples selected control signals to segment connection points in response to display data, wherein one or more of the display segments, which are each connected between one of the common display connection points and one of the segment connection points, are activated when respective control signals are above a minimum correlation.

16. The system of claim 15, wherein the selection driver circuit comprises:

a common section that time division multiplexes the control signals to a plurality of common connection points in a predetermined sequence; and

a segment section that time division multiplexes the control signals to a plurality of common connection points in response to at least display data.

17. The system of claim 15, wherein the plurality of programmable digital blocks are further configured into the following circuits:

a second signal generator circuit that generates a plurality of intensity signals that substantially do not correlate with the control signals; and

an intensity varying circuit that logically combines the intensity signals with signals output from the selection driver circuit.

18. The system of claim 15, wherein the selection driver circuit has at least a second mode that generates at least one control signal having a predetermined frequency.

19. The system of claim 18, further comprising

a display structure coupled to the common and segment connection points having an inherent capacitance that forms at least a portion of a frequency filter, the predetermined frequency being outside a passband of the frequency filter.

20. The system of claim 15, wherein the display device is a liquid crystal display coupled to the common and segment connection points.