Compensating for touch-screen coupling through display electrode
A touch-screen display device comprises a series of column electrodes and a series of row electrodes, with an electronic display layer arranged behind the series of column electrodes and behind the series of row electrodes. The series of row electrodes crosses the series of column electrodes such that the electrical impedance at each crossing of a row and column electrode is responsive to the proximity of a touch input to that crossing. A row-drive circuit is configured to apply an excitation signal to a selected row electrode and to concurrently apply a compensation signal to one or more other row electrodes, the compensation signal being out of phase with respect to the excitation signal. A column-sense circuit is configured to sense a column signal from the series of column electrodes and to provide a corresponding column output.
1 . A touch-screen display device comprising:
a series of column electrodes;
a series of row electrodes crossing the series of column electrodes such that an electrical impedance at each crossing of a row and column electrode is responsive to proximity of a touch input to that crossing;
an electronic display layer having an insulated common electrode arranged behind the series of column electrodes and behind the series of row electrodes;
a row-drive circuit configured to apply an excitation signal to a selected row electrode of the series of row electrodes and to concurrently apply a non-zero compensation signal to one or more other row electrodes of the series of row electrodes, the compensation signal being out-of-phase with respect to the excitation signal; and
a column-sense circuit configured to sense a column signal from the series of column electrodes and to provide a corresponding column output,
wherein the row-drive circuit is further configured to iteratively update the selected row electrode, and wherein the compensation signal applied to the one or more other row electrodes, in combination with the excitation signal applied to the selected row electrode, brings the insulated common electrode to a ground potential recognized by the column-sense circuit.
2 . The touch-screen display device of claim 1 wherein the compensation signal is 180 degrees out-of-phase with respect to the excitation signal.
3 . The touch-screen display device of claim 1 wherein the touch-screen display device includes a capacitive touch sensor, and wherein the series of row electrodes comprises each row electrode of the capacitive touch sensor.
4 . The touch-screen display device of claim 1 wherein the touch-screen display device includes a capacitive touch sensor, wherein the series of row electrodes is one of a plurality of subsets of row electrodes of the capacitive touch sensor, wherein the excitation signal is a signal of an upper modulation frequency, and wherein the row-drive circuit is further configured to apply an excitation signal of a lower modulation frequency to a selected row electrode of at least one other subset of the row electrodes of the touch-screen display device.
5 . The touch-screen display device of claim 1 wherein the electronic display layer includes an insulated conductor, and wherein the insulated conductor capacitively couples the series of row electrodes to the series of column electrodes absent the touch input, thereby adding an undesired component to the column signal.
6 . The touch-screen display device of claim 5 wherein an amplitude of the compensation signal is A/P, where A is the amplitude of the excitation signal and P is the number of the other row electrodes in the series of row electrodes.
7 . The touch-screen display device of claim 5 wherein an amplitude of the compensation signal is determined dynamically via the column-sense circuit, by sensing a response to the touch input on the column signal.
8 . The touch-screen display device of claim 5 wherein the insulated conductor is within 50 microns of the nearer of the series of row electrodes and the series of column electrodes.
9 . The touch-screen display device of claim 5 wherein the undesired component varies in dependence on lifetime usage of the touch-screen display device.
10 . The touch-screen display device of claim 5 wherein the undesired component varies in dependence on a use condition of the touch-screen display device.
11 . The touch-screen display device of claim 1 wherein the electronic display layer includes an active-matrix organic light-emitting diode layer.
12 . A method to process touch input on a touch-screen display device having an insulated common electrode of an electronic display layer arranged behind a series of column electrodes and behind a series of row electrodes, the method comprising:
applying an excitation signal to a selected row electrode of the series of row electrodes;
concurrently applying a non-zero compensation signal to one or more other row electrodes of the series of row electrodes, wherein the compensation signal is out-of-phase with respect to the excitation signal, and wherein the compensation signal applied to the one or more other row electrodes, in combination with the excitation signal applied to the selected row electrode, brings the insulated common electrode to a ground potential recognized by a column-sense circuit;
sensing a column signal from the series of column electrodes via the column-sense circuit, wherein an electrical impedance at each crossing of a row and column electrode is responsive to proximity of the touch input to that crossing; and
providing a column output corresponding to the sensed column signal.
13 . The method of claim 12 wherein the excitation signal is a first excitation signal and the column signal is a first column signal, the method further comprising:
intermittently applying a second excitation signal to the selected row electrode, where a modulation frequency of the second excitation signal is lower than a modulation frequency of the first excitation signal; and
intermittently sensing a second column signal from the series of column electrodes,
wherein an amplitude of the compensation signal is varied based at least partly on the second column signal.
14 . The touch-screen display device of claim 1 wherein the row-drive circuit is configured to iteratively update the selected row electrode according to a predetermined sequence.