Touch sensing high-low driving scheme for in-cell touch LCD display
A capacitive sensing method comprising: driving a first excitation signal onto a sensor electrode, and driving a second excitation signal onto the embedded electrodes. Either the first or the second excitation signal has voltage oscillations of constant first amplitude, while the other has voltage oscillations of varying second amplitude. The second amplitude varies between a high amplitude value that is larger than the first amplitude by an amplitude difference and a low amplitude value that is smaller than the first amplitude by the same amplitude difference. The method further comprises using one or more integrators to integrate an electric current due to combined voltage oscillations of the first and the second excitation signals within an integration cycle, and generate an integrated signal for detecting a capacitive change on the sensor electrode; wherein the integration cycle comprises a plurality of voltage oscillations of the first and the second excitation signals.
1. A capacitive sensing apparatus for performing self-capacitive sensing, comprising:
one or more sensor electrodes;
one or more embedded electrodes;
a generator configured to:
generate a first excitation signal and a second excitation signal;
drive the first excitation signal onto at least one of the sensor electrodes; and
drive the second excitation signal onto the embedded electrodes;
wherein the first excitation signal and the second excitation signal are periodic waveform signals having alternating peaks and troughs of substantially same frequencies and phases;
wherein the second excitation signal has voltage oscillations of a constant first amplitude while the first excitation signal has voltage oscillations of a varying second amplitude;
wherein each voltage oscillation is a positive going pulse or a negative going pulse;
wherein the second amplitude varies between a high amplitude value that is larger than the first amplitude by an amplitude difference and a low amplitude value that is smaller than the first amplitude by the amplitude difference; and
wherein the voltage oscillations of the first excitation signal have repeated series of the high amplitude value, followed by the high amplitude value, followed by the low amplitude value, and lastly followed by the low amplitude value;
and
one or more integrators configured to:
integrate a first electric current due to combined voltage oscillations of the first excitation signal and the second excitation signal within a first integration cycle, wherein the first integration cycle comprises the voltage oscillations within periods of time when the first excitation signal is having the voltage oscillations of high amplitude value;
integrate a second electric current due to combined voltage oscillations of the first excitation signal and the second excitation signal within a second integration cycle, wherein the second integration cycle comprises the voltage oscillations within periods of time when the first excitation signal is having the voltage oscillations of low amplitude value; and
generate one or more first integrated signals for detecting a capacitive change on the sensor electrodes and one or more second integrated signals;
wherein the first integration cycle comprises a plurality of voltage oscillations of the first excitation signal and the second excitation signal; and
wherein when combining the first integrated signals and the second integrated signals, the amplitude differences within the first integration cycle and the second integration cycle cancel each other after the integration.
2. A capacitive sensing method for performing self-capacitive sensing, comprising:
generating a first excitation signal and a second excitation signal;
driving the first excitation signal onto one or more sensor electrodes;
driving the second excitation signal onto one or more embedded electrodes;
wherein the first excitation signal and the second excitation signal are periodic waveform signals having alternating peaks and troughs of substantially same frequencies and phases;
wherein the second excitation signal has voltage oscillations of a constant first amplitude while the first excitation signal has voltage oscillations of a varying second amplitude;
wherein each voltage oscillation is a positive going pulse or a negative going pulse; and
wherein the second amplitude varies between a high amplitude value that is larger than the first amplitude by an amplitude difference and a low amplitude value that is smaller than the first amplitude by the amplitude difference; and
wherein the voltage oscillations of the first excitation signal have repeated series of the high amplitude value, followed by the high amplitude value, followed by the low amplitude value, and lastly followed by the low amplitude value;
integrating a first electric current due to combined voltage oscillations of the first excitation signal and the second excitation signal within a first integration cycle, wherein the first integration cycle comprises the voltage oscillations within periods of time when the first excitation signal is having the voltage oscillations of high amplitude value;
integrating a second electric current due to combined voltage oscillations of the first excitation signal and the second excitation signal within a second integration cycle, wherein the second integration cycle comprises the voltage oscillations within periods of time when the first excitation signal is having the voltage oscillations of low amplitude value; and
generating one or more first integrated signals for detecting a capacitive change on the sensor electrodes and generating one or more second integrated signals;
wherein the first integration cycle comprises a plurality of voltage oscillations of the first excitation signal and the second excitation signal; and
wherein when combining the first integrated signals and the second integrated signals, the amplitude differences within the first integration cycle and the second integration cycle cancel each other after the integration.