Compensation circuit and method for cancelling noise coupled to touch sensing circuit

A compensation circuit for cancelling noise coupled to a touch sensing circuit, the compensation circuit comprising:

• a computing processor configured to average first digital codes to generate a first average digital code and average second digital codes to generate a second average digital code, wherein the second digital codes correspond to grayscale voltages provided from a source driver to pixels connected to a currently driven gate line, wherein the first digital codes correspond to grayscale voltages provided from the source driver to pixels connected to a previously driven gate line adjacent to the currently driven gate line;
• a digital-to-analog converter (DAC) coupled to the computing processor to convert the first average digital code into a first voltage and convert the second average digital code into a second voltage, thereby generating a compensation signal transiting from the second voltage to the first voltage;
• and
• a voltage-to-current converting circuit coupled to the DAC to convert a voltage transition of the compensation signal into a compensation current and apply the compensation current to an input terminal of the touch sensing circuit, wherein the voltage-to-current converting circuit comprises:
• a voltage-to-current converter coupled to the DAC to receive the compensation signal and convert the compensation signal into an instruction signal corresponding to the compensation current;
• a current source coupled between the voltage-to-current converter to receive the instruction signal and thus generate the compensation current applied to the input terminal of the touch sensing circuit;
• and
• a switch coupled to the current source and controlled to determine a duration that the compensation current is applied to the input terminal of the touch sensing circuit;
• wherein a product of the duration and the compensation current is equal to a product of a capacitance of a coupled capacitor and a difference between the second voltage and the first voltage, wherein the coupled capacitor is coupled between the input terminal of the touch sensing circuit and a voltage supply line of the pixels of a display panel.

A compensation method for cancelling noise coupled to a touch sensing circuit, the compensation method comprising:

• averaging first digital codes to generate a first average digital code and averaging second digital codes to generate a second average digital code, wherein the second digital codes correspond to grayscale voltages provided from a source driver to pixels connected to a currently driven gate line, wherein the first digital codes correspond to grayscale voltages provided from the source driver to pixels connected to a previously driven gate line adjacent to the currently driven gate line;
• converting the first average digital code into a first voltage and converting the second average digital code into a second voltage, thereby generating a compensation signal transiting from the second voltage to the first voltage;
• generating an inverse noise signal according to the compensation signal or converting a voltage transition of the compensation signal into a compensation current;
• and
• applying the inverse noise signal or the compensation current to an input terminal of the touch sensing circuit;
• wherein the inverse noise signal is applied to the input terminal of the touch sensing circuit through a compensation capacitor;
• wherein a product of a capacitance of the compensation capacitor and a voltage transition of the inverse noise signal is equal to a product of a capacitance of a coupled capacitor and a difference between the second voltage and the first voltage, wherein the coupled capacitor is coupled between the input terminal of the touch sensing circuit and a voltage supply line of the pixels of a display panel.