Control circuit and noise removing method for touch screen

• US 10,296,137 B2
• Filed: 09/17/2013
• Issued: 05/21/2019
• Est. Priority Date: 09/17/2012
• Status: Active Grant

• Current Assignee: Silicon Works Co., Ltd.
• Original Assignee: Silicon Works Co., Ltd.
• Inventors: Yang, Jun Hyeok, Choi, Jung Min
• Primary Examiner(s): Boddie, William
• Assistant Examiner(s): Elnafia, Saifeldin E
• Application Number:
  US14/428,781
• Publication Number:
  US 20150277660A1
• Time in Patent Office: 2,072 Days
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06F 3/0488 using a touch-screen or digitiser, e.g. input of commands through traced gestures

Abstract

Disclosed are a control circuit and a noise removing method for a touch screen. The present invention includes technology for performing differential sensing on the outputs of two adjacent sensing lines of a touch screen panel and integrating a differential sensing signal to filter noises. The control circuit and noise filtering according to the present invention may remove the display noise, tri-wave lamp noise having a predetermined frequency, 60 Hz noise and charger noise caused by battery charging that might affect the two adjacent sensing lines.

Claims

1. A noise removal method of a control circuit for a touch screen, comprising:

a differential sensing signal generation step of periodically generating a differential sensing signal for sensing signals of two adjacent sensing lines of a touch screen panel;

a noise detection step of detecting a noise in the one or more sensing signals for each cycle;

a differential distribution voltage storage step of storing a first differential distribution voltage and a second differential distribution voltage by charge-distributing the differential sensing signal for each cycle, wherein if a noise is detected the second differential distribution voltage has the same voltage level as that of the first differential distribution voltage and if a noise is not detected the second differential distribution voltage has a voltage level averaged at a specific ratio of an average voltage level of a first differential distribution voltage prior to two cycles and a first differential distribution voltage in a previous cycle right before;

and

a signal processing step of performing integration for each cycle, comprising;

selecting the first differential distribution voltage corresponding to a cycle to which a sensing signal in which a noise is to be detected corresponds, if a noise is not detected, and performing integration on the selected first differential distribution voltage; and

if a noise is detected, selecting the second differential distribution voltage corresponding to the sensing signal of a cycle prior to the cycle to which the sensing signal of the detected noise corresponds, and performing integration on the second differential distribution voltage.

2. The noise removal method of claim 1, wherein:

a result of the determination of the detection of the noise in the noise detection step is provided at a point of time delayed by one cycle from a point of time at which the sensing signal determined to be detected the noise has been input,

the first differential distribution voltage is cyclically alternately stored in two delay elements in the differential distribution voltage storage step, and

the first differential distribution voltage in accordance with the cycle corresponding to the sensing signal determined to be detected the noise is selected for the integration in accordance with the signal processing step that the noise is not detected.

3. The noise removal method of claim 1, wherein:

a result of the determination of the detection of the noise in the noise detection step is provided at a point of time delayed by one cycle from a point of time at which the sensing signal determined to be detected the noise has been input,

the second differential distribution voltage is cyclically stored in at least three charging elements in the differential distribution voltage storage step, and

a second differential distribution voltage that belongs to the second differential distribution voltages stored in the at least three charging elements and that corresponds to the sensing signal of a cycle prior to the cycle corresponding to the sensing signal determined to be detected the noise is selected for the integration in accordance with the signal processing step that the noise is detected.

4. The noise removal method of claim 1, wherein:

a result of the determination of the detection of the noise in the noise detection step is provided at a point of time delayed by one cycle from a point of time at which the sensing signal determined to be detected the noise,

the charging of a delay element and a charge distribution for the delay element are alternately performed every cycle in the differential distribution voltage storage step, and

the second differential distribution voltages corresponding to an odd cycle and an even cycle are stored using the charge-distributed voltage.

5. The noise removal method of claim 4, wherein in the differential distribution voltage storage step, the charge distribution is blocked in accordance with the detection of the noise, and the second differential distribution voltages corresponding to the odd cycle and the even cycle are alternately selected for the integration in accordance with the signal processing step of detecting the noise.

6. The noise removal method of claim 1, wherein in the signal processing step, integration is performed in accordance with the differential sensing signals of at least two cycles.

7. A control circuit for a touch screen, comprising:

a differential sensing unit which periodically generates a differential sensing signal for sensing signals of two adjacent sensing lines of a touch screen panels;

a noise detection unit which cyclically detects a noise in at least one of the sensing signals;

a delay unit which comprises first and second delay elements, performs charging of the differential sensing signal and output of the charged differential sensing signal as a first differential distribution voltage on each of the first and the second delay elements, periodically alternately performs the charging and output of the differential sensing signal on the first and the second delay elements, and outputs the first differential distribution voltage when a noise is not detected in the sensing signal by the noise detection unit;

a storage unit which comprises a plurality of charging elements, sequentially performs charging of a second differential distribution voltage on the plurality of charging elements using a charge-distributed voltage according to the differential sensing signal periodically provided by the delay unit, selects the second differential distribution voltage that corresponds to the sensing signal of a cycle prior to a cycle to which a sensing signal of a detected noise corresponds to the detected noise in the sensing signal by the noise detection unit from the plurality of charging elements, and outputs the selected second differential distribution voltage, wherein if a noise is detected the second differential distribution voltage has the same voltage level as that of the first differential distribution voltage and if a noise is not detected the second differential distribution voltage has a voltage level averaged at a specific ratio of an average voltage level of a first differential distribution voltage prior to two cycles and a first differential distribution voltage in a previous cycle right before; and

an integration unit which integrates the first differential distribution voltage of the delay unit and the second differential distribution voltage of the storage unit.

8. The control circuit of claim 7, wherein the noise detection unit comprises:

a first circuit which determines that a noise is included in the at least one sensing signal if the at least one sensing signal exceeds an upper limit and a lower limit;

a second circuit which generates a pulse corresponding to a result of the determination of the noise and delays the pulse by one cycle; and

a third circuit which outputs first and second noise detection signals having opposite phases using the delayed pulse.

9. The control circuit of claim 7, wherein the delay unit comprises:

a first current path which comprises the first delay element;

a second current path which comprises the second delay element;

an amplifier which comprises an input terminal and an output terminal between which the first current path and the second current path are connected in parallel and outputs the differential sensing signal for charging to any one of the first current path and the second current path;

a first switching circuit which cyclically alternately outputs the charged differential sensing signal to the first current path and the second current path; and

a second switching circuit which outputs the differential sensing signal selected by the first switching circuit to the first differential distribution voltage when a noise is not detected in the sensing signal by the noise detection unit.

10. The control circuit of claim 9, wherein:

the storage unit comprises at least three charging elements,

the differential sensing signals periodically provided by the delay unit are sequentially stored in the at least three charging elements, and

the differential sensing signal that belongs to the second differential distribution voltages stored in the at least three charging elements when a noise is detected in the sensing signal by the noise detection unit and that corresponds to the sensing signal of a cycle prior to a cycle to which the sensing signal in which the noise is determined to be detected corresponds is output as the second differential distribution voltage.

11. The control circuit of claim 9, wherein:

the storage unit comprises a delay element,

the charging of the delay element and a charge distribution for the delay element are alternately performed every cycle, and

the second differential distribution voltages corresponding to an odd cycle and an even cycle are stored using the charge-distributed voltage.

12. The control circuit of claim 11, wherein the storage unit blocks the charge distribution when a noise is detected in the sensing signal by the noise detection unit, alternately selects the differential sensing signals corresponding to the odd cycle and the even cycle, and outputs the selected differential sensing signals as the second differential distribution voltages.