Touch position detector of capacitive touch panel and method for detecting the touch position

• US 8,232,972 B2
• Filed: 01/09/2008
• Issued: 07/31/2012
• Est. Priority Date: 07/31/2007
• Status: Active Grant

• Current Assignee: Elan Microelectronics Corporation
• Original Assignee: Elan Microelectronics Corporation
• Inventors: Huang, Chun-Chung, Wang, Tsun-Min, Lin, Chun-Yu, Lin, Tse-Chi
• Primary Examiner(s): Shalwala, Bipin
• Assistant Examiner(s): LAM, NELSON C
• Application Number:
  US11/971,788
• Publication Number:
  US 20090032312A1
• Time in Patent Office: 1,665 Days
• Field of Search: 345173-179
• US Class Current: 345/173
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• 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

Abstract

A touch position detector includes a plurality of capacitance sensors, a negative capacitance compensation unit, an analog/digital converter and a micro processing unit. The negative capacitance compensation unit is utilized to compensate the capacitance of the capacitance sensor and get a capacitance change. The micro controller unit is utilized to detect the touch position according to the capacitance change. It is easy to get the touch position by using the touch position detector.

Claims

1. A touch position detector of a capacitive touch panel, comprising:

a plurality of capacitive sensors for sensing a touch object;

a negative capacitance compensation unit coupled to the capacitive sensors, for compensating a basic capacitance of the capacitive sensors and obtaining a change of capacitance;

an analog/digital converter (ADC) coupled to the negative capacitance compensation unit, for converting the change of capacitance to a digital signal; and

a micro controller unit coupled to the ADC, for detecting a position of the touch object according to the change of capacitance;

wherein the negative capacitance compensation unit comprises;

a transducer for converting the sensing capacitance to a measuring signal;

a normalized negative compensation unit for generating a corresponding feedback signal according to the basic capacitance of the capacitive sensors; and

an adder for summing the measuring signal and the feedback signal to obtain the change of capacitance of the capacitive sensors.

2. The touch position detector of claim 1, further comprising a multiplexer coupled between the sensors and the ADC.

3. The touch position detector of claim 1, wherein the negative capacitance compensation unit further comprising a successive approximation ADC coupled to the normalized negative compensation unit, for getting the basic capacitance without touching.

4. The touch position detector of claim 1, further comprising a signal amplifier coupled to the negative capacitance compensation unit, for amplifying the output signal of the negative capacitance compensation unit.

5. The touch position detector of claim 4, further comprising a normalized signal amplitude gain controller coupled between the signal amplifier and the micro controller unit, for generating a corresponding feedback signal to a largest signal strength from loading object.

6. A method for detecting a touch position of a touch panel, comprising:

setting an initial value for a capacitive sensor;

inputting a capacitance gain parameter of a channel;

measuring a capacitance of the channel;

generating a feedback signal according to a negative capacitance compensation parameter;

summing the capacitance of the channel and the feedback signal to obtain a change of capacitance of the channel;

detecting a touch position according to the change of capacitance of the channel; and

acquiring the negative capacitance compensation parameter before setting the initial value for the capacitive sensor, wherein the process comprises;

sensing a basic capacitance signal of the channel;

reading the basic capacitance signal; and

processing the basic capacitance signal to get the negative capacitance compensation parameter of the channel and storing the negative capacitance compensation parameter.

7. The method for detecting a touch position of claim 6, further comprising acquiring the capacitance gain parameter before setting the initial value for the capacitive sensor, wherein the process comprises:

inputting a basic capacitance compensation value of the channel;

measuring the capacitance of the capacitive sensor when a standard object is touching on the position of the capacitive sensor; and

processing the capacitance of the capacitive sensor to generate the capacitance gain parameter.