1. Field of the Invention
The present invention is related to a touch detection method and capacitive sensing device, and more particularly, to a touch detection method and capacitive sensing device simultaneously performing a mutual-sensing mode and a self-sensing mode.
2. Description of the Prior Art
With advances in touch control technology, more and more electronic devices are equipped with touch panels as main input interfaces to replace conventional keyboards and mice. The touch panel is a component attached to a display of the electronic device, and a user can command the electronic device by tabbing the touch panel via a finger or a touch pen. As a result, since the space conventionally allocated for the keyboard is no longer required, the display of the electronic device can be enlarged to improve user experiences.
According to sensing methods, the touch panels can be classified into resistive, capacitive, optical and acoustic types. The capacitive touch panels feature great sensitivity, and therefore are widely employed in various kinds of electronic devices. Specifically, a touched region of the capacitive touch panel is determined based on a capacitance change of the capacitive touch panel. However, in addition to capacitors designed by the manufacturer, there are parasitic capacitors in the capacitive touch panel. The parasitic capacitors lead to a bias in touch detection signals, which results in difficulties during the following recognition process. Therefore, the bias of the touch detection signals has to be removed.
It is therefore an objective of the present invention to provide a touch detection method and capacitive sensing device capable of removing a bias component caused by parasitic capacitors so as to simplify a touch detection signal.
The present invention discloses a touch detection method for a capacitive sensing device, the capacitive sensing device utilized for detecting capacitance variance of a panel, a variable capacitor comprising a first end electrically coupled to the panel, the touch detection method comprising simultaneously providing a first clock signal to a second end of the variable capacitor and providing a second clock signal to the panel; determining a touched region of the panel according to a voltage variance of the first end of the variable capacitor; and generating an output signal utilized for indicating the touched region; wherein the first clock signal and the second clock signal have opposite phases against each other.
The present invention further discloses a capacitive sensing device for detecting capacitance variance of a panel, the capacitive sensing device comprising an input end, electrically coupled to the panel; an analog front-end circuit, electrically coupled to the input end, for determining a touched region of the panel according to a voltage variance of the input end and generating an output signal utilized for indicating the touched region; and a variable capacitor, comprising a first end, electrically coupled to the input end; and a second end, electrically coupled to analog front-end circuit, for receiving a first clock signal; wherein the first clock signal is provided to the second end when a second clock signal is provided to the panel; wherein the first clock signal and the second clock signal have opposite phases against each other.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
Please refer to
However, deficiencies of the panel 100 results in a parasitic capacitor Cnoise, as shown in
Other than the mutual-sensing mode, the capacitive sensing device 10 can be equipped with a self-sensing capacitor Cself via a switch circuit, as shown in
Since both the mutual-sensing bias component Rnoise_mutual and the self-sensing bias component Rnoise_self are difficult to be identified in the following recognition process, the present invention further provides an embodiment below, which can remove the bias components Rnoise_mutual, Rnoise_self from the output signal Raw_data.
Please refer to
In other words, the capacitive sensing device 50 is a combination of the mutual-sensing embodiment of
Notably, the mutual-sensing clock signal CLKmutual and the self-sensing clock signal CLKself may be designed to have opposite phases against each other, such that Rself_com and Rnoise_com caused by the self-sensing clock signal CLKself are negative, and the mutual-sensing bias component Rnoise_mutual can counteract the self-sensing bias component Rnoise_com. In addition, the parasitic capacitor Cnoise varies with the panel, and varies with a position on the panel. Therefore, the capacitance of the parasitic capacitor Cnoise also has to be adjusted based on practical conditions, so as to remove parasitic capacitors of different panels. In practice, the capacitance of the variable capacitor Ccom can be determined based on experiments or computer simulations.
Operations of the capacitive sensing device 50 can be summarized into a touch detection process 60, as illustrated in
Step 604: Simultaneously provide the self-sensing clock signal CLKself to a second end of the variable capacitor Ccom and provide the mutual-sensing clock signal CLKmutual to the panel 100.
Step 606: The analog front-end circuit 500 determines the touched region of the panel 100 according to a voltage variance of the first end of the variable capacitor Ccom.
Step 608: The analog front-end circuit 500 generates the output signal Raw_data utilized for indicating the touched region.
Via the touch detection process 60, the output signal Raw_data=Rmutual−Rself_com no longer includes any bias component caused by the parasitic capacitor Cnoise. In other words, the output signal uses Raw_data=0 to represent a non-touch region of the panel 100. Such a representation can be easily interpreted to find out whether there is a touch region, so as to simplify the recognition process.
Notably, the touch detection process 60 implements both the self-sensing mode and the mutual-sensing mode, as illustrated in
To sum up, the present invention utilizes signal correlation between the self-sensing mode and the mutual-sensing mode to simultaneously implement the self-sensing mode and the mutual-sensing mode. As a result, by feeding the opposite phase clock signal, the bias signal components of the self-sensing mode and the mutual-sensing mode counteract each other, so as to simplify the touch sensing signal.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
This application claims the benefit of U.S. Provisional Application No. U.S. 62/201,594 filed on Aug. 6, 2015, the contents of which are incorporated herein.
Number | Date | Country | |
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62201594 | Aug 2015 | US |