Capacitive touch device and sensing method thereof

A capacitive touch device includes a capacitive touch panel, a driving control unit, k ADCs, a multiplex network and a processing unit. The capacitive touch panel has an m×n sensing point matrix formed by m driving line and n sensing lines. The driving control unit is coupled to the m driving lines. The multiplex network connects the n sensing lines and the k ADCs by time-domain multiplexing. The processing unit is coupled to the k ADCs. At least a part of the driving lines and at least a part of the sensing lines are assigned to be electrically connected. The processing unit senses according to multiple frequencies to obtain multiple signal strength values, and selects the frequency corresponding to a smallest signal value to be a sensing frequency of the capacitive touch device.

This application claims the benefit of Taiwan application Serial No. 101110874, filed Mar. 28, 2012, the subject matter of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates a capacitive touch device and sensing method thereof.

2. Description of the Related Art

In a current capacitive touch device, after sensing a capacitive touch panel, it is determined whether the touch panel is touched according to a sensing result to accordingly determine a touch position or a control gesture. To increase operating sensitivity, a sensing result is thoroughly inspected for distinguishing minute differences. However, it is possible that an actual operation environment of a capacitive touch device is filled with noises such that a satisfactory signal-to-noise ratio (SNR) can only be obtained to maintain the operation sensitivity by reinforcing signal strength or reducing noises.

For example, the signal strength is reinforced by boosting a driving voltage. Common noises form new electric fields with the capacitive touch device to produce undesirable effects. Source of electric fields include human static electricity, an LCD module, a power supply, a charger or household appliances. For example, approaches for reducing noises for maintaining a preferred SNR include synchronization, shielding, filter and grounding.

However, all of the above approaches for reinforcing signal strength or reducing noises need extra costs, and may also lead to a change in an overall structure and thus fail to meet a light and compact design.

SUMMARY OF THE INVENTION

The invention is directed to a capacitive touch device and associate sensing method for providing an optimal sensing frequency for resisting against noises in an actual operation environment.

According to an aspect of the present invention, a capacitive touch device is provided. The capacitive touch device includes a capacitive touch panel, a driving control unit, k analog-to-digital converters (ADCs), a multiplex network and a processing unit, where k is a positive integer. The capacitive touch panel has an m×n sensing point matrix formed by m driving lines and n sensing lines, where m and n are a positive integer, respectively. The driving control unit is coupled to the m driving lines. The multiplex network connects the n sensing lines and the k ADCs by time-domain multiplexing. The processing unit is coupled to the k ADCs. At least a part of the m driving lines and at least a part of the n sensing lines are assigned to be electrically connected. According to multiple frequencies within a predetermined range, the processing unit senses the electrically connected driving lines and sensing lines to obtain multiple signal strength values from the corresponding ADCs. The processing unit then selects the frequency corresponding to a smallest frequency to be a sensing frequency of the capacitive touch device.

According to another aspect of the present invention, a sensing method for a capacitive touch device is provided. The capacitive touch device includes a capacitive touch panel, a driving control unit, k ADCs, a multiplex network and a processing unit, where k is a positive integer. The capacitive touch panel has an m×n sensing point matrix formed by m driving lines and n sensing lines. The driving control unit is coupled to the m driving lines. The multiplex network connects the n sensing lines and the k ADCs by time-domain multiplexing. Wherein, m, n and k are a positive integer, respectively. The sensing method includes steps of: assigning at least a part of the driving lines and at least a part of the sensing lines to be electrically connected; sensing the electrically connected driving lines and sensing lines by the processing unit according to multiple frequencies within a predetermined range to obtain multiple signal strength values from the corresponding ADCs; comparing the signal strength values by the processing unit; and selecting the frequency corresponding to a smallest signal strength by the processing unit to be a sensing frequency of the capacitive touch device.

According to yet another aspect of the present invention, a capacitive touch device is provided. The touch device includes a capacitive touch panel, a driving control unit, k ADCs, a multiplex network, at least one dummy scan line and a processing unit, where k is a positive integer. The capacitive touch panel has an m×n sensing point matrix formed by m driving lines and n sensing lines, where m and n are a positive integer, respectively. The driving control unit is coupled to the m driving lines. The multiplex network connects the n sensing lines and k ADCs by time-domain multiplexing. The at least one dummy scan line is disposed on the capacitive touch panel and connects to one of the k ADCs. The processing unit is coupled to the k ADCs. According to multiple frequencies within a predetermined range, the processing unit senses the at least one electrically connected dummy scan line to obtain multiple signal strength values from the corresponding ADC. The processing unit then selects the frequency corresponding to a smallest frequency to be a sensing frequency of the capacitive touch device.

DETAILED DESCRIPTION OF THE INVENTION

In a capacitive touch device and associate method provided by the disclosure, through connections between driving lines and sensing lines or a dummy scan line, an optimal sensing frequency is obtained according to sensed noise strengths to resist against noises in an actual operation environment.

FIG. 1shows a block diagram of a capacitive touch device according to one embodiment. A capacitive touch device100includes a capacitive touch panel110, a driving control unit120, k analog-to-digital converters (ADCs)130, a multiplex network135and a processing unit140. The capacitive touch panel110has an m×n touch point matrix formed by m driving lines y1to ymand n sensing lines x1to xn, where m and n are a positive integer, respectively. The driving control unit120is coupled to the m driving lines y1to ym. The capacitive touch device100may further include m amplifiers152, and the driving control unit120may substantially be coupled to the m driving lines y1to ymthrough an approach of a programmable array logic, respectively.

The multiplex network135connects to the n sensing lines x1to xnand the k ADCs130by time-domain multiplexing. The ADCs130convert received values to signal strength values, each of which indicates a sensed capacitance value at a sensing point where each driving line and each sensing line intersect. The capacitive touch device100may further include k amplifiers154, and the k ADCs130may substantially be coupled to the n sensing lines x1to xnthrough the k amplifiers154by an approach of a programmable array logic, respectively. When the sensed signal strength values are too weak, integration may be performed by the amplifiers154to provide the integration results to the ADCs130for further conversion.

The processing unit140, coupled to the k ADCs130, detects the m×n sensing point matrix by mutual sensing and performs subsequent determination and processing on the signal strength values provided by the ADCs130. For example, the driving control unit120and the processing unit140can substantially be integrated into a capacitance sensing integrated circuit.

FIG. 2shows a flowchart of a sensing method for a capacitive touch device according to one embodiment. In Step S200, at least a part of the driving lines y1to ymand at least a part of the sensing lines x1to xnare assigned to be electrically connected. Methods for electrically connecting the driving lines y1to ymand the sensing lines x1to xnare not limited, and can be designed according to actual requirements. Referring toFIG. 3, all the driving lines y1to ymand all the sensing lines x1to xnare assigned to be electrically connected. Thus, all the sensing points are regarded as a same sensing point, and the capacitive touch device100may be regarded as a noise detector.

FIG. 4shows a schematic diagram of a capacitive touch device according to an alternative embodiment. InFIG. 4, the driving lines y1, y3, . . . and the sensing lines x1, x3, . . . are assigned to be electrically connected. Further, considering that a sensing time for sensing the m×n sensing point matrix may be too long, the driving lines y1to ymand the sensing lines x1to xnmay be grouped to reduce a scan time and to appropriately observe higher frequency noises. For example, the driving lines y1to ymare grouped into first driving lines y1, y3, . . . , and second driving lines y2, y4, . . . ; the sensing lines x1to xmare grouped into first sensing lines x1, x3, . . . , and second sensing lines x2, x4. . . . The first driving lines y1, y3, . . . and the first sensing lines x1, x3, . . . are assigned to be electrically connected, and the second driving lines y2, y4, . . . and the second sensing lines x2, x4, . . . are assigned to electrically connected. Methods for electrically connecting the driving lines y1to ymand the sensing lines x1to xmare not limited, and are preferably capable of covering the entire capacitive touch device110.

In Step S210, a plurality of frequencies within a predetermined range are set. For example, the predetermined range is an entire frequency range, or is a specific frequency range by taking limited time and particular environments into consideration. In Step S220, the processing unit140senses the electrically connected driving lines and sensing lines according to the plurality of frequencies within the predetermined range, and obtains from the corresponding ADCs130a plurality of signal strength values corresponding to the different frequencies. In Step S230, the processing unit140compares the signal strength values. In Step S240, the processing unit140selects the frequency corresponding to a smallest signal strength value to be a sensing frequency of the capacitive touch device100.

For example, the processing unit140performs the comparison through a statistical approach. For example, the processing unit140obtains a difference by subtracting a smallest signal strength value from a largest signal strength value under a same frequency, compares the differences of different frequencies, and determines the frequency corresponding to smallest difference to be the optimal sensing frequency. For example, the processing unit140utilizes a difference between two successive signal strength values under a same frequency. When the difference is greater than a predetermined value, a count value is added by 1. The count values of different frequencies are compared, and the frequency corresponding to the smallest count value is selected as the optimal sensing frequency. For example, the processing unit140first obtains an average value of all the signal strength values, accumulates an absolute value of subtracting the average value by each of the signal strength values, and expresses the strength of the noise by an energy integration value. The energy integration values corresponding to difference frequencies are compared, and the frequency corresponding to a smallest energy integration value is selected to be the optimal sensing frequency.

For example, the processing unit140obtains a root-mean-square of all the signal strength values under a same frequency, accumulates an absolute value of subtracting the average value by each of the signal strength values, and expresses the strength of the noise by an energy integration value. The energy integration values corresponding to difference frequencies are compared, and the frequency corresponding to a smallest energy integration value is selected to be the optimal sensing frequency. For example, the processing unit140first obtains an intermediate value of all the signal strength values sequentially arranged under a same frequency, accumulates an absolute value of subtracting the average value by each of the signal strength values, and expresses the strength of the noise by an energy integration value. The energy integration values corresponding to difference frequencies are compared, and the frequency corresponding to a smallest energy integration value is selected to be the optimal sensing frequency. For example, the processing unit140performs a statistical calculation on all the signal strength values under a same frequency, accumulates an absolute value of subtracting the average value by each of the signal strength values, and expresses the strength of the noise by an energy integration value. The energy integration values corresponding to difference frequencies are compared, and the frequency corresponding to a smallest energy integration value is selected to be the optimal sensing frequency.

For example, the processing unit140further selects a plurality of frequencies corresponding to relatively smaller signal strength values to be sensing frequencies of the capacitive touch device100. That is, the capacitive touch device100selects an optimal sensing frequency or a plurality of preferred sensing frequencies for sensing the m×n sensing point matrix for resisting against noises of an actual operation environment.

When a plurality of driving lines and a plurality of sensing lines are electrically connected, an overload may cause the ADCs130to fail in obtaining the signal strength values. Therefore, in Step S220, the driving control unit120further outputs a driving voltage through one of the driving lines that is not electrically connected to the m×n sensing point matrix. The processing unit140then senses the electrically connected driving lines and sensing lines according to a plurality of sensing frequencies. Thus, the driving voltage may be regarded as a carrier wave such that the noises moving the carrier wave can be detected to obtain the signal strength values.

FIG. 5shows a schematic diagram of a capacitive touch device according to yet another embodiment. InFIG. 5, all the driving lines y2to ymand all the sensing lines x1to xmare assigned to be electrically connected, and the driving control unit120outputs a driving voltage through the driving line y1to the m×n sensing point matrix.FIG. 6shows a schematic diagram of a capacitive touch device according to yet another embodiment. InFIG. 6, the driving lines y1, y3, . . . and the sensing lines x1, x3, . . . are assigned to be electrically connected, and the driving unit120outputs a driving voltage through the driving line y2to the m×n sensing point matrix.

Apart from the approaches of electrically connecting at least a part of the driving lines and at least a part of the sensing lines as in the above description, at least one dummy scan line may also be utilized for sensing the noise strength according to another embodiment of the disclosure.FIG. 7shows a schematic diagram of a capacitive touch device according to another embodiment. A capacitive touch device700includes a capacitive touch panel710, a driving control unit720, k ADCs730, a multiplex network735, at least one dummy scan line760and a processing unit740. The capacitive touch panel710has an m×n sensing point matrix formed by m driving lines y1to ymand n sensing lines x1to xn, where m and n are a positive integer, respectively. The driving control unit720is coupled to the m driving lines y1to ym. The capacitive touch device700may further include m amplifiers752, and the driving control unit720may substantially be coupled to the m driving lines y1to ymthrough an approach of a programmable array logic, respectively.

The multiplex network735connects to the n sensing lines x1to xnand the k ADCs730by time-domain multiplexing. The capacitive touch device700may further include k amplifiers754, and the k ADCs730may substantially be coupled to the n sensing lines x1to xnthrough the k amplifiers754by an approach of a programmable array logic, respectively. The at least one dummy scan line760is disposed on the capacitive touch panel710and connects to one of the k ADCs754. The processing unit740is coupled to the k ADCs730.

FIGS. 8 to 10shows schematic diagrams illustrating an arrangement relationship between at least one dummy scan line and a capacitive touch panel according to one embodiment. InFIG. 8, the at least one dummy scan line760is disposed on the capacitive touch panel710in a fencing layout arrangement. InFIG. 9, the at least one dummy scan line760is disposed on the capacitive touch panel710in a quadrilateral layout arrangement. InFIG. 10, the at least one dummy scan line760is disposed on the capacitive touch panel710in a traversing strip-like layout arrangement.

The processing unit740senses the at least one electrically connected dummy scan line760according to a plurality of frequencies within a predetermined range and obtains a plurality of signal strength values from the corresponding ADC, and selects the frequency corresponding to a smallest signal strength value to be a sensing frequency of the touch device700.

Further, in addition to the at least one dummy scan line760implemented by the capacitive touch device700, the at least a part of the driving lines y1to ymand the at least a part of the sensing lines x1to xnin the foregoing capacitive touch device100can also be jointly implemented. That is, for example, the at least one dummy scan line760is jointly implemented with the at least a part of the driving lines y1to ymand the at least a part of the sensing lines x1to xnthat are assigned to be electrically connected inFIGS. 3 to 6.

Therefore, with the above embodiments, the capacitive touch device and sensing method thereof is as described by the disclosure. Through connections between the driving lines and the sensing lines or the dummy scan line, an optimal sensing frequency is obtained according to the sensed noise strengths to resist against noises in an actual operation environment. Thus, an optimal sensing frequency is obtained according to the environment or an overall status before implementing capacitive touch device, and the sensing frequency can also be dynamically updated when implementing the capacitive touch device to adapt to the environment at all times. Further, the disclosure further utilizes a grouping approach to significantly reduce the number sensing points to be sensed, so that the time needed for searching the optimal sensing frequency is shortened to be even more suitable for quickly observing environmental noises and performing dynamic updates. Without any additional design and costs, the capacitive touch device and sensing method thereof is capable of reducing noises.