Display apparatus, method for driving display apparatus, and pointing device

Abstract

In a display apparatus, a touch panel where driving and sensing electrodes face each other across a dielectric substance outputs a detection signal from the sensing electrode in synchronization with a driving signal applied to the driving electrode. A pointing device points to a position on a touch surface of the touch panel. A detection assisting device includes an inverting circuit for obtaining a detection driving signal corresponding to the driving signal and inverting the phase thereof to generate an inversion signal, and outputs the inversion signal to the sensing electrode via the pointing device. A control device applies the driving signal to the driving electrode, obtains the detection signal generated at the sensing electrode according to the mutual capacitance between the driving and sensing electrodes and the inversion signal, and detects the pointing device in contact with or proximity to the touch panel based on the detection signal.

The invention is claimed as follows: 
     
         1 . A display apparatus comprising:
 a touch panel including a driving electrode and a sensing electrode that faces at least a part of the driving electrode across a dielectric substance, the touch panel being configured to output a detection signal from the sensing electrode in synchronization with a driving signal applied to the driving electrode;   a pointing device configured to point to a position on a touch surface of the touch panel;   a detection assisting device including an inverting circuit configured to obtain a detection driving signal corresponding to the driving signal detected by the pointing device and generate an inversion signal by inverting a phase of the detection driving signal, the detection assisting device being configured to output the inversion signal to the sensing electrode via the pointing device; and   a control device configured to apply the driving signal to the driving electrode, obtain the detection signal that is generated at the sensing electrode according to a mutual capacitance between the driving electrode and the sensing electrode and the inversion signal, and detect the pointing device in contact with or proximity to the touch panel based on the detection signal.   
     
     
         2 . The display apparatus according to  claim 1 , wherein the detection assisting device is provided in the pointing device. 
     
     
         3 . The display apparatus according to  claim 1 , wherein
 the detection assisting device further includes an amplifier circuit configured to amplify the inversion signal by a predetermined gain, and   the detection assisting device outputs the amplified inversion signal to the sensing electrode via the pointing device.   
     
     
         4 . The display apparatus according to  claim 3 , wherein
 the pointing device detects whether or not the pointing device is in contact with the touch surface, and notifies the detection assisting device of a detection result, and   the detection assisting device switches an amplification level for amplifying the inversion signal based on the detection result, by setting a gain of the amplifier circuit to a first gain when the pointing device is in contact with the touch surface and by setting the gain of the amplifier circuit to a second gain when the pointing device is not in contact with the touch surface.   
     
     
         5 . The display apparatus according to  claim 1 , wherein
 the detection assisting device further includes:
 a frequency selection circuit configured to compare a signal component included in the detection driving signal with a frequency of the driving signal, select a first signal having a same frequency as the driving signal, and output the first signal to the inverting circuit; and 
 an adder circuit configured to add a second signal having a frequency different from a frequency of the driving signal to a first inversion signal, which is obtained by inverting a phase of the first signal by the inverting circuit, in order to correct the first inversion signal to generate a correction inversion signal, and 
   the detection assisting device outputs the correction inversion signal to the sensing electrode via the pointing device.   
     
     
         6 . The display apparatus according to  claim 5 , wherein
 the control device includes a noise detection unit configured to collate the detection signal with predefined noise information, change a frequency of the driving signal when determining that noise is included in the detection signal, and notify the detection assisting device of the changed frequency,   the detection assisting device obtains the changed frequency, and   the frequency selection circuit uses the changed frequency for selection of a signal component included in the detection driving signal.   
     
     
         7 . The display apparatus according to  claim 1 , wherein the detection assisting device further includes a phase adjustment circuit configured to compare a phase of an auxiliary signal to be output to the sensing electrode via the pointing device with a phase of the detection driving signal, determine whether or not an amount of phase delay of the auxiliary signal relative to the detection driving signal is within a predetermined allowable range, and align the phase of the auxiliary signal with the phase of the detection driving signal when the amount of phase delay exceeds the allowable range. 
     
     
         8 . A method for driving a display apparatus, the display apparatus including a touch panel and a pointing device, the touch panel including a driving electrode and a sensing electrode that faces at least a part of the driving electrode across a dielectric substance, the touch panel being configured to output a detection signal from the sensing electrode in synchronization with a driving signal applied to the driving electrode, the pointing device being configured to point to a position on a touch surface of the touch panel, the method comprising:
 applying, by a control device, the driving signal to the driving electrode;   obtaining, by a detection assisting device, a detection driving signal corresponding to the driving signal detected by the pointing device;   generating, by the detection assisting device, an inversion signal by inverting a phase of the detection driving signal;   outputting, by the detection assisting device, the inversion signal to the sensing electrode via the pointing device;   obtaining, by the control device, the detection signal generated at the sensing electrode according to a mutual capacitance between the driving electrode and the sensing electrode and the inversion signal; and   detecting, by the control device, the pointing device in contact with or proximity to the touch panel based on the detection signal.   
     
     
         9 . A pointing device for pointing to a position on a touch surface of a touch panel including a driving electrode and a sensing electrode that faces at least a part of the driving electrode across a dielectric substance, the touch panel being configured to output a detection signal from the sensing electrode in synchronization with a driving signal applied to the driving electrode, the pointing device comprising:
 an inverting circuit configured to detect a detection driving signal corresponding to the driving signal and generate an inversion signal by inverting a phase of the detection driving signal; and   an output unit configured to output the inversion signal to the sensing electrode, wherein   the pointing device causes, when the driving signal is applied to the driving electrode, the sensing electrode to generate the detection signal according to a mutual capacitance between the driving electrode and the sensing electrode and the inversion signal.