Control unit, sensing device for a capacitive touch panel and method thereof

Abstract

A noise reducing device for a capacitive touch panel and a method of reducing noise for a capacitive touch panel are disclosed to solve problems related to noise generated by a conventional filter circuit and an integrating circuit or external noise. In the invention, at least one switch circuit is used so that the conventional filter circuit and integrating circuit used in the prior are omitted. Signals output from a current measurement circuit are transmitting to a control unit to calculate the location of a touch point, reducing any noise

What is claimed is: 
     
         1 . A sensing device for a capacitive touch panel, the capacitive touch panel being rectangular and having a transparent substrate and a sensing layer on the transparent substrate, the sensing layer being transparent and electrically conductive, the capacitive touch panel further having a first X side, a second X side, a first Y side and a second Y side, the sensing device comprising:
 a first X side switch circuit connected to the first X side;   a second X side switch circuit connected to the second X side;   a first Y side switch circuit connected to the first Y side;   a second Y side switch circuit connected to the second Y side;   a sensing source, comprising a first sensing signal source and a second sensing signal source; and   a control circuit, receiving at least one first sensing signal generated by the first sensing signal source and at least one second sensing signal generated by the second sensing signal source, the control circuit further comprising:
 a first current measurement circuit, receiving a first X side current signal generated by the first X side switch circuit or a first Y side current signal generated by the first Y side switch circuit; 
 a second current measurement circuit, receiving a second X side current signal generated by the second X side switch circuit or a second Y side current signal generated by the second Y side switch circuit; 
 a first sample and hold circuit, connected to and sampling output of the first current measurement circuit; 
 a second sample and hold circuit, connected to and sampling output of the second current measurement circuit; 
 a switch, selectively connected to one of outputs of the first sample and hold circuit and the second sample and hold circuit according to the received first sensing signal or the second sensing signal; and 
 a control unit, comprising:
 an analogue/digital conversion circuit, connected to the switch to receive a first X side analogue signal generated by the first X side current signal, a first Y side analogue signal generated by the first Y side current signal, a second X side analogue signal generated by the second X side current signal and a second Y side analogue signal generated by the second Y side current signal, and correspondingly converting them into a first X side digital signal, a second X side digital signal, a first Y side digital signal and a second Y side digital signal; and 
 
 a location determining unit, connected to the analogue/digital conversion circuit, and comprising:
 an X coordinate determining device, determining X coordinate of a touch point according to the first X side digital current signal and the second X side digital current signal; and 
 an Y coordinate determining device, determining Y coordinate of the touch point according to the first Y side digital current signal and the second Y side digital current signal. 
 
   
     
     
         2 . A sensing device for a capacitive touch panel, comprising:
 a sensing signal source, providing a sensing signal to a plurality of contacts of the capacitive touch panel;   a plurality of connection circuits, each connection circuit connecting to at least one of the plurality of contacts;   a plurality of digital synchronization circuits, each digital synchronization circuit generating a digital signal according to an analogue signal outputted from one of the connection circuits, and all of the digital synchronization circuits receive corresponding analogue signals simultaneously; and   a location determining unit, calculating a coordinate of a touch point on the capacitive touch panel according to the digital signals.   
     
     
         3 . The sensing device of  claim 2 , wherein the number of the digital synchronization circuits is less than the number of the connection circuits, and each digital synchronization circuit receives corresponding analogue signal from two of the plurality of connection circuits. 
     
     
         4 . The sensing device of  claim 2 , wherein there are four contacts, two pairs of connection circuits, and two digital synchronization circuits, each of the plurality of connection circuits connects to at least one of the plurality of contacts, and the two digital synchronization circuits receive corresponding analogue signals from one of the two pairs of the connection circuits, respectively. 
     
     
         5 . The sensing device of  claim 4 ,
 wherein the four contacts comprise a first contact, a second contact, a third contact and a fourth contact;   wherein the two pairs of the connection circuits comprise a first connection circuit connecting the first contact and the second contact, a second connection circuit connecting the third contact and the fourth contact, a third connection circuit connecting the first contact and the fourth contact and a fourth connection circuit connecting the second contact and the third contact; and   wherein the first and the second connection circuits form a first pair of the connection circuit and the third and the fourth connection circuits form a second pair of the connection circuits.   
     
     
         6 . The sensing device of  claim 4 ,
 wherein the four contacts comprise a first contact, a second contact, a third contact and a fourth contact;   wherein the connection circuits comprise a first connection circuit connecting to the first contact, a second connection circuit connecting to the second contact, a third connection circuit connecting to the third contact, and a fourth connection circuit connecting to the fourth contact; and   wherein the first and the third connection circuits form a first pair of the connection circuits, and the second and the fourth connection circuits form a second pair of the connection circuits.   
     
     
         7 . The sensing device of  claim 2 , wherein the numbers of the contacts, the connection circuits and the digital synchronization circuits are four, two and two respectively, each of the connection circuit connects to at least one of the contacts, and each of the digital synchronization circuit simultaneously receives corresponding analogue signal from two of the connection circuits forming a pair. 
     
     
         8 . The sensing device of  claim 7 ,
 wherein the four contacts comprise a first contact, a second contact, a third contact and a fourth contact;   wherein the two connection circuits comprise a first connection circuit and a second connection circuit, the first connection circuit and the second connection circuit connect with two of the contacts respectively;   wherein the second connection circuit connects with the third contact and the fourth contact if the first connection circuit connects with the first contact and the second contact;   wherein the second connection circuit connects with the second contact and the third contact if the first connection circuit connects with the first contact and the fourth contact.   
     
     
         9 . The sensing device of  claim 7 ,
 wherein the four contacts comprise a first contact, a second contact, a third contact and a fourth contact;   wherein the two connection circuits comprise a first connection circuit and a second connection circuit, the first connection circuit and the second connection circuit connect with a contact respectively;   wherein the second connection circuit connects with the third connection circuit if the first connection circuit connects with the first contact;   wherein the second connection circuit connects with the fourth contact when the first connection circuit connects with the second contact.   
     
     
         10 . The sensing device of  claim 2 , wherein the plurality of digital synchronization circuits receive corresponding analogue signal simultaneously according to a clock signal. 
     
     
         11 . The sensing device of  claim 2 , wherein each of the connection circuits comprises one or any combination of the following:
 a filtering circuit;   an integration circuit;   a sample-and-hold circuit; and   a simple conducting wire.   
     
     
         12 . The sensing device of  claim 2 , wherein the location determining unit calculates the coordinate according to differences of the digital signals between the touch point being touched or not. 
     
     
         13 . The sensing device of  claim 2 , wherein the shape of the capacitive touch panel is rectangular, and the contacts connect to four sides of the capacitive touch panel. 
     
     
         14 . The sensing device of  claim 2 , wherein a plurality of parts of each analogue signal are received by corresponding digital synchronization circuit. 
     
     
         15 . The sensing device of  claim 2 , wherein the coordinate is calculated as X=(I ΔX2 −I ΔX1 )/(I ΔX1 +I ΔX2 ) and Y=(I ΔY2 −I ΔY1 )/(I ΔY1 +I ΔY2 ), X and Y are a first dimension and a second dimension of the capacitive touch panel, I ΔX1  is the difference between the analogue signal I X1  received before touch and the analogue signal I X2  during touch of the capacitive touch panel, I ΔX2  is the difference between the analogue signal I X1  received during touch and the analogue signal I S2  before touch of the capacitive touch panel, I Δy1  is the difference between the analogue signal I Y1  received before touch and the analogue signal I Y2  during touch of the capacitive touch panel, and I αY2  is the difference between the analogue signal I Y1  received during touch and the analogue signal I Y2  before touch of the capacitive touch panel. 
     
     
         16 . The sensing device of  claim 2 , wherein each of the digital synchronization circuits comprises a digital integration circuit, comprising:
 an analog/digital converter for generating a plurality of digital sub-current values continuously by repeated sampling of the analogue signal and executing analogue signal to digital signal conversion; and   an adder for adding the digital sub-current value.   
     
     
         17 . The sensing device of  claim 16 , wherein a plurality of parts of each analogue signal are received sequentially by analog/digital converters of a plurality of integration circuits, and wherein the adders of the integration circuits generate a plurality of summation outputs of the analogue signals. 
     
     
         18 . The sensing device of  claim 2 , wherein the capacitive touch panel comprises an upper layer and a bottom layer, the upper layer of the capacitive touch panel and the bottom layer of the capacitive touch panel comprises a first pair of opposing sides and a second pair of opposing sides, and the contacts connect to the first and the second pair of opposing sides. 
     
     
         19 . The sensing device of  claim 18 , wherein the contacts of the first pair of opposing sides of the touch panel are connected correspondingly and the contacts of the second pair of opposing sides of the touch panel are connected correspondingly for receiving the sensing signal to provide a parallel electric field. 
     
     
         20 . A control unit of a capacitive touch panel, comprising:
 a plurality of digital integration circuits, each the digital integration circuit comprising:
 an analogue/digital converter for converting a plurality of sampled analogue signals into a plurality of digital signals continuously when the analogue signal receives one signal source in an adder cycle; 
 an adder for generating an integration value according to a summary of the digital signals in the adder cycle; and 
 a coordinate calculation unit for calculating a coordinate of a touch point on the capacitive touch panel according to the integration value. 
   
     
     
         21 . The control unit of  claim 20 ,
 wherein the coordinate calculation unit generates a summary value of the signal source according to at least one integration value of the same signal source during a cycle,   wherein the cycle comprises at least one of the adder cycle,   wherein the coordinate calculation unit generates a first summary value and a second summary value of a plurality of signal sources in a first cycle and a second cycle, respectively,   wherein the coordinate calculation unit generates a difference between the first summary value and the second summary value, and   wherein the coordinate calculation unit calculates the coordinate according to the difference.   
     
     
         22 . The control unit of  claim 21 , wherein the coordinate is a one dimension coordinate and the difference comprises a first difference and a second difference, the one dimension coordinate is calculated from (the first difference−the second difference)/(the first difference+the second difference). 
     
     
         23 . The control unit of  claim 21 ,
 wherein the coordinate is a two dimension coordinate and the difference comprises a first, a second, a third and a fourth difference,   wherein a first dimension coordinate of the two dimension coordinate is calculated from ((the first difference+the second difference)−(the third difference+the fourth difference))/(the first difference+the second difference+the third difference+the fourth difference),   wherein a second dimension coordinate of the two dimension coordinate is calculated from ((the first difference+the fourth difference)−(the second difference+the third difference))/(the first difference+the second difference+the third difference+the fourth difference).   
     
     
         24 . The control unit of  claim 20 ,
 wherein the coordinate calculation unit generates a summary value of the same signal source according to at least one integration value of the same signal source during a cycle,   wherein the cycle comprises at least one adder cycle,   wherein the digital integration unit generates a plurality of first, second, third and fourth summary values from a first, second, third and fourth cycle, respectively,   wherein the coordinate calculation unit generates a first difference between the first summary value and the third summary value, and a second difference between the second summary value and the fourth summary value from the same signal source,   wherein the coordinate calculation unit calculates a first dimension coordinate of a two-dimension coordinate according to the first difference, and a second dimension coordinate of the two-dimension coordinate according to the second difference.   
     
     
         25 . The control unit of  claim 20 ,
 wherein the coordinate calculation unit generates a summary value of the same signal source according to at least one integration value of the same signal source during a cycle, the cycle comprises at least one adder cycle,   wherein the digital integration unit generates a plurality of first, second, third, fourth, fifth and sixth summary values according to a first, second, third, fourth, fifth and sixth cycle, respectively,   wherein the coordinate calculation unit generates a first difference and a second difference by subtracting the third summary value and the fifth summary value from the first summary value of the same signal source, respectively,   wherein the coordinate calculation unit generates a third difference and a fourth difference by subtracting the fourth summary value and the sixth summary value from the second summary value of the same signal source, respectively,   wherein the coordinate calculation unit calculates a first dimension coordinate of a first and a second two dimension coordinate according to the first difference and the second difference, respectively, and the coordinate calculation unit calculates a second dimensional coordinate of the first and the second two dimension coordinate according to the second difference and the fourth difference.   
     
     
         26 . The control unit of  claim 20 , wherein the signal source is chosen from a corner, a side, or two neighboring corners of the capacitive touch panel. 
     
     
         27 . The control unit of  claim 20 , wherein the cycle comprises a plurality of continuous adder cycles, the analogue signal of the same signal source is received from different digital integration circuits in different adder cycles of the cycle, respectively. 
     
     
         28 . The control unit of  claim 20 , wherein the adder cycle is a ½ or ¼ clock cycle of one of the sampled analogue signal. 
     
     
         29 . The control unit of  claim 20 , further comprises a switch circuit connects to a plurality of signal sources, the switch circuit determines whether each digital integration circuit receives the signal source of analogue signal. 
     
     
         30 . The control unit of  claim 20 , wherein the digital integration circuit receives the plurality of analogue signals from a first and a second pair of opposing sides of a capacitive touch panel in a first and a second cycle, respectively, a first pair of opposing sides of the capacitive touch panel crisscross with a second pair of opposing side. 
     
     
         31 . The control unit of  claim 20 , further comprising a storage circuit for storing the integration values.