Systems for displaying images

#This application claims the benefit of Taiwan application Serial No. 097126773 filed Jul. 15, 2008, the subject matter of which is incorporated herein by reference.

#1. Field of the Invention

#The invention relates to a system for displaying images, and more particularly to a touch sensing circuit of a system for displaying images.

#The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

#FIG. 1 shows an exemplary embodiment of a touch sensing circuit;

#FIG. 2 shows signal timing when the voltage storage unit of the touch sensing circuit in FIG. 1 detects whether a touch event has occurred;

#The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.

#In an exemplary embodiment of a touch sensing circuit FIG. 1, a touch sensing circuit 1 is applied in a capacitance type touch panel. In the following description, a sensing cell is given as an example. Referring to FIG. 1, the touch sensing circuit 1 comprises a voltage storage unit 10, an integration unit 20, and a voltage amplifying unit 30. The voltage storage unit 10 detects whether a touch event has occurred and generates a corresponding voltage. When a touch event has occurred, there is a voltage variation in the voltage storage unit 10, and the corresponding voltage is changed according to the voltage variation. The integration unit 20 integrates the corresponding voltage generated by the voltage storage unit 10 and generates an integration signal Vint. The voltage amplifying unit 30 receives and amplifies the integration signal Vint and then generates an output voltage Vout for sequential processing, such as touch identification and signal processing.

#Referring FIG. 1, the voltage storage unit 10 comprises capacitors Cpar10, Cpar11, and Cc and switch elements SWA and SWB. A first terminal of the capacitor Cpar10 is coupled to a ground terminal GND, and a second terminal thereof is coupled to a node N1. A first terminal of the capacitor Cpar11 is coupled to the ground terminal GND, and a second terminal thereof is coupled to a node N2. The capacitor Cpar10 is a parasitic capacitor of a signal line coupled to the node N1, while the capacitor Cpar11 is a parasitic capacitor of a signal line coupled to the node N2. The capacitor Ctrans is formed between the nodes N1 and N2. A sensing cell is composed of the switch element SWB and the capacitor Ctrans. A first terminal of the capacitor Cc is coupled to the node N1, and a second terminal thereof is coupled to the ground terminal GND. The capacitor Cc is a parasitic capacitor between windings of the touch panel and the ground terminal GND. A first terminal of the switch element SWA is coupled to the node N1, and a second terminal thereof is coupled to the integration unit 20. A first terminal of the switch element SWB is coupled to the node N1, and a second thereof is coupled to the node N2. When the voltage storage unit 10 of the touch sensing circuit 1 detects whether a touch event has occurred, an alternating current (AC) voltage Vtog is provided to the node N2. In other words, the node N2 is coupled to the AC voltage Vtog. In some embodiments, a relatively high voltage VH and a relatively low voltage VL of the AC voltage Vtog are 5V and 0V respectively, however, without limitation.