Touch panel controller, touch panel device, and electronic information device
The present invention provides a touch panel controller for controlling even a large touch panel with little EMI. The touch panel controller of the present invention includes a plurality of driving circuits (DC 1 through DCm) for driving respective drive lines (DL 1 through DLm) of a capacitive touch panel unit 2 by supplying driving signals (Ds) to the respective drive lines (DL 1 through DLm), and a rise/fall time of each of the driving signals (Ds) is variable.
1. A touch panel controller comprising:
a plurality of driving circuits that drive respective drive lines of a capacitive touch panel by supplying driving signals to the respective drive lines,
length of rise time and fall time of each of the driving signals being variable;
said controller further comprising:
a control section that controls the lengths of rise time and fall time,
each of the plurality of driving circuits including a plurality of inverter circuits which are configured to change the length of rise time and fall time,
the plurality of inverter circuits include (i) one (1) first inverter circuit, (ii) a plurality of second inverter circuits, and (iii) a plurality of switches whose number is identical with that of the plurality of second inverter circuits;
an input terminal of the first inverter circuit serving as an input terminal of the driving circuit,
the plurality of second inverter circuits being configured by respective transistors having different channel widths,
the plurality of second inverter circuits being connected in series with the respective plurality of switches so as to constitute a plurality of series circuits whose number is identical with that of the plurality of second inverter circuits and that of the plurality of switches,
the plurality of series circuits being connected in parallel with each other between an output terminal of the first inverter circuit and an output of the driving circuit, and
the control section selectively operating the plurality of inverter circuits by controlling ON/OFF of each of the plurality of switches until (i) extraneous emission of an electromagnetic wave (EMI) from the touch panel satisfies a predetermined criterion, and (ii) touch location detection sensitivity of the touch panel satisfies a predetermined criterion, the control section changing a synthesis channel width of the plurality of second inverter circuits so as to change the lengths of rise time and fall time of each of the driving signals.
2. The touch panel controller as set forth in claim 1 , wherein:
the plurality of second inverter circuits are configured by respective transistors that have different sizes.
3. The touch panel controller as set forth in claim 1 , wherein:
the control section controls the lengths of rise time and fall time based on a control signal that has been supplied from outside of said touch panel controller.
4. The touch panel controller as set forth in claim 1 , further comprising:
a receiving section that receives a sensing signal supplied via a sense line of the capacitive touch panel and thus detects electrostatic capacitance of the capacitive touch panel, the control section controlling the length of rise time and fall time based on an output signal supplied from the receiving section.
5. A touch panel device, comprising:
a capacitive touch panel; and
a touch panel controller that includes a plurality of driving circuits for driving respective drive lines of the capacitive touch panel by supplying driving signals to the respective drive lines,
the touch panel controller being a touch panel controller recited in claim 1 .
6. An electronic information device, comprising:
a display for displaying an image; and
a touch panel device,
the touch panel device including:
a capacitive touch panel which is provided on the display, and
a touch panel controller that includes a plurality of driving circuits for driving respective drive lines of the capacitive touch panel by supplying driving signals to the respective drive lines,
the touch panel controller being a touch panel controller recited in claim 1 .