Patent ID: 9207803
Filing Date: 2015-12-08
Classification: G06F

Abstract:
1. A control circuit for a touch panel comprising a first terminal, a second terminal, and a third terminal, a first resistive film having one edge connected to the first terminal and having another edge, which is opposite to the aforementioned edge, connected to the second terminal, and a second resistive film facing the first resistive film with a gap between them and having one edge connected to the third terminal, the control circuit comprising: a voltage generating unit configured to apply a predetermined first bias voltage and a predetermined second bias voltage to the first and second terminals, respectively; a voltage detection unit configured to detect a panel voltage that occurs at the third terminal; a current detection unit configured to detect a panel current that flows through a path including the first terminal, the first resistive film, and the second terminal; and a coordinate determination unit configured to detect coordinates which a user touched, based on the panel voltage and the panel current, wherein the voltage generating unit comprises a regulator configured to apply the first bias voltage to the first terminal, the regulator including an output transistor arranged on the path including the first terminal, the first resistive film, and the second terminal; and and wherein the current detection unit comprises: a buffer configured to receive the voltage drop across the detection resistor; an operational amplifier; a first resistor arranged between an output terminal of the buffer and a first input terminal of the operational amplifier; a second resistor arranged between the first input terminal of the operational amplifier and a fixed voltage terminal; a third resistor having one end supplied with the predetermined voltage, and having its other end connected to a second input terminal of the operational amplifier; and a fourth resistor arranged between the second input terminal of the operational amplifier and an output terminal of the operational amplifier.