CROSS-POINT MATRIX FOR INFRARED TOUCH SCREEN

摘要

PROBLEM TO BE SOLVED: To miniaturize a ring board outside a touch screen display by eliminating a high-side multiplexing circuit of light emitting elements and detectors; to reduce its cost; and to improve its appearance.

SOLUTION: A circuit aggregate detects a touch point in a display region by arranging a plurality of the light emitting elements and the detectors around the display region so as to face the respective detectors to the respective light emitting elements. A switching circuit is used for connecting the light emitting elements and the detectors in a switching matrix having a plurality of rows and columns. The switching circuit includes a plurality of row lines and column lines corresponding to the rows and the columns of the switching matrix. Low-side switching transistors are used for selectively connecting the light emitting elements and the detectors to the row lines and the column lines, respectively. A common modulation signal is connected to the anodes of all the light emitting elements. A detection signal is given by connecting the collector terminals of detector phototransistors in common.

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