Touch Panel Controller Circuit Area Reduction via Code Multiplexing
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Solution Overview
Problem
Conventional touch panel devices require multiple amplifiers for individual sense lines, leading to increased mounting area as the number of sense lines grows, which is inefficient in terms of circuit space usage.
Innovation Solution
A touch panel controller that drives M drive lines in parallel using a first code sequence to generate K first linear sum signals, which are then multiplied by a second code sequence to produce a second linear sum signal, allowing for the estimation of capacitor values through inner product operations, thereby reducing the number of circuits needed and minimizing the mounting area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple amplifiers are provided for individual sense lines to detect capacitor values, then measurement precision is improved, but device complexity and mounting area increase
Solution Approach 1:
The patent combines multiple amplifier functions into a single amplifier by using code sequences to drive multiple drive lines in parallel. The single amplifier processes combined signals from multiple sense lines that have been multiplexed through code-based driving, eliminating the need for separate amplifiers for each sense line while maintaining detection capability
Solution Approach 2:
The patent employs periodic code sequences (such as M-sequences or Walsh-Hadamard codes) to drive drive lines at different time intervals. This periodic driving allows a single amplifier to sequentially process signals from multiple sense lines through time-division multiplexing, reducing the number of amplifiers required while preserving measurement precision through correlation-based signal processing
2Measurement precision
If the number of sense lines is increased to improve touch detection resolution, then measurement precision is improved, but the number of amplifiers and mounting area increase
Solution Approach 1:
The patent transitions from a spatial arrangement where each sense line requires a separate amplifier to a temporal arrangement where code sequences enable time-division multiplexing. This dimensional shift from space to time allows multiple sense lines to share a single amplifier through periodic code-based driving, increasing touch detection resolution without proportionally increasing mounting area
Solution Approach 2:
The single amplifier is designed to perform multiple functions by processing signals from multiple sense lines through code-sequenced driving. The amplifier universally handles detection for all sense lines by correlating received signals with the known code sequences, enabling one component to replace multiple specialized components
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the estimation of capacitor values using a smaller number of signals, resulting in a reduced circuit area and more efficient processing, thus providing a touch panel controller with a smaller mounting area.
Implementation Method 1
a capacitance detecting circuit that detects a distribution of the electrostatic capacitances of capacitors arranged in rows and columns demarcated by M drive lines and L sense lines
Implementation Method 2
The capacitance detecting circuit, which capitalizes on a decrease in capacitance of a capacitor at an area touched with a finger or a pen, detects a contact area corresponding to a touch of a finger or a pen on the touch panel by detecting a change in capacitance
Implementation Method 3
The drive portion 904 drives the drive lines DL1 to DL4 on the basis of a 4×4 code sequence shown in (Exp. 3) of FIG. 16. The drive portion 904 applies a voltage VDD when an element of the code sequence is '1', and applies a zero voltage in the case of an element '0'
Implementation Method 4
The four amplifiers 908 receive and amplify linear sums Y1 to Y4 of electric charges on capacitors along with the sense lines SL1 to SL4 driven by the drive portion 904, respectively
Data Source
AI summary
A touch panel controller (1A) includes: a capacitor drive portion (5A); a multiplying portion (2A) which performs multiplication of first linear sum signals by a second code sequence to obtain signals and then performs addition of the signals to generate a second linear sum signal; an inner product operation portion (3A) which generates a first inner product operation signal by calculating an inner product of the second linear sum signal and the second code sequence; an inner product operation portion (3AA) which generates a second inner product operation signal by calculating an inner product of the first inner product operation signal and the first code sequence. This makes it possible to reduce a mounting area of the touch panel controller.