Signal Conversion Control Circuit for Touch Screen
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Solution Overview
Problem
Traditional signal conversion control circuits for resistor-type touch screens face issues with accuracy due to limited maximal output signals and high power consumption, which affect the precision and efficiency of touch position and strength detection.
Innovation Solution
A signal conversion control circuit incorporating an analog-to-digital converter, sample-and-hold circuits, and switches that sample and hold both supplied voltage and ground potential, allowing for reduced current flow and improved accuracy by using operational amplifiers and capacitors to provide reference voltages, thereby minimizing voltage drops and enhancing signal conversion accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the first switch and second switch are turned on to connect supplied voltage and ground potential to the touch screen, then the touch screen can generate output signals through voltage divider, but the current flowing through the touch screen increases significantly (5.6 to 25 mA)
Solution Approach 1:
The patent applies preliminary action by pre-charging capacitors with the supplied voltage and ground potential before the actual signal conversion process. This allows the touch screen to operate using stored voltage references rather than requiring continuous connection to power sources, thereby reducing current consumption while maintaining operational capability.
2Use of energy by moving object
If the first switch and second switch are turned off to reduce current flow through the touch screen, then power consumption decreases, but the maximal output signal of the touch screen is limited to 4.7 volts which significantly affects ADC conversion accuracy
Solution Approach 1:
The patent introduces sample-and-hold circuits as intermediary components that capture and store the supplied voltage and ground potential on capacitors. These held voltages serve as stable reference voltages for the ADC converter, enabling accurate signal conversion even when the main power switches are turned off to reduce current consumption.
3Ease of operation
If the voltage across the first switch and second switch is about 0.3 volts, then the maximal output signal is limited to 4.7 volts, but this voltage drop significantly affects the accuracy of signal conversion for the ADC
Solution Approach 1:
The patent applies preliminary action by pre-charging capacitors in the sample-and-hold circuits to the exact supplied voltage and ground potential levels before conversion. This eliminates the need for switches to maintain precise voltage levels during conversion, as the capacitors already hold the correct reference voltages, thereby removing the 0.3V drop error from the measurement process.
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
The solution reduces power consumption by over 80% and improves the accuracy of analog-to-digital conversion, effectively addressing the limitations of previous designs while maintaining the advantages of resistor-type touch screens.
Implementation Method 1
The first sample-and-hold circuit is configured to provide the analog-to-digital converter with a high-level reference voltage. The second sample-and-hold circuit is configured to provide the analog-to-digital converter with a low-level reference voltage.
Implementation Method 2
The ADC 102 converts the sampled-and-held output signals of the touch screen 500 in accordance with the sampled-and-held supplied voltage and ground potential connected by the high-level and low-level reference voltage terminals.
Data Source
AI summary
A signal conversion control circuit comprises an analog-to-digital converter, a first sample-and-hold circuit, a second sample-and-hold circuit, a first switch, a second switch, a third switch, and a fourth switch. The analog-to-digital converter has an input end for receiving an output signal of a touch screen. The first sample-and-hold circuit is configured to provide the analog-to-digital converter with a high-level reference voltage. The second sample-and-hold circuit is configured to provide the analog-to-digital converter with a low-level reference voltage. The first switch connects a supplied voltage to the touch screen. The second switch connects the touch screen to a ground potential. The third switch connects the supplied voltage to the first sample-and-hold circuit through the first switch. The fourth switch connects the ground potential to the second sample-and-hold circuit through the second switch.