Touch Panel Controller Power Management via Periodic Detection
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Solution Overview
Problem
In semiconductor devices with touch panel controllers and display drivers, unnecessary power consumption occurs when the display driver is suspended or stopped, and during touch detection operations, especially when the interval between touch detections is shortened, leading to increased power usage.
Innovation Solution
Implementing a processor that periodically wakes up from a Sleep state to perform touch/no touch detection, requesting activation only when a touch is detected, and using a second touch detection mode that allows for parallel driving of half the detection electrodes, reducing the need for continuous scanning and thus lowering power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the touch panel controller continuously performs touch detection to ensure responsive input detection, then touch detection accuracy and responsiveness are improved, but power consumption increases significantly
Solution Approach 1:
The touch panel controller performs touch detection periodically rather than continuously. The controller waits for a predetermined period after the display driver suspends operation before initiating touch detection, and stops detection after a predetermined period following display driver activation. This periodic action reduces power consumption while maintaining adequate touch detection accuracy for user input responses.
Solution Approach 2:
The touch detection operation is made dynamic by adjusting its timing based on the display driver's operational state. The controller dynamically starts or stops touch detection according to whether the display driver is active or suspended, rather than maintaining a fixed continuous detection schedule. This dynamic adjustment optimizes the balance between detection accuracy and power consumption.
2Use of energy by moving object
If the processor remains in Sleep state to save power, then power consumption is reduced, but the system responds slower to touch inputs
Solution Approach 1:
The touch panel controller performs preliminary touch detection before the display driver fully activates from suspension. By initiating detection in advance during the transition period, the system ensures that touch inputs are detected even when the processor is in Sleep state, reducing the perceived response time without requiring the processor to remain fully awake.
Solution Approach 2:
The touch panel controller acts as an intermediary between the Sleep state processor and the active display driver. It performs touch detection independently during the transition phase, bridging the gap between power-saving mode and full operation mode, thereby maintaining responsive input detection without requiring continuous processor activity.
3Use of energy by moving object
If the display driver is suspended to reduce power consumption during idle periods, then power consumption is reduced, but touch detection becomes less accurate
Solution Approach 1:
The touch panel controller performs a simplified partial touch detection operation during the display driver's suspended state. Instead of completing the full touch scanning sequence, it performs only the essential capacitance measurement, which is sufficient to detect whether a touch occurred during the suspension period. This partial action maintains adequate accuracy for determining touch presence while significantly reducing power consumption.
Solution Approach 2:
The touch detection process is segmented into two phases: a preliminary detection phase performed during display driver suspension using simplified operations, and a full detection phase performed after activation. This segmentation allows the system to use minimal resources during suspension while maintaining the ability to accurately detect touch inputs, thereby balancing power consumption and measurement precision.
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 significantly reduces power consumption by limiting touch detection actions to only when necessary and optimizing the touch detection process, allowing for efficient power management and accurate touch position calculation.
Implementation Method 1
A touch panel which supports a multipoint touch according to a mutual capacitance method has a plurality of drive electrodes and a plurality of detection electrodes, and mutual capacitances formed thereby. A finger or hand brought close to such a touch panel reduces a mutual capacitance between the electrodes near the finger or hand.
Data Source
AI summary
The semiconductor device has a touch panel controller, a processor and a display driver. The semiconductor device is arranged so as to reduce an electric power uselessly consumed while the action of the display driver is stopped or suspended and further, and an electric power uselessly consumed by the touch-detecting action for recovery of the display driver from the state of the action being stopped or suspended.The processor built in the semiconductor device together with the touch panel controller and the display driver returns to its workable state from Sleep state each time a given length of time elapses, and then causes the touch panel to perform a touch-detecting action. When the processor cannot acquire a result of judgment as “being touched”, it returns to Sleep state again, and waits for the given length of time to elapse.