Charge Detection Circuit with Dual Storage Capacitors for Display Panels
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Solution Overview
Problem
Conventional light sensor panels face challenges in maintaining the electrical curve of amplifying thin film transistors due to the limited charge detection range, leading to performance deterioration and a shift towards positive voltage direction.
Innovation Solution
A charge detection circuit incorporating a first and second storage capacitor, along with specific thin film transistors and power signals, allows for extended charge accumulation and reduced operation in the linear region, preventing curve shift and enhancing light sensor signal intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the amplifying thin film transistor is operated in the linear region to detect charge amount, then the detected charge amount can reach 10 or more picocoulombs, but the voltage difference between gate electrode and source electrode is very large causing the electrical curve to shift toward positive direction and device performance to deteriorate
Solution Approach 1:
The patent divides the charge detection process into multiple stages using separate thin film transistors (switching TFT and amplifying TFT) and storage capacitors. The switching TFT collects charge in the first storage capacitor during integration, while the amplifying TFT reads charge from the second storage capacitor. This segmentation allows the amplifying TFT to operate in saturation region rather than linear region, preventing electrical curve shift while maintaining detection capability.
Solution Approach 2:
The patent introduces a second storage capacitor as an intermediary between the integration process and the amplification process. Charge is first stored in the first storage capacitor during integration, then transferred to the second storage capacitor for reading by the amplifying TFT. This intermediary structure enables the amplifying TFT to operate in a stable saturation region without requiring large voltage differences, thus preventing electrical curve shift.
2Speed
If the turn-on time of the switching thin film transistor is restricted by frame rate and number of rows, then the integration time is limited to microseconds, but this limits the charge amount that can be accumulated
Solution Approach 1:
The patent performs charge accumulation during the display period before the readout operation. The switching TFT integrates charge from photodetectors during the entire display frame time, storing it in the first storage capacitor. This preliminary accumulation allows sufficient charge to be collected before the amplifying TFT reads the signal, enabling operation in saturation region even with microsecond-level readout time.
Solution Approach 2:
The patent uses periodic operation cycles where the switching TFT integrates charge during the display period and the amplifying TFT reads charge during the non-display period. This periodic separation of integration and readout operations allows the system to maintain high frame rates while accumulating sufficient charge amount through extended integration time.
3Device complexity
If a 4T1C charge detection circuit is used, then the structure is simple, but the detected charge amount is insufficient and the electrical curve shifts toward positive direction
Solution Approach 1:
The patent evolves the 4T1C structure into a 4T2C structure by adding a second storage capacitor. This segmentation separates the integration function (first storage capacitor) from the readout function (second storage capacitor), allowing the amplifying TFT to operate in saturation region with stable electrical characteristics while maintaining the simplicity of the 4-transistor design.
Solution Approach 2:
The patent enhances the functionality of each transistor component. The switching TFT serves both as a selection switch and an integration element, while the amplifying TFT provides both charge-to-voltage conversion and signal amplification. The two storage capacitors work together to enable both charge accumulation and stable readout, achieving multi-functionality without significantly increasing transistor count.
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 effectively increases the charge detection range and light sensor signal intensity, improving the display panel's ability to distinguish between bright and dark states, thereby enhancing device performance and light sensing capabilities.
Implementation Method 1
a gate electrode of the first thin film transistor electrically connected to a first power signal, a drain electrode of the first thin film transistor electrically connected to a second power signal, and a source electrode of the first thin film transistor electrically connected to a first node
Data Source
AI summary
A charge detection circuit and a detection method thereof and a display panel are provided. A second storage capacitor is added to the charge detection circuit. The second storage capacitor can continuously accumulate the charge amount of a second thin film transistor. When a third thin film transistor is turned on, all the charges accumulated by the second storage capacitor flow into an integrator, so that second thin film transistor does not need to be operated in a linear region. Increasing the charge amount of the charge detection circuit is beneficial for the display panel to distinguish light sensor signals.