OLED Pixel Circuit with Integrated Capacitive Touch Detection
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Solution Overview
Problem
The uneven display brightness in OLED displays due to threshold voltage drift in driving transistors, and the challenge of signal interference in capacitive in-cell touch technology, which affects the display characteristics and touch signal collection.
Innovation Solution
A pixel circuit with a display driving module and capacitive touch detection module that compensates for threshold voltage effects by using storage capacitors and thin film transistors to generate a light-emitting driving signal independent of the threshold voltage, and integrates touch detection into the display driving process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If capacitive in-cell touch technology is applied to OLED display, then touch detection function is achieved, but signal interference and parasitic capacitance adversely affect display characteristics
Solution Approach 1:
The pixel circuit is divided into separate functional modules: a first module dedicated to display driving (including driving transistor and first storage capacitor) and a second module dedicated to touch detection (including second storage capacitor and detection circuit). This segmentation isolates the touch detection parasitic capacitance from the display driving circuit, preventing signal interference while maintaining both functions.
Solution Approach 2:
A coupling capacitor is introduced as an intermediary element to transfer the touch signal from the touch electrode to the detection circuit. This intermediary isolates the touch detection path from the display driving path, allowing touch signal collection without directly affecting the display characteristics and reducing parasitic capacitance interference.
2Illumination intensity
If threshold voltage compensation is implemented, then brightness evenness is improved, but circuit complexity increases
Solution Approach 1:
The threshold voltage compensation function is merged into the existing pixel circuit structure by utilizing the coupling capacitor and the existing transistor network. The compensation occurs naturally through the circuit operation during touch detection phases, eliminating the need for separate compensation circuits and reducing overall complexity while improving brightness evenness.
Solution Approach 2:
The coupling capacitor serves multiple functions: it acts as a charge transfer element for touch signal detection, provides threshold voltage compensation for the driving transistor, and maintains the touch electrode voltage during different operation phases. This multi-functionality reduces the need for additional components and simplifies the overall circuit design.
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 solution improves brightness evenness and display effect in OLED panels while effectively detecting touch signals, achieving integrated display driving and touch detection, thereby reducing the thickness, weight, and cost of the display panel.
Implementation Method 1
a first storage capacitor Cs1, a driving transistor DTFT
Implementation Method 2
an organic light-emitting diode (OLED)
Implementation Method 3
the OLED is driven to emit light with a stable current
Implementation Method 4
there is a considerable parasitic capacitance between a touch electrode and an electrode desired for the operation of the LCD
Data Source
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AI summary
The present disclosure provides a pixel circuit, its driving method, an OLED display panel and a display device. The pixel circuit includes: a display driving module configured to, within a time period and under the control of a first scanning signal from a first scanning line, a second scanning signal a the second scanning line and a control signal from a control line, compensate for a threshold voltage of a driving transistor with a data signal from a data line and a second signal from a second signal source, so that a light-emitting driving signal for the OLED is irrelevant to the threshold voltage of the driving transistor at a third stage of the time period; and a capacitive touch detection module configured to, within the time period and under the control of the first scanning signal and the control signal, detect a touch signal from a touch screen.