Sensing Unit Capacitor Coupling Compensation in Display Devices
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Solution Overview
Problem
In organic light emitting display devices, the capacitor coupling phenomenon occurs due to differences in voltage between the applied data signal and sensing reference voltage, leading to inaccurate sensing voltages being output, which does not correspond to the applied data signal, thereby affecting the accuracy of pixel characteristic sensing.
Innovation Solution
A display device is designed with a sensing unit that includes a current integrator and an integrator capacitor, along with switches and a reference voltage storage capacitor, to maintain the voltage of the second node at the sensing reference voltage during both sensing reference voltage application and sensing current supply, preventing capacitor coupling and ensuring accurate sensing voltage output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sensing reference voltage different from the data signal voltage is applied to the sensing unit, then the sensing unit can operate with a stable reference voltage, but a capacitor coupling phenomenon occurs in the pixel unit causing the sensing voltage to not correspond to the applied data signal
Solution Approach 1:
A capacitor coupling compensation circuit is introduced as an intermediary component between the pixel unit and sensing unit. This circuit includes a compensation capacitor and control switches that actively compensate for the capacitor coupling effect by injecting compensating charge, thereby eliminating the inaccuracy caused by voltage differences between data signal and sensing reference voltage
Solution Approach 2:
The invention dynamically adjusts the voltage parameters in the pixel unit during sensing operation. By controlling switches to connect or disconnect capacitors and voltage sources at specific timing, the circuit parameters (voltage levels, capacitance connections) are changed to prevent capacitor coupling while maintaining proper sensing reference voltage levels
2Measurement precision
If the voltage of the applied data signal and sensing reference voltage are kept the same, then capacitor coupling is prevented, but the sensing unit loses its stable reference voltage operation
Solution Approach 1:
The sensing operation is divided into distinct time segments or phases. During sensing phase, the pixel unit operates with data signal voltage while the sensing unit uses sensing reference voltage, and during compensation phase, the capacitor coupling compensation circuit activates. This temporal segmentation allows both different voltage levels and stable reference operation coexist
Solution Approach 2:
The compensation capacitor is pre-charged to the appropriate voltage level before sensing operation begins. Control switches are activated in advance to establish the proper capacitor connections, preventing capacitor coupling from occurring in the first place rather than correcting it after the fact
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 reduces the capacitor coupling phenomenon, allowing for accurate sensing voltage generation corresponding to the data signal, thereby accurately sensing pixel characteristics and compensating for degradation, ensuring proper luminance emission despite pixel degradation.
Implementation Method 1
the current integrator may include: a current integrator amplifier including the first input terminal and the second input terminal; and an integrator capacitor including one end connected to the first input terminal and another end connected to an output terminal of the current integrator amplifier
Data Source
AI summary
A display device includes: a pixel unit including a pixel connected to a data line; a data driver which supplies a sensing reference voltage to the data line during a sensing period, and supplies a data signal to the data line during a display period; and a sensing unit which receives a sensing current corresponding to the sensing reference voltage during the sensing period, and generates correction data based on the supplied sensing current. The sensing unit includes a current integrator which outputs a sensing voltage based on the sensing current input thereto through a first input terminal and based on the sensing reference voltage input thereto through a second input terminal.