OLED Circuit Voltage Compensation Using Reset Capacitor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional organic light emitting diode (OLED) circuits face issues with threshold voltage shifts in thin film transistors (TFTs) leading to uneven frame displays due to inadequate voltage compensation, especially in high-resolution and large-size OLED panels, resulting in irregular operations and charge sharing problems.
Innovation Solution
An organic light emitting diode circuit with a voltage compensation arrangement that includes a first capacitor, first and second TFTs, a reset circuit, and an OLED, where the first TFT receives a reference voltage, the second TFT's gate is coupled to the first TFT's gate, and the third TFT receives a pixel voltage, with a reset circuit setting the first capacitor's end to a first voltage level smaller than the reference voltage, enhancing the speed of threshold voltage compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional voltage compensation arrangement is used, then threshold voltage compensation is achieved, but compensation time is too long causing irregular operation and charge sharing issues
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage compensation before the data writing stage. The compensation operation is completed in advance using the compensation capacitor and compensation transistor, so that when data writing occurs, the compensation is already done and no charge sharing issue arises. This resolves the contradiction by eliminating the need for compensation during the critical data writing period.
Solution Approach 2:
The patent segments the operation into distinct phases: a compensation phase where the compensation transistor charges the compensation capacitor to compensate for threshold voltage shifts, and a data writing phase where pixel data is written without interference. This segmentation allows compensation to occur independently before data writing, resolving the time conflict.
2Productivity
If data writing time is reduced for high resolution panels, then productivity is improved, but voltage compensation cannot complete causing charge sharing issues
Solution Approach 1:
The patent performs voltage compensation as a preliminary action before data writing. The compensation transistor charges the compensation capacitor in advance, so that when data writing occurs at high speed, the compensation is already complete. This allows high productivity data writing without compromising voltage stability.
3Device complexity
If TFT MP1 is used for compensation with same device feature as TFT MP2, then compensation mechanism is simplified, but compensation speed is insufficient for high resolution panels
Solution Approach 1:
The patent uses the same device feature TFTs for compensation but performs the compensation action in advance before data writing. This allows the simplified compensation circuit structure to achieve sufficient compensation speed by completing the compensation process prior to the critical data writing period, resolving the speed limitation.
Data Source
AI summary
An organic light emitting diode circuit of an organic light emitting display with voltage compensation technique includes a first capacitor, a first TFT, a second TFT, a third TFT, a reset circuit and an OLED. The first TFT has a first terminal for receiving a first voltage, and a second terminal coupled to its gate and a first end of the first capacitor. The second TFT has a first terminal for receiving a second reference voltage and a gate coupled to the gate of the first TFT. The third TFT is coupled to the first capacitor and receives a pixel voltage and scan signal. The reset circuit sets the first end of the first capacitor to have a first voltage level. The OLED has an anode coupled to a second terminal of the second TFT and a cathode for receiving a third reference voltage. The first voltage level is smaller than a voltage level of the first reference voltage.