OLED Compensation Circuit for Parasitic Capacitance
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Solution Overview
Problem
In OLED displays, parasitic capacitors affect the voltage applied to TFT switches, leading to uneven current flow and brightness issues due to differences in parasitic capacitance across OLED units, resulting in non-uniform brightness.
Innovation Solution
A compensation circuit with a driving unit, storage capacitor, subtractor, and controller is introduced, which calculates voltage differences across the storage capacitor's electrode plates to generate a compensation signal that adjusts the data line voltage, reducing the impact of parasitic capacitors on brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a TFT switch is used to control the data line in OLED display, then the display can be driven with simple switching control, but parasitic capacitors in the TFT switch gates affect the applied voltage, resulting in non-uniform brightness
Solution Approach 1:
The patent introduces a compensation capacitor connected to the gate of the TFT switch through a compensation switch. Before the main switching operation, the compensation capacitor is pre-charged to a compensation voltage that anticipates and counteracts the voltage drop caused by parasitic capacitance. This preliminary action ensures that when the TFT switch activates, the gate voltage remains stable and uniform, eliminating brightness non-uniformity while maintaining simple switching control
Solution Approach 2:
The patent implements a feedback mechanism where the compensation voltage applied to the compensation capacitor is adjusted based on the actual performance of the display. By monitoring the voltage across the storage capacitor and the resulting OLED brightness, the system dynamically adjusts the compensation voltage to optimize uniformity. This feedback loop ensures consistent brightness uniformity while maintaining the simplicity of TFT switching control
2Ease of manufacture
If parasitic capacitors are present in TFT switch gates, then the circuit can be implemented with standard TFT technology, but the parasitic capacitors cause voltage fluctuations that affect current flow uniformity
Solution Approach 1:
The patent introduces a compensation capacitor as an intermediary element between the control signal source and the TFT switch gate. This compensation capacitor acts as a buffer that isolates the gate from voltage fluctuations caused by parasitic capacitance. By charging the compensation capacitor to an appropriate voltage, the system maintains stable gate voltage and uniform current flow through the OLED, while still using standard TFT technology for implementation
Solution Approach 2:
The patent changes the voltage parameter applied to the TFT gate by introducing a compensation voltage through the compensation capacitor. By adjusting this compensation voltage parameter, the system compensates for the voltage drop caused by parasitic capacitance during switching operations. This parameter adjustment ensures uniform current flow through the OLED while maintaining compatibility with standard TFT manufacturing processes
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 compensation circuit effectively mitigates the effect of parasitic capacitors, ensuring more uniform brightness across the OLED display by providing a compensation signal based on calculated voltage differences, thereby stabilizing current flow and enhancing display uniformity.
Implementation Method 1
the storage capacitor has a first electrode plate and a second electrode plate opposite to the first electrode plate, wherein the first electrode plate is connected to a control end of the first response switch, the second electrode plate is connected to a second end of the first response switch
Implementation Method 2
the subtractor is configured to calculate a voltage difference between a first voltage data of the first detection port and a second voltage data of the second detection port
Data Source
AI summary
A compensation circuit includes at least one driving unit, each the driving unit includes a first response switch and a storage capacitor, a first end of the first response switch is connected to a light emitting unit, and a second end of the first response switch is connected to a power supply; the storage capacitor has a first electrode plate and a second electrode plate opposite to the first electrode plate, the first electrode plate is connected to a control end of the first response switch, the second electrode plate is connected to a second end of the first response switch, the compensation circuit further includes a subtractor provided with a first detection port, a second detection port and an output port, and a controller provided with a receiving port and a feedback port.