Pixel Circuit Isolating Transistor Power Supply Interference
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Solution Overview
Problem
Conventional pixel circuits experience unstable light emission due to threshold voltage drift in driving transistors, affecting the stability of the driving current and luminance of light emitting diodes, and existing threshold compensating circuits are prone to interference from external power supplies.
Innovation Solution
A pixel circuit design that includes a compensating unit, a driving unit, a light emitting unit, a capacitor, and an external power supply, where the compensating unit sets a voltage at a first node using a compensating transistor, and the driving unit generates a driving current based on this voltage, the external power supply voltage, and the threshold voltage of the driving transistor, with an isolating transistor ensuring the data signal is not affected by the external power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional threshold compensating circuit is used to eliminate threshold voltage drift influence, then the driving current stability is improved, but the data signal becomes susceptible to interference from external power supply voltage
Solution Approach 1:
The pixel circuit is divided into distinct functional modules: a data writing module that writes data signals to a storage node, and a light emitting module that generates driving current. This segmentation isolates the data signal path from the power supply voltage, preventing interference while maintaining driving current stability through separate control mechanisms.
Solution Approach 2:
A storage node acts as an intermediary between the data signal input and the driving transistor gate. The storage node capacitively couples the compensated data signal to the driving transistor, isolating the sensitive data path from direct connection to the external power supply while still enabling stable driving current generation.
2Reliability
If the driving transistor operates in saturated state to provide stable driving current, then the light emitting stability is improved, but the driving current becomes sensitive to threshold voltage variations
Solution Approach 1:
The circuit performs preliminary threshold voltage compensation during the data writing phase before the light emitting phase. The compensating transistor and capacitor establish a pre-compensated voltage on the storage node that accounts for threshold voltage variations, so that when the driving transistor operates in saturation during light emitting, the threshold sensitivity has already been corrected.
Solution Approach 2:
The circuit uses the driving transistor itself as a feedback element by operating it in saturation mode during the data writing phase. This allows the transistor's own threshold voltage characteristics to be automatically compensated through the saturation region operation, eliminating the need for separate sensing transistors while maintaining accuracy.
Data Source
AI summary
The present disclosure provides a pixel circuit, a driving method, pixel structure and display panel. A driving unit of the pixel circuit includes an isolating transistor, driving transistor and light emitting control transistor coupled between an external power supply and light emitting unit in series with source and drain electrodes. Both gates of the light emitting control transistor and isolating transistor receive a first control signal, and the driving transistor and compensating transistor are transistors with common gate region. The driving transistor is used to generate a driving current to drive the light emitting unit to emit light when the isolating transistor and light emitting control transistor are turned on under the control of the first control signal, and the driving current is obtained according to the first voltage, a voltage of the external power supply, and a threshold voltage of the driving transistor in the driving unit.