Pixel Circuit Timing Control for Uniform Display Brightness
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Solution Overview
Problem
Display devices using pixel circuits face issues of non-uniformity in threshold voltages and parasitic capacitances of driving transistors, leading to uneven brightness and reduced display quality.
Innovation Solution
A pixel circuit design incorporating a driving control circuit and a conduction control circuit, where the conduction control circuit provides the driving current to the light-emitting device after the active level of the first control signal terminal, reducing the impact of parasitic capacitances and voltage fluctuations, and a driving transistor with a top and bottom gate configuration to enhance control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional pixel circuit without separate conduction control circuit is used, then the circuit structure is simple, but brightness non-uniformity occurs due to threshold voltage and parasitic capacitance variations
Solution Approach 1:
The pixel circuit is segmented into multiple functional modules: driving control circuit (including reset circuit, data writing circuit, light emission control circuit, first control circuit, and second control circuit) and conduction control circuit. Each module performs a specific function to address different aspects of brightness uniformity, transforming the monolithic circuit into a modular system that can independently optimize for manufacturing precision while managing complexity through functional decomposition.
Solution Approach 2:
The conduction control circuit acts as an intermediary between the driving transistor and the light-emitting device. It includes a conduction control transistor whose gate is coupled to a first control signal terminal, serving as a mediator that regulates current flow to the light-emitting device based on control signals, thereby compensating for threshold voltage and parasitic capacitance variations without directly modifying the driving transistor or light-emitting device.
2Speed
If the conduction control circuit activates earlier than the light emission control circuit, then current can be supplied sooner, but voltage fluctuations and parasitic capacitance effects increase
Solution Approach 1:
The conduction control circuit is designed to activate in advance of the light emission control circuit during the light emission phase. The first control signal terminal is configured to be at the active level before the second control signal terminal, enabling the conduction control transistor to prepare the current path ahead of time. This preliminary action allows the circuit to respond faster to light emission requirements while the staggered activation timing prevents direct exposure to voltage fluctuations and parasitic capacitance effects.
Solution Approach 2:
The control signals for the conduction control circuit and light emission control circuit are applied periodically in a coordinated sequence during the light emission phase. The first control signal terminal reaches active level at a specific timing, followed by the second control signal terminal reaching active level. This periodic, staged activation pattern ensures optimal current supply timing while minimizing the impact of voltage fluctuations and parasitic capacitance by separating the activation events in time.
3Manufacturing precision
If the duration of the first control signal terminal active level is shorter than the light emission control signal terminal, then brightness non-uniformity is reduced, but current supply duration is limited
Solution Approach 1:
The control signals for the conduction control circuit and light emission control circuit are applied dynamically with different durations. The first control signal terminal is at the active level for a shorter duration compared to the second control signal terminal. This dynamic timing arrangement allows the conduction control transistor to regulate current flow for a limited period to compensate for brightness non-uniformity, while the longer duration of the second control signal ensures sufficient current supply to the light-emitting device throughout the complete light emission phase.
Data Source
AI summary
Disclosed are a pixel circuit, a display apparatus, and a driving method. The pixel circuit includes: a light-emitting device, a driving transistor, a driving control circuit and a conduction control circuit. The driving transistor is configured to generate, based on a data voltage signal, a driving current for driving the light-emitting device to emit light. The driving control circuit is coupled to the driving transistor, and is configured to provide the data voltage signal to a gate of the driving transistor and, in response to a signal from the light emission control signal terminal being at an active level, cause the driving transistor to generate the driving current. The conduction control circuit is configured to provide the driving current from the driving transistor to the light-emitting device in response to a signal from the first control signal terminal being at an active level.