Pixel Circuit Boost Capacitors for High-Resolution Low-Power Displays
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Solution Overview
Problem
Existing emissive-type display devices face challenges in achieving higher resolution while maintaining low power consumption.
Innovation Solution
The display device incorporates a pixel structure with specific transistor configurations and capacitors, including boost capacitors and transistors made of low-temperature polycrystalline silicon (LTPS), along with a circuit layer design that optimizes signal timing and voltage distribution to enhance resolution and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the pixel circuit is simplified to reduce manufacturing complexity, then ease of manufacture is improved, but manufacturing precision deteriorates
Solution Approach 1:
The pixel circuit performs threshold voltage compensation in advance during the initialization phase before the light emitting phase. The third transistor activates the second boost capacitor to compensate for the first transistor's threshold voltage early in the operation cycle, ensuring accurate current control is established before data writing begins, thus preventing cumulative errors in the simplified circuit design
2Manufacturing precision
If the pixel circuit components are increased to improve manufacturing precision, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The first node serves multiple functions: it acts as the gate electrode for the first transistor, stores compensation voltage on the storage capacitor, and receives boosting voltage from both the first and second boost capacitors. This multi-functional design allows the circuit to achieve precise threshold voltage compensation without adding separate dedicated components, thereby maintaining manufacturing precision while limiting device complexity
3Measurement precision
If the driving voltage is increased to improve resolution, then measurement precision is improved, but use of energy increases
Solution Approach 1:
The circuit employs periodic boosting actions through the first and second boost capacitors that charge during specific phases (initialization and compensation periods) and discharge during the light emitting phase. This periodic voltage enhancement provides high driving voltage only when needed for light emission, achieving high resolution display while avoiding continuous high power consumption during non-emitting phases
4Productivity
If the transistor switching speed is increased to improve productivity, then productivity is improved, but use of energy increases
Solution Approach 1:
The boost capacitors are automatically charged and discharged based on the natural timing of the scan signals and transistor switching cycles. The first boost capacitor charges when the first scan signal is active and discharges when the light emitting element needs driving voltage. The second boost capacitor charges during the compensation period when the second scan signal is active. This self-service mechanism achieves fast switching without requiring additional active power input for each switching event
Data Source
AI summary
A display device includes a pixel including a light emitting element, first to fourth transistors, a storage capacitor, and first and second boost capacitors. The first transistor is connected between the light emitting element and a first driving voltage line, operates based on a potential at a first node, and the second transistor is connected to a data line, a first electrode of the first transistor, and a first scan line. The third transistor is connected to the first node, a second electrode of the first transistor, and a second scan line. The storage capacitor is connected between the first node and a first driving voltage line, the first boost capacitor is connected between the first node and the first scan line, and the second boost capacitor is connected between the first node and the second scan line.