Pixel Driving Circuit Voltage Control for High Density Displays
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Solution Overview
Problem
The existing silicon substrate OLED display technology faces challenges with a small data voltage range, which limits gray-scale segmentation and reproduction, particularly in achieving high pixel densities required for virtual and augmented reality applications.
Innovation Solution
A pixel driving circuit is introduced, comprising a voltage control circuit and a light-emitting time control circuit, which control the voltage at a voltage writing node and the light-emitting device's electrodes to increase the data voltage range, enabling better gray-scale representation by varying the light-emitting time and brightness based on voltage differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional glass substrate or silicon substrate displays are used, then the display can be manufactured with existing technology, but the pixel density is limited and cannot achieve PPI greater than 2000 required for VR applications
Solution Approach 1:
The patent changes the substrate material parameter from conventional glass or silicon to flexible substrate, enabling new manufacturing approaches. It also changes the driving mode parameter from conventional voltage driving to combined voltage control and light-emitting time control, achieving higher pixel density compatibility for VR applications requiring PPI > 2000
2Measurement precision
If the data voltage range is kept small as in conventional displays, then the circuit design is simpler, but the gray-scale segmentation and reproduction capability is insufficient
Solution Approach 1:
The patent segments the driving function into two independent parts: voltage control circuit for setting voltage level and light-emitting time control circuit for controlling duration. This segmentation enables extended gray-scale control capability while keeping each circuit module relatively simple and manageable
Solution Approach 2:
The patent introduces dynamic light-emitting time control where the light-emitting duration is adjusted based on voltage differences between nodes. This dynamic control mechanism extends the effective data voltage range and improves gray-scale reproduction without requiring a completely complex circuit structure
3Ease of operation
If the light-emitting device is continuously connected to the voltage writing node, then the voltage control is simple, but the light-emitting time cannot be controlled for gray-scale modulation
Solution Approach 1:
The patent applies preliminary action by first setting the voltage at the voltage writing node through the voltage control circuit before controlling the light-emitting duration. The light-emitting time control circuit prepares the control signal in advance based on the voltage difference, enabling both simple voltage control and precise gray-scale modulation in sequence
Data Source
AI summary
A pixel driving circuit and a display device are provided. The pixel driving circuit includes a voltage control circuit and a light-emitting time control circuit. The voltage control circuit is configured to control a voltage at a voltage writing node according to a first data voltage on a first data line; the light-emitting time control circuit is configured to connect the voltage writing node to a first electrode of a light-emitting device or disconnect the voltage writing node from the first electrode of the light-emitting device according to a second data voltage on a second data line and a reference voltage at a reference voltage terminal; and a second electrode of the light-emitting device is electrically connected to a first voltage terminal.