eDP Display Device Panel Self-Refresh Power Management
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Solution Overview
Problem
As display devices increase in size and resolution, existing interfaces like DisplayPort struggle to efficiently manage power consumption, particularly in portable devices, where battery life is a concern.
Innovation Solution
The implementation of a panel self-refresh (PSR) technique using an embedded DisplayPort (eDP) interface, which generates control signals to identify still images and reduce power usage by storing and reusing previous frames, thereby minimizing unnecessary signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the DisplayPort interface is used to support high resolution and color depth, then the data bandwidth is increased, but the power consumption is increased
Solution Approach 1:
The display device autonomously determines when to enter PSR mode by monitoring its own output buffer status and frame timing, without requiring external controller intervention. The device self-manages the transition between full refresh and still image modes, reducing communication overhead and power consumption while maintaining high data bandwidth capability when needed.
Solution Approach 2:
The system dynamically switches between two operational modes: full refresh mode for moving images and PSR mode for still images. This dynamic adaptation allows the interface to maintain high bandwidth capability when required while reducing power consumption during static display periods, resolving the contradiction between bandwidth availability and power usage.
2Use of energy by moving object
If the eDP transmission unit is turned off to save power, then the power consumption is reduced, but the image signal transmission may be interrupted
Solution Approach 1:
The display device prepares for PSR mode in advance by ensuring that a complete frame is fully written to the output buffer before disabling the eDP transmission unit. This preliminary action guarantees that no image data is lost during the transmission interruption, maintaining reliability while enabling power savings.
Solution Approach 2:
The useful action of image display continues uninterrupted through the use of frame buffering. While the eDP transmission unit is off, the buffered frame is continuously supplied to the display panel, ensuring seamless image output. When the transmission unit reactivates, it seamlessly transitions back to receiving new frame data, maintaining continuous useful action without interruption.
3Use of energy by moving object
If the frame memory stores and reuses still image signals, then the power consumption is reduced, but the device complexity is increased
Solution Approach 1:
The existing frame buffer, originally designed for general-purpose image data storage, is repurposed to serve dual functions: storing moving image frames and storing still image frames for PSR mode. This multi-functionality eliminates the need for separate memory structures, reducing device complexity while enabling power-saving still image display.
Solution Approach 2:
Instead of creating a complex dedicated still image memory system, the patent uses a simple copy mechanism where the last received frame is duplicated and held in the output buffer for multiple display cycles. This copying approach achieves power savings through minimal additional complexity, reusing existing buffer infrastructure.
Data Source
AI summary
A display device includes: a system unit which output image signals corresponding to frames and a first or second image control signal based on the image signals; an eDP reception unit which receives the image signals and the first or second image control signal from the system unit, provides a still image signal based on the first image control signal, and provides the image signals based on the second image control signal; and a frame memory which stores the still image signal and outputs the still image signal while the first image control signal is provided to the eDP reception unit, where the still image signal is one of the image signals; the eDP reception unit recovers first clock signals based on the image signals; and the frame memory outputs the still image signal based on a second clock signal generated based on the first clock signal.