Source Driver Precharge Latent Voltage LCD Power
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Solution Overview
Problem
Display devices consume unnecessary power when updating source lines as the source driver both decreases and increases the voltage already stored on the source line from the previous frame update, leading to inefficiency.
Innovation Solution
The source driver precharges using a latent voltage on the source line, allowing it to adjust its output to the desired voltage without wasting power by initially setting the output voltage to the latent voltage before slewing to the final voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the source driver updates the voltage on source lines sequentially, then the display can be updated frame by frame, but the source driver consumes unnecessary power by both decreasing and increasing the voltage already stored on the source line
Solution Approach 1:
The patent applies preliminary action by precharging the source driver to the latent voltage of the source line before the actual voltage update. This is achieved by coupling the source driver to a source line that has been previously charged to the desired latent voltage, allowing the driver to start from the correct voltage level rather than from zero or a fixed reference. This eliminates the need for the driver to both decrease and increase the voltage, thereby reducing power consumption while maintaining frame update capability.
2Reliability
If the source driver slews from one voltage to another voltage for each source line update, then the display voltage can be updated, but the driver consumes extra power by decreasing and then increasing the voltage
Solution Approach 1:
The patent applies self-service by having the source line itself provide the latent voltage that the source driver needs. Instead of the driver generating all voltages from an internal reference, the source line's stored charge (latent voltage) serves the driver's needs. The driver simply needs to couple to the source line and use its existing voltage, eliminating the wasteful cycle of decreasing and then increasing voltage that would otherwise occur.
3Productivity
If the source driver is continuously coupled to source lines, then voltage updates can be performed, but the driver cannot efficiently precharge using latent voltage from previous frames
Solution Approach 1:
The patent applies segmentation by dividing the source driver's operation into distinct phases: a precharge phase where the driver is coupled to a source line to acquire the latent voltage, and an update phase where the driver actively drives the voltage to the desired level. This temporal segmentation allows the driver to efficiently utilize the latent voltage from previous frames without interfering with the active update process, thereby reducing power consumption while maintaining high update speed.
Data Source
AI summary
Embodiments of the invention generally provide an input device that includes one or more source drivers that are coupled to a display screen. Specifically, one of the source drivers may be coupled to a plurality of source lines (or column lines) on the display screen which the source driver uses to set voltages associated with one or more sub-pixels that determine the color displayed by the pixel. When driving voltages onto subsequent source lines, the input device may precharge the source driver using a latent voltage stored on the source lines. That is, if the source line was previously driven to a particular voltage by the source driver, the input device uses that latent voltage to precharge the output of the source driver to the same voltage. The source driver may then adjust its output to a desired voltage and drive the desired voltage onto the source line and sub-pixel.