HDMI Power Delivery via SCDC Negotiation
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Solution Overview
Problem
High-speed wired interfaces like HDMI do not support power transfer, requiring external power cables for portable devices, which is inconvenient and necessitates a method for power delivery through the interface without separate devices.
Innovation Solution
A method for power transmission and reception using HDMI, where devices exchange power delivery support and request information through Extended Display Identification Data (EDID) and Status and Control Data Channel (SCDC) messages, allowing power negotiation and transfer between source and sink devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If HDMI interface is used for video/audio transmission, then video and audio signals can be transmitted without compression and with high bandwidth, but power transfer function is not supported requiring external power cables
Solution Approach 1:
The patent combines power transfer functionality with the existing HDMI data transmission interface by utilizing the SCDC (Status and Control Data Channel) for power negotiation and the TMDS channels for power delivery. This merging eliminates the need for separate power cables while maintaining the existing video/audio transmission capabilities of HDMI.
Solution Approach 2:
The HDMI interface is extended to perform multiple functions: traditional video/audio transmission, control signal communication, and power delivery. The SCDC messages are used for both data exchange and power negotiation, making the interface universal and eliminating the need for dedicated power transmission components.
2Ease of operation
If separate external power cable is connected for power supply, then adequate power can be provided to portable devices, but user convenience is reduced due to additional cable management
Solution Approach 1:
The patent merges power delivery with the existing HDMI data cable by utilizing the TMDS channels and SCDC protocol. This combination reduces the total number of cables from two (video cable + power cable) to one (HDMI cable with integrated power), significantly improving ease of operation and reducing cable management complexity.
3Device complexity
If power delivery is implemented through existing HDMI protocol, then cable count is reduced and convenience is improved, but power negotiation and control mechanisms must be extended
Solution Approach 1:
The patent implements preliminary power negotiation through SCDC messages exchanged during the HDMI link establishment phase. Devices exchange power delivery support information and required power information before actual power transfer begins, allowing the system to configure power delivery parameters in advance and ensuring compatibility without requiring complex runtime negotiation.
Solution Approach 2:
The patent employs feedback mechanisms where devices monitor power delivery status and exchange SCDC messages to confirm power negotiation results. The sink device reports its power delivery capabilities, and the source device adjusts its output accordingly, creating a closed-loop system that ensures reliable power transfer while maintaining protocol simplicity.
Data Source
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AI summary
A method for supplying and receiving, by a sink device, power using an HDMI may include being connected to a source device through the HDMI, receiving a +5 V signal, transmitting an HPD signal, transmitting EDID information including power delivery support information or power delivery request information of the sink device, receiving a first SCDC write message including required power characteristic information indicative of a first power level requested by the source device from the sink device, writing the required power characteristic information in the power delivery configuration registers of an SCDCS, writing support power characteristic information indicative of a second power level capable of being supplied by the sink device in the status flag register of the SCDCS, transmitting the written support power characteristic information to the source device, and transmitting the power of the second power level to the source device.