USB Host Auto-Detect Charging Protocol Handshake
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Solution Overview
Problem
Portable devices often cannot differentiate between charging down-stream ports (CDPs) and dedicated charging ports (DCPs), leading to suboptimal current draw and extended charging times due to incompatible protocols.
Innovation Solution
A method and apparatus that utilize handshaking protocols on data lines (D+ and D−) to detect and adapt to different charging protocols, allowing USB host devices to supply power according to the correct protocol, enabling maximum current draw based on recognized standards like PRC Telecommunications Industry Standard YD/T 1591-2006 and USB 2.0 Battery Charging Specification 1.1.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If portable devices use a single USB compatible input to save space, then device complexity is reduced, but the device cannot differentiate between CDP and DCP power sources, leading to limited current draw
Solution Approach 1:
The host device performs preliminary handshaking actions by applying voltage to data lines D+ and D- before actual power transfer begins. This preliminary communication phase allows the portable device to identify the correct charging protocol (CDP or DCP) and establish appropriate current draw parameters before power is delivered, resolving the contradiction between simple structure and adaptive power management.
2Reliability
If portable devices limit current draw to ensure safety, then reliability is improved, but charging time increases
Solution Approach 1:
The system implements feedback through bidirectional handshaking on data lines D+ and D-, where the portable device responds to the host's voltage applications with corresponding signals. This feedback mechanism allows the system to dynamically determine the maximum safe current draw based on the identified power source type and protocol, enabling both safety and optimized charging speed.
3Adaptability or versatility
If different charging standards are used for different power sources, then adaptability to various power sources is improved, but compatibility between different standards decreases
Solution Approach 1:
The charging protocol is segmented into distinct phases: a handshaking phase where voltage is applied to data lines to identify the correct protocol, and a power delivery phase where current is drawn according to the identified protocol. This segmentation allows the system to support multiple charging standards (CDP, DCP, and proprietary protocols) by sequentially testing and selecting the appropriate protocol, thereby maintaining both adaptability and compatibility.
Data Source
AI summary
An embodiment of the invention provides a method for providing power to a USB client device and polling for a correct protocol. A USB host device provides power and a first part of a first handshake determined by a first protocol. The host then monitors the client for a second part of the first handshake. When the second part of the first handshake is detected by the host, the client recognizes that power may be applied according to the first protocol. When the second part of the first handshake is not presented by the client device, the host provides a first part of a second handshake according to a second protocol. When the second part of the second handshake is provided by the client, the host the client recognizes that power may be applied according to the second protocol.