USB PD introduction
Oct 04, 2019| USB PD introduction
In the USB PD, a pair of directly connected ports use the CC line in the USB Type-C connector as the communication channel to negotiate the voltage, current, and direction of power supply in the Cable. This adopted mechanism is independent of other modes of operation for negotiating USB power.
The USB PD also acts as a sideband channel to support standard or factory-defined mode operations. Work Mode is associated with SVID. The structured VDM Message in the PD protocol can be used to discover supported SVIDs and Modes, and also supports the entry and exit of Modes when needed. Multiple Active Modes can work simultaneously.
Once the contract relationship negotiated with this standard is used, the power relationship negotiated by any previously used USB 2.0, USB 3.1, USB Type-C 1.2 or USB BC 1.2 mechanism will be replaced. When in PD mode, there will be a contractual relationship (either explicit or implicit) that determines the level of power supply and direction available at work. When a pair of ports working normally in PD mode are disconnected, it will cause a system reset or the SRC side will remove the power supply (except during the PRS and FRS process, when the original SRC removes the power supply in order to get the new SRC Turn on the power supply).
The process of explicit contractual relationship negotiation begins with the SRC initiating a series of power supply capabilities, and then SNK requests a specific capability from it, and the SRC accepts the application.
An implicit contractual relationship is a specified level of power supply in a particular state (such as during PRS and FRS or after they occur). It can be known that the state of the implicit contractual relationship is only temporary. A new explicit contract needs to be negotiated between the ports immediately.
Shenzhen Shenchuang Hi-tech Electronics Co., Ltd(SChitec) is a high tech enterprise which specialized in phone accessories production and sales. Our main products include travel chargers, car chargers, USB cables, power banks and other digital products.All products are safe and reliable, with unique styles.products pass certificates like CE,FCC,ROHS,UL,PSE,C-Tick,etc, If you are interested in, you can contact ceo@schitec.com directly.
Stay Charging Safely with SChitec