| Along with USB Type-C interface's adoption in some smart phone, more and more end customer start to investigate the full-new interface. And USB Power Delivery is important portion in this interface function. It will bring revolutionary solution to current consumer electronic. At the same time, it will save social resource and decrease pollution.USB PD is a power delivery standard which provide up to 100W, the standard was drafted by USB_IF (USB Implementer Forum) in July 2012. PD is based on USB interface process smart grid electric energy transmission, power transmission can be bi-directional, also have the system level power supply strategy. USB PD can enable higher voltage and current support, power supply capability of up to 100W which include 10W,18W,36W,60W and 100W five specifications. By 5V,12V and 20V voltage,1.5A current and 2A,3A and 5 A. USB PD can not only supply power for mobile devices, but also for laptops, monitors, projectors, printers and other direct power supply.USB PD also defined VDM (Vendor Defined Message) functionality which enable customized message exchange. VDM need define of device ID, read device ID to check whether support DP or PCIe, then DFP Type-C Alternate mode into alternative. VDM allows information exchange in two USB devices which support PD protocol, which is based on standard PD message format. The VDM message can be used for the power to negotiate directly, but can be used to supply policy change announcement, port mode operation etc.In this paper, through the realization of the USB system on the PD VDM protocol message, give you a better understanding of the PD system, USB VDM message exchange is to be carried out. |
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