USB power delivery (usbpd) is one of the current mainstream fast charging protocols developed by usb-if organization. It can increase the default maximum power 5V / 2A type-C interface to 100W power. And can carry out two-way or even networking power transmission, with system level
Power Supply scheme. Usbpd communication carries out half duplex communication through the modulation of FSK signal coupled with AC on VBUS (24MHz), so as to realize the charging process of mobile phone and charger. Source end and sink end respectively represent
Adapter end and sink controller of internal chip of mobile phone. From the perspective of USB communication transmission, it can be understood as usbhost (master device) and usbotg (slave device). (5V/9V/12V/15V/20V) When the
Cable is connected, the SOP communication of PD protocol starts on the C C line (type-C interface communication configuration channel), so as to select the specification of power transmission. In this part, the sink end asks the source end for the power configuration parameters (5V / 9V / 12V / 15V / 20V) that can be provided. Take 9V charging of mobile terminal and adapter as an example. The overall process is as follows: USB OTG terminal (slave device: adapter terminal) monitors the voltage status on VBUS. If there is 5V voltage of VBUS and it is detected that the ID pin of OTG is 1K pull-down resistance, it means that the cable supports usbpd communication. At this time, the communication process begins.
1. Sink end initiates SOP (initial stage), starts usbpd equipment manager of source end, and applies for the specification data provided by source end;
2. The source terminal replies to the list of specifications that can be provided, that is, according to the usbpd specification, parse the message to get all the voltage and current list pairs supported by the adapter;
3. Sink terminal returns to the selected voltage specification, i.e. select a voltage and current pair, bring the required current parameters, and send out the corresponding request;
4. The internal decoding and conversion of the source end adapter is connected to the world of electronic products .Upon request, adjust the output of the adapter to raise the VBUS cable from 5V to 9V;
5. After the mobile phone receives the message, the sink terminal will adjust the charging voltage and current until the VBUS cable at the source terminal reaches 9V and reaches a stable state for charging;During the charging process, the mobile phone can send messages dynamically to request the charger to change the output voltage and current, so as to realize the fast charging process.
