what is USB Power Delivery

- Oct 14, 2020-

what is USB Power Delivery?


Usb-power delivery (USBPD) is one of the mainstream fast charging protocols.It is a fast charging specification developed by the USB-IF organization.The USBPD increases power transmission through USB cables and connectors, extending the power supply capability of the cable bus in USB applications.The specification allows for higher voltages and currents, up to 100 watts of power transmission, and the freedom to change the direction of power transmission.Relationship between USBPD and Type-C.People often talk about USBPD and Type-C together, or even call type-C charger PD charger.USBPD and Type-C are two different things. USBPD is a fast charging protocol, while Type-C is a new interface specification.The type-C interface supports a maximum of 5V/3A by default, but after the implementation of the USBPD protocol, the output power can be supported up to the 100W mentioned above.So many devices that use the Type-C interface now support the USBPD protocol.The future of USBPD.USBPD is now available in VERSION 3.0 of USBPD.Under the promotion of Google, USBPD has incorporated qualcomm's QC quick charge protocol and obtained the support of the ministry of industry and information technology of China.It is expected to unify the current chaotic fast-charging market in the near future.

The advantage of PD:

Usb-pd fast charging protocol can increase the power transmission through USB cables and connectors, expand the power supply capacity of cable bus in USB application, so as to improve the charging voltage or current, and can freely change the direction of power transmission.

The type-C interface supports a maximum of 15W (5V/3A) by default, but after implementing the USB-PD protocol, the output power can be supported up to 100W (20V/5A).

So now many devices that use type-C interface will support USB PD protocol.

USB PD Quick Charging communication principle

The communication of USBPD is a process in which messages from the protocol layer are converted into 24MHZ FSK signals and coupled to VBUS or FSK signals are obtained from VBUS to realize the communication between mobile phone and charger.

The principle of USBPD, taking mobile phone and charger both support USBPD as an example, is explained as follows:

1)USBOTG's PHY monitors VBUS voltage. If the 5V voltage of VBUS exists and the OTGID foot is detected to be 1K pull-down resistance (not OTGHost mode, the ID resistance of OTGHost mode is less than 1K), it means that the cable supports USBPD;

2)USBOTG performs normal BCSV1.2 standard charger detection and starts the USBPD device policy manager, which monitors whether FSK signal is coupled on the DC level of the VBUS, and decipher the message to obtain the CapabilitiesSource message, and then parses the message according to the USBPD standard to obtain a list of all voltages and currents supported by the USBPD charger;

3) The mobile phone selects a voltage and current pair from the CapabilitiesSource message according to the user's configuration, and attaches the voltage and current pair to the Payload of the Request message. Then the policy manager coupling the FSK signal to the VBUS DC level;

4) The charger decodes FSK signal and sends an Accept message to the phone, and adjusts the DC voltage and current output of PowerSupply;

5) The mobile phone receives an Accept message and adjusts ChargerIC's charging voltage and current;

6) The mobile phone can dynamically send Request message to Request the charger to change the output voltage and current during charging, so as to realize the rapid charging process.

Relationship to other charging protocols

Usb-pd protocol does not have the same relationship with other manufacturers' quick-charge protocols, but the relationship between inclusion and inclusion.

In the PPS (Fast Charging Technical Specification) released by USB-IF, THE USB-PD 3.0 protocol already includes Qualcomm QC 3.0 and 4.0, Huawei SCP and FCP, MTK PE3.0 and PE2.0, and OPPO VOOC.

From the above, we can see the power of USB-PD protocol, which is also the reason why mobile phones and laptops rapidly popularize Type-C interface and support USB-PD fast charging in recent years.

From the layout of various mobile phone manufacturers and original chip factories, USB PD fast charging will become the preferred charging scheme for electronic devices such as mobile phones, game consoles and laptops at present, and USB Type-C will also become the only interface for power and data transmission between electronic devices in the next decade. The unified USB PD fast charging protocol is about to come.

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