Basic knowledge about USB PD mobile power supply

Release date：2017-08-07   Views：2032

First of all, what is USB PD: USB power delivery, The protocol is based on the type C interface of usb3.1, and is an upgrade product based on usb1.0, USB2.0 and USB3.0. The USB PD standard is divided into five levels: 10W, 18W, 36W, 60W and 100W. The voltage is 5V, 12V, 15V and 20V, and the current is 1.5A 2a, 3a and 5A, according to the successful handshake of communication between the devices, independent negotiation adopts the corresponding power for charging and discharging. In addition, they are bidirectional, and can transform each other's role is power supply. In the future, most electronic devices can be charged through a type C cable, which means that the traditional charging interface can be omitted.

If the USB PD protocol is added to the traditional mobile power supply, it will become a very popular USB PD mobile power supply in the near future. The following is a technical analysis of how to achieve.

To complete the communication and analysis of USB PD protocol, a processor, namely MCU, is required. In addition, it can meet the requirements of type C physical layer in terms of electrical characteristics. At present, ccg2 and ccg3 of cypress and ip2716 of yingjixin, a well-known domestic power supply manufacturer, are all good choices.

The battery of ordinary mobile power supply is usually single cell, and the battery voltage range is from 3.7V to 12.6V, but the USB PD protocol requires 5v-20v. If you want to meet this requirement, you must find a way to adjust the output voltage. For example, three batteries are connected in series. If you need 5V output, you can use a buck DC-DC. If you need to achieve 20V, you need a boost DC-DC. Two of them are expensive. Moreover, such a small PCB can't fit in. Therefore, the major chip manufacturers try their best to integrate these two into one. The buck boost DC DC is born in the sky. Nanxin is the leader in this field, sc8802 It's a very good choice.

So many batteries together are no less than a bomb. Therefore, it is necessary to carry out multi-level protection for the battery. First, add protection and balance in the battery pack. A single cell ip3005 is enough, and 2-3 serial micro cw1046 can be competent. In order to prevent the failure of battery protection board, add secondary protection in MCU. If the temperature, current and voltage are abnormal, it is allowed to enter the protection State stops working.

 

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