Fast charging is becoming more and more popular, ZHIYUAN Electronics releases USB-PD fast charging test solution

USB-PD (Power Delivery) is a power supply standard based on USB Type-C, with a maximum power of 100W. Although USB-PD fast charging is becoming more and more popular, there is no test tool for fast charging in the industry. ZLG Zhiyuan Electronics officially released the USB-PD test solution and provides free on-site testing! Let's learn about the relevant content together with the test and measurement chat.

1. Introduction to USB Type-C

Type-C is a form of USB interface that can be inserted regardless of the front or back side. It supports USB standard charging, data transmission, video transmission, audio transmission, display output and other functions. After supporting USB-PD, it can achieve up to 100W power supply. The USB-PD involved in this article communicates through the "configuration channel pin CC" of Type-C (Figure 1).

Figure 1 Type-C interface and socket pin function definition

2. USB-PD Introduction

The charging power of the USB standard is relatively small. When both the USB host and the device support USB-PD, the maximum power can reach 20V@5A (Table 1).

Table 1 USB power supply standards

The USB-PD physical layer uses single-wire communication (Type-C configuration channel CC). In order to enhance anti-interference ability and balance the DC component, when sending protocol data, the physical layer first converts the data using 4b/5b encoding, and then uses biphase mark coding (BMC) to perform secondary conversion on the data stream, and finally outputs the signal to the CC line.

The receiving process is the opposite of the sending process, as shown in Figure 2. The sender or receiver is usually a USB PD controller or microprocessor. When analyzing the USB-PD protocol, only the signals transmitted on the CC line can be analyzed, and the analysis process is actually similar to the receiver's behavior.

Figure 2 USB-PD communication process

3. Current USB-PD analysis methods

As USB-PD exploded in 2017, there were no relevant testing and analysis tools in the industry. At present, when analyzing USB-PD, engineers need to manually print out the entire communication process waveform, perform brute force analysis, and then perform reverse decoding against the protocol. The process is very painful! The figure below shows the analysis method seen by the ZHIYUAN Electronics promotion team when visiting a company.

Figure 3 USB-PD printing analysis on-site real shot

Using a conventional oscilloscope, the following method is required for analysis (Figure 4): BMC decoding, 5b4b conversion, and then obtaining the original communication data. Finally, referring to the USB PD specification to parse out the "Good CRC" information frame (the handshake command in USB PD communication). How much hardship and frustration are involved in this process?

Figure 4 USB-PD manual analysis method

4. USB PD analysis methods currently provided by Zhiyuan Electronics

Connect the oscilloscope probe to the CC line of Type-C;

· Use deep memory to sample all the data of a few seconds during the power-on process;

Then open the USB-PD protocol decoding plug-in, and the analysis can be completed in a few seconds.

5. USB-PD analysis effect demonstration

Figure 5 shows the communication waveform between the USB PD charger and the device after it is powered on. From the event list in Figure 5, it can be intuitively seen that the charger can provide 5V@3A, 9V@3A and 15V@3A power supply capabilities, and the charger can output a maximum power of 45W.

Figure 5 ZDS4054 Plus USB-PD protocol analysis

6. USB-PD analysis internal process

Figure 6 takes the "Accept" frame as an example to describe the four processes of internal analysis of the oscilloscope.

① Perform BMC decoding on the signal on the CC line (jump to logic "1", do not jump to logic "0") to obtain a bit stream;

② Combine the bit rate into 5B encoding;

③ Convert the 5B code to 4B code to obtain the original protocol data of half a byte (hexadecimal);

④ Parse the raw data according to the USB PD protocol and translate it into easy-to-understand plain text (can be exported as a web report or CSV file).

Figure 6 USB-PD decoding process analysis

The above is an introduction to the USB-PD fast charging test solution released by ZHIYUAN Electronics in test and measurement - fast charging is becoming more and more popular. If you want to know more related information, please pay more attention to eeworld. eeworld Electronic Engineering will provide you with more complete, detailed and updated information.