The Secret Conversation Between Chargers and Devices: Demystifying Fast Charging Handshake Protocols

In today’s digital age, fast charging technology has become an essential part of our daily lives. However, for most users, the complex handshake process behind fast charging remains a mysterious realm. Today, let’s unveil the mystery of fast charging handshake protocols and delve into the secret conversation between chargers and devices.

I. In – Depth Decoding of the USB PD Protocol Layer

• Advantages of the USB PD Protocol: The USB PD (Power Delivery) protocol is an advanced fast – charging technology based on the USB – C interface. It uses a dedicated CC (Configuration Channel) pin for communication and can achieve power transmission of up to 100W. Take a laptop that supports the USB PD protocol as an example. When using a PD – compliant charger, it can charge up to about 70% in an hour, which is significantly more efficient than conventional charging methods.
• Analysis of BMC Encoding Waveforms: In USB PD protocol communication, BMC (Biphase Mark Code) encoding is the core signal transmission method. During PD protocol handshake testing, observing the communication waveforms between the charger and the device with an oscilloscope can clearly reveal the signal characteristics of BMC encoding. When the charger is inserted into the device, it initiates signal exchange with the SOP (Start of Packet) frame. Then, it enters the power negotiation phase. By precisely decoding these waveform signals, we can gain a deeper understanding of the communication details between the charger and the device, providing data support for optimizing fast – charging performance.

II. The Working Principle of Emulator Devices: Hardware – Level Simulation of Emarker Chips

• The Role of Emarker Chips: In USB – C interfaces, Emarker chips are responsible for transmitting power – related information between the charger and the device. This includes parameters such as voltage, current, and power. When the charger is inserted into the device, the Emarker chip sends electronic identification to the device. The device then determines whether it supports the corresponding fast – charging protocol and negotiates power based on this information.
• Risks of Emulator Devices: Emulator devices simulate the electronic identification and communication behavior of Emarker chips, sending false power – related information to the device. This can trick the device into mistakenly thinking that the charger has a higher power output capability, thereby forcibly activating fast – charging mode. The hardware structure of emulator devices includes a microcontroller (MCU), a programmable EEPROM memory, and analog circuits. Although emulator devices can somewhat increase the charging speed of certain devices in actual use, they pose risks such as interfering with normal charging communication, causing unstable charging, and damaging the device’s battery and charging circuit.

III. The Mystery of Compatibility: Why Some Devices Reject Third – Party Fast Chargers

• Brand and Protocol Differences: Different brands and models of devices often adopt their own optimized fast – charging protocols or make special customizations. When third – party fast chargers attempt to perform a protocol handshake with the device, they face numerous challenges. For example, a well – known mobile phone brand’s fast – charging protocol not only follows the general USB PD standard but also adds extra encryption and proprietary communication parameters. Non – officially certified third – party fast chargers cannot correctly identify these parameters, leading to handshake failures and the device rejecting fast charging.
• Impact of Firmware Updates: Device firmware updates can also introduce new compatibility issues. When device manufacturers optimize and upgrade fast – charging technology, they may modify the details of the fast – charging protocol or strengthen security mechanisms. This can cause third – party fast chargers that were originally compatible to fail the handshake after a firmware update.

IV. Future Trends: The 48V Standard of EPR (Extended Power Range)

• Advantages of the EPR (48V) Standard: EPR (Extended Power Range) is the latest extended standard for USB – C and USB PD protocols. It increases the charging voltage from 20V to 48V, supporting power transmission of up to 240W. For high – power devices such as professional laptops, workstations, and high – performance tablets, the EPR 48V standard can meet the high – power requirements and significantly reduce charging time. For example, a laptop that supports the EPR 48V standard can achieve stable charging power of up to 180W when using a compatible charger. Compared with traditional 100W PD chargers, the efficiency is increased by about 80%, and the battery can be charged from 0 to approximately 60% within 30 minutes.
• Challenges of the EPR Standard: The market promotion of the EPR 48V standard faces several challenges. To achieve high – power transmission, it is necessary to comprehensively upgrade and optimize chargers, cables, and device charging circuits, which increases product costs. Additionally, it requires the coordinated development of the industrial chain. Since this standard has just been introduced, there are limited devices and chargers on the market that support it, leaving consumers with few options.

As the core component of fast – charging technology, the fast – charging protocol handshake involves complex technical principles and compatibility issues. By thoroughly analyzing the USB PD protocol, the working principle of emulator devices, compatibility mysteries, and future EPR trends, we can better address fast – charging challenges. It is advisable for users to prioritize chargers and devices that meet standards and have been certified to ensure safe and stable charging. With technological advancements, it is anticipated that fast – charging protocols will become more unified and mature, providing users with more convenient and fast charging experiences.