**USB-PD Protocol Explanation**
The USB-PD communication process involves modulating protocol layer messages into a 24 MHz FSK (Frequency Shift Keying) signal, which is then coupled to the VBUS line or extracted from it to enable communication between a device and its charger. This allows for bidirectional power delivery and advanced configuration of voltage and current levels.
As shown in the diagram, the 24 MHz FSK signal is coupled to the DC level on VBUS using a coupling capacitor. To prevent this high-frequency signal from interfering with the DC power supply or the host’s VBUS voltage, a low-pass filter made up of an isolation inductor is used to remove the FSK component.
Here's how the USB-PD protocol works in practice, using a smartphone and a compatible charger as an example:
1. The USB OTG PHY monitors the VBUS voltage. If it detects 5V and sees that the OTG ID pin is pulled down by a 1kΩ resistor (indicating a PD-compatible cable), it knows the connection supports USB-PD.
2. The OTG performs standard BCSV 1.2 charger detection and initializes the USB-PD device policy manager. This manager checks for the presence of an FSK signal on the VBUS DC level and decodes the message to extract the "CapabilitiesSource" information, which lists all supported voltages and currents.
3. The phone selects a suitable voltage and current pair based on user settings, adds it to the "Request" message, and sends it back via FSK modulation on the VBUS.
4. The charger receives and decodes the FSK signal, responds with an "Accept" message, and adjusts its output accordingly.
5. The phone receives the "Accept" message and adjusts its charging IC to match the new voltage and current settings.
6. Throughout the charging process, the phone can dynamically send new "Request" messages to adjust the power delivery, enabling faster and more efficient charging.
**What Can PD Chargers Be Used To Charge?**
PD fast charging has gained significant traction this year, especially after Google announced that all Android phones must be compatible with USB-PD. This move eliminates the need for non-PD protocols to adjust voltage through USB ports. Similarly, China’s Ministry of Industry and Information Technology has also endorsed PD fast charging, signaling a push toward universal fast charging standards.
Now, half a year later, let’s look at what PD chargers can do today.
One of the most notable devices is the Nintendo Switch. While many in mainland China may not be familiar with it, the Switch created a huge buzz in the gaming world this year. It uses a USB-C port and supports PD fast charging, making it one of the early adopters of this technology.
Apple has also played a major role in promoting PD charging. The new MacBook models feature USB-C ports and come with 29W PD chargers. Additionally, the iPhone 8, 8 Plus, and X models now support PD fast charging.
Xiaomi has also embraced PD charging. Their latest Xiaomi MIX2 and the small notebook Por 15.6 both support PD fast charging. The Por 15.6 can charge up to 50% in just 30 minutes, showcasing impressive speed.
Samsung’s S8 and Note8 models also support PD fast charging, even though they use their own fast charging technology. Most USB-C equipped laptops now support PD charging as well.
**What Are the Chargers That Support the PD Protocol?**
1. **Romans MPA830QFD Charger**
This charger is known for its versatility. It supports USB-PD 3.0 and QC 3.0, offering multiple output options. With three ports, including a Type-C port supporting 20V/1A, 15V/1.4A, 12V/1.5A, 9V/2A, and 5V/3A, it’s ideal for Apple, Samsung, and Xiaomi devices. Despite being bulky, it features foldable pins for better portability.
2. **ORICOTSM-1U Charger**
This 24W charger supports 5V/3A, 9V/2.5A, and 12V/2A. It’s compact and lightweight (93g), with foldable US-style prongs. It supports QC fast charging and can deliver up to 27W for the Galaxy Note7, but doesn’t fully support Apple devices.
3. **ACT Anke News APS-PD024W-G**
A 24W PD charger with outputs like 12V/2A, 9V/2.5A, and 5V/3A. It’s compact, portable, and comes with global certifications. Its white and gray matte design makes it a sleek addition to any desk.
4. **Green Union CD127**
Designed with a simple, Apple-like aesthetic, this charger supports 5V/3A, 12V/2A, 14.5V/2A, and 20V/1.45A. It’s ideal for MacBook and iPad Pro users who want to avoid original chargers.
5. **Apple Original Charger A1540**
Released with the 12-inch MacBook in 2015, this charger is globally compatible with wide voltage input. It offers 14.5V/2A and 5.2V/2.4A outputs. Though expensive, it’s reliable for Apple devices.
6. **Xiaomi Air Charger ADC6501TM**
This 65W charger supports USB-PD 3.0 and delivers up to 20V/3.25A. It’s perfect for Xiaomi notebooks and other PD-enabled devices.
7. **Huawei MateBook Charger HW-59C200CHPQ1**
A lightweight charger (110g) that supports Type-C and MicroUSB. It offers 5V/2A, 9V/2A, and 12V/1A outputs, making it versatile for Huawei devices and Android phones alike.
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