Charing Protocol: USB-C PD
RedotWiki | 2022-11-24
1. Introduction
USB PD: Origin and Evolution
- USB Power Delivery (PD) was developed by the USB Implementers Forum (USB-IF).
- Initially introduced in USB PD 1.0, it has evolved to meet the growing demands of modern devices.
- USB PD is a universal fast-charging protocol used for power delivery and data transmission over a single cable.
2. Understanding USB Power Delivery
Basics of USB PD
- USB PD is a dynamic power negotiation protocol.
- Devices and chargers communicate to determine optimal power levels.
- Supports a wide range of devices, from smartphones to laptops.
USB Power Delivery offers the following features:
- Increased power levels from existing USB standards up to 240W.
- New 28V, 36V, and 48V fixed voltages enable up to 140W, 180W and 240W power levels, respectively.
- An adjustable voltage supply mode allows the device being powered an ability to request intermediate voltages between 15V and up to the maximum available fixed voltage of the charger.
- Power direction is no longer fixed. This enables the product with the power (Host or Peripheral) to provide the power.
- Optimize power management across multiple peripherals by allowing each device to take only the power it requires, and to get more power when required for a given application.
- Intelligent and flexible system level management of power via optional hub communication with the PC.
- Allows low power cases such as headsets to negotiate for only the power they require.
Key Components and Terminology
- Source and Sink: USB PD devices are categorized as power sources (sources) or devices consuming power (sinks).
- Power Rules: USB PD defines rules for power negotiation between sources and sinks.
- Power Profiles: Different power profiles define available voltage and current levels.
USB PD Messages
- USB PD relies on a series of messages for power negotiation.
- Messages include "Request," "Accept," "Capability," and "Alert."
- These messages enable devices to request, offer, and confirm power requirements.
Power Rules and Contracts
- USB PD defines a set of power rules that govern how power is negotiated.
- Power contracts are established during negotiation and specify power requirements.
- Devices follow these contracts to ensure safe and efficient power delivery.
Compatibility and Interoperability
- USB PD is designed for backward compatibility with older USB standards.
- USB PD devices can work with non-PD devices using legacy USB connectors.
- USB PD chargers can adapt to various device power requirements.
3. Evolution of USB PD
USB PD 1.0: Inception and Features
- USB PD 1.0 introduced a maximum power delivery of 100W.
- It primarily targeted laptops and larger devices.
- Limited cable options and adoption initially.
USB PD 2.0: Advancements and Improvements
- USB PD 2.0 expanded compatibility to smaller devices.
- Improved power management and added more power profiles.
- Enhanced safety measures and better interoperability.
- USB PD 2.0 expanded compatibility to a broader range of devices.
- This version introduced support for more compact gadgets such as smartphones and tablets.
- Enhanced compatibility ensured that more devices could benefit from USB PD's fast charging capabilities.
More Power Profiles
- USB PD 2.0 introduced additional power profiles, providing more granularity in power delivery.
- This allowed devices to request and receive power at specific voltage and current levels, optimizing charging efficiency.
Safety and Reliability
- USB PD 2.0 placed a strong emphasis on safety.
- It introduced measures to prevent overcurrent, overvoltage, and overheating, ensuring the safety of both devices and users.
USB PD 3.0: Enhanced Power and Flexibility
Higher Power Delivery
- USB PD 3.0 significantly increased the maximum power delivery capacity to 240W.
- This made it suitable for a broader range of devices, including laptops, monitors, and even some smaller appliances.
Fixed Voltages
- In USB PD 3.0, new fixed voltages of 28V, 36V, and 48V were introduced.
- These fixed voltages allowed for power levels of up to 140W, 180W, and 240W, respectively, providing greater flexibility for various applications.
Adjustable Voltage Supply
One of the key features of USB PD 3.0 is the ability for devices to request intermediate voltages between 15V and the maximum available fixed voltage of the charger.
This dynamic voltage adjustment optimizes power delivery for specific device requirements.
This dynamic voltage adjustment optimizes power delivery for specific device requirements.
4. USB PD 3.1
Advanced Features
- USB PD 3.1 builds upon the foundation of previous versions.
- It enhances support for high-power applications, making it suitable for a wide range of devices, from laptops to industrial equipment.
Protocol Improvements
- USB PD 3.1 includes protocol enhancements that improve power negotiation efficiency.
- These improvements contribute to faster and more reliable power delivery.
- USB PD 3.1 incorporates advanced error handling mechanisms.
- These improvements enhance fault tolerance and error recovery during power negotiation, ensuring greater reliability.
Improved Interoperability
Universal Compatibility:
- USB PD 3.1 continues to prioritize universal compatibility.
- It ensures that devices adhering to this standard can work seamlessly with a wide range of USB PD chargers and cables.
Enhanced Data Transfer:
- USB PD 3.1 not only excels in power delivery but also in data transfer.
- It offers high-speed data transfer capabilities, making it suitable for a variety of applications beyond charging.
5. USB PD vs. Quick Charge: A Comparison
USB PD and Quick Charge: Key Differences
- While both USB PD and Qualcomm's Quick Charge aim to deliver fast charging, they operate differently.
- USB PD is an open industry standard, while Quick Charge is proprietary to Qualcomm.
- USB PD offers greater versatility, supporting a wider range of devices and power levels.
- Quick Charge is primarily associated with Qualcomm Snapdragon-powered devices.
Compatibility
- USB PD chargers and devices are designed to work together seamlessly, ensuring consistent performance.
- Quick Charge, while prevalent, may require specific device-charger pairings for optimal results.
Safety
- USB PD prioritizes safety through its defined power rules and contracts.
- Quick Charge also incorporates safety features but may vary between implementations.
6. Related Resources
7. Parameter list
| Protocol | Max Power | SPR | PPS | EPR | AVS |
|---|---|---|---|---|---|
| USB 1.0 / 2.0 | 2.5W |
500mA@5V
|
/ | / | / |
| USB 3.0 | 4.5W |
900mA@5V
|
/ | / | / |
| USB BC 1.2 | 7.5W |
1.5A@5V
|
/ | / | / |
| PD 2.0 | 100W |
|
/ | / | / |
| PD 3.0 | 100W |
|
|
/ | / |
| PD 3.1 | 240W |
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Remark:
1. SPR:Standard Power Range, Fixed Voltage Charging model
2. PPS: Programmable Power Supply, Programmable Power Supply Charging model
3. EPR: Extended Power Ranger, Fixed Voltage Charging model
4. AVS: Adjustable Voltage Supply, EPR Adjustable Voltage Supply Voltage model
5. Working at 5A requires the 5A Cable, working at EPR Mode/EPR AVS Mode model requires the EPR Cable.
6. The Voltage fields defines the output Voltage range over which the power supply Shall be adjustable in 20mV steps in EPR Model.
The Voltage fields define the output Voltage range over which the power supply shall be adjustable in 100mV steps in EPR AVS Model.
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