USB Reference
USB Charging
USB charging covers how ports, chargers, devices, and cables provide or negotiate power through USB-C, USB Power Delivery, PPS, and Battery Charging.
Charging Systems · Charging Performance · Articles
Related: USB Connectors · USB Standards · USB Adapters
USB charging systems
USB-C defines connector-level power, USB Power Delivery adds negotiated power, PPS adds programmable output, and Battery Charging covers legacy charging ports.
| Technology | What it defines | Power handling | Connector scope | Main compatibility check |
|---|---|---|---|---|
| USB-C charging | Power behavior of the USB Type-C connector system | Type-C current advertisement with optional USB Power Delivery | USB-C | Port, device, cable, current advertisement, and optional PD support |
| USB Power Delivery | Negotiated USB power between source and sink | Source advertises supported capabilities and the sink requests a supported level; Extended Power Range supports up to 240 W | Modern USB PD use is centered on USB-C | PD support on source and sink plus a cable suitable for the requested power |
| USB PD PPS | Programmable Power Supply operation within USB Power Delivery | Compatible devices request adjustable voltage/current within advertised ranges | USB-C with compatible USB PD implementations | PPS support on charger and device plus appropriate cable capability |
| USB Battery Charging | Legacy charging-port detection and behavior | BC 1.2 identifies charging port types and charging behavior without USB PD negotiation | Common on legacy USB-A and Micro-USB-era equipment | BC 1.2 support and correct charging-port type |
What determines USB charging speed?
Fast charging is an outcome of compatible hardware and power negotiation rather than a separate USB connector or data standard.
| Part of the connection | What it controls | Common limitation |
|---|---|---|
| Charger / power source | Advertised protocols, voltage/current levels, and total available output | A charger cannot provide a mode or wattage it does not support |
| USB port | Connector-level current, data/power role, and optional USB PD capability | Two visually identical USB-C ports can expose different charging features |
| Cable | Current carrying capability and support for the requested power level | The cable can cap charging even when charger and device support more |
| Device | Maximum accepted power and supported charging protocols | The device requests only power levels it supports |
| Negotiated protocol | Determines which mutually supported charging mode is actually used | If charger and device do not share a protocol, charging falls back to a lower common capability |
| Shared charger budget | Determines how multiport chargers divide total output | Connecting additional devices can reduce power available to one port |
USB charging articles
Explore USB charging guides covering chargers, power delivery, laptops, multiport setups, charging speed, and common power compatibility questions.
10 Best USB Charging Stations for Phones, Tablets, and More
Best 45W USB Chargers for Fast Charging
Best Multiport USB Wall Chargers for Fast Charging
Can You Charge a Laptop With USB? Ports, Power, and USB-C
Can a USB Car Charger Drain Your Car Battery? What to Know
