USB-C Power Rules Explained (Safe Chargers & Cables)
USB-C can do 5 W or 240 W—depending on cable, charger, and device. Here’s how Power Delivery (PD) actually negotiates voltage/watts, and how to buy safely.
How USB-C PD negotiates power
- Profiles: common voltages are 5/9/15/20 V (and EPR 28/36/48 V for up to 240 W).
- Smart handshake: the device requests; the charger offers; the cable signals limits via an E-marker chip if it supports >3 A.
- Safe by design: power ramps only after agreement—mismatched gear simply falls back to lower power.
What matters when buying
| Item | Look for | Notes |
|---|---|---|
| Charger | Wattage that meets your device’s peak (e.g., 65 W for many laptops) | Multi-port chargers split power—check per-port chart. |
| Cable | E-marked for >60 W; length you need | Charging cables can be USB 2.0 for data and still charge fast. |
| Device | PD support, and whether it accepts charge on all ports | Some laptops charge only on certain ports. |
Myth: “Higher-W chargers damage phones.” False—phones draw only what they need.
Fast-charge brand quirks
- Many brands layer proprietary fast-charge on top of PD—your device still works on any PD charger, just maybe not at peak speed.
- Use the original cable for the absolute fastest vendor-specific modes.
