The standard USB voltage is typically 5V (Volts). However, the current (amps) can vary depending on the USB version and charging protocol used.
USB Voltage and Current Specifications
Different USB standards support varying levels of current at 5V, and some USB-C implementations use higher voltages via USB Power Delivery (USB PD). Here's a breakdown:
| Specification | Voltage | Current | Notes |
|---|---|---|---|
| USB 2.0 | 5V | 500mA (0.5A) | Standard for older devices. |
| USB 3.0 / USB 3.1 | 5V | 900mA (0.9A) | Offers faster data transfer and more power than USB 2.0. |
| USB Battery Charging (BC) 1.2 | 5V | 1.5A | Designed for charging devices. |
| USB-C Current Mode (non-PD) | 5V | 3A | Requires a USB-C cable and compatible device. |
| USB Power Delivery (USB PD) via USB-C | 5V-20V | Up to 5A | Can negotiate higher voltages (e.g., 9V, 12V, 15V, 20V) for faster charging. |
Explanation
-
USB 2.0 and 3.0: These are the most common USB types and generally provide 5V. USB 3.0 provides slightly more current (0.9A) compared to USB 2.0 (0.5A), allowing for faster charging and data transfer.
-
USB Battery Charging (BC) 1.2: This specification is designed specifically for charging devices, allowing for a higher current of 1.5A at 5V.
-
USB-C: USB-C connectors support higher power delivery, with some devices supporting up to 3A at 5V using standard USB-C cables.
-
USB Power Delivery (USB PD): This is a fast-charging protocol that allows devices to negotiate higher voltages (up to 20V) and currents (up to 5A), enabling much faster charging for devices like laptops and smartphones. USB PD always uses a USB-C connector.
Therefore, while 5V is the standard USB voltage, the specific voltage and current a device receives can vary depending on the USB standard, the charging protocol, and the capabilities of both the host device (e.g., charger, computer) and the connected device.
