The standard voltage of the USB interface varies according to different USB versions and types, but in general, the standard USB interface voltage is 5V. The following is a detailed summary of the standard voltage of the USB interface:

1.USB 2.0 and USB 3.0 voltage standards:

The standard voltage of USB 2.0 is 5V.

USB 3.0 supports 5V, 9V, and 12V, where 5V is the standard voltage for USB interfaces, while 9V and 12V are used for fast charging. Note, however, that while USB 3.0 supports higher voltages, not all USB 3.0 devices will use these higher voltages.

2. Voltage tolerance:

The voltage tolerance of a standard USB interface is usually plus or minus 5%, meaning that the normal operating voltage range is roughly between 4.75V and 5.25V.

3. Working voltage range:

In many cases, the device can work properly at a voltage slightly below 4.75V, but the voltage should not be lower than 3.2V, otherwise the USB device may not work properly.

4. Special interface types:

For the USB Type-C interface, it supports higher currents and a variety of different voltage levels, including 5V, 12V and 20V, which enables the Type-C interface to provide power support for more devices with higher power consumption. At the same time, the Type-C interface also supports fast charging protocols such as PD(Power Delivery) and QC(Quick Charge).

To sum up, although the standard voltage of the USB interface is 5V, the actual application may vary according to device requirements and interface types. When using USB devices, be sure to follow the device manufacturer's guidelines to ensure safety and optimal performance.