The voltage output by the computer USB port is 5V that has been stabilized. If the electrical device is powered by 5V, it can be powered directly without adding a voltage stabilizing circuit.
If the electrical equipment is not 5V, you need to add a DC-DC converter to change the 5V to the required voltage. Because the voltage of the USB port is low and the output current is limited, the power of the device powered by the USB port should be less than 5W.