The Step-Up takes advantage of protocols called PD (Power Delivery) and QC (Quick Charge) present in USB power sources. These protocols allow a device to request a certain voltage (5V, 9V, 12V and even 15V or 20V in some cases) from a USB port. A Step-Up Power Tip connects to the power source, requests the voltage needed by your gear, and supplies it. Step-Up handles up to 100W - however, will only deliver what the PD / QC Source it's connected to can provide, so you do need to check the spec of your power source.