Improved Voltage Regulation Under Load

When multiple USB devices are connected - especially high-draw peripherals like external drives or charging phones - the demand on the dock’s internal power can spike. If the power supply were delivering only 5V, any load increase might cause voltage “sag,” potentially leading to unstable or unreliable performance.

By starting with a higher voltage like 12V or 20V, the internal voltage regulators within the dock or hub can more reliably and efficiently step down that voltage to a consistent 5V, even under heavy load. It’s similar to having a reservoir above a village - you’ll have more reliable water pressure regardless of demand.

Greater Power Efficiency Over Distance

Transmitting power at higher voltage and lower current reduces energy loss due to resistance in the wires (which causes heat). By increasing the voltage we can decrease the amperage for the same power, and power loss in the line is directly proportional to amperage squared so even a small decrease in the amperage adds up quickly. Once the power reaches the dock, it's stepped down to the voltages needed for USB ports. This not only enhances efficiency but also makes compact, cooler-running designs possible.

Special Consideration for USB-C Docks

USB-C docks commonly include 20V power supplies, which serve a dual purpose:

• Supplying 5V for downstream USB devices
• Delivering up to 100W (or more) to host laptops via USB-C Power Delivery

With USB Power Delivery 3.1 (EPR), even higher voltages (up to 48V) are supported, enabling future docks and laptops to handle even more powerful devices like desktop replacement laptops or external GPUs.

Will Future Docks Use 48V Power Supplies?

It's likely. While 20V is common now (especially for consumer devices), 24V+ power supplies are widespread in industrial and telecom applications. As high-performance laptops and workstations demand more power, consumer docks may start including 24V, 36V, or even 48V adapters. These would align with USB PD 3.1 specs and simplify designs that support extended power ranges.

However, for now, 20V remains a sweet spot for cost, availability, and compatibility across a wide range of devices.

TL;DR

Higher voltages like 12V or 20V are used for better regulation and more efficient power delivery.

USB-C docks use 20V to support Power Delivery charging (up to 100W+).

USB PD 3.1 EPR opens the door to 48V systems, and while uncommon now, future docking stations may shift to 48V as demand grows.