Discussion: Power-supply circuit operates from USB port
Quote:
Stefano Palazzolo, Senago, Italy; Edited by Martin Rowe and Fran Granville - EDN Get 1.25V to 3.75V from an adjustable regulator Every PC has a USB (Universal Serial Bus) port that can supply 5V±5% at 500 mA for peripherals. Powered USB hubs also provide this power.