XL6009 5 V → 12 V Boost Converter

Step a USB pack up to 12 V with one chip, one inductor, and a feedback divider you can dial.

Difficulty: Breadboard. Estimated build time: about 45 minutes. Estimated parts cost: about US$5.00. 6-part bill of materials with live supplier pricing. A bench boost converter built around the XL6009, a $0.50 monolithic step-up regulator that takes any input between 3.3 V and 28 V and produces a regulated output up to 60 V at up to 4 A switching current.