This is a follow-up to this thread: https://arstechnica.com/civis/threa...-polarity-of-this-laptop-barrel-jack.1491071/tl;dr I have a laptop but no charger, and I'm ...
This is a 5V to 12V DC-DC step-up (boost) converter circuitry that is especially ideal for the USB powered applications. First of all a USB port has two current supply modes. Before detecting the ...