“This project provides 12V output from any USB power source, like PC USB port, USB adapter or power banks. LM2577ADJ boost converter IC is the heart of the project. The IC can handle load up to 800mA, it’s advisable to use only 200mA load on output to be on the safe side. The LM2577 are monolithic integrated circuits that provide all of the power and control functions for step-up (boost), fly back, and forward converter switching regulators. The device is available in three different output voltage versions: 12V, 15V, and adjustable. Requiring a minimum number of external components, these regulators are cost effective, and simple to use. Listed in this data sheet are a family of standard inductors and fly back transformers designed to work with these switching regulators. Included on the chip is a 3.0A NPN switch and its associated protection circuitry, consisting of current and thermal limiting, and under voltage lockout. Other features include a 52 kHz fixed-frequency oscillator that requires no external components, a soft start mode to reduce in-rush current during start-up, and current mode control for improved rejection of input voltage and output load transients.
Default output is set to 12V output, however Output Voltage is adjustable using R2 and R3. Refer to datasheet of LM2577ADJ for more info. Output Voltage Formula VOut=1.23V (1+R2/R3) (Read Data Sheet for more information about Inductor value, Capacitor, Feedback resistors, Output current and voltage)”