Converter is simple boost design. Controller have feedback about charger current value and find so duration pulse of PWM of boost, that set maximum charger current. This is variant of maximum of power point tracker. Also controller indicates value of charger current and output voltage above 5.6V. Maximum output voltage is limited on 6.2V by two Zener diodes, 1.3W every diode. In idle work (work without charging phone) controller check output current through Zener diode and indicate level above 320mA by blinking voltage led.
Inductor must work with 1.5-2A peak current, because the best variant of core is iron powder (CoolMu etc) ring (computer power supply output filter, some automobile phone charger) 12-15mm external diameter.
This design can good work with solar battery with 2-3V output and other power sources. Converter don't have current limit, because energy source must be power limited (1.5-3W).
converter circuit.pdf
converter board.pdf
converter mount.pdf
converter_program.zip
