Does anyone know how to use a QC 3.0 quick charger to control 12vdc instead of mains

the one i have my eye on is the FAN6290QF
heres a schematic from its datasheet


from the looks of it, its throttling the output of a flyback transformer, i doubt its regulating through PWM using just that Cout for maintaining a clean output, i think its more likely that the flyback is being controlled based on how much it can output, oddly though theres no interaction between the two controllers.


Anyway, i want to know how to control the FAN6290QF to take 12VDC and control a step down converter, or boost converter, or heck, even just switch between a 5v, 9v and 12v fixed power source, for the purpose of USB quick charging.
My end use is building a battery back quick charger, so, i wont have any mains to work with, not that i would ever consider using mains anyway.

At very least id like to understand how this controller achieves the regulated output? I cant see it stepping down a 12v source because in the event of a failure that would mean that the default output would be 12v, which would blow any non QC compliant device plugged into it.


-edit-

it just occured to me that in this schematic, the flyback output is directly connected to the to the the USB output. How does that even work?

jpoopdog said:

oddly though theres no interaction between the two controllers.

Click to expand...

Just a quick comment - I've not looked at the datasheets for these parts or fully absorbed what you're trying to do - but there is an optocoupler providing control from the 6290 to the 602. You may have overlooked it as the two sections are drawn separately.