Mobile fone 5v 9v and 12v charging from a generator.

[dr pepper]

I have a bicycle trailer that has a dynohub, it generates from 6v 1a to 12v1a depending how fast I'm going.
So I want to make a charger for a smartfone that swicthes voltage to the fone itself rather than the usual other way round where the fone negotiates and requests a swtch in voltage, the other thing is traffic I will be starting and stopping a lot so the power willbe up and down a lot.
Is there any info available for adaptive charging, I;m sure an arduino would do the trick with the right info.

 

[betwixt]

For simplicity, I would just use a LDO linear regulator. They cost almost nothing. If you use one that doesn't leak backwards and produces 5V the phone will see it as a USB charger port.

Brian.

 

[dr pepper]

Done something like that already, well its a switching 5v reg, this is so when the voltage goes up the current draw goes down allowing the dynamo to achieve higher voltages for my lights.
If the fone draws current at 5v a high current like 2 amps it drags the voltage down dimming my lights.
So seeing as the dynamo acts like a current source convincing the fone to charge at 12v allows me to get more power from the dynamo.
One might think the switching 5v reg does the same thing, the problem seems to be the fone initially wants to charge at 5v 2a before it switches to 12v, so the system never 'gets over the hump'. Maybe I need a small power bank that does all the work and gives the initial boost and charge it from the dynamo.