The project is to make a phone charger similar to the free loader.
I have a low voltage supply (0.4) which I am converting to 5V using a charge pump and DC-DC Converter. The problem is that the circuit is unable to supply enough current directly from the source. So the plan is to have a battery which gets charged from the source. When a phone is connected the battery will be used in parallel with the source to charge the phone. The battery will potentially be charged continuously from the source, even when a phone is not connected.
My questions are:
1) What type of battery is best for this type of application? Should I use a battery charge management chip?
2) When a phone is connected and being charged is there anyway to set the source as the main supply and only top up the current from the battery if required.
3) I should probably go for a 4.8V battery as this will still be within the USB Spec. Otherwise it would be a 3.6V Battery and then use another DC-DC converter to boost it to 5 V. (Not very efficient)
Any tips / advice would be appreciated!
Thanks in advance!