I have made a portable device charger with a 5 volt voltage regulator(7805-TO220 package),a 9 volt battery and a few capacitors.The problem is,when I connect the charger to a certain device(whose original charger outputs 5 volts and 2A) and the device starts charging, after a few minutes,the image starts flashing and then it shuts down,then the start-up screen appears,then the screen turns black and so on a few times,then it shuts down completely and remains in this state.I connected the circuit to another device whose original charger outputs 5,1 volts and 700 mA and all works just fine.
simulate this circuit – Schematic created using CircuitLab
Why does the first device behave this way?
I don'think it's about the voltage or current.
The 9 volt battery is a Varta High Energy model-6LP3146. EDIT:I noticed that when charging the second device,its battery drops after a while,whether discharging on its own or being discharged by my charger(I added a diode between the output pin of the regulator and the positive terminal of the device,so it's unlikely).
Answer
You don't mention what case style of 7805 you have. If i was guessing you are using a TO220. That case can only support up to 1A output current and even then requires substantial heat sinking to do so. Some 7805s had thermal protection and would shut down if overheating. Check the voltage to the device when it shuts down. Perhaps the voltage drops out.
Also you cryptically say that it's a 5v device. If i also had to guess it's a USB device. Some USB devices require that an identified is detected on the data lines to announce that the device is connected to a charger. For example my HTC phone charger shorts the data lines together. Also my Galaxy tab doesn't like my HTC charger because Samsung uses a different scheme to identify the charger.
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