I thought about splitting this into many threads, but it might be better to describe the application in full.
So sorry if it is a bit long.
At this stage, I don't know where to start, as there's so many possibilities for the project.
I want to create a controller to power leds for a "flash" application.
The duration of the flash would never exceed 50ms, time between flashes can be up to 2-3 seconds (although shorter is better)
It needs to be battery powered, not too heavy probably 4 AA cells max.
I will need around 3 amps for the leds, 6 would be nice.
I wanted to use an AVR for the timing, charge and constant current for the leds.
To provide the power, I thought about boosting voltage to a capacitor bank,
then using that charge to power the leds in serie with constant current.
(Simmilar to what a xenon camera flash does, so it keeps working even with low bat)
Question is of course how much voltage should I target...
The higher, the more in leds I can put in serie in each string, but probably boost efficiency will degrade.
Also probably depends on the caps I can find...
Can leds can survive to something like 200v ?
Lower voltage means less leds in serie and more strings, so probably more danger of blowing them because of variations in current.
(would also be safer of course)
The next thing is the constant current with the AVR.
If I want to keep the inductor small, then I need high speed pwm to control current.
Is it realistic to control the current with an AVR ADC over a sense resistor ?
That is using a higher PWM frequency than the AVR ADC monitors current to reduce L size ?
Or should I think about using an external opamp with a comparator maybe ?
Maybe I can share the inductor for charge/discharge to decrease the weight, but haven't found any similar design yet.
If you have any advice, recommendations or ideas, you're welcome ;-)