Arduino Based LED driver circuit

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I want to build a 90% efficient microcontroller based LED driver circuit with current range from 25mAmps to 35mAmps with the source voltage of 7.4 volts. How can I make it using my Arduino board.


1.) 24 to 32 LED's.
2.) LED load is of 3 to 3.2 volt.
3.) 7.4 is the source voltage which is charging a 3.7 volt lithium ion battery i.e LED's wil be powered by the lithium
ion battery.
Please help.
 

You don't need a MCU to make an LED driver unless you want dimming control. Furthermore the MCU will be low voltage drive @ 30mA +/-5.

If this current is intended to drive 32 LEDs @ 3.2V you need to convert 3.7 to 100V at 3Watts average load.

We call this a 32 Series or 32S string. Often when voltages exceed 50 Voltages they are put into series/parallel arrays such as 16S2P.

Pls confirm what you want.
 

Thanks for your concern SunnySkyguy.
I have a 7.4 volt solar panel from which i will charge the 3.7 volt Lithium Ion battery. This lithium ion battery has to drive the LED's(32 LED). Please tell me a suitable LED driver which matches my specifications and the corresponding circuit diagram. Microcontroller (arduino) is for other side tasks such as high HCO(high cut off) and LCO(low cut off), battery voltage sensing etc.
 

LiPos have the tendency to explode when charged incorrectly.

1st consider efficiency of 32Parallel LEDs with Lipo charged from **broken link removed** or equivalent

Then consider LDO with series R for each LED. Efficiency is approx 3.2V/3.7 = 86% for LDO

Charger efficiency using 7.4 to charge 3.7V LiPo @ 4.2V is much less. so overall efficiency of 90% is not possible with linear charger. Actually the problem is choice of PVC voltage and battery voltage is too low to make high efficiency.
 

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