led driver circuit ideas

[gungor]

Hi All,

I have a 5V input. I need a circuit to drive 40 LEDs connected in parallel. Maximum current will be 800 mA (20 mA/LED). LEDs will open at 2.4 V and maximum brightness is at 5V. It is needed to control brightness in maximum 32 steps.

So I need a converter with a 5V input, having output variable between 2.4 to 5V in maximum 32 steps.

I have thought of:

Putting a mosfet between 5V and anode of leds and driving gate by pwm.

My question is:
Is this a feasible approach? What are the critical things for this implementation?
Do you have other suggestions?
Thanks in advance.
Regards, Gungor

 

[oh_jani]

use 6.8R risestance in series to flow of current limt to maxmum 800mA

 

[cheolim]

Hello gungor

In order to comment,what is Vf of LEDs. Actually no single LED's Vf can bear 5V.

Good Luck.

 

[gungor]

vf is 2.4v. thanks.