PIC24 driving FETs for PWM signals to LEDs

C

cyrusthevirus

New Member

• Jul 22, 2009

• #1

I am trying to design my first circuit. The purpose is to drive 100 LEDs via PWM through four different channels on my PIC.

The questions I have is can a PIC24FJ64GA002 drive 4 output channels with a PWM signal to drive a logic FET feeding strings of LEDs?

The PIC specs can be found here: **broken link removed**

The PIC is supplied by a 3.3v.

Thanks for your help

 

blueroomelectronics

Well-Known Member

• Jul 22, 2009

• #2

How are the 100 LEDs connected? Series, parallel?
Post a schematic.

 

C

cyrusthevirus

New Member

• Jul 22, 2009

• #3

See the attached circuit

 

Attachments

• PIC24_4.jpg

  76.5 KB · Views: 643

blueroomelectronics

Well-Known Member

• Jul 22, 2009

• #4

What power FETs are you using?
You could use a pair of TC4427 (dual FET drivers) to drive them.

Personally I'd skip the LM317 and just use a suitable resistor in each LED chain.

 

C

cyrusthevirus

New Member

• Jul 23, 2009

• #5

The purpose of the LM317s are to protect the remaining strings of LEDs if one string goes down.

The power supply each string of LEDs is 24v 3A which is higher than the TC4427 is rated.

I am going to search for a dual FET which is rated for 4A.

 

C

cyrusthevirus

New Member

• Jul 23, 2009

• #6

Okay I found the TC4425 which is rated at 3A and has a minimum input votage of 2.4 V.

I can rearrange my strings so they work from a 48V 2.2A power supply which would be in the range for the TC4425.

Thoughts?

 

blueroomelectronics

Well-Known Member

• Jul 23, 2009

• #7

The TC442x are designed to drive a power FET. I'd just use it to drive a high power FET like the IRF510 or find a ultra low RDS on MOSFET (you may not need a heatsink)

 

C

cyrusthevirus

New Member

• Jul 23, 2009

• #8

Okay not exactly sure what I am looking for, but I found an ultra low RDS (ON) MOSFET. Here is a link on digikey: Digi-Key - IXTP220N04T2-ND (IXYS - IXTP220N04T2)