Help with STCS2A LED linear driver

[aiq25]

Hello. I'm trying to design an LED driver using the STCS2A chip from ST Micro. I would like to use this chip primarily because of it's size. I'm hoping with the bigger size I will be able to solder the chip myself. I'm designing a PCB using Eagle CAD and I just wanted to post my schematic to get some feedback on it since I'm still a newbie in electronics. I'm still learning how to use Eagle CAD, so I don't have the PCB ready yet. I had to add the chip package and symbol to Eagle CAD. I'm not sure if the chip package is modeled correctly, so I plan on printing out the PCB and checking the sizes before trying to get a PCB made.

Attached is my schematic. I'm thinking of adding a fast-acting fuse to the LED+ line to protect the LED's from high current. I'm planning on using some 10W multichip LED's to test the board. The multichip LED's have a Vf of 9-12V and If of 1050mA. I'm planning on using 3 LED's per driver. I have 6 LED's I would like to use. The DC power supply I'm thinking of using the Genssi 36V DC 9.7A 350W Regulated Switching Power Supply (not sure if this is a good choice, the reviews on Amazon look positive).

Ultimately I will be using these drivers for an LED lighting system I'm building for my saltwater aquarium. I will also replace the LED's with Cree or other quality LED's after testing the system. I ordered some Chinese LED's from eBay to do test on and see if the system works.

I know I could buy the drivers and power supply but I would like to build my own driver to get some experience in getting a PCB made and in electronics in general.

[mij59]

Hi,

The STCS2A is a linear regulator, dependent on the total Vf you'll need to dissipate at lot power.

Worst case scenario:  Vf =9 V, total voltage across the led's 27V , the voltage across the regulator is  9V.
Power dissipation of the  STCS2A (9V*1.05A) = 9.45 W, so you'll need a heat sink.

If Vf =12V  the regulator won't work because the voltage across the regulator needs to be 0.58 V (typical) or more.

You may have a look at switch mode led drivers

[aiq25]

Hi,

The STCS2A is a linear regulator, dependent on the total Vf you'll need to dissipate at lot power.

Worst case scenario:  Vf =9 V, total voltage across the led's 27V , the voltage across the regulator is  9V.
Power dissipation of the  STCS2A (9V*1.05A) = 9.45 W, so you'll need a heat sink.

If Vf =12V  the regulator won't work because the voltage across the regulator needs to be 0.58 V (typical) or more.

You may have a look at switch mode led drivers

I never really considered the power dissipation of the chip due to the total voltage across the LED's. I guess I will have to switch to a switch mode driver. I think I will go with the LM3406HV. The extra voltage input will be good, in case in the future I want to add more LED's to the array. I will need to change the schematic and the design. Thank you for replying.