MC018 and controlling LED

[FStelzer]

Hi guys,

do you have some experiences with MC018 and controlling LED's? I have 4 LED's with 15W on a 12V system and want to control each LED with a 25 A output.
The reason why I ask is, that I have heard that there are some troubles with the inrush or start current on such LED's - so that the output status from the MC018 turns into "overload" because of the short current overshoot.

Thanks for your help.

Regards,
FStelzer

[pinias]

FStelzer,

I have not used any of the MC018 however from your description, 15W on 12 V  system, the nominal current will be 1.25 amps for resistive loads it is recommended to design 3x your nominal current, for inductive it is recommended to design 5x your system.

a LED is not an inductive load but even with that you are still safe.

now if that was a typo and you meant 150W on 12volts system then that is 12.5 Amps so times 3 it will be 37.5 amps. according with the datasheet of the MC018 the overcurrent for the output is 47.6 amps so you still should be ok.

on the other hand I would try to ramp up the turning of the LED by minimizing the duty cycle and keep it increasing over a few seconds.

I have done that with a MC012 and a SS relay so that I  "dimmed" the  LED of a LIGHT BAR for off road, as far as I remember the LED LIGHT BAR was like 120W or 150W. it did work pretty well.

I hope this helps

[FluidPowerTom]

As far as your question goes with inrush current I have dealt with that a few times.  Inrush current is no joke and will indeed cause an overload status issue.  I had a customer send me a mobile quality LED light that the manufacturer affirms on their data sheet draws just 1A and does not have inrush current.  However, we were having issues with it causing overloads on the standard 3A outputs.

So I hooked it to a power supply through my Fluke meter and put the multimeter on fast mode and set it to hold the max current it sees.  This supposed 1A LED would regularly draw over 3A every power up.  I tried a bunch of power cycles, and sometimes it would draw over 5A.

The solution I've been using is a small circuit element called an inrush current limiter.  It works well but does get warm.

[Marbek_Elektronik]

There is a difference between PWM output and Digital Output.
Please test digital ouput.
I have read, pwm Output overcurrent is around 5A and it is electronc controlled.
Digital output is only controled by the IC itself and it depends on the temperature of the IC.
This ICs can 17A, says the datasheet. I have opened one defect controller and looked to the ICs....

[FStelzer]

Thanks a lot for your answers!
 
I am at the machine on monday and will try to control these LED's - I will let you know if everything works or not


Regards,
FStelzer