8 parallel mini switchers casue bad EMC?

[treez]

hello,

I am making a LED lamp using eight 300mA LEDs.

(It is a re-design of my previous post's circuit)

It will run off a battery with voltage 13.5V.

I dont want all the LEDs to simply come on all at once,
-i want them to come on in succession, LED "chaser" style.

Therefore, i have designed the following circuit, which uses 8 parallel mini switch mode current regulators (one for each LED).
(I will control each LEDs on/off with a PIC interfaced to each of the current regulators)

http://i27.tinypic.com/1z1zsi1.jpg

These will all be paralleled across the 13.5V input.

My question is.................

Will this cause a Bad EMC problem?,

-since eight switchers (albeit ~one Watt each) will be switching away and may "beat" with each other or something, causing bad EMC problems.?

(These mini current regulators are not synchronized and i may end up using a different (constant frequency) controller than ZXLD1362, which is hysteretic mode.)

 

[MacGyverS2000]

Time out... if this is automotive, why all of the worry about EMC in the first place? Exactly what FCC rules are you trying to fit?

Dan - Owner

http://www.Hi-TecDesigns.com

 

[treez]

We are trying to fit specific EMC rules of each of the various manufacturers who we build for.

-they have there own EMC reuirement documents

They are strict EMC standards.

 

[OperaHouse]

I read your other post and immediately thought not another Nightrider. Seems a computer guy like yourself could program a PIC to do the job. "the various manufacturers who we build for".......REALLY! This doesn't even make a good high school project. If you want to get credit for work other people do, you should make a career change to MANAGEMENT.

 

[MacGyverS2000]

Manufacturers do not set EMC rules, the engineers do. Manufacturers do just that, they manufacture, and if one told me my product wasn't meeting their desired electrical spec I'd move to someone who did their job, not mine.

If you're designing this for another company, why are they imposing stringent EMC requirements on an aftermarket automotive lighting component? Who builds It simply doesn't make sense. Building a Knight-Rider style lighting piece is simply NOT a problem that should be taxing a single engineer, let alone a group of 5-6.

There are two possibilities I can come up with here: 1) You're a hobbyist/student posing as an engineer to get our help with the design, or 2) you're not telling us everything, because this simply does not add up.



Dan - Owner

http://www.Hi-TecDesigns.com

 

[OperaHouse]

A high value resistor in series with the gate of a FET will slow the transition down enough that it won't produce EMI. The gate of the FET has enough capacitance to create a RC filter.

 

[treez]

Macgyvers2000:

Your answer is very intriguing.

You are right i am a junior joe.

I dont do our EMC testing, that is done by my boss alone.(and the eventual emc testing house who test to whatever we conform to which i am presuming is EN55022 or CISPR25 or whatever we all have to conform to as i assumed it was worldwide?

Most intriguing was the suggerstion(?) in you last post that afternarket car lights dont have stringent EMC requirements?

The EMC document i ahve here quotes CISPR, ISO, IEC.