Electronic – EMC Design Precaution

emclayoutpcb-design

I'm designing a simple circuit which will
charge a big capacitor for 3 seconds,
then pass a 5A current for few microseconds,
then charge again the big capacitor for 3 seconds,
then pump again 5A for a few microseconds, and so on.
And now I test it on a breadboard and I'm convince that its working.
So I started to do a PCB layout.

enter image description here

Questions are the following:

  1. Do I need to concerned on the EMI emission?
  2. What design techniques can you recommend to me or PCB guide layout on this specific PCB.
  3. Any precaution that I need to do in the circuit or even PCB layout?

Best Answer

1.- Yes, sure. You always must attend the EMC performance of your electronics design.

EMC or Signal Integrity, we are talking about the same. Although probably It's a hobbyist-project and you won't need to pass an emission or immunity EMC test in a EMC Lab but EMC is also the noise, the crosstalk or ground bounce and this could be a problem inside your project.

So, yes. For emission you can check: (only a summary)

  • Raise/Fall Time in high speed signals.
  • Layout of high speed. (Changes of layers, loop current...)
  • Possible antennas. (Your connector and your cables could work as an antennas)

2.- It would better if you explain us more about your circuit.

I suppose there is a component that works as a switch. The out of this component we can call it "switch node". In this node the voltage is

$$V = L (di/dt) $$

; V is voltage, L the inductance of the node, i is the current, and $$di/dt$$ is the rise time (or fall time) of change.

This parameter is really important!

Maybe you can:

  • Decrease the rise time. (Could it work slower?)
  • Decrease the voltage (Could you use a lower voltage?)
  • Decrease the inductance in your switch node.
  • Include a snubber (a circuit for absorb the voltage peak).

3.- This question is the similar to 2 isn't it?

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