Traco Power DC converter - Probe the Output

RE: Traco Power DC converter - Probe the Output

Andrew J — Sun, 26 Apr 2020 19:24:55 GMT

This is really interesting to see. I have a Recom isolator on the way and it will be interesting to see what its output is like - something very similar I should think. Thanks for posting this.

RE: Traco Power DC converter - Probe the Output

DAB — Sat, 25 Apr 2020 17:44:03 GMT

Good post Jan.

It looks like somebody just slapped this thing together without much thought as to what happens when the fan comes on.

Just a little bit of planning could have cleaned the design up.

DAB

RE: Traco Power DC converter - Probe the Output

genebren — Sat, 25 Apr 2020 16:55:41 GMT

Jan,

Interesting blog. I have struggled with the noise issues surrounding switching supplies/regulators (similar to a DC-DC isolator). What I find that works best for me is to run the digital side direct from the supply and add a Pi-filter (a ferrite in between two caps to ground) inline to the analog circuit. Typically the digital side of the circuit needs a low impedance throughout the frequency range, but specifically to high frequency edges (with the bypass caps helping out here to supply needed current locally). The inline ferrite creates a higher impedance at these higher frequencies. By filtering the analog side, where you can suffer a higher impedance at the higher frequencies, I have found that this keeps the analog rails cleaner.

Good luck with your experiments!

Gene

RE: Traco Power DC converter - Probe the Output

Jan Cumps — Sat, 25 Apr 2020 14:45:21 GMT

Mini-exercise:

Put the analog part on the +12 V section of the Traco. Filtered by a single 470 µF capacitor.

The fan is on the -12 V part. A 220 µF onthe output.

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I did two measurements again in the AC domain. One without fan. One with fan.

The first capture is zooming out on the noise train. 2nd one drills into the higher frequency within the noise trains:

1: fan off

[View:/resized-image/__size/620x372/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-c9f150c1-e16d-4c2b-8f1a-885977b0d439/3531.contentimage_5F00_206806.png:620:372][View:/resized-image/__size/620x372/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-c9f150c1-e16d-4c2b-8f1a-885977b0d439/5658.contentimage_5F00_206807.png:620:372]

2: fan on

[View:/resized-image/__size/620x372/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-c9f150c1-e16d-4c2b-8f1a-885977b0d439/0882.contentimage_5F00_206808.png:620:372][View:/resized-image/__size/620x372/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-c9f150c1-e16d-4c2b-8f1a-885977b0d439/3124.contentimage_5F00_206809.png:620:372]