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I need help on how to reduce this ripple at the output of my converter. I already have a 1uF x8 capacitor at the output, butI am still getting loads of noise.

Can you help with the best method to have at least 5 to 10% ripple?

enter image description here

The green is my switching frequency at 500kHz and the blue is my output.

Regards,

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  • \$\begingroup\$ I'm having trouble reading the horizontal scale. What the time duration of the blue ripple/ringing? And what happens at the left of of the trace? Is that the power supply turning on? \$\endgroup\$
    – SteveSh
    Commented Oct 10, 2022 at 16:09

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It isn't ripple as such; it's overshoot. The part of your circuit that regulates the output voltage to (circa) 750 volts is a little unstable. You need to probably increase the phase margin possibly with a little lead compensation. Unfortunately, without a schematic (the bread and butter of circuit design) I can't advise you how to fix it specifically.

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Your supply has some overshoot. This isn't an issue with bypassing (although it has some influence), rather, it's an issue with the control loop.

Without knowing what kind of converter it is (current mode, voltage mode, COT, etc.) it’s hard to give a precise, prescriptive answer to your issue. Generally, you will need to modify your feedback network. There's different types depending on the regulator in use.

If you have access to Spice or similar, this would be a good time to use this tool to experiment with the feedback. Here’s a slide deck that introduces some concepts: https://www.onsemi.com/pub/Collateral/TND349-D.PDF (full disclosure: author is here on EE-SE as Verbal Kint.)

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  • \$\begingroup\$ Thanks so much for your comments. I have a bit of an idea about the issue, but how to resolve it I am having a hard time finding. Please keep in mind that this is an open loop DC/DC converter H-bridge with a low and high side and an inductor between the SIC MOSFETs. This is an internal project. It would be hard to post it online. Any help would be appreciated. \$\endgroup\$
    – ikenna
    Commented Oct 10, 2022 at 18:31
  • \$\begingroup\$ You can see the difficulty here. Without feedback, the output will tend to oscillate. You could try a quick model in Falstad for example and see this. \$\endgroup\$
    – hacktastical
    Commented Oct 10, 2022 at 18:36
  • \$\begingroup\$ It won't overshoot if you turn it on slow enough - slow down the turn on ramp. \$\endgroup\$
    – SteveSh
    Commented Oct 10, 2022 at 21:00

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