Walrus
Well-known member
How would I go about working out the size of choke I would need to reduce switching noise on the output of a
15 Volt 20 Amp 70kHz SMPS?
15 Volt 20 Amp 70kHz SMPS?
Coomon mode chokes
- Thread starter Walrus
- Start date
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Bo Deadly
Well-known member
Presumably the common mode choke is for the input in which case you need to know what the input current is which is not the same as the output. Then find parts that handle double that.
Walrus
Well-known member
No, it's for the output to block the HF switching noise.
It's not going to be very easy putting a CM on a 20A supply!
My rough calculations seem to indicate that I'd need to have something like a 25-50mH choke to have a good rejection at 70kHz.
But they don't exist off the shelf in 20A.
It's not going to be very easy putting a CM on a 20A supply!
My rough calculations seem to indicate that I'd need to have something like a 25-50mH choke to have a good rejection at 70kHz.
But they don't exist off the shelf in 20A.
Bo Deadly
Well-known member
You don't need a common mode choke for output. A regular choke would work equally well. But usually the load creates problems such that a capacitance multiplier would be a better solution. Meaning you can skip the choke entirely. If you describe the use-case and provide the supply model number, I might have better advise.
You should have a common mode choke on the input but even with the lower current at mains voltages, you might have to live with just a really nice line filter.
You should have a common mode choke on the input but even with the lower current at mains voltages, you might have to live with just a really nice line filter.
