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Noise in power supply

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HF_ATL:
Hi all,


I've found a circuit online to reduce the voltage regulator output noise. Please see link below.
I wonder if I can use it with +13.8V instead of +15V and if a 25A load is acceptable (using a 50W wirewound 0.05R resistor). I'm aware of 1.25V voltage drop with 25A load but that is acceptable.
My idea is to filter out as much as possible the 13.8V switching power supply I'm using with my ham transceiver.


Link: https://ibb.co/JCS6YWW



Thank you in advance!

moffy:

--- Quote from: HF_ATL on February 18, 2024, 02:44:07 pm ---Hi all,


I've found a circuit online to reduce the voltage regulator output noise. Please see link below.
I wonder if I can use it with +13.8V instead of +15V and if a 25A load is acceptable (using a 50W wirewound 0.05R resistor). I'm aware of 1.25V voltage drop with 25A load but that is acceptable.
My idea is to filter out as much as possible the 13.8V switching power supply I'm using with my ham transceiver.


Link: https://ibb.co/JCS6YWW



Thank you in advance!

--- End quote ---

I doubt the circuit will do anything useful, you could always try an LTSpice simulation as it's quite simple.

Wolfgang:
The circuit you have here is called a "Wenzel Cleanup Shunt" and is meant for cleaning up noise for sensitive circuits like VCOs and the like, all low power.

When you are prepared to spend 1.25V in voltage drop you might go for a "capacitance multiplier" or a low-drop regulator instead.

What also helps a lot against switching noise is a Pi filter with a large enough inductor.

David Hess:
I agree with Wolfgang; a pi filter would be more appropriate.  A 25 amp pi filter is not trivial, but the alternatives are even more trouble.

Wolfgang:
Probably some toroids (30A types are available) would do the job.
Example: HHBC24W-2R1B0065 from KEMET, thats about 50uH under load.
Filter caps must be either ceramic or low-ESR foil for pulse.

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