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 Post subject: DC to DC Boost Converter "Adding More Filter Capacitors"
PostPosted: Oct Sun 20, 2019 5:28 am 
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Joined: Jan Mon 17, 2011 2:10 am
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Location: Revere,Massachusetts U.S.A.
Hi Folks, A couple of questions I have a boost converter and I understand the supply has a degree of ripple, should I add more filter caps to smooth the output even more ?
Also regarding ground loops, I tried to power two devices from a wall wart and one device failed I understand that both devices share the same ground and that's the problem. "Ground Loop"
Is there any other way of isolating the supply without using a transformer ?

Thank You Tony

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 Post subject: Re: DC to DC Boost Converter "Adding More Filter Capacitors"
PostPosted: Oct Sun 20, 2019 7:06 am 
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You might try simply increasing the capacitance value, rather than adding more caps.

I wouldn't try powering two different circuits with the same supply. You must have more than one wall wart.

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 Post subject: Re: DC to DC Boost Converter "Adding More Filter Capacitors"
PostPosted: Oct Sun 20, 2019 8:42 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2448
Location: Saskatoon
If this boost converter operates at a high switching frequency, then the relatively high inductance and ESR of additional electrolytic capacitors probably won't help much. You'll need some kind of LC filter.

Near the bottom of the following page, is info on the filter that I used on my boost converter.
http://electronbunker.ca/eb/BplusSMPS.html


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 Post subject: Re: DC to DC Boost Converter "Adding More Filter Capacitors"
PostPosted: Oct Sun 20, 2019 2:55 pm 
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Joined: Jun Sun 15, 2014 5:37 pm
Posts: 398
Location: Montreal, Quebec
One thing I've thought about is whether a tuned circuit in series with the output woukd help.

Making power in a car clean was once a big thing. The material about it including tuned circuuts in series with alternator output.

The same sort of issue is there in switching supplies and the like, and usually high enough in frequency that a tuned circuit wouidn't be too hard.

The real problem is that this only cleans noise on the output line, if the supply radiates interference, the tuned circuit won't help.

I'd also consider small bypass capacitors across the main filter capacitor, as someone said. Snall values would likely be more effective at higher frequencies.

Michael


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 Post subject: Re: DC to DC Boost Converter "Adding More Filter Capacitors"
PostPosted: Oct Sun 20, 2019 6:20 pm 
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Location: Somers, CT
A tuned circuit might help if the ripple was a pure sine wave, but a switching type supply will contain multiple harmonic frequencies throughout the RF range. A CLC pi network filter (cap to ground, series choke, another cap to ground) is essentially a low pass filter by definition. I'd go that route.

Pete

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 Post subject: Re: DC to DC Boost Converter "Adding More Filter Capacitors"
PostPosted: Oct Sun 20, 2019 6:54 pm 
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Joined: Jan Mon 17, 2011 2:10 am
Posts: 223
Location: Revere,Massachusetts U.S.A.
Thank You Everyone for the great help ! I really do appreciate it.
Tony

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