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Suppressing unwanted spikes in DC_DC converters

 
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reshmi



Joined: 23 Apr 2008
Posts: 1
Post23 Apr 2008 14:25   Suppressing unwanted spikes in DC_DC converters
We are designing some DC-DC converter circuits.We have used the boost, Flyback and Sepic configurations.
We have used LC filters and capacitor filters to suppress the switching noise and to meet the EMI/EMC requirements. The noise is getting suppressed by the filter, but there are unwanted spikes at the rising and falling edges which are of considerable amplitude and may cause a problem.( I have attached the waveform that we are getting)
Can anyone suggest a method by which this spike can be either removed or suppressed to a lower value.
[/tex]

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FvM



Joined: 22 Jan 2008
Posts: 1837
Helped: 335
Location: Bochum, Germany
Post23 Apr 2008 19:34   Re: Suppressing unwanted spikes in DC_DC converters
Without knowing the dimensioning of existing filters and the circuit layout, one may only guess how the spikes spread out. It could be, that they simply bypass your filter.
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pinoy



Joined: 25 May 2007
Posts: 31
Helped: 2
Post02 May 2008 12:39   Re: Suppressing unwanted spikes in DC_DC converters
try to add snubber circuit.
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XNOX_Rambo



Joined: 13 Jul 2002
Posts: 424
Helped: 86
Location: Far out, man!
Post02 May 2008 13:50   Re: Suppressing unwanted spikes in DC_DC converters
What type of capacitors do you use in the design?

I have managed to reduce switching spikes from 5 Vp-p to 100 mVp-p
by replacing the output capacitor for a type with low ESR and adding
a 100 nF X7R capacitor in parallel to that.

After the change e.g. the 13th harmonic of the switching frequency was
reduced by 30 dB.

No LC or snubber filter were necessary.

/Ram
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oddbudman



Joined: 20 Oct 2004
Posts: 77
Helped: 8
Post14 May 2008 13:55   Suppressing unwanted spikes in DC_DC converters
It may be caused by the circuit layout itself. what frequency is the converter running at? Is your filtering close to the switcher?

oddbudman
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