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Cearmic Vs Bulk capacitors in power supply

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balamanikandan

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hi,

"....To reduce the rms current in the bulk capacitors the ripple voltage amplitude must be reduced using
ceramic capacitors....."

I can understand the purpose of ceramic capacitors and Bulk capacitors.


But I could not understand How Ceramic reduces the input ripple voltage when bulk does not?

it looks like....ceramic acts as a safeguard for bulk. Since ceramic limits input ripple voltage , Bulk handles less ripple current. But both are in parallel.

Please explain the physics behind this.

I referred the application note at https://www.ti.com/lit/an/slta055/slta055.pdf
 

Bulk capacitors are to clean up the lower frequencies. For low impedance at low frequencies you need a large capacitance, but the larger caps have higher inductance too which limits their ability at higher frequency. The smaller ceramic caps have little effect at low frequency, but are lower impedance at high frequency than the bulk caps because of their lower inductance.
 

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