[SOLVED] bulk capacitor vs bypas capacitor

[lizsagzki]

What is the difference between bulk capacitor and bypass/decoupling capacitor?

I have read that bulk capacitor are usually placed right at the output of the voltage regulator or voltage supply while the bypass capacitor is placed close to the power input of the device.

If I already have a bypass capacitor at the power input of the device, would adding the bulk capacitor be redundant?

 

[ads-ee]

The bulk and decoupling capacitors serve different purposes.

Bulk capacitance is used to help supply a power rail with instantaneous power that exceeds the ability of the power supply feedback loop to react to. These capacitors tend to be quite large as they aren't meant to perform any high frequency power decoupling.

Bypass/decoupling capacitors are needed to allow for local high frequency reaction to instantaneous power requirements of a device.

Finally in a multilayer PCB a core power/ground plan pair can serve as an even higher frequency decoupling capacitor.

 

[lizsagzki]

The bulk and decoupling capacitors serve different purposes.

Bulk capacitance is used to help supply a power rail with instantaneous power that exceeds the ability of the power supply feedback loop to react to. These capacitors tend to be quite large as they aren't meant to perform any high frequency power decoupling.

Bypass/decoupling capacitors are needed to allow for local high frequency reaction to instantaneous power requirements of a device.

Finally in a multilayer PCB a core power/ground plan pair can serve as an even higher frequency decoupling capacitor.

Thank you very much! This makes a lot of sense.
So if a power supply already has a sensing circuit, will that make the bulk capacitor unnecessary? Or is it still good to have the bulk capacitor there as extra precaution?