Buffer capacitors' role in boost power supply design?

Question

In the power supply design, there are always smaller value capacitors placed at the output.What is the main role played by these capacitors in the module? Check the screenshot attached and I am referring to C7.

schematic

^{simulate this circuit – Schematic created using CircuitLab}

With smaller capacitors, you can create a mechanically-smaller loop, and reduce the inductance (perhaps greatly).This reduces the stored energy in a parasitic path, and reduces the amplitude of parasitic ringing voltage. — analogsystemsrf, Feb 01 '19 at 15:13
overly-short explanation: one is built for speed (little one), the other is for power (big one). — dandavis, Feb 01 '19 at 20:24

score 5 · Accepted Answer · answered Feb 01 '19 at 08:29

That is done because the 100 uF capacitor isn't very "good" / doesn't work very well at higher frequencies. The 100 nF is much better at those frequencies, but has a smaller value so does not work for lower frequencies. The 100 uF capacitor takes care of those lower frequencies.

By using these two in parallel we create a "better" capacitor that works at both low and high frequencies.

It is explained in more detail by Dave from the EEVBlog in this video.

Buffer capacitors' role in boost power supply design?

1 Answers1