Help me understand how does a SMPS work

Hi everyone,
I have a question about Switch Mode Power Supply(SMPS).i want to know that how SMPS works.I have read from one of the site which state that

"Switched mode power supplies or SMPS as DC to DC converters operate at 20 Khz or higher and utilize the energy stored during one portion of its operating cycle to supply power during the remaining segment of its operating cycle. It does however, suffer significantly in the ripple regulation it is able to maintain."

i can't understand what does an operating cycle means.
Is SMPS is off for a certain period of time and during this off time capacitor or any other element give votlage to load?
Or i am wrong.
please clear this.
And what is the concept of frequency in this means 20khz.

Re: question about SMPS

There is many type of DC-DC SMPS but basically the concept would be store some energy and then release a portion of this energy to the load, what is different from model and model is in what way and how this operation is performed.
Some SMPS have a time interval where there is direct power flow from input and output then in this way load was powered from source and also storage elements inside the converter will charge energy (e.g. Buck), other topology don't allowed a direct transfer of power from source to load but power will be stored first in magnetic element and then released to load in subsequent phase (e.g. Flyback).

Frequency is not a fixed parameter, there is SMPS converter which can work also up to MHz (resonant topology) and also there is other one that is able to work only to a few kHz (IGBT converter for very high power output), frequency is defined from several parameter, mainly from power that converter has to manage, device used to make the switch, EMI consideration, efficiency, control scheme (some converter can work with fixed frequency and variable duty-cycle control, other have variable frequency with constant on-time or constant off-time, ...).

SMPS is a really big and very nice field of electronics...

Hope this help.

Cheers
Powermos

question about SMPS

https://en.wikipedia.org/wiki/Switched-mode_power_supply

Re: question about SMPS

Thankx alot tekut and my_books.
It helps me a lot.