How the input voltage is step down in a smps?

[ABEL DANIEL]

Is it only depends on the duty cycle(of the pwm).Does the turns ratio have any effect on stepping down?

 

[crutschow]

If you are referring to a standard buck converter which uses an inductor to step down the voltage, then there is no turns ratio since there is only one winding.

 

[ABEL DANIEL]

no im telling about the one that uses a smps transformer??

 

[FvM]

im telling about the one that uses a smps transformer

Good you mention it.

There are also different converter types, may be you are referring to flyback converter?
For the time being, you should assume that turns ratio matters.

 

[ABEL DANIEL]

may be you would recognize what type of converter is it if i upload my circuit here.

i think its the flyback itself....

 

[FvM]

i think its the flyback itself

Yes. You should read a bit about switched mode converters, then you have no difficulties to recognize it yourself.

 

[ABEL DANIEL]

actually that was not my question,i believe...

 

[crutschow]

Actually he did answer your question in post #4. The output voltage depends upon both duty-cycle and turns ratio. Here's some references on flyback converters to help you understand their operation.