Flyback converter output inductor

[francis29]

All comparisons between Flyback converter and forward converter says that flyback converter don't require output inductor as in forward converter. But output inductor is used in flyback converters (ex. Power integrations pi expert designs).
why is that??

 

[Akanimo]

Hi francis29,

Flyback converters can be designed without an output inductor but having an inductor in the output filter makes for better filtering (though with second order transient response).
If you want to build one, you can do without an inductor in the output filter.

Just in case, you don't have to think of modifying a pi expert design for you are likely going to spend more time doing that than you'd spend learning to design one from scratch.


--Akanimo.

 

[smijesh]

Forward converter topology required output inductor “ when switch turned off the transformer output current become zero this time output inductor provide continues current to output) but fly-back topology not required output inductor because energy transferring to secondary when switch turns off.

In power integration circuit they used inductor in the secondary side as an LC filter(Pi filter of parallel LC filter). This second stage LC filter reduces high frequency switching ripple at the output of the power supply

 

[francis29]

So in forward converter it is energy storage and in flyback it is simply a low pass filter right??

 

[schmitt trigger]

So in forward converter it is energy storage and in flyback it is simply a low pass filter right??

Exactly!
It all depends on the application and the budget allowed for the power supply section.

I've seen perfectly good circuits without any LC filters.

On the other hand, if your project displays video, it is useful to include a LC post filter. The switching harmonics may mix with the higher video frequencies and produce a "beat".
Depending on the frequency and intensity, beats can be very annoying to watch.

 

[treez]

In the flyback , the "output inductor" is actually the secondary of the flyback.....as the flyback "transformer" is actually a "coupled inductor".

The inductor sometimes seen at the output of a flyback (or any other smps), is called a "filter inductor".