High gain power converter comparison

[ljy4468]

Hi all

I've a question about high gain power converter. i'm just curious about this.

Simply, we use boost converter for step-up, however when gain need to be larger, (about 30~40x )
we should consider coupled inductor boost converter (aka tapped inductor boost converter) for obtaining high gain.

Now I have a question.
How about using flyback instead of coupled-inductor boost converter?
First, MOSFET voltage stress (peak) at drain would be higher by VIN voltage.
Second, gain would be a little bit smaller than coupled inductor boost converter, but it can boost 30~40x with proper turn ratio.

I think the drawback of using flyback for high gain is above two factor. do you have any idea of another drawback with using flyback?

Thanks in advance.

 

[FvM]

Boost converter and flyback converter are essentially the same.

I don't think that "gain" is a usual technical term for the step-up voltage ratio.

 

[ZekeR]

Boost converter and flyback converter are essentially the same.

Indeed, except that flyback converters are somewhat less efficient (since all the power must be delivered strictly by energy storage in the inductor, whereas in a boost some of the power that flows to the output needn't be first stored in the inductor).

ljy4468,

You can make a coupled inductor boost converter which has a turns ratio between primary and secondary. Voilà, best of both worlds. One thing to keep in mind, though, is that most flyback inductors are designed to withstand high voltage between primary and secondary, while most coupled inductors are designed not to. Therefore, most coupled inductors will naturally out-perform flyback inductors for non-isolated apps like this.

BTW, the "gain" of a power converter is actually called its "conversion ratio." People don't call it gain.