dc dc converter w/wo transformer

[mess123]

What is the actual difference between a dc/dc converter with and without a transformer? I have heard a little bit about bidirectional converter.... Should the bidirectional converter be always with a transformer?

 

[FvM]

The usual purpose of a transformer is either isolation or achieving a large voltage ratio with good efficiency.
As long as you don't tell your requirements, your question can't be answered.

 

[mess123]

I am considering a battery charging application, where power can flow from the battery also. The input voltage is (3-4Volts from fuel cell/PV) and the output voltage of the DC/DC converter should 12V/24V. The power wattage of about 100W.

Also my query is - is there reactive power consumption in the DC/DC converter? If yes, what supplies it?

 

[FvM]

What should be the purpose of running the converter bidirectionally with a fuel cell/PV voltage source?

However, for the moderate voltage ratio, a usual synchronous converter (a halfbridge with an inductor) can be used bidirectionally.

Reactive power is an AC property. It's not defined for DC circuits. Input/Output AC currents, that don't contribute to power
transmission would be described in terms of "ripple".

 

[mess123]

Thanks Fvm,
I probably don't need bidirectional.

About reactive power, I thought the transformer in DC/DC converter consumes reactive power.

 

[FvM]

I thought the transformer in DC/DC converter consumes reactive power.

The transformer magnetization current is supplied by the input filter capacitor.