advantage and disadvatnge of AC to DC converter circuit

[pharaon]

Do you intend to connect the fan to the fridge thermostat?

yes so it can make cold air movement inside the fridge

It might be easier to use a mains powered fan instead as mentioned above

i dont't have such one in my city

 

[Cirkit]

Using a plug-in power supply as has already been mentioned would be far safer. You should be able to pick up a small 12V one or order online.