I'm going to be using a LM2679 regulator for a switching power supply that outputs 5V as 5A, but the question I have is for the input for the regulator. If I use a transformer and bridge retifier as the DC input for the regulator, what does the transformer need to be rated at? Do I have the option to use any transformer as long as I have a minimum of 25VA of power? What about the bridge rectifier after the transformer, does the voltage/current rating need to match the transformer?