Designing Power supply with EMI & PI filters

[bkar]

I read that harmonics is bad for electronics appliance. 8-O I try to make a supply which combines both EMI & PI Filter. But I am not good in calculation. It will be good If any body suggest me for further improvement or changes parts value in this schematics....

Its just an :idea: . Please check :arrow:


attachment & Picture.

 

[crutschow]

Without knowing what EMI frequencies and levels you are concerned about, an informed suggestion cannot be make.

 

[D.A.(Tony)Stewart]

For transformer with 9V, 18V, 54VA your sharing one rectifier is not good for efficiency

What are the worst case load currents?
I+5, I+12 DC.

The LDO will reject EMI easily but min.

Drop for chosen regulator I recall is >2v ,

5V will have biggest drop and get hot, so VI drop must be dissipated in heatsink.

 

[FvM]

A transformer DC supply rarely needs a pure differential mode EMI filter. If at all, you'll use an industry standard filter that suppresses both differential and common mode interferences, e.g. to help a sensitive instrument to pass RF burst tests or keep internally generated EMI inside the box.

The shown filter doesn't effectively reduce harmonics by it's high cutoff frequency, and you don't need a harmonics filter for a low power transformer supply.

The secondary LC filters are mostly useless. They can also cause unwanted oscillations during load transients or power-up. A sufficient filter C is state of the art.

 

[bkar]

Dear FvM,

Thanks for the valuable reply.So you suggested that the above circuit does not required secondary LC filters & EMI Filter. Then could you please suggest the value of PI Filter that would I used to the circuit at most 18 hours with 5V 1.3Amp load?