not isolated AC/DC converter 3.3V 0.25A

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Hi dear all,

to design the circuit to in the subject ( 230Vac +-15%)

My idea is to use a LNK306G classical configuration fig1 in datasheet.

Is the output requirements possible with this IC? 

Can you help me in this design?

PI expert gave me Cin=3.3uF L=470uH Cout=470uF US1M freewheeling diode.

Are these values correct?

reliability is very important  for me.


Not sure which feedback circuit you are using -- if you are the boot-strap diode coupled feedback configuration you may be pushing it with this at 3.3V. You might try it out and see. If it is not good enough you could try using TL431LV error amp sense on output with opto coupling to feedback pin.. The output of opto would have it's collector tied to BP pin and emitter tied to feedback pin with a 5k resistor feedback pin to source of device.

thank you very much  for your support,

now I'm using the bootstraps diode couopled feedback configuration. But I will evaluate the opto suggestion.

I have 3 questions:

1) at start up I have 5ms of drain current of  1.4A  is this value fail safe for lnk306?

2) can be  this converter compliant with EN55022B in band 30MHz-300MHz?


3) in case of output short circuit  a value of  L=470uH is high enough to avoid ic failure?

thank you very much

kind regards

1. As long as input DC is equal or less than 400VDC it is OK

2. That will depend on your layout for supply and the general system layout and filtering. It is certainly possible to pass so it is probably best to have radiated test with your first layout

3. Yes, this is safe