LNK306 unstable with microcontroller 3v3

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Hi, I'm design power supply transformeless with LNK306GN, using LNK schematic default Vo=12Vdc projected to 320mA, inductor 1,5mH 0,5A. The input stage with Full wave with 1 capacitor input 10uF/400V eletrolytic, but when substitute the 10uF/400 for 10nF/400V the output voltage at regulator Vo=3v3 the microcontroller seems me working good. Because when use 10uF/400V the circuit  microcontroller to interface a dimmer AC, it seems the LNK was restart, but measuring with multimeter Vo of regulator and Vin appear that are ok and stable, but the microcontroller unstable.

 

A current topology that my PCB is buck converter.

 

I've also tested it using another topology with high-side buck optocoupler and the same problem continues.

Also tested several resistor to pre-load, but did not work.

 

 Any ideas, to solution the unstable with microcontroller? 

 

Vin AC - 220V

Freq. - 60Hz

Rbias - 2k (two resistor 1K in series smd1206)

Rfb - 12K 1% (smd1206)

Cbp - 10nF/50V (smd1206)

Cfb - 100uF/16V

Dfb - 1N4005

L - 1,5mH to 680uH (tested both and also 470uH)

Co -  100uF/16V

 

Regards,