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