Can you help me? I want to limit the input voltage. If the line voltage change. So that the output has always been a 20V. Just in this scheme, the output voltage 30VDC (U4+D13=30,2V). I decided if I'm have 20V, then i need replace the U4 and D13 (18+2,4=20,4V). I was wrong? The output voltage of 20V was enough for me. It also surprised me. I think D7 not needed. Am I right? Or, maybe, you advise me another way in my situation. I read this and some similar forum almost 2 weeks and dont know what to do. Thank you anyway.