I saw this circuit on some recommended YouTube channel and I thought it would be a good start to building a custom PSU, learning some stuff along the way. I would like to keep the circuit analog for now since I'm a newbie in electronics so this seems like a good start. The circuit seemed incorrect so I drew one on circuit lab and now I have a couple of questions from what I have. I used parts that I have on hand since I want to know what I'm doing before getting parts online.
- How does the current/voltage adjustment work? I understand the two transistors are a sziklai pair which should provide a huge current gain from what is set by the zener diode VD1.
- Can I replace VD1 with say, a TL431 which is adjustable? If I can, do I lose R1 or leave it in?
- I did it try the circuit on my own, but used a TL431 instead of VD1, the voltage is adjustable, current is also adjustable but when any load is connected that draws over 50mA, the voltage slumps down to zero and but the current can be increased to ~2A. See the second circuit to see my TL431 addition
- Would I be better off using a mosfet instead of VT1 and VT2?
- Can I leave out the 1K R5 bleeder resistor?
p.s. My transformer is a brick adapter putting out 12V ac from EU's 220-240V Ac. It's rated for 3A but my circuit is intended to put out 1A.