Hi guys, I am new to electronics and to this forum, I was trying to build a good quality bench power supply using LM317T which is capable of 0 to 15v and up to 5A with current limiting function. I based the design on the LM317T using op-amp LM301A and pass transistor MJ2955 that I found from the IC's application note. I built the circuit and it works relatively fine except for the minor voltage drop when a load is connected. But as I increase the load higher and higher the voltage drop becomes higher and higher and at times the MJ2955 keeps burning out and suddenly output voltage rises to 26/27V!. I tried using a lower gain PNP/2N2905 coupled with 2N3055 and some resistors in place of the MJ2955 which reduced the likelihood of burning the transistor but the voltage drop was still there and the 2N3055 got burnt out at the end. Please help me figure out what's wrong with this circuit, thank you.
57.3 KB Views: 54
20.2 KB Views: 50