Hello Could anyone please help me understand the signficance of the diode D3 and maybe D2 in the below application circuit. I have a circuit that has D3 at 15V and the position is moved after D2, but the direction is the same. Also i have two secondary windings for a bipolar +-12 v output power supply. My Zener diode D3 seems to heat up above 220C. I know its clearly a problem but i cant figure out why. Could someone please explain?