P.S supply construction with L200

[Jimidis]

I built the P.S 0-30V 2A shown in the diagram specified in the L200 datasheet. The 741 circuit works as a current limitter. I need to be able to control the limitting current i.e short-circuit the o/p and control Iout using potentiometer P1 to any desired value up to Imax. The problem I have encountered is that when o/p is s.c the L200 internal protection limits Iout to a constant 300mA. I connected low load resistors and noticed that below 8 ohms the power dissipation of L200 goes above 12W (for Vou=12V) and protection limits Iout to 300mA. I use a large heatsink.
Do I need to change the current limitting circuit ? I would appreciate any help

 

[JimB]

Have another look at the datasheet, figure 3 on page 4, the Safe Operating Area.
You will have to reduce the supply voltage if you want a short circuit current of 2 amp.
Consider, 30 volts at 2 amp is 60 watts, the poor little L200 will get VERY hot and destroy its self. So the protection circuit limits the S/C current to 300 mA when the supply is 30 volts.

JimB