When you turn your wheel the power steering pump gets utilized, and if you watch your RPMs they will go down, it's like engaging the clutch on your AC compressor.. more load on the pump = more inertia that the belt has to overcome to turn your engine. Turning your wheels all the way one way or the other puts the largest load on the pump.. watch your RPM's, you'll see.
Check your fluid.. your car stalls because too much load is put on the engine from that pump, and your RPM slows down too much. If its your pump, replace it.. or just turn up your idle.. or, just dont turn your wheels all the way at ad ead stop.
