A/C system

Hello all:

I need help with my A/C system. When I'm around town and use my A/C the whole system takes too much power and my engine dies when I stop the car. On the highway and when the car is moving, the A/C unit works very well. But it just seems that when you turn it on and when you are on idle, the engine fails.

PLEASE HELP, IT'S REALLY HOT IN THE SUMMER!!!

Thank you