Without the schematic it's a shot in the dark. What Ian said should work it's the easy way to do what I was saying but the hardware needs changes to I said that too.
I just use PNP transistor in the Common Anode pin in the seven segment display.. Now its Okey. But how can I ignore these transistors for reduce the total cost?
It can be controlled through the source code to change the duty cycle of the micro controller?