I have a problem about making an negative regulator, which have parameters following
+ Vin = 40 V
+ Vout = -12V
+Iout = 1A
I need schematics not use transformer. Help me please
Thank you every one seeing the thread!!

 

use a LM7912 regulator..

 

Sory, i have only input, with is 40VDC. I want to make a negative voltage -12 V from the input without pulse transformer. I need a schematic buck-boost converter.

 

How many outputs do you have? If there is just the single -12V output then the aforementioned LM7912 will do the trick, along with many other devices equally simple and suitable.

If you are using the input for a positive output then sorry kid, it cannot be done without a transformer (for isolation) inside a switching converter.

 

I found an application of LM 2576. but it's starting current too high, about 2A. and efficient low, about 60 %

 

Hello,

You already have a thread for this :
http://forum.allaboutcircuits.com/threads/help-me-about-negative-regulator.105439/

One is enough.

Bertus