I am planing to design forward off-line switching power supply using UC3842 with the following ratings:
Input: 100 -240v
outputs:
12v 3A
5V 250MA
The problem is that the transformers available in the local market don't have any listed specifications ( Core material ...etc) they are E type ferrite this is all I know so is it possible to do the design without knowing the transformer specifications for example by trying different frequency ranges and else.
P.S: I will be using this smps in inteligent NiMH charger circuit using PIC microcontroller
You can do the design based on a typical grade ferrite, such as the 3C85, from Ferroxcube. If you are going to run it at 100kHz or so, I think you will not have any problems. Keep the flux swing low and you will be fine, even though the actual ferrite may not be as good.
But if the transformers seem relatively new, then it's hard to imagine that the ferrite used in them is poorer than the 3C85.
i am designing smps power supply for output of 5v/1A . can any one give specifications for transformer to be used like turns ratio or name of transformer to be used...
I am planing to design forward off-line switching power supply using UC3842 with the following ratings:
Input: 100 -240v
outputs:
12v 3A
5V 250MA
The problem is that the transformers available in the local market don't have any listed specifications ( Core material ...etc) they are E type ferrite this is all I know so is it possible to do the design without knowing the transformer specifications for example by trying different frequency ranges and else.
P.S: I will be using this smps in inteligent NiMH charger circuit using PIC microcontroller
Looking for a transformer for smps can be frustrating, but if you know where to look then you should be able to find something. The main specifications that get left out are the saturation properties, but if you can find that then you shouldn't really need to worry about the core material or shape. Where have you been searching so far?