DER-243 REDESIGN
Attn CRUSHER
Attached files. Pls answer prev questions, especially regarding resistors. Ae is same for both cores and power rating for both cores are the same. Regards JDN
note design file has had suffix renamed to pdf, Pls rechange suffix at you end before reading.
Comments
JDN
Hello Crusher
You can access both files from the following links:-
http://www.all-systems.com.au/files/PIDesignSM2.uds
http://www.all-systems.com.au/files/SM1Switcher.pdf
The way I checked the core equivalence is by comparing the Ae for both the RM10 and EER28L core(which the PI Expert chose automatically). The RM10 has an Ae which is only 10% higher than the EER28L. I then took the fact that the RM10 core was used in the DER-243 app note for a 60W design, which it is the same power rating for my design.
Can I manually ask the PI Expert to choose RM10 and see what the turns ratios become? I notice that the components section does list the RM10 core but not when I run PI Expert in automatic mode. Do you have a simple procedure to invoke the RM10 into the design, then I can see the correct turns ratios ?
Hi Unc60,
You have clear instruction how to use a custom transformer core here:
http://www.powerint.com/en/design-support/pi-expert-design-software
Check “Designing with a Fixed PI Device and/or a Fixed Transformer Core” and “Adding a Custom Transformer into the Component Library”
Cheers,
PI_Crusher
Hi Unc60,
See previous answer. Only if the two cores are equivalent you can use the same turn ratio, otherwise you have to choose the closest core from default list and recheck the design. Since you checked and the two cores are equivalent, it is absolutely safe to use the data provided by the design file for the resistors.
When you choose a resistor you have to check a few parameters, not value only. It is important to always validate maximum allowed voltage and power rating (from data-sheet). Check the specifications for any resistor you have questions about.
It is possible to change the design using copper foil instead of quad-filar. Nevertheless, be advised to validate EMI compliance after your first prototype is built, this change could affect EMI signature. Also you made a few references to files you never attached. Only a single PDF file in your last post is available.
Cheers,
PI_Crusher