DPA design 16W,
Hello,
I am trying to design a SMPS using DPA switch. I have used PIExpert 8.6.0.2 to design the SMPS according to my specificatins, attached schematic of my design(with UV/OV error). The problem is I need both UV and OV protection, but my design fails if I keep the option of UV/OV in PIExpert s/w. I have found a solution for it in Design seminar for DPA http://www.powerint.com/sites/default/files/PDFFiles/seminars/dpa.pdf, page 8-45, adjusting UV/OV ratio.So my doubts are
1) If I do the changes, my design will work? What should be the actual values of components RLS, VZ, R1 ?
2) Can I use EE20 core in place of EFD20 core? What are the possible changes that I need to do in my design?
thanks in advance.
Comments
thanks Traveler, I will try to design the external circuitry for UV or OV.
pritam
I have selected EF20 core from Epcos, with N87 material will it help my design?
http://www.epcos.com/inf/80/db/fer_07/e_20_10_6.pdf
shall I preafer a gapped core or ungapped core?
Thanks in Advance
The bobbin/core geometry is ultimately up to you, your design constraints (physical space), cost, etc.
It looks like the N87 core material is rated up to 500kHz which should be suitable for DPASwitch. The important thing with DPASwitch is to use a high-frequency core material so that you don't suffer from excessive core losses.
-The Traveler
Depending on where you are in your prototyping process, it might make sense to disable the UV/OV feature and test your design to see if it meets your expectations in other performance areas. While you're working on optimizing the power supply design, you could also experiment with ways to implement the UV/OV circuitry and then just piggy back the UV/OV circuitry onto the power supply with some test point connections.
Here is an IC from Linear that provided UV/OV functionality with only a few external components. This is just one that I saw while quickly looking through Digikey. I'm sure there are other manufacturers with similar products.
http://cds.linear.com/docs/en/datasheet/4365f.pdf
-The Traveler
Thank you for the valuable Response
Pritam
The UV/OV ratio is fixed at 1:2.7 when using a single resister. Quickly looking at the PDF you've referenced, Vz and R1 can be used to create a tighter UV/OV ratio. If you need to make it a wider ratio, you might have to come up with an external circuit to control the UV/OV feature. Or maybe just use either the UV or OV feature as descrived in the datasheet but use an external circuit to implement the complementary feature.
For the core material, you want to make sure you're using a material that is inteded to be used with the switching frequencies involved, otherwise you'll suffer from high core losses.
-The Traveler