Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

[SOLVED] Forward type XFMR from PE

Status
Not open for further replies.

CataM

Advanced Member level 4
Joined
Dec 23, 2015
Messages
1,275
Helped
314
Reputation
628
Reaction score
312
Trophy points
83
Location
Madrid, Spain
Activity points
8,409
Hi everyone,

I need a Forward type XFMR rated for 30V in the primary, 100kHz, Npri/Nsec=6, Isec>5A.

I found the PA3856.001NL which almost suits.. the problem is the frequency.

How can I know if the XFMR from Pulse Engineering rated at 200kHz will saturate at 100 kHz if I do not know what ferrite they are using ?
Can anyone tell if it is safe if I use this rule of thumb to estimate the saturation flux density: Bmaxworst case conditions given by manufacturer design/Bsat=65% ?

Worst case conditions given by manufacturer: Vin=57V, 200kHz, D=50%.

Any comment is appreciated.
 

Worst case conditions given by manufacturer: Vin=57V, 200kHz, D=50%.
Where do you see D=50%? Duty cycle for rated output voltage is about 0.35 with 57 V input. You get the designed flux at 100 kHz with half the output voltage.
 
  • Like
Reactions: CataM

    CataM

    Points: 2
    Helpful Answer Positive Rating
O.K. You are correct. I was mistaken.

I see that they are providing the K1 factor but they use it for the Flyback. Are they using the same core material for both Flyback and Forward ?
 

I'm quite sure both transformers differ only by air gap. If the flux is below saturation, half frequency may allow up to 50 % flux increase with constant loss, but not 100 %.
 
  • Like
Reactions: CataM

    CataM

    Points: 2
    Helpful Answer Positive Rating
I'm quite sure both transformers differ only by air gap
Yeah they are... the core loss is calculated with the same parameters for both topologies.
By the way, Bmaxmanufacturer worst case conditions/Bsat=(2773.05 gauss /2)/2700 gauss~50% .. close to my initial assumption of post #1.
 

In a fwd converter at 100Khz, the peak B of the AC flux swing should be 100mT or less, so 0-200mT and back to near zero is a an AC flux swing of 100mT, pushing harder assumes a very good core material ...
 

In a fwd converter at 100Khz, the peak B of the AC flux swing should be 100mT or less,
I think that is relative to the specific application.

The referenced XFMR in worst case conditions given by the manufacturer has 277.3 mT swing, respectively 277.3/2=138.65 mT peak, which gives about 245mW core loss.
That core loss seems reasonable, taking into account that it is a XFMR rated at 50W.
 

Ah well for 50W, you may well get away with it - esp if ambient < 30 degC ...
 

Also contact pulse. I reached out to them once and was pleased with a good honest response from a real engineer. Now they’re high on my inductor supplier list (next to coilcraft who has the best website).
 
  • Like
Reactions: CataM

    CataM

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top