Why parameter KP/PI Expert may be greather then one?
Hi.
According to AN-17/pg.7 => (KRP=IR/IP) or PI-E help topic => "Continuous/Discontinuous Operating Ratio (KP) is the ripple-to-peak current ratio of the primary current."
It's pretty clear what should it be but one simulation calculated KP=1,70!?
For discontinuous mode IR=IP but in any case how the ripple current can be GREATHER then the peak current?
I'm trying to understand the physics behind the construction of the transformer.
Please some help. Thank you.
Comments
Refer to pg.6 of AN-47 (http://ac-dc.power.com/design-support/product-documents/application-not…). The definition of KP varies based on continuous/discontinuous mode of operation.
I suppose KP=1 and KP>1 means the same.
Thank you.
Best regards.
Hm, I must correct myself.
According to the link you sent "the value of KP should be in the range of 0.3 < KP < 6".
If KP>1 (figure 7a) KP=KDP=[(1-D)xT]/t.
Thank you for this answer. Now I can continue to simulate with PI Expert with more knowledge.
Best regards, Zeljko.
Hi.
The textbook definition of Kp is between 0 and 1 (anything at 1 is discontinuous). We've slightly modified the definition (AN-17 is very old), and nowadays we give a value that can be above 1 to indicate how far away we are from critical conduction mode (Kp=1.0).
You can take a look at our definition of Kp here: http://ac-dc.power.com/design-support/product-documents/application-not…
Take a look at figures 6 and 7. Let me know if you have doubts.