Blog for students taking ECEN5817 Resonant and Soft Switching Techniques in Power Electronics, ECEE Department, University of Colorado at Boulder, Spring 2012
Sunday, April 11, 2010
Problem 20.5 Verification
I was wondering if anyone got these numbers:
For 2.38A case: Cr <= 3.8nF and Lr < 6.81e-5 H For 0.119A case: Cr < = 0.19nF and Lr < 1.37mH
Please find: R0, Vbase and J2 for both Imin and Imax. Verify that both J2s are less than or equal to 1, which is the ZCS boundary condition(L31_annotated slide 17).
Transformer turns ratio is 1:n (1 is referred to the prim side, n is referred to the sec side). If Vg and Q in forward converter are pushed through the transformer to the secondary side, circuit from L31 slide 12 can be obtained with: V1=n*Vg. From the circuit: J2=normalized inductor current =normalized output current.
But you should get 2 sets of L and C because you have 2 different load currents. Then you select the L and C (from the 2 sets you calculated previously) that will maintain all conditions for both load currents.
I asked because you should only get one set of L's & C's. If you meet the Js<=1 requirement for the max case, this is one condition. Minizimizing the fet current (J1) means that you pick the max Ro given by the Js<=1 inequality.
Also, you have a max frequency requirement and a u requirement. You know J2 so these two conditions should give you an fo value. This combined with the Ro requirement should give you the L and C value.
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8 comments:
Please find: R0, Vbase and J2 for both Imin and Imax.
Verify that both J2s are less than or equal to 1, which is the ZCS boundary condition(L31_annotated slide 17).
Hi Vojkan,
Any hints for J2?
I don't see how to be determined based on actual data.
Transformer turns ratio is 1:n (1 is referred to the prim side, n is referred to the sec side).
If Vg and Q in forward converter are pushed through the transformer to the secondary side, circuit from L31 slide 12 can be obtained with: V1=n*Vg.
From the circuit: J2=normalized inductor current =normalized output current.
Hi Brandon,
I took a different approach and was wondering how you come up with different L & C for each of the cases.
--Aaron
My answers aren't correct.....
But you should get 2 sets of L and C because you have 2 different load currents. Then you select the L and C (from the 2 sets you calculated previously) that will maintain all conditions for both load currents.
I asked because you should only get one set of L's & C's. If you meet the Js<=1 requirement for the max case, this is one condition. Minizimizing the fet current (J1) means that you pick the max Ro given by the Js<=1 inequality.
Also, you have a max frequency requirement and a u requirement. You know J2 so these two conditions should give you an fo value. This combined with the Ro requirement should give you the L and C value.
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