2.9 d): The use of small-ripple approximation creates the problem that you're seeing (I think). In order to determine the peak inductor current ripple, you will need to find the ripple without SRA method. See lecture 4 slides (annotated version), slides 14-18 for help with this. There is an example for cap ripple, but as the slides mention, a similar process can be used for inductor ripple as well. If everything goes smoothly, you should end up with a relationship between peak inductor ripple and Vg, D, R, L_1, C_1, and f_s (the usual suspects). From there you will be able to set the ind. ripple = 20mA and solve for your new L_1 value. After doing so, you can take a sip of your cool frosty Mountain Dew Code Red, you've earned it. And if you don't have a Dew, you might think about getting one.
well pooh. I think I almost got there, but mine came out in terms of V instead of Vg. When estimating the ripple for i_ci(t), we use the small ripple approximation to determine the slope of the ripple, correct? My I_L1 was in terms of D, V and R.
Yes since the small ripple approximation method results in a zero ripple current in the input inductor which is not accurate,I followed the method as described of section 2.5 of the textbook to find the exact ripple current.
4 comments:
That is what I got as well. It was Vg-Vc1 for all time.
L. Simpson
2.9 d): The use of small-ripple approximation creates the problem that you're seeing (I think).
In order to determine the peak inductor current ripple, you will need to find the ripple without SRA method. See lecture 4 slides (annotated version), slides 14-18 for help with this. There is an example for cap ripple, but as the slides mention, a similar process can be used for inductor ripple as well.
If everything goes smoothly, you should end up with a relationship between peak inductor ripple and Vg, D, R, L_1, C_1, and f_s (the usual suspects). From there you will be able to set the ind. ripple = 20mA and solve for your new L_1 value. After doing so, you can take a sip of your cool frosty Mountain Dew Code Red, you've earned it. And if you don't have a Dew, you might think about getting one.
- Keith
well pooh. I think I almost got there, but mine came out in terms of V instead of Vg.
When estimating the ripple for i_ci(t), we use the small ripple approximation to determine the slope of the ripple, correct? My I_L1 was in terms of D, V and R.
Yes since the small ripple approximation method results in a zero ripple current in the input inductor which is not accurate,I followed the method as described of section 2.5 of the textbook to find the exact ripple current.
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