Comments on Duty cycle of buck-boost converter
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Duty cycle of buck-boost converter
+5
−1
I have the following problem: -
Using Wikipedia I find that during CCM we have the relation: -
$$\frac{V_{out}}{V_{in}} = -\frac{D}{1-D} $$Solving for $D$ and inserting values gives me
$$D=\frac{20\text{V}}{20\text{V}-24\text{V}} = -5 $$But this doesn't seem to make sense. First of all, the duty cycle is negative... Second the duty cycle is more than 100%!
Why do I get this erroneous result?
EDIT
Turns out I used the wrong formula. Using the formulas given by my instructor for the course: -
yields $d=0.454545 $
Post
+4
−0
If you're referring to this Wikipedia page then the topology has a negative output. In that case, the problem as you have it stated in the OP, is misleading: it should be Vo=-20. With that, extracting D will give:
$$D=\dfrac{V_{out}}{V_{out}-V_{in}}=\dfrac{-20}{-20-24}=0.4545$$
Sure enough, a quick check shows the confirmation:
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