How to Find Crossover Frequency?

[sjabbari]

Hi to all

I try to see bode and phase plot of flyback converter in DCM mode on MATHCAD 15

After write equations i can see all result is ok.

My problem is, i don't know how can i understand crossover frequency on 0db? I don't know which equation i can use to give this frequency?

[RichardJ · Accepted solution]

Make AR a function of omega, and then solve for omega when AR=0.

Note that Mathcad has sqrt(-1) built in. You get it by typing 1i or 1j.

[sjabbari]

Thanks a lot Mr. Jackson

For last question:

I don't understand this line

w:=1000    given      AR(w)=0  w0=FIND(w)  w0=3509

1. Why do you use w:=1000 ?

2. Can you explain about Given ? I search about "Given" on help of MATHCAD but unfortunately i don't find any description of this!!!

3. Why evaluate sign "=" of AR(w)=0 bolder than other one?

4. Why in w0 before of zero (0) using "Decimal Point" sign?

Excuse me for my question, because i am newbie in MATHCAD

Your Sincerely

Saeid Jabbari

[RichardJ]

1. It's a guess value

2. Look up solve blocks in the help

3. It's a boolean equals, not a numeric assignment operator.

4. It's just part of the variable name. Look up literal subscripts.