Description

AN4339

14/27

DocID025039 Rev 1

Poles and zero from error amplifier transfer function are:

Equation 27

Transfer function of feedback loop is:

Equation 28

Where CTRmin = 0.5 - minimum current transfer ratio of optocoupler in feedback loop.

Poles and zero of above transfer function are:

Equation 29

cross over frequency is 13 Hz and desired phase margin is 40°.

fz1

1

2

 C12 R16







----------------------------------------------

=

fp1

1

2

 C12

R15 R16

+









---------------------------------------------------------------------

=

Hs



1

R27

----------- R18 R24



R18 R24

+

-----------------------------



1

s

1

---

C19

R28 R26

+





---------------------------------------------------

+

s

1

---

R26 C19



----------------------------









------------------------------------------------------------------



=

fp2

1

2

 R26 C19







----------------------------------------------

=

fz2

1

2

 C19

R28 R26

+









---------------------------------------------------------------------

=