Feedback - tl431 - flyback

Discussion in 'General Electronics Chat' started by Mirasoul, May 9, 2010.

  1. Mirasoul

    Thread Starter New Member

    Dec 7, 2009
    5
    0
    Hiho all. Ive got a problem with stability of closed loop feedback. I found Basso`s book and I did step by step as there is. Does anyone can tell what`s wrong(I mean why ive got RHP)? As you can see D=45%, so i work in DCM.

    Effect:
    Poles: 1.0e+005 *

    -8.9392
    2.0157
    -0.3453
    -0.0073
    Code ( (Unknown Language)):
    1.  
    2. clear;
    3. Uinmin=8;
    4. Uinmax=16;
    5. Uo=15;
    6. f=100000;
    7. Dmax=0.45;%max duty cycle
    8. Cooutput=110e-6; %filter
    9. Resr=25e-3  %filter
    10. Robc=25;     %Load
    11. s=tf('s');
    12.  
    13. %Filtr + Modulator
    14. fz=1/(2*pi*Resr*Co); %zero
    15. fp=1/(2*pi*Co*Robc); %pole
    16. Umodulator=0.33; %modulator ripple
    17. DCgainHigh=(Uinmax-Uo)^2*Ns/(Uinmax*Umodulator*Np);
    18. DCgainLow=(Uinmin-Uo)^2*Ns/(Uinmin*Umodulator*Np);
    19.  
    20. Wp=2/(Robc*Co);
    21. Wz=1/(Resr*Co);
    22. D1=DCgainHigh*((1+s/Wz)/(1+s/Wp));
    23. D2=DCgainLow*((1+s/Wz)/(1+s/Wp));
    24.  
    25. %Max crossover frequency
    26. fcross=f/(2*pi*Dmax);
    27.  
    28. %MOC %Optocoupler
    29. UfMoc=1.4;
    30. CMoc=18e-12;
    31. CTRmin=0.5;
    32. CTR=0.6
    33. CTRmax=0.8;
    34. UceMocSat=0.4;
    35. IfLed=60e-3;
    36.  
    37. %Tl431 %shunt regulator
    38. UrefTL431=2.5;
    39. IrefTL431=5e-3;
    40. Ukat=2.5;
    41.  
    42.  
    43. %NCP1216 - pwm controller
    44. Ifb=2e-3;
    45. Rpullup=20e3;
    46.  
    47. %Compensator
    48. RLedMax=(Uo-Ukat-UfMoc)/Ifb
    49. RbiasMax=UfMoc/1e-3
    50. Rbias=1e3;
    51. RLed=3e3;
    52.  
    53. k=5;
    54. fzKompensator=fcross/k
    55. fpKompensator=fcross*k
    56.  
    57. Rupper=50e3
    58. Cb=1/(2*pi*fpKompensator*Rpullup)
    59. Cz=1/(2*pi*fzKompensator*Rupper)
    60.  
    61. Gfb_out = -((s*Rupper*Cz+1)/(s*Rupper*Cz))*(1/(1+s*Rpullup*Cb))*Rpullup*CTR/RLed
    62.  
    63. bode(Gfb_out,'b',D2,'g',(D2/(1+Gfb_out*D2)),'r')
    64. figure(2),bode(Gfb_out,'b',D1,'g',(D1/(1+Gfb_out*D1)),'r')
    65.  
     
    Last edited: May 9, 2010
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    Friend, why not do us a favor and edit your post and put code tags around the code.

    It makes it much easier to read, and to cut and paste.

    type [ code] before the code and [ /code] after the code.
    remove the spaces is the tags above. the space after the [ in both tags.

    If you press the 'Go Advanced' button on the editor, next to the 'Post Quick Reply' button,
    you will be transfered to a more full featured editor.

    Highlight your code and click the '#' button located in the top of the editing box. This will automatically insert the code in the code tags.

    when you view the post after that, it will be laid out in a code box, much easer to read and more pleasant to work with.
     
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