• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 64 subscribers
  • Views 311 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM2577: LM2577 Snubber Circuit

John Scoles
Prodigy 40 points
Part Number: LM2577

Stuck on the LM2577 again

I have the design bread-boarded and sort of working for 12Vin and +-15 volts out  so that means I willl require the Snubber  circuit as well.

as the the  transformer is Lp=200 and the input voltage is 12 and the max I is 300ma

Now I am stuck on how  Ip(PK)  is derived?

Was using a  '1N4148'  in the circuit as the FRD  so far I have been just plugging in values

.33 uf  for C and 250 ohm for 'R'  seem to work but are these  even close?

I can't seem to figure this one out.

Cheers

John

  • +1
    TI__Mastermind 25550 points

    Hi John,

    Ip(PK) is defined in table 5, equation 19. It is derived from adding half the peak-peak inductor current to the average input current.

    In equation 19, it derives the input current from the average of the output current [Iout/(1-D)] and then reflecting that current to the input current by the transformers ratio. Afterwards, peak-peak inductor current is derived by the inductor voltage-current relationship, as shown in equation 18 in table 5. 

    Thanks,

    Richard

  • 0 in reply to Richard Fu22
    Prodigy 40 points

    ok thanks

    That helped me out. 

    I also made a  silly mistake not converting  'Lp=200uh'  into h when I was doing my calculations once I corrected that I was getting a better values in my calculations  now getting  C=0.02 uf and R = 2k5 which I think is a better set of values

    Cheers

    and thanks again.