how to get high duty ratio???

[biswaIITH]

i am using SG3525 PWM ic for voltage control in a dc-dc converter..i read in internet that the maximum duty we can get from both outputs is 50%...is there any way of getting more than 50% duty ratio in a closed loop feedback control using SG3525

 

[FvM]

SG3525 is designed to drive push-pull converters and has no option to get 49 % duty cycle from a single output. You can connect an ORing circuit or use SG3524 with both open collector outputs parallel connected. Unfortunately it's not suited to drive MOSFETs without a buffer stage.

 

[biswaIITH]

i am designing a buck-boost converter integrated buck converter...could u plzz advise me any good voltage controller ic for closed loop feedback...

 

[schmitt trigger]

I hesitate to suggest a device, because 9 out of 10 times, the poster will come back with either "this is not available where I live" or "it is too expensive" or "I can't solder surface mount devices".

Rather, what I suggest is that you go to the Texas Instruments, OnSemi, Fairchild websites and based on your parameter criteria, choose a device that is both available and within your budget.
You can then come back here and say: "hey! I found these three devices, which one would you recommend?" and we would gladly help you out to narrow your decision.