hello, ı have a homework about converters whıch 40-75v variable input voltage / 12v/20a-5v/10a output dc dc converter design. There are lots of examples about buck and flyback converters at google but ıcant find a desing about variable input voltage between 40-75v. Can someone help me while do design?

 

Think about how you would create one for 40v input and one for 75V. Then how you might make one circuit work for all voltages in between. Also when you write voltages you should specify AC vs DC.
Since this is homework you should do some work and learn something. Don’t expect someone to do it for you.

 

Welcome to AAC!

Are you supposed to design the switching regulator using discrete components? Or are you supposed to learn how to use commercially available integrated circuits?

 

Think about how you would create one for 40v input and one for 75V. Then how you might make one circuit work for all voltages in between. Also when you write voltages you should specify AC vs DC.
Since this is homework you should do some work and learn something. Don’t expect someone to do it for you.

I dont expect someone to do it for me also ı already specify AC or DC.I can understand your concern. I've been searching for days but couldn't find a way out so I asked for help.

 

Welcome to AAC!

Are you supposed to design the switching regulator using discrete components? Or are you supposed to learn how to use commercially available integrated circuits?

this homework for learn how to use commercially available integrated circuits.

 

this homework for learn how to use commercially available integrated circuits.

That's not much of a challenge. All datasheets will have example circuits. The only challenge will be increasing the output to 20A.

 

The first part of the design problem is to determine the boundary conditions. If the problem was to design a converter with FIXED input an output voltages then you would presumably know how to proceed. Question: "What is the nominal duty cycle for an unregulated output given the following conditions:

1. 40 V Input and 12V Output
2. 75 V Input and 12V Output
3. 40 V Input and 5 V Output
4. 75V Input and 5 V Output

This gives you a range of duty cycles for the unregulated output. Once you have that capability you can add the output monitoing, compensation and duty cycle adjustment to achieve your regulation goals. The good news is that all of the duty cycles you will encounter in this project are less than 0.5, so things like sub-harmonic oscillation will not be a problem.