Buck Converter Clarification

[electronicsLearner77]

I found the following formula for the buck converter, for example if the requirement is
Input voltage is 24V and the output voltage is 12V, using the standard buck circuit the duty cycle is calculated as D = output voltage / input voltage = 12/24 = 50% duty cycle. But i need to design a circuit where the input voltage range is 24-100V (2 to 10 Amps) and the output voltage is 12V (20 amps). In this case how do i calculate the duty cycle? Please advise.

 

[ramussons]

The duty cycle is calculated not by the voltages alone, but by Power IN to Power OUT.
That means an infinite set of values for various Input Voltage vs Output Power.
That is why you have a Feedback system for Pulse Width.

 

[crutschow]

As ramussons noted, you need a feedback loop.
You can't just calculate the duty-cycles and use that, since that doesn't include all the variables in a real circuit (circuit resistance, non-linear magnetics, etc.).
The duty-cycle will be close to the theoretical values you calculated, but will vary slightly depending upon the value of those variables.

 

[bertus]

Hello,

Have a look at the following page and the attached PDF.
https://www.richtek.com/Design Support/Technical Document/AN041?sc_lang=en

Bertus