what is the difference between PWM and simple comparator based regulator ?

[Sahil_khan]

Dear Guys

I am working on the design of a buck converter. Using the classical approach of PWM for gating the Mosfet. I have also implemented a PI controller.

I came to know another approach of simply comparing the output voltage of my buck converter with a Vref and the feeding them to a comparator, hence the comparator will On and Off depending on the value of Vout-Vref. Using this technique I would have actually a variable frequency operation depending on the load.

This approach seems to be quite simple and more stable and much more fast. Now my question is, if this is so simple approach then why we always use PWM technique instead?

Thank you all.

 

[BALKRISHNA TULSYAN]

Using PWM method you can design fixed frequency regulator while second method is used when variable frequency regulator is designed. Basic point is that when load current is small then power efficiency of PWM regulator is low. So for low load current u choose second method of designing. Where as for high load current u choose PWM method.

 

[energeio]

I just read the post. Could you please explain more in detail this statement ."Basic point is that when load current is small then power efficiency of PWM regulator is low". Thank you