I have designed BUCK regulator using PWM topology and now want to add PFM also for compensating the low load operation.Tell me some idea how should I start and how I can reduce the circuit used alone for PFM.
your response is greatly appreciated.

rds
varun

This is a step-down converter which is also called as the Buck Converter. In order to regulate the output he needs a PWM. PWM(Pulse Width Modulation) is used in order to regulate the output of the buck when targetted to deliver high current loads. For PFM he needs a similar control loop to vary the frequency. Here you needs to compare the output of the buck with a reference voltage through a low offset comparator and a digital PWM to regulate the loop.

I can send the link to a Ph.D thesis where it is explained. Please be aware that PFM is totally a recent development and people are exploring ways to use it in Low Voltage applications for low load currents. There bv we don't need to burn currents with PWM techniques for low load currents.

http://www-power.eecs.berkeley.edu/publications/thesis_documents/jinwen_thesis.pdf

Hope this helps you..