I'm designing a current mode controlled buck converter IC which can work in either fixed frequency PWM in normal load, and pulse skipping mode in light load. I have a flag to indicate whether the load current is small enough to be a light low case or not by using a current controlled voltage source in series with the load to compare the load current with a reference threshold for light load current.
Now I'm thinking about how my controller can detect if the load is light enough because it is not possible to measure current directly from the load in an IC as in simulation. Is there a practical way to determine the load condition? Is comparing the compensator output to a threshold a good idea for a current mode control buck? In voltage mode, I think it is okay as this voltage also set the duty cycle directly through comparing with the PWM ramp comparator, but for a current mode, the duty cycle is indirectly controlled by this.
*Update: My converter is synchronous, and I used my zero crossing detector as a light load indicator as well. I counted if the zero crossing happens more than 4 continuous cycles then light load flag is triggered. For normal load detection to go back from light load mode to normal PWM, I compare the output voltage with a reference about 98% target output, so if light load mode cannot handle the load then the drop will trigger the comparator and the converter will jump back to PWM mode. I am not sure if this is the best scheme for toggling between modes, but for now it can do the job.