Valley Current Mode and Slope Compensation

Thread Starter

BitsNBytes

Joined Mar 22, 2021
12
Hello,
I am curious to know if anyone has seen resources discussing slope compensation when valley current mode is implemented. All of the literature I have found thus far only discuss slope compensation for peak current mode.
 

Papabravo

Joined Feb 24, 2006
17,551
Well in the normal Current Mode Control you have two functions to do each switching cycle: SET the flip-flop that turns the switch on and CLEAR the flip-flop that turns the switch off. The SET function is normally controlled by a fixed frequency clock so that whatever else happens the switch is ALWAYS turned ON, once per cycle. The CLEAR happens when the instantaneous current reaches the value of the slope compensation signal.

Your proposal, which I have not previously seen described is to interchange the order of operations and have the CLEAR signal, which turns the switch off be driven by the clock, while a rising slope compensation signal is used to detect the valley in the load current and turn the flip-flop back on. I don't see any apriori reason why you could not do that, but does it have any particular advantage over the traditional method? In particular will it also prevent sub-harmonic oscillation?

You could implement this on a simulator to experiment with the concept.
 

Thread Starter

BitsNBytes

Joined Mar 22, 2021
12
If by "traditional method" you mean peak current mode, then I would say it comes down to choosing which method one requires based on the advantages and disadvantages of peak, valley, or average current mode control.

I finally found a paper that does review valley current mode among others:
"Understanding and Applying Current Mode Control Theory by Robert Sheehan: SNVA555 on TI's website.
 

Papabravo

Joined Feb 24, 2006
17,551
If by "traditional method" you mean peak current mode, then I would say it comes down to choosing which method one requires based on the advantages and disadvantages of peak, valley, or average current mode control.

I finally found a paper that does review valley current mode among others:
"Understanding and Applying Current Mode Control Theory by Robert Sheehan: SNVA555 on TI's website.
What is the executive summary on the subject of advantages and disadvantages?
 
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