Yes. In DCM, there is no RHPZ.(1) can I say RHPZ only exists in CCM, but not DCM?
When operating in CCM, the RHPZ always exists, no matter what sort of modulation scheme you use. I have also seen others report that constant off/on time control mitigates the RHPZ, but it's simply not true. The RHPZ is built into the boost circuit itself. The controller can add poles/zeros onto the overall transfer function, but it can't remove existing ones (can't cancel a RHPZ since a RHPP is unstable).(2) does RHPZ also exist when we have variable frequency mode control? For example, contant off time control has been used in Boost and buck-boost. There is a similar question asked in this forum but no conclusive answer was posted there.
Show your work. The concept of poles/zeros existing above the switching frequency makes no sense (in the context of state space averaging). It's like trying to describe the frequency response of a digital filter outside its nyquist bandwidth.RHPZ exists in both boost- and buck-boost-derived CCM and DCM converters. The power-stage inductance determines the frewuency at which it exists. In DCM, it exists at a very high frequency beyond our highest frequency of interest such that it's effect doesn't affect our feedback loop. This is because of the low-value inductance used in the power stage. In CCM, because the inductance is heavy, it shows up at a frequency lower than our switching frequency and actually dwells within the vicinity of our desired crossover frequency.
The CMC loop itself has no RHPZ, since the CMC loop governs the inductor current, not the output current/voltage. But if we look at the response of the output, the RHPZ pops up, regardless of whether a CMC loop is used.However a current mode control loop implemented on a boost doesn't have an RHP zero I believe.
Assuming you mean the bandwidth of the voltage loop is lower than the RHPZ. That's typically the only way to deal with it.And if that's wrapped by a voltage loop with a lower bandwidth the remaining impact of the RHP zero should be almost nothing.
How do you mean show your work? I'm not the OP....
Show your work. The concept of poles/zeros existing above the switching frequency makes no sense (in the context of state space averaging). It's like trying to describe the frequency response of a digital filter outside its nyquist bandwidth.
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Actually frhpz is higher for converters with higher values of Rload.looking at those equations, they only come into play when Rload is very large...
This statement is with the consideration of closing the loop. I'm considering the inherence of the RHPZ in the power stage.but really right hand plane zero comes into play only when CCM entered into
I do not understand what you mean here but you don't increase this D. This D is already the maximum value for the converter.Common sense reinforces this, under fully DCM, over one complete cycle the o/p power goes up for an increase in D, under CCM over one complete cycle o/p power does not go up for an increase in D...
Respectfully - I cannot agree with you.
hi - just read it - you refer to equ 18 & 19 in that paper - the so called RHP zero is in fact formed from the output load and the ESR & ESL in the output cap AND the boost choke - it is barely a zero - it merely flattens out the gain response as you now have an inductive divider at high frequencies.
This statement again is considering a closed-loop converter not the power stage alone as it should.There is no RHPZero in the sense that increasing on time in DCM gives a delayed response - it doesn't - as somewhat hazily pointed out in the preceding text
I do not want to comment on this. But I haven't seen it anywhere on this paper.although the writer does conflate DCM and CCM operation at times ...
Hi,
For Q1:
RHPZ exists in both boost- and buck-boost-derived CCM and DCM converters. The power-stage inductance determines the frewuency at which it exists. In DCM, it exists at a very high frequency beyond our highest frequency of interest such that it's effect doesn't affect our feedback loop. This is because of the low-value inductance used in the power stage. In CCM, because the inductance is heavy, it shows up at a frequency lower than our switching frequency and actually dwells within the vicinity of our desired crossover frequency.
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But no - not in DCM, in DCM when the D is increased a little the total power to the load goes up in that cycle, because time where the current would otherwise be zero - is now active time - therefore no RHP zero, inside that same cycle the peak input current is bigger and the total current to the load ( & o/p cap) is also bigger - you are confusing with CCM ...
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