Steady-State Analysis of Asymmetrical Pulse-Width-Modulated Series Resonant Converter for Light Load Condition
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe paper shows impressive analytical derivations of many variables for the circuit, but finally comes to a point where only a numerical approach appears to be feasible. This raises the question whether the method is of practical significance: one could also set up a (numerical) simulation model and use it to tune the operation to the desired performance.
The approach to use the Laplace transform for analysis of the SRC circuit is not new and actually regularly taught in a MSc course in my institute since 2012 at least. The authors could profit from studying more recent works on SRC's, almost all of the references are from before 2000 - significant work was done after that, and should be studied and cited.
State-plane analysis is mentioned but discarded in the paper: I advise the authors to look at it again as it might lead to more insight in the circuit operation than just meticulously doing the algebra.
A few comments on the content (using the numbering on the right-hand side of the manuscript):
27-29: It is unclear from the statement why the DC blocking would make the converter particularly suitable for high power - this needs more explanation.
43: SPA is not limited to symmetrical waveforms.
48: grammar needs adjustment
67++ several assumptions are missing and need to be mentioned:
- The transformer is assumed ideal
- The supply and load voltages are assumed constant during the resonant cycle
- The voltage commutation is ignored in the analysis
139+ (Fig 3): resonances can be expected in the final part of the cycle (similar as in a flyback converter). This needs to be addressed, in particular as it may have impact on EMI and switching losses
232+ (Fig 8):
- Spikes can be observed on Vin - this needs explanation
- Vin and Vout are not constant during the resonant cycle which undermines the basis of the analysis
- Vout shows steps synchronous to the switching of Vin. This needs explanation.
234+ (Fig 9):
- resonances are clearly visible in the real circuit. See comment for line 139.
General: A more thorough description of the experimental setup is needed. Topology, part values, type of transistors and passives.....
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Reviewer 2 Report
Comments and Suggestions for Authors1) In abstract section, please try to avoid using acronyms. Also, it is reasonable to add more specific information regarding numerical data from simulation and experimental validation to extend the abstract a bit and make it more informative for a reader.
2) In the introduction section add more up to date references and highlight advantages of SRC (e.g. compare SRC with a couple of other topologies). At the end of the section it is necessary to add a short paper structure explanation.
3) In Fig. 1 (a) it is not quite clear why it is mentioned Vo/nt? Do you mean that the output voltage equals Vo = Vout (voltage on a primary winding) / nt?
4) If possible improve quality of Figure 8, 9 to avoid pixelation.
5) Conclusion part is too short, please improve it by adding more obtained results.
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Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors have presented Steady State Analysis of Asymmetrical Pulse-Width-Modulated Series Resonant Converter for Light Load Condition, The comments are;
1. The authors need to add how this proposed work compares to similar analytical work already presented in literature and how this analysis show important dynamic properties of the overall system.
2. The overall analytical expression must be used in simulation along with the full switched model of the converter in order to understand how closely the analyses and the real system match in performance.
3. Important case studies showing various corner scenario can be added both in the full switching model as well as the proposed model to understand the performance spectra achieved by the proposed work.
4. The presented experimental result should be modified and explained about why the waveforms are distorted as well as add some dynamic performance results to better understand the effectiveness of the proposed approach.
Comments on the Quality of English LanguageIt can be improved for better flow of information to the readers.
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Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe work in v2 has been improved significantly, but more is needed in my opinion:
Lines 37-38: This statement needs one or more references.
Line 43: in the time domain
Lines 45+: The part "... but becomes highly complex for converters with more than two state variables." is not relevant here, as you have only 2 SVs. You need better motivation to reject SPA for this circuit.
Lines 56,57: Also this statement needs (a) reference(s)
Lines 65: "...to the variable duty...."
Line 163: "and 3" --> "the waveforms in Figure 3"
Figures 6 and 7: the dotted lines connecting the squares should be removed as in my perception they do not correspond to a calculation result.
Figure 8: The explanation of the spikes due to reverse conduction of the GaN switches is ok now, I can only advise to tune the dead time better.
But: my previous comment "Vout shows steps synchronous to the switching of Vin. This needs explanation." is not properly addressed yet. The cause for the steps (as for example at the point where Vin goes down close to t=8 us in fig 8a) can probably be attributed to the presence of some leakage inductance in the transformer. Measuring Vout at the secondary side will then lead to waveforms which correspond much better to the circuit model as shown in fig. 1b.
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Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors have successfully answered all the queries raised by the reviewer in the previous version and have modified the manuscript accordingly. No further changes needed.
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Round 3
Reviewer 1 Report
Comments and Suggestions for AuthorsNice improvements, only two issues left:
Line 162: "Figures 1(b)" --> "Figure 1(b)"
Figures 8/9: The signals make much more sense now. I am not happy with the use of a composed variable "Vout/nt", as shown in the graphs and in the text several times. I would prefer to add an extra voltage indication such as "Vsec" at the secondary side of the transformer in figure 1(a) and use that name everywhere instead of "Vout/nt". You could add a remark about the non-ideality of the real transformer to explain this choice of measurement point.
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