Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript, as an article, focused on the comparative analysis of several step-down DC-DC converters especially synchronous versus asynchronous switched inductor converters. The first comment is the manuscript must be submitted and considered as a "Review" not an "Article because it mostly deals with comparision and evaluation of recent converters in the field, and there is not any significant contribution. 

Moreover, modern vehicles is claimed as an application for the analyzed wide input voltage range step-down converter, however, no results and discussions are in the manuscript to validate it. 

Furthermore, some recent works are listed in the Introdution section without any brief explanations. 

All in All, I suggest/recommend the paper must be updated with sufficient references and details and resubmitted as an Review. 

Author Response

Dear Reviewer,

Thank you for your time and thoughtful comments on the manuscript. We sincerely appreciate your feedback. Please find our detailed responses to each of your points below.

 

Comment 1: The first comment is the manuscript must be submitted and considered as a "Review" not an "Article because it mostly deals with comparision and evaluation of recent converters in the field, and there is not any significant contribution. 

Response 1: While the manuscript includes comparative analysis, it is respectfully submitted as a research article rather than a review. The study goes beyond summarizing existing work by presenting original experimental measurements of 14 commercially available wide-input DC-DC converters, all tested under standardized and repeatable conditions. It also applies a mathematical model to estimate power losses and efficiency, followed by a statistical analysis to quantify prediction accuracy. These steps provide new, application-specific insights into converter behavior under low-power automotive conditions. Unlike review articles that typically synthesize findings from existing literature, this work introduces original data and evaluation results that can serve as a practical reference for future integrated converter development. For these reasons, we believe the manuscript meets the requirements for an original research article.

 

Comment 2: Moreover, modern vehicles is claimed as an application for the analyzed wide input voltage range step-down converter, however, no results and discussions are in the manuscript to validate it. 

Response 2: This comment has been addressed by revising and restructuring the relevant section of the Introduction. Specifically, the paragraph beginning at line 32 was updated to better justify the automotive relevance of the evaluated converters. The text now clarifies that the target application involves powering low-power vehicular systems such as GNSS modules and communication modems, which operate from a regulated 4 V output across a wide input voltage range. Additionally, references [4], [5], and [6] were replaced with more relevant and up-to-date sources to support the discussion on typical battery voltages in modern and emerging vehicle platforms.

 

Comment 3: Furthermore, some recent works are listed in the Introdution section without any brief explanations. 

Response 3: As noted in the previous response, the references in the Introduction were reviewed and updated to ensure they are directly relevant and informative. Each reference now provides clearer context regarding the intended application, typical specifications of the analyzed converters, and relevant use cases. To improve the structure and clarity of the manuscript, the Introduction was also reorganized and partially merged with the previously separate Section 2. This change allows for a more coherent presentation of background information and scope without expanding into a full review of converter topologies, which is outside the intended focus of the article.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear colleagues, Your work is of potential interest. I must confess that the idea of evaluating commercial devices doesn’t sound very scientific, but rather more from the engineering or educational point of view. Still, the study is interesting for the educational and academic field. I will provide some comments which may help you improve it.

 

In the scientific literature, it is common to read that one drawback in DC-DC converter is revealed when the voltage gain is too high or too low, which requires a duty cycle close to one or zero. And that there is a maximum gain of five for efficiently boosting voltage with a non-isolated DC-DC converter (or one over five for bucking); as a reference, you can see this book: Lenk Ron. Practical Design of Power Supplies. USA: IEEE-Press, Wiley-Interscience Publishers; 2005. (Chapter 2 “Practical Selection of Topology”, page 18). It is possible that the technology is better now, and those limits are not updated. Can you comment on something related to that in the introduction?

 

Section 2 is maybe to short and then confusing for some readers. Table 1 includes a summary of information, but please include the topology (schematic) of each of those converters to have a better idea of what you are comparing. Please also define what you understand for a switched inductor converter; it seems you mean the traditional buck converter; why do you call it that if we all call it buck converter? I am not saying something is wrong; just saying that if there is a specification that I am not grasping, maybe other readers would get confused, too. Then please provide some examples of non-switched inductor converters. Please also explain why Table 1 seems to include very different topologies, which usually may have different applications, and that is the application you are using for comparison (what is the input voltage, output voltage, power, and application). Another option is just eliminating that section and explaining that you are comparing commercial buck converters for some particular application (and explaining it).

 

The explanation you provide with Fig. 1 is ok, but it is well known and also well explained in vendors literature like Texas instruments. They still sell all the options for different applications. IT would be better if you could provide the information (or at least some comments and discussion) they don´t explain, like approximated cost, PCB space, and volume weight of the entire solution with the different options.

 

It would be better if you could add a table with the specifications of the evaluated converters and also an explanation of how you choose them. In the experimental evaluation, it is mentioned that temperature was measured using a thermal camera. Please include (if possible) the accuracy of the camera.

Author Response

Dear Reviewer,

Thank you for your time and thoughtful comments on the manuscript. We sincerely appreciate your feedback. Please find our detailed responses to each of your points below.

 

Comment 1: In the scientific literature, it is common to read that one drawback in DC-DC converter is revealed when the voltage gain is too high or too low, which requires a duty cycle close to one or zero. And that there is a maximum gain of five for efficiently boosting voltage with a non-isolated DC-DC converter (or one over five for bucking); as a reference, you can see this book: Lenk Ron. Practical Design of Power Supplies. USA: IEEE-Press, Wiley-Interscience Publishers; 2005. (Chapter 2 “Practical Selection of Topology”, page 18). It is possible that the technology is better now, and those limits are not updated. Can you comment on something related to that in the introduction?

Response 1: 

Additional comments regarding low duty cycle challenges have been added to the introduction (paragraph starting at line 74). While it is true that extremely low duty cycles can be problematic, they are not necessarily critical in the context of this study. The mentioned reference focuses on power supplies up to 10 kW, where longer rise/fall times and higher switching losses make such rules of thumb more applicable. E.g. "Don’t plan on running duty cycles outside the limits of approximately 10% minimum or 80% maximum". In contrast, the converters analyzed in this study operate at much lower power levels (up to 8 W), allowing shorter transition times and low duty cycles.

This is supported by the data in Table 4. For example, a converter operating at 150 kHz with a 90 V input and 4 V output has a duty cycle of approximately 4.44%, resulting in an on-time of about 300 ns. Measured rise/fall times range from ~5 ns to 40 ns, depending on the converter. While such low duty cycles do increase switching losses, these were accounted for in the analysis and do not contradict theoretical knowledge.

 

Comment 2: Section 2 is maybe to short and then confusing for some readers. Table 1 includes a summary of information, but please include the topology (schematic) of each of those converters to have a better idea of what you are comparing. Please also define what you understand for a switched inductor converter; it seems you mean the traditional buck converter; why do you call it that if we all call it buck converter? I am not saying something is wrong; just saying that if there is a specification that I am not grasping, maybe other readers would get confused, too. Then please provide some examples of non-switched inductor converters. Please also explain why Table 1 seems to include very different topologies, which usually may have different applications, and that is the application you are using for comparison (what is the input voltage, output voltage, power, and application). Another option is just eliminating that section and explaining that you are comparing commercial buck converters for some particular application (and explaining it).

Response 2:

Thank you for the detailed feedback. The term "switched inductor" has been replaced with the more commonly used term "buck converter" to avoid confusion. While switched inductor topologies can refer more broadly to variations like tapped-inductor or coupled-inductor converters, the intent was to refer to the simple buck topology.

Table 1 was originally included to give an overview of various DC-DC converter types and to motivate the focus on buck converters. However, in response to this comment, the material from Section 2 has been consolidated into the Introduction. This helps clarify the scope of the study without expanding into an in-depth review of all topologies, which is outside the article's objective. The revised Introduction briefly introduces alternative topologies while clearly stating that the article focuses on commercial buck converters designed for low-power applications with wide input voltage ranges.

 

Comment 3: The explanation you provide with Fig. 1 is ok, but it is well known and also well explained in vendors literature like Texas instruments. They still sell all the options for different applications. IT would be better if you could provide the information (or at least some comments and discussion) they don´t explain, like approximated cost, PCB space, and volume weight of the entire solution with the different options.

Response 3: 

Figure 1 is included to improve accessibility for all readers and to ensure the article remains self-contained. While the concepts may be well known to experienced readers, we believe a brief explanation of converter control schemes adds clarity and helps support later sections of the paper. Additional discussion related to PCB area, IC packaging, and solution complexity are included into Section 2, which helps distinguish between controller-based and integrated solutions. These factors are important in evaluating suitability for compact automotive applications.

 

Comment 4: It would be better if you could add a table with the specifications of the evaluated converters and also an explanation of how you choose them. 

Response 4: Specifications of the evaluated converters are presented in Table 4, located in Section 6. Additional clarifying text has been added to both the Introduction and Section 6 to explain the selection criteria. The converters were chosen to represent a variety of commercially available solutions with different manufacturers, internal topologies, and control strategies, including both synchronous and asynchronous implementations.

 

Comment 5: In the experimental evaluation, it is mentioned that temperature was measured using a thermal camera. Please include (if possible) the accuracy of the camera.

Response 5: The accuracy of the thermal camera has been added to Section 8 (line 329). The camera used was the ShortCam Langchi LC-AD11, with a specified thermal accuracy of ±2%

Reviewer 3 Report

Comments and Suggestions for Authors

This paper gives the experimental and analytical look at 14 wide input voltage range step-down DC/DC converters for low-power applications. The strength of the work is in how broad and detailed the comparative analysis is rather than developing a new converter topology. The technical analysis and experimental work are strong but there are a few areas that can be explored or at least mentioned as the future of this work:

1- It’d be good to mention or discuss thermal management techniques like heat sinks, etc. after measuring PCB temperatures in the thermal analysis. 

2- the tests are all done under static load conditions, but automotive systems deal with dynamic loads. Can you discuss how these converters might handle that sort of stress ?

3- There’s no mention of fault tolerance or robustness.

4- a sensitivity analysis with respect to variations in things like gate charge or dead time could be very useful for the comparisons

5- the fonts used for the letters in figure 7 are too large

6- EMI testing and EMC strategies aren’t really covered. How these topologies can handle filtering? How about PCB layout for noise?

7- The mathematical expressions for RMSE and R² or an other metrics used in analysis should be presented

8- The units in the tables should be placed between parentheses for consistency and clarity. For example: "V_D (V)" instead of "V_D, V" in table 4 

Thanks.

Author Response

Dear Reviewer,

Thank you for your time and thoughtful comments on the manuscript. We sincerely appreciate your feedback. Please find our detailed responses to each of your points below.

 

Comment 1: It’d be good to mention or discuss thermal management techniques like heat sinks, etc. after measuring PCB temperatures in the thermal analysis. 

Response 1: A discussion of thermal management considerations has been added to the manuscript (beginning at line 496). It is noted that no dedicated thermal enhancement techniques—such as heat sinks, thermal vias, or additional copper planes—were used during the measurements, in order to ensure fair comparison between devices. The text now acknowledges that such methods can significantly improve thermal performance in practical applications but were intentionally excluded from this study to maintain uniform testing conditions across all converters.

 

Comment 2: the tests are all done under static load conditions, but automotive systems deal with dynamic loads. Can you discuss how these converters might handle that sort of stress ?

Response 2: A discussion addressing the limitations of static load testing and the relevance of dynamic loads in automotive applications has been added to the manuscript (starting at line 518). It is acknowledged that the scope of the study is limited to static load conditions. This approach was chosen to ensure standardized and repeatable testing across all converters, allowing for a fair comparison. While dynamic loads are important in real-world automotive systems - especially in communication and sensor subsystems - static load testing provides more universally applicable insights into efficiency and thermal behavior. The potential effects of dynamic load transients are noted as an important area for future investigation.

 

Comment 3: There’s no mention of fault tolerance or robustness.

Response 3: An additional paragraph has been included in the discussion section (beginning at line 537) explaining why fault tolerance and robustness were not evaluated in this study. While these aspects are important in practical applications, their assessment requires specific test scenarios outside nominal operating conditions—such as input surges, output short circuits, or thermal overstress—which were beyond the defined scope of this work. The focus of the article is on evaluating converter performance under typical conditions relevant to low-power automotive systems. Robustness is acknowledged as a system-level consideration that can often be enhanced through external protection circuitry.

 

Comment 4: a sensitivity analysis with respect to variations in things like gate charge or dead time could be very useful for the comparisons

Response 4: We appreciate this suggestion. However, parameters such as gate charge and internal dead time are not directly accessible or adjustable in commercial DC-DC converter ICs. As the study focuses on off-the-shelf components, it is not possible to vary these internal characteristics in a controlled or systematic way. Therefore, a sensitivity analysis of such parameters falls outside the scope of this work.

 

Comment 5: the fonts used for the letters in figure 7 are too large

Response 5: Figure 7 has been updated to use smaller and more appropriately scaled font sizes, in accordance with the comment.

 

Comment 6: EMI testing and EMC strategies aren’t really covered. How these topologies can handle filtering? How about PCB layout for noise?

Response 6: A paragraph discussing EMI and EMC considerations has been added to the discussion section (beginning at line 527). It is noted that these aspects were not evaluated in this study, as they are highly dependent on system-level implementation, including external filtering, shielding, and PCB layout practices. Since the focus of the article is on evaluating intrinsic converter performance under standardized electrical conditions, EMI/EMC testing was considered outside the scope of this work.

 

Comment 7: The mathematical expressions for RMSE and R² or an other metrics used in analysis should be presented

Response 7: Full mathematical expressions for RMSE, R², and other statistical metrics were not included in the manuscript to maintain conciseness, as these are well-established and commonly used in statistical analysis. However, references to standard sources explaining these metrics—[29], [30], and the newly added reference [31]—are provided for completeness.

 

Comment 8: The units in the tables should be placed between parentheses for consistency and clarity. For example: "V_D (V)" instead of "V_D, V" in table 4 

Response 8: All tables have been reviewed and updated for consistent unit formatting. Units are now presented in parentheses as suggested, for improved clarity and uniformity.

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Most of the comments are already addressed, however, the manuscript can be updated in case of the "title" and Introduction to better reflect the contribution of the paper. 

Author Response

Comments 1: Most of the comments are already addressed, however, the manuscript can be updated in case of the "title" and Introduction to better reflect the contribution of the paper. 

 

Response 1: 

Thank you for the suggestion. The title has been revised to better emphasize the nature of the work as an experimental review. The new title is:

“An Experimental Review of Step-Down Converter Topologies with Wide Input Voltage Range for Modern Vehicle Low-Power Systems.”

Additionally, the Introduction section (lines 75–95) and the paragraph in Conclusion section (starting at line 547) have been updated to place clearer emphasis on the article’s contribution as an experimental review, highlighting the systematic methodology and comparative evaluation of the 14 converters under study.

Reviewer 2 Report

Comments and Suggestions for Authors

My comments have been addressed. Thank you.

Author Response

Dear Reviewer,

Thank you for your time and for confirming that all comments have been addressed. We appreciate your valuable feedback throughout the review process.

Best regards,
Lukas Šalavėjus