## 7 Conclusions  
In this review study, recent trends in DC-DC converter implementations for LEV charging were chronicled--ranging from on-board chargers to off-board chargers. From these trends, we have observed that on-board charging technology has reached a high level of maturity in recent years. Off-board chargers were also discussed in this work, as an alternative to on-board charging. Although off-board charging has not reached same the level of maturity as that of on-board, the technology is increasing in interest among researchers--so much so that their suitability for renewable energy integration is being heavily evaluated. Furthermore, the segregation of DC-DC converters into isolated and non-isolated topologies was also discussed. It was observed that while isolated converters can inherently support soft-switching and are beneficial from a safety point of view, they suffer from setbacks such as voltage spikes during switching and relatively high component count. In contrast, non-isolated converters are also an option for LEV charging due to their relatively simple and compact design, and they can be explored further. A gap that needs addressing is to arrive at a balance between circuit and control complexity, and converter performance parameters. Another gap in research that needs to be investigated is the unlocking of potential for vehicle to grid (V2G) capability.  
Additionally, this review discusses issues and some emerging techniques that can be used to augment LEV charging:  
* Wireless charging techniques, their optimization and safety aspects.
* Fast charging through high current DC-DC converters, and battery swapping.
* Integration of renewable energy sources such as solar PV into charging system, ensuing challenges and how to overcome them.
* Use of superior wide band-gap semiconductor switches for implementing LEV fast chargers, and barriers in their adoption.
* Advanced charging techniques such as reflex charging and constant temperature control.
* Compatibility of LEVs with standardized charging stations and battery swapping stations.
* Considerations with respect to electrical insulation requirements and necessity for insulation monitoring.  
**Author Contributions:** Conceptualization, M.F.A., S.R.S.R. and M.N.A.; Formal analysis, M.F.A., S.R.S.R. and N.A.R.; Funding acquisition, M.N.A. and E.A.B.; Methodology, M.F.A., S.R.S.R. and N.A.R.; Project administration, S.R.S.R., S.R.S.R. and E.A.B.; Supervision, S.R.S.R. and N.A.R.; Writing--original draft, M.F.A.; Writing--review and editing, M.F.A., S.R.S.R. and E.A.B. All authors have read and agreed to the published version of the manuscript.  
**Funding:** The work is supported by the Ministry of Higher Education Malaysia via Fundamental Research Grant Scheme (FRGS/1/2020/TK0/UM/02/41). The authors also thank the technical and financial assistance of UM Power Energy Dedicated Advanced Centre (UMPEDAC) and the Higher Institution Centre of Excellence (HICoE) Program Research Grant, UMPEDAC--2020 (MOHE HICOE--UMPEDAC), Ministry of Education Malaysia, IF006-2021, RU002-2021, University of Malaya.  
**Informed Consent Statement:** Not applicable.  
**Acknowledgments:** The authors thank the technical and financial assistance of UM Power Energy Dedicated Advanced Centre (UMPEDAC) and the Higher Institution Centre of Excellence (HICoE) Program Research Grant, UMPEDAC--2020 (MOHE HICOE--UMPEDAC), Ministry of Education Malaysia, IF006-2021, RU002-2021, University of Malaya.  
**Conflicts of Interest:** The authors declare no conflict of interest.