# PFC Single-Phase AC/DC Boost Converters: Bridge, Semi-Bridgeless, and Bridgeless Topologies
## 6 Conclusions  
In this paper, a review and categorization regarding BBC, SBBC and BLBC topologies for PFC based on boost converter was presented; the basic operation, advantages, and disadvantages of these topologies were analyzed, including criteria for categorization which allows for unifying the technical language that is used in these types of devices. All consulted topologies need an input EMI filter and may reach high power factor (complying with IEEE Std. 519 and IEC/EN 61000-3-2) when PID controls are used; however, to reach high standards of power quality, the use of nonlinear control techniques is recommended. Basically, challenges are focused on improving energy quality concerning electromagnetic compatibility. An adequate PI tuning that includes any optimization technique can reduce the filter size; nevertheless, it could present a slow response in the face of disturbances or load changes in comparison with nonlinear control techniques. In general terms, nonlinear control can significantly reduce the filter size improving the converter behavior.  
BBC is widely used in low voltage applications due to its simplicity (low components and control requirements). Nevertheless, in medium voltage and power, a robust EMI filter is required, increasing power losses, implementation cost, and control requirements. BBC topologies based on bidirectional switches are not recommended due to the fact that other topologies can carry out the same function with better electromagnetic compatibility performance and less demanding requirements not only in control but also in implementation. In conclusion, BBC topologies present an appropriate dynamic performance for low voltage and power applications. As regards medium voltage applications, the use of interleaved BBC is recommended; nevertheless, it must be considered that its rectifier bridge may produce higher EMI.  
In general, topologies based on the symmetric distribution of components (SBBC) have better behavior than other topologies (BBC and BLBC) regarding efficiency and EMI when similar control strategies are implemented. In some topologies (as the clamped one), the same control signal can be used to operate all converter switches. SBBC topologies are symmetric with respect to the ground and several paths for current circulation. This reduces thermal stress in their components such as inductors and power switches. In addition, SBBC topologies can easily comply with IEEE Std. 519 and IEC/EN 61000-3-2 when PID controlsare implemented while using less robust filters than BBC topologies. For these reasons, SBBC topologies are recommended for low voltage and medium power applications.  
Conceptualization, J.R.O.-C., G.E.M.-R., N.M.-G. and S.D.S.-[PERSON]; Funding acquisition, [PERSON] and [PERSON]; Investigation, [PERSON]-C., [PERSON] and [PERSON]; Project administration, [PERSON] and [PERSON]-L.; Resources, [PERSON]-C., [PERSON]-R., [PERSON] and [PERSON]-L.; Supervision, [PERSON]-[PERSON] and [PERSON]-L.; Writing--original draft, [PERSON]-C. and [PERSON]-R. Writing--review and editing, [PERSON], [PERSON] and [PERSON]Z. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Colombia Scientific Program within the framework of the so-called Ecosistema Cientifico (Contract No. FP44842- 218-2018).  
Not applicable.  
The authors thank Corporacion Universitaria Minuto de Dios--UNIMINUTO for the support received in this research. The authors also acknowledge the support of the Colombia Scientific Program within the framework of the call Ecosistema Cientifico (Contract No. FP44842-218-2018).  
The authors declare no conflicts of interest.