# PFC Single-Phase AC/DC Boost Converters: Bridge, Semi-Bridgeless, and Bridgeless Topologies
## 2 Categorization of Bridge Boost Converter Topologies
### BBC Topologies  
Figure 1 shows the conventional BBC topology where (\(v_{ac}\)) is the electrical grid or feeding source. The rectification is performed by means of the diode bridge (\(D_{1}\), \(D_{2}\), \(D_{3}\) and \(D_{4}\)) [16; 30; 32; 33; 45]. Inductor (\(L\)) and capacitor (\(C\)) interchange energy while diode (\(D\)) prevents reverse currents. Resistor (\(R\)) is the load that is feeding through a regulated voltage from the DC bus. Control structure is usually implemented by using a cascade PI structure for regulating the DC bus and also performing PFC. The conventional BBC is the most common topology used in low voltage and power applications due to its reduced number of components. However, when medium and high voltage converters are required, power losses must be taken into account in the design process for obtaining a more accurate estimation of efficiency and gains of the system [28; 46]. In [16; 47], the authors showed the importance of soft switching for medium and high voltage and power applications of BBC. In [16], a review concerning soft switching techniques with snubber circuits to reduce power switching losses in BBCs was presented. This work analyzes four main aspects: (1) application for low voltage; (2) behavior in Discontinuous Conduction Mode (DCM) and Continuous Conduction Mode (CCM); (3) contrast between Zero Voltage Switching (ZVS), Zero Voltage Transition (ZVT), and Zero Current Switching (ZCS) techniques; and (4) comparison between MOSFET and IGBT switching technologies. It should be noted that there are switch technologies with better performance than conventional IGBTs and MOSFETs. These technologies include Gallium Nitride (GaN) switches and Silicon Carbide (SiC) MOSFET switches. GaN and SiC technologies can be used (recommended) in frequencies between 100 KHz and 200 KHz, so that GaN and SiC switches present better efficiency (lower losses) than conventional IGBTs and MOSFETs. More information concerning these switch technologies is available in [48; 49; 50]). In general terms, switching with ZVS or ZCS increases the switch useful life. Resonant BBC topology that operates with ZVS or ZCS can be implemented by adding an LC circuit to BBC conventional topology. Further details can be consulted in [51; 52; 53; 54; 55; 56; 57; 58; 59; 60; 61; 62; 63]. The aforementioned resonant LC circuit requires an additional switch (a second one) to introduce an inductor to the converter circuit for providing an additional path with zero impedance where the current and voltage do not strongly change their values. The BBC converter is directly connected to the AC supply, so its diodes and power switches inject harmonics and produce noise; then, an EMI filter is required. The authors in [26] present a design of an EMI filter for a medium power BBC, where results show a reduction of the Common Mode (CM) and Differential Mode (DM) noise when high switching frequency is needed. The EMI filter with classical linear PID control can reduce \(THD_{i}\) to normative ranges; nevertheless, limitations of PID control (slow and tuning around of an operation point) can reduce its efficiency, increasing \(THD_{i}\) and causing poor dynamic performance when the converter operates out of its design range [64]; this can be solved with nonlinear controllers or PID hybrid control techniques [3; 22; 24; 29; 30; 45; 65; 66; 67; 68]. For example, a modulation technique for the BBC that can operate in DCM or CCM, exhibiting a high \(PF\) and low \(THD_{i}\) over a wide range of input voltage and load is presented in [3; 69]. The conventional BBC topology can be modified as it was proposed in [70]. Figure 2 shows the BBC with pseudo-continuous conduction mode where diode \(D_{5}\) and switch \(Q_{1}\) were added in parallel with \(L\). This modification increases dynamic behavior in transients and reduces stress in \(L\) by current circulation.