Bridgeless High Power Factor Buck-Converter Operating In Discontinuous Capacitor Voltage Mode

High power factor AC-DC rectifiers have gained a lot of attention due to demanding international regulations. The international harmonics’ standards, i.e. IEC 61000-3-2 and EN 61000-3-2 require low harmonic content of the main line current, or in other words, high power factor. Also, new market initiatives such as the 80 PLUS initiative, require high efficiency of the power supply. These standards specify the AC line current harmonics’ limits depending on load and application. In this research, a new converter, with high power factor and high efficiency, operating in discontinuous capacitor voltage mode (DCVM) – is investigated targeting personal computers (PC) and server applications. To the best of our knowledge, this is the first publish bridgeless topology operating in DCVM. To ensure high efficiency, the bridgeless rectifier topology is modified by eliminating two diodes and replacing them with two unidirectional switches. On the other hand, the DCVM has the advantages of no need for high frequency input filter, soft turn-off switching, low switch current stress and high efficiency at low loads. A comparison between full bridge DCVM buck power factor correction (PFC) converter and the proposed topology is presented. The present topology found to have higher efficiency than that of the full bridge DCVM buck PFC converter, and less THD. Hence, the power factor has been significantly improved. The comparison is summarized and tabulated in chapter five Design procedure, simulation and measurements are in chapter five. Simulation results are presented to demonstrate the topology’s performance. Orcad PSpice software has been used to simulate the proposed topology. Measurements are presented to verify the theoretical analysis and the simulation findings. The harmonics at the input current are also compared with the IEC 61000-3-2 harmonic standard values. A step by step design procedure for the converter has been developed at any operating point over universal line input voltage (90-265Vrms). Small signal analysis and bode plots for the proposed topology were developed for the line-to-output and control-to-output transfer functions

Power quality improvements of arc welding power supplies by modified bridgeless SEPIC PFC converter

This paper proposes an efficient bridgeless power factor corrected (PFC) modified single ended primary inductor converter (SEPIC) for arc welding power supplies (AWPS). The overall configuration is composed of two converters: (1) a modified bridgeless SEPIC PFC converter, which is controlled by a PI controller to achieve a high power factor and fast response; and (2) a full bridge buck converter with high-frequency transformer for high-frequency isolation to ensure arc welding stability. The proposed system is simulated under different operating conditions of an AWPS. It is also tested in real time by a hardware-in-the-loop system based on a dSPACE DS1103 control board. The system performances are evaluated based on power quality indices such as power factor, total harmonic distortions of the AC grid current, and voltage regulation. The obtained results show that the proposed controller enhances the weld bead quality by keeping a constant current at the output and a stable arc, meet the international power quality standards and robustness for voltage regulation

PFC Topologies for AC to DC Converters in DC Micro-Grid

With increasing dominance of renewable energy resources and DC household appliances, the novelty of DC micro grid is attracting significant attention. The key interface between the main supply grid and DC micro grid is AC to DC converter. The conventional AC to DC converter with large output capacitor introduces undesirable power quality problems in the main supply current. It reduces system efficiency due to low power factor and high harmonic distortion. Power Factor Correction (PFC) circuits are used to make supply currents sinusoidal and in-phase with supply voltages. This paper presents different PFC topologies for single phase AC to DC converters which are analyzed for power factor (PF), total harmonic distortion (THD) and system efficiency by varying output power. Two-quadrant shunt active filter topology attains a power factor of 0.999, 3.03% THD and 98% system efficiency. Output voltage regulation of the presented active PFC topologies is simulated by applying a step load. Two-quadrant shunt active filter achieves better output voltage regulation compared to other topologies and can be used as grid interface

High Step-Down Bridgeless Sepic/Cuk PFC Rectifiers With Improved Efficiency and Reduced Current Stress

In this article, two high step-down bridgeless power factor correction rectifiers based on the switched inductor network (SIN) are introduced. The proposed rectifiers employ the SIN to provide high step-down voltage gain with a higher duty cycle than the competitors. They also offer higher efficiency, lower current stress, and total peak switching device powers. A thorough and straightforward design algorithm in the discontinuous conduction mode is provided that ensures a unity power factor and a low total harmonic distortion with a simple control scheme. As a demonstration of the superior performance of the proposed rectifiers, a 300-W high-gain sepic rectifier setup with 48Vdc output voltage from a 230Vrms/50Hz source is built in the laboratory

Bridgeless Step/Up Unity Power Factor Rectifier for High Voltage Applications

Power electronic devices with front- end rectifier are widely used in computer, communication and electric vehicle industries. These rectifiers are nonlinear in nature and generate current harmonics which pollute utility power. International harmonic standards (e.g., IEC 61000-3-2 and EN 61000-3-2) have been put in place to confine power pollution. These standards limit the current harmonics generated by loads to a specified threshold depending on load power and application. In other words, a high power factor is required. Power supplies with active power factor correction (PFC) techniques are becoming necessary for many types of electronic equipment to meet the harmonic regulations and standards. However, classical PFC schemes have lower efficiency due to significant losses in the diode bridge. Several bridgeless topologies have been introduced to decrease diode bridge conduction losses. Most of the step-up PFC rectifiers utilize boost converter at their front end due to its natural PFC capability. In this thesis, a new bridgeless PFC topology based on Cuk converter is presented. Similar to Cuk converter, the proposed topology offers several advantages in PFC applications, such as easy implementation of transformer isolation, inherent inrush current limitation during start-up and overload conditions, and lower electromagnetic interference (EMI). These advantages make the proposed topology a viable solution for high voltage DC loads such as electric vehicle battery charger. Chapter III presents steady state analysis for the proposed rectifier. The rectifier is analyzed only during the positive half of the line frequency due to symmetry. Design procedure, simulation and measurements to verify the capability of the rectifier are presented in Chapter IV. Harmonics content and efficiency of the proposed rectifier versus conventional Cuk full bridge PFC rectifier are also presented

Bridgeless SEPIC Converter Based Computer Power Supply Using Coupled Inductor

Switched Mode Power Supplies (SMPS) are used as power source for computers. Conventional SMPS used in computers are suffered by some serious problems such as poor power quality, high device stress, slow dynamic response, high harmonic contents, periodically dense, peak currents, distorted input current. To minimize these problems, a non-isolated bridgeless buck-boost single ended primary inductance converter (SEPIC) using coupled inductor is introduced at the front end of the SMPS, which is operated in discontinuous conduction mode (DCM). This proposed technique reduces the Total Harmonic Distortion(THD), which results in power factor improvement. The DC output voltage of the SMPS is almost a constant voltage which is regulated by means of the proposed SEPIC converter. For obtaining different dc voltage levels for the PC applications, the output of the front end SEPIC converter is fed to the half-bridge DC-DC converter. The output voltages of the SMPS are controlled by controlling any one of the output voltages. Design and simulation of the proposed converter are carried out using the MATLAB/simulink software