EPE Association: EPE 1999 - Topic 03e: Power Factor Correction

EPE 1999 - Topic 03e: Power Factor Correction
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1999 - Conference > EPE 1999 - Topic 03: POWER SUPPLIES > EPE 1999 - Topic 03e: Power Factor Correction

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   A New Unity Power Factor AC/DC Converter Based on Energy Recirculation
By O. Lopez Lapena; L. Garcia de Vicuña; J. Matas; M. Castilla; M. López [View]
[Download]

Abstract: A novel Unity Power Factor converter based on energy recirculation is proposed together with its control design. A new three-position switch is used to obtain a major control on the converter dynamics without increasing the conduction and switching losses from the conventional two-position switch. The new converter provides low input current distortion and inrush current during the start-up, as well as good power factor and robustness with regards to external disturbances. Full theoretical analysis and simulations are presented.

   A Novel Constantly-Sampled Sinusoidal-Input Single-Phase Rectifier with Two Switched-Valve-Devices Employed
By M. Ohshima; R. Saito; S. Ushiki [View]
[Download]

Abstract: A non-uniformly connected single-phase rectifier with a novel constantly-sampled PWM scheme is trially fabricated and experimentally examined, the ratings of which are a.c. 100 V input, d.c. 200 V output, 1 kVA and a unity power factor. The applied PWM scheme ensures theoretically the maximum error of the actual a.c. current to the reference one, zero-cross distortion free and the minimum on-state and off-state time durations of main switches. Both high speed d.c. voltage response and less distortion of the a.c. input current are achieved by the PWM scheme with applying feedfoward control to the dc-AVR which functions as the upper stage of the PWM. 95% efficiency, 100% power factor and 2% a.c. current THD were measured. For full load shut-down, 1% and 20ms were obtained for the transient d.c. overshoot voltage and the settling time although the topology is unavailable for inverter operation. The rectifier demonstrated quick and excellent performance.

   A Simple Control Circuit for Dual Boost Rectifier Providing Sinusoidal Input Currents
By P. Pejovic [View]
[Download]

Abstract: In this paper, a novel circuit utilized to generate reference signals for current programming in the three-phase dual boost harmonic-free rectifier is proposed. The circuit is characterized by simplicity and by excellent rejection of zero-sequence harmonic components of the input voltages. Optimal current programming is provided. Analytically obtained results are verified on a 1.5 kW rectifier.

   A Unified Analysis of AC-to-DC Converters with Active Input Current Shaper
By J.Sebastián; A. Fernández; P.Villegas; M.M. Hernando; J.M. Alonso [View]
[Download]

Abstract: This paper deals with the steady-state analysis of ac-to-dc converters which use the recently proposed Active Input Current Shaper (AICS) to reduce the line current harmonics in order to comply with the IEC 1000-3-2 specifications. The main equations for many topologies directly derived from the standard ones (Forward, Flyback, SEPIC, Cuk, Half Bridge, Full Bridge, Push-Pull, Buck, Boost, Buck-Boost, etc.) have been obtained. Special attention must be paid in the case of the Buck topology, which can exhibit a voltage gain with positive and negative slope. Finally, some of the proposed topologies have been experimentally tested.

   Active Power Factor Correction of Diode Rectifiers using Output Filters with Diode-Switched and Harmonic-Resonant Stages
By T. Sakkos; V. Sarv [View]
[Download]

Abstract: Efficient two-stage hybrid output filters with diode-switched and harmonic-resonant stages for single- and three-phase diode rectifiers, to provide quasisinusoidal operation mode with close-to-unity power factor, are proposed, analyzed and verified. The harmonic reduction technique proposed is based on the ripple power factor conversion into the additional quantity of the dc output power. To verify the feasibility and usefulness of the proposed improved rectifier circuits, all new circuit configurations were tested using computer simulation. In addition, the correspondiong laboratory rectifiers were built and tested. In the experimental rectifiers power factor PF>= 0.99 were measured. The high values of the power factor hold in the wide range of the load variation.

   Analysis of a Three-Phase Rectifier Operating with a Six-Switch Current Pre-Charge Circuit
By D. Simonetti; J. L. F. Vieira; J. P. Rey [View]
[Download]

Abstract: A new approach to improve the input current profile of three-phase rectifiers is presented in this paper. To achieve this aim, an auxiliary circuit is used to impose current circulation during the time intervals that the rectifier does not absorb current. The additional switches are of low current capacity. Design equations are presented, as well as the operating characteristics. Experimental results corroborate the analysis carried out here.

   Closed-Loop PSPICE Simulation of a Unity Power Factor Off-Line Switcher with Non Linear Carrier Control
By F. Alonge; F. M. Raimondi; P. Scalia; G. Tortorici; A. Urso [View]
[Download]

Abstract: The closed loop PSPICE simulation of a 350W AC/DC isolated CUK converter, operating in Continuous Conduction Mode (CCM) with a Non Linear Carrier (NLC) Control to achieve input current shaping, is presented. Through the generation of special ideal blocks, heavy convergence problems are solved which allows to have at disposal a powerful and flexible instrument for the closed-loop simulation of various converter topologies. Complete discription of functional blocks and operation of the control loop are described. Results of simulation tests are shown.

   Comparison of Three Single-Stage Solutions for Low Cost PFC
By V. Tuomainen; V. Grigore; J. Wallius; J. Kyyrä [View]
[Download]

Abstract: This paper compares three single-stage solutions : BIFRED, BIBRED and Modified Dither. These circuits are able to produce an input current with low harmonic content and a regulated and isolated output voltage with only one switching stage. Useful equations to determine the behavior of the bulk capacitor voltage during any load condition are given. Practical power range of the converters and peak currents ratings are discussed in the paper and theoretical results are compared with a 200 W BIFRED prototype.

   Design and Implementation of a Low-Cost High-Power-Factor Battery-Charger Family for Lead-Acid Batteries
By J. Cardesín; J. M. Alonso; J. Sebastián [View]
[Download]

Abstract: A new low-cost off-line battery-charger family featuring high input power factor is presented in this paper. Typical average current mode control technique used in DC-to-DC converters has been applied to achieve an input power factor near unity. The low cost feature has been obtained by using a singlestage flyback topology since no very fast output response is necessary for lead-acid battery chargers. Design procedure and experimental results obtained at the laboratory are also presented.

   Differential Mode Current Harmonics Forecast for DCM Boost Rectifiers design
By J. C. Crebier; M. Brunello; J. P. Ferrieux [View]
[Download]

Abstract: This new method allows to forecast differential mode current harmonics of discontinuous current mode (DCM) rectifiers from the fundamental up to the switching frequency multiples. It is a lot faster than time domain simulations and it gives exact theoretical predictions. This allows design optimization because it takes into account control variables with respect to operation point. It is applicable to any kind of boost derived converters. Comparisons with experiments and simulations emphasize its interesting characteristics.

   Double PWM Control for Unity-Power-Factor Converters
By T. Ohnuki; O. Miyashita; K. Ohniwa; T. Fujimaki [View]
[Download]

Abstract: A new unity-power-factor converter with double PWM (pulsewidth modulation) control is presented. The converter consists of two PWM converter circuits in parallel: the main and auxiliary converter circuits. The main converter circuit, which is a boost converter controlled at relatively low frequencies, transfers almost all the power to the dc load. The auxiliary converter circuit, on the other hand, has a lower-power but higher-speed switching device and compensates the remainder that the main converter circuit leaves. Consequently, this double PWM converter acts as a converter with the power aspect determined by the main converter circuit and the frequency aspect determined by the auxiliary converter circuit. Steady-state and transient performance of the proposed converter are discussed. Experimental and simulation results show the usefulness of this converter.

   Novel One Stage Forward-type Power Factor Correction Circuit and Comparison of its Control Methods
By M. Nagao; R. Matsumoto; M. Nakahara; K. Harada [View]
[Download]

Abstract: A novel power factor correction circuits and its control methods have been proposed which are simply constructed by one stage using a single forward converter. This PFC has functions of high power factor and suppression of the output voltage ripple. The high power factor is accomplished by operation of the discontinuous conduction mode, and the suppression of the output voltage ripple by using the exciting energy of the transofmer in the forward converter. Two control methods is considered by inserting the exciting energy for the ripple compensation. In this paper the characteristics of these two methods are compared with the SCAT simulator and the experiments.

   Novel Single-Stage Low-Cost Soft-Switched Off-Line Converter with PFC
By D. O'Sullivan; M.G. Egan; M. Willers. [View]
[Download]

Abstract: A single-stage, isolated, low cost, LC resonant based power supply circuit incorporating power factor correction and output voltage hold-up is proposed. Advantages of this topology include soft switching of power devices, close output voltage regulation and control loop simplicity. The recently introduced Rectifier Compensated Fundamental Mode Analysis (RCFMA) method is used to provide an accurate yet simple analysis of the circuit. The accuracy of this analysis method is shown in a comparison with results from a 5V, 20A prototype. Compliance with input current harmonic regulations is demonstrated and overall performance is assessed.

   Single-Phase High Power Factor Pre-regulator with Multilevel PWM
By B.-R. Lin; H-H Lu [View]
[Download]

Abstract: A new control scheme for the single-phase rectifier with three-level voltage pattern is proposed. A power factor corrector to improve the power quality is presented. A hysteresis current control (HCC) is adopted to control the line current with high power factor and low harmonic distortion. The line current command is derived from a dc link voltage regulator and an output power estimator. The major advantage of using three-level instead of two-level voltage pattern is that the blocking voltage of each power device is clamping to half of the dc link voltage. Based on the region detector of the line voltage, capacitor compensator and hysteresis comparator, the proposed control scheme is used to drive the line current with high power factor and low current distortion. The proposed scheme is verified by software simulations and experimental results from a laboratory prototype.

   The Three-Phase Interleaved Boost Rectifier: Study and Comparison
By J.-C. Crebier; D. Buzon; M. Brunello; J.-P. Ferrieux [View]
[Download]

Abstract: The three-phase interleaved boost rectifier operating in discontinuous current mode (DCM) is studied and characterized. It presents advantages compared with classical DCM boost rectifiers. Better power factor correction (PFC), reduced high frequency harmonics, lower output voltage, and greater efficiency are the main ones. Easy to control, it draws continuous courant mode input currents. It is suitable for medium power switch mode power supplies.

   Three Phase Power Factor Correction Converter for Aerospace Application
By K.W.E. Cheng; H. Y. Wang; D. Sutanto [View]
[Download]

Abstract: This paper is to present a 3 phase power factor correction circuit for the aerospace application. It describes the major concern of the AC/DC converters in the power conditioning system of the aerospace industry. The main features are the high power density and the leliability of the circuit. Simulation and experimental results are shown to verify the theoretical performance. Comparison of the proposed converter to other converters such as modular approach are presented.

   Three-Phase Unity Power Factor AC/DC Converter with Dual Isolated DC/DC Converter for a Battery Charger
By J. Herminjard [View]
[Download]

Abstract: In this article the development and realization of a 8 kW battery charger with Power Factor Correction (PFC) is described. The converter consists of two parts: The first part is an AC/DC converter based on a “VIENNA” topology with a controlled output voltage of 700V and midpoint connection [1],[2]. The second part consists of two DC/DC converters with galvanic isolation and parallel outputs. The output current and voltage can be controlled in the ranges 0-28A and 0-280V.

   Three-Phase, Three-Level PFC Circuit with Tri-Directional Switches
By D. Carlton; W. G. Dunford; M. Edmunds [View]
[Download]

Abstract: The three-phase, three-level boost Power Factor Correction circuit with tri-directional switches is proposed. The performance analysis in Continuous Conduction Mode operation is carried out using the space vector technique. Several types of switches could be implemented and the resulting space vector diagrams are presented for each case. the increase in the number of available vectors renders new modulation features to the circuit.

   Topologies for Power Factor Correction with Reduced Conduction Losses
By V. Grigore;J. Kyyrä [View]
[Download]

Abstract: A rectifier with Power Factor Correction (PFC) usually consists of a diode bridge, PFC stage and output voltage regulation stage. This paper investigates the possibility of integrating the functions of the rectifier diode bridge and the PFC stage. Rather than reducing component count, such integration aims at diminishing conduction losses by reducing the number of switches in the power path. In this paper, the widely used topology consisting of a diode bridge followed by a Boost converter is used as a reference. Three other topologies derived from this one, which have fewer switches in the power path, are presented and analyzed. Besides these Boost-derived topologies, a converter able to operate with bipolar input voltage is presented and its usefulness for power factor correction is assessed. Finally, a comparison between the analyzed topologies is presented.

EPE 1999 - Topic 03e: Power Factor Correction
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1999 - Conference > EPE 1999 - Topic 03: POWER SUPPLIES > EPE 1999 - Topic 03e: Power Factor Correction
	[return to parent folder]

	A New Unity Power Factor AC/DC Converter Based on Energy Recirculation By O. Lopez Lapena; L. Garcia de Vicuña; J. Matas; M. Castilla; M. López	[View] [Download]
Abstract: A novel Unity Power Factor converter based on energy recirculation is proposed together with its control design. A new three-position switch is used to obtain a major control on the converter dynamics without increasing the conduction and switching losses from the conventional two-position switch. The new converter provides low input current distortion and inrush current during the start-up, as well as good power factor and robustness with regards to external disturbances. Full theoretical analysis and simulations are presented.

	A Novel Constantly-Sampled Sinusoidal-Input Single-Phase Rectifier with Two Switched-Valve-Devices Employed By M. Ohshima; R. Saito; S. Ushiki	[View] [Download]
Abstract: A non-uniformly connected single-phase rectifier with a novel constantly-sampled PWM scheme is trially fabricated and experimentally examined, the ratings of which are a.c. 100 V input, d.c. 200 V output, 1 kVA and a unity power factor. The applied PWM scheme ensures theoretically the maximum error of the actual a.c. current to the reference one, zero-cross distortion free and the minimum on-state and off-state time durations of main switches. Both high speed d.c. voltage response and less distortion of the a.c. input current are achieved by the PWM scheme with applying feedfoward control to the dc-AVR which functions as the upper stage of the PWM. 95% efficiency, 100% power factor and 2% a.c. current THD were measured. For full load shut-down, 1% and 20ms were obtained for the transient d.c. overshoot voltage and the settling time although the topology is unavailable for inverter operation. The rectifier demonstrated quick and excellent performance.

	A Simple Control Circuit for Dual Boost Rectifier Providing Sinusoidal Input Currents By P. Pejovic	[View] [Download]
Abstract: In this paper, a novel circuit utilized to generate reference signals for current programming in the three-phase dual boost harmonic-free rectifier is proposed. The circuit is characterized by simplicity and by excellent rejection of zero-sequence harmonic components of the input voltages. Optimal current programming is provided. Analytically obtained results are verified on a 1.5 kW rectifier.

	A Unified Analysis of AC-to-DC Converters with Active Input Current Shaper By J.Sebastián; A. Fernández; P.Villegas; M.M. Hernando; J.M. Alonso	[View] [Download]
Abstract: This paper deals with the steady-state analysis of ac-to-dc converters which use the recently proposed Active Input Current Shaper (AICS) to reduce the line current harmonics in order to comply with the IEC 1000-3-2 specifications. The main equations for many topologies directly derived from the standard ones (Forward, Flyback, SEPIC, Cuk, Half Bridge, Full Bridge, Push-Pull, Buck, Boost, Buck-Boost, etc.) have been obtained. Special attention must be paid in the case of the Buck topology, which can exhibit a voltage gain with positive and negative slope. Finally, some of the proposed topologies have been experimentally tested.

	Active Power Factor Correction of Diode Rectifiers using Output Filters with Diode-Switched and Harmonic-Resonant Stages By T. Sakkos; V. Sarv	[View] [Download]
Abstract: Efficient two-stage hybrid output filters with diode-switched and harmonic-resonant stages for single- and three-phase diode rectifiers, to provide quasisinusoidal operation mode with close-to-unity power factor, are proposed, analyzed and verified. The harmonic reduction technique proposed is based on the ripple power factor conversion into the additional quantity of the dc output power. To verify the feasibility and usefulness of the proposed improved rectifier circuits, all new circuit configurations were tested using computer simulation. In addition, the correspondiong laboratory rectifiers were built and tested. In the experimental rectifiers power factor PF>= 0.99 were measured. The high values of the power factor hold in the wide range of the load variation.

	Analysis of a Three-Phase Rectifier Operating with a Six-Switch Current Pre-Charge Circuit By D. Simonetti; J. L. F. Vieira; J. P. Rey	[View] [Download]
Abstract: A new approach to improve the input current profile of three-phase rectifiers is presented in this paper. To achieve this aim, an auxiliary circuit is used to impose current circulation during the time intervals that the rectifier does not absorb current. The additional switches are of low current capacity. Design equations are presented, as well as the operating characteristics. Experimental results corroborate the analysis carried out here.

	Closed-Loop PSPICE Simulation of a Unity Power Factor Off-Line Switcher with Non Linear Carrier Control By F. Alonge; F. M. Raimondi; P. Scalia; G. Tortorici; A. Urso	[View] [Download]
Abstract: The closed loop PSPICE simulation of a 350W AC/DC isolated CUK converter, operating in Continuous Conduction Mode (CCM) with a Non Linear Carrier (NLC) Control to achieve input current shaping, is presented. Through the generation of special ideal blocks, heavy convergence problems are solved which allows to have at disposal a powerful and flexible instrument for the closed-loop simulation of various converter topologies. Complete discription of functional blocks and operation of the control loop are described. Results of simulation tests are shown.

	Comparison of Three Single-Stage Solutions for Low Cost PFC By V. Tuomainen; V. Grigore; J. Wallius; J. Kyyrä	[View] [Download]
Abstract: This paper compares three single-stage solutions : BIFRED, BIBRED and Modified Dither. These circuits are able to produce an input current with low harmonic content and a regulated and isolated output voltage with only one switching stage. Useful equations to determine the behavior of the bulk capacitor voltage during any load condition are given. Practical power range of the converters and peak currents ratings are discussed in the paper and theoretical results are compared with a 200 W BIFRED prototype.

	Design and Implementation of a Low-Cost High-Power-Factor Battery-Charger Family for Lead-Acid Batteries By J. Cardesín; J. M. Alonso; J. Sebastián	[View] [Download]
Abstract: A new low-cost off-line battery-charger family featuring high input power factor is presented in this paper. Typical average current mode control technique used in DC-to-DC converters has been applied to achieve an input power factor near unity. The low cost feature has been obtained by using a singlestage flyback topology since no very fast output response is necessary for lead-acid battery chargers. Design procedure and experimental results obtained at the laboratory are also presented.

	Differential Mode Current Harmonics Forecast for DCM Boost Rectifiers design By J. C. Crebier; M. Brunello; J. P. Ferrieux	[View] [Download]
Abstract: This new method allows to forecast differential mode current harmonics of discontinuous current mode (DCM) rectifiers from the fundamental up to the switching frequency multiples. It is a lot faster than time domain simulations and it gives exact theoretical predictions. This allows design optimization because it takes into account control variables with respect to operation point. It is applicable to any kind of boost derived converters. Comparisons with experiments and simulations emphasize its interesting characteristics.

	Double PWM Control for Unity-Power-Factor Converters By T. Ohnuki; O. Miyashita; K. Ohniwa; T. Fujimaki	[View] [Download]
Abstract: A new unity-power-factor converter with double PWM (pulsewidth modulation) control is presented. The converter consists of two PWM converter circuits in parallel: the main and auxiliary converter circuits. The main converter circuit, which is a boost converter controlled at relatively low frequencies, transfers almost all the power to the dc load. The auxiliary converter circuit, on the other hand, has a lower-power but higher-speed switching device and compensates the remainder that the main converter circuit leaves. Consequently, this double PWM converter acts as a converter with the power aspect determined by the main converter circuit and the frequency aspect determined by the auxiliary converter circuit. Steady-state and transient performance of the proposed converter are discussed. Experimental and simulation results show the usefulness of this converter.

	Novel One Stage Forward-type Power Factor Correction Circuit and Comparison of its Control Methods By M. Nagao; R. Matsumoto; M. Nakahara; K. Harada	[View] [Download]
Abstract: A novel power factor correction circuits and its control methods have been proposed which are simply constructed by one stage using a single forward converter. This PFC has functions of high power factor and suppression of the output voltage ripple. The high power factor is accomplished by operation of the discontinuous conduction mode, and the suppression of the output voltage ripple by using the exciting energy of the transofmer in the forward converter. Two control methods is considered by inserting the exciting energy for the ripple compensation. In this paper the characteristics of these two methods are compared with the SCAT simulator and the experiments.

	Novel Single-Stage Low-Cost Soft-Switched Off-Line Converter with PFC By D. O'Sullivan; M.G. Egan; M. Willers.	[View] [Download]
Abstract: A single-stage, isolated, low cost, LC resonant based power supply circuit incorporating power factor correction and output voltage hold-up is proposed. Advantages of this topology include soft switching of power devices, close output voltage regulation and control loop simplicity. The recently introduced Rectifier Compensated Fundamental Mode Analysis (RCFMA) method is used to provide an accurate yet simple analysis of the circuit. The accuracy of this analysis method is shown in a comparison with results from a 5V, 20A prototype. Compliance with input current harmonic regulations is demonstrated and overall performance is assessed.

	Single-Phase High Power Factor Pre-regulator with Multilevel PWM By B.-R. Lin; H-H Lu	[View] [Download]
Abstract: A new control scheme for the single-phase rectifier with three-level voltage pattern is proposed. A power factor corrector to improve the power quality is presented. A hysteresis current control (HCC) is adopted to control the line current with high power factor and low harmonic distortion. The line current command is derived from a dc link voltage regulator and an output power estimator. The major advantage of using three-level instead of two-level voltage pattern is that the blocking voltage of each power device is clamping to half of the dc link voltage. Based on the region detector of the line voltage, capacitor compensator and hysteresis comparator, the proposed control scheme is used to drive the line current with high power factor and low current distortion. The proposed scheme is verified by software simulations and experimental results from a laboratory prototype.

	The Three-Phase Interleaved Boost Rectifier: Study and Comparison By J.-C. Crebier; D. Buzon; M. Brunello; J.-P. Ferrieux	[View] [Download]
Abstract: The three-phase interleaved boost rectifier operating in discontinuous current mode (DCM) is studied and characterized. It presents advantages compared with classical DCM boost rectifiers. Better power factor correction (PFC), reduced high frequency harmonics, lower output voltage, and greater efficiency are the main ones. Easy to control, it draws continuous courant mode input currents. It is suitable for medium power switch mode power supplies.

	Three Phase Power Factor Correction Converter for Aerospace Application By K.W.E. Cheng; H. Y. Wang; D. Sutanto	[View] [Download]
Abstract: This paper is to present a 3 phase power factor correction circuit for the aerospace application. It describes the major concern of the AC/DC converters in the power conditioning system of the aerospace industry. The main features are the high power density and the leliability of the circuit. Simulation and experimental results are shown to verify the theoretical performance. Comparison of the proposed converter to other converters such as modular approach are presented.

	Three-Phase Unity Power Factor AC/DC Converter with Dual Isolated DC/DC Converter for a Battery Charger By J. Herminjard	[View] [Download]
Abstract: In this article the development and realization of a 8 kW battery charger with Power Factor Correction (PFC) is described. The converter consists of two parts: The first part is an AC/DC converter based on a “VIENNA” topology with a controlled output voltage of 700V and midpoint connection [1],[2]. The second part consists of two DC/DC converters with galvanic isolation and parallel outputs. The output current and voltage can be controlled in the ranges 0-28A and 0-280V.

	Three-Phase, Three-Level PFC Circuit with Tri-Directional Switches By D. Carlton; W. G. Dunford; M. Edmunds	[View] [Download]
Abstract: The three-phase, three-level boost Power Factor Correction circuit with tri-directional switches is proposed. The performance analysis in Continuous Conduction Mode operation is carried out using the space vector technique. Several types of switches could be implemented and the resulting space vector diagrams are presented for each case. the increase in the number of available vectors renders new modulation features to the circuit.

	Topologies for Power Factor Correction with Reduced Conduction Losses By V. Grigore;J. Kyyrä	[View] [Download]
Abstract: A rectifier with Power Factor Correction (PFC) usually consists of a diode bridge, PFC stage and output voltage regulation stage. This paper investigates the possibility of integrating the functions of the rectifier diode bridge and the PFC stage. Rather than reducing component count, such integration aims at diminishing conduction losses by reducing the number of switches in the power path. In this paper, the widely used topology consisting of a diode bridge followed by a Boost converter is used as a reference. Three other topologies derived from this one, which have fewer switches in the power path, are presented and analyzed. Besides these Boost-derived topologies, a converter able to operate with bipolar input voltage is presented and its usefulness for power factor correction is assessed. Finally, a comparison between the analyzed topologies is presented.