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Abstract-For the sake of energy saving, harmonic current suppression and drive performance improvement, Bridgeless PFC circuit topologies are used more and more extensively. The implementation of a bridgeless power factor correction (PFC) boost rectifier with low common-mode noise is presented in this paper. The proposed method is compared with conventional method. The proposed implementation employs a unique multiple-winding, multicore inductor to increase the utilization of the magnetic material. Open and closed loop model is developed and simulated. The simulation results justify the theoretical analysis.
Index Terms-Boost converter, bridgeless, magnetic integration, power factor correction (PFC).
TO maximize the power supply efficiency, bridgeless power factor correction (PFC) circuit topologies that may reduce the conduction loss by reducing the number of semiconductor components in the line-current path have been introduced. The bridgeless PFC boost implementations have received the most attention all over. Bridgeless PFC is one of the options to meet these new requirements. The main goal of this paper is to present a bridgeless solution that is relatively easy to implement in the sense that it does not require any specific controller and the operation remains very similar to that of a conventional PFC. The major drawback of the conventional PFC is the low utilization of switches and magnetic components. The proposed implementation employs a unique multiple-winding, multicore inductor to increase the utilization of the magnetic material. In this paper, a systematic review of the bridgeless PFC boost rectifier and proposed implementation employs unique multiple-winding, multicore inductor implementations that have received the most attention is presented. Performance comparison between the conventional bridgeless PFC boost rectifier and a representative member of the bridgeless PFC boost rectifier with multicore inductor is performed. Open and closed loop controlled modeled is developed for the proposed system.
II. Bridgeless PFC converter WITH COMMON-CORE INDUCTORS
The bridgeless PFC boost rectifier in Fig.01 consists of two boost PFC rectifiers, each operating during a half line cycle. One boost rectifier operates while the other boost rectifier is idle. As a result, the utilization of switches and magnetic components is only one-half of that of the conventional PFC boost converter that always utilizes all the components during the entire line cycle. The low utilization of the components may be a serious penalty in terms of weight, power density, and cost. However, the utilization can be improved by minimizing the number of components through component integration. As discussed the number of components can be reduced by integrating magnetic components such as transformers and inductors on the same core. The utilization of the magnetic components in the circuit in Fig.01 can be significantly improved by employing a unique multiple-winding, multicore inductor structure. The circuit diagram of this implementation of the dual-boost PFC rectifier is shown in Fig.02.
Fig.01. Bridgeless PFC boost converter
Fig.02. Proposed dual-boost PFC rectifier with common-
Fig.03. Two-winding integrated magnetic device with the
decoupled energy storage.
As shown in Fig.03, boost inductor LB consists of a first winding, a second winding, and two cores. The first winding (NA) consists of series-connected windings NA1 and NA2. The second winding (NB) consists of series-connected windings NB1 and NB2. Windings NA1 and NB1 are wound on the first core in the same direction. However, windings NA2 and NB2 are wound on the second core in opposite directions. To facilitate the explanation of the magnetic element, Fig.04 shows the simplified symbol of the integrated magnetic device in Fig.03 with the polarity mark of each winding. Moreover, Fig.05 shows the integrated magnetic device in Fig.03 with reference directions of currents and magnetic flux as current iA flows through winding NA. To make the two windings magnetically independent of each other, windings NA1 and NA2 should have an equal number of turns, i.e., NA1 = NA2 . In addition, windings NB1 and NB2should also have an equal number of turns, i.e., NB1 and NB2. As can be seen in Fig.05, current iA generates magnetic flux Ï†A=NA X iA in each core.
Fig.04. Simplified symbol of the magnetic device
The change of flux Ï†A induces the current in windings NB1 and NB2 in each core. Because of the opposite winding directions and the equal number of turns of NB1 and NB2, the induced currents in windings NB1 and NB2 have opposite directions and equal magnitudes. As a result, the total current of winding NB is zero, i.e., iB = 0. Similarly, current iA is zero when current iB flows in winding NB. As a result, the first winding and the second winding are magnetically independent and can be used as two different inductors. As shown in Fig.02, during the period when ac input voltage Vac is positive, the boost rectifier that consists of switch S1 , diodes D1 and D4 , and windings NA1 and NA2 operates to deliver energy to the output, while the boost rectifier that consists of switch S2 , diodes D2 and D3 , and windings NB1 and NB2 is idle.
Fig.05. Integrated magnetic device
It should be noted that the two cores on which windings NA1 and NA2 are wound are fully utilized although windings NB1 and NB2 are idle. Similarly, during the period when ac input voltage Vac is negative, the boost rectifier that consists of switch S2 , diodes D2 and D3 , and windings NB1 and NB2 operates to deliver energy to the output, while the boost rectifier that consists of switch S1 , diodes D1 and D4 , and windings NA1 and NA2 is idle. It should be also noted that the two cores are still fully utilized by windings NB1 and NB2 although windings NA1 and NA2 are idle. As a result, the high utilization of the magnetic cores significantly improves power density and reduces the overall weight of the power supply. While windings NA1, NA2, NB1 and NB2 can be easily manufactured with an equal number of turns, the cross-sectional area and permeability of magnetic cores exhibit small differences within the specified manufacturing tolerances. As a result of this difference in the core parameters, the magnetizing inductances of the two coupled inductors may not be the same so that the cancellation of the currents in the inactive windings (windings NB1 and NB2 during positive line half cycles and NA1 and NA2 during negative line half cycles) may not be perfect. However, the lack of a perfect current cancellation in the inactive windings has virtually no effect on the electromagnetic interference (EMI) performance of the circuit in Fig.02 since return diodes D3 and D4 always provide low-impedance current path for the return current, i.e., they always connect the load directly to the source. The effect of the mismatched magnetizing inductance of the cores is observed as a current flow of the switching-frequency component of the return current (ripple current) through the inactive winding. It should also be noted that in bridgeless boost PFC implementations with the return diodes, the line-frequency return current divides between the path through a return diode and the path through the inactive switch and inductor in accordance to the low-frequency (dc) impedances of this two paths. According to this analysis, for gapped cores that typically exhibit magnetizing inductance tolerances in the Â±10 range, only 10% of the ripple current returns through the inactive windings. Such a small current has virtually no effect on the performance of the circuit, i.e., it practically does not affect the efficiency or EMI of the circuit. Finally, the leakage inductance of the coupled inductors has no effect on the operation and performance of the circuit, and can be neglected.
III. Simulation Results Analysis.
Simulation is done using Matlab Simulink and the results are presented. The dual boost converter is shown in Fig.6.a.The corresponding AC input voltage and current waveforms are shown in Fig.6.b. It can be seen that the current and voltage are almost in phase. The acceptance of the implementation in practical applications is hampered by a high common-mode noise produced by high-frequency switching of S1 and S2. The major drawback of the rectifier is the low utilization of switches and magnetic components.
Fig.06.a. Simulation circuit of dual boost converter
Fig.6.b. AC input voltage and current
Modified dual-boost PFC rectifier with common-core inductors is shown in Fig.7.a. It is assumed that a controlled switch is implemented as the power MOSFET with its inherently slow body diode. Voltage across the MOSFET's 1& 2 are shown in Fig.7.b respectively. Ac input voltage and current are shown in Fig.7.c. DC output current and output voltage are shown in Figs.7.d and 7.e respectively. Open loop controlled dual-boost PFC rectifier with common-core inductors circuit is shown in Fig 8.a. A disturbance in input voltage as well as in the DC output voltage is shown in Figs.8.b and 8.c.In Open loop control no proper controller is present.
Fig.07.a. Simulation circuit of dual boost converter with
Fig.07.b. Voltage across the MOSFET's 1& 2
Fig.7.c. Proposed circuit -AC input voltage and current
Fig.7.d. DC Output Current
Fig.7.e. DC Output Voltage
Fig.08.a. Open loop circuit of dual boost converter with
Fig.08.b. Ac input voltage with disturbance
Closed loop system is shown in Fig.9.a. Output voltage is sensed and it is compared with a reference voltage. The error is processed through a PI controller. There is a step rise in input voltage for closed loop system. The output of the pulse generator controls the output voltage till it reaches the set value. It can be seen that the DC voltage reaches the set value as shown in Fig.9.b. The comparison of input voltage for conventional and proposed method is shown in Fig.9.c.
Fig.08.c. DC Output voltage with disturbance
Fig.09.a. Closed loop circuit of dual boost converter
with inductor core.
Fig.09.b. Output voltage with disturbance
Bridgeless PFC Converter with magnetic utilization is modeled and simulated using Matlab. Open loop and closed loop models are developed and they are used successfully for simulation. The simulation studies indicate that the dual-boost PFC rectifier employs a multiple-winding magnetic device to increase the utilization of the magnetic core. The performance of the proposed rectifier was verified on Matlab Simulink. The proposed technique improves the efficiency by approximately 1% compared to the conventional PFC boost rectifier, and improves the utilization of the magnetic cores from the conventional bridgeless dual-boost rectifier, resulting in a low-cost high-power-density design.
Fig.09.c. Comparison of input voltage for conventional
and proposed method