# Study on a Novel High-Efficiency Bridgeless PFC Converter

Authors: Cao Taiqiang; Chen Zhangyong; Wang Jun; Sun Zhang; Luo Qian; Zhang Fei
Journal: Journal of Applied Mathematics
 (2014)

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## Abstract

In order to implement a high-efficiency bridgeless power factor correction converter, a new topology and operation principles of continuous conduction mode (CCM) and DC steady-state character of the converter are analyzed, which show that the converter not only has bipolar-gain characteristic but also has the same characteristic as the traditional Boost converter, while the voltage transfer ratio is not related with the resonant branch parameters and switching frequency. Based on the above topology, a novel bridgeless Bipolar-Gain Pseudo-Boost PFC converter is proposed. With this converter, the diode rectifier bridge of traditional AC-DC converter is eliminated, and zero-current switching of fast recovery diode is achieved. Thus, the efficiency is improved. Next, we also propose the one-cycle control policy of this converter. Finally, experiments are provided to verify the accuracy and feasibility of the proposed converter.


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## Body

## 1. Introduction

A great number of harmonic currents, which are caused by nonlinear loads connected to grid, are main pollution sources of power system and important factors in the safe operation of the grid. In order to reduce the harmonic pollution, the active power filter (APF) and power factor correction (PFC) are required, which are applied to control the harmonic and reactive current generated from rectifier loads. PFC converter can realize the AC input current control and DC output voltage control at the same frequency and phase with AC voltage, and thus it is widely used in server power [1–8], charger, UPS, and so on. Traditional PFC converter includes a front-end bridge rectifier, which increases conduction loss and greatly affects the efficiency of the PFC converter. Moreover, more serious loss is generated under low input voltage and light load particularly [5, 9–13].In order to improve efficiency of the traditional PFC converter, an effective method named as bridgeless PFC technology without front-end bridge rectifier is proposed [3, 14, 15]. Then the bridgeless PFC converter is proposed in [1–18], which uses two switches instead of the uncontrolled diodes. When AC input voltage is in positive half-cycle, the front bridge leg of the converter operations, while AC input voltage is in negative half-cycle, the rear bridge leg operations. The papers report that the bridgeless PFC converter adopts the same two DC-DC converters to implement the power conversion for positive and negative half-cycle of AC input voltage, respectively. Another bridgeless PFC converter makes the input voltage greater than zero at first and then obtains steady output voltage through the DC-DC converter. All of these bridgeless PFC converters have a higher cost, require complex topology, and may lead to serious electromagnetic inference (EMI) [3, 13–18].In this paper, we research a novel Pseudo-Boost converter, which has bipolar-gain characteristic; that is, no matter if the input voltage is positive or negative, the output voltage is always positive, and the converter also has the same characteristic as the traditional Boost converter. Although the converter has a resonant branch, the difference from the traditional resonant converter is that the voltage transfer ratio is not relevant to the resonant branch parameters and switching frequency; it only depends on the switching duty cycle. Based on the Bipolar-Gain Pseudo-Boost converter, a bridgeless Bipolar-Gain Pseudo-Boost PFC converter in continuous conduction mode (CCM) is investigated. The converter adopts one bidirectional controllable switch and two fast-recovery diodes instead of bridge rectifier, and the zero-current switching of the fast-recovery diodes is achieved. Therefore, the efficiency of the converter is improved. Meanwhile, the one-cycle control technology is adopted to control the Bipolar-Gain Pseudo-Boost PFC converter.


## 2. Operation Principle of Bipolar-Gain Pseudo-Boost Converter

The topology of the Bipolar-Gain Pseudo-Boost converter consists of switchS, two recovery diodes D1 and D2, resonant capacitor Cr, and resonant inductor Lr, as in Figure 1. When the input voltage is positive or negative, the output voltage of traditional Boost converter is the corresponding polarity. Compared with the traditional one, the output voltage of Bipolar-Gain Pseudo-Boost converter is just positive; that is, the Bipolar-Gain Pseudo-Boost has bipolar-gain characteristic. To simplify the analysis of the operation of the Bipolar-Gain Pseudo-Boost converter, the following assumptions are made.(a)
All of the switches, diodes, inductors, and capacitors are ideal.(b)
Output capacitorCo is large enough to make the output voltage keep constant in a switching cycle.(c)
Resonant inductorLr and resonant capacitor Cr are much smaller than the inductor L and output capacitor Co, respectively.(d)
The converter operates in CCM.Figure 1
The topology of Bipolar-Gain Pseudo-Boost converter.


### 2.1. Positive Input Voltage

The operation modes of Bipolar-Gain Pseudo-Boost converter operate in CCM with positive input voltage (Figure2). The corresponding key waveforms of the converter are shown in Figure 3. At the beginning of each switching cycle, the resonant inductor current iLr is zero and the initial value of resonant capacitor voltage vcr is Δvcr, where vc>Δvcr>0 exists.Equivalent circuit of operation mode of the converter with positive input voltage.
(a)
Mode 1
(b)
Mode 2
(c)
Mode 3Figure 3
The key waveform of the converter with positive input voltage.(1) Mode 1 [t0~t1]: as shown in Figures 2(a) and 3, at t=t0, the switch S is turned on. The voltage across the inductor L is equal to input voltage vin, which makes inductor current increase linearly. The resonant capacitor voltage vcr makes diode D1 turn on, and the reverse voltage across D2 makes it turn off. Resonant capacitor voltage vcr and resonant inductor current iLr are given as
(1)vcr=Δvcrcos⁡ωr(t-t0),iLr=-ΔvcrZnsinωr(t-t0),
where Zn=Lr/Cr, ωr=1/LrCr.(2) Mode 2 [t1~t2]: as shown in Figures 2(b) and 3, at t=t1=t0+Tr/2, resonant inductor current iLr is equal to zero and diode D1 gets zero-current turn-off, where Tr=2π/ωr is the resonant period. At this moment, the resonant capacitor is equal to -Δvcr. Due to vc>Δvcr, the diode D2 is still turned off with reverse voltage Δvcr-vc. The voltage across diode D1 is equal to vD1=-vcr=Δvcr, while the voltage across diode D2 is equal to vD2=vc-Δvcr.(3) Mode 3 [t2~t3]: as shown in Figures 2(c) and 3, at t=t2, the switch S is turned off. Because the inductor current iL does not change suddenly, the diode D2 is turned on to provide the path for the inductor current iL. The diode D1 is reversely biased and the voltage across it is equal to -vc, and the inductor L is then discharged and capacitor Co is charged. As Lr≪L, Lr can be ignored. So during t2~t3, the resonant capacitor voltage can be expressed as
(2)vcr=-Δvcr+iLCr(t-t2).When the resonant capacitor voltage rises toΔvcr, the converter begins to enter the next switch cycle.


### 2.2. Negative Input Voltage

Figure4 shows the operation modes of Bipolar-Gain Pseudo-Boost converter operated in CCM with negative input voltage. The corresponding key waveforms of the converter are shown in Figure 5. At the beginning of each switching cycle, the resonant inductor current iLr is zero and the initial value of resonant capacitor voltage vcr=-vc-Δvcr, where vc>Δvcr>0.Equivalent circuit of operation mode of the converter with negative input voltage.
(a)
Mode 4
(b)
Mode 5
(c)
Mode 6Figure 5
The key waveform of the converter with negative input voltage.(1) Mode 4 [t4~t5]: as shown in Figures 4(a) and 5, at t=t4, the switch S is turned on. The voltage across the inductor L is equal to input voltage -vin, which makes inductor current decrease linearly. The diode D2 is turned on by the opposite voltage Δvcr, and the diode D1 is reversely biased. The resonant branch begins to resonate; the resonant capacitor voltage vcr and resonant inductor current iLr are given as
(3)vcr=-vc-Δvcrcos⁡ωr(t-t4),iLr=ΔvcrZnsinωr(t-t4),
where Zn=Lr/Cr, ωr=1/LrCr.(2) Mode 5 [t5~t6]: as shown in Figures 4(b) and 5, at t=t5, the resonant inductor current iLr is equal to zero and diode D2 gets zero-current turn-off, where t5-t4=Tr/2 and Tr=2π/ωr is the resonant period. The resonant capacitor is equal to -vc+Δvcr, the diode D1 is still reversely biased, and the voltage across it is equal to vD1=-vcr=vc-Δvcr. The voltage across diode D2 is equal to Δvcr.(3) Mode 6 [t6~t7]: as shown in Figures 4(c) and 5, at t=t6, the switch S is turned off. Because the inductor current iL does not change suddenly, the diode D1 is turned on to provide the path for the inductor current iL. The diode D2 is reversely biased, and the inductor L is then discharged and capacitor Co is charged. During t6~t7, the resonant capacitor voltage can be given as
(4)vcr=-vc+Δvcr-iLCr(t-t6).When the resonant capacitor voltage decreases to-vc-Δvcr, the converter begins to enter the next switch cycle.


## 2.1. Positive Input Voltage

The operation modes of Bipolar-Gain Pseudo-Boost converter operate in CCM with positive input voltage (Figure2). The corresponding key waveforms of the converter are shown in Figure 3. At the beginning of each switching cycle, the resonant inductor current iLr is zero and the initial value of resonant capacitor voltage vcr is Δvcr, where vc>Δvcr>0 exists.Equivalent circuit of operation mode of the converter with positive input voltage.
(a)
Mode 1
(b)
Mode 2
(c)
Mode 3Figure 3
The key waveform of the converter with positive input voltage.(1) Mode 1 [t0~t1]: as shown in Figures 2(a) and 3, at t=t0, the switch S is turned on. The voltage across the inductor L is equal to input voltage vin, which makes inductor current increase linearly. The resonant capacitor voltage vcr makes diode D1 turn on, and the reverse voltage across D2 makes it turn off. Resonant capacitor voltage vcr and resonant inductor current iLr are given as
(1)vcr=Δvcrcos⁡ωr(t-t0),iLr=-ΔvcrZnsinωr(t-t0),
where Zn=Lr/Cr, ωr=1/LrCr.(2) Mode 2 [t1~t2]: as shown in Figures 2(b) and 3, at t=t1=t0+Tr/2, resonant inductor current iLr is equal to zero and diode D1 gets zero-current turn-off, where Tr=2π/ωr is the resonant period. At this moment, the resonant capacitor is equal to -Δvcr. Due to vc>Δvcr, the diode D2 is still turned off with reverse voltage Δvcr-vc. The voltage across diode D1 is equal to vD1=-vcr=Δvcr, while the voltage across diode D2 is equal to vD2=vc-Δvcr.(3) Mode 3 [t2~t3]: as shown in Figures 2(c) and 3, at t=t2, the switch S is turned off. Because the inductor current iL does not change suddenly, the diode D2 is turned on to provide the path for the inductor current iL. The diode D1 is reversely biased and the voltage across it is equal to -vc, and the inductor L is then discharged and capacitor Co is charged. As Lr≪L, Lr can be ignored. So during t2~t3, the resonant capacitor voltage can be expressed as
(2)vcr=-Δvcr+iLCr(t-t2).When the resonant capacitor voltage rises toΔvcr, the converter begins to enter the next switch cycle.


## 2.2. Negative Input Voltage

Figure4 shows the operation modes of Bipolar-Gain Pseudo-Boost converter operated in CCM with negative input voltage. The corresponding key waveforms of the converter are shown in Figure 5. At the beginning of each switching cycle, the resonant inductor current iLr is zero and the initial value of resonant capacitor voltage vcr=-vc-Δvcr, where vc>Δvcr>0.Equivalent circuit of operation mode of the converter with negative input voltage.
(a)
Mode 4
(b)
Mode 5
(c)
Mode 6Figure 5
The key waveform of the converter with negative input voltage.(1) Mode 4 [t4~t5]: as shown in Figures 4(a) and 5, at t=t4, the switch S is turned on. The voltage across the inductor L is equal to input voltage -vin, which makes inductor current decrease linearly. The diode D2 is turned on by the opposite voltage Δvcr, and the diode D1 is reversely biased. The resonant branch begins to resonate; the resonant capacitor voltage vcr and resonant inductor current iLr are given as
(3)vcr=-vc-Δvcrcos⁡ωr(t-t4),iLr=ΔvcrZnsinωr(t-t4),
where Zn=Lr/Cr, ωr=1/LrCr.(2) Mode 5 [t5~t6]: as shown in Figures 4(b) and 5, at t=t5, the resonant inductor current iLr is equal to zero and diode D2 gets zero-current turn-off, where t5-t4=Tr/2 and Tr=2π/ωr is the resonant period. The resonant capacitor is equal to -vc+Δvcr, the diode D1 is still reversely biased, and the voltage across it is equal to vD1=-vcr=vc-Δvcr. The voltage across diode D2 is equal to Δvcr.(3) Mode 6 [t6~t7]: as shown in Figures 4(c) and 5, at t=t6, the switch S is turned off. Because the inductor current iL does not change suddenly, the diode D1 is turned on to provide the path for the inductor current iL. The diode D2 is reversely biased, and the inductor L is then discharged and capacitor Co is charged. During t6~t7, the resonant capacitor voltage can be given as
(4)vcr=-vc+Δvcr-iLCr(t-t6).When the resonant capacitor voltage decreases to-vc-Δvcr, the converter begins to enter the next switch cycle.


## 3. The Steady-State Analysis of Bipolar-Gain Pseudo-Boost Converter

There are four state variables in Bipolar-Gain Pseudo-Boost converter. One is the energy storage state variable(vc,iL), in which the natural frequency is much lower than the switching frequency. The other one is the resonant state variables (vcr,iLr), in which the natural frequency is close to the switching frequency. According to the generalized state space averaging (GSSA) approach, the GSSA equation of the converter can be established, which chooses vc, iL as state variables. Based on the GSSA equation, the steady-state characteristic can be analyzed.


### 3.1. Positive Input Voltage

For positive input voltage, from Figures2(a) and 2(b), when the switch S is turned on, the state differential equations are
(5)LdiLdt=vin,Codvcdt=-vcR.From Figure2(c), when the switch S is turned off, the corresponding state differential equations are
(6)(L+Lr)diLdt=vin-vc-vcr,Codvcdt=iL-vcR.The above analysis shows that the resonant capacitor voltage satisfies (2) when the switch S is turned off. From Figure 3, at the end of switching cycle, the resonant capacitor voltage is equal to Δvcr; meanwhile, the integration of the resonant capacitor voltage is zero.The matrix representation of the state variables isx=[iLvc]T; according to (5) and (6), the state space equation is
(7)x˙=Aix+Biu,i=1,2,
where
(8)A1=[000-1RCo],B1=[vinL0],A2=[0-1L+Lr1Co-1RCo],B2=[vin-vcrL+Lr0].According to GSSA approach, for positive input voltage, the GSSA equation of the Bipolar-Gain Pseudo-Boost converter can be obtained as(9)ddt[iLvc]=[0-(1-d)L+Lr(1-d)Co-1RCo][iLvc]+[vinL0],
where d is the transient state switching duty cycle.The equation(d/dt)[iLvc]=0 is founded at steady state because L≫Lr, so L+Lr≈L. From (9), there are
(10)vin=(1-D)vc,IL=vcR(1-D),
where D is the steady state switching duty cycle and IL is the steady state inductor current.


### 3.2. Negative Input Voltage

For negative input voltage, from Figure4(a), when the switch S is turned on, the state differential equations are
(11)LdiLdt=-vin,Codvcdt=iLr-vcR.From Figure4(b), when the switch S is turned on, the corresponding state differential equations are
(12)LdiLdt=-vin,Codvcdt=-vcR.From Figure4(c), when the switch S is turned off, the corresponding state differential equations are
(13)(L+Lr)diLdt=-vin-vcr,Codvcdt=-vcR.According to the above analysis, it can be seen that the resonant capacitor voltage satisfies (4) when the switch S is turned off. From Figure 5, at the end of switching cycle, the resonant capacitor voltage is equal to Δvcr-vc; thus, the integration of the resonant capacitor voltage is -vc in the time.The matrix representation of the state variables isx=[iLvc]T; according (11), (12), and (13), the state space equation is
(14)x˙=Aix+Biu,i=1,2,3,
where
(15)A1=[000-1RCo],B1=[-vinLiLrCo],A2=[000-1RCo],B2=[-vinL0],A3=[000-1RCo],B3=[-vin-vcrL+Lr0].Therefore, for negative input voltage, the GSSA equation of the Bipolar-Gain Pseudo-Boost converter can be obtained as(16)ddt[iLvc]=[000-1RCo][iLvc]+[-vinL+vcL(1-d)iL(1-d)Co].The equation(d/dt)[iLvc]=0 is founded at steady state because L≫Lr, so L+Lr≈L. From (16), there are
(17)vin=(1-D)vc,IL=vcR(1-D).According to (10) and (17), no matter if the input voltage is positive or negative, the voltage transfer ratios of Bipolar-Gain Pseudo-Boost converter keep the same. The converter has the same Boost characteristic as the traditional Boost converter. In addition, the voltage transfer ratio does not rely on the resonant branch parameters and switching frequency, which is determined only by the switching duty cycle.


## 3.1. Positive Input Voltage

For positive input voltage, from Figures2(a) and 2(b), when the switch S is turned on, the state differential equations are
(5)LdiLdt=vin,Codvcdt=-vcR.From Figure2(c), when the switch S is turned off, the corresponding state differential equations are
(6)(L+Lr)diLdt=vin-vc-vcr,Codvcdt=iL-vcR.The above analysis shows that the resonant capacitor voltage satisfies (2) when the switch S is turned off. From Figure 3, at the end of switching cycle, the resonant capacitor voltage is equal to Δvcr; meanwhile, the integration of the resonant capacitor voltage is zero.The matrix representation of the state variables isx=[iLvc]T; according to (5) and (6), the state space equation is
(7)x˙=Aix+Biu,i=1,2,
where
(8)A1=[000-1RCo],B1=[vinL0],A2=[0-1L+Lr1Co-1RCo],B2=[vin-vcrL+Lr0].According to GSSA approach, for positive input voltage, the GSSA equation of the Bipolar-Gain Pseudo-Boost converter can be obtained as(9)ddt[iLvc]=[0-(1-d)L+Lr(1-d)Co-1RCo][iLvc]+[vinL0],
where d is the transient state switching duty cycle.The equation(d/dt)[iLvc]=0 is founded at steady state because L≫Lr, so L+Lr≈L. From (9), there are
(10)vin=(1-D)vc,IL=vcR(1-D),
where D is the steady state switching duty cycle and IL is the steady state inductor current.


## 3.2. Negative Input Voltage

For negative input voltage, from Figure4(a), when the switch S is turned on, the state differential equations are
(11)LdiLdt=-vin,Codvcdt=iLr-vcR.From Figure4(b), when the switch S is turned on, the corresponding state differential equations are
(12)LdiLdt=-vin,Codvcdt=-vcR.From Figure4(c), when the switch S is turned off, the corresponding state differential equations are
(13)(L+Lr)diLdt=-vin-vcr,Codvcdt=-vcR.According to the above analysis, it can be seen that the resonant capacitor voltage satisfies (4) when the switch S is turned off. From Figure 5, at the end of switching cycle, the resonant capacitor voltage is equal to Δvcr-vc; thus, the integration of the resonant capacitor voltage is -vc in the time.The matrix representation of the state variables isx=[iLvc]T; according (11), (12), and (13), the state space equation is
(14)x˙=Aix+Biu,i=1,2,3,
where
(15)A1=[000-1RCo],B1=[-vinLiLrCo],A2=[000-1RCo],B2=[-vinL0],A3=[000-1RCo],B3=[-vin-vcrL+Lr0].Therefore, for negative input voltage, the GSSA equation of the Bipolar-Gain Pseudo-Boost converter can be obtained as(16)ddt[iLvc]=[000-1RCo][iLvc]+[-vinL+vcL(1-d)iL(1-d)Co].The equation(d/dt)[iLvc]=0 is founded at steady state because L≫Lr, so L+Lr≈L. From (16), there are
(17)vin=(1-D)vc,IL=vcR(1-D).According to (10) and (17), no matter if the input voltage is positive or negative, the voltage transfer ratios of Bipolar-Gain Pseudo-Boost converter keep the same. The converter has the same Boost characteristic as the traditional Boost converter. In addition, the voltage transfer ratio does not rely on the resonant branch parameters and switching frequency, which is determined only by the switching duty cycle.


## 4. The Implementation of Bridgeless Bipolar-Gain Pseudo-Boost Converter

The voltage transfer ratio of traditional DC-DC converter is unipolar, which means that it only makes positive and negative input voltage transfer to positive output voltage. However, the PFC converter belongs to AC-DC converter, which makes AC input voltage transfer to DC output voltage. Hence, the traditional DC-DC converter cannot be used as PFC converter. To realize PFC, the most direct way is combining a front-end bridge rectifier with a DC-DC converter. Assume that the voltage transfer ratio of DC-DC converter is bipolar; that is, no matter if the input voltage is positive or negative, the output voltage is always positive. This DC-DC converter can realize AC-DC transformation, which eliminates the bridge of traditional AC-DC converter and improves the efficiency of the converter.According to the steady state characteristic of Bipolar-Gain Pseudo-Boost converter, it is shown that the converter has bipolar-gain characteristic. So the Bipolar-Gain Pseudo-Boost converter can be used as PFC converter. From Figure6, the bridgeless PFC converter can be achieved by using bidirectional switch S1 combined with  S2 instead of controllable switching S of the Bipolar-Gain Pseudo-Boost converter. The converter has some advantages such as simple topology, high efficiency, and simple controlled circuit. Compared with the double bridge-leg bridgeless PFC converter researched in paper [3, 14–16], the converter has reduced the EMI due to common-grounded input and output. Compared with the bridgeless PFC converter proposed in paper [3, 13–17], the Bipolar-Gain Pseudo-Boost converter has improved the utilization ratio and reduced the costs.Figure 6
The topology of bridgeless Bipolar-Gain Pseudo-Boost PFC converter.From the preceding analysis, the achievement conditions of bridge Pseudo-Boost PFC converter are as follows.(1)
From Figures3 and 5, a two-way switch is needed because the switch S should suffer positive and negative voltage.(2)
The choice of inductorL: to guarantee that the converter operates in CCM, the inductor L must satisfy
(18)vinp,max⁡LDmax⁡Ts≤2Iinp.The input current effective value isIinp=2Po/ηvin,RMS, where vin,RMS is the input voltage effective value, vinp,max⁡ is the maximum input voltage peak value, Po is the output power, and η is the efficiency of the converter. In addition, Dmax⁡ is the maximum duty cycle and Ts is the switching cycle.(3)
The choice of resonant branch parameters: from (2), (4), and the operation figure, it can be obtained as
(19)Δvcr=IL2Cr(Ts-DTs)=vc2RCrTs.From (19), the choice of Δvcr has nothing to do with resonant inductor Lr. Δvcr is too large to increase the switch voltage stress, so larger resonant Cr and smaller switching period Ts should be chosen with the condition that resonant capacitor Cr is much smaller than output capacitor Co. However, the resonant capacitor Cr is too small to result in zero-crossing distortion, and it must satisfy vc>Δvcr>0; moreover,
(20)Dmin⁡Ts>Tr2,
where the minimum duty cycle is Dmin⁡=1-vinp,max⁡/vc, and the resonant period is Tr=2πLrCr. Thus, a suitable resonant inductor Lr should be chosen with respect to (19) when the resonant inductor Lr is much smaller than the Boost inductor L.


## 5. One-Cycle Control Bridgeless Bipolar-Gain Pseudo-Boost Converter

Figure7 is the principle scheme of bridgeless Pseudo-Boost PFC converter based on one-cycle control technology. The main circuit topology employs a bidirectional switch composed of S1 and S2. Dotted part of Figure 7 is the one-cycle control circuit, which consists of an integrator with reset function, a comparator, a RS trigger, and a clock signal generator.Figure 7
Block diagram of one-cycle control bridgeless Bipolar-Gain Pseudo-Boost PFC converter.The output voltagevc is sampled in each period and compared with a reference voltage Vref. The compared result is compensated by PI regulator and then the modulation signal vm is obtained. At each clock pulse coming, the two-way switch is turned on. Meanwhile, the modulation signal vm begins to be integrated by the reset integrator. The difference values v1 between vm and Rs|iL| are compared with the output signal v2 from reset integrator, when v2=v1, and the output level of the comparator is flipped and the switch is turned off, while the reset integrator resets to zero until the next clock pulse arrives.According to the principle of one-cycle control, it can be obtained that(21)vm-Rs|iL|=1Ts∫0TsDvmdt,
where vm=vcRs/Re and Re is the equivalent input resistor of the bridgeless Bipolar-Gain Pseudo-Boost PFC converter and Rs is the sampling resistor of inductor current.When (21) is applied at each switching cycle, the output voltage of the bridgeless Bipolar-Gain Pseudo-Boost PFC converter is steady; moreover, the input current that is iL will maintain sinusoidal, and thus the purpose of PFC is achieved.


## 6. Experiment Verification

In order to verify the accuracy of the theoretical analysis, a set of experiments are designed. According to (18)–(20), the parameters of experiment circuit are as follows: Po=100W, vin,RMS=50V, vc=100V, C=470μF, fline=50Hz, f=50kHz, L=2.5mH, Lr=7.8μH, and Cr=330nF.Figure8 shows the input voltage, input current, and output voltage waveforms of bridgeless Bipolar-Gain Pseudo-Boost PFC converter with Po=100W. It can be observed from Figure 8 that the output voltage of the converter vc is constant and the input current iin closely follows the input voltage vin to realize power factor correction.Figure 8
Waveforms of DC output voltagevc, AC input voltage vin, and AC input current iL.Figure9 shows the efficiency curve of bridgeless Pseudo-Boost PFC converter with vc=100V. It can be seen that the proposed converter has relatively high efficiency.Figure 9
Efficiency of the converter with 100 V DC output voltage.Figures10(a) and 10(b) show the switch voltage, diode voltage, and inductor current waveforms for the positive input voltage and negative voltage. It is seen that the experiment waveforms are consistent with the theoretical analysis waveforms and the diodes D1 and D2 can realize zero-current switching.The key operation waveforms of the converter (a) with positive input voltage and (b) with negative input voltage.
(a)
(b)The measured harmonic contents of the line current at 100 V AC input voltage are shown in Figure11 together with the limits of IEC61000-3-2 class D standard. It is shown that the input current harmonics of proposed converter can meet the IEC61000-3-2 standard. In addition, Figure 12 illustrates the measured PF value at full load of the proposed converter as the function of input voltage.Figure 11
Measured harmonic contents of the proposed converter.Figure 12
Measured PF value at full load of the proposed converter as the function of input voltage.


## 7. Conclusion

In this paper, we research the Bipolar-Gain Pseudo-Boost converter, and the topology and operation principles in CCM and DC steady-state character of this converter are analyzed. Based on this topology, a novel bridgeless Bipolar-Gain Pseudo-Boost PFC converter is proposed. In addition, the implement condition of the bridgeless PFC and control technology of the converter is studied. The experiments show that the proposed converter is capable of achieving the PFC better, and zero-current switching of the fast recovery diode is achieved. Moreover, the reverse-recovery loss of the diode is reduced and the efficiency of the converter is improved.



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