a single stage soft-switched ac/dc power factor corrected
TRANSCRIPT
A single stage soft-switchedAC/DC power factorcorrected converter withgalvanic isolation
Zhi Zhang1a), Xueliang Liu1, and Zhiping Wang21 School of Electronic Engineering, Dongguan University of Technology,
Dongguan 523808, China2 Guangdong Institute of Automation, Guangzhou 510007, China
Abstract: This paper describes a single-stage AC/DC Power Factor Cor-
rection (PFC) converter with galvanic isolation, and an active-clamp circuit
is used to achieve zero-voltage-switching (ZVS) for both main and auxiliary
switches. The ZVS operation principle of the system is illustrated in detail.
Simulation and experimental results based on a 85 kHz, 3000W prototype
circuit show that the proposed converter has low component count, galvanic
isolation, simple control, high power factor and high conversion efficiency in
a wide load range.
Keywords: power factor correction, zero-voltage-switching, isolation
Classification: Power devices and circuits
References
[1] D. S. Gautam, et al.: “An automotive onboard 3.3-kW battery charger forPHEVapplication,” IEEE Trans. Veh. Technol. 61 (2012) 3466 (DOI: 10.1109/TVT.2012.2210259).
[2] F. Musavi, et al.: “An LLC resonant DC–DC converter for wide output voltagerange battery charging applications,” IEEE Trans. Power Electron. 28 (2013)5437 (DOI: 10.1109/TPEL.2013.2241792).
[3] L. Huber, et al.: “Effect of valley switching and switching-frequency limitationon line-current distortions of DCM/CCM boundary boost PFC converters,”IEEE Trans. Power Electron. 24 (2009) 339 (DOI: 10.1109/TPEL.2008.2006053).
[4] F. Musavi, et al.: “A high-performance single-phase bridgeless interleaved pfcconverter for plug-in hybrid electric vehicle battery chargers,” IEEE Trans. Ind.Appl. 47 (2011) 1833 (DOI: 10.1109/TIA.2011.2156753).
[5] L. Huber, et al.: “Performance evaluation of bridgeless pfc boost rectifiers,”IEEE Trans. Power Electron. 23 (2008) 1381 (DOI: 10.1109/TPEL.2008.921107).
[6] J. W. Yang and H. L. Do: “High-efficiency ZVS AC-DC LED driver using aself-driven synchronous rectifier,” IEEE Trans. Circuits Syst. 61 (2014) 2505(DOI: 10.1109/TCSI.2014.2309837).
[7] S. W. Lee and H. L. Do: “Single-stage bridgeless AC-DC PFC converter usinga lossless passive snubber and valley switching,” IEEE Trans. Ind. Electron. 63(2016) 6055 (DOI: 10.1109/TIE.2016.2577622).
© IEICE 2017DOI: 10.1587/elex.14.20170144Received February 17, 2017Accepted March 24, 2017Publicized April 7, 2017Copyedited April 25, 2017
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[8] S. Cuk: Power electronics Technology Magazine (2010) 22.[9] D. Bortis, et al.: “Comprehensive analysis and comparative evaluation of
isolated true bridgeless Cuk single-phase PFC rectifier system,” IEEECOMPEL (2013) 1 (DOI: 10.1109/COMPEL.2013.6626438).
[10] M. Kim and S. Choi: “A fully soft-switched single switch isolated DC-DCconverter,” IEEE Trans. Power Electron. 30 (2015) 4883 (DOI: 10.1109/TPEL.2014.2363830).
1 Introduction
Isolated AC/DC converters are used in many applications, such as PC’s and
consumer electronics, uninterruptible power supplies, telecommunication power
supplies [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]. Sever isolated AC/DC converter topologies
with active PFC have been proposed [1, 2]. These topologies has two stages: the
first stage for rectification and power factor correction [3, 4, 5], and the other stage
for galvanic isolation, output voltage regulation and conversion [2]. However, these
topologies suffers from high switch losses with the drawback of many switch
component needed, and this often results in an overall efficiency of less than 90%.
Several single stage schemes have been reported in the literature [6, 7, 8, 9, 10].
They have the features such as lower component, lower cost, smaller size and high
power conversion efficiency than the two stage schemes. A boost-flyback topology
is the most commonly used single stage converter for galvanic isolation [6, 7], but it
is only suitable for small power applications.
The DC-DC converter proposed in [8, 9] can realize galvanic isolation and
could be used for high power applications, but it has the drawback of high voltage
spike across the power switch and limiting its use for high frequency applications.
An passive-clamp circuit is proposed to limit the switch voltage excursion and
realize the soft-switch for power switch and diode [10], but it suffers from excessive
power losses dissipated in RCD snubber.
This paper proposes a single-phase single-stage soft-switched AC/DC isolated
converter, and the basic active-clamp operation of the ZVS single-stage converter
is analyzed and explained. Finally, simulation and experimental results verify the
validity of the analysis. With a rated power of 3000W prototype, an outstanding
efficiency of 94.49% can be achieved.
2 Circuit converter
Fig. 1 shows the single-stage isolated PFC AC/DC topology. The AC/DC top-
ology includes a diode bridge and a isolated boost converter [8, 10]. The proposed
converter consists of switches Q1 and Q2, which are shown with their associated
antiparallel diode. Q1 and Q2 are main and auxiliary switches respectively. During
the turn-off of the main switch Q1, it will produce high voltage spikes at switch Q1,
so a clamp circuit is essential part of the topology [10].
Cr represents the parasitic capacitance of the two switches. L represents the
input inductor. The component Lr, Cp, Cs, together with the main power switch Q1
compose of the hybrid switch [8, 10]. C and Co are the clamp capacitor and output
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capacitor, respectively. The active clamp circuit is composed of the auxiliary switch
Q2 and the clamp capacitor C. With the active-clamp circuit, the main switch Q1
voltage spike is clamped, zero-voltage-switching (ZVS) for both primary (Q1) and
auxiliary (Q2) switches become possible, and high switching frequency, high
conversion efficiency can be reached.
3 Operating principle
Fig. 2 shows the key waveforms for the active-clamp isolated boost converter and
Fig. 3 illustrates the topological operation stages. The following assumptions are
made for the system analysis:
(1) all switch components are ideal;
(2) the clamp capacitance C is larger than the parasitic capacitance Cr;
(3) the resonant Lr is much less than the transformer magnetizing inductance Lm;
(4) energy stored in the resonant Lr is greater than the parasitic capacitance to
completely discharge Cr and turn on Q1’s antiparallel diode;
(5) n = ns/np is the transformer turns ratio between the secondary winding turns
and the primary winding turns.
The five distinct operating modes can be described below.
Fig. 2. Key waveforms of the proposed converter
Fig. 1. Proposed single-stage isolated active-clamp PFC converter
© IEICE 2017DOI: 10.1587/elex.14.20170144Received February 17, 2017Accepted March 24, 2017Publicized April 7, 2017Copyedited April 25, 2017
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Mode 1
At t0, the main switch Q1 is turned on, and the auxiliary switch Q2 is turned off.
The input inductor L is being linearly charged, the parasitic capacitor voltage
ucr ¼ udsQ1 ¼ 0, and the resonant inductor current iLr discharge the capacitor Cp.
The diode D2 and D3 are turned on. The capacitor current ics increase and capacitor
voltage ucs decrease.
Mode 2
At t1, main switch Q1 is turned off, and the auxiliary switch Q2 is off, Cr is
charged by the input inductor current iL and resonant current iLr from 0 to uc(udsQ1 ¼ ucr ¼ uc) until time t ¼ t2, the charge time is very short, and the input
inductor iL and resonant current iLr are almost constant.
Fig. 3. Operation stages of proposed isolated converter
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Mode 3
At t2, the antiparallel diode of Q2 starts to conduct, when the Cr is charged to
the point of ucr ¼ uc, since the clamp capacitor C is larger than Cr, the time interval
is very short, the uc almost keeps constant. The auxiliary switch Q2 should be
turned on to achieve ZVS. The input inductor current iL decrease linearly.
The resonant inductor iLr will decrease form a positive to a negative value, and
the capacitor current ics becomes negative, the diode D1, D4 are turned on. The
voltage ucs increase. This stage ends when auxiliary switch Q2 is turned off.
Mode 4
The auxiliary switch Q2 is turned off at t3, and the clamp capacitor C is removed
from the circuit, and the main switch current is negative.
Assuming the energy stored in resonant inductor Lr is greater than the energy
stored in Cr. The ucr voltage will be discharged from uc to 0, and the antiparallel
diode of Q1 starts to conduct. Hence, the resonant Lr must stratify:
Lr � Crðucðt3ÞÞ2iLr ðt3Þ2
: ð1Þ
At time t4, the main switch is turned on for ZVS because the antiparallel diode
of main switch turns on.
Mode 5
At time t5, the switch current is increases from a negative to a positive value.
The input inductor current begins to linearly charge again, and another switch cycle
starts again.
4 Experimental result
A 3000W simulation and experimental prototype of the proposed AC/DC con-
verter has been built and tested to verify the effectiveness of the proposed converter.
The PSIM software is used to illustrate to the operation waveform of the proposed
converter, and the control circuit is implemented with the average current-mode
controller UC3854 from Texas Instruments. The parameters of the experimental
prototype of the AC/DC PFC converter are summarized in Table I.
Fig. 4 shows the simulation and experimental waveforms of input voltage,
input current and output voltage at the rated output power of 3000W. The input
current is close to a sinusoidal waveform, and it is in phase with the input voltage.
A high power factor of 0.993 could be achieved, and the measured THD of the
Table I. System parameters of the proposed converter
Input AC voltage 220V/50HzTurn ratio for primary side winding and
8:9secondary side winding
Output DC voltage 300V Sic switch C3M0065090JPomax 3000W Resonant inductor Lr 5 uH
Switching85K Input inductor L 220 uH
frequency (KHz)Output filter
2200 uF capacitance Cp 6.6 uFcapacitance C0
Clamp capacitance C 100 uF capacitance Cs 2.2 uF
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input current is 3.9%. The output voltage keeps 300V and it contains 100Hz ripple
voltage.
The simulation and experimental waveform of primary capacitor ucp, secondary
capacitor voltage ucs and input current is are given in Fig. 5 respectively.
Fig. 6 shows the gate drive signal ugs and the drain to source voltage uds for
main switch Q1 and auxiliary switch Q2, it indicates that the zero voltage switching
(ZVS) could be achieved for all SiC MOSFETs.
Fig. 7 shows the efficiency of the proposed topology for 220V/50Hz AC input
voltage, a high efficiency is reached over a wide load range, and the maximum
conversion efficiency is achieved by the 3000W prototype is 94.49%.
(a) (b)
Fig. 4. Simulation and experimental waveform of input voltage, inputcurrent and output voltage
(a) (b)
Fig. 5. Simulation and experimental waveform of input current,primary capacitor Cp and secondary capacitor Cs
(a) (b)
Fig. 6. Experimental waveform of gate voltage and drain-sourcevoltage for switch devices Q1 and Q2
© IEICE 2017DOI: 10.1587/elex.14.20170144Received February 17, 2017Accepted March 24, 2017Publicized April 7, 2017Copyedited April 25, 2017
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5 Conclusion
A single-stage isolated AC/DC PFC topology with active-clamped zero-voltage
switch is described in this paper. The ZVS operation mode is analyzed in detail, and
the proposed converter can be easily implemented with available control IC’S. The
theoretical analysis is verified by a 3000W simulation and experimental prototype.
A nearly unity power factor, lower than 4% THD current, and greater than 94%
conversion efficiency could be achieved.
Acknowledgments
This work was supported by Guangdong Science and Technology Foundation of
China (grant number 2015A010106018), Distinguished Young Teacher Project of
Education Department of Guangdong Province (YQ2015156, 2014KQNCX217).
Fig. 7. Measured efficiency curve
© IEICE 2017DOI: 10.1587/elex.14.20170144Received February 17, 2017Accepted March 24, 2017Publicized April 7, 2017Copyedited April 25, 2017
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