wiwo

280 IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 25, NO. 2, FEBRUARY 2010

A Wide-Input–Wide-Output (WIWO)DC–DC Converter

Hao Cheng, Keyue Ma Smedley, Fellow, IEEE, and Alexander Abramovitz, Member, IEEE

Abstract—This paper presents a new wide-input–wide-outputdc–dc converter, which is an integration of buck and boost convert-ers via a tapped inductor. Coherent transition between step-downand step-up modes is achieved by a proper control scheme. Thispaper presents theoretical concepts and experimental results.

Index Terms—Boost, buck, coupled inductors, energy recoveringsnubber, wide step-down, wide step-up, wide-input–wide-output(WIWO) dc–dc converter.

I. INTRODUCTION

THE BUCK, boost, buck–boost, and Cuk converters are thefour basic dc–dc nonisolating converters that have found

wide applications in industry. The buck converter can step downthe dc voltage, whereas the boost converter is capable to per-form a step-up function. In applications where both step-upand step-down conversion ratios are required, the buck–boostand Cuk converters can be used. Simplicity and robustness areamong the advantages of the buck–boost converter. However,the pulsating input and output currents cause high conductionlosses, and thus, impair the efficiency of buck–boost. Further-more, the buck–boost converter uses the inductor to store theenergy from the input source, and then, release the stored energyto the output. For this reason, the magnetic components of buck–boost are subjected to a significant stress. These disadvantageslimit the applications of the buck–boost converter mainly to lowpower level. The isolated version of buck–boost, referred to asthe flyback converter, can achieve greater step-up or step-downconversion ratio utilizing a transformer, possibly, with multipleoutputs. As compared with the buck–boost converter, the Cukconverter has higher efficiency and smaller ripples in input andoutput currents. A significant improvement of the Cuk converterperformance can be achieved by applying the zero ripple con-cept. The Cuk converter can be found in many high-performancepower applications.

In theory buck and boost converters can generate almost anyvoltage, in practice, the output voltage range is limited by com-ponent stresses that increase at the extreme duty cycle. Conse-

Manuscript received November 7, 2008; revised January 20, 2009. Currentversion published February 12, 2010. Recommended for publication byAssociate Editor J. Antenor.

H. Cheng is with the Department of Electrical Engineering and ComputerScience (EECS), University of California, Irvine (UCI), Irvine, CA 92617 USA(e-mail: [email protected]).

K. M. Smedley is with the Department of Electrical and Computer Engi-neering (ECE), University of California, Irvine (UCI), Irvine, CA 92697 USA(e-mail: [email protected]).

A. Abramovitz is with the Department of Electrical Engineering (EE), SamiShamoon College of Engineering (SCE), Beer-Sheva 84100, Israel (e-mail:[email protected]).

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TPEL.2009.2025375

quently, buck converter losses mount at low duty cycle, whereasboost converter efficiency deteriorates when the duty cycle tendsto unity. Accordingly, voltage conversion range of the buck con-verter below 0.1–0.15 becomes impractical whereas that of theboost converters’ is limited to below 8–10. Additional prob-lems associated with narrow duty cycle are caused by MOS-FET drivers rise and fall times as well as pulsewidth-modulated(PWM) controllers that have maximum pulsewidth limitations.These problems become even more severe at higher voltagesand higher frequencies.

Introducing a transformer helps attaining large step-up orstep-down voltage conversion ratio. Transformers’ turn ratioshould be chosen as to provide the desired voltage gain whilekeeping the duty cycle within a reasonable range for higherefficiency. The transformer, however, brings in a whole newset of problems associated with the magnetizing and leakageinductances, which cause voltage spikes and ringing, increasedcore and cooper losses as well as increased volume and cost.

In a quest for converters with wide conversion range, quite afew authors proposed using converters with nonlinear charac-teristics. Single-transistor converter topologies, with quadraticconversion ratios, were proposed in [1] and demonstratedlarge step-down conversion ratio. This method has successfullyachieved wide conversion range in the step done direction. Adifferent approach to obtain wide conversion range utilizingcoupled inductors was proposed in [2]. With only minor modi-fication of the tapped-inductor buck, [2] shows low componentcount and solves the gate-drive problem by exchanging the po-sition of the second winding and the top switch. The problemof a high turn-OFF voltage spike on the top switch was solvedby applying a lossless clamp circuit. Due to the coupled induc-tor action, the converter demonstrated high step-down dc–dcconversion ratio, whereas the converter’s efficiency was im-proved by the extended duty cycle. A tapped-inductor buckwith soft switching was introduced in [3]. Derivations of thetapped-inductor buck were also suggested in [4] and [5]. An-other modification of the tapped-buck converter was realizedin [6] for power factor correction (PFC) application. With theaddition of a line-frequency-commutated switch and a diode,both flyback and buck characteristics were achieved and largestep-down was demonstrated.

Some applications, especially battery-operated equipment,require high voltage boosting. To attain very large voltage step-up, cascaded boost converters that implement the output volt-age increasing in geometric progression were introduced in [7].These converters effectively enhance the voltage transfer ra-tio; however, their circuits are quite complex. In comparison,tapped-inductor boost converters proposed in [8] and [9] at-tain a comparable voltage step-up preserving relative circuit

0885-8993/$26.00 © 2010 IEEE

Authorized licensed use limited to: RAJESH K. Downloaded on March 19,2010 at 01:54:59 EDT from IEEE Xplore. Restrictions apply.

CHENG et al.: WIDE-INPUT–WIDE-OUTPUT (WIWO) DC–DC CONVERTER 281

Fig. 1. Buck-derived converters with tapped inductors.

simplicity. In [10], the boost converter output terminal and fly-back converter output terminal are connected in series to in-crease the output voltage gain with the coupled inductor. Theboost converter also functions as an active clamp circuit to re-cycle the snubber energy.

This paper proposes a new wide-input–wide-output (WIWO)dc–dc converter. The new converter is an integration of buckand boost converters via a tapped inductor. By applying propercontrol to the two active switches, the converter exhibits bothbuck and boost features [11], [12]. Section II discusses the basicswitching converters with tapped inductors, and offers motiva-tion and guidelines to the synthesis of the new switching con-verter. Section III presents the topology of the proposed WIWOdc–dc converter and the required control scheme. The operatingprinciple is described in detail providing the steady-state (dc)and dynamic (ac) models as well. The theoretical derivationswere verified experimentally and reported in Section IV. Modi-fications and additional applications are discussed in Section V.Conclusions are given in Section VI.

II. MOTIVATION IN THE SEARCH FOR NEW SWITCHING

CONVERTER TOPOLOGY

The basic buck and boost converters can be transformed intoa number of new topologies by bringing in the tapped induc-tor. The proposed tapped-inductor buck-derived converters areshown in Fig. 1, with their corresponding voltage conversionratios plotted in Fig. 2. The proposed tapped-inductor boost-derived topologies and their corresponding voltage conversionratios are given in Figs. 3 and 4. Here, D is the duty ratio ofswitch S, M is the voltage conversion ratio, and n is the turnratio of the tapped inductors, which is defined as n = n2 : n1 .As the turn ratio n tends to infinity, the conversion ratio of thebuck-derived converters approach the characteristic of a basicbuck topology. On the other hand, as the turn ratio n goes tozero, the conversion ratio of the boost-derived converters ap-proach the characteristic of a basic boost topology. Inspectionof the conversion ratio plots, as given in Fig. 1(a), reveals that theproposed buck-derived converter achieves wider voltage step-down than a basic buck converter. Also, by examining Fig. 3(a),it becomes evident that the suggested boost-derived converterattains a wider voltage step-up than a basic boost converter.

The converter topologies shown in Figs. 1(a) and 3(a) arestrikingly similar. The idea proposed here is that these twotopologies may be combined to form a new two-switch topol-ogy, with an extended conversion range. Same conclusion canbe reached comparing the converters given in Figs. 1(c) and 3(c).The proposed WIWO range converter topology is described inthe next section.

III. WIWO DC–DC CONVERTER

A. Proposed WIWO DC–DC Converter Topology

The proposed WIWO dc–dc converter is illustrated in Fig. 5.The converter is comprised of two active switches S1 and S2,tapped inductors L1 and L2 with turns ratio n = n2 : n1 , diodeD, and capacitive output filter C.

Specifically, note that the tapped inductor in Figs. 1 and 3 isreconfigured into a pair of coupled inductors in Fig. 5. Beingequivalent electrically, this reconfiguration is beneficial from apractical point of view. In Fig. 5, S1 and S2 are connected toa common junction or midpoint. The midpoint is periodicallyswitched by S1 to ground, which allows recharging the bootstrappower supply and reliable operation of the flying driver of thetop switch S2. Consequently, a standard half-bridge driver chipcan be used with the low-side driver operating the bottom switchS1 and the bootstrap high-side driver activating the top switchS2.

WIWO can operate either in the step-down or the buck modeor in the step-up or the boost mode. To operate the WIWOin the buck mode, the switch S1 is assigned a high-frequencyswitching signal with a predetermined duty cycle D, whereasS2 is switched complementarily to S1. The diode D is kept ON

by the inductor L2 current, which is assumed to be continuous.To operate WIWO in the boost mode, the controller keeps

S2 switch continuously ON and issues the required duty cyclesignal for the S1 switch. Thus, the diode D is forced to switchon and off complementarily to S1.

In both modes, the capacitor C filters the pulsating currentand provides a smoothed output voltage for the load R.

B. Control Scheme

For the proper operation of WIWO, a modified PWM controlcircuitry is required. The implementation is not unique. Onepossible realization of the modulator is shown in Fig. 6. Here, awindow comparator is employed to derive the required switch-ing signals for S1 and S2 by comparing the sawtooth ramp withamplitude of Vm to the two control voltages VC and V ′

C . Thecontrol voltage VC for the upper comparator is delivered byan external source, whereas the lower comparator input signalV ′

C is derived by the PWM circuitry, downshifting the controlvoltage VC by Vm : V ′

C = VC − Vm . The relationship betweenthe control voltage VC and the sawtooth ramp amplitude Vm

can be expressed by means of a variable m as VC = mVm .WIWO operates in the buck mode when 0 < VC < Vm , i.e.,when 0 ≤ m < 1. Here, the upper comparator generates therequired duty cycle for the S2 switch, whereas the lower com-parator is in “1” state and commands the NAND gate to provide



Fig. 2. Voltage conversion ratio of buck-derived converters with tapped inductors. (a) 0 < n < ∞. (b) 0 < n < ∞. (c) n > 1. (d) n > 1.

Fig. 3. Boost-derived converters with tapped inductors.

the complimentary duty cycle for the S1 switch. Therefore,WIWO operates similarly to a synchronous buck converter. Onthe other hand, for Vm < VC < 2Vm , or 1 ≤ m < 2, the up-per comparator is in “1” state and keeps S2 continuously ON,

whereas the lower comparator and the NAND gate provide therequired duty cycle for the S1 switch. Thus, the converter entersthe boost mode.

C. Operating Principle of the WIWO Converter

In the following, the steady-state operation of the proposedWIWO converter is described. The analysis is performed as-suming that the circuit is comprised of ideal components. Thecoupling coefficient of the tapped inductor is assumed to beunity. Under continuous inductor current (CCM) condition, theproposed WIWO converter exhibits four topological states, asshown in Fig. 7. Here, the large output filter capacitor is re-placed by an ideal voltage source. The waveforms and timing ofWIWO for both buck and boost modes are illustrated in Fig. 8.

1) Buck Mode: State 1 (t0 ≤ t < t1) is the buck-modecharging state [see Figs. 7(a) and 8(a)]. Here, the switch S2is turned on and S1 is turned off. The diode D conducts and thecoupled inductors L1 and L2 are charged. The energy is alsotransferred from dc source to load.



Fig. 4. Voltage conversion ratio of boost-derived converters with tapped inductors. (a) 0 < n < ∞. (b) 0 < n < ∞. (c) 0 < n < 1. (d) 0 < n < 1.

Fig. 5. WIWO dc–dc converter topology.

State 2 (t1 ≤ t ≤ t2) is the buck-mode discharging state [seeFigs. 7(b) and 8(a)]. Here, the switch S2 is turned off also cuttingoff the current in the L1 winding, whereas S1 is turned on andthe diode D conducts L2 current to the load.

2) Boost Mode: State 3 (t′0 ≤ t < t′1) is the boost-modecharging state [see Figs. 7(c) and 8(b)]. Here, the switches S1

Fig. 6. Proposed WIWO dc–dc converter and PWM control circuitry.

and S2 are turned on charging the L1 inductor. The diode Dis cut off by the negative voltage induced in L2 winding. Theoutput voltage is supported by the capacitor C.



Fig. 7. Four topological states of the WIWO converter. (a) Buck-mode charging state. (b) Buck-mode discharging state. (c) Boost-mode charging state.(d) Boost-mode discharging state.

Fig. 8. Waveforms of the WIWO dc–dc converter. (a) Buck mode. (b) Boostmode.

State 4 (t′1 ≤ t ≤ t′2) is the boost-mode discharging state [seeFigs. 7(d) and 8(b)]. Here, the switch S2 is still ON whereas S1 isturned off. Both windings L1 and L2 conduct through the diodeD and discharge the stored energy to the output.

D. Steady-State Analysis

The steady-state models of the proposed WIWO converterare shown in Fig. 7. These models preserve the tapped-inductorsymbol. More suitable for analysis purposes, however, are themodels of Fig. 9. Here, the role of the magnetizing inductanceLm is clearly shown. The detailed analysis was carried out

in [11] using state-space averaging technique. WIWO voltageconversion ratio, output voltage ripple, voltage stresses, etc.,were obtained. The characteristics of WIWO are summarizedin Table I for a general case of n and separately for the specialcase of n = 1.

WIWO voltage transfer characteristics M (n, m) are plotted inFig. 10. Clearly, for n = 1, the voltage transfer ratio is smoothat the vicinity of the buck to boost switchover point m = 1,whereas for other values of n, the curves exhibit a slope change.This statement can be verified analytically by calculating thederivatives of M (m) at m = 1. Using the expressions for voltageconversion ratio given in Table I, the result is ((n + 1)/n) for thebuck mode and (n + 1) for the boost mode. Obviously, the slopeof WIWO dc–dc characteristic becomes continuous for n = 1.

Table I also presents the line-to-output and control-to-outputtransfer functions. The small-signal transfer functions of theWIWO converter were derived by linearizing the state-spaceequations around the operating point [11]. The line-to-outputand control-to-output transfer functions reveal strong depen-dence on the operating point and a right-half-plane (RHP)zero. This is also the case in other tapped-inductor topolo-gies [13], [14]. These characteristics make the WIWO com-pensation network design somewhat difficult.

IV. EXPERIMENTAL RESULTS

A 100-W prototype WIWO converter was designed for inputvoltage range of 12–48 Vdc and a constant output voltage of28 Vdc . The turn ratio of the tapped inductor was set to n =1 with a total inductance of 400 µH. The switching frequencyof 200 kHz was chosen. The tapped inductors were wound onC058548A2 toroidal powder core, chosen for its low leakage,with 50 turns of AWG20 wire for both windings. The designyielded 400 µH inductance with only 560 nH leakage induc-tance. Two FDD2572 MOSFETs were paralleled to comprisethe top switch and two IRFR3518 were used for the low switchproviding low Rds−ON and low gate capacitance. Schottky diode



TABLE ICHARACTERISTICS OF WIWO DC–DC CONVERTER AND CHARACTERISTICS FOR n = 1



Fig. 9. Switched circuit models. (a) State 1. (b) State 2. (c) State 3. (d) State 4.

Fig. 10. Voltage transfer characteristics M (n, m) of the WIWO dc–dcconverter.

20CTQ150 was selected due to superior reverse recovery char-acteristics.

Experimental waveforms of WIWO converting 48 V inputto 28 V output (buck mode) are shown in Fig. 11. In the buckmode, S2 is the leading switch, gated by the duty cycle commandshown as the bottom trace in Fig. 11, whereas the bottom switchS1 is switched complementarily, similarly to a synchronousconverter. Switch voltages (see Fig. 6 for definition) are shownas top two waveforms in Fig. 11. The middle traces show thewinding currents. These were measured by ac probe, so onlythe ripple components could be observed. As could be seen, asthe S2 switch conducts, both windings carry the same current.At the S2 is turned off, the input current ceases whereas theoutput current is doubled in amplitude, consistent with WIWOmodels in Fig. 9(a) and (b). The ramp portion of the currentis hardly noticeable due to the relatively high frequency andsufficiently large inductance value. The leakage inductance ofL1 developed a turn-OFF voltage spike across S1 that is smoothedby the snubber circuitry. The snubber is used to clamp the voltagespike, as described later.

Fig. 11. Experimental waveforms of the WIWO converter in the buck mode(see Fig. 6 for designation of variables). Top trace: drain voltage V1 of S1switch (50 V/division, 2 µs/division); second top trace: drain voltage V2of S2 switch (50 V/division, 2 µs/division); middle trace: input current Ii

(0.2 A/division, 2 µs/division); second bottom trace: output current Io (0.2A/division, 2 µs/division); bottom trace: S2 switch gating voltage (20 V/ divi-sion, 2 µs/division).

The experimental waveforms of WIWO in the boost modewith 12 V input and 28 V output, under full-load condition,are shown in Fig. 12. To supply the power requirements of theload at lower input voltage range, WIWO calls for greater inputcurrent, and therefore, turn-OFF voltage spike on S1 is observed.

In the boost mode, the S1 switch is the leading switch thatis issued the duty cycle command, shown as the bottom tracein Fig. 12. Since in the buck mode the S2 switch is constantlyON, the drain voltage of S2 and the drain voltage of S1 arealmost identical. The winding currents were measured by ahigh-frequency ac probe, and therefore, only ac current compo-nents are shown as two middle traces in Fig. 12. As S1 switchconducts, the input winding carries the input current and ischarging, whereas the output current is cut off. As the S1 switch



Fig. 12. Experimental waveforms of WIWO in the boost mode (see Fig. 6 fordesignation of variables). Top trace: drain voltage of S1 switch (20 V/division,2 µs/division); second top trace: drain voltage of S2 switch (20 V/division,2 µs/division); middle trace: input current Ii (0.5 A/division, 2 µs/division);second bottom trace: output current Io (0.5 A/division, 2 µs/division); bottomtrace: S1 switch gating voltage (20 V/division, 2 µs/division).

Fig. 13. Comparison of K with Kcrit for n = 1.

is cut off, both windings carry the same current and are dis-charging into the output capacitor and feeding the load. For thisreason, the currents ripple components appear in antiphase, aspredicted by WIWO models in Fig. 9(c) and (d). Also couldbe seen is the snubber circuit resonant discharge as the snubberrecycles the stored energy.

With decreased load, the converter enters the discontinuousconduction mode (DCM). To measure the tendency of the con-verter to operate in DCM, the parameter K = (2Lm /RTs) isdefined as suggested in [15]. The critical value of K for n = 1is compared with K = 2, 0.2, 0.02 in Fig. 13. The experimen-tal voltage conversion ratio M as function of m for differentvalues of K plotted on top of the theoretical curve is given inFig. 14(a)–(c). Due to the parasitic resistances in the circuit, theexperimental voltage conversion ratio M is slightly lower thantheoretical prediction. For very same reason, the experimentalM cannot become infinite and drops as m approaches 2. Anarrow buck- to boost-mode transition can be observed on theWIWO characteristic in the vicinity of m = 1. The conversion

Fig. 14. Comparison of the experimental and theoretical voltage conversionratio under different loading conditions. (a) K = 2. (b) K = 0.2. (c) K = 0.02.

ratio in DCM is higher than that in CCM, as shown in Fig. 14(b)and (c).

The efficiency of the experimental WIWO dc–dc converterfor different dc input voltages versus the load current is plottedin Fig. 15. The output voltage was kept at the nominal valueof 28 Vdc . No attempt was made to optimize the preliminarydesign, still the converter demonstrated high efficiency.

V. APPLICATIONS

A continuously conducting diode D has a considerableforward voltage drop. This is not desirable for low-output-voltage applications. The voltage drop can be reduced using



Fig. 15. Experimental WIWO converter efficiency.

Fig. 16. WIWO dc–dc converter with the synchronous rectifier.

Fig. 17. Bidirectional WIWO dc–dc converter.

a synchronous rectifier with low Rds-ON instead of the diode,as shown in Fig. 16.

Interchanging the position of the inductor L2 and switch S3,as shown in Fig. 17, the WIWO topology becomes symmet-rical. This also allows driving the top switch S3 with anotherflying driver. An additional advantage of the circuit in Fig. 17is the ability to sustain a bidirectional power flow. The direc-tion of the power flow can be controlled applying a single-poledouble-throw switch, which may be controlled manually or au-tomatically, as illustrated in Fig. 17. This WIWO can be used ina battery charging and discharging application. With the switchin position 1, the power flows from the left port to the right

Fig. 18. WIWO PFC ac–dc converter.

Fig. 19. Energy recovering snubber for WIWO power stage.

port, whereas with the switch in position 2, the power flows ina reverse direction from the right port to the left port.

The WIWO dc–dc converter can also be used for PFC appli-cation (see Fig. 18). Here, a sinusoidal line voltage is fed intothe rectifier input. The WIWO dc–dc converter can accept therectified voltage and directly produce the required low dc out-put. With the line voltage greater than the output, the converterworks in the buck mode. As the line drops below the outputvoltage, WIWO enters the boost mode.

VI. ENERGY RECOVERY SNUBBER

Since the WIWO operates a coupled inductor, the energystored in the leakage inductances becomes a problem to dealwith. Besides increased switching losses, discharge of the leak-age inductance energy causes oscillations and increased voltagespikes across the switches. The resulting voltage stress becomesintolerable at higher voltages and higher power. If not snubbed,overvoltage breakdown of the MOSFET devices may occur.

The proposed lossless snubber is comprised of a snubbercapacitor CS and a pair of fast diodes DS1 and DS2 . The snubberis fitted to WIWO, as shown in Fig. 19. The snubber is effectiveboth in buck mode and in boost mode.

Detailed description of the snubber operation is out of scopeof this paper; in brief, however, the operation is as follows. WithWIWO in the buck mode, at the instant when the S2 switch isturned off, the snubber diode DS1 conducts L1 leakage currentand allows the stored energy to be discharged into the snubbercapacitance CS and to the output of the circuit. This takes one-half resonant cycle dictated by the leakage inductance and thesnubber capacitance. CS will remain charged until the S2 switchis turned ON again at the onset of the subsequent switching cycle.With S2 turned ON, the energy stored in the snubber capacitoris discharged into L2 winding via DS2 and recycled.



In the boost mode, the snubber operation is similar. However,here, S1 interrupts the current and is subject to the voltage spikewhile S2 switch is constantly ON with zero voltage VDS 2 across.

VII. CONCLUSION

This paper has presented a new WIWO dc–dc converter,which is an integration of buck and boost converters with cou-pled inductors. The paper described WIWO principles of opera-tion and offers a comprehensive summary of WIWO analyticalcharacteristics. Simulation and experimental results were alsoreported. A modified PWM modulator scheme required to makethe converter work coherently was also suggested. A prototypeWIWO dc–dc converter was built and tested. The converterdemonstrated in practice the WIWO dc–dc conversion ratio.

The new converter topology has several advantages. TheWIWO retains the features of both the buck and the boost con-verters; however, it achieves wider step-up and wider step-downdc–dc conversion range. The WIWO converter can operate withan input source with broadly varying voltage or, alternatively,feed loads with variable operating voltage such as dc motors.The converter has a simple structure and moderate componentcount. The advantageous buck feature allows turning off theoutput voltage on demand. WIWO is also inherently capable oflimiting the inrush current and can protect the output in the caseof a short circuit. Due to the nonlinear characteristics, WIWOcan avoid operating at extreme duty cycle. As a result, WIWOefficiency remains high even throughout large input voltageswing. The transition between the operating modes is inher-ently smooth, and causes no transient disturbance in the averagecurrent. Among the disadvantages of WIWO is the coupled in-ductor whose leakage causes oscillation and high voltage spikeacross the switches. Clamp circuits are needed to clamp volt-age spikes upon switches, so as to recycle the leakage energy.Another disadvantage of WIWOs is that small-signal transferfunctions include an RHP zero, and therefore, WIWO is some-what difficult to stabilize using a single voltage loop. To resolvethe dynamic problem, current loop should be employed, whichis a good practice in any case. An additional disadvantage is thatWIWO does not provide isolation. This, however, may not bemuch of a problem in systems with multiple stages.

Modifications of the WIWO to synchronous WIWO dc–dcconverter, bidirectional WIWO dc–dc converter, and WIWOdc–dc converter for PFC are possible. Numerous advantagesindicate WIWO as a viable candidate for many industrialapplications.

REFERENCES

[1] D. Maksimovic and S. Cuk, “Switching converter with wide dc conversionrange,” IEEE Trans. Power Electron., vol. 6, no. 1, pp. 151–157, Jan. 1991.

[2] K. Yao, M. Ye, M. Xu, and F. C. Lee, “Tapped-inductor buck converter forhigh-step-down dc–dc conversion,” IEEE Trans. Power Electron., vol. 20,no. 4, pp. 775–780, Jul. 2005.

[3] J.-H. Park and B.-H. Cho, “Nonisolation soft-switching buck converterwith tapped-inductor for wide-input extreme step-down applications,”IEEE Trans. Circuits Syst. I, Reg. Papers, vol. 54, no. 8, pp. 1809–1818,Aug. 2007.

[4] K. Yao, Y. Ren, J. Wei, M. Xu, and F. Lee, “A family of buck type dc–dcconverters with autotransformers,” in Proc. Appl. Power Electron. Conf.Expo. (APEC 2003), pp. 114–120.

[5] K. Nishijima, K. Abe, D. Ishida, T. Nakano, T. Nabeshima, T. Sato, andK. Harada, “A novel tapped-inductor buck converter for divided powerdistribution system,” in Proc. IEEE PESC Conf. (PESC 2006), Jun., 18–22, pp. 1–6.

[6] G. Spiazzi and S. Buso, “Power factor preregulator based on modifiedtapped-inductor buck converter,” in Proc. IEEE PESC Conf., 1998, vol. 2,pp. 873–879.

[7] F. L. Luo and H. Ye, “Positive output cascade boost converters,” Proc.Inst. Electr. Eng. Electr. Power Appl., vol. 151, no. 5, pp. 590–606, Sep.2004.

[8] Q. Zhao and F. C. Lee, “High efficiency, high step-up dc–dc converters,”IEEE Trans. Power Electron., vol. 18, no. 1, pp. 65–73, Jan. 2003.

[9] N. Vazquez, L. Estrada, C. Hernandez, and E. Rodriguez, “The tapped-inductor boost converter,” in Proc. IEEE Int. Symp. Ind. Electron., Jun.,4–7, 2007, pp. 538–543.

[10] K. C. Tseng and T. J. Liang, “Novel high efficiency step-up converter,”Proc. Inst. Electr. Eng. Electr. Power Appl., vol. 151, no. 2, pp. 182–190,Mar. 2004.

[11] H. Cheng, “Wide input wide output (WIWO) dc–dc converter,” Master’sthesis, Univ. California, Irvine, Dec. 2007.

[12] H. Cheng and K. Smedley, “Wide input wide output (WIWO) dc–dc con-verter,” in Proc. IEEE Appl. Power Electron. Conf. Expo., 2008, pp. 1562–1568.

[13] R. D. Middleblook, “A continuous model for the tapped-inductor boostconverter,” in IEEE PESC 1976 Rec., Jun., pp. 10–19.

[14] D. Edry, M. Hadar, O. Mor, and S. Ben-Yaakov, “A SPICE compatiblemodel of tapped-inductor PWM converters,” in Proc. IEEE APEC 1994,pp. 1021–1027.

[15] R. Erickson and D. Maksimovic, Fundamentals of Power Electronics.Norwell, MA: Kluwer, 2001.

Hao Cheng, photograph and biography not available at the time of publication.

Keyue Ma Smedley (S’87–M’90–SM’97–F’08) re-ceived the B.S. and M.S. degrees in electrical engi-neering from Zhejiang University, Hangzhou, China,in 1982 and 1985, respectively, and the M.S. andPh.D. degrees in electrical engineering from theCalifornia Institute of Technology, Pasadena, in 1987and 1991, respectively.

She was employed at the Superconducting SuperCollide from 1990 to 1992, where she was respon-sible for the design and specification of ac-dc con-verters for all accelerator rings. She is currently a

Professor in the Department of Electrical Engineering and Computer Science,University of California at the Irvine (UCI). She is also the Director of the UCIPower Electronics Laboratory. Her research activities include high efficiencydc-dc converters, high-fidelity class-D power amplifiers, active and passive softswitching techniques, single-phase and three-phase PFC rectifiers, active powerfilters, grid-connected inverters for alternative energy sources, VAR on demandfor modern grid, motor drive, fault current limiters for utility, solar and windpower conversion, etc. She has authored or coauthored more than 100 technicalarticles and holds ten US/international patens.

Dr. Smedley is the recipient of UCI Innovation Award 2005.

Alexander Abramovitz (M’06) was born inKishinev, USSR, and repatriated to Israel in 1973.He received the B.Sc., M.S., and Ph.D. degrees all inelectrical engineering from Ben-Gurion Universityin the Negev, Beer-Sheva, Israel, in 1987, 1993, and1997, respectively, and a postdoc from the Universityof California, Irvine, in 2004.

He is currently an Assisting Professor in the De-partment of Electrical and Electronics Engineering,Sami Shamoon College of Engineering, Beer-Shevaand a Visiting Researcher in the Department of Elec-

trical Engineering and Computer Science, University of California. His currentresearch interests include switch mode and resonant power conversion, highquality rectification, electronic instrumentation, and analog circuits.


Documents

wiwo