Bidirectional Flyback Converter with Multiple Series Connected Outputs for High Voltage Capacitive Charge and Discharge Applications

Transcription

1 Downloaded from orbi.du.dk on: Apr 21, 218 Bidirecional Flyback Converer wih Muliple Series Conneced Oupus for High Volage Capaciive Charge and Discharge Applicaions Thummala, Prasanh; Schneider, Henrik; Zhang, Zhe; Andersen, Michael A. E. Published in: Proceedings of 3h Annual IEEE Applied Power Elecronics Conference and Exposiion Link o aricle, DOI: 1.119/APEC Publicaion dae: 215 Documen Version Peer reviewed version Link back o DTU Orbi Ciaion (APA): Thummala, P., Schneider, H., Zhang, Z., & Andersen, M. A. E. (215). Bidirecional Flyback Converer wih Muliple Series Conneced Oupus for High Volage Capaciive Charge and Discharge Applicaions. In Proceedings of 3h Annual IEEE Applied Power Elecronics Conference and Exposiion (pp. 556). IEEE. DOI: 1.119/APEC General righs Copyrigh and moral righs for he publicaions made accessible in he public poral are reained by he auhors and/or oher copyrigh owners and i is a condiion of accessing publicaions ha users recognise and abide by he legal requiremens associaed wih hese righs. Users may download and prin one copy of any publicaion from he public poral for he purpose of privae sudy or research. You may no furher disribue he maerial or use i for any profimaking aciviy or commercial gain You may freely disribue he URL idenifying he publicaion in he public poral If you believe ha his documen breaches copyrigh please conac us providing deails, and we will remove access o he work immediaely and invesigae your claim.

2 Bidirecional Flyback Converer wih Muliple Series Conneced Oupus for High Volage Capaciive Charge and Discharge Applicaions Prasanh Thummala, Henrik Schneider, Zhe Zhang and Michael A. E. Andersen Elecronics Group, Deparmen of Elecrical Engineering Technical Universiy of Denmark Kongens Lyngby, DK28 Denmark Web: hp:// Absrac This paper evaluaes wo differen implemenaions of a bidirecional flyback converer for driving a capaciive elecro acive acuaor, which mus be charged and discharged from V o 2.5 kv DC and vice versa, supplied from a 24 V baery. In one implemenaion, a high volage MOSFET (4 kv) in series wih a high volage blocking diode is added, in parallel wih a high volage freewheeling diode of a convenional flyback opology, o enable bidirecional operaion. Experimenal resul from a digially conrolled bidirecional flyback converer shows ha he discharge energy efficiency is limied by he parasiics of he high volage acive componens, which also preven full uilizaion of valley swiching during discharge process. A second implemenaion is herefore proposed, where he secondary of flyback ransformer winding is spli ino muliple windings which are conneced in series by lower volage raing MOSFETs driven by a gae drive ransformer. Simulaion resuls o compare he operaion of convenional and proposed converers are provided. The advanages of proposed implemenaion are improved energy efficiency and lower cos. Experimenal resuls wih wo series conneced secondary windings are provided o validae he proposed implemenaion. NOMENCLATURE C in /C load Inpu capaciance / Load capaciance. C ou1 Balancing capacior across a series combinaion of one of he splied secondary winding and a secondary MOSFET. C ossp Oupu capaciance of he low volage MOS FET M p. C osss Oupu capaciance of he high volage MOS FET M s. C osss1 Oupu capaciance of one of he several series conneced MOSFETs (M s1 ) on he secondary high volage side. C j Juncion capaciance of he high volage diodes D 2 or D b. C s Self capaciance of secondary high volage winding of he flyback ransformer. C s1 Self capaciance of one of he secondary high volage splied windings of he flyback ransformer. D 2 High volage (5 kv) freewheeling diode which conducs while charging he capaciive load. D b High volage (5 kv) blocking diode which conducs while discharging he capaciive load. D bp /D bs Body diode of he MOSFET M p /M s. D bs1 Body diode of one of he several series conneced MOSFETs (M s1 ) on he secondary high volage side. i in /i p /i s Inpu / Primary / Secondary curren. i load Curren hrough he load. L mp /L ms Primary / Secondary magneizing inducance of a nonsplied flyback ransformer. L ms1 Secondary magneizing inducance of one of he splied winding of he flyback ransformer. L lkp /L lks Leakage inducance referred o primary / secondary of a nonsplied flyback ransformer. L lks1 Leakage inducance referred o secondary of one of he splied winding of he flyback ransformer. M p /M s Low volage / High volage (4 kv) MOSFET. M s1 One of he several series conneced MOSFETs on he secondary high volage side. n Turns raio from secondary o primary of he nonsplied flyback ransformer. n 1 Turns raio from one of he splied secondary o primary of he splied flyback ransformer. N p /N s Number of primary / secondary urns of he nonsplied flyback ransformer. N s1 Number of secondary urns on one of he splied secondary winding of he flyback ransformer. R p /R s DC resisance of low volage / high volage winding of he ransformer. R s1 DC resisance of one of he splied secondary high volage winding of he flyback ransformer. V Db /V D2 Volage across he high volage (5 kv) blocking / freewheeling diode. V Mp /V Ms Volage across he low volage / high volage (4 kv) MOSFET. V Ms1 Volage across one of he several series conneced MOSFETs (M s1 ) on he secondary high volage side. V in /V ou Inpu volage / Oupu or load volage.

3 I. INTRODUCTION Dielecric elecro acive polymer (DEAP) is an emerging smar maerial ha has experienced subsanial improvemen and has gained increasing aenion over he las decade from he researchers [1] [3]. The DEAP maerial is a very hin (4 μm) incompressible silicone elasomer film wih a complian elecrode layer on boh sides [5], [7]. DEAP can be considered as a pure capaciive load from an elecrical perspecive [6]. The basic behaviour of he DEAP acuaor is he reducion in he polymer hickness and he incremen in is area, due o an applied elecric field (46 V/μm) [7], [8]. The axial DEAP acuaor as shown in Fig. 1 is ideally equivalen o a capaciive load. When a DEAP acuaor is driven wih high volage (22.5 kv), i convers a porion of he elecrical energy ino mechanical displacemen, which is of he order of mm (1 1.5 mm) [4], [5]. Three of such axial DEAP acuaors are used o creae a DEAP incremenal acuaor [9] as shown in Fig. 2. DEAP, when used as linear incremenal acuaors, has he poenial o be an effecive replacemen for many convenional (e.g., piezo, pneumaic and hydraulic) linear acuaors due o is unique properies such as large srain, ligh weigh, and high flexibiliy. 33 mm 11 mm neced secondary windings is differen from aforemenioned converers, since i is aimed for bidirecional operaion, by replacing he diode wih a MOSFET on he secondary HV side. This paper is organized as follows: Secion II describes he convenional and proposed HV drivers. Secion III provides he simulaion resuls. Secion IV discusses he gae driver for he secondary HV side. Secion V provides he experimenal resuls and efficiency measuremens. Secion VI concludes he paper followed by he fuur work in Secion VII. II. HIGH VOLTAGE DRIVERS: CONVENTIONAL AND PROPOSED High efficien flyback based converers have been widely invesigaed and implemened by several researchers [18] [24]. Several bidirecional flyback converer opolofies have been proposed and implemened in [25] [29]. The convenional high volage bidirecional flyback converer [3], [31], for driving (charging and discharging) a DEAP acuaor wih a cerain acuaion frequency, is shown in Fig. 3. V in Low volage side i in C in i p C ossp D bp R p M p L lkp Energy flow L mp L ms R s V Mp 1:n L lks V Ms D b VDb D bs M s High volage side C s D 2 Cosss i s i load V D2 V ou C load Fig. 1. A linear DEAP acuaor manufacured by Danfoss PolyPower A/S. The DEAP acuaor applicaions [1], [11] require high volage (HV) bidirecional power elecronic converers, o charge and discharge he acuaor, and o ransfer par of he energy sored in i o he source. Swichmode power supplies for charging he capaciive loads have been implemened in [12] [15]. The flyback converer is suiable for low power (< 15 W) and high volage (2.5 kv) applicaions, due o is simple srucure and low componen coun [16]. In [17], [3], [32] [36], [44], [45] bidirecional flyback converers wih various power sages and conrol echniques, for charging and discharging DEAP acuaors have been proposed and implemened. The proposed converer wih muliple series con Fig. 2. A DEAP incremenal acuaor. Fig. 3. Convenional HV bidirecional flyback converer. An efficiency opimizaion echnique has been proposed in [32], [33] o improve he energy efficiency of he converer. Invesigaion of differen ransformer winding archiecures (TWAs) for he same opology has been proposed in [34]. A new digial conrol echnique o achieve he valley swiching during boh charge and discharge processes in a bidirecional flyback converer is proposed in [35], for beer energy efficiency and improved charge and discharge speed. Primary parallel, secondary series flyback converer wih muliple ransformers is proposed in [36], o reduce he equivalen selfcapaciance on he secondary HV side. The HV converer used in [9], [3], [32], [35], requires a HV (4 or 4.5 kv) MOSFET M s and wo HV (5 kv) diodes D 2 and D b as shown in Fig. 3. The 4 kv, 3 ma high volage IXYS MOSFET [37] has he following feaures: high onresisance of 29 Ω. high oupu capaciance of 19 pf. high reverse recovery ime of 2.8 μs. The 5 kv, 15 ma VMI high volage diode [38] has he following feaures:

4 onsae volage drop of 7 V. juncion capaciance of 3 pf. reverse recovery ime of 7 ns. Therefore, using a HV MOSFET M s and wo HV diodes D 2 and D b on he secondary side of he HV bidirecional DC DC converer, make i very expensive and inefficien. To reduce he volage raing of he high volage MOSFETs, series inpu and parallel oupu DCDC converers have been proposed and implemened in [39] [43]. The proposed HV bidirecional flyback converer is shown in Fig. 4. Using his opology, i is possible o series connec several lower volage (< 4 kv) raed MOSFETs each having a beer body diode (wih less reverse recovery ime). he need of high side gae drivers for driving some of he secondary MOSFETs. synchronous swiching of secondary MOSFETs. volage sharing among he secondary windings and he secondary MOSFETs. III. SIMULATION RESULTS Simulaions have been performed in pspice sofware o validae he proposed mehod, and he resuls are provided in Figs. 5 and 6. Vou,max 25 V Low volage side Energy flow High volage side V in i in i p C in Dbp C ossp M p R p L lkp L lks1 R s1 Lmp Lms1 V Mp 1:n 1 L lks2 R s2 L ms2 1:n 2 V Ms1 V Ms2 L lks3 R s3 C s1 C s2 i s Dbs1 M s1 Dbs2 M s2 C osss1 C osss2 i load C ou1 C ou2 V ou C load Fig. 5. V VD V 2.max Dbs 1.max V 5 Simulaion resuls during charge process for p =5sages. L ms3 C s3 Flyback ransformer wih muliple secondary windings 1:n 3 L ms4 1:n 4 V Ms3 L lks4 R s4 V Ms4 L lks5 R s5 C s4 Dbs3 M s3 Dbs4 M s4 C osss3 C osss4 C ou3 C ou4 Vou,max 25 V L ms5 1:n 5 V Ms5 C s5 Dbs5 C osss5 M s5 C ou5 VMs,max V Ms 1,max V V 5 Fig. 4. Proposed HV bidirecional flyback converer wih 5 series conneced secondary ransformer windings and MOSFETs on he secondary HV side. The advanages of he proposed opology are: reducion in he volage raing and price of he HV MOSFET. eliminaion of blocking and freewheeling HV diodes. possibiliy o achieve perfec valley swiching of HV MOSFET, unlike he semivalley swiching [35] (due o series connecion of HV diode D b and HV MOS FET M s during he discharge process). improved overall (charge and/or discharge) energy efficiency. However, he difficulies associaed wih he proposed converer are: Fig. 6. Simulaion resuls during discharge process for p =5sages. The simulaion parameers used for he convenional flyback converer (Fig. 3) are: V in =24 V, C load =4 nf, L mp =48 μh, L ms =3 mh, R p =6 mω, n=25, R s =13 Ω. Peak curren conrol has been implemened during boh charge (wih curren limi 5 A) and discharge (wih curren limi 2 ma) processes wih a fixed ime period of 22 μs (swiching frequency f sw =45.54 khz). The simulaion parameers used for he proposed flyback converer (Fig. 4) are he same as above, excep he urns raio (n 1 =5) and he secondary magneizing inducance (L ms1 =1.2 mh). In he simulaions, he leakage inducance and selfcapaciance are ignored and ideal swiches and diodes are being used. Figure 5, provides he comparison beween he oupu volages, and he volage across he secondary HV free wheeling diode V D2, and body diode V Ms1, for he convenional and proposed converers,

5 during charge process. Figure 6, provides he comparison of he oupu volages and he drainosource volage across he secondary MOSFET, for he convenional and proposed converers, during discharge process. When p series conneced ransformer and MOSFET sages are used in he secondary HV side of he proposed converer: he urns raio n 1 is reduced by p. he magneizing inducance L ms1 is reduced by p 2. he drianosource across he body diode of he secondary MOSFETs during he charge process is reduced by p. he drianosource across he secondary MOSFETs during he discharge process is reduced by p. Hence, o charge and discharge he capaciive load o and from 2.5 kv oupu volage, he 4 kv or 4.5 kv MOSFET on he secondary HV side, could be easily replaced by a 8 V MOSFET, when p =5sages are used in he secondary side. Table I provides he comparison beween he convenional and proposed converers in erms of losses due o he HV acive componens (a he maximum oupu volage during boh charge and discharge modes). Table II provides he comparison beween he convenional and proposed converers in erms cos and he volume occupied, when he real MOSFETs and HV diodes are used in he converer. TABLE I. LOSS COMPARISON BETWEEN THE CONVENTIONAL AND PROPOSED CONVERTERS Converer Loss during Loss during Toal Type charge process (W) discharge process (W) loss (W) Convenional L 1 =.168 L 3 = L 4 =4.9 Proposed L 2 =.192 L 5 =.61.8 TABLE II. COST AND VOLUME COMPARISON BETWEEN THE CONVENTIONAL AND PROPOSED CONVERTERS Converer Cos ($) Volume Toal Toal Type low quaniy occupied cos volume prices (mm 3 ) ($) (mm 3 ) Convenional 2 ( 1 for each 128 (64 each HV diode) diode) 3 (HV MOSFET) 134 (MOSFET) Proposed 5 (1 for each 44 (88 each 8 1 MOSFET), 3 (for gae MOSFET), driver) 56 (gae driver) In Table I he loss expressions are given by: L 1 = i avgc V ond2 (for HV diode D 2 ); L 2 = pi avgc V ondbs (for p =5HV body diodes); L 3 = i avgd V ondb (for HV diode D b ); L 4 = i 2 rmsd R dsons.5c osss V 2 Ms,max f sw V gs f sw Q gs (for 4 kv MOSFET M s ); L 5 = p(i 2 rmsd R dsons1.5c osss1 V 2 Ms1,max f sw V gs f sw Q gs1 ) (for p =5HV MOSFETs M si, i =1, 2...5); The parameers used are: i avgc =24mA,i avgd =19 ma, i rmsd =52 ma, V ond2 =V ondb =7 V, V ondbs =1.6 V, R dsons = 29 Ω (4 kv), R dsons1 =13Ω, C osss =19 pf, C osss1 =9.5 pf, V Ms =31 V, V Ms1 =62 V, V gs =12 V, Q gs =16.3 nc, Q gs1 =7.7 nc; In he above i avgc, i avgd, i rmsd are he average curren during charge and discharge modes, and RMS curren during discharge mode, respecively. Those values are exraced from he pspice simulaions. Also V ond2, V ondb, and V ondbs are he onsae diode drops of diodes D 2, D b and D bs1, respecively. IV. DRIVING THE SECONDARY SERIES CONNECTED MOSFETS USING A GATE DRIVE TRANSFORMER (GDT) In he proposed opology as shown in Fig. 4, he secondary HV side MOSFETs, need o be driven wih p 1 high side gae drivers, for p series conneced sages. I is possible o drive all secondary MOSFETs using a gae drive ransformer (GDT). Figure 7a) provides he full schemaic of he gae driver for 2 series conneced sages (p =2). The microconroller generaes enable signals for he dual lowside gae driver, whose oupus are fed o he GDT. The GDT as shown in Fig. 7a) has a single primary and wo secondary windings wih 1:1 urns raio. Secondary gae driver V A V B V C V D V G 1 S 1 V G 2 S 2 Microconroller A B Dual lowside gae driver C D Gae drive ransformer a) 5 V 5 V RM6core 15 urns 1:1 G1 To Gae 1 12 V S1 To Source 1 1:1 12 V 12 V 12 V 12 V G2 To Gae 2 12 V S2 To Source 2 5 V 5 V 12 V 12 V 12 V b) 12 V Fig. 7. a) Schemaic of he gae driver for driving wo secondary series conneced MOSFETs; b) Driving signals a differen nodes in he gae driver schemaic. The GDT is made using a RM 6 core, each winding has 15 urns wih.2 mm diameer. The wo isolaed oupus of he GDT are used o drive he 2 secondary series conneced MOSFETs. To proec he secondary MOSFETs from he volage spikes, a 12 V Zener diode is placed across he gae o source erminals of he wo MOSFETs. Driving signals a differen nodes in he secondary gae driver are shown in Fig. 7b). The wo primary winding erminals of gae drive ransformer (nodes C and D) are driven wih wo ouofphase signals. Posiive signal a he primary do erminal of GDT (node C), produces posiive gaeosource driving signals, and posiive signal a he primary nondo erminal of GDT (node D), produces negaive gaeosource driving signals, for he wo MOSFETs, respecively. In Fig. 7b), G 1,G 2,S 1 and S 2 represens he gae nodes and source nodes of he wo MOSFETs, respecively. The idea of driving he wo series

6 z conneced MOSFETs, using a GDT described above, can be used o drive more han 2 series conneced MOSFET sages (p >2). However, he ype of core used for he GDT can be changed depending on he number of sages. Primary curren ip Drain volage of Mp VMp Vou = 5 V, Vin =24V V. EXPERIMENTAL RESULTS The experimenal prooype of he convenional HV bidirecional flyback converer is shown in Fig. 8 [35]. The experimenal resuls showing he bidirecional operaion a 2.5 kv oupu volage are provided in Fig. 9. The primary MOSFET M p is 25 V, 16 A [FQD16N25CTM], he secondary side MOSFETs are 4 kv, 3 ma, 29 Ω [IXTV3N4S] and 4.5 kv, 2 ma, 75 Ω [IXTA2N45HV], and he HV diodes D 2 and D b are 5 kv, 15 ma [SXF6525]. However, for evaluaing he convenional and proposed converers, only 4 kv MOSFET is considered. The secondary MOSFET used in he proposed converer is 8 V, 1 A, 13 Ω [STN1NK8Z, [46]]. Gae drive signal of Mp Inpu volage Vin Fig. 1. Experimenal waveforms when he converer is operaed wih valley swiching during charge process; CH1: 2 A/div, CH2: 2 V/div, CH3: 5 V/div, CH4: 2 V/div, Time scale: 5 μs/div. Secondary curren is Drain volage of Ms VMs Vou = 2 V, Vin =24V Low volage side High volage side Gae drive signal of Ms Drain volage of Mp VMp Gae driver Comparaor 3 mm Fig. 11. Experimenal waveforms when he converer is operaed wih valley swiching during discharge process; CH1: 2 ma/div, CH2: 5 V/div, CH3: 5 V/div, CH4: 2 V/div, Time scale: 5 μs/div. To Low volage Microconroller MOSFET Flyback ransformer 9 mm High volage Diodes High volage MOSFET Fig. 8. Experimenal prooype of he digially conrolled convenional HV bidirecional flyback converer wih 4.5 kv MOSFET on he HV side [35]. Primary curren ip Inpu curren iin Oupu volage Vou Energy efficiency (%) Charge energy efficiency Discharge energy efficiency Oupu volage (kv) Fig. 12. Energy efficiency measuremens wih a 4 kv MOSFET on HV side. Drain volage of Mp Fig. 9. Experimenal resuls showing a single charge ( V o 2.5 kv) and discharge cycle (2.5 kv o V) [35]; CH1: 5 ma/div, CH2: 5 V/div, CH3: 5 A/div, CH4: 5 V/div, Time scale: 2 ms/div. A digial conrol echnique was recenly proposed in [35] o achieve valley swiching conrol during boh charge and discharge processes. In Fig. 9 a full charge/discharge cycle is shown. Figure 1 confirms he valley swiching operaion in charge mode. However, during discharge mode he valley volage of he drain of HV MOSFET M s is limied by he series conneced HV diode D b as seen in Fig. 11. The energy efficiency measuremens during boh charge and discharge modes as a funcion of oupu volage are provided in Fig. 12. The proposed converer is expeced o achieve ideal valley swiching during he discharge process leading o improved energy efficiency. VMp The converer specificaions are provided in Table III. The deails of flyback ransformer are shown in Table IV. To verify he concep of proposed converer, only wo series conneced secondary sages are considered. The 3 secondary urns are spli ino wo for each series conneced secondary winding (N s1 = 15). The parameers of he flyback ransformer are provided in Table V. I is a nonopimized (noninerleaved, nonsecioned) ransformer. The flyback ransformer used for he experimen is of noninerleaved and nonsecioned, and i is no propoerly opimized. However, for his applicaion, ransformer wih muliple secions would be beer choice o reduce he selfcapaciance. The experimenal resuls from he proposed converer wih 2 series conneced secondary sages (p =2) are shown in Figs. 13, 14 and 15, respecively. Figure 13 provides a single charge and discharge cycle using he proposed opology, when he capacior load is charged and discharged from V o 2 V, and vice versa. To verify he

7 proposed concep, during boh charge and discharge processes, he converer is driven wih fixed swiching frequency. During he charge process he swiching ime period is 59 μs, and during he discharge process, he swiching ime period is 1 μs. In Figs. 14 and 15, a comparison of drainosource volage across he wo secondary MOSFETs during a charge and discharge swihcing cycle are provided. Drain o ground volage of high side secondary MOSFET Source o ground volage of high side secondary MOSFET Drain o source volage of low side secondary MOSFET Drain o source volage of high side secondary MOSFET TABLE III. CONVERTER SPECIFICATIONS Parameer Inpu volage Capaciance of load Onime of primary MOSFET during he charge process Value 24 V 4 nf 9 μs Fig. 15. Comparison of he volage sress across he wo secondary MOSFETs during he discharge process using he proposed opology; CH1: 2 V/div, CH2: 2 V/div, CH4: 1 V/div,F3=C2C4: 2 V/div, Time scale: 1 μs/div. TABLE IV. DETAILS OF THE SPLITTED FLYBACK TRANSFORMER WITH A TURNS RATIO OF 25 Parameer Value Number of primary / secondary urns 12 / 3 Diameer of primary / secondary winding.5 mm /.12 mm Number of layers of primary / secondary winding 1/ 4 Type of core / maerial EF25 / N87 TABLE V. PARAMETERS OF THE SPLITTED FLYBACK TRANSFORMER Parameer Primary / Each splied secondary magneizing inducance Secondary nonsplied magneizing inducance Leakage inducance referred o primary / splied secondary Leakage inducance referred o nonsplied secondary Primary / Secondary splied winding DC resisance Secondary nonsplied winding DC resisance Selfcapaciance of each splied secondary winding Selfcapaciance of nonsplied secondary winding Vou,max = 2 V, Vin =24V Gae drive signal of Mp Oupu volage Value 42 μh / 6.3 mh 25 mh 1.1 μh / 53μH 721 μh 64 mω / 6.3 Ω 12.4 Ω 78.2 pf 37 pf Gae drive signal of Ms1 and Fig. 13. A charge and discharge cycle wih he proposed opology; CH1: 1 V/div, CH2: 1 V/div, CH3: 1 V/div, Time scale: 5 μs/div. Drain o ground volage of high side secondary MOSFET Drain o source volage of low side secondary MOSFET Drain o source volage of high side secondary MOSFET Ms2 Source o ground volage of high side secondary MOSFET Fig. 14. Comparison of he volage sress across he wo secondary MOSFETs during he charge process using he proposed opology; CH1: 2 V/div, CH2: 2 V/div, CH4: 1 V/div,F3=C2C4: 2 V/div, Time scale: 1 μs/div. VI. CONCLUSION In his paper, a bidirecional flyback converer wih muliple series conneced oupus is proposed, for high volage drive of capaciive DEAP acuaors. Simulaion resuls (oupu volages and volage sresses across he secondary MOSFETs/diodes) during boh charge and discharge processes are provided, o show a comparison beween he proposed and convenional implemenaions. A heoreical comparison shows ha he proposed converer has he poenial o improve efficiency and lower he cos. The deailed implemenaion of secondary gae driver, using a gae drive ransformer is provided. Experimenal resuls from he convenional (for full operaing volage range 2.5 kv) and he proposed (2 V) bidirecional converers are provided. The experimenal waveforms of he drainosource volages of he wo secondary MOSFETs confirms he volage sharing across he wo MOSFETs. VII. FUTURE WORK Due o lack of ime he converer operaion for full operaing volage range, and wih p =5series conneced secondary sages is no verified. However, he fuure work regarding he proposed converer involves: implemening he valley swiching conrol during boh charge and discharge processes. design and implemenaion of he gae drive ransformer for p =5sages. design of he efficien flyback rasformer wih very low selfcapaciance. invesigaing he coupling facor of differen winding sraegies inerms of volage sharing. REFERENCES [1] Y. BarCohen, Elecroacive Polymer [EAP] Acuaors as Arificial Muscles: Realiy, Poenial, and Challenges, 2nd ed. Washingon, DC: SPIE, 24. [2] R. E. Pelrine, R. D. Kornbluh, Q. Pei, and J. P. Joseph, Highspeed elecrically acuaed elasomers wih srain greaer han 1%, Science, vol. 287, pp , 2. [3] F. Carpi, D. DE Rossi, R. Kornbluh, R. Pelrine, and P. SommerLarsen, Dielecric Elasomer As Elecromechanical Transducers, Amserdam, Neherlands: Elsevier, 28. [4] M. Tryson, H. E. Kiil, M. Benslimane, Powerful ubular core free dielecric elecro acive polymer (DEAP) push acuaor, in Proc. SPIE, vol. 7287, 29.

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