High-voltage high-frequency Marx-bank type pulse generator using integrated power semiconductor half-bridges

Transcription

1 High-volage high-frequency Marx-bank ype pulse generaor using inegraed power semiconducor half-bridges L.M. Redondo 1,2, J. Fernando Silva 1,3,4, P. Tavares 5, Elmano Margao 1,4 1 Insiuo Superior de Engenharia de Lisboa Rua Conselheiro Emídio Navarro 1, Lisboa, Porugal 2 Cenro de Física Nuclear da Universidade de Lisboa Avenida Prof. Gama Pino 2, Lisboa, Porugal 3 Insiuo Superior Técnico Av. Rovisco Pais 1, Lisboa, Porugal 4 Cenro de Auomáica da Universidade Técnica de Lisboa Av. Rovisco Pais 1, Lisboa, Porugal 5 Indúsrias Lever Poruguesa S.A. R. Cidade de Goa, 22-24, Sacavém, Porugal lmredondo@deea.isel.ipl.p, fernandos@alfa.is.ul.p, Pedro.Tavares@unilever.com, emargao@deea.isel.ipl.p Acknowledgemens The auhors would like o hank Insiuo Superior Técnico, Insiuo Superior de Engenharia de Lisboa and Fundação da Ciência e da Tecnologia for supporing his work. Keywords Energy sorage, High frequency power converer, High power discree device, Power supply. Absrac This paper discusses he operaion of an all silicon-based soluion for he convenional Marx generaor circui, which has been developed for high-frequency (khz), high-volage (kv) applicaions needing recangular pulses. The convenional Marx generaor, for high-volage pulsed applicaions, uses passive power componens (inducors or resisors), o supply he energy sorage capaciors. This soluion has he disadvanages of cos, size, power losses and limied frequency operaion. In he proposed circui, he bulky passive power elemens are replaced by power semiconducor swiches, increasing he performance of he classical circui, srongly reducing coss, losses and increasing he pulse repeiion frequency. Also, he proposed opology enables he use of ypical half-bridge semiconducor srucures, and ensures ha he maximum volage blocked by he semiconducors equals he power supply volage (i.e. he volage of each capacior), even wih mismaches in he synchronized swiching, and in faul condiions. A laboraory prooype wih five sages, 5 kw peak power, of he proposed silicon-based Marx generaor circui, was

2 consruced using 12 V IGBTs and diodes, operaing wih 1 V d-c inpu volage and 1 khz frequency, giving 5 kv / 1 A pulses, wih 1 µs widh and 5 ns rise ime. Inroducion High-volage pulsed power is now a very imporan research field and an expanding indusrial echnology wih major worldwide economical impac. From he earlier high energy physics, paricle acceleraors and weapons applicaions, i has grown up o he commercial semiconducor and meal reamen process applicaions. New process for food serilizaion, wase reamen, polluion conrol, medical diagnosics and reamen are also being developed, which require high-volage pulses, needing efficien and suiable pulsed power supplies, based on power semiconducor swiches and on new opologies brough from power elecronics [1]. One aracive applicaion is plasma immersion ion implanaion (PIII), a versaile, relaively new, surface reamen echnique for implaning ions. Where, he sample is immersed in a plasma chamber, and shor, almos recangular, negaive high-volage pulses are applied o i, resuling in he acceleraion of he plasma ions o he sample surface and subsequen implanaion of he sample [2]. The mos widely used echnique o generae high volages, combines a high volage power supply wih semiconducor swiches, eiher in series or resonan circui associaions o overcome he high volage limiaions of semiconducor devices. The use of sep-up ransformers, o furher increase he oupu volage pulses, is limied due o he exisence of he ransformer parasiic elemens ha worsens he pulse shape [3]. Anoher widely used mehod for generaing high-volage pulses is he Marx generaor circui [4], as shown in Fig. 1, charging capaciors (C i ) in parallel and discharging hem in series ino he load (hrough a number of swiches, S i ), where he subscrip i {1, 2,, n-1, n}. The Marx generaor requires only a relaively low-volage power supply, V dc, for charging and does no require pulse ransformers o achieve he desired high-volage. The concep shown in Fig. 1 has been used inensively hrough he years, changing he swich echnology, from spark gaps o vacuum or gas ubes and nowadays o solid-sae semiconducors, and alernaing resisive charging sysems wih inducive ones, Z i. These echnological upgrades increased he life-ime of he circui and he pulse repeiion frequency, meaning an improved performance [5-9]. Z 1 Z 2 Z (n-1) Z n r i S 1 S 2 S (n-1) S n V dc C 1 C 2 C (n-1) C n Load v Z 1 Z 2 Z (n-1) Z n i Fig. 1. Basic opology of he Marx generaor circui, wih n sages, for negaive oupu pulses o he load. This work is suppored by FCT POSI/ ESE/38963/21

3 However, he use of bulky passive elemens (resisors or inducors, Z i ), as shown in Fig. 1, for charging he energy soring capaciors, C i, and o limi he self-discharging of he capaciors, during he series operaion, conribues o he low yield and efficiency of he circui, limiing he pulse frequency, due o he long charging ime consans, and degrading he generaion of almos recangular pulses. Therefore, in he circui here proposed, Fig. 2, o increase he performance of he classic Marx-bank generaor opology, Fig. 1, no charging resisors or inducors are used. Insead, an all-silicon-based soluion is obained. Volage increase is achieved by charging capaciors in parallel, hrough power semiconducor swiches (IGBTs and diodes), and hen discharging hem in series by opening he charging swiches, and closing he discharging ones. The circui opology and operaion mode block any self-discharging capacior pah. Due he power semiconducor opology used, almos recangular highfrequency pulses can be obained. Also, he proposed opology enables he use of ypical half-bridge semiconducor srucures, while ensuring ha he maximum volage blocked by he IGBTs is he volage of each capacior (i.e. he power supply volage), even when he swiching is no well synchronized, and even in faul condiions. A laboraory prooype wih five sages, 5 kw peak, of his silicon-based Marx generaor circui, was consruced using 12 V IGBTs and diodes, operaing wih 1 V d-c inpu volage and 1 khz repeiion frequency. Firs experimenal resuls show almos recangular pulses wih 5 kv /1 A, near 5ns rise ime and 1 µs widh, ino a resisive load. Circui Topology Due o he inensive used of solid-sae swiches o charge and discharge he energy soring capaciors sages, he circui will be named here as All-Elecronic Marx Generaor (AEMG). The basic opology of he AEMG, wih n sages, able o deliver negaive high-volage oupu pulses o a load, is presened in Fig. 2. Each sage of he AEMG consiss of a energy soring capacior C i, a diode D ci and wo IGBTs (T ci and T di ), where he subscrip i {1, 2,, n-1, n}. Oupu posiive pulses are simply obained by invering he polariy of all semiconducors as well as changing D ci wih T ci. T c1 T c2 T c(n-1) T cn r i V dc C 1 C 2 C n-1 C n Load v T d1 T d2 T d(n-1) T dn i D c1 D c2 D c(n-1) D cn Fig. 2. Basic opology of he AEMG circui, wih n sages, for negaive oupu pulses o he load. The AEMG operaion in Fig. 2 can be undersood, considering only wo differen operaing modes. In he firs one, swiches T ci and T di are, respecively, on and off. During his period, capaciors C i are charged

4 from he dc power supply, V dc, hrough T ci and D ci, as shown in Fig. 3, wih curren limied by he inernal resisance of he elemens, resuling in a small ime consan ha enables khz operaion. The on sae of D ci ensures ha, during his period, he volage, v, applied o he load is approximaely zero, as shown in Fig. 5, for a resisive load. Due o he parallel charging opology of he capaciors during his period, he charge currens are larger in he firs sages. During saring on, he volage V dc is slowly increased o limi he charging curren on he semiconducors T ci and D ci. T c1 T c2 T c(n-1) T cn r i V dc C 1 C 2 C n-1 C n Load v i D c1 D c2 D c(n-1) D cn Fig. 3. Capaciors charging operaion mode of he EMG in Fig. 2. In he second operaing mode, swiches T ci and T di are, respecively, off and on. During his period, capaciors C i are conneced in series and he volage applied o he load is, approximaely, v = nv dc (1) considering ha all capaciors are charged wih V dc, as shown in Fig. 4. However, his holds: i) on he characerisics of he componens; ii ) on he operaing frequency; iii) on he capaciors charge ime, c, being much longer ha discharge ime, d, meaning ha T ci and T di operae, respecively, wih a long (δ c = c /T) and shor (δ d = d /T) swiching duy cycle, as shown in Fig. 5. The off-sae of D ci ensures, during his period, ha capaciors are no shor-circuied by T di swiches. C 1 C 2 C n-1 C n Load v T d1 T d2 T d(n-1) T dn i Fig. 4. Pulse operaion mode of he AEMG in Fig. 2. I is imporan ha, during he pulse, he volage drop, due o he discharge of he energy soring capaciors, is only a few percen of each capacior volage. To guaranee his, he energy sored in he capaciors,

5 E = n cap C v 2 2 i c (2) where v c is he volage in he n capaciors, mus be nearly 1 imes greaer han he energy delivered by each volage pulse, o he load [2], E pulse = nvdci d where d is he on sae period of T di and i is he pulse curren, i = nv dc Z load (4) considering a resisive load and all capacior charged wih V dc, as shown in Fig. 5. For he above condiions, he plaeau of he pulse volage decreases exponenially, during he duraion of he pulse, described by (3) v = nv dc e ( / C eq R eq ) (5) where C eq is he capaciance equivalen o he series of C i, and R eq represens he equivalen series resisance of he circui during his period, which is normally relaively low. v gs (T di ) a) v gs (T ci ) V i b) v c) c V i T -nv dc d i d) nv dc /Z load Fig. 5. Theoreical wave forms for he operaion of he AEMG of Fig. 2, considering a resisive load: a) Drive signal of semiconducors T di ; b) Drive signal of semiconducors T ci ; c) load volage, v ; d) load curren, i.

6 The opology of he AEMG, in Fig. 2, guaranees ha, if problems wih he swiching synchronizaion occur or in fauly condiions, he maximum volage ha each semiconducor holds is V dc (maximum charge volage of capaciors C i ). As an example, if swich T dn swiches o on-sae somewha laer han he remaining T di swiches, diode D n says on during his period, mainaining he volage a he erminals of T dn equal o he capacior C n volage. During his condiion he load volage is, roughly, ( n ) V dc v = 1 In addiion o he above described advanages, he swiching sequence and swich configuraion, seen in Fig. 2, enables he use of ypical half-bridge semiconducor srucures currenly inegraed in modular packages, which is advanageous o build he circui and o drive he semiconducors. I is imporan o avoid cross conducion beween T di and T ci swiches, due o he circui opology in Fig. 2. Therefore, a dead ime is inroduced beween he swiching inpu conrol signals, so ha he urn-on conrol inpu o T di IGBTs is delayed wih respec o he urn-off conrol inpu of T ci IGBTs, and viceversa. Addiionally, due o he fac ha, here are wo drive signals for he solid-sae swiches, in he circui of Fig. 2, v gs(tdi) and v gs(tci), respecively, o T d i and T ci, which mus be driven synchronously, he complexiy of he driving circui is increased, compared o he circui in Fig. 1. Moreover, all he semiconducor swiches are a differen poenials, requiring gae circuis wih galvanic isolaion (opic fibres are used o ransmi he gae signals). (6) Experimenal Resuls A laboraory prooype of he AEMG circui of Fig. 2, wih five sages, 4.5 µf capaciors, was buil using 12 V IGBTs and diodes, operaing wih V dc =1 V, 1% duy cycle and 1 khz repeiion rae. Fig. 6 shows he pulse pulse, v, and pulse curren, i, for a resisive load. a) b) Fig. 6. Experimenal resuls for he AEMG of Fig.2, horizonal scale 2 (µs/div): a) Volage pulse, v, 1 (V/div); b) Curren, i, 2 (A/div).

7 a) b) Fig. 7. Experimenal resuls for AEMG of Fig. 2, Volage pulse, v, 1 (V/div), horizonal scale: a) 5 (µs/div), b) 1 (ns/div) The volage pulse, in Fig. 7 a), exhibi an almos recangular shape wih - 5 kv ampliude and 1 µs widh, giving 1 A, ino a resisive load, Fig. 7 b). The 1 khz pulse frequency is observed in Fig. 8 a), and he 5 ns pulse rise ime is shown in Fig. 8 b). Conclusion This paper proposed a new all-silicon-based Marx-bank circui opology for high-volage, high frequency pulse generaor circui for recangular pulsed applicaions. In his new circui, he bulky passive power elemens, used o charge he energy soring capaciors, were replaced wih power semiconducor swiches, increasing he performance of he classical circui, srongly reducing cos, losses and increasing he pulse repeiion frequency. Also, he proposed opology enables he use of ypical half-bridge semiconducor srucures, and ensures ha he maximum volage blocked by he semiconducors is he power supply volage, even wih mismaches in he synchronized swiching, and in faul condiions. A laboraory prooype wih five sages, 5 kw peak power, of his silicon-based Marx generaor circui, was consruced using 12 V IGBTs and diodes, operaing wih 1 V d-c inpu volage and 1 khz frequency, giving 5 kv / 1 A pulses, wih 1 µs widh and 5 ns rise ime. Using sae-of-he-ar kv IGBTs and diodes, high volage pulses reaching dozens of kv can be obained using he AEMG concep. References [1]. Cook, E. G.: Review of Solid-Sae Modulaors, Presened a he XX Inernaional Linac Conference, Monerey, Augus 2. [3]. Mark R. Brown. Using Nescape 4, Simon & Schuser MacMillan, Indianapolis, Indiana 4629, USA, [2]. Conrad, J. R.; Radke, J. L.; Dodd, R. A.; Worzala, Frank J.; Tran, Ngoc C.: Plasma source ion-implanaion echnique for surface modificaion of maerials, J. Appll. Phys., Vol. 62 (11), pp , 1 December [3].Goebel, D. M.; Pulse Technology, Chaper 8 de Handbook of Plasma Immersion Ion Implanaion & Deposiion, Edior Anders, André, 1 s ediion, John Wiley & Sons, New York, 2, p. 76, ISBN [4]. Willis, W. L.: Pulse-Volage Circuis, Chaper 3 de High Power elecronics, Edior Dollinger, R. E.; Sarjean, W. James, Tab Books Inc., 1 s Ediion, 1989, ISBN

8 [5]. Ghasemi, Z.; Macgregor, S.; Anderson, J.; Lamon, Y.: Developmen of am inegraed solid-sae generaor for ligh inacivaion of food-relaed pahogenic baceria, Meas. Sci. Technology, Vol. 14, pp. N26-N32, 23. [6]. O Loughlin, J.; Lehr, J.; Loree, D.: High repeiion rae charging a Marx ype generaor, Pulse Power Plasma Science, IEEE Conference, Diges of Technical Papers, Vol. 1, pp , June 21. [7]. Okamura, K.; Kuroda, S.; Maeyama, M.: Developmen of he high repeiive impulse volage generaor using semiconducor swiches, 12 h Pulsed Power Conference, Diges Of echnical Papers, Vol. 2, pp. 27-3, [8]. Rai, V.N.; Shukla, M.; Khardekar, R.K.: A ransisorized Marx Bank circui providing sub-nanosecond highvolage pulses, Meas. Sci. Technology, Vol. 5, pp , [9]. Vardigans, S.V.G.; Cogan, D.: A bipolar pulse eser for semiconducor devices, J. Phys. E: Sci. Insrum., Vol. 19, pp , 1986.