Scattering Parameter-based Measurement of Planar EMI filter

Transcription

1 8 Journal of Power Electronic, Vol. 4, No. 4, pp. 883, July 4 JPE 44 IN(Print): 989 / IN(Online): 9348 cattering Parameterbaed Meaurement of Planar EMI filter hihan Wang, Min Gong *, and Chenchen Xu * * Jiangu Key aboratory of New Energy Generation and Power converion, Nanjing niverity of Aeronautic and Atronautic, Nanjing, China Abtract Planar electromagnetic interference (EMI) filter are widely ued to retrain the conducted EMI of witching power upplie. uch filter are characterized by mall ize, low paraitic parameter, and better highfrequency performance than the paive dicrete EMI filter. However, EMI filter performance cannot be exactly predicted by uing exiting method. Therefore, thi paper propoe a method to ue cattering parameter (parameter) for the meaurement of EMI filter performance. A planar EMI filter ample i etablihed. From thi ample, the relationhip between parameter and inertion gain (IG) of EMI filter i derived. To determine the IG under different impedance, the EMI filter i theoretically calculated and practically meaured. The differential tructure of the nearfield coupling model i alo deduced, and the IG i calculated under tandard impedance condition. The calculated reult and actual meaurement are compared to verify the feaibility of the theory. Key word: Inertion gain (IG), Nearfield couple, Planar EMI filter, cattering parameter (parameter) I. INTRODCTION Electromagnetic interference (EMI) i a eriou problem in the development of the witching power upply and affect the normal operation of the grid and urrounding equipment []. According to the different interference pattern, EMI can be claified into two form: radiated and conducted emiion. The latter i the mot eriou concern in power electronic ytem. To meet the EMC tandard, an EMI filter i often ued to attenuate the conducted EMI noie. Fig. how a typical meaurement etup. ine impedance tabilization networ (IN) ha been traditional ued to determine the pecified impedance over the woring frequency range. In particular, noie can be meaured when both ource and load impedance are Ω. An EMI filter i placed between IN and the equipment under tet (ET), which i compoed of the common mode (CM) and differential mode (DM) filter. In the EMI filter, the left DM capacitor Cx bypae mot of the DM noie becaue of the low Cx impedance. The remaining noie i bloced by the DM, which i the leaage inductance of CM Manucript received Jul., 3; accepted May, 4 Recommended for publication by Aociate Editor TaeWoong Kim. Correponding Author: Wanghihan@nuaa.edu.cn Tel: 88489, Nanjing niv. of Aeronautic and Atronautic * Jiangu Key aboratory of New Energy Generation and Power converion, Nanjing niverity of Aeronautic and Atronautic, China 4 KIPE inductance. The right DM capacitor Cx bypae mot of the remaining DM current becaue of the high IN impedance. C Y i the CM capacitor and CM i CM inductance, which contitute the CM filter ued to attenuate the CM noie. A conventional EMI filter comprie up to onethird of converter volume and weight.. To reduce the ize of paive component, an integration technology that implement multiple function into one component i propoed. The development of integration technology ha made integrated EMI filter an important mean to reduce the volume and weight of the whole converter. Among thee integrated EMI filter, the planar EMI filter i the focu of thi tudy. imilar to the conventional EMI filter, the planar EMI filter i compoed of the CM and DM part [][4]. The core component of the planar EMI filter i an annular inductorcapacitor unit. To analyze the performance of the planar EMI filter and EMI noie tranmiion, parameter are employed []. The performance of EMI filter i often evaluated on the bai of inertion gain (IG) []. However, matching tate i difficult to achieve in both the ource and load in practical implementation. Conequently, the EMI filter i alo difficult to elect on the bai of the IG curve given by manufacturer. Therefore, the election of the ource and load impedance i important. Thi election ignificantly affect filter performance. Notably, failing to elect the appropriate

2 cattering Parameterbaed Meaurement of Planar EMI filter 8 impedance will ometime magnify noie. In the highfrequency range, the effect of nearfield coupling on the EMI filter i ometime more evere than that of the paraitic parameter of component []. When the nearfield coupling effect of component i conidered, parameter extraction become epecially ignificant. Numerou extraction method, uch a the impedance and parameter method, can be elected. However, the impedance method cannot guarantee the ideal hortcircuit and opencircuit of the port, a well a the accuracy of branch and tray impedance, at high frequencie. Therefore, the parameter method i elected to extract the nearfield coupling parameter while avoiding the aforementioned problem [8]. everal tudie [9][] have propoed method to etablih the highfrequency model on the bai of the impedance meaurement method. However, enuring that one end of the filter i a hort circuit or open circuit i difficult under high frequency. In practice, model parameter accuracy i difficult to guarantee. More importantly, the exiting model are unrelated, which caue problem attributed to the lac of coupling parameter. Compared with thoe of the filter compoed of dicrete component, the coupling parameter of a planar filter are more eriou becaue all cell are integrated into a core. Therefore, the model etablihed by uing the impedance meaurement method i inufficiently accurate when applied to a planar filter. For intance, literature [] reveal that the actual inertion lo i obtained through the calculation of the minimum I and coefficient. In fact, the I propoed in [] i the oppoite of IG. However, numerou parameter are ignored in the calibration coefficient proce, which caue low accuracy. Conequently, thi approach ha a certain application limitation. Baed on the above analyi, parameter are ued to meaure the characteritic of the EMI filter in thi tudy. Combining the reflection coefficient of the noie ource with the load port enable the calculation of the filter IG. To etablih a model with enhanced highfrequency characteritic, parameter are ued to meaure and calculate the coupling parameter of the planar filter. II. MEAREMENT OF FITER CHARACTERITIC BY ING PARAMETER A. Planar EMI Filter tructure Applying the planar magnetic integration technology to the EMI filter and uing a planar C a a baic cell can realize the miniaturization of planar EMI filter. The baic principle of a planar EMI filter are imilar to thoe of the dicrete EMI filter (Fig. ), both which contain the CM and DM part. The CM module (Fig. 3) i formed by the C unit compoed of integrated inductance and capacitance. The planar C unit V AC Fig.. Meaurement etup. Fig.. tructure of planar EMI filter. Fig. 3. Integrated unit of planar C. ue a high dielectric contant ceramic a the ubtrate. Either ide of the ubtrate i covered with one or more turn. The DM module i compoed of DM capacitance and DM inductance. When the common mode choe i not wounded tightly, it will produce leaage inductance, that i DM mode inductor. B. Parameter According to tranmiion line theory [3], the normalized equivalent voltage and equivalent current at any port reference urface for an nport networ are a follow: For port, and () I I I () I are the normalized incident voltage and normalized incident current wave, repectively. imilarly, and W IN C X CM DM * * W I are the normalized reflection voltage and normalized reflection current wave, repectively. For a networ characterized by parameter [4], the port impedance meet the requirement of conjugate matching. The normalized incident and reflection voltage are derived a V I Z (3) Re( Z ) C Y Cx C Y EMI filter ET

3 88 Journal of Power Electronic, Vol. 4, No. 4, July 4 V Fig. 4. Twoport microwave networ model. V : witch power upply noie ignal Z, Z : noie ource impedance and load impedance, : normalized incident voltage wave, : normalized reflection voltage wave V, V : Z port voltage * V I Z * Z (4) Re( ) In the equation, V, I are the voltage and current of the port, repectively; Z i the input impedance of the EMI filter; and Z * i the output impedance of the filter. Equation () and () can yield, a follow: ( I ) / () ( I ) / () Tranforming the port characteritic on all port enable the derivation matrice of the incident and reflected wave of the normalized equivalent voltage. The matrix expreion i given by ( I ) /, ( I ) / () When the networ i linear, ubtituting Z I into Equation () yield ( Z E)( Z E) (8) In the equation, E i the unity matrix. Etablihing the matrix, ( Z E)( Z E) The expanion form of Equation () i é ù é n ù é ù ê ú ê ú ê ú ê ú n ê ê ú ê ú M ú ê M M O M ú ê M ú ê ú ê ú ê ú n n n êë úû ë nn û êë ú n û where i nown a the parameter or parameter. C. Parameter of EMI Filter (9) () Characterizing an EMI filter a a linear paive i reaonable only under the condition of mallignal excitation. Fig. 4 how the tet etup for an EMI filter, which i characterized in term of wave. Moreover, nonlinear characteritic can be imulated by adding mallignal excitation to the DC bia. V V Z Fig.. cattering parameter ignal flow of EMI filter. Fig.. ingle port model of EMI filter. From the normalized port voltage definition and Equation () and (), the port voltage and current of two port networ can be derived a ( V ) Z () I ( ) / Z () where Z i a poitive real number that repreent the reference impedance of the port. According to parameter theory and Equation (), we derive é ù é ù é ù ê ú ê ú ê ú (3) êë úû ë û êë úû When reflected to the noie ource or load ide, and will alo be reflected to the oppoite poition becaue of mimatched impedance. The reflection coefficient, Г at ource ide and Г at load ide, are given by [] G ( Z Z ) / ( Z Z ) (4) G ( Z Z ) / ( Z Z ) () The current of the circuit in Fig. 4 i characterized by the ignal flow graph hown in Fig.. Fig. and how that repreent the normalized voltage wave, which i emitted by the noie ource. V Γ Z V V and are the normalized incident and normalized reflection voltage wave of the ource port. For the EMI filter, when the impedance Z of noie ource i determined, the normalized voltage wave i given by V I Z V I Z () Re( ) Z Z V I Z V I Z () Re( ) Z Z I V / ( Z Z ) (8) Γ Z

4 cattering Parameterbaed Meaurement of Planar EMI filter 89 According to Equation (), (9) Z V / ( Z Z ) () After meauring the parameter, the Maon formula and ignal flow diagram can be ued to deduce,,, and. According to Equation (9) and (), the port voltage and current are further calculated. The ultimate goal of the EMI filter i to control the noie energy tranmitted to the load ide under a certain tandard. Extracting the loadide power i important. According to parameter theory, the normalized power of the load ide i [4] IN REF G P P P ( ) () By uing the Maon formula to analyze Fig., we determine that / D () where D ( G G G G ) G G (3) P P / D ( G ) (4) P i the normalized power of ource port P P / ( G ) () The EMI filter networ energy tranmiion gain i given by D G G G log( P / P ) / ( )( ) ( G )( G ) ( G )( G ) G G () From Equation (), the energy tranmiion characteritic of the filter networ can be extracted by uing the parameter. Thereafter, the operating characteritic of the networ can be expreed. However, IG hould be further tudied becaue of the difference in the characteritic of tranmiion gain and IG. D. IG Calculated by Parameter In an actual ytem, the IG under the condition of pecific impedance hould be accurately obtained. IG refer to the ratio of the voltage V (or power P ) and voltage V (or power P ) []. When the filter i connected between the load and power ide, thi voltage can be expreed in decibel form (DB). V i the load voltage when the EMI filter i placed between the load and ource ide, wherea V refer to the voltage without the filter. IG log( V / V ) [ V Z Z V I Z ] log ( / ) / ( ) According to Equation () and () () TABE I TRCTRE PARAMETER OF PANAR EMI FITER Core C unit DM capacitor P43 Turn 4 Thicne.8 mm ubtrate permittivity Turn 3 Thicne.8 mm ubtrate permittivity V Z ( ) (8) V Z ( ) (9) I ( ) / Z (3) é ( / / )( Z / Z ) ù IG log ê ú (3) ë ( Z / Z ) / ( Z / Z ) / û According to the Maon formula, / G / D (3) / ( G ) / D (33) / [ ( G ) G ] / D (34) é ( GG ) ù IG log ê ú ë ( G )( G ) G G û (3) From (4) and (), when the Г and the Г are equal to zero, the ource and load impedance are in a matching tate. Therefore, in Equation (3) i the IG. However, when the impedance are mimatched, the reflection parameter Γ and Γ can be calculated to improve EMI filter deign. For witching power upply, determining the hardware circuit enable the noie impedance Z of the loop to be obtained through analyi and teting. The load impedance Z of the EMI filter i the input impedance of the former device or the tandard impedance, which i provided by IN.,,, and can be meaured by uing an parameter teter (Agilent 8A). The parameter teter ha a calibration function, and it attenuation can be iolated from the noie and energy of the meauring line. Without hortcircuit and opencircuit, the parameter tet value are more precie compared with the impedance tet value of Y Z parameter in the high frequency. III. TETING PARAMETER AND INERTION GAIN OF EMI FITER Thi tudy ue a typical planar EMI filter tructure compoed of the integrated capacitance of differential mode, leaage inductance layer, integrated C unit, and magnetic core. Fig. how the electrical configuration. Table I preent the parameter of the baic cell tructure. The tet apparatu ue the Agilent 439A and Agilent 8A networ analyzer to tet the parameter of the DM and CM tructure in the planar filter, repectively. Taing

5 8 Journal of Power Electronic, Vol. 4, No. 4, July 4 Phae Amplitude Phae / o Fig. 8. Comparion of IG with different impedance. 4 Amplitude 8 Phae Phae / o Z Ω, Z Ω Z Ω, Z Ω 3 Z Ω, Z Ω Magnitude/dB 8 Phae Amplitude Phae / o Fig. 9. Calculated curve of IG for CM filter. Z Ω, Z Ω Z nf, Z Ω Amplitude Phae Fig.. Tet curve of parameter for DM filter Phae/ o the DM tructure a an example, Fig. how the amplitudefrequency and phaefrequency curve of the parameter. Fig. 8 clearly how that when noie ource and load impedance are changed, the influence of the different impedance characteritic of IG mut be conidered to optimize the planar EMI filter deign. To calculate the IG, the Agilent 439A Impedance Analyzer i ued to tet the parameter of the CM tructure. Fig. 9 how the calculated curve. ubequently, the ignal generator, voltmeter, IN, EMI filter, and ET are ued to etablih the tet circuit. The voltage before or after adding the EMI filter are determined by uing the voltmeter. The real incircuit attenuation of everal frequency point are then derived (Table II). A comparion of the IG value of curve in Fig. 9 and in Table II reveal that the actual tet value coincide with that calculated in the multiple frequency point. In Equation (3), the noie ource impedance ue the ideal capacitor impedance curve. Thu, the calculated reult are not fully conitent with the tet reult. everal error can be aumed between the meaured and calculated value.

6 cattering Parameterbaed Meaurement of Planar EMI filter 8 TABE II TET IG FOR CM FITER frequency/mhz.... IG/dB P C X M M P3 D P4 C X P P P P P Fig.. Nearfield coupling model of DM tructure. M M 3 P3 (a) C erie reonant connection. P P3 DM P3 PM M DMM P P P Fig.. Calculated M through equivalent capacitor branch. P (b) twoport connection. the C unit in term of pace poition. Meanwhile, M, M are equal becaue of the ymmetrical electrical and mechanical tructure of the planar EMI filter. P P (c) fourport connection. Fig.. Three ind of connection for integrated C unit. IV. EXTRACTION OF NEARFIED COPING PARAMETER IN A PANAR FITER BY ING PARAMETER A. Coupling Parameter of NearField for Planar EMI Filter tructure The highfrequency parameter of a planar filter differ from that of dicrete tructure. The traditional model (highfrequency paraitic mutual inductance) i no longer applicable. nder certain condition, the planar filter unit can be regarded a an integrated C tructure. Therefore, the ue of different connecting method will affect the equivalent erie inductance (E) of the integrated capacitor, a hown in Fig.. In Fig. 8, P, P are the line inductance, wherea i the planar C unit inductance. To reduce the integrated capacitor E and to form a complete EMI filter, the integrated C unit ue the connection method hown in Fig. (c). In the EMI filter frequency, the nearfield coupling parameter can be ued to expre mutual inductance. Without conidering the coupling parameter with negligible effect, the nearfield coupling parameter model of the DM tructure in the planar filter i a (Fig. ). Fig. how that P, P are the input and output inductance of the wire loop, repectively; and P3, P4 are the inductance between the interior unit of the planar filter. P3, P4 are ignificantly le than P, P. Moreover, the coupling effect can be diregarded becaue of the extreme cloene of P P B. e of Parameter to Extract Mutual Inductance To extract the M, M, a CM inductor and differential capacitor are removed from the core. Fig. how the equivalent twoport networ model. According to Fig., M i given by M 4p f C (9) where f i the reonant frequency of the capacitor branch. For the extraction of M 3, the CM inductance and retained C unit contituted by DM capacitance hould be removed. Fig. 3 how the highfrequency model. Fig. and 3 how that for any value of mutual inductance, the functional relationhip i hown in Fig. 4 after extracting amplitude and phae of the impedance of each branch in correponding Ttranmiion networ equivalent circuit. According to microwave networ theory, further extraction of mutual inductance parameter reult in the converion of the parameter into Ttranmiion networ parameter. The relationhip of the each branch impedance with the parameter of the Tnetwor (Fig. 4) are given by Z Z Z C. Experiment Z ( ) ( ) Z ( ) ( ) Z ( ) 3 (3) (3) (3) Table how the parameter of the planar filter. Fig. how the M, M, and M 3 extracted by uing Agilent 439A. The nearfield coupling model i created (Fig. ). Fig.

7 8 Journal of Power Electronic, Vol. 4, No. 4, July 4 P P3 P4 PM 3 PM 3 M 3 Fig. 3. Calculation of M3 through equivalent circuit. Port M 3 Z Z Z 3 Port Meanwhile, the IG i developed to predict the filter performance. The parameter can be ued to extract the nearfield coupling parameter. Therefore, etablihing an effective nearfield parameter model i poible. Compared with the traditional model, which only conider paraitic parameter, the nearfield coupling model can predict the characteritic of planar EMI filter more accurately. ACKNOWEDGMENT Fig. 4. parameter of Tnetwor. nh 8nH 3nH 3pF n.μh n 3nH 8nH n Thi tudy i upported by the Power Electronic cience and Education Development Program of Delta Environmental & Educational Foundation; National Natural cience Foundation of China; Jiangu Province niverity Outtanding cience and Technology Innovation Team Project. 3nH Fig.. Parameter for the nearfield coupling model. Magnitude/db 4 8 Fig.. IG for planar EMI filter. how the IG tet value of the differentialmode tructure and the model imulation. Fig. how that curve repreent the IG of the differential tructure in the planar filter. Curve i the calculation curve of the traditional differential tructure, which only conider it own paraitic parameter. Curve 3 repreent the IG of high frequency model when the near field coupling effect i conidered. A comparion of the three curve reveal that the calculation value of the two model are extremely cloe to their tet value in the lowfrequency band. However, in the highfrequency band after M, the calculation curve of IG with nearfield coupling i cloer to the meaurement curve than to the curve of the traditional differential tructure model. Therefore, the nearfield coupling model i better than the traditional differential model. Meanwhile, the parameter M, M, and M 3 are more uitable for the planar EMI filter. V. CONCION A method uing parameter to characterize EMI filter i dicued. A implified EMI filter model i propoed to help undertand the tranmiion characteritic of the port. 3 REFERENCE [] R.. Ozenbaugh, EMI Filter Deign, Taylor & Franci, nd ed.,. []. Wang and Chenchen Xu, Deign theory and implementation of planar EMI filter baed on annular integrated inductorcapacitor unit, IEEE Tran. Power Electron., Vol. 8, No. 3, pp., Mar. 3. [3] H. Hieh, J. i, and D. Chen, Effect of X capacitor on EMI filter effectivene, IEEE Tran. Ind. Electron., Vol., No., pp. 9499, Feb. 8. [4] H. Huang and. Deng, Improving the highfrequency performance of integrated EMI filter with multiple ground layer, AiaPacific ympoium on Electromagnetic Compatibility, pp. 49,. [] J. Drinovy, J. vacina, and P. Bednar, Operation amplifier in EMI filter inertion lo meaurement etup, Radioeletronia, th International Conference, pp. 3, Apr.. []. Wang, F. C. ee, and W. G. Odendaal, Characterization and paraitic extraction of EMI filter uing cattering parameter, IEEE Tran. Power Electron., Vol., No., pp., Mar.. [] W. Chen,. Feng, H. Chen, and Z. Qian, Near field coupling effect on conducted EMI in power converter, in 3th IEEE Power Electronic pecialit Conference, PEC ', pp. 9,. [8]. Wang and F. C. ee, ing cattering parameter to characterize EMI filter, in 3th IEEE Annual Conference on Power Electronic pecialit Conference, pp. 933, 4. [9] V. Tarateeraeth, K. Y. ee, F. G. Canavero, and R. W. Chang, ytematic electromagnetic interference filter deign baed on information from incircuit impedance meaurement, IEEE Tran. Electromagn. Compat., Vol., No. 3, pp. 8898, Aug.. [] J. Epina, J. Balcell, A. Aria, C. Ortega, and N. Berbel, EMI model of an AC/AC power converter, Vehicle Power and Propulion Conference ( VPPC), pp.,.

8 cattering Parameterbaed Meaurement of Planar EMI filter 83 [] J. Pleite, R. Pietro, R. Aeni, J. A. Cobo, E. Olia, Obtaining a frequencydependent and ditributedeffect model of magnetic component from actual meaurement, IEEE Tran. Magn., Vol. 3, No., pp. 4494, Nov [] J. Drinovy, J. vacina, M. Zamazal, T. rbanec, and J. aci, Variable impedance in meauring EMI filter inertion lo, Communication, AiaPacific Conference on, pp. 4,. [3] D. M. Pozar, Microwave Engineering, John Wiley & on, Inc, 998. [4]. Beer and R. Gilmore, Practical RF Circuit Deign for Modern Wirele Communication ytem, Artech Houe Publiher, pp. 349,. []. Wang, F. C. ee, and W. G. Odendaal, Characterization and paraitic extraction of EMI filter uing cattering parameter, IEEE Tran. Power Electron., Vol., No., pp., Mar.. [] D. Zhang, D. Y. Chen, and D. able, A new method to Characterize EMI Filter, Applied Power Electronic Conference and Expoition, Vol., pp , 998. Min Gong wa born in China in 989. he received her B.. in Electrical Engineering degree from Nanjing niverity of Aeronautic and Atronautic, Nanjing, China, in. At preent, he i puruing an M.. degree in Electrical Engineering at the ame univerity. Her main reearch interet include the electromagnetic compatibility of power electronic ytem. hihan Wang wa born in haanxi Province, China, in 9. He received hi Ph. D in Electrical Engineering in 3 from Xi an Jiaotong niverity, China. He i currently woring at Nanjing niverity of Aeronautic and Atronautic in the Department of Electrical Engineering. Hi reearch interet include the electromagnetic compatibility of power electronic ytem, electromagnetic numerical calculation, and it application in electrical device. Chenchen Xu received her B.. degree in Electrical Engineering and automation from the Anhui niverity of Technology, Anhui, China, in. At preent, he i woring to complete her M.. degree in Electrical Engineering at Nanjing niverity of Aeronautic and Atronautic, Nanging, China. Her main reearch interet include electromagnetic compatibility of power electronic, a well a the deign and development of a new type electromagnetic interference filter.