Coreless Printed Circuit Board (PCB) Stepdown Transformers for DC-DC Converter Applications

Transcription

1 Vol:4, No:, Corele Printed Circuit Board (PCB) Stedown Tranformer for DC-DC Converter Alication Radhika Ambatiudi, Hari Babu Kotte, and Dr. Kent Bertilon International Science Index, Electrical and Comuter Engineering Vol:4, No:, waet.org/publication/554 Abtract In thi aer, multilayered corele rinted circuit board (PCB) te-down ower tranformer for DC-DC converter alication have been deigned, manufactured and evaluated. A et of two different circular iral te-down tranformer were fabricated in the four layered PCB. Thee tranformer have been modelled with the aitance of high frequency equivalent circuit and characterized with both inuoidal and quare wave excitation. Thi aer rovide the comarative reult of thee two different tranformer in term of their reitance, elf, leakage, mutual inductance, couling coefficient and alo their energy efficiencie. The oerating region for otimal erformance of thee tranformer for ower tranfer alication are determined. Thee tranformer were teted for the outut ower level of about 3 Watt within the inut voltage range of -5 Vrm. The energy efficiency for thee te down tranformer i oberved to be in the range of 9%-97% in MHz frequency region. Keyword Corele Ste down Tranformer, DC-DC Converter alication, High frequency tranformer, MHz oerating frequency, Multilayered PCB tranformer, Power Tranfer Alication. T I. INTRODUCTION HIS In thi modern era, where we can find miniaturized electronic circuit, lanar technology lay a rominent role becaue of their mall ize and reduced weight with high ower denity [], []. A ome of the alication demand electrical iolation and multile outut, tranformer have become the irrelaceable comonent in modern ower ulie. The witching frequencie of iolated ower ulie are limited to few hundred of khz becaue of the increaed hyterei and eddy current loe of core baed tranformer and the witching loe of the Power MOSFET at higher oerating frequencie. The other major roblem involved in high frequency magnetic are leakage inductance, kin and roximity effect and unbalanced magnetic flux ditribution, which generate localized hot ot and reduce the couling Radhika Ambatiudi i with the Deartment of Information Technology and Media, Mid Sweden Univerity, SE-857, Sundvall, Sweden, (hone: ; fax: ; Radhika.Ambatiudi@miun.e). Hari Babu Kotte i with the Mid Sweden Univerity, Deartment of Information Technology and Media, Mid Sweden Univerity, SE-857, Sundvall, Sweden, Hari.Kotte@miun.e). Dr. Kent Bertilon i with the Deartment of Information technology and Media, Mid Sweden Univerity, SE-857, Sundvall. Sweden ( Kent.Bertilon@miun.e). He i alo CEO and co-founder of SEPS Technologie AB, Storgatan 9, SE-857, and Sundvall, Sweden. coefficient [3]. The drawback of the core tye tranformer at higher frequencie and alo the advancement in the emiconductor technology uch a introduction of SiC, GaN device trongly demand the high frequency, high ower denity tranformer. Thu, the reearch i made to focu on the high frequency corele tranformer. The invetigation regarding the corele PCB tranformer rovided the ueful information that it i oible to ue them a an iolation tranformer for both ignal and energy tranfer alication [4]. Since in thee tye of tranformer, the magnetic flux i not confined, there exit a deluion of high radiated EMI but according to antenna theory, thee tranformer are not conidered a good antenna/receiver and therefore can be uitable for the energy tranfer alication [4]. In DC/DC converter for alication uch a Power over Ethernet, WLAN Acce-oint, IP hone and for a wide variety of telecom alication, a te down ower tranformer of different turn ratio i required. Two different corele PCB te down (:) multilayered tranformer were manufactured uitable for high frequency DC/DC converter. In thi aer thee tranformer erformance characteritic for ower tranfer alication have been tudied and alication otential of thee tranformer were addreed. II. STRUCTURE OF THE MULTILAYERED PCB TRANSFORMERS In thee corele PCB tranformer, the rimary and econdary coer winding of the tranformer are etched on the FR4 PCB laminate whoe breakdown voltage i of aroximately 5kV/mm [5]. In order to have better couling and for the high ower denity of the tranformer, the : tranformer are deigned in a four layered PCB. Here, there are two rimary winding (P and P) in two different layer and one econdary winding (S) in between the two rimary winding. The two rimarie P and P are connected in erie externally uing the fourth layer of the PCB. The dimenion of the two tranformer are hown in fig.. It i mentioned in [6], increaing the area of the tranformer by increaing the number of turn without changing the track earation of the conductor, the rate of increae of elf and mutual inductance are greater with reect to that of the leakage inductance. A a reult the couling coefficient of the tranformer i going to be increaed. Therefore, a erie coniting of two different tranformer of the International Scholarly and Scientific Reearch & Innovation 4() 487 cholar.waet.org/37-689/554

2 Vol:4, No:, International Science Index, Electrical and Comuter Engineering Vol:4, No:, waet.org/publication/554 Fig.. Dimenion of corele PCB Tranformer Tr (mm) and Tr (3mm) ame width, track earation and height have been deigned for the DC/DC Converter alication. The width, track earation and height of the conductor are.6mm,.4mm and 7µm reectively. The number of turn relating to the rimary and econdary winding for thee tranformer i different, while at the ame time the other geometrical arameter remain contant. The number of rimary/econdary turn of Tr and Tr are 6/8 and 4/ reectively. The outer diameter of the deigned tranformer Tr and Tr are mm and 3mm reectively and the correonding height of the tranformer i.48mm. III. HIGH FREQUENCY MODEL OF MULTILAYERED STEP DOWN PCB : TRANSFORMERS In thi ection the reitive, inductive and caacitive arameter relating to the tranformer uing high frequency equivalent circuit are reented. The erformance characteritic uch a the tranfer function H(f) and inut imedance (Z in ) of the tranformer with two different reonant caacitor Cr of.5nf and.nf at a load reitance of 47 Ω are meaured for matching the high frequency model of the tranformer. The initial arameter uch a the rimary elf inductance L, econdary elf inductance L and the reitance of the winding are meaured with the aitance of HP484A reciion LCR meter at MHz frequency by oen circuiting the ooite winding of the tranformer. The reliminary rimary and econdary leakage inductance of the tranformer are obtained by uing the four-wire meauring method [7]. The leakage inductance of the tranformer which are le than µh are obtained by () 5 Vdut Llk = () πf V 5Ω Where, L lk - Leakage Inductance f - Excitation frequency, [Hz] V dut - Voltage acro the device under tet V 5Ω - Voltage acro the 5Ω reitor The actual arameter uch a elf inductance, mutual inductance and leakage inductance of the tranformer are obtained by fitting the above meaured arameter in high frequency model of the tranformer hown in fig.. Fig.. High frequency model of corele PCB te down tranformer Here, R Primary winding reitance; R Secondary winding reitance; L lk Leakage inductance of rimary; L lk Leakage inductance of econdary; R L Load reitance; C r Reonant Caacitor; L m Primary Mutual inductance; L m Secondary Mutual inductance; L m Mutual inductance; Interwinding caacitance; C The intrawinding caacitance of both the winding are very mall and can be ignored in the analyi. The above meaured arameter at MHz frequency are aed into thi high frequency model and are fine tuned in order to match the meaured erformance characteritic over the full frequency range and hence the correct model arameter are obtained. The model arameter uch a elf, mutual, leakage inductance, interwinding caacitance of the rimary and econdary winding, and the correonding DC reitance are hown in table II. Here, the rimary /econdary mutual inductance of the tranformer i given a Lm = L Llk () Lm = L Llk (3) The mutual inductance L m between the rimary and econdary of the tranformer i the geometric mean of the rimary and econdary mutual inductance L m and L m [8] Lm = Lm* Lm (4) From Table I, it can be verified that the rate of increae of leakage inductance of rimary/econdary with reect to their correonding elf inductance i low when the area of the tranformer i increaed with the increaed number of turn a mentioned earlier. Therefore, the comarative leakage inductance to elf inductance of the tranformer Tr i lower comared to that of the tranformer Tr. The DC reitance of the tranformer are hown in the table I. International Scholarly and Scientific Reearch & Innovation 4() 488 cholar.waet.org/37-689/554

3 Vol:4, No:, TABLE I ELECTRICAL PARAMETERS OF THE DESIGNED TRANSFORMERS PARAMETERS TR TR R (Ω)-DC.6.84 current while oen circuiting the econdary winding of the tranformer Tr Tr R (Ω)-DC.3.4 L (µh) L (µh).78. L lk (µh).35.4 R AC [Ω].5.5 International Science Index, Electrical and Comuter Engineering Vol:4, No:, waet.org/publication/554 L lk(µh).9.8 L m(µh) C (F) %L lk/l (µh) %L lk /L (µh) The winding reitance of the above tranformer increae a the oerating frequency of the current increae due to kin effect. Thee AC reitance of the rimary and econdary winding of the two tranformer are calculated by uing the following exreion and by aroximating the model to a circular iral inductor [9]. R h R = DC AC δ ( ex( h / δ )) (5) Where R DC - DC reitance of the winding h - Height of the conductor δ - Skin deth The equation of the kin deth [] i given a follow δ = πfμσ (6) Here, f - Oerating frequency μ - Permeability of the medium σ - Conductivity The meaured and calculated AC reitance of the rimary winding of the two tranformer i illutrated in fig. 3. The AC reitance of the econdary winding of the tranformer follow the ame behaviour a hown in fig. 3 but i twice a low, a it conit of one winding a comared to two for the rimary. The AC reitance of the rimary are obtained by meauring the voltage, current and hae angle between the voltage and..5 5 Fig.3. Calculated (olid line) and meaured (ymbol) AC reitance of the rimary winding of the deigned tranformer Couling Coefficient: The couling coefficient i the ratio of the mutual inductance to the geometric mean of rimary and econdary elf inductance according to []: Lm K = (7) L L where, L m i the mutual inductance between the rimary and econdary winding and L /L the elf inductance of the rimary/econdary winding. The couling coefficient of tranformer Tr i.875 and for the tranformer Tr it i.93. We oberve that, the couling coefficient K enhance a the area of tranformer increae with the increae of number of turn a dicued earlier. In thee tranformer alo by lacing an external reonant caacitor the roblem of low voltage gain becaue of low couling factor can be eliminated. Thi i due to the artial reonant henomena of the leakage inductance of the tranformer and the external reonant caacitor []. Therefore, the energy efficiency of the tranformer increae and can actually be greater than the couling coefficient which alo make the mallet tranformer energy efficient and thu ueful for ower ulie. IV. PERFORMANCE CHARACTERISTICS OF THE MULTILAYERED PCB TRANSFORMERS The erformance characteritic uch a tranfer function of the corele PCB tranformer under load condition H (f), inut imedance (Z in ) and the hae angle (φ) of the tranformer determine the oerating frequency of thee tranformer. Thee exreion are obtained from the high frequency equivalent circuit of the tranformer hown in fig. 4 and are derived in [4], [6], and [] a follow: International Scholarly and Scientific Reearch & Innovation 4() 489 cholar.waet.org/37-689/554

4 Vol:4, No:, International Science Index, Electrical and Comuter Engineering Vol:4, No:, waet.org/publication/554 Fig. 4. High frequency equivalent circuit of the tranformer referred to rimary + j ( π f ) C ' Y V H ( f ) = = (8) V ny Z in = (9) V ( A) C' ( n ) + + C' V where n i the turn ratio of the tranformer R ' = n L lk ' = n R L lk n C ' = C + C n n C r ' = C r + C n n C ' = C n Y Y Y A = = R + L = R ' + L lk lk = + = + C C = ' + Y + Y Y ' + L m ' + C r ' + n R Y A. Tranfer Function H (f) of the Corele PCB Tranformer: L The tranfer function of deigned tranformer are determined by uing two different reonant caacitor. The magnitude of the tranfer function, referred to the rimary ide with reonant caacitor of.5nf and.nf at a load reitance of 47Ω, are lotted and are hown in fig. 5 and 6 reectively. From fig.5 and 6 we oberve that the meaured tranfer function of the tranformer are in good agreement with thoe calculated by uing the model equation. The tranfer function H (f) i maximum at a frequency known a maximum gain frequency of the tranformer. Theoretically the reonant frequency [] of the tranformer can be calculated by uing () where f r eq = π L lk eq m C L L '+ L L eq lk () = () C = C ' + C ' () eq r The reonant frequency of the tranformer decreae for larger value of reonant caacitor acro the econdary winding of the tranformer. For examle in fig. 5 it can be oberved that the maximum gain frequency of the tranformer Tr with C r =.5nF i cloe to 9.8MHz where a in fig.6 it i 8.MHz with C r =.nf. B. Inut Imedance (Z in ) and hae angle (φ): With an external reonant caacitor of.5nf connected acro the econdary winding of the tranformer (Tr and Tr), the meaured and the calculated inut imedance (Z in ) and hae angle (φ) are lotted in fig. 7 and 8 reectively. In thi cae the load reitance i 47Ω. From fig. 5 the maximum gain frequency of the tranformer Tr i aroximately 9.8MHz a dicued in the reviou ection. For the ame tranformer Tr, from fig. 7 it can be oberved that the inut imedance eak at 4.8MHz aroximately. Thi frequency, at which the imedance of the tranformer i maximum, i known a the Maximum Imedance Frequency (MIF). From fig. 5 and 7, the maximum imedance frequency of the tranformer i le than the maximum gain frequency. From fig. 8 it can be oberved that before MIF, the tranformer i highly inductive in nature and at MIF, the hae angle of the tranformer Tr i very mall. The oerating frequency region i the region where the tranformer oee ufficient inut imedance and alo where it i highly inductive in nature. The inut imedance of the tranformer Tr at 3MHz i reaonably high and thu the correonding oerating frequency region of thi tranformer lie aroximately in the frequency range of 3-4.8MHz. After thi frequency region, the inut imedance of the tranformer i decreaing a hown in International Scholarly and Scientific Reearch & Innovation 4() 49 cholar.waet.org/37-689/554

5 Vol:4, No:, 3.5 Tr Tr Tranfer Function, H(f) Fig. 5. Calculated (olid line) and meaured (ymbol) tranfer function H (f) of the tranformer with C r =.5nF and RL=47 Ω. International Science Index, Electrical and Comuter Engineering Vol:4, No:, waet.org/publication/554 Tranfer Function, H(f) Fig. 6. Calculated (olid line) and meaured (ymbol) tranfer function H (f) of the tranformer with C r =.nf and R L =47 Ω. fig.7 and additionally the tranformer i not inductive in nature a illutrated in fig. 8, hence we cannot oerate the tranformer after MIF. Therefore, for ower tranfer alication, MIF determine the maximum limit on the oerating frequency region of the tranformer. The ame henomenon i.e., the maximum imedance frequency, oerating frequency region i oberved for the other tranformer Tr. The inut imedance of the tranformer Tr and Tr i oberved to be increaing in nature a the number of turn of the tranformer increae becaue of the increaed inductance of the tranformer a hown in fig.7.the effect of the reonant caacitor on the inut imedance and hae angle i alo oberved by connecting a.nf reonant caacitor acro the econdary winding of the tranformer Tr and Tr and the reult are lotted in fig. 9 and reectively. From fig. 6 and 9, the maximum gain frequency and the maximum imedance frequency of the tranformer Tr are 8 and 4MHz reectively. It can be oberved that thee frequencie were hifted toward the lower oerating frequencie when the reonant caacitor value i increaed. Here, the inut Tr Tr imedance of the tranformer i ufficiently high at a frequency of.75mhz and thu, the oerating frequency region of the tranformer Tr i oberved to be in the frequency range of.75-4mhz. However, a it ha been reviouly dicued, the oerating frequency region of tranformer Tr with the reonant caacitor C r =.5nF i 3-4.8MHz. From thi we can ay that the wide oerating frequency region i obtained with the aitance of lower value of reonant caacitor. Alo, we can ay that for the given tranformer, with the hel of larger value of reonant caacitor, the otimal oerating frequency region move toward the lower frequencie wherea with the lower value of caacitor it move toward the higher oerating frequencie while maintaining the imilar characteritic curve. The ame criterion i oberved for the tranformer Tr. For SMPS alication, ince the witching loe of the ower mofet are dominant in nature, the maximum imedance frequency of the tranformer can be hifted further toward the lower oerating frequencie with the hel of reonant caacitor o that maximum energy efficiency of the converter can be International Scholarly and Scientific Reearch & Innovation 4() 49 cholar.waet.org/37-689/554

6 Vol:4, No:, 6 4 Tr Tr Z In [Ω] International Science Index, Electrical and Comuter Engineering Vol:4, No:, waet.org/publication/ Fig. 7. Calculated (olid line) and meaured (ymbol) inut imedance of tranformer with C r =.5nF and R L =47 Ω Phae angle, φ [ ] Tr -8 Tr Fig. 8. Calculated (olid line) and meaured (ymbol) hae angle of tranformer with C r =.5nF and R L =47 Ω attained at a frequency known a maximum energy efficiency frequency. From fig. 7 and 9, we can oberve that the magnitude of the inut imedance become reduced when the reonant caacitor value i increaed which alo agree with (6). C. Energy Efficiency (η): Since no magnetic core exit, there i no magnetic core lo involved in thee tranformer. The ower lo in the rimary and econdary winding of the : te down tranformer [] i given by (3). * * * * Plo = ( i i Rac ( ) + i i Rac ( ) + Rac ( ) ( i i + i i ) (3) where, i /i - RMS current through rimary/econdary winding i * /i * - Comlex conjugate RMS current through rimary/econdary winding R ac () / R ac () - Primary/econdary winding ac reitance The meaured average inut and outut ower er cycle of thee tranformer are obtained from (4) and (5) reectively. T P in = v ( t) i ( t dt T ) (4) P T out ) = v ( t) i ( t dt T (5) Where, v - Intantaneou rimary voltage acro the rimary winding v - Intantaneou econdary voltage acro the econdary winding i - Intantaneou current through the rimary winding of the tranformer International Scholarly and Scientific Reearch & Innovation 4() 49 cholar.waet.org/37-689/554

7 Vol:4, No:, 6 4 Tr Tr Z In [Ω] International Science Index, Electrical and Comuter Engineering Vol:4, No:, waet.org/publication/ Fig. 9. Calculated (olid line) and meaured (ymbol) inut imedance of tranformer with C r =.nf and R L =47 Ω Phae angle, φ [ ] Tr -8 Tr Fig.. Calculated (olid line) and meaured (ymbol) hae angle of tranformer with C r =.nf and R L =47 Ω i - Intantaneou current through the econdary winding of the tranformer T - Period of a cycle where T=/f f - Oerating frequency of the tranformer Hence, the meaured energy efficiency of the tranformer i Pout η mea = % (6) Pin V. POWER TESTS OF THE TRANSFORMERS The ower tet of the tranformer Tr and Tr are carried out with the hel of EMPOWER BBMA3FKO Radio Frequency Power Amlifier whoe frequency range i given a.mhz - 3MHz and with a ower delivering caacity of Watt. Here, the tranformer rimary winding i ubjected to the variable voltage in the frequency range of - MHz. The tye of the waveform i.e., inuoidal/quare wave and the excitation voltage fed to the ower amlifier i varied with the hel of HP33A ignal generator. The meaurement are fetched from the Tektronix ocillocoe TPS4 with the hel of Lab view 8.5. The rimary/econdary voltage of the tranformer are meaured with the hel of high voltage robe P5 and the current through the rimary/econdary winding are taken by uing Tek-CT Current tranformer. (A) Energy Efficiency of the tranformer Tr and Tr with different loaded condition The energy efficiency of the tranformer Tr with C r =.5nF i meaured for different loaded condition and i hown in fig.. With thi external reonant caacitor, the maximum imedance frequency of the tranformer i found to occur at 4.8MHz and from fig. we can oberve that the efficiency i maximum at a frequency of 4MHz for all the load. Thi mean that the maximum energy efficiency frequency of the tranformer doe not change with reect to different loaded condition. From thi we can alo oberve that the maximum energy efficiency frequency i le than maximum imedance International Scholarly and Scientific Reearch & Innovation 4() 493 cholar.waet.org/37-689/554

8 Vol:4, No:, International Science Index, Electrical and Comuter Engineering Vol:4, No:, waet.org/publication/554 frequency. The energy efficiency of the tranformer Tr i about 97% at the frequency of 4MHz with the load reitance of 5 Ω. Here, the outut ower of the tranformer i aroximately Watt and with the load current of.5am, fed with an inut voltage of 43Vrm. Under the ame voltage excitation, with the load reitance of Ω, the efficiency of the tranformer i aroximately 93.8% at an outut ower of 3Watt with the load current carrying caacity of.7am. Energy Efficiency, η[%] 9 8 RL= Ohm 7 RL=3 Ohm RL=4 Ohm RL=5 Ohm Fig.. Efficiency of the tranformer Tr with different load at C r =.5nF Similarly, the energy efficiency of the tranformer Tr with different loaded condition and with an external reonant caacitor of.5nf i illutrated in fig.. For thi tranformer, the maximum inut imedance frequency i oberved to be at.8mhz from fig (7).Hence, the maximum energy efficiency of thi tranformer can be in the range of -.8MHz. Energy Efficiency, η[%] 9 8 RL= Ohm 7 RL=3 Ohm RL=4 Ohm RL=5 Ohm Fig.. Efficiency of the tranformer Tr with different load at C r =.5nF The energy efficiency of the tranformer i aroximately 97% at load reitance of 5 Ω with a load ower of about Watt at a frequency of MHz which can be oberved from fig (). Here, the inut voltage i 4Vrm with an outut load current of.459am. At the load reitance of Ω the efficiency i aroximately 94.5% with an outut ower from the tranformer i of about Watt and with the load current of.98 Am. At thi intant the inut voltage fed to the rimary winding of the tranformer i 4Vrm. (B) Energy Efficiency of the tranformer Tr and Tr with different reonant caacitor The meaured energy efficiency of the tranformer Tr and Tr with different reonant caacitor at the reitive load of 3 Ω i illutrated in fig. 3 and 4 reectively. Energy Efficiency, η[%] Energy Efficiency, η[%] 8 6 Cr=4.7nF Cr=3.3nF 4 Cr=.nF Cr=.nF Cr=68F Fig. 3. Meaured energy efficiency of the tranformer Tr with different reonant caacitor and at RL=3Ω. 8 6 Cr=4.7nF Cr=3.3nF 4 Cr=.nF Cr=.nF Cr=68F Fig. 4. Meaured energy efficiency of the tranformer Tr with different reonant caacitor and at R L =3Ω. A the reonant caacitor value acro the econdary winding of the tranformer increae, the maximum energy efficiency frequency move toward the lower oerating frequencie which can be oberved from fig. 3 and 4.Thi i becaue their correonding maximum gain frequency and maximum imedance frequency are decreaed with the increaed value of the caacitor. Hence, with the roer election of reonant caacitor acro the tranformer, it can International Scholarly and Scientific Reearch & Innovation 4() 494 cholar.waet.org/37-689/554

9 Vol:4, No:, be oerated at the deired lower frequencie by till maintaining the high energy efficiency. (C) Energy Efficiency of the tranformer Tr and Tr with Sinuoidal and Square wave excitation For mot of the SMPS alication the inut voltage fed to the ower tranformer i of quare wave in nature. Therefore, the ower tet were carried out for both the inuoidal and quare wave excitation for thee two tranformer Tr and Tr and the energy efficiencie are hown in fig. 5. VI. APPLICATION POTENTIAL OF THE DESIGNED TRANSFORMERS The deigned two tranformer Tr and Tr are comared with exiting tranformer of coil craft in term of their dimenion for variou outut ower level of about 8, 5 and 3 Watt. For thee different alication the required inut 98 International Science Index, Electrical and Comuter Engineering Vol:4, No:, waet.org/publication/554 Energy Efficiency, η[%] Tr Square wave Excitation 9 Tr Sinuoidal Excitation Tr Square wave Excitation Tr Sinuoidal Excitation P out [Watt] Fig. 5. Efficiency of the tranformer Tr and Tr for different excitation with R L =3Ω and C r =.5nF at 4 and MHz reectively. The energy efficiency of the tranformer Trand Tr i meaured at a load reitance of 3Ω with an external reonant caacitor of.5nf and i hown in fig.5. The maximum imedance frequency of the tranformer Tr i at 4.8MHz and the energy efficiency i found to be aroximately 96% at 4MHz with the outut ower range of 4-4Watt for both the excitation. The efficiency of tranformer Tr i found to be aroximately 96.3% at the frequency of MHz for both inuoidal excitation.the efficiency of the tranformer Tr and Tr for quare wave excitation i not varied ignificantly with reect to inuoidal excitation, hence thee tranformer can be utilized well in the SMPS alication together with mofet which ha low rie and fall time in order to reduce mofet witching loe. The waveform were catured at maximum energy efficiency frequency of Tr at 4MHz are illutrated in fig.6. The load reitance conidered i of 3 Ohm and the external reonant caacitor i.5nf. Here, the RMS value of the rimary voltage, V ri, econdary voltage, V ec, rimary current, I ri and the econdary current, I ec, of corele PCB te down tranformer are illutrated. In thi cae, the load ower i aroximately.5 watt and energy efficiency i of about 96%. Fig. 6. Meaured waveform with Cr=.5nF and RL=3 Ω. CH V ri (5V/div), CH I ri (5mA/div), CH3 V ec (V/div), CH4 I ec (A/div) voltage range, outut voltage, outut current, dimenion and ercentage volume reduction of deigned tranformer are lited in table II. TABLE II EISTING CORE BASED TRANSFORMERS DIMENSIONS, PART NUMBER AND ELECTRICAL CHARACTERISTICS V in (Volt) V in (VOLTS) I out (Am) Power (Watt) Dimenion in mm & art number(coil craft) %Volume reduction of Tr, Tr x.7x 7, 37 FCT- 5LSLB x3.4x 79, 53 FCT- 5MSLB x.5x.4 9, 8 FCT- 5MSLB For the 8 Watt alication mentioned in the table II, the tranformer Tr and Tr are fed with an inut voltage of about 3Vrm and the energy efficiency of Tr and Tr are 95.7% and 96.3% reectively. Similarly, for 5 Watt alication the inut voltage alied to the tranformer i 35Vrm and the energy efficiency of thee tranformer i of about 9.4% and 93.5% reectively. For 3 Watt alication the inut voltage given to the tranformer i aroximately 56Vrm and the meaured energy efficiency of the tranformer are 93.7% and 94.8% reectively. In all the cae i.e., for 8, 5 and 3watt alication we can oberve that the energy efficiency of the International Scholarly and Scientific Reearch & Innovation 4() 495 cholar.waet.org/37-689/554

10 Vol:4, No:, International Science Index, Electrical and Comuter Engineering Vol:4, No:, waet.org/publication/554 tranformer Tr i lightly greater when comared to that of the tranformer Tr. In thi cae, even though the AC reitance of the tranformer Tr i greater than Tr, the efficiency i higher becaue of the high couling coefficient. With thee deigned multilayered corele PCB tranformer the height of the tranformer ued in converter get reduced ignificantly from mm to.48mm and in ome cae the ize of the converter can be the ize of the tranformer. Therefore, for the SMPS alication which require very tight retriction on the height of the tranformer, tranformer Tr and Tr can be utilized when comared to the exiting tranformer. VII. CONCLUSIONS In thi aer the deign, analyi and the alication otential of multilayered corele PCB : te down tranformer for DC/DC converter alication ha been reented. The tranformer rimary and econdary winding are etched on the Fr4 PCB laminate. The high couling coefficient of the tranformer i achieved by increaing the number of turn of the tranformer and alo by andwiching the econdary winding between the two rimary winding. The high frequency equivalent circuit model ha been verified for thee multilayered corele PCB te down tranformer. Thee fabricated tranformer have been teted for the outut ower level uto 3Watt and the energy efficiency i found to be within the range of 9-97% for both the tranformer. Tranformer Tr ha higher energy efficiency with reect to Tr and can be utilized for the abovementioned alication. From the obervation we can conclude that thee te down : multilayered PCB tranformer are highly energy efficient and can be ued in SMPS for ower tranfer alication in MHz region.it wa roven that the high energy efficiency of the te down tranformer i oible by increaing the te down ratio for higher ower rating and reduced voltage which wa not oible with jut two layered : tranformer [].Thi rovide the coe for further increae of te down ratio of the tranformer for different SMPS alication. ACKNOWLEDGMENT The author would like to thank VINNOVA, The Swedih Energy Agency and Euroean Union for their financial uort. REFERENCES [] Conor Quinn, Karl Rinne, Terence O Donnell, Maeve Duffy and Cian O Mathuna, A review of Planar Magnetic Technique and Technologie, IEEE APEC, [] Colonel William, T.McLyman, Tranformer and Inductor deign Handbook CRC re; 3 edition. [3] Wong, Fu Keung, High Frequency tranformer for witch mode ower ulie, Griffith Univerity, 4. [4] S.C.Tang, S.Y.R.Hui and H. Chung, Corele Printed Circuit Board (PCB) Tranformer Fundamental characteritic and alication otential, IEEE Circuit and Sytem Newletter, Vol., No. 3, Third Quarter,.,.3-5 and.47. [5] C.F.Coomb, Printed Circuit handbook 5th Edition, McGraw-Hill, Augut 7,. [6] S.C.Tang, S.Y. (Ron) Hui and Henry Shu-Hung Chung, Characterization of Corele Printed Circuit Board (PCB) Tranformer, IEEE Tranaction on Power Electronic, Vol. 5, No. 6, November, [7] Alex Van den Boche and Vencilav Cekov Valchev, Inductor and Tranformer for Power Electronic t Edition, CRC Pre, March4, 5. [8] Sun-Min Hwang and Tae-Young Ahn, A ZVS forward DC-DC Converter Uing Corele PCB Tranformer and Inductor,. [9] Heng-Ming Hu, Effective erie-reitance model of iral inductor, Microwave and Otical technology letter, vol.46, No., July, [] Robert W.Erickon, Fundamental of Power Electronic nd Edition, Sringer International Edition,.55. [] S.C.Tang, S.Y.(Ron)Hui and Henry Shu-Hung Chung, Corele lanar Printed-Circuit-Board (PCB) Tranformer-A Fundamental Concet for Signal and Energy Tranfer, IEEE Tranaction on Power Electronic, vol 5, No.5, Setember, [] JAMES H.SPREEN, Electrical Terminal Rereentation of Conductor Lo in Tranformer, IEEE Tranaction on Power Electronic, vol 5, No.4, October 99. International Scholarly and Scientific Reearch & Innovation 4() 496 cholar.waet.org/37-689/554