PSMA/APEC 2019

Series-Coupling Test Characterization of High-Leakage Transformers

(Originally presented at APEC 2007)

Presenter: John G. Hayes

Power Electronics Research LaboratoriesUniversity College Cork, Ireland

PSMA/APEC 2019

Objectives

Present three types of high-leakage transformers.

Poor performance of open-circuit and short-circuit tests.

Develop series-coupling tests to accurately extract resistive and inductive elements of transformer.

Validate with FEA for prototypes.

Inductive Charging for EVs

PSMA/APEC 2019

Coupler

TranformerInlet

Cores

puck

Primary

Secondary

(a) (b)

PSMA/APEC 2019

PWB-Integrated Transformer

6 layer PWBWindings on the four inner layersPermalloy on the two outer layers

Permalloy (80/20 nickel iron alloy)

-

PSMA/APEC 2019

On-Chip Silicon-Integrated Transformer

Transformer deposited onto silicon wafer 10 µm thick nickel-iron alloy Race-track shaped copper winding Electroplated copper 4 or 6 turn primary45 µm wide

1 turn secondary 105 µm wide

Very high-impedance wirebonds

PSMA/APEC 2019

Transformer Equiv. Cct

Low magnetizing inductance High leakage inductances High copper and core resistances

Llp LlsRwp Rws

Lmp

Rcp

1:n

PSMA/APEC 2019

Characterization Tests: Short Circuit

( ) ( ) ( )ωp SS p SS p SSZ R j L= +( ) ( ) ( )ωp SS p SS p SSZ R j L= +( ) ( ) ( )ωp SS p SS p SSZ R j L= +( ) ( ) ( )ωp SS p SS p SSZ R j L= +

( )

2 22 2 2

2 4 2 4

2 22

2 2

where

ws ws ws lscp cp mp cp

wpp SSws ls

cp mp

R R R LR R L Rn n n n

R RR LR Ln n

+ + ω +

= + + +ω +

( ) ( ) ( )Short-circuit Impedance : ωp SS p SS p SSZ R j L= +

Complex equations, dependent on flux level.Can be simplified for well-coupled transformers.Distorted results due to parasitics and wirebonds.

PSMA/APEC 2019

Open & Short Cct Tests Results for Silicon-Integrated

Transformer:

Poor performance by open and short-circuit tests.* Negative – distorted results due to secondary wire bond impedances.

Rwp Llp Rcp Lmp Rws Lls

(Ω) (nH) (Ω) (nH) (Ω) (nH)

FEA Average 0.560 13 0.297 418 0.057 6

Exp Std(2 test) 0.461 134 0.333 266 -0.135* -4*

PSMA/APEC 2019

Series Coupling Tests:Back EMFs

( ) ( ) ( ) ( ) ( ) ( ) ( )p sp wp cp p cp s lp mp mpdi t di t

v t R R i t nR i t L L n Ldt dt

= + − + + −

( ) ( ) ( ) ( ) ( ) ( ) ( )2 2 pss ws cp s cp p ls mp mpdi tdi t

v t R n R i t nR i t L n L nLdt dt

=− + + − + +

Llp LlsRwp Rws

Lmp

Rcp

1:n

( )pv t ( )sv t

( )pi t ( )si t

PSMA/APEC 2019

Differential Coupling - ILlp LlsRwp RwsM

1:n

vp(t)

+

-

vs(t)

+

-

is(t)ip(t)

Rcp(1-n)2

vdif (t), Zdif

+

-

idif (t)

( ) ( ) ( )

( ) ( ) ( ) ( )( )2 21 1

dif p s

difwp ws cp dif lp ls mp p OS

v t v t v t

di tR R n R i t L L n L L

dt

= −

= + + − + + + −

PSMA/APEC 2019

Differential Coupling - IILlp LlsRwp Rws

Zdif

Rcp(1-n)2 Lmp(1-n)

2

( )( ) ( )( )2 21 ω 1dif dif dif

wp ws cp lp ls mp

Z R j L

R R n R j L L n L

ω= +

= + + − + + + −

Series elements only – addresses wire bond problem

PSMA/APEC 2019

Cummulative CouplingLlp LlsRwp RwsM

1:n

vp(t)

+

-

vs(t)

+

-

is(t)ip(t)

Rc(cum)

vcum(t),Zcum

+

-

icum(t)

Llp LlsRwp RwsRc(cum)

Zcum

Lm(cum)

(a)

(b)

( )( ) ( )( )2 21 ω 1cum cum

wp ws cp lp ls mp

R j L

R R n R j L L n L

ω= +

= + + + + + + +

PSMA/APEC 2019

Series-coupling Test Currents

( )

( )( )

( )( ) ( ) dif cumm dif m cummp p OS ms s OP

mp c s c p s c p s c

L I L IL I L IB

N A N A N N A N N A= = = =

− +

( ) ( )( ) ( ) 1 1p OS s OP dif cumI I n I n I n⇒ = = − = +

Uniform magnetizing flux and resultant core loss

PSMA/APEC 2019

Test Currents and Measurements

Test Resistance Inductance Current

Zp(OS) ( )p OS wp cpR R R= + ( )p OS lp mpL L L= + I

Zs(OP) 2

( )s OP ws cpR R R n= + ⋅ 2

( )s OP ls mpL L L n= + ⋅ In

Zdif ( )21dif wp ws cpR R R n R= + + − ( )21dif lp ls mpL L L n L= + + − ( )1

In−

Zcum ( )21cum wp ws cpR R R n R= + + + ( )21cum lp ls mpL L L n L= + + + ( )1

In+

Test

Resistance

Inductance

Current

Zp(OS)

()

pOSwpcp

RRR

=+

()

pOSlpmp

LLL

=+

I

Zs(OP)

2

()

sOPwscp

RRRn

=+×

2

()

sOPlsmp

LLLn

=+×

I

n

Zdif

(

)

2

1

difwpwscp

RRRnR

=++-

(

)

2

1

diflplsmp

LLLnL

=++-

(

)

1

I

n

-

Zcum

(

)

2

1

cumwpwscp

RRRnR

=+++

(

)

2

1

cumlplsmp

LLLnL

=+++

(

)

1

I

n

+

_1232860632.unknown

_1232860747.unknown

_1232860748.unknown

_1232860655.unknown

_1232860745.unknown

_1232860746.unknown

_1232860744.unknown

_1232860644.unknown

_1232804076.unknown

_1232804091.unknown

_1232804061.unknown

_1232804047.unknown

PSMA/APEC 2019

Core-loss Resistance and Magnetizing Inductance Formulae

Test Resistance Inductance

Differential ( ) ( )2p OS s OP dif

cp

R R RR

n+ −

= ( ) ( )2

p OS s OP difmp

L L LL

n+ −

=

Cumulative ( ) ( )2cum p OS s OP

cp

R R RR

n− −

= ( ) ( )2

cum p OS s OPmp

L L LL

n− −

=

Average 4

cum difcp

R RR

n−

= 4

cum difmp

L LL

n−

=

Test

Resistance

Inductance

Differential

()()

2

pOSsOPdif

cp

RRR

R

n

+-

=

()()

2

pOSsOPdif

mp

LLL

L

n

+-

=

Cumulative

()()

2

cumpOSsOP

cp

RRR

R

n

--

=

()()

2

cumpOSsOP

mp

LLL

L

n

--

=

Average

4

cumdif

cp

RR

R

n

-

=

4

cumdif

mp

LL

L

n

-

=

_1232861290.unknown

_1232861291.unknown

_1232861288.unknown

_1232861289.unknown

_1232861287.unknown

_1232861286.unknown

PSMA/APEC 2019

Test measurements for silicon-integrated transformer at 1 MHz

including wire bonds.

Zp(OS) Zp(SS) Zs(OP) Zs(SP) Zcum Zdif

I (mA) 5.03 20.5 20 19.9 4.01 6.6

R (Ω) 0.970 1.273 0.215 0.242 1.318 1.088

L (nH) 413 294 48 26 658 283

PSMA/APEC 2019

Simulation results and hysteresis loss calculation excluding wire bonds.

Zp(OS) Zs(OP) Zcum Zdif

I (mA) 5.03 20 4.01 6.6

L (nH) - FEA 431 32 675 257

R (Ω) - FEA 0.604 0.060 0.684 0.644

R (Ω) - hysteresis 0.253 0.016 0.396 0.143

R (Ω) - total 0.857 0.076 1.080 0.787

PSMA/APEC 2019

Parameter values for silicon-integrated transformer.

Rwp Llp Rcp Lmp Rws Lls

(Ω) (nH) (Ω) (nH) (Ω) (nH)

FEA Cumulative 0.562 7 0.295 424 0.057 6FEA Differential 0.558 19 0.299 412 0.057 6FEA Average 0.560 13 0.297 418 0.057 6Exp Std(2 test) 0.461 134 0.333 266 -0.135* -4*Exp-SC Cumulative 0.529 6 0.266 394 0.023 10Exp-SC Differential 0.601 44 0.194 356 0.028 13Exp-SC Average 0.565 25 0.230 375 0.026 12

PSMA/APEC 2019

Summary/Conclusions

Developed series-coupling tests to characterize high-leakage transformers.

Series-coupling tests performed well for characterizing loosely-coupled devices.

Far better performance of series-coupling tests compared to standard open and short-cct tests.

Caveats: Pay attention to flux levels and external cabling.

Series-Coupling Test Characterization of High-Leakage Transformers�(Originally presented at APEC 2007)ObjectivesInductive Charging for EVsPWB-Integrated TransformerOn-Chip Silicon-Integrated Transformer Transformer Equiv. CctCharacterization Tests: �Short CircuitOpen & Short Cct Tests Results for Silicon-Integrated Transformer:Series Coupling Tests:�Back EMFsDifferential Coupling - IDifferential Coupling - IICummulative CouplingSeries-coupling Test CurrentsTest Currents and Measurements Core-loss Resistance and Magnetizing Inductance FormulaeTest measurements for silicon-integrated transformer at 1 MHz including wire bonds.Simulation results and hysteresis loss calculation excluding wire bonds. Parameter values for silicon-integrated transformer.Summary/Conclusions