1. Magnetic Problems
Magnetics Group
DPEC

2. Consideration of Core Material Selection
1.如何正確建議工程師使用鐵心?
Material performance factor f*B △ T P cv
core material fs Pc
N49
N97
Pcv=100(kwm3)
Pcv=300(kwm3)
Pcv=500(kwm3)
EPCOS
T=100 ℃
Pcv=100(kw/m3)
Pcv=300(kw/m3)
Pcv=500(kw/m3)
1000 3
C96
F35 F4
Pcv=100 kw/m3
Pcv=300 kw/m3
Pcv=500 kw/m3
T=100 
Ferroxcube
3C96
3F35
3F4 ℃
2000
1000
f*B vs. frequency

3. High Frequency Ferrite Material Class
2. 設計頻率200 KHZ~500KHZ,應如何選擇適用的的鐵芯材質.
High Frequency Ferrite Material Class
100kHz~300kHz-----3C94,PC40,3C96,PC44,PC47….
300kHz~500kHz----3F3,P5,2M,MBF4,BH5….
500kHz~1MHz F35,N49,MC2,PC50,BH40….
1MHz~2MHz F4,3F45,N59,7H20…..
2MHz~4MHz F5
4MHz~10MHz F1,F2(NiZn)

4. 300kHz~500kHz Material Comparison

5. 3.ADP在使用Half Bridge Circuit設計變壓器時,使用3C96鐵心材質會有
好的溫度表現；使用FlyBack Circuit則使用2HM5會有較好的溫度表現。
3C96
Bs = 0.37T
2HM5
Bs = 0.41T
ADP-150BP (AHB)
Bac = 112mT
ADP-75HB (Flyback)
Bac = 103mT
Bdc = 230mT
Bm = 333mT

6. LLC integrated magnetics core
4.如何有效利用鐵心(鐵心開模的建議)
LLC integrated magnetics core
Original design
Uneven flux
Optimal design
Even flux

7. Modified PJ core
Even flux
Winding consideration (winding space, terminal)

8. How to Calculate Gap Length?
Challenges in gapped inductance calculation
Inductance
with gap
Gap length
Gap location
Winding location
Frequency
Core area
Core length
Window size
Many inaccurate formula!
A lot of time spending!
More accurate formula
Error comparison of the Equations
-40
-20 20 40 60
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Air gap (mm)
Error (%)
Measured
Our Eq.
Other equations

9. Calculation tool interface
Suitable cases
EE core
EI core
Winding near gap
Winding far from gap
Calculation tool interface

10. Core and Circuit Type Selection
在多少瓦特數時 (FLYBACK 、FORWARD 、FULL BRIDGE、
HALF BRIDGE等) ，如何選用何種TYPE形式最有效益。
Characteristics of converters
Common used core shape
Flyback: High output current ripple
Po<150W
Poor cross regulation
High Bm (Bac + Bdc)
High turns number
PJ, RM core
PJ, RM: large Ae, good EMI
EE, ETD: large Aw, good heat emission,
poor EMI
PQ: large Ae, good EMI, poor terminal
Forward: low voltage, high current
and high power application
Half bridge: high input voltage application
Full bridge: high power application
EE, ER,ETD, PQ core

11. Safety Problem of Transformer
家電類POWER SUPPLY需作PLD測試, (6.6KVac,500A),對X‘FMR會有什麼影響?
Good insulation!
Good withstand voltage capability!

12. EMI Problem 1.變壓器正繞、反繞及腳位互換時,對於ADP的影響(EMI、特性.…等)?
Vin D S N1 N2 C Vo + -
Jumped voltage point
Constant voltage point
Jumped voltage point:
most inside the bobbin
Constant voltage point:
far away from the jumped voltage point
Test result of 75W adaptor
Jumped point
EMI/dBuV 70 60 50 40 20 10
-10
100k M
EMI/dBuV 70 60 50 40 20 10
-10
100k M P2 S P1 P2 S P1
Jumped point
Original design
Optimal design

13. 2.變壓器的EMI 、NOISE過大時該如何改善…?
C1: Switch to Heatsink
C2: Heatsink to Ground
C3: Secondary to Ground
CPS: Transformer Parasitic Capacitance
If heatsink is connected to the minus, C1, C2  0.
CPS<<C3, CP  CPS.
Cps is a key parameter to be minimum.
Add shielding: decrease Cps
Jumped voltage point: most inside the bobbin
Constant voltage point: far away from the jumped voltage point
Filter component: far away from transformer

14. 3. DIFFER&COMMON CHOKE對於EMI,RFI的抑制,基本設計關係式?(CORE TYPE)
CM choke as an example
Filter
Power
supply
CM choke L C
LISN
25ohm Vd
LISN
50ohm
With filter: VLISN = Vs
Without filter: VLISN = Vs’
IL = 20lg(Vs/Vs’)
Characteristics of filter
Vs’ < EMI limit L
EMI filter design tool developed by DPEC can help engineers to design filter easily.

15. 4.雜散電容的定義與測試方法?
C1: Switch to Heatsink
C2: Heatsink to Ground
C3: Secondary to Ground
CPS: Transformer Parasitic Capacitance
Cps is a key parameter to be minimum.
The impedance analyzer can not be used to measure the Cps because of the transformer
shielding and non-constant voltage distribution along the primary winding turns.

16. Cps Test Device Step1: Getting the C-EMI curve
Shielding
Shielding
Step1: Getting the C-EMI curve
Step2: Getting the Cps with interpolation

17. ADP-10UB Thailand transformer TP – EMI passed TF – EMI failed
Taiwan transformers are
similar to the yellow curves.
Cps is a key factor for EMI level
Cps can be tested by our fixture

18. Magnetics Design Problem

19. For copper foil 1D Dowell Model For solid wire
1.Design tools中也有AC WINDING LOSS的分析程式, 是否
可告訴我們原計算公式為何?有哪些是必要的影響參數?
For copper foil
1D Dowell Model
Wcu
For solid wire
Key parameters:
f, D, Wcu, structure (H), current waveform
same area
same Rdc (change )

20. 2. Design tools是否可加入漏感的計算及告知我們影響參數有哪些?
Leakage calculation by out tool
Effect factor
From a circuit point of view, the energy storage
capability of the magnetic field between the
windings is called leakage inductance.
Leakage
Energy = H
Simple, sandwich B
Air, low u core P S
Low u core
Space between windings

21. 3.當X’FMR GAP過大時,圈數比的測量將會失真,Design tools Lk N2 N1 Lm im V1 V2 Lp Ls
If Ls is low enough
If Ls is relative high
If Lk<<Ls, the effect of Lk can be neglected.
If gap is high, Lm will be low, and then the
Lk can’t be neglected compared with the Lm.
Open Lp, measure Ls
Short Ls, measure Lk

22. 4. Design tools是否可加入LLC線路的設計?
Design parameter: Vin-min, Vin-max, Vin-nor, Vo, Io, fo, fmin, Vc-max
1. Transformer effect turn ratio, n
5. Coupling coefficient, k
2. Resonant capacitance, Cs
6. Secondary inductance, L2
7. Transformer physical turn ratio, na
3. Resonant inductance, Ls
4. Transformer magnetizing inductance, Lm
8. Highest operating frequency, fmax

23. Model of Tr with Ls Measure method: Simulation method: i i iLk Lm
n:1
Effect turn ratio
Np:Ns
Physical turn ratio
Common used model
Convenient for circuit analysis model
Measure method:
Simulation method: L1 i
Lk = Lpsshort
Lm = Lp – Lk
n = (Lm/Ls)1/2 i L1 L2 U1 Lp
Lpsshort: short circuit inductance
Lp: primary self inductance
Ls: secondary self inductance i L1 L2 U2 Ln
Lk = (1-k2)*L1
Lm = L1 - Lk
n = (Lm/L2)1/2
L1, L2, M (k)

24. DC gain of output to input voltageCs Ls Lm
n2R
nVo D1 D2 Vo
Different requirements (low profile, low cost, low loss…) need various LLC magnetics design.

25. LLC magnetics design for low cost requirement
Challeges of LLC magnetics:
Many magnetic components (Tr, Ls)
High AC component for Ls
High winding loss x r h P S h Lk Lm h
n (P:S)
Adjust gap position
to obtain certain
circuit performance
Influence of gap position on magnetic parameters

26. 5.Design tools是否可加入INVERTER X’FMR及低頻(60Hz)變壓器的設計?
Vin C 1 N Cs Cp
Rlamp Vi
Basic schematic diagram of the backlight inverter
Backlight inverter for a 14’’ notebook as an example
220mm long CCFL
Ignition voltage of 1400Vrms
Lamp voltage and current in burning state: 600Vrms and 5mA
C: DC blocking capacitor
Cp: Lamp’s parasitic capacitor ( 15pF for 14’’ lamp )
Cs: Ballast capacitor, normal start with 47pF

27. components to secondary
Inverter Transformer Design
Circuit analysis
Ls1 Lm
Vin
1:N
Ls2
Vsec Cs Cp
Rlamp Vs
( k: coupling factor, 0.4~0.7 )
Transfer primary
components to secondary L Cs Cp
Rlamp Vs
Vsec
L, Lsec
N,Lpri
Before ignition L C Vs
Vsec
( fo = 55kHz )

28. Transfer function Burning state: Ignition state: Ignition frequency
Burning frequency

29. Turns number of primary and secondary
Core and winding loss
Core material: 3C91
(minimum loss around 50 degree)
Winding design based on
winding space in the bobbin
Temperature rise
( for frame&bar T)

30. The end !
Thanks !