Simple Model of Transformer using LTspice

Saturable transformer modelSimplified SPICE Behavioral Model

Bee Technologies Inc.

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Contents1. Model Overview

2. Concept of the Model

3. Parameter Settings of Saturable Core

4. Saturable core SUBCKT using LTspiceIV <<-- Netlist is not open(If you buy this model , you can show netlist)

5. Saturable Core Parameter Setting (Example) 5.1 Curve fitting: RLOSS5.2 Curve fitting: LM5.3 Curve fitting: BEXP

6. Dynamic Magnetizing Curves Characteristics

7. Basic Ideal Transformers and Their Parameters7.1 Parameter settings of 1:1 ideal transformer 7.2 Parameter settings of 2:1 ideal transformer 7.3 Parameter settings of 1:2 ideal transformer

8. Saturable transformer SUBCKT Using LTspiceIV <<-- Netlist is not open(If you buy this model , you can show netlist)

9. 1:1 Saturable transformer model (Example)

10. 1:1 Saturable transformer model (Example) (Phase reverse)

11. 2:1 Saturable transformer model (Example)

12. 1:2 Saturable transformer model (Example)

13. 1:2 Saturable transformer model (Example) (Center tap)

14. Application Circuit Example: Flyback converter

Library Files and Symbol Files Location

Library Files Index

Simulation Index

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V(H)

-1.0KV 0V 1.0KVV(U1:B)

-600mV

0V

600mV

• This Saturable Transformer Simplified SPICE Behavioral Model is for users who require the model of the core loss and hysteresis as a part of their system.

• The model focuses on the hysteresis loop behavior in their operation area, which user can shape the B-H curve.

1) Model Overview

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Saturation Flux Density BS

H (A-turns/m)

B (Teslas)

Coercive Field HC

Remanent Flux Density Br

Saturation Field HS

Figure 1, Hysteresis Loop and Magnetic Properties.

Ideal TransformerSimplified SPICE Behavioral Model

[Model parameters: N, RP, RS and LP]

2) Concept of the Model

• The Saturable core is characterized by parameters: BSAT, RLOSS, LM and BEXP, which represent the Flux density vs. Magnetic field characteristics of the Saturable core.

• The Ideal transformer is characterized by parameters: N, RP, RS and LP .

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Saturable CoreSimplified SPICE Behavioral Model

[Model parameters: BSAT, RLOSS, LM and BEXP]

3) Parameter Settings of Saturable Core

BSAT The saturation flux density (in teslas). – e.g. 100mT, 350mT, 500mT– Value = <BSAT>

RLOSS The resistor RLOSS represents a loss when a voltage is applied.

– e.g. 0.5Ω, 1Ω, 100KΩ– Value = <RLOSS>

LM Magnetizing inductance of the core inductor (in henry).

– e.g. 1uH, 5uH, 50uH– Value = <LM>

BEXP The exponent in the expression for coupling factor KC.

– e.g. 2, 4, 8– Value = <BEXP>

• From the Saturable Core specification, the model is characterized by setting parameter BSAT, then adjust the parameters RLOSS, LM and BEXP to shape the dynamic magnetic curve.

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Model Parameters:

B-H Curve test pointsB-H Curve test points

Figure 2, Saturable core model (Default parameters).

4) Saturable core SUBCKT using LTspiceIV

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Figure 3, Saturable core subcircuit SPICE compatible,the key parameters are shown in bold.

Information of Netlist

5) Saturable Core Parameter Setting (Example)

Material: NC-2H

Manganese Zinc Ferrite Cores with• BS = 500(mT)• Br = 140(mT)• HC = 15.9(A/m)

Conditions:• F = 10(KHz)• TC = 23(C)

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Figure 4, Dynamic Magnetization Curves.

Specification

The data is provided in the datasheet

Input the parameter

BSAT=500m

Input the parameter

BSAT=500m

5.1) Curve fitting: RLOSS

• Condition: F=10KHz, Vin=80VP

• Parametric sweep: RLOSS=0.5Ω, 1Ω, 100KΩ

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0.5Ω ---1Ω ---100KΩ ---

Figure 5, The magnetizing line difference, RLOSS.

H (A-turns/m)

B (Teslas)

5.2) Curve fitting: LM

• Condition: F=10KHz, Vin=80VP

• Parametric sweep: LM=1uH, 5uH, 50uH

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1uH ---5uH ---50uH ---

Figure 6, The magnetizing line difference, LM .

H (A-turns/m)

B (Teslas)

5.3) Curve fitting: BEXP

• Condition: F=10KHz, Vin=80VP

• Parametric sweep: BEXP=2, 4, 8

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2 ---4 ---8 ---

Figure 7, The magnetizing line difference, BEXP.

H (A-turns/m)

B (Teslas)

6) Dynamic Magnetizing Curves Characteristics

- Evaluation Circuit and Setting

Sine wave excitation Square wave excitation

Condition: F=10KHz, Vin=80VP, TC=23°C

.tran 0 200u 100u 10n

.lib score.sub

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6) Dynamic Magnetizing Curves Characteristics- Simulation Result

• The saturable core model is completed with both sine and square wave (above) excitation as shown in these LTspiceIV simulations.

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Figure 8, Sine wave excitation Figure 9, Square wave excitation

7) Basic Ideal Transformers and Their Parameters

• The relationship between the Voltage and current are defined as equations

below.

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Figure 10, Symbol of basic ideal transformer with The voltage to current relationships.

NP NS

IP IS

VP VS

1 : N

+

-

+

-

NVV PS (7.2)

(7.3)NII SP

VP is the primary voltage.

VS is the secondary voltage.

IP is the primary current.

IS is the secondary current.

NP is the turns number of primary winding.

NS is the turns number of secondary winding.

P

S

N

NN (7.1)

N is the turns ratio of Ideal transformer (above).

7.1) Parameter settings of 1:1 ideal transformer

LP Inductance of primary winding (in henry). – e.g. 100uH, 250uH, 500uH– Value = <LP>

N is the turns ratio of Ideal transformer. – e.g. 0.1, 0.5, 1– Value = <N>

RP A series resistance of primary winding (in ohm).– e.g. 1mΩ, 10mΩ, 100mΩ– Value = <RP>

RS A series resistance of secondary winding (in ohm).– e.g. 1mΩ, 10mΩ, 100mΩ– Value = <RS>

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Model Parameters:

Figure 11, 1:1 Ideal transformer (Default parameters).

Figure 12, 1:1 Phase reverse ideal transformer (Default parameters).

7.2) Parameter settings of 2:1 ideal transformer

LP Inductance of primary winding (in henry). – e.g. 100uH, 250uH, 500uH– Value = <LP>

N is the turns ratio of Ideal transformer. – e.g. 0.1, 0.5, 1– Value = <N>

RP1 A series resistance of primary winding 1 (in ohm).– e.g. 1mΩ, 10mΩ, 100mΩ– Value = <RP1>

RP2 A series resistance of primary winding 2 (in ohm).– e.g. 1mΩ, 10mΩ, 100mΩ– Value = <RP2>

RS A series resistance of secondary winding (in ohm).– e.g. 1mΩ, 10mΩ, 100mΩ– Value = <RS>

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Model Parameters:

Figure 13, 2:1 Ideal transformer (Default parameters).

7.3) Parameter settings of 1:2 ideal transformer

LP Inductance of primary winding (in henry). – e.g. 100uH, 250uH, 500uH– Value = <LP>

N is the turns ratio of Ideal transformer. – e.g. 0.1, 0.5, 1– Value = <N>

RP A series resistance of primary winding (in ohm).– e.g. 1mΩ, 10mΩ, 100mΩ– Value = <RP>

RS1 A series resistance of secondary winding 1 (in ohm).– e.g. 1mΩ, 10mΩ, 100mΩ– Value = <RS1>

RS2 A series resistance of secondary winding 2 (in ohm).– e.g. 1mΩ, 10mΩ, 100mΩ– Value = <RS2>

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Model Parameters:

Figure 14, 1:2 Ideal transformer (Default parameters).

Figure 15, 1:2 Center tap ideal transformer (Default parameters).

8) Saturable transformer SUBCKT Using LTspiceIV

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Figure 17, Saturable transformer equivalent circuit.

Figure 16, Saturable transformer symbol, the key parameters are shown in bold.

Information of Netlist

Condition: F=10KHz, VIN=50VP, VOUT=5VP, ROUT=10Ω.tran 0 2500u 0 50n.lib tfmr1.sub

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Saturable transformer modelSaturable transformer model

Primary currentPrimary current Output VoltageOutput Voltage

9) 1:1 Saturable transformer model (Example)- Simulation Circuit and Setting

1 : N

Secondary currentSecondary current

9) 1:1 Saturable transformer model (Example) - Simulation Result

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Input voltage

Output voltage

Input Current

Output Current

Figure 18, The Input–Output Characteristics of 1:1 Saturable transformer.

Condition: F=10KHz, VIN=50VP, VOUT=5VP, ROUT=10Ω.tran 0 2500u 0 50n.lib tfmr1_rev.sub

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10) 1:1 Saturable transformer model (Example) - Simulation Circuit and Setting (Phase reverse)

1 : N

10) 1:1 Saturable transformer model (Example)

- Simulation Result (Phase reverse)

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Figure 19, The Input–Output Characteristics of 1:1 Saturable transformer (Phase reverse).

Input voltage

Output voltage

Input Current

Output Current

Condition: F=10KHz, VIN=25VP, VOUT=5VP, ROUT=10Ω.tran 0 2500u 0 50n.lib tfmr2prim.sub

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11) 2:1 Saturable transformer model (Example) - Simulation Circuit and Setting

1 : N

11) 2:1 Saturable transformer model (Example)

- Simulation Result

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Figure 20, The Input–Output Characteristics of 2:1 Saturable transformer.

Input voltage 1

Input Current 1

Output voltage

Output Current

Input voltage 2

Input Current 2

Condition: F=10KHz, VIN=50VP, VOUT1=VOUT2=5VP, ROUT=10Ω.tran 0 2500u 0 50n.lib tfmr2.sub

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12) 1:2 Saturable transformer model (Example) - Simulation Circuit and Setting

1 : N

12) 1:2 Saturable transformer model (Example)- Simulation Result

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Input voltage

Output voltage 1

Input Current

Output Current 1

Figure 21, The Input–Output Characteristics of 1:2 Saturable transformer.

Output voltage 2

Output Current 2

Condition: F=10KHz, VIN=50VP, VOUT1=VOUT2=5VP, ROUT=10Ω.tran 0 2500u 0 50n.lib tfmr2_ct.sub

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13) 1:2 Saturable transformer model (Example) - Simulation Circuit and Setting (Center tap)

1 : N

13) 1:2 Saturable transformer model (Example)

- Simulation Result (Center tap)

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Figure 22, The Input–Output Characteristics of 1:2 Saturable transformer (Center tap).

Input voltage

Output voltage 1

Input Current

Output Current 1

Output voltage 2

Output Current 2

Condition: F=40KHz, VIN=24V, VOUT=5V, RL=5Ω, CL=200uF, LP=500uH.tran 0 10m 0 100n startup.lib tfmr1_rev.sub

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1 : N

14) Application Circuit Example: Flyback converter- Simulation Circuit and Setting

14) Application Circuit Example: Flyback converter- Simulation Result

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Secondary voltage of transformer

Output voltage= 5Vdc

Figure 23, Flyback converter with Saturable transformer model.

Output ripple voltage

Secondary current of transformer

VRIPPLE

Input voltage= 24Vdc

Library Files and Symbol Files Location

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…\Simulations

C:\Program Files\LTC\LTspiceIV\lib\sub

C:\Program Files\LTC\LTspiceIV\lib\sym

Copy/Paste into

Copy/Paste into

Copy/Paste into

Copy/Paste into

1. Copy the library files (.lib) from the folder …\Simulations \.lib\, then paste into the folder C:\Program

Files\LTC\LTspiceIV\lib\sub

2. Copy the symbol files(.asy) from the folder …\Simulations \.asy\, then paste into the folder C:\

Program Files\LTC\LTspiceIV\lib\sym

Library Files Index

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Model Library Symbol

1. Saturable Core…….......................................................

2. 1:1 Saturable transformer model…………………..........

3. 1:1 Saturable transformer model (Phase reverse)…….

4. 2:1 Saturable transformer model..…………….…………

5. 1:2 Saturable transformer model..…….…………………

6. 1:2 Saturable transformer model (Center tap)…….......

score.sub

tfmr1.sub

tfmr1_rev.sub

tfmr2prim.sub

tfmr2.sub

tfmr2_ct.sub

SCORE.asy

TFMR1.asy

TFMR1_REV.asy

TFMR2PRIM.asy

TFMR2.asy

TFMR2_CT.asy

Simulation Index

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Simulations Folder name

1. Curve fitting: RLOSS…………………………………………........

2. Curve fitting: LM………………………………………………........

3. Curve fitting: BEXP…………………………………………………

4. Dynamic Magnetizing Curves Characteristics……....................

5. 1:1 Saturable transformer model (Example)……………………..

6. 1:1 Saturable transformer model (Example) (Phase reverse)…

7. 2:1 Saturable transformer model (Example)..…………….……..

8. 1:2 Saturable transformer model (Example)..…….……………..

9. 1:2 Saturable transformer model (Example) (Center tap)……...

10. Application Circuit Example: Flyback converter………………....

Curve fitting

Curve fitting

Curve fitting

Sat_Core

Sat_Trans1

Sat_Trans2

Sat_Trans3

Sat_Trans4

Sat_Trans5

Appl