Key Points in Simulation-based Conductive Noise...

© 2011 ANSYS, Inc. November 20, 2014

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Key Points in Simulation-based Conductive Noise Analysis


2

Overview and Applications

The Importance of Frequency in Circuits

EMI/EMC Overview

Simulation Requirements

Tips and Tricks

Further Materials

Outline


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Different Perspectives of EM


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EMI/EMC considers the emission/susceptibility of electronics to often unwanted signals.

Conducted emissions exist within electrically-connected systems, and can be investigated with a circuit tool.

Magnetically and Electrically coupled emissions can also be simulated with quasistatic analyses to determine the coupling due to spatial proximity.

Electromagnetic radiation occurs when the electrical conductors are efficient radiators (an appreciable fraction of the electrical wavelength), and this can be evaluated through simulation as well.

This document focuses on conducted EMC, but explains the integration of all types as well.

Overview of EMI/EMC


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Power Electronics, including switching noise in SMPS, PWM power converters, inverters, rectifiers, drives.

Cables in power equipment. Including Frequency-Dependence and Distributed wave behavior.

Automotive electronics. Bus bars, ground-plane modeling, cables, sensors.

Electric Machines and Drives.

Applications


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This is a “low-frequency” EMI solution from DC to ~100MHz.

The switching frequency may be from 10Hz to ~100kHz.

Sometimes we may need several time-steps per rise/fall, and the transient simulation requires higher-frequency data (from measurement or simulation).

If all components are characterized across the frequency, then the results will also be valid across freq.

Which Frequencies are of Interest?

Trap_WavePWIDTH=1e-005TRISE=0.1usTFALL=0.1usTPERIO=5e-005

0 20 40 60 80 100Time [us]

0.00

0.25

0.50

0.75

1.00

Tra

p_W

ave.V

AL

Simplorer1Trapezoidal Waveform

0 10 20 30 40 50Spectrum [MHz]

-140

-115

-90

-65

-40

-15

0

dB

(Tra

p_W

ave.V

AL)

Simplorer1Trapezoidal Frequency Spectrum

fswitch = 20kHz


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The time-step used in the transient circuit simulation is dictated by the dynamics of the circuit/system.

For results up to 30MHz (CISPR upper limit), then you will want time-step at <=15ns.

Whatever time-step (hmin) is used, you should provide frequency-dependent component data above 2/(hmin).

Time-steps >= 2/Fmax

Fresults 30MHz

Fswitching ?

DC 0Hz

2/hmin ~120MHz

Fcomponent-Max ~120-300MHz


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Simplorer simulations for power electronics are nonlinear and require lots of switching.

The dynamic response of the system is determined by accurate frequency-dependent modeling of all significant sub-components.

If we can characterize the frequency-response of the component across the spectrum of the transient time-stepping, then we can confidently use the model in a transient analysis – there are many ways to characterize and use this data.

Frequency-Dependent Components in Transient Simulations


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Resistors, Inductors, Capacitors, Connectors, Bus-bars, Cables, Transformers, etc.

Datasheets or Test Data Import with Sheet-Scan and/or Network Data Explorer

Define with labelled parasitics (ESR, ESL)

Simulation Maxwell for Magnetics, Cables

Q3D for bus-bars, transmission lines

SIwave for layered PCBs

Parasitic RLCs are NOT indicated in circuit diagrams!!

Passive Component Characterization

Imports touchstone (.s*p) or citifile (.cit) from impedance analyzer, and

ANSYS-native formats!


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Ideal R L C

Constant values yields simple frequency dependence (linear relationship of impedance in log-log plots).


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1.00E-001 1.00E+000 1.00E+001 1.00E+002 1.00E+003 1.00E+004 1.00E+005F [kHz]

-90.00

0.00

90.00

Ph

ase

[de

g]

-50.00

-25.00

0.00

25.00

Ga

in [

dB

]

00_nonideal_RImpedance

Curve Info

-E1.V/E1.IAC

A Freq-Dependent Resistor Model

R1C1

L1

n

p

+

V

VM1

A

AM1

p

n

E1

A resistor model with parasitic capacitance due to leakage and leads, and parasitic inductance for conductive leads. The model contains frequency effects including high-frequency resonance. ESL

ESL = Equivalent Series Inductance


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1.00E-001 1.00E+000 1.00E+001 1.00E+002 1.00E+003 1.00E+004 1.00E+005F [kHz]

-90.00

0.00

90.00

Ph

ase

[d

eg

]

-40.00

-15.00

10.00

25.00

Ga

in [d

B]

01_nonideal_LImpedanceCurve Info

-E1.V/E1.IAC

n

p

R1

C1

L1

+

V

VM1

A

AM1

A Freq-Dependent Inductor Model

An inductor model with parasitic capacitance between winding turns, and parasitic resistance of the coil wire. Contains frequency effects.

ESR

ESR = Equivalent Series Resistance


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1.00E-001 1.00E+000 1.00E+001 1.00E+002 1.00E+003 1.00E+004 1.00E+005F [kHz]

-90.00

0.00

90.00

Phase [deg]

-40.00

-15.00

10.00

35.00

60.00

Gain

[dB

]

02_nonideal_CImpedance

Curve Info

-E1.V/E1.IAC

n

p

R1

C1

L1

+

V

VM1

A

AM1

A Freq-Dependent Capacitor Model

A capacitor model with parasitic resistance, and parasitic inductance for conductive leads. Contains frequency effects including high-frequency resonance.

ESL

ESR

ESL = Equivalent Series Inductance ESR = Equivalent Series Resistance


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Freq-Dependent Components in Transient

0

Trap_WavePWIDTH=1e-005

TRISE=0.1us

TFALL=0.1us

TPERIO=5e-005

E1

L1

C1 R2

1 1 1 1 1 1Time [ms]

-0.20

0.30

0.80

1.22

R2

.V [

V]

Curve Info

R2.VTR

0 10 20 30 40 50Spectrum [MHz]

-150

-100

-50

0

dB

(R2

.V)

Curve Info

dB(R2....TR

R=10ohm

C=10nF

L=1uH

0

Trap_WavePWIDTH=1e-005

TRISE=0.1us

TFALL=0.1us

TPERIO=5e-005

E1

pn

pn

p n

1 1 1 1 1 1Time [ms]

-0.20

0.30

0.80

1.23

R_

fre

q1

.V

Curve Info

R_freq1...TR

0 10 20 30 40 50Spectrum [MHz]-140

-90

-40

0

dB

(R_

fre

q1

.V)

Curve Info

dB(R_freq1....TR

R=10ohm

C=10nF

L=1uH

Ideal RLC Freq-Dependent RLC


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EMI/EMC Library and Examples

p n

p n

p n

LISNLine ImpedanceStabilization Network

Pos_Dev ice

Gnd_Dev ice

Pos_Source

Gnd_Source


Neg_Dev ice

Pos_Dev ice

Gnd_Dev ice

Pos_Source

Neg_Source

Gnd_Source

Within the Library Component Definitions are available for RLC and LISNs.


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EMI is the creation and coupling of unwanted signals.

The creation of signals is caused by switching in active devices.

The coupling of signals is caused by electromagnetics in passive components and can be analyzed with Maxwell’s Equations.

Interference is caused when the combination of large switching signals have an efficient path/coupling to a neighboring part.

EMI Theory Overview


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Three Factors – EM Noise Issue

1) Noise Source(EMI) – starts with active/passive circuit; coupled via space

2) Load (Immunity) – immunity response is a combination of noise source and coupling through circuit/space.

3) Path – both circuit and space – both lumped components and 3D geometry.

EMI Source

Immunity

Conductive Noise

Inductive Noise

Capacitive Noise

Radiation Noise

Conduction Path (SIMPLORER)

Space Path

High Frequency (HFSS) Low Frequency

(MAXWELL/Q3D)

Space

“EMC ANALYSIS METHODS AND COMPUTATIONAL MODELS” : Frederick M. Tesche, Michel V. Ianoz :John Wiley & Sons, Inc. 1997 p34-36


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Saturation will affect the waveform shape through inductors and chokes.

Magnetic permeability and loss are frequency dependent, and so will be resistance and inductance.

These values can be calculated and extracted from Maxwell 2D/3D from geometry data.

Magnetics Design and Modeling


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Accurate Semiconductor Characterization

Allows creation of a Simplorer component from a datasheet for - IGBTs - Power Diodes - MOSFETs


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EMI analysis by Q3D LRC extraction

Circuit Model ・DC or AC

Static

Circuit Model ・DC or AC

State Space Model ・Freq. Sweep

Dynamic

Equiv. Circuit

Project info.

R/L vs Freq.

DC Circuit Model

AC Circuit Model

State Space / IFFT Model

Q3D Simplorer

IGBT Package and BusBar RLC Extraction


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Cable Design Toolkit

Cable will be often called a noise main factor…

Maxwell/

Q3D Extractor Simplorer

Bounds Noise

Surge Noise

Geometry: 2D with skew


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Need common ground reference defined even when using galvanically isolated converters.

Ground with care in order to preserve isolation, and also to provide realistic return paths (DC to HF).

Can create secondary grounds for Signal Ground and Chassis Ground, in addition to global “Earth Ground”.

Provide realistic impedances between ideal ground and secondary ground-planes – necessary for ground loops.

Ground References in Simplorer


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Simulation Requirements

Determine Critical Components in the System Characterize these well across operating points

Model all passive components from impedance analyzer

Model active components from datasheet if not measurement

Model all Current Paths – Especially Ground Loops

Create Geometric Model in Q3D to Solve for Parasitics

Solve Transient Model in Simplorer

Compare to Limits and Standards

Optimize Design – both Circuit and Layout for EMI


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0

E1

MOS1

D1

L1

C1 R1

TRAPEZ1

L2

R2

DC-DC Buck Converter Example

Ideal Converter Schematic

0 0

E1

MOS1

D1

L1

C1 R1

TRAPEZ1LISNLine ImpedanceStabilization Network

Neg_Device

Pos_Device

Gnd_Device

Pos_Source

Neg_Source

Gnd_Source

R2

L2

Converter with LISN

0 0

0

E1

L1

C1

TRAPEZ1

pn


Neg_Device

Pos_Device

Gnd_Device

Pos_Source

Neg_Source

Gnd_Source

pn

pn pn

pn

pn

pn

pn

pn

pn

pn

E2

p nSPICE_D1

pn pn

pn pn pn

pn

L2

L3

pnpn

N_1

N_

2

N_3

Real Schematic realized in Simplorer

[Master Thesis] “EMI Measurements and Modeling of a DC-DC Buck Converter”, G. Johannesson, N. Fransson, Chalmers University of Technology, June 2008.


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Further Material Available

EMI/EMC Library with Documentation and Examples

IGBT Characterization Workshop

Cable-Design Toolkit Workshop

Q3D-Simplorer EMC Example

Signal Integrity examples: SIwave, HFSS, Q3D


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Summary

Include all frequency effects: - By Geometric Simulation (Q3D, Maxwell, HFSS, SIwave) - By Datasheet (Network Data Explorer) - By manually adding extra parasitic RLCs

Connect grounds with reasonable impedances to include any ground loops and physical couplings.

Both Passive and Active components are necessary for accurate circuit simulation.

Simplorer enables the combination of power electronics simulations, and their controls, with the accuracy of finite element and test data.

Key Points in Simulation-based Conductive Noise...

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