active pfc boost rectifier emc2

14
1 Giorgio Spiazzi University of Padova Italy Active PFC Boost Rectifier Power section CHARACTERISTICS: Input voltage: V in = 90-260V RMS Output voltage: V o = 380V Output power: P o = 600W Switching frequency: f s = 70kHz Control PFC line load VALUES: Output capacitor: C = 680 mF Inductor: L = 600 mH Mosfet: IRFP450 Diode: RURP1560 Controller: L4981A Giorgio Spiazzi University of Padova Italy Active PFC Boost Rectifier General Considerations: MOSFET and DIODE are the main noise generators Short wires where high dv/dt Small area of fast di/dt loops Short paths for return currents Power section and related EMI aspects Careful Layout High di/dt loop Line Load High dv/dt wires Common mode capacitive coupling

Upload: ahmed58seribegawan

Post on 08-Feb-2016

73 views

Category:

Documents


2 download

TRANSCRIPT

Page 1: Active PFC Boost Rectifier EMC2

1

Giorgio SpiazziUniversity of Padova

ItalyActive PFC Boost RectifierPower section

CHARACTERISTICS:

Input voltage: Vin = 90-260VRMS

Output voltage: Vo = 380VOutput power: Po = 600WSwitching frequency: fs = 70kHz

ControlPFC

line load

VALUES:

Output capacitor: C = 680 µµFInductor: L = 600 µµHMosfet: IRFP450Diode: RURP1560Controller: L4981A

Giorgio SpiazziUniversity of Padova

ItalyActive PFC Boost Rectifier

General Considerations:

MOSFET and DIODE are the main noise generators

• Short wires where high dv/dt

• Small area of fast di/dt loops

• Short paths for return currents

Power section and related EMI aspects

Careful Layout

High di/dt loop

Line Load

High dv/dt wires Common modecapacitive coupling

Page 2: Active PFC Boost Rectifier EMC2

2

Giorgio SpiazziUniversity of Padova

Italy

Circuit Layout (components)Input Output

OutputfilterInput

filter

Control and drive

Power stage

Giorgio SpiazziUniversity of Padova

ItalyActive PFC Boost Rectifier

Circuit Layout (solder layer)

Page 3: Active PFC Boost Rectifier EMC2

3

Giorgio SpiazziUniversity of Padova

ItalyActive PFC Boost Rectifier

Circuit Layout (component layer)

Giorgio SpiazziUniversity of Padova

Italy

MOS D

Circuit Layout ConsiderationsActive PFC Boost Rectifier

High dv/dt track is short ...... and shielded between

+Vout and -Vout tracks

Short paths amongswitching components

and filter capacitor

Page 4: Active PFC Boost Rectifier EMC2

4

Giorgio SpiazziUniversity of Padova

ItalyActive PFC Boost Rectifier

Circuit Layout Considerations

Control

Short (and shielded)track at analog

inputs

Shielding tracksconnected to reference

Small area of the gatecircuit. Snubber close to

gate and source terminals

Giorgio SpiazziUniversity of Padova

ItalyActive PFC Boost Rectifier

Star connection ofground paths Common mode

filter capacitors

Shield planeconnected to

reference

Circuit Layout Considerations

Page 5: Active PFC Boost Rectifier EMC2

5

Giorgio SpiazziUniversity of Padova

ItalyActive PFC Boost Rectifier

Coupled inductors show highcommon mode inductance but lowdifferential mode inductance:

Ex: 6.8 mH CM, 70 µµH DM

Power section with EMI Filters

idm

icm

High CM impedance Low CM impedance

Giorgio SpiazziUniversity of Padova

ItalyActive PFC Boost Rectifier

Differential mode input noise: 70 kHz, 87 dB µµV (peak values) 140 kHz, 57 dB µµV

210 kHz, 40 dB µµV280 kHz, 26 dB µµV350 kHz, 19 dB µµV420 kHz, 9 dB µµV

a suitable margin (20 dB µµV) is maintained for the commom mode noiseand possible resonances

Input filter design - Differential Mode

vn

1 Fµ 2 Fµ

L = 70 Hµdm

L = 6.8 mHcm

idm50 Ω

50 Ω

Ripple amplitude

triangular waveform

∆IUf L

Aout

smax .= ≅

8113

Page 6: Active PFC Boost Rectifier EMC2

6

Giorgio SpiazziUniversity of Padova

ItalyActive PFC Boost Rectifier

• Several current return paths are present

• The main one is on the output side of the PFC

• High value of filter inductor reduces current term at the input side

• CM input side current generates DM input noise due to asymmetricalconverter topology

• Adding CM capacitors at the input side reduces input CM voltage noise butthe increased CM current causes additional DM noise

Input filter design - Common Mode

50 Ω

1 Fµ 2 Fµ

L = 6.8 mHcm

icm

100 nF

4.7 nF

4.7 nF

icm

Giorgio SpiazziUniversity of Padova

ItalyPrototype Tests

v

i

Input behavior

Line current

Line Voltage

100 V/div.

2 A/div.

Page 7: Active PFC Boost Rectifier EMC2

7

Giorgio SpiazziUniversity of Padova

ItalyPrototype Tests

v

iL

Line Voltage and Inductor Current(peak to peak sampling)

Inductor currentswitching ripple

Giorgio SpiazziUniversity of Padova

ItalyPrototype Tests

vGS

vDS

Gate drive circuit

vG iD

iL

IL+IDthreshold

Voltagedrop

ILthreshold

Page 8: Active PFC Boost Rectifier EMC2

8

Giorgio SpiazziUniversity of Padova

ItalyPrototype Tests

vGS

vDS

Gate drive circuit

vG iD

iL

ILthreshold

Commutationis slowed-

down

Giorgio SpiazziUniversity of Padova

ItalyPrototype Tests

vDS

vGS

vGiDiG

Gate drive circuit

Drain-Gatecoupling

Page 9: Active PFC Boost Rectifier EMC2

9

Giorgio SpiazziUniversity of Padova

ItalyPrototype Tests

vDS

vGS

vGiDiG

Gate drive circuit

Giorgio SpiazziUniversity of Padova

ItalyPrototype Tests

Modulation of Switching FrequencyVDS Spectra

Modulated

Fixed

Page 10: Active PFC Boost Rectifier EMC2

10

Giorgio SpiazziUniversity of Padova

ItalyPrototype EMI TestsConducted noise (peak measure)

Phase Neutral

Giorgio SpiazziUniversity of Padova

ItalyPrototype EMI Tests

Introducing input-side common-modefilter capacitors

• Differential noise increases (circuit isnot symmetrical) and low-frequencybehavior is worse

• A resonance, between input andoutput CM filter capacitors and theinductances of their connections,appears, modifying the high-frequency behavior

Conducted noise (peak measure)

Line PFC

Added

Page 11: Active PFC Boost Rectifier EMC2

11

Giorgio SpiazziUniversity of Padova

ItalyPrototype EMI Tests

Increased output-side common-modecapacitors

• Common mode currents are closed onthe output side (no additional voltagedrop on the input filter occurs)

• Low-frequency behavior is improved

• High-frequency behavior becomesworse due to resonance of two CMfilter capacitors and their connections

Conducted noise (peak measure)

LoadPFC

Added

Giorgio SpiazziUniversity of Padova

Italy

By connecting the heatsink to thenegative rail (capacitive currents areclosed “near” to the Mosfet source):

•Low-frequency behaviour is improved

•High-frequency behavior is good (theheatsink shields all circuitry)

Prototype EMI TestsConducted noise (peak measure)

Page 12: Active PFC Boost Rectifier EMC2

12

Giorgio SpiazziUniversity of Padova

Italy

By inserting a shield, between Mosfetand heatsink, connected to Mosfetsource (drain coupled capacitivecurrents are closed directly to the Mosfetsource)•Low-frequency behavior is improved(common mode noise is reduced)•High-frequency behavior is good (Usingthe heatsink as shield of the whole circuitgives however better results)

Shield

Prototype EMI TestsConducted noise (peak measure)

Giorgio SpiazziUniversity of Padova

Italy

Switching Frequency Modulation

Switching frequency harmoniccomponents disappear

• Measured peak noise remainsunchanged

• Measured average noise isconsiderably reduced

Peak

Average

Prototype EMI TestsConducted noise (peak measure)

Page 13: Active PFC Boost Rectifier EMC2

13

Giorgio SpiazziUniversity of Padova

Italy

Effect of Diode Reverse Recovery(Disconnecting gate snubber)

• Low-frequency behavior is almostunchanged

• High-frequency behavior is heavilyworsened

vG iD

iL

Prototype EMI TestsConducted noise (peak measure)

Giorgio SpiazziUniversity of Padova

Italy

Increasing gate resistor

• Low-frequency behavior remainsunchanged

• High-frequency behavior is improved(MOSFET commutation slows down)

vGiDiG

33 72 Ω

Prototype EMI TestsConducted noise (peak measure)

Page 14: Active PFC Boost Rectifier EMC2

14

Giorgio SpiazziUniversity of Padova

Italy

By spreading the ac wires close to theinput filter (filter inductors inside plasticcan)

•Low-frequency behavior becomesworse (input wires capture leakagemagnetic field of filter inductor)

•High-frequency behavior remainsunchanged

Line PFCEMIFilter

Increased Area

Prototype EMI Tests