057 - norpie 2004 presentation

8/6/2019 057 - Norpie 2004 Presentation

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All rectified ac sine wave voltages with capacitive

filtering draw high amplitude discontinuous current

pulses rich in harmonics , causing:

Low input power factor

High circulating currents


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There are many approaches to mitigate this

problem :

Passive and Active power factor correction

Passive and Active filtering of network

Accepting non-sinusoidal voltage / current in the

system.


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Passive Power Factor Correction

Simple inductive input filter

Inductor stores energy to maintainconduction throughout half cycle

Hence reduces harmonic distortation andimproves power factor

But size, weight and cost limits itsapplication upto 200W


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Active high frequency power factor correction

Makes load behave like a resistor

Near unity load power factor

Load generating negligible harmonics


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Types of active PFC circuits with Boost

converter topologies

Hard switched

Soft switched using ZVT

Discontinuous Conduction mode (DCM)

Critical Conduction mode (CRM)

Continuous Conduction mode (CCM)


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Block Diagram of an active PFC Circuit of

CCM Boost converter


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Mosfet & Diode switching waveforms showing switching losses


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Switching loss reduction strategies

RCD Snubber Circuits

Magnetic Snubber Circuits

Power Switch types - IGBT or MOSFET

Boost Diode Options

SiC Schottky Diodes

Single Package Series connected diodes

PFC specific single diodes


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Magnetic Snubber Circuit


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Comparison of recovery time of various diodes


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Comparision of RECOVERY TIME and COST of various diodes

Diode TypePart

NumberRating

TypicalRecovery

time

SupplierCost in

USD

Sic Schottky SDT12S60 12A, 600V Zero Infineon 7.69

Single package

seriesconnected

DSEE 808CC 10A, 600V 30ns IXY S 2.46

Single package

series

connected

STTH806TTI 8A, 600V 30ns ST Micro 1.82

PFC Specific 1SL9R1560P2 15A, 600V 25ns Fairchild 1.42

PFC Specific 15ETX06 15A, 600V 18ns IR 1.03


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Experimental Results

PFC Specific DiodeSingle Package

Series ConnectedDiode

SiC SchottkyDiodes

Input AC Voltage

(RMS)

85 264V 85 264V 85 264V

SwitchingFrequency

100kHz 100kHz 100kHz

Input Power (W) 652 1076 653 1078 642 1049

Output Power (W) 600 1006 598 998 597 1001

Efficiency 0.92 0.935 0.915 0.925 0.93 0.954


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Effect of Diode Recovery Current on the

Switching Current at turn-on

The switch turn-on peak current was the lowest

for the SiC Schottky Diode and highest for the

Single Package Series Diode


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Effect of Diode recovery current on Mosfet

drain current with a SiC Diode


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drain current with a PFC specific diode


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drain current with a single package series

connected diode


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Conducted EMI generated by the PFC board

was measured separately for each of the

three diode types:

Measurements were made at90V AC input, 600W output load witha 3mH common mode EMI filter connected at the input circuit

Low freq part of conducted emission spectrum ( 150kHz - 1

MHz) is almost unaffected by different diode types

High freq part of conducted emission spectrum ( 1 MHz -30MHz) is affected by diode behavior

SDT12S60 SiC Schottky diode generates lower noise

Increased EMI caused by STTH806TTI single package seriesconnected diodes is only about 4dBQV


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Low frequency conducted emission

SiC DiodeSiC Diode Single package series connected diodeSingle package series connected diode

PFC Specific DiodePFC Specific Diode


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High frequency conducted emission

Single package series connected diodeSingle package series connected diode

PFC Specific DiodePFC Specific Diode

SiC DiodeSiC Diode


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OPTIMIZING PERFORMANCE BY DESIGN -

A SUMMARY

Power levels < 200 - Criticalconduction mode PFC may beconsidered

Power levels > 200 - HardswitchedCCM PFCis preferred

Power levels < 1000 & sw. freqof 100kHz -PFCspecificisthe bestchoice

Power levels > 1000 & sw. freq> 100kHz -HigherinitialcostsofSiCSchottkydiodesare justified

Hi ereffi i encyor i er sw. freq-ZVTresonant mode boostconvertermay beconsidered

Power levels < 600 - OldergenerationMosfetslike IRF N(IR) couldreducecostsw/oaffecting performancesignificantly

057 - norpie 2004 presentation

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