Power e Lab Designing a 90% efficiency 150W power supply with PFC in hours Prepared by Dr. Franki Poon & Dr. Joe Liu PowerELab Limited .

PowerPowereeLabLab

Designing a 90% efficiency 150W power supply with PFC in hoursPrepared by Dr. Franki PoonPrepared by Dr. Franki Poon & Dr. Joe Liu & Dr. Joe Liu PowerELab LimitedPowerELab Limited www.powerEsim.comwww.powerEsim.com 11

Explanation of Electromagnetic Interference Explanation of Electromagnetic Interference (EMI) in Switching Power Supply(EMI) in Switching Power Supply

Speakers

Dr. Franki Poon, Dr. Joe Liu

Power eLabThe PowerELab Limited

© copyright 2006

PowerPowereeLabLab


EMI solutions: Passive filterEMI solutions: Passive filter

Conventional EMI solutions depend on passive filter using inductors and capacitors:

Inductors: CMC, DMC Capacitors: X-cap, Y-cap

There are limitations when using passive filters: Inductors: Large size and high conduction loss Capacitors: leakage current specifications

PowerPowereeLabLab


Active EMI cancellation IC WT6001:Active EMI cancellation IC WT6001:An effective EMI solution – Y-cap boosterAn effective EMI solution – Y-cap booster

A patented technology developed in PowerELab. An SO-8 IC WT6001 developed with W2.W2. Equivalent to a Y-cap with very large value within the EMI concerned

frequency range only. No boosting effect in the leakage current test concerned frequency

range (50 – 800Hz). Greatly reduce the common mode inductor size and requirements. Reduce converter size and improve conversion efficiency. Provide effective and efficient EMI solution. Built-in electrical surge protection which can easily pass the

EN61000-4-4 and EN61000-4-5 immunity standard.

WT6001

PowerPowereeLabLab


Applications: Replace passive Y-cap Applications: Replace passive Y-cap

LISN

Replaced by Y-cap booster

PowerPowereeLabLab


Effect measurable by oscilloscope Effect measurable by oscilloscope when using Y-cap boosterwhen using Y-cap booster

Noise voltage across Y-cap in switching converter

Noise voltage across Y-cap booster in switching converter

More application examples can be found in the datasheet of WT6001

PowerPowereeLabLab


Practical application examplesPractical application examples

The original EMI filter design cannot pass the EN55022 class B limit.

Filter component:

2 x 20mm high mu toroid for common mode filters 2 x 0.15uF X – cap 1 x 1n Y1-cap connected between primary and secondary

PowerPowereeLabLab


Practical application examples:Practical application examples: Original filter schematic Original filter schematic

C2

L2B

13

24

C1

L1B

13

24

P1

1

P2

1

TH1 F1

• It is a commonly used filter configuration

• L2B is wound with many turns which intends to suppress the low to mid-frequency common mode noise. Its leakage inductance together with C1 also provides differential mode noise filtering

• L1B is a single layer, bi-filer wound common mode choke for high frequency common mode noise filtering

PowerPowereeLabLab


Practical application examples: Practical application examples: EMI measurementEMI measurement

230V pri-sec Y1n U shielded original

EN 55022; Class B Conducted, Average

EN 55022; Class B Conducted, Quasi-Peak

0

10

20

30

40

50

60

70

80

1 10

dBuV

10/3/2005 10:55:40 (Start = 0.15, Stop = 30.00) MHz

DM noiseCM noise

230V pri-sec Y3n3 U shielded original

EN 55022; Class B Conducted, Average


0

10

20

30

40

50

60

70

80

1 10

dBuV

10/3/2005 16:08:11 (Start = 0.15, Stop = 30.00) MHz

Y-cap: From 1n to 3n3Improved but not enough

Failure was identified to be caused by:• Insufficient leakage inductance of the common mode choke for DM noise

attenuation.• The two common mode choke cannot effectively block out the common mode

current.• Further increase of Y-cap can reduce CM noise but fail to meet leakage current

specifications.

PowerPowereeLabLab


Practical application examples:Practical application examples: Solution using Y-cap booster Solution using Y-cap booster

230V CB U shield SDMC SCMC .33uFEN 55022; Class B Conducted, Average


0

10

20

30

40

50

60

70

80

1 10

dBuV

10/3/2005 16:39:55 (Start = 0.15, Stop = 30.00) MHz

Y-cap booster is used to replace the primary to secondary Y-cap

After using the Y-cap booster, L2B is replaced by a small differential mode filter and L1B is reduced to a 9mm toroid with only a few turns to tackle the high frequency common node noise. The test results pass the required limit lines

PowerPowereeLabLab


Practical application examples:Practical application examples: Filter comparison: Before and After... Filter comparison: Before and After...

Failed design even with morecost, loss and bigger size for thefilter

Passed design using Y-cap booster with much smaller filter size that saves cost, power and space

PowerPowereeLabLab


Another practical application examples:Another practical application examples: Filter comparison: Before and After... Filter comparison: Before and After...

Original EMI solution using passive filterin ATX converter

New EMI solution using Y-cap boosterin ATX converter

PowerPowereeLabLab


ConclusionConclusion

Y-cap booster breaks the relationship between the Y-cap values and leakage current requirement.

Greatly reduce product design period and resources.

It can be applied to any position with conventional Y-cap.

Significantly reduce the size and loss of common mode choke implies higher power density and efficiency.

EMI less sensitive to transformer winding capacitance implies more rooms for improving transformer coupling.

Very suitable for equipment required low leakage current like medical equipment.

PowerPowereeLabLab


Active Diode – An easy to use and high Active Diode – An easy to use and high efficiency rectifier suitable for all convertersefficiency rectifier suitable for all converters

Stringent requirements of nowadays converters:

Compact size Low heat generation and high conversion efficiency High output power and output current Low cost ………!!!

Conventional technologies cannot meet the requirements!!

PowerPowereeLabLab


Synchronous rectifierSynchronous rectifier Use MOSFETs to replace diode rectifiers.

AK 7.8 m9 m0.24 V

AK

PowerPowereeLabLab


Synchronous rectifierSynchronous rectifier

0 2 4 6 8 100

0.5

1

1.5

2

2.5

3

STPS30L30SO8 Active Diode

Losses comparison between SCK and AD

A

W

MOSFET 0.7W losses @ 10A

SCK 2.8W losses @ 10A

Provides low conduction loss.

Can operate at higher high current without heatsink.

PowerPowereeLabLab


Synchronous rectifierSynchronous rectifier Usage not limited to converters with high profit margin.

Price of nowadays low RDSon MOSFETs comparable to schottky diodes using the state of the art technology.

Provide even lower converter cost because of reduced heatsink, more output power, higher conversion efficiency…..

Emerge in low cost converter like adaptors, standard open frame converters, ATX …… .

PowerPowereeLabLab


Synchronous rectifierSynchronous rectifierA

D

AD

Problematic for some conventional topologies

Special and sometimes complicated driving circuits SR

are needed for different topologies

Performance sensitive to transformer leakage

inductance and operating conditions

Converter cannot be paralleled – Reverse current

Poor efficiency at low load

Limited input voltage range

Simple circuit

Discontinuous mode is allowed

Good low load efficiency

Converter can be paralleled

High conversion efficiency

Works just like a diode

PowerPowereeLabLab


Active diode – Operating principleActive diode – Operating principle

N1 is the current sense winding N2 provides MOSFET driving signals A1 driver circuit (IC WT6002) N1 N3 & D1 form energy recovery

circuit N4 & D2 form reset circuit

AK

N1 N2

N3 N4

D1 D2

A1

PowerPowereeLabLab


Active diode – Operating principleActive diode – Operating principle

Voltage across winding N2 or gate drive voltage Von of SR depends on ratio of N2 to N3

and voltage Vo

Voltage source Vo

can be any voltage source in a converter, e.g. output voltage

3

2N

NVV oon

AK

N1 N2

N3 N4

D1 D2

A1

Toff

Vo

Vo

VN2

VN3

VN4

Von

Ii

PowerPowereeLabLab


Application of Active Diode in Application of Active Diode in different topologiesdifferent topologies

FlybackFlyback ForwardForward

S

Flyback SR

Co

+

Vin

-

+

Vo

-

S

MagneticReset

Forward SR

FreewheelSR

Lf

Co

+

Vo

-

+

Vin

-

PowerPowereeLabLab



Half Bridge centre tapHalf Bridge centre tap Current DoublerCurrent Doubler

S1

S2

C1

C2

SR1

SR2

Lf

Co

+

Vin

-

+Vo

-

+Vo

-

S1

S2

C1

C2

SR1

SR2

Lf1

Co

Lf2

+

Vin

-

PowerPowereeLabLab



Resonant converterResonant converter

and many others….and many others….

SR1

SR2

Co

+Vo

-ISIN

PowerPowereeLabLab


Successful application of Active Diode Successful application of Active Diode in converter productsin converter products

AD on 150W ACDC AD on 120W ACDC

AD on 50W ACDC AD on 300W ACDC AD on 60W ACDC AD on 100W DCDC

AD on 1.5 V 200 A ACDC

PowerPowereeLabLab


ConclusionConclusion A new “Active Diode” technology is presented.

A kind of current driven synchronous rectifier technology that provides high conversion efficiency and eliminates many conventional synchronous rectifier application problems.

Patented technologies.

An Active Diode driver IC WT6002 for easy implementation of the technology.

Well proven by many converter product design.

PowerPowereeLabLab


ReferencesReferences• Liu, J.C.P.; Poon, F.N.K.; Xuefei Xie; Pong, M.H.; current driven synchronous rectifier with energy recovery sensor Power

Electronics and Motion Control Conference, 2000. Proceedings. PIEMC 2000. The Third International , Volume: 1 , 2000, page(s): 375 -380 vol.1

• Xuefei Xie; Liu, J.C.P.L.; Poon, F.N.K.; Man Hay Pong; Current-driven synchronous rectification technique for flyback topology, Power Electronics Specialists Conference, 2001. PESC. 2001 IEEE 32nd Annual , Volume: 1 , 2001, Page(s): 345 -350 vol. 1

• Xuefei Xie; Liu, J.C.P.; Poon, F.N.K.; Man Hay Pong; A novel high frequency current-driven synchronous rectifier for low voltage high current applications, Applied Power Electronics Conference and Exposition, 2001. APEC 2001. Sixteenth Annual IEEE , Volume: 1 , 2001, Page(s): 469 -475 vol.1

• Liu, J.C.P.; Xuefei Xie; Poon, F.N.K.; Pong, B.M.H.; Practical solutions to the design of current-driven synchronous rectifier with energy recovery from current sensing, Applied Power Electronics Conference and Exposition, 2002. APEC 2002. Seventeenth Annual IEEE , Volume: 2 , 2002, Page(s): 878 -884 vol.2

• Xuefei Xie; Joe Chui Pong Liu; Poon, F.N.K.; Man Hay Pong; A novel high frequency current-driven synchronous rectifier applicable to most switching topologies, Power Electronics, IEEE Transactions on , Volume: 16 Issue: 5 , Sep 2001, Page(s): 635 -648

• Xie Xuefei; Liu, J.C.P.; Poon, F.N.K.; Pong, B.M.H.; Two methods to drive synchronous rectifiers during dead time in forward topologies, Applied Power Electronics Conference and Exposition, 2000. APEC 2000. Fifteenth Annual IEEE , Volume: 2 , 2000, Page(s): 993 -999 vol.2

• US patent "Current driven synchronous rectifier with energy recovery" patent number 6,134,131

• US patent “Self-driven synchronous rectifier by retention of gate charge” patent number 6,377,477

• US patent “Current driven synchronous rectifier with energy recovery using hysterisis driver”, patent number 6,597,587

Power e Lab Designing a 90% efficiency 150W power supply with PFC in hours Prepared by Dr. Franki Poon & Dr. Joe Liu PowerELab Limited .

Documents

w power supply

joe liu power e lab

noise ycap

ycap booster ycap booster

ycap booster slide

joe liu powerelab limited

franki poon

secondary ycap