PKS603-607

Rev. I 10/06

8

Application Example

ThecircuitshowninFigure15isalowcost,highefficiency,

flyback power supply designed to provide a 30 V, 1.06A

continuous,2.7Apeakoutputfromuniversalinputusingthe

PKS606Y.

Thesupplyfeaturesunder-voltagelockoutandsmartACsensewith

fastreset.Latchingoverload,openloop,andhystereticthermal

shutdownprotectboththesupplyandloadunderfaultconditions

whilehighefficiency(>80%)andverylowno-loadconsumption

(<200mWat230VAC)meetsbothactiveandstandbyefficiency

requirements.Outputregulationisaccomplishedusingasimple

Zenerreferenceandoptocouplerfeedback.

ComponentsC1,C2,C3,C10,C17,C19,R15,L1andL2provide

commonmodeanddifferentialmodeEMIfiltering.Resistors

R1andR2dischargeC3whenACpowerisremovedtoprevent

electricshockfromtouchingtheACinput.ThermistorRT1

limitsthepeakinrushcurrentwhenACisfirstapplied.

Therectifiedandfilteredinputvoltageisappliedtotheprimary

windingofT1.Theothersideofthetransformerprimaryis

drivenbytheintegratedMOSFETinU1.DiodeD6,C5,R3,

R4,andVR1clamptheU1drainvoltagetosafelevels.Use

ofafastdiode(500ns)vsultrafastforD6increasespower

supplyefficiencybyrecoveringsomeoftheclampenergy.A

sloworstandardrecoverydiodemustnotbeusedduetothe

highswitchingfrequency(aslowdiodewillnotrecoverfast

enoughunderstartuporoutputfaultsandthereforefaildue

toexcessdissipation).TheuseofaZenerinserieswithR3

comparedtoastandardRCDclampoptimizesbothEMIand

energyefficiency.

ComponentsD5,C7,andR5-6provideAClineandunder-

voltagesensingforPeakSwitchU1.Byprovidingaseparate

rectifiedvoltageacrossC7whichisindependentfromtheload

condition,ratherthanusingthemaininputcapacitor,allows

PeakSwitch

todistinguishthecauseoflossofregulation.It

alsoprovidesfastresetwhentheACinputisremoved,should

latchingshutdownbetriggered.ConnectingR5andR6toC4

wouldstillprovideunder-voltagelockoutbutafterafaultthe

userwouldhavetowaitforC4todischargebeforethesupply

wouldreset.ResistorR16providesasmallamountofbiasto

theU1ENABLE/UNDER-VOLTAGEpintoretaintheunder-

voltagelockoutfunctionduringbrown-outconditions.

WithR5andR6present,switchingisinhibiteduntilthecurrent

intotheEN/UVpinexceeds25µA.Thisallowsthestartup

voltagetobeprogrammedwithinthenormaloperatinginput

voltagerange,preventingglitchingoftheoutputunderabnormal,

lowvoltageconditionsandalsoonremovaloftheACinput.

Underafaultcondition,forexampleanoutputshortcircuitor

brokenfeedbackloop,ifthelinevoltageiswithinthenormal

range(>25µAintotheEN/UVpin)thePeakSwitchwilllatch

T1

EE25

J1

L

PE

N

30 V @

1.07 A Cont.

2.7 A Peak

RTN

D5

1N4007

D6

FR106

D10

UF4003

D8

STPS3150

D9

1N4148

D7

1N4148

U2

PC817X4

Q2

FS202DA

J3

PCB Term 18 AWG

RTN Connected to PE via Flying Lead

Q1

2N3906

D1-D4

1N4007

L1

5.3 mH

L2

5.3

µH

R2

1.3 M

Ω

R1

1.3 M

Ω

R15

2.2

Ω

R4

22

Ω

1/2 W

R3

10 k

Ω

1/2 W

R5

2.2 M

Ω

R6

2.4 M

Ω

R16

2.7 M

Ω

R7

4.7 k

Ω

R12

1 k

Ω

R13

1 k

Ω

R14

100

Ω

R11

3 k

Ω

R10

1.5 k

Ω

R9

0.33

Ω

2 W

R8

68

Ω

1/2 W

C3

680 nF

X1

C1-C2

100 pF

250 VAC

C17

4.7 nF

1 kV

C6

47

µF

35 V

C15

100 nF

50 V

C16

100 nF

C12

330

µF

50 V

C10

1 nF

250 VAC

C11

330 pF

U1

PKS606Y

C13

47

µF

16 V

C14

220 nF

50 V

C7

100 nF

400 V

C8

220 nF

50 V

C5

2.2 nF

1 kV

VR1

1N4764A

100 V

VR2

1N5255B

28 V

VR3

1N5258B

36 V

1

9,10

7,8

4

5

3

2

C4

150

µF

400 V

F1

3.15 A

RT1

10

Ω

PI-4170-060706

PeakSwitch

C19

1 nF, 250 VAC

D

S

EN/UV

BP

GND

Figure 15. PeakSwitch PKS606Y, 32 W Continuous, 81 W Peak, Universal Input Power Supply.