seminario viperplus - stmicroelectronics

ST Off-Line Power Supply

September 2011

Agenda

ST brief Introduction

Offline Common configurations

SMPS Fundamentals

SMPS Common Configurations

New VIPer+ Family

Roadmap

Products

Detailed description

New products

Magnetic Components

Lunch

Layout Recommendations

Design Tools

2

ST brief introduction

4

50/50 JV with Ericsson

* Source: iSuppli-2008 rankings, ST and ST-Ericsson

Wireless:

#2

Consumer:

#2 in Set Top Box

Computer:

#2 (HDD & Printers)

Automotive:

#3

Industrial:

#1

Products

Market Position*

Major Customers

Automotive, Consumer,

Computer and

Communication

Infrastructure (“ACCI”)

Industrial and

Multisegment Sector

(“IMS”)

Wireless

Home

Entertainment

& Displays

Computer &

Communication

Infrastructure

Automotive

Products

Group

Analog,

Power and

MEMS

Microcontrollers,

Memories and

SmartcardsMajor Product Lines

Market Segments

30 %

31 %

38%

5

Source: iSuppli, March 11th 2011

(x) * refers to M&A. Details provided on separate page.

2009Rank

2010Rank

Company Name2009

Revenue($)2010

Revenue($)

RevenuePercentChange

RevenuePercentof Total

RevenueCumulative

Percent

1 1 Intel 32,187 40,394 25.5% 13.3% 13.3%

2 2 Samsung Electronics 17,496 27,834 59.1% 9.2% 22.4%

3 3 Toshiba 10,319 13,010 26.1% 4.3% 26.7%

4 4 Texas Instruments (1) 9,671* 12,994 34.4% 4.3% 31.0%

95

Renesas Electronics (2) 5,15311,893* 130.8% 3.9% 34.9%

12 NEC Electronics 4,384

7 6 Hynix 6,246 10,380 66.2% 3.4% 38.3%

5 7 STMicroelectronics 8,510 10,346 21.6% 3.4% 41.7%

13 8 Micron Technology (3) 4,293* 8,876* 106.8% 2.9% 44.6%

6 9 Qualcomm 6,409 7,204 12.4% 2.4% 47.0%

14 10 Broadcom (4) 4,278 6,682* 56.2% 2.2% 49.2%

15 11 Elpida Memory 3,948 6,446 63.3% 2.1% 51.3%

8 12 AMD 5,207 6,345 21.9% 2.1% 53.4%

11 13 Infineon Technologies (5) 4,456* 6,319 41.8% 2.1% 55.5%

10 14 Sony (6) 4,468* 5,224 16.9% 1.7% 57.2%

18 15 Panasonic Corporation (7) 3,243* 4,946 52.5% 1.6% 58.8%

17 16 Freescale Semiconductor (8) 3,402* 4,357 28.1% 1.4% 60.3%

19 17 NXP (9) 3,240 4,028* 24.3% 1.3% 61.6%

23 18 Marvell Technology Group 2,572 3,633 41.3% 1.2% 62.8%

16 19 MediaTek 3,551 3,553 0.1% 1.2% 64.0%

20 20 nVidia 2,826 3,196 13.1% 1.1% 65.0%

Top 20 Companies 141,475 197,660 39.7% 65.0%

All Others 88,719 106,415 19.9% 35.0%

Total Semiconductor 230,194 304,075 32.1% 100.0%

2010 overall ranking

2010 ranking on ST SAM

2009Rank

2010Rank Company Name

2009Revenue

($)

2010Revenue

($)

RevenuePercentChange

RevenuePercentof Total

RevenueCumulative

Percent

1 1 Texas Instruments 9,671 12,994 34.4% 7.3% 7.3%

52

Renesas Electronics 5,14611,469 122.9% 6.4% 13.8%

9 NEC Electronics 4,119

2 3 STMicroelectronics 8,093 9,778 20.8% 5.5% 19.3%

4 4 Intel 5,721 7,233 26.4% 4.1% 23.3%

3 5 Qualcomm 6,409 7,204 12.4% 4.1% 27.4%

8 6 Broadcom 4,278 6,682 56.2% 3.8% 31.1%

7 7 Infineon Technologies 4,456 6,319 41.8% 3.6% 34.7%

6 8 Toshiba 5,053 5,659 12.0% 3.2% 37.9%

11 9 Samsung Electronics 3,279 4,348 32.6% 2.4% 40.3%

12 10 NXP 3,235 4,024 24.4% 2.3% 42.6%

18 11 Panasonic Corporation 2,428 3,647 50.2% 2.1% 44.6%

10 12 MediaTek 3,551 3,553 0.1% 2.0% 46.6%

17 13 Marvell Technology Group 2,458 3,472 41.3% 2.0% 48.6%

15 14 Freescale Semiconductor 2,537 3,204 26.3% 1.8% 50.4%

13 15 nVidia 2,826 3,196 13.1% 1.8% 52.2%

16 16 Fujitsu Semiconductor Limited 2,537 3,059 20.6% 1.7% 53.9%

14 17 Sony 2,810 2,999 6.7% 1.7% 55.6%

20 18 Analog Devices 2,091 2,862 36.9% 1.6% 57.2%

19 19 ROHM Semiconductor 2,286 2,776 21.4% 1.6% 58.7%

23 20 Maxim Integrated Products 1,657 2,367 42.8% 1.3% 60.1%

Top 20 Companies 80,522 106,845 32.7% 60.1%

All Others 59,587 70,997 19.1% 39.9%

Total Semiconductor 140,109 177,842 26.9% 100.0%

6

Source: iSuppli, March 11th 2011SAM = TAM – DRAM – Flash – MPU - Opto

Morocco

Malaysia

Manufacturing Locations

Philippines

Front-end fabs

Back-end fabs

China

(Shenzhen, Longgang)

Malta

Italy

(Agrate, Catania 6”& 8”)France

(Crolles I & II, Rousset, Tours)

Singapore 2009 sales : US$ 8.51 billion

2010 sales : US$ 10.346 billion

Approx. 53,000 employees in the group

15 main production sites

Advanced R&D centers in 10 countries

8

Innovation Investment

SMPS Fundamentals

9

Power Supply in Appliances

Power ranges from 3W to 15W

Non-isolated topologies are used where there

are no external electrical connection.

Isolated topologies are used where there is a

possibility of user touching electrical points.

Cost and simplicity are key drivers.

10

BUCK

11

Topology

12

++

IL

L1V2

V1

S1

S2

Topology Applied

13

L

Cout

VS

IIN

IGND

IIND

Buck topology – ON time

14

L

IIND

IM

ID

IL

Vsw

On

Buck topology – Off time

15

IM

ID

IL

Vsw

Off

L

IIND

Current/Voltage Waveforms

16

++

IL

L1V2

V1

S1

S2

IS1

IS2

IL

Vsw

Buck Example

17

Buck/Boost, Negative Output

18

IL

VD

ISWID

VIN

VOUT

RO

Negative Output Example

19

Continuous versus Discontinuous

Continuous refers to continuous current in the

inductor, there is always positive current flowing

in the inductor.

20

Inductor current

Load Current


Discontinuous refers to the inductor current

going to zero during every clock cycle.

21

Inductor current

Load Current


Discontinuous mode has higher peak currents.

Higher peak current lowers the efficiency.

Higher peak current increases the EMI energy.

22

EMI considerations for the Buck

EMI stands for ElectroMagnetic Interference and

is the result of noise generated by switching

devices.

EMI has two components, radiated and

conducted.

Radiated refers to the EMI that is “broadcast” into

the air by the module.

Conducted refers to EMI on the power line

emitted by the module.

23

EMI Considerations for the Buck

The buck has one switching point, the common

point of the two switches and the inductor.

A simple RC snubber at this switching point is

the most common method of reducing EMI (both

conducted and radiated).

24

Reduction of EMI

25

L

Cout

Snubber

VS

IIN

IGND

IIND

Effect of Snubber on VS(t)

26

No snubber

With Snubber

VS

T (ns)

Ringing causes big EMI numbers

Snubber lows frequency

and amplitude of ringing

50 100 150

FLYBACK

27

Topology

28

Topology Applied

29

VP VS

+ +

IP IS

Note: NP = # of primary turns

NS = # of secondary turns

VD

VIN

Transformer relationship

30

N12

N22

L1

L2

Where NX = number of turns

LX = inductance of winding

I1 I2

+

V1V1

+

N1 N2

N1

N2

V1

V2

V1

V2

I2

I1

Flyback topology – ON time

IQ1

VQ1

ID1

ON OFF ON OFF

C1

D1

C2

Q1

1 4

2 3

T1

Input DCOutput DC

+ +

-

-

+

+-

-

IQ1

SWPKQPT fILP 2

112

1

C1

D1

C2

Q1

1 4

2 3

T1

Flyback topology – OFF time

Input DCOutput DC

+ +

-

-

IQ1

VQ1

ID1

ON OFF ON OFF

+

+-

-

ID1

Charge and discharge of the core

33

I

t

VIN

LP V

OUT

LS

Drain Switching Waveforms (DM)

34

Drain Switching Waveforms (CM)

35

Diode Switching Waveforms

36

Current/Voltage Waveforms (discontinuous)

37

VD

VIN

IP

IS

VP

VS

VIN+VO*NP/NS

VIN

-VO*NP/NS

VOUT

VIN * NS/NP

T

t

IPEAK

Current/Voltage Waveforms (continuous)

38

VD

VIN

IP

IS

VP

VS

VIN+VO*NP/NS

VIN

-VO*NP/NS

VOUT

VIN * NS/NP

IPEAK

Quasi Resonant

39

VD

VIN

IP

IS

VP

VS

VIN+VO*NP/NS

VIN

-VO*NP/NS

VOUT

VIN * NS/NP

T

t

IPEAK

VD

VIN

IP

IS

VP

VS

VIN+VO*NP/NS

VIN

-VO*NP/NS

VOUT

VIN * NS/NP

T

t

IPEAK

Key difference between a

discontinuous mode flyback and

QR flyback:

1) There is no dead time in QR

flyback.

2) QR flyback is a variable frequency

scheme

EMI considerations for a Flyback

There are two commutation point in a flyback

The primary side power switch.

The secondary side diode switch

EMI is created only if there is a high frequency

power dissipation event.

For DM, the current is ~zero when the switch

turns on and the diode turns off.

Most of the EMI is generated when the switch

turns off and the diode turns on (the current is

highest).

40

Reducing EMI

High current tracks should be as short as possible

Area enclosed by high current loops, as indicated in red

should be minimized

It is recommended to place high current tracks close

each to other to compensate magnetic field and reduce

parasitic inductance

Use snubber to decrease dV/dt. Snubbers should be

placed with minimum trace lengths

Increase capacitance between primary and secondary

side of the transformer. Higher Leakage inductance

helps!!

Connect the VIPer Drain to the deepest primary winding

41

Reducing EMI

42

VP VS

+ +

VIN

Auxiliary Supply

43

VIN = 160VVOUT = < 40V

VAUX = 12V

Why Auxiliary Supply (1/2)

The PWM control loop uses 10V/5mA for power.

If the power supply is the input bus (rectified line

voltage) and VDD is ~10V then the PWM loop

will draw (160V-10V)*5mA=7.5W

The secondary output can’t be used because

galvanic isolation is required

Auxiliary supply allows low power consumption

and galvanic isolation.

Cost is low.

44

Why Auxiliary Supply (1/2)

Transformer action will also apply between the

secondary voltage and the auxiliary voltage.

Fault tolerence when reference/opto fails: No

overvoltage seen at output.

Short circuit behavior: with aux winding the max

output power is limited, no need to oversize

secondary side components.

45

Flyback Example

46

Buck Vs Flyback

Buck

Lower cost

Less components

Designed based on

output current

Differential EMI critical

Outputs must be

inaccessible to users

Single output commonly

Flyback

Higher cost

Custom transformer

Designed based on

output power

Common mode EMI

critical

Users can touch output

connectors or output

power stages

Multiple outputs possible

47

Viper Family

48

49

Solutions for low-medium power SMPS

The best energy saving approach Minimized stand-by power

High efficiency

The most reliable approach Avalanche rugged power section

Integration of advanced protections

Thermal shutdown sensor located on power section

The most flexible approach Modular product: controller + power section

Packages’ design and development

The most profitable partner Continuous products’ innovation

Technical support (competence centers, documentations, software)

Excellence in quality and supply chain

50

Secondary Controllers

HV Converters

VIPer Plus.

Primary Controllers

DELIVER the

power to

Transformer’s

Primary

Sync.

Rectification

RECTIFY Efficiently

(optional)

Replacement of the

diode

CC/CV

REGULATE

Constant Voltage &

Current

(Adapters,

Chargers,..)

DCAC

Controller + MOSFET

Solutions for low-medium power SMPS

New VIPer Plus family

51

GND / SOURCE DRAIN

FB

DRAIN

CONT / Lim

VDD

Function

+ Technology

+ Functionalities

+ Protections

= VIPer+

VIPer+

+ Technology

52

BCD6 controller technologyNEW

NEW

GND / SOURCE DRAIN

FB

DRAIN

CONT

VDD

BR

VIPER17CONT

VDD

FB

Out

CONTROL

On-Off

Gate

Sense

Tmp1

Gnd

SOURCE

Out

GndGnd1

Sense

Gate

On/Off

Tmp1

DRAIN

BR

800V Power MOSFET

+ Functionalities

Current mode converter with ADJUSTABLE IDLIM set point

Frequency

Fixed (60kHz or 115kHz) with JITTERING for EMI reduction

Quasi Resonant operation with Frequency Fold-back function (x5)

SOFT START UP: IDLIM increased cycle by cycle

BURST MODE in low load condition with IDLIM fixed

ADJUSTABLE IDLIM set point

STAND BY consumption < 50 mW

53

+ Protections

Over voltage protection (OVP)

2nd over current protection (2nd OCP)

Over load protection (OLP)

Over temperature protection + hysteresis (OTP)

Brown out protection

Max Duty Cycle: 70%

54

AUTO RESTART

MODE

after every fault

condition

55

VIPer37

VIPer25

VIPer17 VIPer27

VIPer35VIPer15

VIPer28 VIPer38

VIPer16 VIPer26VIPer06

SMPS topology and main applications

High features - Isolated Fly-backAuxiliary PS, STB, DVD, Games console, LCD TV,

major appliances, Motor control, Power Meter,

Chargers, Adapters, PC Stand-by

Quasi Resonant - Isolated Fly-backAuxiliary PS, STB, DVD, Games console, LCD TV,



Peak Power Isolated Fly-backDVD, Printer, ATX

Basic features – Isolated Fly-backAuxiliary PS, STB, DVD, Games console, LCD TV,



Non Isolated convertersHome appliances, Small appliances, Lighting, Power

meter

DIP7

SO16N

DIP7

SO16N

DIP7

SSO10SDIP10

1W……. …….15W(1) / 30W(2)

56

Brown out

Over Load Delay

PWM operations with settable IDLIM

Over Voltage

Over

Temperature

shut down

No auxiliary

Quasi ResonantFixed Frequency (60 or 115kHz) with

Jittering

Simplified

Non Isolated

loop

2° OCP

Feedback

disconnection

Extra Power

Timer

Burst Mode

Soft start

VIPer x7 VIPer x8

Brown out

VIPer x5 VIPer x6Basic features

Auto restart

Auto restart

(fixed time)

Main features

800VAvalanche Rugged

Fixed Frequency(301 or 60 or 115kHz)

with Jittering

Latched a

Feedback

disconnection(option only for VIPer06)

Latched OVP(option for VIPer25LLD)

(1) 30kHz available only for VIPer06

Trainings/VIPerx7_28EXT.ppt


Trainings/VIPerX5training.ppt

Trainings/VIPER16_26training.ppt

57

VIPer37

VIPer25

VIPer17 VIPer27

VIPer15

VIPer28

VIPer16 VIPer26VIPer06

24 7 30 3 1

HV Converter Portfolio + Roadmap

VIPer50VIPer22

VIPer20VIPer12 VIPer100 VIPer53

800 V

Av.Rug.

18 30 5.5 3 1 730V

620V

1 W (3)

6W(1) / 12W(2) 12W(1) / 24W(2)4W(1) / 8W(2) 15W(1) / 30W(2) 20W(1) / 35W(2) 30W(1) / 50W(2)

CTRL

VIPer x7

CTRL

VIPer x8

CTRL

VIPer x5

CTRL

VIPer x6

(1) Open frame, VIN = 85 - 264VAC ,

(2) Open frame, VIN = 230VAC ±20%,

(3) Achievable consumption at no load with Vin 264VAC

4.5

SSO10 & DIP7 SO16N & DIP7 SO16N & DIP7 SDIP10

under development, SOP planned within 2011

30 mW(3)

30 mW(3)

30 mW(3)

30 mW(3)


Trainings/VIPerX5training.ppt


Tools availability

DatasheetTraining

(slides)

Application

Notes

Evaluation

Boards

e-Design

StudioSpreadsheet Spice Model

VIPer17 Yes Yes Yes Yes Yes Yes Yes


VIPer37 Preliminary YesUnder

development

Under

development

Under

development

Under

development--

VIPer06 Preliminary YesUnder

development

Under

development

Under

development

Under

development--


VIPer26 Yes Yes Yes Yes Yes Yes --

VIPer15 Yes Yes Yes YesUnder

development

Under

development--

VIPer25 Yes Yes Yes YesUnder

developmentYes --

VIPer28 Yes Yes Yes Yes YesUnder

development

--

.

58

Evaluation Boards and ANs

59

VIPer 17 Order code Topology Input VAC Output Output Relevant AN Reference

VIPER17LN STEVAL-ISA058V1Isolated

Fly-back85-265 5W 5V / 1A AN2864 Stand-by PSU

VIPER17HN STEVAL-ISA060V1Isolated

Fly-back85-265 6W 12V / 0.5A AN2753 Stand-by PSU

VIPER17HN EVLVIP17-5WCHGIsolated

Fly-back90-265 5W 5V / 1A AN2840

Cell Phone

Battery Charger

VIPER17HN STEVAL-ILL017V1Isolated

Fly-back220 ±20% 3.5W 7V / 500mA AN2811 Led Driver

VIPER17HN STEVAL-ISA062V1Isolated

Fly-back85-265 5.5W

5V / 500mA

12V / 250mAAN2934 General Purpose

VIPER17HN EVLVIP27-7WLEDIsolated

Fly-back100-264 3.5W 10V / 350mA AN3212

High Power

Factor Led Driver


VIPER27LN EVLVIP27L-12WSIsolated

Fly-back85-265 12W 5V / 2.4A AN2929 Auxiliary PSU

VIPER27HN EVLVIP27H-12SBIsolated

Fly-back85-265 11W 5V / 2.2A AN3011 Auxiliary PSU

VIPER27HN EVLVIP27-7WLEDIsolated

Fly-back100-264 7W 10V / 750mA AN3212

High Power

Factor Led Driver


VIPER37xx TBDIsolated

Fly-back85-265 5V / 3A

VIPER37xx TBDIsolated

Fly-back85-265 12V / 1.3A


60


VIPER06LS

VIPER06HSUnder development

Non isolated

Fly-back85-265

12V / 300mA

option

( 5V /800mA)

TBD Home appliance

Under developmentIsolated

Fly-back85-265 TBD TBD Home Appliance


VIPER16LN STEVAL-ISA010V1Non isolated

buck converter85-500 1.8W

12V / 5V (post

reg.) / 150mAAN2872 Power Meter

VIPER16LN EVLVIP16L-4WFNNon Isolated

Fly-back85-265 4.5W 16V / 280mA

AN3028

draftHome appliance

VIPER16LN STEVAL-ISA071V1Non Isolated

Fly-back85-265 4W

- 5V / 400mA,

+7V / 160mAUM0920 Home appliance

VIPER16LN EVLVIP16L-5WFLIsolated

Fly-back85-265 5W 12 / 350mA databrief

Home appliance

Auxilairy PSU

VIPER16LD EVLVIP16LD-1W5 Non Isolated

buck converter85-265 1.8W

12V / 5V (post

reg.) / 150mAdatabrief

Small Home

Appliance

VIPER16HN EVLVIP16H-4WFNNon Isolated

Fly-back85-265 4.5W 16V / 280mA databrief Home appliance


VIPER26LD STEVAL-ISA081V1Primary

Regulation

Fly-back

85-265 12.5W 12V, 3.3V / 1A UM0984 Home appliance


61


VIPER15LN STEVALVIP15L-6W

Quasi-

Resonant

Isolated

Fly-back

90-265 VAC 6W 12V, 500mAAN3160

draftAuxiliary PSU

VIPER15LN EVLVIP15L-5WSB

Quasi-

Resonant

Isolated

Fly-back

90-265 VAC 5W 5V, 1A TBD Auxiliary PSU


VIPER25LN EVLVIP25L-10WSB

Quasi-

Resonant

Isolated

Fly-back

85-265 VAC 10W 5V, 2AAN3286

draft

Auxiliary PSU

STB

Power Meter


VIPER28LN EVLVIPER28L-10WIsolated

Fly-back85-265 VAC 12W 5V, 2.4A AN2950

Auxiliary PSU

Printer

62

VIPer06 / 16 /26

800V, avalanche rugged power MOSFET

PWM controller with drain current limit IDlim

Adjustable current limit,IDlim

Fixed frequency with Jittering

high performance for stand-by & efficiency

No need of auxiliary winding

Automatic auto restart after faults

Hysteretic thermal shutdown

Direct feedback for non isolated SMPS

Replacement of capacitive power supply

Open loop protection

Main Features

Main parametersMAIN PARAMETERS

Power MOSFET

(SuperMESH)

CONTROLLER

(BCD6S)

Break down voltage [V] 800

RDSon [Ohm] 30 /24 / 7

VDD [V] 9 ÷ 23

FOSC [KHz] 30 or 60 or 115

Max IDlim [mA] 420 / 740

RTHJ-A [°C/W] (1) 80

POUT [W]@ 85-265 VAC 4 / 6 / 12

(1) Package SO16N, 100mm2 of Cu

(2) Open Frame

GND

controller ground / power MOSFET Source

VDD

controller supply voltage / ICHARGE output current

LIM

Current limit set-up, IDlim .

FB

direct voltage feedback (in case of non isolated SMPS)

COMP

Compensation network.

Current loop feedback in case of isolated SMPS

N.A.

Not Available for user. (It can be connected to GND)

N.C.

Not Connected

Pin description

63

C6

R4

R2

+C1

C3 C4

R3

+

C5

D3L1

FB

DRAIN

GND VDDCOMP LIM

VIPER x6

D2

D1

+C2

R1

Controller

T1

GND

VOUT

+

-

Schematics with VIPerx6

FLY-BACK / Fixed Freq.

NON ISOLATED

Simplified feedback loopR3, R4

No Need auxiliary windingC4

Low cost EMI filterC1, C2, L1

Low cost clamp componentsR2,D2,C6

Default current limit400mA / 700mA

Short circuit protection

(automatic restart)

VIPer06 / 16 / 26



64

C6

R4

R2

+C1

C3 C4

R3

+

C5

D3L1

FB

DRAIN

GND VDDCOMP LIM

VIPER x6

D2

D1

+C2

R1

Controller

T1

GND

VOUT

+

-

FLY-BACK / FF

NON ISOLATED





Current limit set-up - RLIM

<400mA or <700mA


(automatic restart)RLIM

VIPer06 / 16 / 26



65

Stand-by optimization , 30 mWD4, R5

VOUT ≥ 12 V

FLY-BACK / FF

NON ISOLATED







(automatic restart)

C6

R4

R2

+C1

C3 C4

R3

+

C5

D3L1

FB

DRAIN

GND VDDCOMP LIM

VIPER x6

D2

D1

+C2

R1

Controller

T1

GND

VOUT

+

-

D4

R5

VIPer06 / 16 / 26

Feedback disconnection

(automatic restart)



C6

R4

R2

+C1

C3 C4

R3

+

C5

D3

L1

FB

DRAIN

GND VDDCOMP LIM

VIPER x6

D2

D1

GND

+C2

R1

AC INVOUT

Controller

T1

D4

R5

+

-

VOUT < 12 V

FLY-BACK / FF

NON ISOLATED


Need auxiliary windingC4 + AUX





(automatic restart)

VIPer06 / 16 / 26



(automatic restart)



C6

R4

R2

+C1

C3 C4

R3

+

C5

D3

L1

FB

DRAIN

GND VDDCOMP LIM

VIPER x6

D2

D1

GND

+C2

R1

AC INVOUT

Controller

T1

D4R5

+

-


(automatic restart)

No need the optocoupler

FLY-BACK / FF

PRIMARY REGULATION







(automatic restart)

VIPer06 / 16 / 26




68

VIPer06 / 16 / 26

IC3

R4

R4

IC2

C7

R3

C6R2

+C1

C3

C4

+

C5

D3

L1

FB

DRAIN

GND VDDCOMP LIM

VIPER x6

D2

D1

GND

+C2

R1

AC INVOUT

Controller

T1

D4R6

+

-

R5

C6

FLY-BACK / FF

ISOLATED

Minimum components count






(automatic restart)



69

IC3

R4

R4

IC2

C7

R3

C6R2

+C1

C3

C4

+

C5

D3

L1

FB

DRAIN

GND VDDCOMP LIM

VIPER x6

D2

D1

GND

+C2

R1

AC INVOUT

Controller

T1

D4R6

+

-

R5

C6


(automatic restart)

FLY-BACK / FF

ISOLATED







(automatic restart)

VIPer06 / 16 / 26

Stand-by optimization , 30 mWAUX + D4, R5


70

VIPer17 / 27 / 37

Main Features

Main parametersMAIN PARAMETERSPower MOSFET

(SuperMESH)

CONTROLLER

(BCD6S)


RDSon [Ohm] 24 / 7 / 4.5

VDD [V] 9 ÷ 23

FOSC [KHz] 60 or 115

Max IDlim [mA] 420 / 740 / 1050

RTHJ-A [°C/W] (1) 50

POUT [W] @ 85-265VAC 6 / 12 / 15

(1) Package SO16N and 100mm2 of Cu

(2) Open Frame


PWM controller with drain current limit, IDlim.

Adjustable current limit, IDlim

Fixed Frequency with Jittering

High performance for stand-by & efficiency

Integrated protections: OVP, OLP, high OCP

Automatic auto restart after fault


Brown-out: minimum input voltage is settable

Pin description

* BR pin has the position 10 for VIPER17LD/HD (SO16N package)

*

GND


VDD


CONT

OVP set-up, IDLIM set-up.

FB

current loop feedback

BR

brown out set-up

N.A.


N.C.

Not Connected

*


71

30mW Stand-by

FLY-BACK / FF

ISOLATED


Low cost EMI filterC1,C2, L1

Low cost clamp componentsR2,C6,D2

Short circuit protection No need ext components

2nd Over Current protectionNo need ext components

Default current limit400mA / 700mA / 1000mA

VIPer17 / 27 / 37

IC3

R4

R4

IC2

C7

R3

C6R2

C3

C4

+

C5

D3

VDD

DRAIN

GND FBBR CONT

VIPER x7

D2

GND

VOUT

Controller

T1

D4R6

R5

C6

+C1

L1

+C2AC IN

F

NTC



72







<400mA or <700mA or <1000mA

30mW Stand-by

RLIM

IC3

R4

R4

IC2

C7

R3

C6R2

C3

C4

+

C5

D3

VDD

DRAIN

GND FBBR CONT

VIPER x7

D2

GND

VOUT

Controller

T1

D4R6

R5

C6

+C1

L1

+C2AC IN

F

NTC

FLY-BACK / FF

ISOLATEDVIPer17 / 27 / 37



73

Over Voltage Protection (VOUT)RLIM , ROVP , DOVP







<400mA or <700mA or <1000mA

30mW Stand-by

RLIM

ROVP

DOVP

IC3

R4

R4

IC2

C7

R3

C6R2

C3

C4

+

C5

D3

VDD

DRAIN

GND FBBR CONT

VIPER x7

D2

GND

VOUT

Controller

T1

D4R6

R5

C6

+C1

L1

+C2AC IN

F

NTC

FLY-BACK / FF




74

Brown out set-up (VINDC)R7,R8, C6







30mW Stand-by

C6

R8

R7

IC3

R4

R4

IC2

C7

R3

C6R2

C3

C4

+

C5

D3

VDD

DRAIN

GND FBBR CONT

VIPER x7

D2

GND

VOUT

Controller

T1

D4R6

R5

C6

+C1

L1

+C2AC IN

F

NTC

FLY-BACK / FF




75








<400mA or <700mA or <1000mA

Brown out set-up (VINDC)R7,R8, C6

30mW Stand-by

RLIM

ROVP

DOVP

IC3

R4

R4

IC2

C7

R3

C6R2

C3

C4

+

C5

D3

VDD

DRAIN

GND FBBR CONT

VIPER x7

D2

GND

VOUT

Controller

T1

D4R6

R5

C6

+C1

L1

+C2AC IN

F

R7

R8

C6

NTC

FLY-BACK / FF



76

VIPer28

Main Features

Main parametersMAIN PARAMETERSPower MOSFET

(SuperMESH)

CONTROLLER

(BCD6S)


RDSon [Ohm] 7

VDD [V] 9 ÷ 23

FOSC [KHz] 60 or 115

Max IDlim [mA] 850

RTHJ-A [°C/W] (1) 50

POUT [W] @ 85-265VAC 12


(2) Open Frame

GND


VDD


COMP

OVP set-up, IDLIM set-up.

FB

current loop feedback

EPT

Extra Power Time set-up

N.A.


N.C.

Not Connected


PWM controller with drain current limit, IDlim.


Fixed Frequency with Jittering





Extra Power Management

Pin description


77

Extra Power TimerCEPT

FLY-BACK / FF

ISOLATED







30mW Stand-by

IC3

R4

R4

IC2

C7

R3

C6R2

C3

C4

+

C5

D3

VDD

DRAIN

GND FBEPT CONT

VIPER x8

D2

GND

VOUT

Controller

T1

D4R6

R5

C6

+C1

L1

+C2AC IN

F

CEPT

NTC

VIPer28


78

VIPer15 / 25

Main Features Pin description


Power MOSFET

(SuperMESH)

CONTROLLER

(BCD6S)


RDSon [Ohm] 24 / 7

VDD [V] 9 ÷ 23

FOSClim [KHz]up to 150 (L type)

up to 225 (H type)

Max IDlim [mA] 420 / 740

RTHJ-A [°C/W] (1) 80

POUT [W] @ 85-26 VAC 6 / 12

(1) Package SO16N, 100mm2 of Cu

(2) Open Frame


Quasi-Resonant PWM controller with drain current limit, IDlim.


Feed-Forward compensation





Brown-out: minimum input voltage is settable

GND


VDD


ZCD

Zero Current Detection, Feed-Forward set-up, OVP set-up, IDlim set point.

FB

Current loop feedback

BR

Brown out set-up

N.A.


N.C.

Not Connected

Schematics with VIPer x5

79

Feed-ForwardRFF


FLY-BACK / Quasi Res.

ISOLATED







≤400mA or ≤700mA or ≤1000mA

Zero current Detection (QR)RLIM , ROVP , DOVP, RFF

30mW Stand-by

IC3

R4

R4

IC2

C7

R3

C6R2

C3

C4

+

C5

D3

VDD

DRAIN

GND FBBR ZCD

VIPER x5

D2

GND

VOUT

Controller

T1

D4R6

R5

C6

RLIM

DOVP

ROVPRFF

+C1

L1

+C2AC IN

F

NTC

VIPer15 / 25


VIPER+ DETAILLE

80

2 Dies

Give flexibility to get the best technology for each

section

Power MOSFET in SuperMESH Technology

BCD6 controller technology

81

CONT

VDD

FB

Out

CONTROL

On-Off

Gate

Sense

Tmp1

Gnd

SOURCE

Out

GndGnd1

Sense

Gate

On/Off

Tmp1

DRAIN

BR/EPT

Power SECTION: 800V BVDSS

Leakage inductance contributes to the power

dissipation

82

PL=1/2LL(Ipk)2fSWVclamp/(Vclamp-Vfl)

Vindc

VDS

Vclamp

Vfl

tOff time On time

800V

High Vclamp reduces power loss

VDD pin (IC supply)

83

GND / SOURCE DRAIN

FB

DRAIN

CONT+~/ ZCD* / LIM^

VDD

VIPerx5*

Viper16^

VIPerx7+

VIPerx8~ BR*+ / EPT

~/ COMP^

VDD pin: What you can do?

To manage the power supply start-up

HV start up current generator & soft start

To keep alive the VIPer’s supply

wide range voltage

Viperx5, x7 & x8 (from 8.5V to 23V)

Viperx6 (from 11.5V to 23V)

To manage the power supply auto-restart

with special low restart current from the HV start up current

generator

To manage the Power supply turn-off

when VDD<8.5V and VDRAIN<80V, Viperx5, x7 & x8

when VDD<11.5V and VDRAIN<50V, Viperx6

84

GND / SOURCE DRAIN

FB

DRAIN

CONT

VDD

BR

Aux

winding

IDS_

CH

HV start up

VDD pin: IC turn-on & turn-off

VDD_ON

Fsw = 60 KHz

VDD(max

)

VDD_OF

F

VDD(restart)

Fsw = 0 KHz Fsw = 0 KHz

VDRAIN _START= 80V

VIN

VDD SOFT

START

VDD pin: IC auto-restart with fault

LOW controller consumptions LOW restart repetition rate

VDD_ON

Fsw = 0 KHz Fsw =

60 KHz

VDD(max

)

VDD_OF

F

VDD(restart)

Fsw = 0 KHz

IDS_CH =0.6 mA

Fsw =

60 KHzFsw

IDD_FAULT = 300 uA

IDD_OFF = 250 uA

VIN

SOFT START UP

Advantages :

Reduce the stress on the transformer

Improving of the VIPer and system and reliability

Soft start zone with

growing IDLIM valueSteady stateTransient

zone

t

t

IDLIM

8.5 ms

IDRAIN

VFBVFB_olp

VFB_lin

FB pin (Viperx5, x7 & x8 )

88

GND / SOURCE DRAIN

FB

DRAIN

CONT+~/ ZCD*

VDD

VIPerx5*

VIPerx7+

VIPerx8~

BR*+ / EPT~

FB pin: What you can do?

To make the current mode control loop

Error Amplifier Input

To fix the loop stability

Only in Viperx5, x7 & x8

To manage the Over Load Protection


To enter the Burst Mode


89

FB pin: IDRAIN versus VFB

90

IDLIM

IDRAIN

VFB

OVER LOADCURRENT MODE CONTROLBURST MODE

ID_BM

VFB_bm

drain current is

depending from

the load

OLPShut down

VFB_bm- VFB_bm_hysVFB_lin VFB_olp

FB pin: Current mode & loop stability

Linear range: VFB from VFB_bm +VFB_bm_hys to VFB_lin

CFB or CFB , RFB , CFB1 fixes the loop stability

91

CFB

FBR1

R2

Sense FET

+

-

PWM logicIFB

The optocoupler current and the

IFB current are depending from

the output load

The drain current is compared

with IFB in order to drive the PWM

CFB

CFB1RFB

FB pin: Over load protection

VFB ≥ VFB_lin , V max load has been reached and the FB voltage is

controlled

VFB = VFB_lin, 3uA current starts charging CFB

VFB = VFB_olp, Power section is switched off for over load after the

OLP delay

92

CFB

GND / SOURCE DRAIN

CONT

DRAIN

FB

VDD

BR

VIPERx5

VIPERx7

VIPERx83 A

VFB

VDSt

OLP delay

= A

VVC

linFBolpFB

FB3

__

VFB_olp

VFB_lin

FB pin: OLP delay, why?

IMMUNITY to over load NOISE during the normal operation

IMMUNITY to false OLP and incorrect switch off before the

converter’s steady state conditions

93

FB pin: Burst Mode working mode

94

VFB

IDS

t

t

ID_BM

Converter frequency reduction by packets operation

STAND-BY mode: less than 30 mW with optimezed psu design

VFB_bm- VFB_bm_hys

FB & COMP pin (Viperx6)

95

GND / SOURCE DRAIN

FB

DRAIN

LIM^

VDD

Viper16^

COMP^

FB & COMP (only for non isolated topology)

Fly-back non isolated

Buck

Buck-Boost

FB pin = EA input

COMP pin = EA output

FB pin takes the feedback directly from VOUT

FB voltage is compared with the EA reference

Loop is compensated by RCC to COMP pin

PWM is performed comparing the EA output (COMP) with sense FET.

96

FB & COMP (only for isolated smps)

Fly-back isolated with optocoupler

FB pin = GND => EA disabled

COMP pin takes the feedback from optocoupler

Loop is compensated by RCC to COMP pin

PWM is performed comparing the COMP signal with sense FET.

PWM dynamic VCOMPL – VCOMPH

V(COMP) < VCOMPL – 50mV => Burst Mode

V(COMP) > VCOMPH => Current Limited to IDlim

97

FB & COM: Burst Mode working mode

STAND-BY mode: less than 50 mW with optimezed psu

design

Activated when COMP voltage decreases

Low load

98

FB & COMP: Open loop failure protection

(with aux winding)

NON-ISOLATED If RUP is opened:

V(OUT) increases and then V(VDD) increases (coupled by aux winding)

I(DRAIN) = Idlim

VDD pin has inside a clamp:

If V(VDD) reaches the VDDclamp level and the injected current, IDD, exceeds the latch

threshold, IDDol, a fault signal is generated*

If RDOWN is opened:

V(OUT) is clamped to VREF_FB (3.3V typ)

99

ISOLATED If RUP is opened:

V(OUT) increases and then V(VDD) increases (coupled by aux winding)

I(DRAIN) = IDlim

VDD pin has inside a clamp: If V(VDD) reaches the VDDclamp level and the injected current, IDD, exceeds the latch threshold, IDDol, a fault signal is

generated*

If RDOWN is opened: V(OUT) is clamped to the voltage reference

FB & COMP: Open loop failure protection

(with aux winding)

100

CONT pin (Viperx7 & x8 )

101

GND / SOURCE DRAIN

FB

DRAIN

CONT+~

VDD

VIPerx7+

VIPerx8~

BR+ / EPT~

CONT pin: What you can do?

To choose the IDLIM level (RLIM)

To fix the Over Voltage Protection (RLIM & ROVP, DOVP)

102

Auxiliary

winding

ROVP

RLIM

DOVP

GND / SOURCE DRAIN

FB

DRAIN

CONT

VDD

BR / EPT

VIPERx7VIPERX8

CONT pin: IDLIM set point

Advantages :

Transformer optimization and accurate OLP.

Flexibility vs design changes

Flexibility vs different Projects (stock optimization)

103

RLIM

GND / SOURCE DRAIN

FB

DRAIN

CONT

VDD

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 20 40 60 80 100

RLIM [K ]

I DL

IM

(Norm

aliz

ed t

o I

DLIM

whitout

RLIM

)VIPERx7VIPERX8

BR / EPT

CONT pin: Over Voltage Protection

104

Auxiliary

winding

ROVP

RLIM

DOVP

GND / SOURCE DRAIN

FB

DRAIN

CONT

VDDVIPerx7VIPerx8

KRLIM 100

+

DOVPDSECOVP

SEC

AUX

OVPOVP

VVVoutN

N

VK

OVP

OVPLIMOVP

k

kRR

1 VCONT = VOVP= 3V

3 V

VCONT

VDS

KRLIM 50

or

BR / EPT

LIM pin (Viperx6)

105

GND / SOURCE DRAIN

FB

DRAIN

LIM^

VDD

Viper16^

COMP^

LIM pin: What you can do?

106

RLIM

GND / SOURCE DRAIN

FB

DRAIN

LIM

VDD

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 20 40 60 80 100

RLIM [K ]

I DL

IM

(Norm

aliz

ed t

o I

DLIM

whitout

RLIM

)

VIPERx6


RLIM>100 kOhm or pin float:

IDlim default (typ, 400mA)

RLIM< 80 kOhm:

IDlim decreased continuously according to the current

sunk from the LIM pin

ZCD pin (Viperx5)

107

GND / SOURCE DRAIN

FB

DRAIN

ZCD*

VDD

VIPerx5*

BR*+

ZCD pin: What you can do?

Transformer demagnetization Sensing (Zero Voltage Detection)


To fix the Over Voltage Protection (RLIM & ROVP, DOVP)

To have dynamic IDLIM Adjustment for almost constant maximum

power versus converter input voltage (Voltage Feed Forward

function)

108

Auxiliary

winding

ROVP

RLIM

DOVP

GND / SOURCE DRAIN

FB

DRAIN

ZCD

VDD

BR

VIPERx5

RFF

ZCD pin: IDLIM set point

Advantages :

Transformer optimization and accurate OLP.

Flexibility vs design changes

Flexibility vs different Projects (stock optimization)

109

RLIM

GND / SOURCE DRAIN

FB

DRAIN

ZCD

VDD

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 20 40 60 80 100

RLIM [K ]

I DL

IM

(Norm

aliz

ed t

o I

DLIM

whitout

RLIM

)

VIPERx5

BR

ZCD pin: Over Voltage Protection

110

Auxiliary

winding

ROVP

RLIM

DOVP

GND / SOURCE DRAIN

FB

DRAIN

ZCD

VDDVIPerx5

KRLIM 100

+

DOVPDSECOVP

SEC

AUX

OVPOVP

VVVoutN

N

VK

OVP

OVPLIMOVP

k

kRR

1 VCONT = VOVP= 3V

3 V

VCONT

VDS

KRLIM 50

or

BR

ZCD pin: Power MOSFET turn on

111

ZCD LOWER CLAMP

t

VDS

t

t

VZCD

t

VAUX

ARMING LEVEL

TRIGGER LEVEL

Turn on DELAY

IDRAIN

The Power MOSFET turn on is controlled by the ZCD pin. Turn off

Auxiliary

winding

ROVP

RLIM

DOVP

GND / SOURCE DRAIN

FB

DRAIN

ZCD

VDD

BR

VIPERx5

RFF

VZCD

VAUX

DEGMAGNETIZATION PHASE

Steady state operation

POWER Capability and switching frequency

In quasi resonant Flyback converter the

switching frequency changes with:

Input Voltage

Load

112

Where fT is:

Where fr is:

BR pin (IC supply)

113

GND / SOURCE DRAIN

FB

DRAIN

CONT+/ ZCD*

VDD VIPerx5*

VIPerx7+

BR*+

BR pin: What you can do?

To interdict the switching during low input voltage (VIN)

VIN(OFF) and VIN(ON) thresholds can be separately fixed by the

current hysteresis

Brownout protection input with hysteresis.

A voltage below the threshold VBRth shuts down (not latch) the

device and lowers the power consumption.

Device operation restarts as the voltage exceeds the threshold

VBRth + VBRhyst.

Advantages

Reduce the RMS current

Guaranty monotonic output voltage decreasing during the

converter turn off

114

BR pin: VIN(ON) & VIN(OFF)

115

BR

GND / SOURCE DRAIN

CONT / ZCD

DRAINVDD

FB

VIPERx5

VIPERx7R1

R2

VINDC

IBR_hyst

450 mV

VIN

VIN(ON)

VIN(OFF)

10 A

VBR

IBR_hyst

100 mV

FSW = 60 KHz FSW = 60 KHzFSW = 0 KHz

HYSH

L

LHHYSBRBRthONIN IR

R

RRVVV _

L

LHBRthOFFIN

R

RRVV

BR pin: To disable the Brown out

116

450 mV

100 mV

VIN

VIN(ON)

VIN(OFF)

15 A

VBR

IBR_hyst

Brown out

disable level

FSW = 60 KHz

BR

GND / SOURCE DRAIN

CONT /ZCD

DRAINVDD

FB

VIPERx5

VIPERx7

EPT pin (Viperx8 )

117

GND / SOURCE DRAIN

FB

DRAIN

CONT+~

VDD

VIPerx8~

EPT~

EPT pin: What you can do?

Give extra out power for programmed time

118

IDLIM = 750mA

IDLIM_EPT = 85% IDLIM =650mA

IDRAIN> IDLIM_EPT ;5 A charges CEPT and

Vout is regulated

VEPT(STOP)

VEPT(RESTART)

V (EPT)

Operations restarts here

GND DRAIN

FB

DRAIN

CONT

EPT

VIPerx8VDD

CEPT

5uA

2nd OCP - IC PROTECTION

Present in Viperx5, Viperx7 & Viperx8

To latch the power after extra drain current…, upper than IDLIM

Noise filter with latch after the 2nd event (i.e. during the ESD)

AUTOMATIC AUTORESTART after the 2nd OCP latch

Advantages

Protection from SHORT CIRCUIT in secondary diode

Protection from HEAVY TRANSFORMER SATURATIONS

System RELIABILITY

119

TBLANK

t

2nd OCP

IDRAIN

IDILM

ALTAIR & HVLED

Optoless Current & Voltage Controllers

120

Device objective – Standard configuration

Accurate CC-CV regulation

Need dedicated CV-CC regulator

Need secondary components and opto

Power dissipation on sense resistor

Expensive solution

121

ST - Proposed configuration

Control of output voltage and current entirely from

primary side

Save all secondary regulation components (voltage

reference, error amplifiers, optocoupler, sense resistor)

122

Technology

123

BCD6 controller technologyWith OTP (one time programmable) trimming

function available for the end user

ZCD/FB

VCC

COMP

Out

CONTROL

On-Off

Gate

Sense

SOURCE

Out

Gnd1

Sense

Gate

On/Off

DRAIN

IREF

800V Avalanche Ruggedness Power MOSFET

in SuperMESH Technology

CDC

GND

TR

IM

DA

TA

CL

OC

K

Main electrical parameters – HVLED805

Main Features


Power MOSFET

(SuperMESH)

CONTROLLER

(BCD6S)


RDSon [Ohm] 11

VDD [V] 11.5 ÷ 23

FOSC [KHz] Up to 166 kHz

Restart time during burst mode( 500us

RTHJ-A [°C/W] (1) 80

POUT [W] @ 85-265VAC 5


SOURCE

Power section Source

Vcc


GND

controller ground

ILED

Current loop reference

DMG

Zero Current Detection

COMP

Compensation network

DRAIN

Power section Drain

Pin description

800V, avalanche rugged power section

QR current-mode PWM controller in BCD6 technology

Constant voltage and constant current output regulation (CV/CC) with no optocoupler

Optimized for LED


Integrated protections: 2nd OCP, open loop protection (brownout) OLP, high OCP


SO16

Main electrical parameters – ALTAIR05T-800

Main Features


Power MOSFET

(SuperMESH)

CONTROLLER

(BCD6S)


RDSon [Ohm] 11

VDD [V] 11.5 ÷ 23


Restart time during burst mode(1) 500us

RTHJ-A [°C/W] (2) 80

POUT [W] @ 85-265VAC 6

(1) Also 125us, 250us and 1ms available


SOURCE


Vcc


GND

controller ground

IREF


ZCD/FB

Zero Current Detection, Cvregulation, FF compensation

COMP


CDC

Cable Drop Cpmplensation

DRAIN

Power section Drain

Pin description







N.A.

N.A. CDC

SOURCE DRAIN

SOURCE

GND

IREF

ZCD/FB

COMP

Vcc

DRAIN

DRAIN

DRAIN

N.A.

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

N.C.

N.A.

N.A. CDC

SOURCE DRAIN

SOURCE

GND

IREF

ZCD/FB

COMP

Vcc

DRAIN

DRAIN

DRAIN

DRAIN

DRAIN

N.A.

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

N.C.

SO16

Main electrical parameters – ALTAIR04-900

Main parameters

(1) Also 125us, 250us and 1ms available


SOURCE


Vcc


GND

controller ground

IREF


ZCD/FB

Zero Current Detection, Cvregulation, FF compensation

COMP


DRAIN

Power section Drain







SO16

Main Features Pin description

MAIN PARAMETERSPower MOSFET

(SuperMESH)

CONTROLLER

(BCD6S)


RDSon [Ohm] 16

VDD [V] 11.5 ÷ 23


Restart time during burst mode(1) 500us

RTHJ-A [°C/W] (2) 50

POUT [W] @ 85-265VAC 5

N.C.

N.C.N.C.

SOURCE DRAIN

SOURCE

GND

IREF

ZCD/FB

COMP

Vcc

DRAIN

DRAIN

DRAIN

N.C.

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

N.C.

N.C.

N.C.N.C.

SOURCE DRAIN

SOURCE

GND

IREF

ZCD/FB

COMP

Vcc

DRAIN

DRAIN

DRAIN

DRAIN

DRAIN

N.C.

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

N.C.

Typical load regulation cv/cc: high accuracy

127

0 200 400 600 800 1000 1200

0

1

2

3

4

5

6

Ou

tpu

t V

oltag

e [V

]

Output Current [mA]

HV Startup is ON

High current accuracy:

+/-5%

High voltage accuracy

+/-2.5%

CV Mode – Principe of operations

Vaux

GND

An accurate image of the output voltage can be obtained by sampling the voltage of the auxiliary winding right at the end of transformer’s demagnetization. We use our proprietary technique to do the job.

CC Mode – Principe of operations

t

t

t

t

IP

Is

Q

IC

T

REFI

R

VI

CCREF

REFI

I REFOUT

SENSE

R In

2 R

Valid in DCM only

Iout not depend on either Vin, Vout or Fsw

Layout Recommendations

Viper Family

Layout Rules

Some simple rules insure a correct running of

switching power supplies. They may be classified

into two categories:

To minimize power loops

Split low level signals and power

Thermal management is important too, consider:

Copper in Drain pin for thermal dissipation

Helps for instantaneous thermal peaks

Dissipates heat from Drain

131

Layout Rules

To minimize power loops:

The way the switched power current must be carefully analyzed

and the corresponding paths must present the smallest possible

inner loop area. This avoids radiated EMC noises, conducted

EMC noises by magnetic coupling, and provides a better

efficiency by eliminating parasitic inductances, especially on

secondary side.

To use different tracks for low level signals and power

ones.

The interferences due to a mixing of signal and power may result

in instabilities and/or anomalous behavior of the device in case of

violent power surge (Input overvoltages, output short circuits...).

132

Viper Loops

In case of VIPer, these rules apply as shown:

Loops that must be minimized:

C1-T1-U1

C5-D2-T1

C7-D1-T1

C6 must be as close as possible to T1

C2, ISO1, C3 and C4 use a dedicated track to be

connected directly to the source of the device

133

Viper Loops

134

Viper Loops Analysis

Schematic for Loop Analysis

135

Loop Analysis

Layout for Loop Analysis

136

Loop A, High Voltage

137

Loop B, Low Signals

138

Loop C, Small signal GND

139

Loop D, Output

140

Y Capacitor, Primary & Secondary

141

As close as possible to Transformer

e-DESIGN

142

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