WS9256_技术文档

WS9256ProductDescription

High Precision PSR Constant Current LED Driver

Features

Description



Built-in 650V Power MOSFET

The WS9256 is a high precision primary-side

Constant current control without secondary sense and

feedback circuit.

feedback and regulation controller for LED lighting, it

operates in constant current control mode and is designed

to work in inductor current discontinuous conduction mode

and extremely suitable for flyback convertor under

universal input, the output power of system should be less

than 24W.



±3% LED current accuracy

Ultra low operating current to improve efficiency

High resistance feedback resistor to improve efficiency

Universal input voltage

LED short and open circuit protection

VCC under-voltage protection

The WS9256 integrates 650V power MOSFET. Since

adopting primary sense and feedback control technology,

the secondary sense and feedback circuit is eliminated.

The loop compensation components are also removed

while maintaining stability overall operating conditions. The

low component counts and low BOM cost are realized.

Since using the proprietary high accurate current

sense method, the WS9256 realizes ±3% accuracy of LED

current along with excellent line regulation and load

regulation.

Feedback loop short circuit protection

Current sense resistor open circuit protection

Over temperature protection

No external loop compensation component required

Available in DIP-7 package

Applications



LED bulb light

Other LED lighting

The WS9256 offers rich protection functions including

LED short circuit protection, LED open circuit protection,

die over-temperature protection, VCC over voltage

protection, VCC under voltage protection and FB short

circuit protection. All the protection features are

auto-recovery.

Typical Application

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WS9256^{ProductDescription}

Pin Configuration and Marking Information

WS9256 is offered in DIP7 package, as bellows:

WS9256D7P

A：Product Code

X：Internal Code

BCY：Internal Code For QC

YMX：D/C

Pin Definition

Pin No.

Pin Name

GND

Function Description

1

2

Ground.

Feedback. This pin detects the output information from auxiliary winding.

Power suppl.

FB

3

4

VCC

CS

Current sense. This pin connects a current sense resistor to GND to detect

the primary current of transformer.

5,6

7

Drain

NC

Internal high voltage MOSFET drain.

No connection, must be floated.

Internal Block Diagram

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WS9256^{ProductDescription}

Ordering Information

Package

Marking

Part Number

7-Pin DIP-7, Pb-free

WS9256D7P

Recommended Operation Conditions

Symbol

Parameter

Maximumworking frequency

Value

Unit

Fmax

TA

100

-20~85

10~17.5

<30

khz

℃

V

Operation temperature

Power supply voltage

VCC

POUT1

POUT2

Output power(Input voltage230V±15%)

Output power(Input voltage85V～265V)

W

<24

Absolute Maximum Ratings (Note1)

symbol

paramete

limites

unit

VCC

VCC pin input voltage

-0.3~20

-0.3~6

-0.3~650

-0.3~6

0.9

V

FB

Drain

CS

Feedback pin input voltage

Internal MOSFET drain voltage

Current sense pin input voltage

Power dissipation (note2)

V

PDMAX

Tjo

W

Operating junction temperature

Thermal resistance (Junction to Ambient)

Storage temperature range

-40~150

80

℃

℃/W

℃

θJA

TSTG

-55~150

Note 1: Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. Under

“recommended operating conditions” the device operation is assured, but some particular parameter may not be achieved.

The electrical characteristics table defines the operation range of the device, the electrical characteristics is assured on DC and

AC voltage by test program. For the parameters without minimum and maximum value in the EC table, the typical value defines

the operation range, the accuracy is not guaranteed by spec.

Note 2: The maximum power dissipation decrease if temperature rise, it is decided by TJMAX, θ JA, and environment

temperature (TA). The maximum power dissipation is the lower one between PDMAX = (TJMAX - TA)/ θJA and the number

listed in the maximum table.

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WS9256^{ProductDescription}

Electrical Characteristics (Unless otherwise specified, VCC=8V and TA =25 ℃)

Symbol

Parameter

Test condition

Min

Typ

Max

Units

Supply Voltage Section

VDD_CLAMP

UVLO_on

VDD Clamping Voltage

4mA

17.4

16.1

18.3

17.1

19.4

18.1

V

VDD Power Supply

VDD Under Voltage

Lockout

UVLO_off

VCC_OVP

8.5

9

9 .5

V

VCCover voltage

protection level

Start up current

Operating current

17.9

18.9

19.9

Ist

35

uA

Iop

152

Current Sense Section

Ipp

Primary Peak Current

484

508

500

200

42

531

mV

ns

%

T_LEB

Lead Edge Blanking

Shutdown Delay

T_DELAY

D_max

Maximum Duty Cycle

FeedbackInputSection

MaximumDemagnetization

Toff_max

420

4

us

time

MinimumDemagnetizationt

ime

Toff_min

Ton_max

MaxmiumON time

100

1

us

V

Vfb

FB voltage sense level

Power MOSFET

Drain-source leakage

current

Idss

Vgs=0V,Vds=650V

10

uA

V

Drain-source breakdown

voltage

BVdss

Ron

650

Static drain-source

on-resistance

2.8

3.5

Ω

Over TemperatureProtection

Thermal Regulation

Temperature

T_comp

147

℃

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WS9256ProductDescription

Application Information

The ratio of FB upper resistor to lower resistor is

recommended to about 4.0. The FB upper resistor can be

set to 300KΩ~750KΩ to improve efficiency of convertor.

The WS9256 is a high performance power switch

specially designed for LED lighting, it uses the patent

constant current control technology of WINSEMI. The

WS9256 integrates a 650V power MOSFET. The accurate

LED current can be realized without opto-coupler and TL431

feedback circuit while minimizing the external component

count, lowering the total bill of material cost.

Operation Switching Frequency

The WS9256 is designed to work in discontinuous

conduction mode and no external loop compensation

component is required while maintaining stability. The

maximum duty cycle is limited to 42%. The maximum

switching frequency should be set to less than 100KHz and

the minimum switching frequency should be set to more

than 20KHz. The maximum and minimum switching

frequency is limited in WS9256 to ensure the stability of

system.

Start Up

The VCC capacitor will be charged through the start-up

resistor when the system is powered on, once the voltage

on VCC reaches the start-up threshold, the WS9256 will

start to operate, and then the VCC is supplied by the

auxiliary winding.

The switching frequency can be set by the formula:

Np²V_LED

f 

8 Ns² Lp I_LED

Constant Current Control

Cycle-by-Cycle current sense is offered in WS9256, the

CS is connected to the current sense comparator, and the

voltage on CS will be compared with the internal 508mV

reference voltage, the MOSFET will be switched off when

the voltage on CS reaches the threshold. The output of the

comparator also includes a 500nS leading edge blanking

time

Where, LP is the primary winding inductance of

transformer.

Protection Function

The WS9256 has several protection functions. The

internal MOSFET will be shut down immediately when the

voltage on VCC reaches the threshold of OVP and the

device will not recover until the protection condition is

removed. A 18V zener diode is designed in the WS9256 to

prevent the chip damage from the abnormal situation.

The thermal protection circuitry in the WS9256 senses

the die temperature after start up, and the thermal protection

threshold is set to 147℃

The primary peak current is given by:

508

I_{P_PK}



(mA)

R_CS

The current in LED can be calculated by the equation:

I_{P_PK}

N_P

N_S

I_OUT





4

The system will work in low consumption mode when

the output LED short circuit or open circuit is detected.

While the WS9256 continuous to detect output status until

the LED recover to normal condition, and then the device

will be operate in normal mode.

Where,

NP: primary winding turns of transformer

NS: secondary winding turns of transformer

IP_PK: peak current in MOSFET

Feedback Network

PCB Layout

The WS9256 senses the output information through the

feedback network and the FB threshold voltage is set to 1V.

The following rules should be followed in WS9256 PCB

layout:

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WS9256ProductDescription

Bypass Capacitor

NC Pin

The bypass capacitor on VCC should be as close as

possible to the VCC pin

The NC pin must be left floating to satisfy the

requirement of creepage distance.

Ground Path

Drain pin

The power ground path for current sense should be

short, and the power ground path should be separated from

small signal ground path before the negative of the bulk

capacitor.

To increase the copper area of drain for thermal

consideration.

FB Pin

The feedback divider should be as close as possible to

FB Pin and the node must keep away from dynamic node of

transformer.

The Area of Power Loop

The area of main current loop should be as small as

possible to reduce EMI radiation, such as the primary

current loop, the snubber circuit and the secondary

rectifying loop.

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WS9256ProductDescription

Package Information

DIP7 Package Outline Dimensions

Winsemi

Dimensions in Millimeters

Dimensions in Inches

Symbol

Min

9.00

6.10

3.0

Max

9.50

6.60

3.4

Min

Max

A

0.354

0.240

0.118

0.058

0.016

0.096

0.374

0.260

0.134

0.062

0.021

0.104

B

C

A1

A2

A3

A4

A5

C1

C2

C3

C4

D

1.474

0.41

2.44

1.574

0.53

2.64

0.51TYP

0.99TYP

0.02TYP

0.04TYP

6.6

7.30

0.260

0.287

0.50TYP

0.02TYP

3.00

1.47

7.62

0.24

3.40

1.65

9.3

0.118

0.058

0.300

0.009

0.134

0.065

0.366

0.013

D1

D2

0.32

7.62TYP

0.3TYP

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WS9256ProductDescription

NOTE:

1.We strongly recommend customers check carefully on the trademark when buying our product, if there is

any question, please don't be hesitate to contact us.

2.Please do not exceed the absolute maximum ratings of the device when circuit designing.

3.Winsemi Microelectronics Co., Ltd reserved the right to make changes in this specification sheet and is

subject to change without prior notice.

CONTACT:

Winsemi Microelectronics Co., Ltd.

ADD:Futian District, ShenZhen Tian An Cyber Tech Plaza two East Wing 1002

Post Code : 518040

Tel : +86-755-8250 6288

FAX : +86-755-8250 6299

Web Site : www.winsemi.com

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www.winsemi.com Tel : +86-755-8250 6288

Fax : +86-755-8250 6299

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型号：	WS9256
厂家：	ETC
描述：	High Precision PSR Constant Current LED Driver
文件：	总8页 (文件大小：680K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

WS9256 [ETC]

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