WS9441S7P [ETC]

Non-isolated BuckOffline LED Driver;


型号：	WS9441S7P
厂家：	ETC
描述：	Non-isolated BuckOffline LED Driver
文件：	总9页 (文件大小：404K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

WS9441 Product Description

Non-isolated BuckOffline LED Driver

Features



Critical Conduction Mode Operation

Internal 500V Power MOSFET

Gate Drive and No Auxiliary Winding

±3% LED Current Accuracy

Efficiency up to 93%

Description

The WS9441 is a high precision buck constant current LED

driver and is applied to non-isolated buck LED power system with

AC input voltage of 85VAC-265VAC. The WS9441 integrates a

500V power MOSFET, and can achieve excellent constant current

performance with very few external components, so the system

cost and size are minimized. The driver operates in critical

conduction mode, and the output current does not change with the

inductance and LED output voltage. The operating current of the

IC is 200uA, so it doesn’t need the auxiliary winding for supplying

the chip, thus simplifying design and reducing cost.

LED Short Circuit Protection

LED Open Circuit Protection



Current Sense Resistor Short Protection

Thermal Regulation Function

Applications

The WS9441 adopts intelligent temperature control and

thoroughly solves the problem of light flashing at high

temperatures. The WS9441 offers full protection functions to

improve the system reliability, including LED open circuit

protection, LED short circuit protection, CS resistor short circuit



LED Bulb Lights

LED Panel Lights

LED Strings

protection and thermal regulation function.

The WS9441 is available in SOP-7 Package.

Typical Application Circuit

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WS9441 ^{Product Description}

Pin Configuration and Marking Information

The WS9441 is available in SOP-7 Package. The top marking is shown as below:

Pin Definition

Pin No.

Description

Name

GND

Ground

ROVP

Over Voltage Protection Setting Pin. Connect a resistor to GND

No Connection.Should be hanged out.

Power Supply Pin

VCC

5,6

DRAIN

Internal HV Power MOSFET Drain

Current Sense Pin. Connect a sense resistor between this pin and GND

pin.

Block Diagram

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WS9441 ^{Product Description}

Ordering Information

Package

Marking

Part Number

7-Pin DIP-7, Pb-free

WS9441S7P

Recommended Operation Conditions

Part Number

Package

Input voltage

Maximum output power

150V/120mA

80V/200mA

WS9441S7P

SOP7

175VAC-264VAC

Absolute Maximum Ratings

Symbol

V_DS

Parameter

Range

-0.3~500

2.5

Unit

Internal HV MOSFET drain voltage

VCC pin maximum sink current

I_{CC_MAX}

V_ROVP

V_CS

LED open circuit protection voltage regulation

Current sense pin input voltage

-0.3~7

-0.3~8

-0.3~7

0.9

P_DMAX

T_J

Power dissipation SOP7

Maximum operating junction temperature

Minimum/Maximum Storage temperature

℃

T_STG

150

Note：Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device

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WS9441 ^{Product Description}

Electrical Characteristics (Unless otherwise specified, VCC=15V and TA =25 ℃)

Symbol

Parameter

Conditions

Min

Typ

Max

Units

Supply Voltage Section

VCC_CLAMP

UVLO_on

VCC Clamp Voltage

Chip Startup Voltage

VDD Under voltage

protection

10mA

17.8

18.8

19.8

16.2

UVLO_off

9.5

Ist

Startup Current

VCC= 13V

150

100

220

170

300

250

Iop

Operating Current

Fop=70KHz

Current Sense Section

Threshold Voltage for

Vcs_th

390

400

410

Peak Current Limit

Leading Edge Blanking

Time for Current Sense

TLEB

350

200

TDELAY

Switch Off Delay Time

Internal Time Control Section

Toff_max

Minimum OFF Time

310

4.5

Toff_min

Maximum OFF Time

Maximum On Time

Rovp=70k

Ton_max

100

MOSFET Section

Static Drain-source

On-State Resistance

Drain-Source Breakdown

Voltage

Rds_on

BVdss

Idss

Vgs=15V,Ids=0.5A

Vgs=0V,Ids=250uA

Vgs=0V,Vds=500V

500

Drain-Source Leakage

Current

Thermal Regulation Section

Thermal Regulation

T^REG

150

℃

Temperature

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WS9441 Product Description

Function Description

The WS9441 is a high performance non-isolated buck

converter specially designed for LED lighting. The device

comparator, and the voltage on CS pin is compared with the

internal 400mV reference voltage. The MOSFET will be

switched off when the voltage on CS pin reaches the threshold.

The CS comparator includes a 350ns leading edge blanking

integrates

a 500V power MOSFET. With the help of

advanced constant current control and gate drive technology,

the converter achieves excellent constant current

performance with very few external components. It does not

need auxiliary winding for powering the IC or voltage sensing,

hence the system size and cost is greatly reduced.

time.

The peak inductor current is calculated by the equation:

400

I_PK



(mA)

R_CS

Start Up

Where, RCS is the current sense resistor value.

After system powered on, the VCC pin capacitor is

charged up by the start up resistor. When the VCC pin

voltage reaches the turn on threshold, the internal circuits

start operating. The WS9441 integrates a 17V ZENER diode

to clamp the VCC voltage. Due to the ultra-low operating

current, the auxiliary winding is not needed to supply the IC.

The typical value of the start-up current is 200uA (the

maximum value is 300uA). For the application of 176VAC—

264VAC, the start-up resistor can be calculated by the

equation:

The current in LED can be calculated by the equation:

I_PK

I_LED



(mA)

Where, IPK is the peak current of the inductor.

Freewheeling Diode

The diode will bear the reverse voltage equal to the

input voltage when the MOSFET is on. A 600V diode was

suggested to use. Besides, the operating frequency of

freewheeling diode is from 20K to 120 KHz, such ultra fast

recovery diodes as ES and ER whose Trr is less than 50ns are

good choice.

V_{IN _ MIN}1.414

1761.414

R_ST





 910K

I_{ST _ MAX}

270

Two resistors in 1206 size SMD can be used in series.

VCC Capacitor Selection

Input Electrolytic Capacitor

The Vcc capacitor is used to bypass noise to IC, so that

to assure its stable operation, and should be as close as

possible to the chip.

Input voltage should be considered in to the capacitor

pressure, and the common value is 400V.

In general, the capacity design can be calculated by the

following empirical equations:

A 1uF or above capacitor can be used in Vcc. If

selecting MLCC, the material of X7R will be used to satisfy

the stability of the capacity under high temperatures. Due to

external damage resulted from small volume and brittle

texture of MLCC, the Vcc is easy to leakage currents, which

will make the WS9441 unable to start. Strict control

measures are taken in its layout and productive process.

90Vac~264Vac: 1W output uses1uF

capacitor;

176Vac~264Vac: 1W output uses 0.5uF buck electrolytic

capacitor.

buck electrolytic

Output Capacitor

Electrolytic capacitor is recommended to be used. Its

stable capacitance can improve the efficiency of power supply,

the LED ripple current and luminous efficiency.

Vovp voltage should be considered in output capacitor

pressure.

Constant Current Control

The WS9441 utilizes proprietary current control method.

It can achieve precise LED output current with a few external

components. Cycle by Cycle current sense is adopted in

WS9441, the CS pin is connected to the current sense

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WS9441 ^{Product Description}

Inductor Selection

current is gradually reduced; the output power and thermal

dissipation are also reduced. The system temperature is

regulated and the system reliability is improved. The thermal

regulation temperature is set to 150℃ internally.

The WS9441 works in

a inductor critical current

conduction mode. When the power MOFET is switched on,

the current in the inductor rises up from zero. The on time of

the MOSFET can be calculated by the equation:

Over Voltage Protection

L  I_PK

t_on

The over voltage protection of the WS9441 can be

programmed by the ROVP pin resistor. The ROVP pin voltage

is 0.5V.

V_INV_LED

Where,

L is the inductance value,

When the LED is open circuit, the period of the output

voltage increases gradually, the demagnetization time gets

shorter. The demagnetization time at OVP---- Tovp can be

calculated by the open circuit protection voltage by the

equation:

IPK is the peak current of the inductor,

VIN is the DC bus voltage after the rectifier bridge,

VLED is the voltage on the LED.

After the power MOSFET is also switched off and the

current in the inductor decreases. When the inductor current

reaches zero, the power MOSFET is turned on again by IC

internal logic. The off time of the MOSFET is given by the

equation:

L  V_CS

Tovp 

R_CS V_OVP

L I_PK

V_LED

Where，

t_off



Vcs is the CS pin turn off threshold (0.4V);

Vovp is the open circuit protection voltage.

And then the Rovp resistor value can be calculated by the

equation:

The inductance can be calculated by the equation:

V_LED(V_INV_LED

f  I_PKV_IN

)

L 

Rovp  120  7.67 * Tovp *10 ⁶^（KΩ）

Where, f is the maximum system switching frequency,

which is proportional to the input voltage. So the minimum

switching frequency is set at lowest input voltage, and the

maximum switching frequency is set at highest input voltage.

The minimum and maximum off time of WS9441 is set at

4.5us and 310us, respectively. Referring to the equation of

Toff calculation, if the inductance is too small, the Toff may be

smaller than the minimum off time, the system will operate in

discontinuous conduction mode and the output current will

be smaller than the designed value. If the inductance is too

large, the Toff may be larger than the maximum off time, the

system will operate in continuous conduction mode and the

output current will be higher than the designed value. So it is

important to choose a proper inductance.

It is suggested that the open circuit protection voltage is

set at or above 1.5 times maximum load voltage.

Protection Function

The WS9441 offers rich protection functions to improve

the system reliability, including LED open/short protection, CS

resistor short protection, VCC under voltage protection,

thermal regulation. When the LED is open circuit, the system

will trigger the over voltage protection and stop switching.

When the LED short circuit is detected, the system works at

low frequency and the CS pin turnoff threshold is reduced. So

the system power consumption is very low. At some abnormal

fault condition, such as CS resistor shorted or inductor

saturation, the internal fast fault detection circuit will be

triggered, the system stops switching immediately.

Thermal Regulation

The WS9441 integrates thermal regulation function.

When the system is under higher temperature, the output

After the system enters into faulty condition, the VCC

voltage will decrease until it reaches the UVLO threshold, then

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WS9441 ^{Product Description}

the system will restart again. If the fault condition is removed,

the system will recover to normal operation.

Ground Path: The power ground path for current sense

resistor should be short, and the power ground path should be

separated from small signal ground path before connecting to

the negative node of the bulk capacitor.

Line Voltage Compensation

The WS9441 integrates line voltage compensation

function, which makes LED current remain unchanged in the

range of full voltage with good line regulation and current

accuracy.

The Area of Power Loop: The area of main current loop

should be as small as possible to reduce EMI radiation. And it

should be away from diodes and other heating components.

ROVP PIN: The ROVP resistor should be as close as

possible to the ROVP Pin to increase its resistance to prevent

PCB Layout

from the interference.

The following rules should be followed in WS9441 PCB

layout:

DRAIN PIN: The copper area of DRAIN pin can be

increased for better thermal dissipation. And it should be away

from CS/VCC and ROVP Pin.

VCC Capacitor: The VCC capacitor should be as close

as possible to the VCC Pin and GND pin.

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WS9441 Product Description

SOP7 Package Dimension

Winsemi

Dimensions in Millimeters

Dimensions in Inches

Min

Symbol

Min

4.70

3.70

1.30

0.35

Max

5.10

4.10

1.50

0.48

Max

0.201

0.161

0.059

0.019

0.185

0.146

0.051

0.014

1.27TYP

0.05TYP

0.345TYP

0.014TYP

5.80

6.20

0.228

0.244

5.00TYP

0.197TYP

0.55

0.05

0.70

0.022

0.002

0.028

0.009

0.225

0.203TYP

1.05TYP

0.008TYP

0.041TYP

0.40

0.80

0.016

0.031

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WS9441 ^{Product Description}

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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WS9441S7P [ETC]

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