WS9442P [ETC]

Non-isolated Buck Offline LED Driver;


型号：	WS9442P
厂家：	ETC
描述：	Non-isolated Buck Offline LED Driver
文件：	总9页 (文件大小：852K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

WS9442P Product Description

Non-isolated Buck Offline LED Driver

Features

Description



Critical Conduction Mode Operation

Internal 500V Power MOSFET

Gate Drive and No Auxiliary Winding

±3% LED Current Accuracy

Efficiency up to 93%

The WS9442P 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 WS9442P 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 simplify design and reduce cost.

LED Short Circuit Protection

LED Open Circuit Protection



Current Sense Resistor Short Protection

Thermal Regulation Function

External PWM Dimming

The WS9442P adopts intelligent temperature control and

thoroughly solves the problem of LED flickering under high

temperature. It integrates an external dimming pin which inputs

PWM signal and can dim by changing the duty cycle of the PWM

signal. The WS9442P offers full protection functions to improve

the system reliability, including LED open circuit protection, LED

short circuit protection, CS resistor short circuit protection and

Applications



LED Bulb Lights

LED Panel Lights

LED Strings

thermal regulation function.

The WS9442P is available in DIP-7 Package.

Typical Application Circuit

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WS9442P ^{Product Description}

Pin Configuration and Marking Information

The WS9442P is available in DIP-7 Package. The top marking is shown as below:

WS9442PD7P：Product Code

A：Product Code

X：Internal Code

BCY：Internal Code For QC

YMX：D/C

Pin Definition

Pin No.

Description

Name

GND

Ground

ROVP

DIM

Over Voltage Protection Setting Pin. Connect a resistor to GND

Dinmming Pin.Must be floated when not in use.

Power Supply Pin

VCC

5,6

DRAIN

Internal HV Power MOSFET Drain

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

pin.

Block Diagram

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WS9442P ^{Product Description}

Ordering Information

Package

Marking

Part Number

7-Pin DIP-7, Pb-free

WS9442PD7P

Recommended Operation Conditions

Part Number

Package

Input voltage

Maximum output power

120V/280mA

160V/220mA

175VAC-264VAC

90VAC-264VAC

WS9442PD7P

DIP7

80V/300mA

Absolute Maximum Ratings

Symbol

V_DS

Parameter

Range

-0.3~500

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

0.9

P_DMAX

T_J

Power dissipation DIP7

Maximum operating junction temperature

Minimum/Maximum Storage temperature

150

℃

T_STG

-55~150

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

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WS9442P ^{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 Start-up 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

Toff_min

Ton_max

Minimum OFF Time

310

4.5

Maximum OFF Time

Maximum On Time

Rovp=70k

100

DIM Dimming Section

DIM Square Wave High

VH_DIM

400

Level

DIM Square Wave Low

Level

VL_DIM

-300

0.1

KHZ

DIM Square Signal

Frequency

f_DIM

0.5

MOSFET Section

Rds_on

Static Drain-source

On-State Resistance

Drain-Source Breakdown

Voltage

Vgs=15V,Ids=0.5A

Vgs=0V,Ids=250uA

Vgs=0V,Vds=500V

6.8

BVdss

Idss

500

Drain-Source Leakage

Current

Thermal Regulation Section

Thermal Regulation

TREG

150

℃

Temperature

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WS9442P Product Description

Function Description

The WS9442P is a high performance non-isolated buck

converter specially designed for LED lighting. The device

adopted in WS9442P, the CS pin is connected to the current

sense 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

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.

blanking time.

The peak inductor current is calculated by the equation:

400

I_PK



(mA)

R_CS

Start Up

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 WS9442P 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.

Where, Rcs is the current sense resistor value.

The current in LED can be calculated by the equation:

I_PK

I_LED



(mA)

Where, IPK is the peak current of the inductor.

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:

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



 820K

I_{ST _ MAX}

300

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

VCC Capacitor Selection

Input Buck 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 capacitor design can be calculated by the

following empirical equations:

A 1uF 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 temperature. Due to external damage

resulted from small volume and brittle texture of MLCC, the

Vcc is easy to leakage currents, which will make the

WS9442P unable to start. Strict control measures are taken

in its layout and productive process.

90Vac~264Vac: 1W output uses1uF buck electrolytic

capacitor;

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

capacitor.

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 WS9442P utilizes proprietary current control

method. It can achieve precise LED output current with a few

external components. Cycle by Cycle current sense is

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WS9442P ^{Product Description}

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 WS9442P 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.

External PWM Dimming

The WS9442P integrates an external dimming pin which

inputs PWM signal and can dim by changing the duty cycle

of the PWM signal. The testing dimmable curve of a

120V/260mA driver under 175~264Vac application is shown

as below:

Thermal Regulation

The WS9442P integrates thermal regulation function.

When the system is under higher temperature, the output

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 at 150℃ internally.

The duty cycle of the PWM signal

Inductor Selection

The WS9442P 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

The over voltage protection of the WS9442P can be

programmed by the ROVP pin resistor. The ROVP pin voltage

is 0.5V.

L  I_PK

t_on

V_INV_LED

Where,

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:

L is the inductance value,

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 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

Where，

L I_PK

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:

V_LED

The inductance can be calculated by the equation:

V_LED(V_INV_LED

f  I_PKV_IN

)

L 

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WS9442P ^{Product Description}

Rovp  120  7.67 * Tovp *10 ⁶^（KΩ）

PCB Layout

It is suggested that the open circuit protection voltage is

set at or above 1.5 times maximum load voltage.

The following rules should be followed in WS9442P PCB

layout:

VCC Capacitor: The VCC capacitor should be as close

Protection Function

as possible to the VCC Pin and GND pin.

The WS9442P offers full 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 turn-off 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.

After the system enters into faulty condition, the VCC

voltage will decrease until it reaches the UVLO threshold,

then 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.

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

from the interference.

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.

Line Voltage Compensation

The WS9442P integrates line voltage compensation

function, which makes LED current remain unchanged in the

range of full voltage with good line regulation and current

accuracy.

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WS9442P Product Description

DIP7 Package Dimension

Winsemi

Max

Dimensions in Millimeters

Dimensions in Inches

Symbol

Min

Max

9.00

6.10

3.0

9.50

6.60

3.4

0.354

0.240

0.118

0.058

0.016

0.096

0.374

0.260

0.134

0.062

0.021

0.104

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

0.32

7.62TYP

0.3TYP

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WS9442P ^{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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WS9442P [ETC]

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