WS9441 datasheet(5/9 Pages) ETC2

5 / 9 page

www.winsemi.com

Tel : +86-755-8250 6288

Fax : +86-755-8250 6299

5/9

WS9441 Product Description

WINSEMI MICROELECTRONICS

Function Description

The WS9441 is a high performance non-isolated buck

converter specially designed for LED lighting. The device

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.

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 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:













MAX

MIN

910

270

414

176

414

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

VCC Capacitor Selection

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.

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.

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

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

time.

The peak inductor current is calculated by the equation:

)

(

400

PK 

Where, RCS is the current sense resistor value.

The current in LED can be calculated by the equation:

)

(

LED 

Where, IPK is the peak current of the inductor.

Freewheeling Diode

The diode will b

ear 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.

Input Electrolytic Capacitor

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:

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.

WS9441 Datasheet(PDF) 5 Page - List of Unclassifed Manufacturers

WS9441 Datasheet(HTML) 5 Page - List of Unclassifed Manufacturers

Html Pages

1 2 3 4 5 6 7 8 9

Datasheet Download

Link URL