WS3413 datasheet(5/8 Pages) WINSEMI

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WS3413 Product Description

Function

Function Description

Description

The WS3413 is designed for active PFC non-isolated buck

LED driver, which integrates 500V power MOSFET and

using DIP8 package, producing up to 260mA output current.

It operates under

valley switching mode, automatically

adapting to the variation of the inductance and the output

voltage.

can

achieve

excellent

constant

current

performance with very few external components.

Start

Start up

The start current is very low, Typ. 70uA(Max. 100uA). Under

the design system of 85VAC, the startup resistor is:

100

Chip

hip

hip Supply

Supply

After startup, the output voltage should supply the chip,

rectifier diodes D6 need to use fast recovery diodes.Current

limiting resistor R4 is calculated as:

(

)

LED

400

−

Where, D is duty cycle, 400uA is the normal operation

current of the chip, Vled is output load voltage. The

consumption of R4 is:

(

)

(

LED

−

For example:

Requirements:180~260V input voltage, 36~80V output,

240mA output current.

The R4 design of above program should be met:

1. Supply Problem when Min. input AC voltage 180V and

Min. output voltage 36V(which is the weakest power supply):

D=36/180/1.414=0.141,R4=(1-0.141)*(36-9)/400uA=58k

2.Power consumption problem of R4 when Max. input AC

voltage 260V and Max. output voltage 80V(which is the

strongest power supply):

D=80/260/1.414=0.218

The power consumption of R4:

P=(80-9)*(80-9)/58*(1-0.218)=68mW

Sence

Sence Resistor

Resistor

The WS3413 is designed for active PFC non-isolated buck

LED driver. It operates under

valley switching mode and

can achieve high accuracy constant current performance

with very few external components. The peak current of

inductor is continuous detected. CS terminal is connected

internal of the chip, and compared with the internal 200mV.

Internal Amplifier’s output COMP adjust the on-time, making

the average value os CS equal to 200mV after the system is

stable. In addition, a 1V cycle-by-cycle over current

protection is set up inside CS pin.

LED output current:

LED

FB Voltage

Voltage

Voltage Detection

Detection

FB voltage determines the working status of the system,

when

greater

then

1.6V(typ.),

WS3413

will

automatically considered as output over voltage protection.

The system will enter extremely energy efficient hiccup

mode. Output over voltage protection voltage as follows:

OVP

R2,R3,please refer to the typical application diagram, in

which R3=1k(no more than 2k). use 1.3 instead of constant

1.6 in the above formula in the design of system. Assuming

Vovp=90V, we got R2=56k from the above formula,

choosing 60k for R2 (larger as far as possible).

Because VFB2 is between 1.3 and 1.9, choose 1.9 to

calculate the withstand voltage of C4,

Vovp=1.9*(1+60)/1=116V

The withstand voltage of C4 shoule larger than the above

value, 200V capacitor could be used.

The WS3413 uses the patent source driver structure. The

typical operation current is as low as 200uA, the auxiliary

winding is not need. So the system design is simple and the

cost is low.

WS3413 will automatic detect the output voltage when

enters hiccup mode; and will re-enter the normal working

state when the output voltage is lower than Vovp.

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