WS3410 View Datasheet(PDF) - Shenzhen Winsemi Microelectronics Co., Ltd
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WS3410 Datasheet PDF : 8 Pages
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WS3410 Product Description
Function Description
The WS3410 is designed for active PFC non-isolated buck
LED driver, using SOT23-6 package, It operates under
valley switching mode, automatically adapting to the
variation of the inductance and the output voltage. It can
achieve excellent constant current performance with very
few external components.
Start up
The start current is very low, Typ. 70uA(Max. 100uA). Under
the design system of 85VAC, the startup resistor is:
R = 85 * 2 = 1.2M
100
Sence Resistor
The WS3410 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 so 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:
0.2V
I LED = RCS
Chip 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:
R4
=
(1 −
)D * VLED − 9
400uA
Where, D is duty cycle, 400uA is the normal operation
current of the chip, Vled is output load voltage. The
FB Voltage Detection
FB voltage determines the working status of the system,
when FB is greater then 1.6V(typ.), WS3410 will
automatically considered as output over voltage protection.
The system will enter extremely energy efficient hiccup
mode. Output over voltage protection voltage as follows:
VOVP
= 1.6 * R2 + R3
R3
consumption of R4 is:
PR 4
=
(VLED − 9)2
R4
* (1 −
D)
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
R2,R3,please refer to the typical application diagram, in
which R3=10k(Not over 15 K, not less than 8.2 K). use 1.3
instead of constant 1.6 in the above formula in the design of
system. Assuming Vovp=90V, we got R2=552k from the
above formula, choosing 560k 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*(10+560)/10=108V,The withstand voltage of C4
shoule larger than the above value, 200V capacitor could be
used. WS3410 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.
voltage 260V and Max. output voltage 80V(which is the
Output Open(Short) protection
strongest power supply):
Output open/short protection is integrated inside WS3410.
D=80/260/1.414=0.218
Once output open/short circuit is detected, the system will
The power consumption of R4:
automatic enter hiccup mode until the protection signal
P=(80-9)*(80-9)/58*(1-0.218)=68mW
disappear.
WIN SEM I M ICROELECTRON ICS
WIN SEM I M ICROELECTRON ICS
WIN SEM I M ICROELECTRON ICS
www.winsemi.com Tel : +86-755-8250 6288 Fax : +86-755-8250 6299
WIN SEM I M ICROELECTRON ICS
WIN SEM I M ICROELECTRON ICS
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