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WS3412 Product Description
WS3412 Active PFC Non-isolated Buck LED Driver
Features
General Description
�
High Power Factor Correction, Low Total Harmonic
The WS3412 is designed for active PFC non-isolated buck
Distortion
LED driver. It operates at valley switching mode with high
�
Dynamic Temperature Compensation
efficiency, low EMI and High PF. The output current
�
550V Power MOSFET Integrated
automatically adapt to the variation of the inductance and the
�
No Auxiliary Winding For Supplying
output voltage. The truly constant current LED is realized.
�
SOP8 Package, Up To 260mA Output Current
The WS3412 integrates 550V power MOSFET, using SOP 8
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Valley Switching, High efficiency, Low EMI
package,
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Automatic Compensate the Inductance Variation
It can achieve excellent constant current performance with
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Automatic Adapt to the Change of Output Voltage
very few external components.
�
LED Short Circuit Protection
The WS3412 offers rich protection functions, including over
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Over Voltage Protection
voltage protection, LED short circuit protection, cycle by cycle
�
Over Temperature Protection
current limiting, dynamic temperature compensation, over
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Open Circuit Protection
temperature protection and soft start.
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Few External Components
WS3412 consumes very low start current and operation
current,
producing
driving
LED
up
to
260mA
efficiently
under
output
current.
universal
AC
input(85VAC~265VAC).
WS3412 is available in SOP8 package.
Applications
�
LED Driver Supply
Typical Application Circuit
5
6
3
AC
2
8
D
CS
D
CS 7
VCC
FB
GND
C O MP
4
LE D+
1
LE D-
W/T-S031-Rev.A/ 0 Nov.2013
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WS3412 Product Description
Pin Definition and Device Marking
WS3412 is available in SOP-8 package.
COMP
VC C
3
FB
4
W S3 41 2S 8 P
2
A XB YM
GND
CS
8
1
WS3412S8P: Product code
7
CS
6
D
5
D
A: Product Code
X：Internal Code
B：Area Code
YM：Year, Month
Pin Function Description
Pin Name
Pin NO.
Description
COMP
1
Loop compensation, with a cap to GND.
GND
2
Ground
VCC
3
Power supply
FB
4
Feedback signal input.
D
5
Internal HV power MOSFET drain
D
6
Internal HV power MOSFET drain
CS
7
Current sense input, connect to internal HV power MOSFET source
CS
8
Current sense input, connect to internal HV power MOSFET source
Block Diagram
VCC
FB
3
4
GND
2
8 .5 V
OVP
U V LO
Inter
s upply
Zero-Current
Detect
Tem perature
control
5 ,6
D
Logic
&
driver
P FC
control
7 ,8 C S
OTP
200m V
CO MP 1
1V
EA
Current
s ens e
1 .5 V
low-clam p
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WS3412 Product Description
Ordering Information
Package
Part Number
Marking
8-Pin SOP-8, Pb-free
WS3412S8P
WS3412S8P
Recommended Operating Condition
symbol
parameter
value
units
ILED
Output LED current
< 260
mA
Absolute Maximum Ratings
symbol
parameter
Range
Units
VDS
Internal HV MOSFET drain voltage
-0.3~550
V
VCC
VCS
Power Supply
-0.3~8.5
V
Current sense pin input voltage
-0.3~7
V
VFB
VCOMP
Feedback voltage input
-0.3~7
V
Loop Compensation Pin voltage
-0.3~7
V
PDMAX
TJ
Power dissipation
0.5
W
Max. Operating junction temperature
150
℃
T STG
Max./Min. Storage temperature range
-55~150
℃
Note: Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device.
Under “recommended operating conditions” the device operation is assured, but some particular parameter may not be
achieved.
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WS3412 Product Description
Electrical Characteristics (Unless otherwise specified，TA=25℃，VCC=8V)
Symbol
Parameter
Conditions
Min
Typ
Max
Units
7.8
8.5
9.3
V
5
mA
Supply Voltage Section
Vcc_clamp
VCC Clamping Voltage
Icc_clamp
VCC Clamping Current
VCC_ST
VCC Start Up Voltage
Vuvlo_HYS
VCC Under Voltage
Latch Out Hysteresis
Ist
Start Up Current
Iop
Operation Current
VCC Rise
7.5
V
VCC Falling
1.5
V
VCC<VCC_ST-0.5V
70
100
uA
400
uA
1
V
Current Sensor Section
Current Sensor Voltage
Vocp
Threshold
TLEB
Leading Edge Blanking
350
ns
TDELAY
Turn Off Delay Time
200
ns
Loop Compensation Section
VREF
Internal Reference Voltage
VCL
Comp Low Clamp Voltage
194
VCH
200
206
mV
1.5
V
4
V
3
us
20
us
Internal Driver Secion
Toff_min
Min. Demagnetization Time
Ton_max
Max. On Time
Feedback input Section
VFB
OVP Threshold Voltage
1.6
V
VZCD
Zero Crossing Checking Threshold
0.2
V
Internal HV MOSFET
RDSON
HV MOS ON Resistance
VDS
Drain to Source voltage
6.5
ohm
550
V
Over Temperature Section
TSD
Thermal Shut Down Temperature
160
℃
TSD_HYS
Thermal Shut Down Hysteresis
30
℃
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WS3412 Product Description
Function Description
strongest power supply):
The WS3412 is designed for active PFC non-isolated buck
D=80/260/1.414=0.218
LED driver, which integrates 550V power MOSFET and
The power consumption of R4:
using SOP 8 package, producing up to 260mA output
P=(80-9)*(80-9)/58*(1-0.218)=68mW
current. It operates under
valley switching mode,
Sence Resistor
automatically adapting to the variation of the inductance and
the output voltage.
The WS3412 is designed for active PFC non-isolated buck
It can achieve excellent constant current performance with
LED driver. It operates under
very few external components.
valley switching mode and
can achieve high accuracy constant current performance
with very few external components. The peak current of
Start up
inductor is continuous detected. CS terminal is connected
internal of the chip, and compared with the internal 200mV.
The start current is very low, Typ. 70uA(Max. 100uA). Under
Internal Amplifier’s output COMP adjust the on-time, making
the design system of 85VAC, the startup resistor is:
the average value os CS equal to 200mV after the system is
stable. In addition, a 1V cycle-by-cycle over current
85 * 2
R=
= 1.2M
100
protection is set up inside CS pin.
LED output current:
I LED =
C hip Supply
0.2V
R CS
After startup, the output voltage should supply the chip,
FB Voltage Detection
rectifier diodes D6 need to use fast recovery diodes.Current
limiting resistor R4 is calculated as:
FB voltage determines the working status of the system,
V −9
R 4 = (1 − D ) * LED
400uA
when
FB
is
greater
then
1.6V(typ.),
WS3412
will
automatically considered as output over voltage protection.
Where, D is duty cycle, 400uA is the normal operation
The system will enter extremely energy efficient hiccup
current of the chip, Vled is output load voltage. The
mode. Output over voltage protection voltage as follows:
consumption of R4 is:
PR 4 =
VOVP = 1.6 *
(V LED − 9 )2 * (1 − D)
R4
R2 + R3
R3
R2,R3,please refer to the typical application diagram, in
For example:
which R3=1k(no more than 2k). use 1.3 instead of constant
Requirements:180~260V input voltage, 36~80V output,
1.6 in the above formula in the design of system. Assuming
240mA output current.
Vovp=90V, we got R2=56k from the above formula,
The R4 design of above program should be met:
choosing 60k for R2 (larger as far as possible).
1. Supply Problem when Min. input AC voltage 180V and
Because VFB2 is between 1.3 and 1.9, choose 1.9 to
Min. output voltage 36V(which is the weakest power supply):
calculate the withstand voltage of C4,
Vovp=1.9*(1+60)/1=116V
D=36/180/1.414=0.141,R4=(1-0.141)*(36-9)/400uA=58k
The withstand voltage of C4 shoule larger than the above
2.Power consumption problem of R4 when Max. input AC
value, 200V capacitor could be used.
voltage 260V and Max. output voltage 80V(which is the
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WS3412 Product Description
The WS3412 uses the patent source driver structure. The
Input Filter Capacitor
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.
In order to obtain high PF value, the input capacitor can not
be too large. 10-100nF is recommended.
WS3412 will automatic detect the output voltage when
Power Factor Correction
enters hiccup mode; and will re-enter the normal working
state when the output voltage is lower than Vovp.
Active PFC control circuit is integrated in WS3412, which
can get high PF value and low THD.
Output Open(Short) protection
PCB Design
Output open/short protection is integrated inside WS3412.
Once output open/short circuit is detected, the system will
automatic enter hiccup mode until the protection signal
disappear.
The following guidelines should be followed in WS3412 PCB
layout:
Bypass Capacitor: The bypass capacitor on VCC pin should
be as close as possible to the VCC and GND pins.
Over Temperature Automatic adjustment of output
Ground Path: The power ground path for current sense
current
should be short, and the power ground path should be
separated from small signal ground path before the negative
WS3412 has over temperature regulating function, gradually
reducing the output current when the power is over
node of the bulk capacitor.
The Area of Power Loop: The area of power loop should be
temperature, so as to control the output power and the
as small as possible to reduce EMI radiation.
temperature rise, keeping the power temperature in a setting
value in order to improving the reliability of the system. The
And the controller should be placed away from the heat
generator, such as the power diode.
starting regulation temperature is 135℃.
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WS3412 Product Description
Package Information
SOP-8 Package Outline Dimensions
B2
0 . 5 * 0.125±0. 05
球形标记
A1
A2
D
D1
B
B1
A
C4
A3
R2
C
C1
θ4
C2
θ2
R1
θ1
C3
θ3
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Dimensions in Millimeters
Symbol
Dimensions in Inches
Min
Max
Min
Max
A
4.70
5.10
0.185
0.201
B
3.70
4.10
0.146
0.161
C
1.30
1.50
0.051
0.059
A1
0.35
0.48
0.014
0.019
A2
1.27TYP
0.05TYP
A3
0.345TYP
0.014TYP
B1
5.80
B2
6.20
0.228
5.00TYP
0.244
0.197TYP
C1
0.55
0.70
0.022
0.028
C2
0.55
0.70
0.022
0.028
C3
0.05
0.225
0.002
0.009
C4
0.203TYP
0.008TYP
D
1.05TYP
0.041TYP
D1
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WS3412 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 : 86-0755-82506257
FAX : 86-0755-82506299
Web Site : www.winsemi.com
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