20160401090344 6627

WS9441P Product Description
Non-isolated BuckOffline LED Driver
Features
 Critical Conduction Mode Operation

Internal 500V Power MOSFET

Gate Drive and No Auxiliary Winding

±3% LED Current Accuracy

Efficiency up to 93%

LED Short Circuit Protection

LED Open Circuit Protection



Current Sense Resistor Short Protection
Description
The WS9441P 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 WS9441P 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
Thermal Regulation Function
IC is 200uA, so it doesn’t need the auxiliary winding for supplying
External PWM Dimming
the chip, thus simplifying design and reducing cost.
The WS9441P adopts intelligent temperature control and
Applications
thoroughly solves

LED Bulb Lights
temperatures. It integrates an external dimming pin which inputs

LED Panel Lights
PWM signal and can dim by changing the duty cycle of the PWM

LED Strings
signal. The WS9441P offers full protection functions to improve
the problem of light flashing at high
the system reliability, including LED open circuit protection, LED
short circuit protection, CS resistor short circuit protection and
thermal regulation function.
The WS9441P is available in SOP-7 Package.
Typical Application Circuit
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WS9441P Product Description
Pin Configuration and Marking Information
The WS9441P is available in SOP-7 Package. The top marking is shown as below:
WS9441PS7P:Product Code
A:Product Code
X:Internal Code
BCY:Internal Code For QC
YMX:D/C
Pin Definition
Pin No.
Name
Description
1
GND
2
ROVP
3
DIM
Dinmming Pin.Must be floated when not in use.
4
VCC
Power Supply Pin
5,6
DRAIN
7
CS
Ground
Over Voltage Protection Setting Pin. Connect a resistor to GND
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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WS9441P Product Description
Ordering Information
Package
Marking
Part Number
7-Pin DIP-7, Pb-free
WS9441PS7P
WS9441PS7P
Recommended Operation Conditions
Part Number
Package
Input voltage
WS9441PS7P
SOP7
175VAC-264VAC
Maximum output power
150V/120mA
80V/200mA
Absolute Maximum Ratings
Symbol
Parameter
Range
Unit
VDS
Internal HV MOSFET drain voltage
-0.3~500
V
ICC_MAX
VCC pin maximum sink current
2.5
mA
VROVP
LED open circuit protection voltage regulation
-0.3~7
V
VCS
Current sense pin input voltage
-0.3~8
V
PDMAX
Power dissipation SOP7
-0.3~7
V
TJ
Maximum operating junction temperature
0.9
W
TSTG
Minimum/Maximum Storage temperature
150
℃
Note:Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device
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WS9441P Product Description
Electrical Characteristics (Unless otherwise specified, VCC=15V and TA =25 ℃)
Symbol
Parameter
Conditions
Min
Typ
Max
Units
17.8
18.8
19.8
V
14
15
16.2
V
9
9.5
10
V
Supply Voltage Section
VCC_CLAMP
VCC Clamp Voltage
UVLO_on
Chip Startup Voltage
10mA
VDD Under voltage
UVLO_off
protection
Ist
Startup Current
VCC= 13V
150
220
300
uA
Iop
Operating Current
Fop=70KHz
100
170
250
uA
390
400
410
mV
Current Sense Section
Threshold Voltage for
Vcs_th
Peak Current Limit
Leading Edge Blanking
TLEB
Time for Current Sense
TDELAY
Switch Off Delay Time
350
ns
200
ns
310
us
4.5
us
100
us
Internal Time Control Section
Toff_max
Minimum OFF Time
Toff_min
Maximum OFF Time
Ton_max
Maximum On Time
Rovp=70k
DIM Dimming Section
DIM Square Wave High
VH_DIM
Level
DIM Square Wave Low
VL_DIM
Level
DIM Square Signal
f_DIM
Frequency
1
3
5
V
-300
0
400
mV
0.1
0.5
5
KHZ
9
11
Ω
MOSFET Section
Static Drain-source
Rds_on
Vgs=15V,Ids=0.5A
On-State Resistance
Drain-Source Breakdown
BVdss
Voltage
Drain-Source Leakage
Idss
Vgs=0V,Ids=250uA
500
V
Vgs=0V,Vds=500V
Current
10
uA
Thermal Regulation Section
Thermal Regulation
TREG
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Temperature
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WS9441P Product Description
Function Description
adopted in WS9441P, the CS pin is connected to the current
The WS9441P is a high performance non-isolated buck
sense comparator, and the voltage on CS pin is compared
converter specially designed for LED lighting. The device
with the internal 400mV reference voltage. The MOSFET will
integrates a 500V power MOSFET. With the help of
advanced constant current control and gate drive technology,
be switched off when the voltage on CS pin reaches the
the
threshold. The CS comparator includes a 350ns leading edge
converter
achieves
excellent
constant
current
performance with very few external components. It does not
need auxiliary winding for powering the IC or voltage sensing,
blanking time.
The peak inductor current is calculated by the equation:
hence the system size and cost is greatly reduced.
I PK 
Start Up
After system powered on, the VCC pin capacitor is
400
(mA)
RCS
Where, RCS is the current sense resistor value.
charged up by the start up resistor. When the VCC pin
The current in LED can be calculated by the equation:
voltage reaches the turn on threshold, the internal circuits
start operating. The WS9441P integrates a 17V ZENER
I LED 
diode to clamp the VCC voltage. Due to the ultra-low
operating current, the auxiliary winding is not needed to
supply the IC.
I PK
(mA)
2
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
Freewheeling Diode
The diode will bear the reverse voltage equal to the
equation:
input voltage when the MOSFET is on. A 600V diode was
RST 
V IN _ MIN  1.414
I ST _ MAX

176  1.414
 910 K
270
Two resistors in 1206 size SMD can be used in series.
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.
VCC Capacitor Selection
The Vcc capacitor is used to bypass noise to IC, so that
Input Electrolytic Capacitor
Input voltage should be considered in to the capacitor
to assure its stable operation, and should be as close as
pressure, and the common value is 400V.
possible to the chip.
In general, the capacity design can be calculated by the
A 1uF or above capacitor can be used in Vcc. If
following empirical equations:
selecting MLCC, the material of X7R will be used to satisfy
the stability of the capacity under high temperatures. Due to
90Vac~264Vac: 1W output uses1uF buck electrolytic
capacitor;
external damage resulted from small volume and brittle
texture of MLCC, the Vcc is easy to leakage currents, which
176Vac~264Vac: 1W output uses 0.5uF buck electrolytic
capacitor.
will make the WS9441P unable to start. Strict control
measures are taken in its layout and productive process.
Output Capacitor
Electrolytic capacitor is recommended to be used. Its
Constant Current Control
stable capacitance can improve the efficiency of power supply,
The WS9441P utilizes proprietary current control
the LED ripple current and luminous efficiency.
method. It can achieve precise LED output current with a few
external components. Cycle by Cycle current sense is
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Vovp voltage should be considered in output capacitor
pressure.
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WS9441P Product Description
L
External PWM Dimming
VLED  (VIN  VLED )
f  I PK  VIN
The WS9441P 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
80V/220mA driver under 175~264Vac application is shown
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.
as below:
The minimum and maximum off time of WS9441P 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.
The duty cycle of the PWM signal
Thermal Regulation
The WS9441P integrates thermal regulation function.
Inductor Selection
The WS9441P 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
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
the MOSFET can be calculated by the equation:
regulation temperature is set to 150℃ internally.
L  I PK
t on 
VIN  VLED
Over Voltage Protection
Where,
The over voltage protection of the WS9441P can be
L is the inductance value,
programmed by the ROVP pin resistor. The ROVP pin voltage
IPK is the peak current of the inductor,
is 0.5V.
VIN is the DC bus voltage after the rectifier bridge,
VLED is the voltage on the LED.
When the LED is open circuit, the period of the output
voltage increases gradually, the demagnetization time gets
After the power MOSFET is also 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
shorter. The demagnetization time at OVP---- Tovp can be
calculated by the open circuit protection voltage by the
equation:
equation:
toff 
Tovp 
L  I PK
VLED
L  V CS
R CS  V OVP
Where,
The inductance can be calculated by the equation:
Vcs is the CS pin turn off threshold (0.4V);
Vovp is the open circuit protection voltage.
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WS9441P Product Description
And then the Rovp resistor value can be calculated by
the equation:
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 WS9441P PCB
layout:
VCC Capacitor: The VCC capacitor should be as close
Protection Function
The WS9441P offers rich 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,
as possible to the VCC Pin and GND pin.
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 system will trigger the over voltage protection and stop
The Area of Power Loop: The area of main current loop
switching. When the LED short circuit is detected, the system
should be as small as possible to reduce EMI radiation. And it
works at low frequency and the CS pin turnoff threshold is
should be away from diodes and other heating components.
reduced. So the system power consumption is very low. At
ROVP PIN: The ROVP resistor should be as close as
some abnormal fault condition, such as CS resistor shorted
possible to the ROVP Pin to increase its resistance to prevent
or inductor saturation, the internal fast fault detection circuit
from the interference.
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,
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.
then the system will restart again. If the fault condition is
removed, the system will recover to normal operation.
Line Voltage Compensation
The WS9441P 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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WS9441P Product Description
SOP7 Package Dimension
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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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WS9441P 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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