20160401090321 5989

WS9441 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 WS9441 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 WS9441 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
Thermal Regulation Function
inductance and LED output voltage. The operating current of the
IC is 200uA, so it doesn’t need the auxiliary winding for supplying
the chip, thus simplifying design and reducing cost.
Applications

LED Bulb Lights

LED Panel Lights
thoroughly solves the problem of light flashing at high

LED Strings
temperatures. The WS9441 offers full protection functions to
The WS9441 adopts intelligent temperature control and
improve the system reliability, including LED open circuit
protection, LED short circuit protection, CS resistor short circuit
protection and thermal regulation function.
The WS9441 is available in SOP-7 Package.
Typical Application Circuit
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WS9441 Product Description
Pin Configuration and Marking Information
The WS9441 is available in SOP-7 Package. The top marking is shown as below:
Pin Definition
Pin No.
Name
1
GND
2
ROVP
3
NC
4
VCC
5,6
DRAIN
7
CS
Description
Ground
Over Voltage Protection Setting Pin. Connect a resistor to GND
No Connection.Should be hanged out.
Power Supply Pin
Internal HV Power MOSFET Drain
Current Sense Pin. Connect a sense resistor between this pin and GND
pin.
Block Diagram
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WS9441 Product Description
Ordering Information
Package
Marking
Part Number
7-Pin DIP-7, Pb-free
WS9441S7P
WS9441S7P
Recommended Operation Conditions
Part Number
Package
Input voltage
WS9441S7P
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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WS9441 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
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
9
Ω
500
V
Vgs=0V,Vds=500V
Current
11
10
uA
Thermal Regulation Section
Thermal Regulation
TREG
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Temperature
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WS9441 Product Description
Function Description
comparator, and the voltage on CS pin is compared with the
The WS9441 is a high performance non-isolated buck
internal 400mV reference voltage. The MOSFET will be
converter specially designed for LED lighting. The device
switched off when the voltage on CS pin reaches the threshold.
integrates a 500V power MOSFET. With the help of
advanced constant current control and gate drive technology,
The CS comparator includes a 350ns leading edge blanking
the
time.
converter
achieves
excellent
constant
current
performance with very few external components. It does not
The peak inductor current is calculated by the equation:
need auxiliary winding for powering the IC or voltage sensing,
I PK 
hence the system size and cost is greatly reduced.
Start Up
400
(mA)
RCS
Where, RCS is the current sense resistor value.
After system powered on, the VCC pin capacitor is
The current in LED can be calculated by the equation:
charged up by the start up resistor. When the VCC pin
voltage reaches the turn on threshold, the internal circuits
I LED 
start operating. The WS9441 integrates a 17V ZENER diode
I PK
(mA)
2
to clamp the VCC voltage. Due to the ultra-low operating
Where, IPK is the peak current of the inductor.
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—
Freewheeling Diode
264VAC, the start-up resistor can be calculated by the
equation:
RST 
The diode will bear the reverse voltage equal to the
input voltage when the MOSFET is on. A 600V diode was
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.
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.
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
A 1uF or above capacitor can be used in Vcc. If
following empirical equations:
90Vac~264Vac: 1W output uses1uF buck electrolytic
selecting MLCC, the material of X7R will be used to satisfy
the stability of the capacity under high temperatures. Due to
capacitor;
176Vac~264Vac: 1W output uses 0.5uF buck electrolytic
external damage resulted from small volume and brittle
texture of MLCC, the Vcc is easy to leakage currents, which
capacitor.
will make the WS9441 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 WS9441 utilizes proprietary current control method.
the LED ripple current and luminous efficiency.
Vovp voltage should be considered in output capacitor
It can achieve precise LED output current with a few external
components. Cycle by Cycle current sense is adopted in
pressure.
WS9441, the CS pin is connected to the current sense
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WS9441 Product Description
Inductor Selection
current is gradually reduced; the output power and thermal
The WS9441 works in a inductor critical current
dissipation are also reduced. The system temperature is
conduction mode. When the power MOFET is switched on,
regulated and the system reliability is improved. The thermal
the current in the inductor rises up from zero. The on time of
regulation temperature is set to 150℃ internally.
the MOSFET can be calculated by the equation:
t on 
Over Voltage Protection
L  I PK
VIN  VLED
The over voltage protection of the WS9441 can be
programmed by the ROVP pin resistor. The ROVP pin voltage
Where,
is 0.5V.
L is the inductance value,
When the LED is open circuit, the period of the output
IPK is the peak current of the inductor,
VIN is the DC bus voltage after the rectifier bridge,
voltage increases gradually, the demagnetization time gets
shorter. The demagnetization time at OVP---- Tovp can be
VLED is the voltage on the LED.
After the power MOSFET is also switched off and the
current in the inductor decreases. When the inductor current
calculated by the open circuit protection voltage by the
equation:
reaches zero, the power MOSFET is turned on again by IC
Tovp 
internal logic. The off time of the MOSFET is given by the
equation:
toff 
L  I PK
VLED
Where,
Vcs is the CS pin turn off threshold (0.4V);
The inductance can be calculated by the equation:
L
L  V CS
R CS  V OVP
VLED  (VIN  VLED )
f  I PK  VIN
Vovp is the open circuit protection voltage.
And then the Rovp resistor value can be calculated by the
equation:
Rovp  120  7 . 67 * Tovp * 10 6 (KΩ)
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
It is suggested that the open circuit protection voltage is
set at or above 1.5 times maximum load voltage.
maximum switching frequency is set at highest input voltage.
The minimum and maximum off time of WS9441 is set at
Protection Function
4.5us and 310us, respectively. Referring to the equation of
The WS9441 offers rich protection functions to improve
Toff calculation, if the inductance is too small, the Toff may be
the system reliability, including LED open/short protection, CS
smaller than the minimum off time, the system will operate in
resistor short protection, VCC under voltage protection,
discontinuous conduction mode and the output current will
thermal regulation. When the LED is open circuit, the system
be smaller than the designed value. If the inductance is too
will trigger the over voltage protection and stop switching.
large, the Toff may be larger than the maximum off time, the
When the LED short circuit is detected, the system works at
system will operate in continuous conduction mode and the
low frequency and the CS pin turnoff threshold is reduced. So
output current will be higher than the designed value. So it is
the system power consumption is very low. At some abnormal
important to choose a proper inductance.
fault condition, such as CS resistor shorted or inductor
saturation, the internal fast fault detection circuit will be
Thermal Regulation
triggered, the system stops switching immediately.
The WS9441 integrates thermal regulation function.
After the system enters into faulty condition, the VCC
When the system is under higher temperature, the output
voltage will decrease until it reaches the UVLO threshold, then
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WS9441 Product Description
the system will restart again. If the fault condition is removed,
Ground Path: The power ground path for current sense
the system will recover to normal operation.
resistor should be short, and the power ground path should be
separated from small signal ground path before connecting to
Line Voltage Compensation
The WS9441 integrates line voltage compensation
the negative node of the bulk capacitor.
The Area of Power Loop: The area of main current loop
function, which makes LED current remain unchanged in the
should be as small as possible to reduce EMI radiation. And it
range of full voltage with good line regulation and current
should be away from diodes and other heating components.
accuracy.
ROVP PIN: The ROVP resistor should be as close as
possible to the ROVP Pin to increase its resistance to prevent
PCB Layout
from the interference.
The following rules should be followed in WS9441 PCB
DRAIN PIN: The copper area of DRAIN pin can be
increased for better thermal dissipation. And it should be away
layout:
VCC Capacitor: The VCC capacitor should be as close
from CS/VCC and ROVP Pin.
as possible to the VCC Pin and GND pin.
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WS9441 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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WS9441 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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