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PDF WS9221 Data sheet ( Hoja de datos )

Número de pieza WS9221
Descripción High Precision PSR Constant Current LED Driver
Fabricantes Winsemi 
Logotipo Winsemi Logotipo



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WS9221ProductDescription
High Precision PSR Constant Current LED Driver
Features
Built-in650V Power MOSFET
Constant current control without secondary sense and
feedback circuit.
No Auxiliary winding for sensing and supplying
Ultra low operating current to improve efficiency
Universal input voltage
±5% LED current accuracy
LED short and open circuit protection
CS resistor short circuit protection
VCC under-voltage protection
Over temperature protection
Available in SOP-7 package
Applications
GU10/E27 LED bulb, spot light
Other LED lighting
Description
The WS9221 is a high precision primary-side feedback
and regulation controller for LED lighting, it operates in
constant current control mode and is designed to work in
inductor current discontinuous conduction mode and
especially suitable for flyback convertor under universal input.
The output power of system is recommended to less than 5W.
The WS9221integrates 650V power MOSFET. Since
adopting primary sense and feedback control technology, the
secondary sense and feedback circuit is eliminated. The loop
compensation components are also removed while
maintaining stability overall operating conditions. The
operating current is very low, and it doesn’t need the auxiliary
winding for sensing the output current and supplying the chip.
The low component counts and small system size
arerealized.
Since using the proprietary high accurate current sense
method, theWS9221 realizes ±5% accuracy of LED current
along with excellent line and load regulation.
The WS9221 offers rich protection functions including
LED open/short circuit protection, CS resistor short circuit
protection, over-temperature protection, VCC under voltage
protection.
Typical Application
WINSEMI MICROELECTRONICS
WINSEMI MICROELECTRONICS
WINSEMI MICROELECTRONICS
Copyright@WinsemiMicroelectronics Co.,Ltd.,All rightreserved
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WS9221 pdf
WS9221ProductDescription
Application Information
The WS9221 is a high performance power switch
specially designed for LED lighting, with patent constant
current control technology. The WS9221integrates a 650V
power MOSFET. The accurate LED current can be realized
without opto-coupler, TL431 feedback circuit and auxiliary
winding while minimizing the external component count,
lowering the total bill of material cost.
Start Up
The start-up current in WS9221 is designed to as low as
45uA. The VCC capacitor will be charged through the
start-up resistor when the system is powered on. Once the
VCC voltage reaches the start-up threshold, the WS9221
will start to switch. The WS9221 integrates a 8V zener for
VCC clamping. Due to the ultra-low operating current, the
auxiliary winding is not needed to supply the IC.
Operating Switching Frequency
The WS9221 is designed to work in discontinuous
conduction mode and no external loop compensation
component is required while maintaining stability. The
maximum duty cycle is limited to 42%. The maximum
switching frequency at normal operation is suggested to set
around 65KHz~70KHz. If the maximum frequency is set too
high, it will affect the number of maximum series LED lamps.
If set too low, the LED open circuit voltage will be too high.
The maximum and minimum switching frequency is
limited in WS9221 to ensure the stability of system.
The switching frequency can be set by the formula:
f
8
Np2 VLED
Ns2 Lp ILED
Where, LP is the primary winding inductance of
transformer.
Constant Current Control
Protection Function
Cycle-by-Cycle current sense is adopted in WS9221,
The WS9221 has integrated rich protection functions,
the CS is connected to the current sense comparator, and
LED open/short protection, CS resistor short circuit
the voltage on CS will be compared with the internal 500mV
protection, VCC under voltage protection, over temperature
reference voltage, the MOSFET will be switched off when
protection, and so on. When the LED is open circuit, it will
the voltage on CS reaches the threshold. The output of the
trigger over-voltage protection logic and latch, the system
comparator includes a 500ns leading edge blanking time.
stops switching immediately.
The primary peak current is given by:
When the LED short circuit is detected, the system
I P_PK
500 (mA)
RCS
works at low frequency (Fop=3KHz), so the power
consumption is low. At some catastrophic fault condition,
such as shorted CS resistor or flyback transformer
The current in LED can be calculatedby the equation:
saturation, the internal fast fault detection circuit will trigger
I OUT
I P_PK
4
NP
NS
and latch, the system stops switching immediately.
After the system enters into fault latch condition, the
VCC voltage will fall until it reaches UVLO threshold. Then
Where,
the system will re-start again. If the fault condition is
NP: primary winding turns of transformer
removed, the system will recover to normal operation.
NS: secondary winding turns of transformer
IP_PK: peak current in MOSFET
PCB Layouts
The following rules should be followed in WS9221 PCB
Power MOSFET
The WS9221 integrates a 650V power N-MOSFET. It
can minimize the external component count and reduce the
BOM cost and PCB size.
The WS9221 uses SOP-7 package. The recommended
system output power is below 5W in universal input
(90Vac~265Vac) application.
layout:
Bypass Capacitor
The bypass capacitor on VCC should be as close as
possible to the VCC pin and GND pin.
Ground Path
The power ground path for current sense should be
short, and the power ground path should be separated from
small signal ground path before the negative of the bulk
WINSEMI MICROELECTRONICS
WINSEMI MICROELECTRONICS
WINSEMI MICROELECTRONICS
www.winsemi.com Tel : +86-755-8250 6288 Fax : +86-755-8250 6299
WINSEMI MICROELECTRONICS
WINSEMI MICROELECTRONICS
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