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WS3441A Schematic ( PDF Datasheet ) - WINSEMI

Teilenummer WS3441A
Beschreibung Non-isolated Buck Offline LED Driver
Hersteller WINSEMI
Logo WINSEMI Logo 




Gesamt 8 Seiten
WS3441A Datasheet, Funktion
WS3441A ProductDescription
Features
Critical Conduction Mode Operation
Internal 500V Power MOSFET
No Auxiliary Winding
Ultra Low Operating Current
±3% LED Output Current Accuracy
Efficiency up to 93%
LED Open Protection
LED Short Protection
Current Sensing Resistor Short Protection
Thermal Regulation Function
Available in SOP-8 Package
Applications
LED Candle Light
LED Bulb, Spot Light
T8/T10 LED String
Other LED Lighting
Typical Application
Non-isolated Buck Offline LED Driver
Description
The WS3441A is a high precision buck constant current
LED driver. The device operates in critical conduction mode
and is suitable for 85Vac~265Vac universal input offline LED
lighting.
The WS3441A integrates a 500V power MOSFET. The
operating current of the IC is very low. So it doesn’t need the
auxiliary winding for supplying the chip. It can achieve
excellent constant current performance with very few external
components, so the system cost and size are minimized.
The WS3441A utilizes patent pending current control
method. It can achieve precise output current and excellent
line regulation. The driver operates in critical conduction
mode, the output current does not change with the inductance
and LED output voltage.
The WS3441A offers rich protection functions to improve
the system reliability, including LED open circuit protection,
LED short circuit protection, VCC under voltage protection,
CS resistor short circuit protection and thermal regulation
function.
The WS3441A is available in SOP-8 Package.
AttentionA 22pF capacitor can be parallel with Rovp and a resistor can be parallel with the Vcc capacitor.
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WS3441A Datasheet, Funktion
WS3441A ProductDescription
And then the Rovp resistor value can be calculated by
the equation:
Rovp 3.3*Tovp *106 kohm
Protection Function
The WS3441A 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,
the system will trigger the over voltage protection and stop
switching.
When the LED short circuit is detected, the system
works at low frequency (5kHz), and the CS pin turn off
threshold is reduced to 200mV. So the system power
consumption is very low. At some catastrophic fault
condition, such as CS resistor shorted or inductor saturated,
the internal fast fault detection circuit will be triggered, the
system stops switching immediately.
After the system enters into fault condition, the VCC
voltage will decrease until it reaches the UVLO threshold,
then the system will re-start again. If the fault condition is
removed, the system will recover to normal operation.
Thermal Regulation
The WS3441A integrates thermal regulation function.
When the system is over 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 regulation
temperature is set to 150internally.
PCB Layouts
The following rules should be followed in WS3441A
PCB layout:
Vcc Capacitor
The bypass capacitor on VCC pin should be as close as
possible to the VCC Pin and GND pin.
ROVP Pin
The ROVP resistor should be as close as possible to
the ROVP 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 connecting to the negative
node of the bulk capacitor.
The Area of Power Loop
The area of main current loop should be as small as
possible to reduce EMI radiation, such as the inductor, the
power MOSFET, the output diode and the bus capacitor
loop.
NC pin
The NC pin should be connected to GND (pin1).
Drain Pin
To increase the copper area of DRAIN pin for better
thermal dissipation. However too large copper area may
compromise EMI performance.
The material of PCB
Avoid choosing the material that is easy to absorb the
moisture, just like paper copper-clad laminates.
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