WS3440 Datasheet PDF - WINSEMI
| Part Number | WS3440 | |
| Description | Constant Current Controller | |
| Manufacturers | WINSEMI | |
| Logo |  |
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WS3440 Product Description
Constant Current Controller For Non-isolated Buck LED Driver
Features
� Inductor Current Critical Mode, No Need to
Compensate the Inductance Variation
� Source Driver Structure, Not Need the Auxiliary
Winding for VCC
� ±3% LED Current Accuracy
� Up to 93% System Efficiency
� LED Short Circuit Protection
� Current Sense Resistor Short Circuit Protection
� Over Temperature Protection
� Programmable LED open protection
Applications
� LED Bulb
� LED Candle light
� LED Spot light
� Decorative LED lighting
General Description
The WS3440 is a high precision constant current controller，
designed for non-isolated buck LED driver. suitable for AC
input voltage range (84V-264V)
The WS3440 uses high precision current sense circuit and
patent method for constant current control, to achieve high
precision output current and excellent line regulation. The
WS3440 operates in inductor current critical mode. The LED
current is constant over wide range of inductance variation
and the LED output voltage, so the load regulation is
excellent.
The WS3440 uses patent source driver architecture. The
operation current is 200uA only, so the auxiliary winding is not
needed. It can simplify the system design and reduce the
system cost.
The WS3440 offers rich protection functions, including LED
open/short circuit protection, current sense resistor short
circuit protection and over temperature protection.
Typical Application Circuit
AC
1 ROVP G ND 2
6 V C C G ATE 5
3 CS
S4
WIN SEM I M ICROELECTRON ICS
WIN SEM I M ICROELECTRON ICS
WIN SEM I M ICROELECTRON ICS
Copyright@Winsemi Microelectronics Co., Ltd., All right reserved.
WIN SEM I M ICROELECTRON ICS
W/T-Y027-Rev.A/1 May.2014
WIN SEM I M ICROELECTRON ICS
0813
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WS3440 Product Description
Function Description
WS3440 is a constant current controller, designed for driving
non-isolated buck LED power supply. WS3440 uses patent
constant current control method and source driver structure,
excellent constant current characteristic is achieved with low
counts components. Low cost and high efficiency of system
is realized.
cost is low.
Inductance Calculation
The WS3440 is designed to work in inductor current critical
mode; the energy will be stored in the inductor when the
MOSFET is turned on. The turn on time is given by:
Start up
The Vcc will be charged through the startup resistor when
the system is powered on. When the voltage on Vcc reaches
the startup voltage threshold, the controller starts to
switching. The Vcc voltage of WS3440 is clamped to 7.3V
by internal Zener diode.
ton
=
L × I PK
VIN − VLED
The L is the inductance. The Ipk is the peak current in
inductor. The VIN is the input rectified voltage. The VLED
is the voltage on LED.
When the power MOSFET is turned off, the inductor current
will decrease from the peak current to zero. The turn off time
Constant Current Control and Output Current Setting
The WS3440 uses patent constant current control method,
is given by:
toff
=
L × I PK
VLED
excellent constant current is achieved with low counts
components. The WS3440 senses the peak current in
inductor cycle by cycle. The CS Pin is connected to the input
of internal current comparator, and compared with the
internal 400mV reference voltage. The external power
MOSFET will be turned off when the CS pin voltage reaches
the voltage threshold. The comparator has a 350ns LEB
timer to avoid mis-trigger.
The peak current in the inductor is given by:
I PK
=
400 (mA)
RCS
The Rcs is the resistance of current sense resistor The
current in LED can be calculated by the following equation:
I LED
=
I PK
2
The IPK is the peak current in inductor
The MOSFET will be turned on again when it detects the
inductor current goes to zero. The inductance can be
calculated by the following equation:
L = VLED × (VIN − VLED )
f × I PK ×VIN
The f is the system switching frequency, which is
proportional to the input voltage. So the minimum switching
frequency is set at lowest input voltage, and maximum
switching frequency is set at highest input voltage.
The WS3440 internally set the minimum off time to 4us and
maximum off time to 240 us. When the inductance is very
small, the toff may goes below the minimum off time and the
inductor current becomes discontinuous. So the output LED
current will be smaller than the setting value. If the
inductance is too large, the toff may goes beyond the
maximum off time and the inductor current becomes
Source Driver Structure
continuous. And the output LED current will be larger than
the setting value. So it’s very important to select a right
The WS3440 uses the patent source driver structure. The
inductance.
typical operation current is as low as 200uA, the auxiliary
The WS3440 also internally set the maximum on time to
winding is not need. So the system design is simple and the
40us. When the input voltage is very low or LED output
WIN SEM I M ICROELECTRON ICS
WIN SEM I M ICROELECTRON ICS
WIN SEM I M ICROELECTRON ICS
Copyright@Winsemi Microelectronics Co., Ltd., All right reserved.
WIN SEM I M ICROELECTRON ICS
W/T-Y027-Rev.A/1 May.2014
WIN SEM I M ICROELECTRON ICS
0813
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Part DetailsOn this page, you can learn information such as the schematic, equivalent, pinout, replacement, circuit, and manual for WS3440 electronic component. |
| Information | Total 8 Pages | |
| Link URL | [ Copy URL to Clipboard ] | |
| Download | [ WS3440.PDF Datasheet ] | |
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