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PDF ( 数据手册 , 数据表 ) BW9910A

零件编号 BW9910A
描述 High Brightness LED Driver
制造商 Bruckewell Technology
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BW9910A 数据手册, 描述, 功能
BW9910/A High Brightness LED Driver
Features
Efficiency > 90%
Universal rectified 85VAC to 265VAC input range
Constant current LED driver
Applications from a few mA to more than 1.0A
LED string from one to hundreds of diodes
PWM low-frequency dimming via PWM_D pin
Input voltage surge ratings up to 500V
Internal over temperature protection (OTP)
7.5V MOSFET drive – BW9910
10V MOSFET drive – BW9910A
Typical Applications
AC/DC or DC/DC LED Driver applications
RGB backlighting LED Driver
Backlighting of flat panel displays
General purpose constant current source
Signage and decorative LED lighting
Buck/Buck-Boost/Boost LED driver
T8/T9/T10 LED tubes
E26/E27 LED bulbs
Product Description
The BW9910/BW9910A is a PWM high-efficiency LED
driver control IC. It allows efficient operation of high
brightness (HB) LEDs from voltage sources ranging from
85VAC up to 265VAC. The BW9910/BW9910A controls an
external MOSFET at fixed switching frequency up to
300kHz. The frequency can be programmed using a single
resistor. The LED string is driven at constant current rather
than constant voltage, thus providing constant light output
and enhanced reliability. The output current can be
programmed between a few mA and up to more than 1.0A.
The BW9910/BW9910A uses a rugged high voltage
junction isolated process that can withstand an input
voltage surge of up to 500V. Output current to an LED
string can be programmed to any value between zero and
its maximum value by applying an external control voltage
at the linear dimming control input of the
BW9910/BW9910A. The BW9910/BW9910A provides a
low-frequency PWM dimming input that can accept an
external control signal with a duty ratio of 0%~100% and a
frequency of up to a few kHz.
The BW9910A allows wider range of external MOSFET
which has lower RDS(ON) (drain-source on resistance) at
higher VGS. The BW9910/BW9910A is available in SOP-8
and SO8-EP packages.
Typical Application Circuit
© 2012 Bruckewell Technology Corp., Ltd.
1
www.bruckewell-semi.com/
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BW9910A pdf, 数据表
BW9910/A High Brightness LED Driver
Assuming the nominal rectified input voltage VIN
120V 1.414 169V, the switching duty ratio can be
determined as follows :
0.195
(6)
Then, in this example, given the switching frequency,
fOSC 50kHz, the required on-time of the MOSFET
transistor can be calculated as below :
3.91µs
(7)
The required minimum value of the inductor is given by :
5.06mH
(8)
Input Bulk Capacitor
An input filter capacitor should be designed to hold the
rectified AC voltage above twice the LED string voltage
throughout the AC line cycle. Assuming 15% relative
voltage ripple across the capacitor, a simplified formula
for the minimum value of the bulk input capacitor is given
by :
Equation :
(9)
where
DCH : CIN capacity charge work period, generally about
0.20 ~ 0.25,
fL : input frequency for full range (85VRMS ~ 265VRMS),
VDC(MAX) should be set 10% ~ 15% of
If the capacitor has a 15% voltage ripple then a simplified
formula for the minimum value of the bulk input capacitor
approximates to :
© 2012 Bruckewell Technology Corp., Ltd.
(10)
8
24µF, a value 33µF/250V can be used.
A passive PFC circuit at the input requires using two
series connected capacitors at the place of calculated
CMIN. Each of these identical capacitors should be rated
for ½ of the input voltage and have twice as much
capacitance.
Enable Function
The BW9910/BW9910A can be turned off by pulling the
PWM_D pin to ground. When the device is disabled, the
BW9910/BW9910A draws quiescent current of less than
1.0mA.
Output Open Circuit Protection
When the buck topology is used, and the LED is
connected in series with the inductor, there is no need
for any protection against an open circuit condition in the
LED string. Open LED connection means no switching
and can be continuous. In this case, since the output
voltage will be the same as input voltage, if there is a
capacitor connected across the output, this capacitor
should be able to withstand the peak value of the input
voltage.
Thermal Shut Down
Thermal protection is added due to buck topology can
generate large heat when operated with high voltage
input. The over temperature protection is activated to
shut down external MOSFET when the junction
temperature (TJ) reaches 150°C. There is a 50°C
hysteresis to re-start the MOSFET.
DC-DC Low Voltage Applications
Boost LED Driver
BW9910/BW9910A can also be used in boost
configurations – at reduced accuracy. The accuracy can
be improved by measuring the LED current with an Op-
Amp and use the Op Amp’s output to drive the LD pin.
Refer to Figure 1, a boost LED driver is used when the
total voltage drop of the output LED string is higher than
the input supply voltage. For example, the boost
topology can be appropriate when input voltage is
supplied by a 48V power supply and the LED string
consists of twenty HB LEDs, as the case may be for a
street light.
www.bruckewell-semi.com/














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