User Guide for
FEBFL7701_L30U003A
2.4W LED Ballast Using FL7701
Featured Fairchild Product:
FL7701
Direct questions or comments
about this evaluation board to:
“Worldwide Direct Support”
Fairchild Semiconductor.com
© 2012 Fairchild Semiconductor Corporation
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FEBFL7701_L30U003A • Rev.1.0.2
Table of Contents
1.
Introduction ............................................................................................................................... 3
1.1.
General Description.......................................................................................................... 3
1.2.
Key Features ..................................................................................................................... 3
1.3.
Internal Block Diagram .................................................................................................... 4
2.
General Specifications for Evaluation Board ........................................................................... 5
3.
Photographs of the Evaluation Board ....................................................................................... 6
4.
Printed Circuit Board ................................................................................................................ 7
5.
Schematic .................................................................................................................................. 8
6.
Bill of Materials ........................................................................................................................ 9
7.
Test Condition & Test Equipment ............................................................................................ 9
8.
Test Waveforms ...................................................................................................................... 10
8.1.
8.2.
8.3.
8.4.
8.5.
9.1.
9.2.
9.3.
9.4.
9.5.
Typical Waveforms: Startup .......................................................................................... 10
Operating frequency & minimum duty .......................................................................... 11
Typical waveforms: Steady State ................................................................................... 12
Typical waveforms: Abnormal Mode(LED Open) ........................................................ 15
Typical waveforms: Abnormal Mode (Inductor Short Condition) ................................ 16
Power Factor at Rated Load Condition .......................................................................... 17
System Efficiency .......................................................................................................... 18
THD Performance .......................................................................................................... 19
Thermal Performance ..................................................................................................... 20
EMI Results .................................................................................................................... 22
9.
Performance of Evaluation Board ........................................................................................... 17
10.
Revision History ..................................................................................................................... 24
© 2012 Fairchild Semiconductor Corporation
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FEBFL7701_L30U003A • Rev. 1.0.2
This user guide supports the Evaluation kit for the FL7701. It should be used in
conjunction with the FL7701 datasheet as well as Fairchild’s application notes and
technical support team. Please visit Fairchild’s website at
www.fairchildsemi.com.
1.
Introduction
This document describes the proposed solution for a universal-input 2.4W LED ballast
using the FL7701. The input voltage range is 90V
RMS
– 265V
RMS
and there is one DC
output with a constant current of 85mA at 28V
MAX
. This document contains general
description of FL7701, the power supply specification, schematic, bill of materials, and
the typical operating characteristics.
1.1.
General Description
The FL7701 LED lamp driver is a simple IC with PFC function. The special “adopted
digital” technique automatically detects input voltage condition and sends an internal
reference signal, resulting in high power factor. When an AC input voltage is applied to
the IC, the PFC function is automatically enabled. Otherwise, when a DC input is applied
to the IC, the PFC function is automatically disabled. The FL7701 does not require a bulk
capacitor (electrolytic capacitor) for supply rail stability, which can significantly affect
LED reliability.
1.2.
Key Features
Digitally Implemented Active PFC Function
Built-in Self-Biasing HV Startup Circuit
Application Input Range: 80V
AC
~ 308V
AC
AOCP Function with Auto-Restart Mode
Built-in Over-Temperature Protection
Cycle-by-Cycle Current Limit
Current-Sense Pin Open Protection
Low Operating Current: 0.85mA (Typical)
Under-Voltage Lockout with 5V Hysteresis
Programmable Oscillator Frequency
Programmable LED Current
Analog Dimming Function
Fixed Soft-Start Function
Precise Internal Reference: ±3%
© 2012 Fairchild Semiconductor Corporation
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FEBFL7701_L30U003A • Rev. 1.0.2
1.3.
Internal Block Diagram
Figure 1. Internal Block Diagram
Pin Descriptions
Pin
1
2
3
4
Symbol
CS
OUT
VCC
RT
Description
Current Sense.
Limits output current, depending on the sensing resistor
voltage. The CS pin is also used to set the LED current regulation.
Output.
Connects to the MOSFET gate.
Supply Voltage.
Supply pin for stable IC operation; ZCD signal detection used
for accurate PFC function.
Resistor.
Programmable operating frequency using an external resistor
connected to this PIN and the IC has fixed frequency when this pin is left open
or floating.
Analog Dimming.
Connects to the internal current source and can change the
output current using an external resistor. If ADIM is not used, connect a 0.1µF
bypass capacitor between ADIM and GND.
GROUND.
Ground for the IC.
No Connection
High Voltage.
Connect to the high-voltage line and supply current to the IC
5
6
7
8
ADIM
GND
NC
HV
© 2012 Fairchild Semiconductor Corporation
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FEBFL7701_L30U003A • Rev. 1.0.2
2.
General Specifications for Evaluation Board
All data for this table was measured at an ambient temperature of 25°C
Table 1.
Summary of Features and Performance
Symbol
V
IN,min
Input Voltage Range
V
IN,nom
V
IN,max
AC Input Frequency
Output Voltage/Current
Output Power
Efficiency
T
FL7701
Temperature
PCB Size
Initial Application
T
MOSFET
T
INDUCTOR
f
IN,min
f
IN,max
V
OUT
I
OUT
Output Power
Description
Value
90V
220V
265V
47Hz
64Hz
28V
85mA
2.41W
>78%
< 71.5°C
< 59.5°C
< 57.5°C
Note 2
At full load
Note 1
Comments
At full load (all at open frame, room
temperature / still air)
20mm (width) x 32mm (length) x 13mm
(height)
LED bulb
Notes:
1. The output current has I
LEDPK
ripple. To reduce ripple current, use a large electrolytic capacitor in
parallel with the LED. Ensure the capacitor voltage rating is high enough to withstand an open-LED
condition or use a Zener diode for protection.
2. The output power is not equal to the apparent power due to the slight phase shift between the output
voltage and current.
© 2012 Fairchild Semiconductor Corporation
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FEBFL7701_L30U003A • Rev. 1.0.2
