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FL7701MX Schematic ( PDF Datasheet ) - Fairchild Semiconductor

Teilenummer FL7701MX
Beschreibung Smart LED Lamp Driver IC
Hersteller Fairchild Semiconductor
Logo Fairchild Semiconductor Logo 




Gesamt 13 Seiten
FL7701MX Datasheet, Funktion
June 2013
FL7701
Smart LED Lamp Driver IC with PFC Function
Features
Digitally Implemented Active PFC Function
(No Additional Circuit Necessary for High PF)
Built-in HV Supplying Circuit: Self Biasing
Application Input Range: 80 VAC ~ 308 VAC
AOCP Function with Auto-Restart Mode
Built-in Over-Temperature Protection Function
Cycle-by-Cycle Current Limit
Current-Sense Pin Open Protection
Low Operating Current: 0.85 mA (Typical)
Under-Voltage Lockout with 5 V Hysteresis
Programmable Oscillation Frequency
Programmable LED Current
Analog Dimming Function
Soft-Start Function
Precise Internal Reference: ±3%
Applications
LED Lamp for Decorative Lighting
LED Lamp for Low-Power Lighting
Description
The FL7701 LED lamp driver is a simple IC with PFC
function. The special adopted digitaltechnique of the
IC can automatically detect input voltage condition and
send an internal reference signal for achieving high
power factor. When AC input is applied to the IC, PFC
function is automatically enabled. Otherwise, when DC
input is applied to the IC, PFC function is automatically
disabled. The FL7701 does not need a bulk capacitor
(electrolytic capacitor) for supply rail stability, which can
significantly affect to LED lamp system.
Related Resources
Evaluation Board: FEBFL7701_L30U003A
Ordering Information
Part Number
Operating
Temperature Range
FL7701MX
-40°C to +125°C
Package
Packing Method
8-Lead, Small Outline Integrated Circuit (SOIC),
JEDEC MS-012, .150-inch Narrow Body
Tape & Reel
© 2011 Fairchild Semiconductor Corporation
FL7701 • Rev. 1.0.4
www.fairchildsemi.com






FL7701MX Datasheet, Funktion
Functional Description
The FL7701 is a basic PWM controller for buck
converter topology in Continuous Conduction Mode
(CCM) with intelligent PFC function using a digital
control algorithm. The FL7701 has an internal self-
biasing circuit that uses the high-voltage switching
device. The IC does not need an auxiliary powering
path to the VCC pin typical in flyback control ICs or PSR
product family.
When the input voltage applied to the HV pin is over
25 V to 500 V, the FL7701 maintains a 15.5 V DC
voltage at the VCC pin for stable operation. The FL7701
has UVLO block functions such that when the VCC
voltage rises higher than VCCST+, the internal UVLO
block releases and starts operation. Otherwise the VCC
goes down to the VCCST- and IC operation stops.
Normally, the hysteresis function provides stable
operation even if the input voltage is operating under
the very noisy or unstable circumstances.
The FL7701 has a smart internal digital block for
determining input condition: AC or DC. When an AC
source with 50 Hz or 60 Hz is applied to the IC, the IC
automatically changes its internal reference signal,
which is similar to input signal, for creating high power
factor. Otherwise, once the DC source connects to the
IC, the internal reference immediately changes to DC.
1. Soft-Start Function
The FL7701 has an internal soft-start function to reduce
inrush current at startup. When the IC starts operation
following an internal sequence, the internal reference
slowly increases for a pre-determined fixed time. After
this transient period, the internal reference goes to a
steady-state level. In this time, the IC continually tries to
find phase information from the VCC pin. If the IC
succeeds in getting phase information, it automatically
follows a similar shape reference made during the
transient times, 7 periods. If not, the IC has a DC
reference level.
Vbridge
ILED
power for the IC, has voltage ripple as well as the
rectification voltage after bridge, changing voltage level
according to the VCC capacitor value. Using this kind of
voltage fluctuation on the VCC pin, the IC can detect
the time reference and create the internal ZCD signal.
For precise and reliable internal reference for input
voltage signal, the FL7701 uses a digital technique
(sigma/delta modulation) and creates a new internal
signal (DAC_OUT) that has the same phase as the
input voltage, as shown in Figure 5. This signal enters
the final comparator and is compared with current
information from the sensing resistor.
Vbridge
Bridge Diode
Output Voltage
VCC
ZCD
DAC_OUT
Input Voltage
Peak
JFET Output
Voltage
Vdd Charging Voltage
JFET Output Voltage
t
t
t
Figure 5. Internal PFC Function
t
3. Self-Biasing Function
The self-biasing function, using an HV device, can
supply enough operating current to the IC and
guarantee similar startup time across the whole input
voltage range (80 V~308 VAC). However, self-biasing
has a weakness in high-voltage condition. Normally,
the HV device acts as constant current source, so the
internal HV device has power loss when high input
voltage connects to the HV pin. This power loss is
proportional to input voltage. To reduce this power
loss, one of the possible solutions is an additional
resistor between the input voltage source and the HV
pin, as shown in Figure 6.
Bridge
Diode
EMI filter
T/2 = 1/(Input Frequency * 2)
7*(T/2)
Normal Operation
Figure 4. Soft Starting Function in AC Input Mode
2. Internal PFC Function: How to Achieve
High Power Factor
The FL7701 has a simple, but smart, internal PFC
function that does not require additional detection pins
for detecting input phase information or an electrolytic
capacitor for supply voltage stabilization. For achieving
high PF, the FL7701 does not use the rectification
capacitor after the bridge diode. This is important
because the IC instead uses fluctuation in the signal on
the VCC pin. Basically, the VCC pin, which is supplies
© 2011 Fairchild Semiconductor Corporation
FL7701 Rev. 1.0.4
6
U1
HV
ADIM
RT
VCC
OUT
CS
GND
Figure 6. High-Voltage Application
www.fairchildsemi.com

6 Page









FL7701MX pdf, datenblatt
Physical Dimensions
6.20
5.80
5.00
4.80
3.81
8
A
5
B
4.00
3.80
1.75
0.65
5.60
PIN ONE
INDICATOR
(0.33)
1
0.25
0.10
1.75 MAX
4
1.27
0.25
CBA
1.27
LAND PATTERN RECOMMENDATION
SEE DETAIL A
0.25
C 0.19
R0.10
R0.10
0.90
0.40
0.51
0.33
0.10
OPTION A - BEVEL EDGE
0.50
0.25
x 45°
GAGE PLANE
0.36
OPTION B - NO BEVEL EDGE
NOTES: UNLESS OTHERWISE SPECIFIED
SEATING PLANE
(1.04)
DETAIL A
SCALE: 2:1
A) THIS PACKAGE CONFORMS TO JEDEC
MS-012, VARIATION AA.
B) ALL DIMENSIONS ARE IN MILLIMETERS.
C) DIMENSIONS DO NOT INCLUDE MOLD
FLASH OR BURRS.
D) LANDPATTERN STANDARD: SOIC127P600X175-8M.
E) DRAWING FILENAME: M08Arev14
F) FAIRCHILD SEMICONDUCTOR.
Figure 26. 8-Lead, Small-Outline Integrated Circuit (SOIC), JEDEC MS-012, .150-Inch Narrow Body
Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner
without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify
or obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically
the warranty therein, which covers Fairchild products.
Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings:
http://www.fairchildsemi.com/packaging/.
© 2011 Fairchild Semiconductor Corporation
FL7701 Rev. 1.0.4
12
www.fairchildsemi.com

12 Page





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