Texas Instruments Incorporated AN-2127 User's Guide
AN-2127 LM3448 A19 Edison Retrofit Evaluation Board
1 Introduction
This demonstration board highlights the performance of a LM3448 non-isolated LED driver solution that
can be used to power a single LED string consisting of eight to twelve series connected LEDs from a 85
V
to 135 V
RMS
This is a two-layer board using the bottom and top layer for component placement. The demonstration
board can be modified to adjust the LED forward current, the number of series connected LEDs that are
driven and the switching frequency. The topology used for this evaluation board eliminates the need for
passive power factor correction and results in high power factor with minimal component count which
results in a size that can fit in a standard A19 Edison socket. This board will also operate correctly and
dim smoothly using most standard TRIAC dimmers.
Refer to the LM3448 Phase Dimmable Offline LED Driver with Integrated FET (SNOSB51) data sheet for
detailed information regarding the LM3448 device. A schematic and layout have also been included along
with measured performance characteristics. A bill of materials is also included that describes the parts
used on this demonstration board.
, 60 Hz input power supply.
RMS
User's Guide
SNOA559B–October 2011–Revised May 2013
2 Key Features
• Drop-in compatibility with TRIAC dimmers
• Line injection circuitry enables PFC values greater than 0.85
• Adjustable LED current and switching frequency
• Flicker free operation
3 Applications
• Retrofit TRIAC Dimming
• Solid State Lighting
• Industrial and Commercial Lighting
• Residential Lighting
4 Performance Specifications
Based on an LED Vf= 3V
Symbol Parameter Min Typ Max
V
IN
V
OUT
I
LED
P
OUT
Input voltage 85V
LED string voltage - 36V -
LED string average current - 181mA -
Output power - 6.5W -
RMS
120V
RMS
135V
RMS
All trademarks are the property of their respective owners.
SNOA559B–October 2011–Revised May 2013 AN-2127 LM3448 A19 Edison Retrofit Evaluation Board
Submit Documentation Feedback
Copyright © 2011–2013, Texas Instruments Incorporated
1
20 40 60 80 100 120
0
50
100
150
200
LED CURRENT (mA)
INPUT VOLTAGE (V
RMS
)
Performance Specifications
www.ti.com
Figure 1. Demo Board
Figure 2. LED Current vs. Line Voltage (using TRIAC Dimmer)
2
AN-2127 LM3448 A19 Edison Retrofit Evaluation Board SNOA559B–October 2011–Revised May 2013
Copyright © 2011–2013, Texas Instruments Incorporated
Submit Documentation Feedback
80 90 100 110 120 130 140
50
100
150
200
250
300
350
LED CURRENT (mA)
INPUT VOLTAGE (V
RMS
)
12 LEDs
10 LEDs
8 LEDs
80 90 100 110 120 130 140
4
5
6
7
8
P
OUT
(W)
INPUT VOLTAGE V
RMS
12 LEDs
10 LEDs
8 LEDs
80 90 100 110 120 130 140
74
76
78
80
82
84
EFFICIENCY (%)
INPUT VOLTAGE (V
RMS
)
12 LEDs
10 LEDs
8 LEDs
80 90 100 110 120 130 140
0.78
0.80
0.82
0.84
0.86
0.88
0.90
POWER FACTOR
INPUT VOLTAGE V
RMS
12 LEDs
10 LEDs
8 LEDs
www.ti.com
5 Typical Performance Characteristics
TJ=25°C and VCC=12V, unless otherwise specified.
Figure 3. Efficiency vs. Line Voltage Figure 4. Power Factor vs. Line Voltage
Typical Performance Characteristics
Figure 5. LED Current vs. Line Voltage Figure 6. Output Power vs. Line Voltage
Figure 7. SW FET Drain Voltage Waveform Figure 8. COFF Voltage (CH1), Inductor Current (CH4)
(VIN=120V
SNOA559B–October 2011–Revised May 2013 AN-2127 LM3448 A19 Edison Retrofit Evaluation Board
Submit Documentation Feedback
RMS
, 12 LEDs, I
=181mA) (VIN=120V
LED
Copyright © 2011–2013, Texas Instruments Incorporated
, 12 LEDs, I
RMS
LED
=181mA)
3
EMI Performance
6 EMI Performance
120V, 6.5W Conducted EMI Scans
Figure 9. LINE – CISPR/FCC Class B Peak Scan Figure 10. NEUTRAL – CISPR/FCC Class B Peak Scan
www.ti.com
Figure 11. LINE – CISPR/FCC Class B Average Scan Figure 12. NEUTRAL – CISPR/FCC Class B Average
Scan
4
AN-2127 LM3448 A19 Edison Retrofit Evaluation Board SNOA559B–October 2011–Revised May 2013
Copyright © 2011–2013, Texas Instruments Incorporated
Submit Documentation Feedback
www.ti.com
Circuit Operation With Forward Phase TRIAC Dimmer
7 Circuit Operation With Forward Phase TRIAC Dimmer
The dimming operation of the circuit was verified using a forward phase TRIAC dimmer. Waveforms
captured at different dimmer settings are shown below:
Figure 13. Forward phase circuit at full brightness Figure 14. Forward phase circuit at 90° firing angle
Figure 15. Forward phase circuit at 135° firing angle
SNOA559B–October 2011–Revised May 2013 AN-2127 LM3448 A19 Edison Retrofit Evaluation Board
Submit Documentation Feedback
Copyright © 2011–2013, Texas Instruments Incorporated
5
Circuit Operation With Reverse Phase Dimmer
8 Circuit Operation With Reverse Phase Dimmer
The circuit operation was also verified using a reverse phase dimmer and waveforms captured at different
dimmer settings are shown below:
Figure 16. Reverse phase circuit at full brightness Figure 17. Reverse phase circuit at 90° firing angle
www.ti.com
Figure 18. Reverse phase circuit at 135° firing angle
6
AN-2127 LM3448 A19 Edison Retrofit Evaluation Board SNOA559B–October 2011–Revised May 2013
Copyright © 2011–2013, Texas Instruments Incorporated
Submit Documentation Feedback
www.ti.com
9 Thermal Performance
The board temperature was measured using an IR camera (HIS-3000, Wahl) while running under the
following conditions: VIN= 120V
NOTE: Thermal performance is highly dependent on the user's final end-application enclosure, heatsinking methods, ambient operating temperature, and PCB board layout in addition to the electrical
operating conditions. This LM3448 evaluation board is optimized to supply 6.5W of output power at room
temperature without exceeding the thermal limitations of the LM3448. However higher output power levels
can be achieved if precautions are taken not to exceed the power dissipation limits of the LM3448
package or die junction temperature. Please see the LM3448 datasheet for additional details regarding its
thermal specifications.
RMS
, I
= 181mA, # of LEDs = 12, P
LED
OUT
Thermal Performance
= 6.5W.
• Cursor 1: 65.3°C
• Cursor 2: 60.1°C
• Cursor 3: 67.6°C
• Cursor 4: 64.9°C
• Cursor 5: 65.6°C
Figure 19. Top Side - Thermal Scan
SNOA559B–October 2011–Revised May 2013 AN-2127 LM3448 A19 Edison Retrofit Evaluation Board
Submit Documentation Feedback
Copyright © 2011–2013, Texas Instruments Incorporated
7
Thermal Performance
www.ti.com
• Cursor 1: 68.1°C
• Cursor 2: 64.7°C
• Cursor 3: 62.6°C
• Cursor 4: 61.7°C
Figure 20. Bottom Side - Thermal Scan
8
AN-2127 LM3448 A19 Edison Retrofit Evaluation Board SNOA559B–October 2011–Revised May 2013
Copyright © 2011–2013, Texas Instruments Incorporated
Submit Documentation Feedback
1
4
3
2
16
13
14
15
ASNS
DIM
GND
FLTR1
COFF
FLTR2
5 12
BLDR
ISNS
11
NC
NC
VCC
GND
10
8 9
SW
SW
6
7
SW
SW
www.ti.com
10 LM3448 Device Pin-Out
Pin # Name Description
1, 2, 15, SW Drain connection of internal 600V MOSFET.
16
3, 14 NC No connect. Provides clearance between high voltage and low voltage pins. Do not tie to GND.
4 BLDR Bleeder pin. Provides the input signal to the angle detect circuitry. A 230Ω internal resistor ensures BLDR is
5, 12 GND Circuit ground connection.
6 V
7 ASNS PWM output of the TRIAC dim decoder circuit. Outputs a 0 to 4V PWM signal with a duty cycle proportional
8 FLTR1 First filter input. The 120Hz PWM signal from ASNS is filtered to a DC signal and compared to a 1 to 3V,
9 DIM Input/output dual function dim pin. This pin can be driven with an external PWM signal to dim the LEDs. It
10 COFF OFF time setting pin. A user set current and capacitor connected from the output to this pin sets the
11 FLTR2 Second filter input. A capacitor tied to this pin filters the PWM dimming signal to supply a DC voltage to
13 ISNS LED current sense pin (internally connected to MOSFET source). Connect a resistor from ISNS to GND to
pulled down for proper angle sense detection.
Input voltage pin. This pin provides the power for the internal control circuitry and gate driver. Connect a
CC
22µF (minimum) bypass capacitor to ground.
to the TRIAC dimmer on-time.
5.85 kHz ramp to generate a higher frequency PWM signal with a duty cycle proportional to the TRIAC
dimmer firing angle. Pull above 4.9V (typical) to TRI-STATE® DIM.
may also be used as an output signal and connected to the DIM pin of other LM3448/LM3445 devices or
LED drivers to dim multiple LED circuits simultaneously.
constant OFF time of the switching controller.
control the LED current. Could also be used as an analog dimming input.
set the maximum LED current.
LM3448 Device Pin-Out
Figure 21. Device Pin-Out
Table 1. Pin Description 16 Pin Narrow SOIC
SNOA559B–October 2011–Revised May 2013 AN-2127 LM3448 A19 Edison Retrofit Evaluation Board
Submit Documentation Feedback
Copyright © 2011–2013, Texas Instruments Incorporated
9
Loading...