Reference Design Lighting Power Products Longmont Design Center LM3444 MR16 Boost Reference Design for Non-Dimming & Dimming LED Applications Feb 13, 2012 Revision 3.
Table of Contents MR16 Halogen/SSL Retro-Fit Analysis ...................................................................................................................... 3 Differences between Magnetic and Electronic Transformers .................................................................................................... 3 SSL MR16 lamps compatibility concerns with ELVT and ELV dimmers (true retro-fit) ...............................................................
MR16 Halogen/SSL Retro-Fit Analysis Differences between Magnetic and Electronic Transformers Magnetic Transformers Magnetic transformers step down 120VAC line voltage to 12VAC. Magnetic transformers consist only of magnetic core, and copper wire, no electronics are used to step down the voltage from 120VAC to 12VAC. Due to the fact that the frequency of operation is 50Hz or 60Hz, the size of the Magnetic transformers is large and heavy.
Halogen vs SSL MR16 waveforms Halogen MR16 waveforms Improper SSL MR16 operating waveform Channel - 1 (yellow trace) = Input line voltage Channel - 3 (purple trace) = Input line current Channel - 4 (green trace) = bulb current Issue #1 - The two scope captures above illustrate the SSL MR16 technical challenges. Figure one shows typical Halogen MR16 waveforms, and figure two is common MR16 replacement bulbs waveforms.
Halogen MR16 Summary: No flickering observed. There is a delay (1.12ms, 24° angle) from when the supply voltage starts ramping up from zero volts to when the electronic transformer starts to operate and the bulb turns on. This delay shows up on the LED MR16s as well although the magnitude of delay does vary from bulb to bulb. No current spikes observed out of the transformer. The bench set-up diagram below was used in the evaluation of the halogen MR16 bulb.
VIN (Yellow), IIN (Magenta), IBULB (Green) VBULB (Blue), IBULB (Green) LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR Page 6 of 20
LM3444 Boost MR16 Reference Design This reference design was based on the released LM3444 IC from National Semiconductor. This design was developed to minimize the current spikes coming out of an electronic transformer to less than 5A, which is a typical transformer rating, when driving an LED MR16 circuit.
PCB Schematic PCB Layout LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR Page 8 of 20
Bill of Materials Designator Description MFG Part Number C1 CAP, CERM, 1.0uF, 25V, +/-10%, X5R, 0805 MuRata GRM216R61E105KA12D C2 CAP, ELECT, 220uF, 35V, +/-20%, Radial 8x11.5mm Panasonic ECA-1VHG221 C3 CAP, CERM, 22uF, 25V, +/-10%, X5R, 1210 MuRata GRM32ER61E226KE15L C4 CAP, CERM, 330pF, 100V, +/-5%, X7R, 0603 AVX 06031C331JAT2A C5 CAP, CERM, 4.7uF, 50V, +/-10%, X7R, 1210 MuRata GRM32ER71H475KA882 C6 CAP, CERM, 4.
Typical Performance (Eight series LEDs) Bench Circuit I1 LINE 120VAC Power Supply NEUTRAL I3 I2 Vp Vs Transformer V1 (Electronic) Vp Vs VIN V2 LM3444 MR16 LED Driver VIN LED Board LED+ V3 LED- The following scope plots show voltage and current waveforms designated by the labels indicated in the following bench set-up diagram. The electronic transformer used was the Lightech LET-75.
CH2 V1 Voltage, CH4 I2 Current 4.
CH2 V2 Voltage, CH4 I2 Current LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR Page 12 of 20
LM3444 MR16 Boost evaluation board Dimming Waveforms Bench Circuit I1 Vp LINE 120VAC Power Supply V1 Triac Dimmer V2 NEUTRAL I4 I3 I2 Vs Transformer ( Electronic ) Vp Vs VIN V3 VIN LED Board LED+ LM3444 MR16 LED Driver V4 LED- This LM3444 MR16 Boost evaluation board is designed to operate (flicker-free) with common Electronic Low Voltage dimmers, and Electronic Transformers.
LM3444 MR16 Boost - Eight series connected LEDs at 100mA (45° Conduction Angle) CH2 V2 Voltage, CH4 I4 Current LM3444 MR16 Boost - Eight series connected LEDs at 10mA (minimum Conduction Angle) CH2 V2 Voltage, CH4 I4 Current LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR Page 14 of 20
Thermal Analysis LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR Page 15 of 20
Reference Design Transformer Compatibility The following transformers were tested with the National LED driver designs described in this document. A compatibility matrix is shown below which describes which driver/transformer combinations are suitable (i.e. no flicker, stable operation).
Performance with 7 LEDs Performance without transformer The table below compares the performance of each reference design when powered directly by a 12VAC source LM3441 BOOST 7 LEDs 11.91 0.708 7.97 23.55 0.281 6.62 83.0% 0.948 Units VAC A W VDC A W - Specs VIN IIN PIN (1) VOUT (1) ILED (2) POUT Efficiency Power Factor LM3444 BOOST 7 LEDs 120 0.07 8.18 23.5 0.270 6.23 77.6% 0.970 Units VAC A W VDC A W - Specs VIN IIN PIN VOUT ILED POUT Efficiency Power Factor LM3444 BOOST 7 LEDs 2 LEDs 120@ 1A 0.
Performance with 8 LEDs Performance without transformer The table below compares the performance of each reference design when powered directly by a 12VAC source LM3441 BOOST 8 LEDs 11.91 0.682 7.66 26.64 0.238 6.34 82.8% 0.946 Units VAC A W VDC A W - Specs VIN IIN PIN VOUT ILED POUT Efficiency Power Factor LM3444 BOOST 8 LEDs 120 0.067 7.86 26.5 0.230 6.10 77.5% 0.970 Units VAC A W VDC A W - Specs VIN IIN PIN VOUT ILED POUT Efficiency Power Factor LM3444 BOOST 8 LEDs 2 LEDs 120@ 1A 0.069 7.82 26.5 0.
Performance with 9 LEDs Performance without transformer The table below compares the performance of each reference design when powered directly by a 12VAC source LM3441 BOOST 9 LEDs 11.92 0.668 7.51 28.25 0.220 6.22 82.8% 0.946 Units VAC A W VDC A W - Specs VIN IIN PIN VOUT ILED POUT Efficiency Power Factor LM3444 BOOST 9 LEDs 120 0.066 7.74 28.0 0.215 6.02 77.8% 0.970 Units VAC A W VDC A W - Specs VIN IIN PIN VOUT ILED POUT Efficiency Power Factor LM3444 BOOST 9 LEDs 2 LEDs 120@ 1A 0.068 7.64 28.0 0.
Revision History Date 10/14/2011 02/13/2012 Author David Zhang David Zhang Revision 2 3 LM3444-MR16-Boost Reference Design Description Added D9 Change D9 P/N NATIONAL SEMICONDUCTOR Page 20 of 20
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