Texas Instruments LM3444 Buck-Boost Topology MR16 LED Bulb Reference Design LM3444MR16BBRB/NOPB LM3444MR16BBRB/NOPB Fiche De Données
Codes de produits
LM3444MR16BBRB/NOPB
LM3444-MR16-Boost Reference Design
NATIONAL SEMICONDUCTOR
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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. Magnetic
transformers are primarily available in two types of construction; torroidal and laminated EI core.
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. Magnetic
transformers are primarily available in two types of construction; torroidal and laminated EI core.
With existing Halogen MR16 systems that require dimming, Magnetic Low Voltage Dimmers are required to be
used.
used.
Electronic Transformers
Electronic transformers also step down 120VAC line voltage to 12VAC. Electronic transformers are much smaller
and more efficient than magnetic transformers. Electronic transformers are more common than magnetic
transformers in existing Halogen MR16 system. Electronic Low Voltage Transformers (ELVT) consists of a small
self resonant tank power supply. Electronic Low Voltage Dimmers (ELV dimmers) are used with ELVT for dimming
systems.
and more efficient than magnetic transformers. Electronic transformers are more common than magnetic
transformers in existing Halogen MR16 system. Electronic Low Voltage Transformers (ELVT) consists of a small
self resonant tank power supply. Electronic Low Voltage Dimmers (ELV dimmers) are used with ELVT for dimming
systems.
Although electronic transformers are more complex, with many more components, that their magnetic counterparts,
electronic transformers are far less expensive and smaller. The shear amount of core material and copper within a
magnetic transformer adds cost, and the weight of the product makes it expensive to manufacture, and ship.
electronic transformers are far less expensive and smaller. The shear amount of core material and copper within a
magnetic transformer adds cost, and the weight of the product makes it expensive to manufacture, and ship.
SSL MR16 lamps compatibility concerns with ELVT and ELV dimmers (true retro-fit)
Electronic transformers modulate (PWM) the input AC voltage with a frequency of 35 kHz to150 kHz. This
waveform is step-down from 120V or 230V (typical) to 12VAC with a transformer. The higher switching frequency
allows for the smaller magnetic components, and the overall smaller design. As mentioned earlier, the electronic
transformer is a self driven resonant half bridge topology. The self resonance half-bridge topology requires the
converter to have a minimal load at all times to function properly. Common minimum loads for ELV dimmers are
from 6W
waveform is step-down from 120V or 230V (typical) to 12VAC with a transformer. The higher switching frequency
allows for the smaller magnetic components, and the overall smaller design. As mentioned earlier, the electronic
transformer is a self driven resonant half bridge topology. The self resonance half-bridge topology requires the
converter to have a minimal load at all times to function properly. Common minimum loads for ELV dimmers are
from 6W
– 12W depending on manufacture, and maximum power rating of the ELVT. With traditional Halogen
lamps, the minimal load is of no concern, common Halogen MR16 lamps use about 50W of power per lamp. These
lamps are very inefficient, and 10W of Halogen power produces very little light.
lamps are very inefficient, and 10W of Halogen power produces very little light.
With the current efficacy of the LEDs above 100 lumens per watt, 6W of SSL power is equivalent to about 40W to
50W of Halogen power. One can quickly see the compatibility
50W of Halogen power. One can quickly see the compatibility
issue of SSL MR16 lamps and the ELVT’s. If the
output power of the ELVT reduces below the minimum requirement, the ELV dimmer will stop operating. The
turning on, and off of the ELVT will cause visible flicker from the SSL MR16 lamp, and could also cause reliability
issues with the lamp or ELVT.
turning on, and off of the ELVT will cause visible flicker from the SSL MR16 lamp, and could also cause reliability
issues with the lamp or ELVT.