Texas Instruments LM3444 Buck-Boost Topology MR16 LED Bulb Reference Design LM3444MR16BBRB/NOPB LM3444MR16BBRB/NOPB Hoja De Datos
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LM3444MR16BBRB/NOPB
LM3444-MR16-Boost Reference Design
NATIONAL SEMICONDUCTOR
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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
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. The SSL replacement
bulb looks capacitive to the ELVT; therefore large current spikes charge the energy storage device within the SSL
MR16 bulb. The switching converter within the bulb then processes the input power from the energy storage
element to the LED load. At this time the minimum load requirement of the ELVT is not satisfied, and the ELVT
turns off. Once the energy is depleted within the MR16 converter, the ELVT will start up, and the process cycles.
The turning off/on of the ELVT will manifest itself as visible flicker.
Issue #2
– The maximum input current to the Halogen bulb is approximately 4.25A. The maximum input current to
the SSL bulb is approximately 12A. The large magnitude spike associated with charging the SSL MR16 input
capacitor can cause premature failures within the SSL bulb, or even the ELVT.
capacitor can cause premature failures within the SSL bulb, or even the ELVT.