Another LED tube from China

The vendor of the LED tube exchanged the temporary tube with another using surface-mounted LEDs, which is an improvement due to consistency of the pick-n-place machine instead of manual assembly using cheap Chinese labor. I insisted on getting the SMD version because its spatial light distribution is more suitable to my kitchen ambient lighting.

SPECIFICATION:

Input power: 20 watts, measured 22 watts
Input voltage range: 110-220VAC
Number of LEDs: 288
Power factor: > 0.9; measured 0.8
Color temperature: 4000K

My comment:

Given the input voltage range, its power supply is most likely a flyback converter. That means that there is an output electrolytic capacitor that will limit the life of the lamp to about 5 years, more likely less than 5 years. Flyback power supply is not the most efficient power supply money can buy, therefore you get what you pay: power supply efficiency lower than 80%, more like 75%.

The lamp comprises paralleled banks of 12 LEDs in series with a current equalizing resistor. There're 288 LEDs, thus each LED is rated for less than 76 milliwatts, because the series resistors eat up some power.

Again the uninspired manufacturer went for the obvious: use the extant form factor of the fluorescent tube the LED tube is designed to replace.

What is wrong with that approach?

First, the use of 288 small LEDs means that the life of the LED tube is much lower than the rated life of the LED used, which is typically 10,000 hours, not the 100,000 hours for the high-brightness LEDs which are designed with appropriately low thermal resistance to last that long.

Second, the LED has more glare than the fluorescent tube it replaces, due to the much higher brightness of the LEDs used vs. the low-light-density of phosphors used in fluorescent tubes. It is not economical to use any sort of optics or lenses to control the beam spread to say 60 degrees vs. the normal 180 degrees. That means that if used in a hallway, from far away the persons to try to see are masked by the glare from the tubes.

In summary, the inherent glare and the relatively short life of the built-in flyback power supply will not make this LED tube a good financial move.