suppress surge at the source on 120 vac house circuit ?

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The leds will blink at the switching frequency - probably 50kHz or so. Using the term ‘constant current’ is a tad confusing as it isn’t constant in a DC sense - the current is regulated. The switch transistor is turned on until the current reaches the required value then is switched off. Next cycle this is repeated and repeated.......
Thus the input voltage can vary and the leds can change with temperature, but the current remains regulated (within certain constraints).

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I have noticed when I look at an LED tube I have over my workbench with a photo diode and a scope I see something much like a square wave with a duty cycle greater than 50%

Notice the hidden mic in your lamp?---it is modulating the leds to form an optical link to the CIA van across the street surprise 

 

 

Line flicker can bother people (& maybe the cat?)...a better lamp runs at constant(DC)  current, with no flicker.  Fluorescents are similar--DC not allowed, but they can be driven with a high freq driver   

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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The flicker doesn't bother me.  Both the LED tube and fluorescents show 120Hz with a photo diode and scope.  I used to have trouble with flicker in the old days when my monitor refreshed at 60 Hz under fluorescent lighting in the work place.  Changing refresh rate to 70 Hz solved that problem.  As for the CIA van across the street, they have been there for so long they have their own parking meter.  Doesn't bother me any more. 

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