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Do LED lights flicker more than fluorescent?

by copperx 10y ago

djaychela 10y ago
I think if they're at the same frequency then they will appear to - the LED has a much sharper on/off curve than anything else. Certainly in one of the places I work they have new LED lights in the toilets and it's quite disconcerting as the strobing effect is noticeable. The LED lighting in the streets in my town (Bournemouth, UK) doesn't exhibit this, but certainly is very 'blue' at first, and my mother (who lives there) didn't realise the effect of the blue light in terms of sleep; she used to leave her curtains open at night and wasn't sleeping well. Closing them has helped greatly in that respect.
zkms 10y ago
Yes. Good fluorescent bulbs will have electronic ballasts (the driving circuit) that supply current to the bulb with a higher frequency (in the low kilohertz) than the time response of the bulb's phosphor. Thus, any sort of flicker gets low-pass filtered and doesn't appear in the output light. Even with a subpar magnetic ballast that drives the bulb with line frequency, the phosphor never gets close to fully extinguishing -- so there is flicker, but the instantaneous light output never gets less than, say, half the maximum instantaneous light output. Look on page 3 of http://www.usailighting.com/stuff/contentmgr/files/1/e18f88d078a54622682528e496596192/misc/flickerfactsheet_doe.pdf http://www.usailighting.com/stuff/contentmgr/files/1/e18f88d... for some instantaneous light vs time graphs for fluorescent bulbs. LEDs have a much higher frequency response (in the tens of megahertz, easily) -- they respond quicker and more faithfully replicate their electrical drive signal as light output. You can see on page 4 of that report how violently jagged the LED's light/time plots can get. If the manufacturer didn't want to include filter capacitors in the LED's driver because of cost/reliability concerns, well, I hope your eyes enjoy that signal because the LED, unlike the fluorescent bulb, isn't going to smooth it out.
- copperx 10y ago
  Oh wow -- for some reason I thought LED bulbs converted AC to DC internally and drove the light without flicker (assuming no PWM for dimming).
  - zkms 10y ago
    It's certainly possible to do so and doing so would indeed avoid any sort of flicker -- but cost-cutting (good capacitors that will last the life of the LEDs are expensive) reigns supreme alas.

Do LED lights flicker more than fluorescent?

by copperx 10y ago

Do LED lights flicker more than fluorescent?

I think if they're at the same frequency then they will appear to - the LED has a much sharper on/off curve than anything else. Certainly in one of the places I work they have new LED lights in the toilets and it's quite disconcerting as the strobing effect is noticeable. The LED lighting in the streets in my town (Bournemouth, UK) doesn't exhibit this, but certainly is very 'blue' at first, and my mother (who lives there) didn't realise the effect of the blue light in terms of sleep; she used to leave her curtains open at night and wasn't sleeping well. Closing them has helped greatly in that respect.

zkms 10y ago

Yes. Good fluorescent bulbs will have electronic ballasts (the driving circuit) that supply current to the bulb with a higher frequency (in the low kilohertz) than the time response of the bulb's phosphor. Thus, any sort of flicker gets low-pass filtered and doesn't appear in the output light. Even with a subpar magnetic ballast that drives the bulb with line frequency, the phosphor never gets close to fully extinguishing -- so there is flicker, but the instantaneous light output never gets less than, say, half the maximum instantaneous light output. Look on page 3 of http://www.usailighting.com/stuff/contentmgr/files/1/e18f88d078a54622682528e496596192/misc/flickerfactsheet_doe.pdf http://www.usailighting.com/stuff/contentmgr/files/1/e18f88d... for some instantaneous light vs time graphs for fluorescent bulbs. LEDs have a much higher frequency response (in the tens of megahertz, easily) -- they respond quicker and more faithfully replicate their electrical drive signal as light output. You can see on page 4 of that report how violently jagged the LED's light/time plots can get. If the manufacturer didn't want to include filter capacitors in the LED's driver because of cost/reliability concerns, well, I hope your eyes enjoy that signal because the LED, unlike the fluorescent bulb, isn't going to smooth it out.

copperx 10y ago
Oh wow -- for some reason I thought LED bulbs converted AC to DC internally and drove the light without flicker (assuming no PWM for dimming).
- zkms 10y ago
  It's certainly possible to do so and doing so would indeed avoid any sort of flicker -- but cost-cutting (good capacitors that will last the life of the LEDs are expensive) reigns supreme alas.