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Plain daily use LED light bulbs...
- Thread starter Externet
- Start date
schmitt trigger
- Joined Jul 12, 2010
- 2,027
Yes, but…. YMMV, Let me explain.
I once did that experiment because I felt that some of the harshness seen in some of the lower cost lamps was caused by the minimal amount of bulk capacitance causing voltage ripple and thus light flickering.
I set up a photodiode with associated its trans impedance amplifier to feed to a scope. Measuring the lamp’s light output in a darkened room, the flickering was evident although ameliorated by the phosphor latency. Similar to a fluorescent light with a magnetic ballast.
When the lamp was fed with well filtered DC, the flicker disappeared. Thus I proved that DC operation was feasible WITH THAT PARTICULAR LAMP’s CIRCUIT CONFIGURATION.
If your lamp circuit has some form of capacitive dropping or other circuit like PFC that requires an alternating or pulsating waveform, the lamp will not work. Other circuits rely on the supply waveform to drop to zero to reduce internal power dissipation.
I once did that experiment because I felt that some of the harshness seen in some of the lower cost lamps was caused by the minimal amount of bulk capacitance causing voltage ripple and thus light flickering.
I set up a photodiode with associated its trans impedance amplifier to feed to a scope. Measuring the lamp’s light output in a darkened room, the flickering was evident although ameliorated by the phosphor latency. Similar to a fluorescent light with a magnetic ballast.
When the lamp was fed with well filtered DC, the flicker disappeared. Thus I proved that DC operation was feasible WITH THAT PARTICULAR LAMP’s CIRCUIT CONFIGURATION.
If your lamp circuit has some form of capacitive dropping or other circuit like PFC that requires an alternating or pulsating waveform, the lamp will not work. Other circuits rely on the supply waveform to drop to zero to reduce internal power dissipation.
ronsimpson
- Joined Oct 7, 2019
- 4,646
I can't find the schematic right now, I have seen LED arranges to so plus current goes through half of the LED and negative goes through the other half. The + LEDs need to be very close to the -LED to reduce flicker. There is no driver. Much of the flicker came from variations in line voltage.
In some cases, we find the + half of the voltage measures different than the "-" half of the voltage. With some types of bulbs this causes flicker.
Most LEDs have "drivers" for many reasons.
Depending on where you live, the power line voltage varies. With out feedback the light will change with voltage. Flickering might be from a heavy load on the system. When I was designing light bulbs we argued about, should the light be held to 0.1% regulation from 90Vac to 240Vac or should the light change with voltage like the old bulbs. In flashlight (torches) some people want the amount of light to change with the health of the batteries and some people did not like that.
Some bulbs have almost unmeasurable ripple in the light. (120hz) and some, to reduce cost, we let the light output drop down during the "zero volts crossover time". Some want to zero output, and some went to 1/2 power.
There is flicker because the light is pulsing at 120 or 100hz just like fluorescent light.
Some of the field "flicker complaints" were caused by the error amplifier in the driver oscillating.
Some of the field "flicker complaints" were caused by light dimmers. The old dimmers did not like LEDs. The first LEDs drivers did not like any kind of dimmers.
In some cases, we find the + half of the voltage measures different than the "-" half of the voltage. With some types of bulbs this causes flicker.
Most LEDs have "drivers" for many reasons.
Depending on where you live, the power line voltage varies. With out feedback the light will change with voltage. Flickering might be from a heavy load on the system. When I was designing light bulbs we argued about, should the light be held to 0.1% regulation from 90Vac to 240Vac or should the light change with voltage like the old bulbs. In flashlight (torches) some people want the amount of light to change with the health of the batteries and some people did not like that.
Some bulbs have almost unmeasurable ripple in the light. (120hz) and some, to reduce cost, we let the light output drop down during the "zero volts crossover time". Some want to zero output, and some went to 1/2 power.
There is flicker because the light is pulsing at 120 or 100hz just like fluorescent light.
Some of the field "flicker complaints" were caused by the error amplifier in the driver oscillating.
Some of the field "flicker complaints" were caused by light dimmers. The old dimmers did not like LEDs. The first LEDs drivers did not like any kind of dimmers.
MisterBill2
- Joined Jan 23, 2018
- 27,164
You always see rectifiers in an AC powered LED circuit because without a diode to limit the reverse voltage and resulting reverse current the LED will be destroyed. The flicker of a rectified AC supplied LED is because of insufficient on time, often caused by design compromises.
