Is there any LED that works with ac directly?

[electronicman26]

hi
Is there any LED strip that work directly with AC voltage (without need driver or rectifier or ...)
https://www.theledlight.com/line-voltage-led-strip.html
or no, all leds work with dc? then if we want to supply them with ac we need driver?

before driver is ac and after it is dc?

 

[KlausST]

Hi,

LEDs are DC, current driven devices.
They can operate on AC with a driver circuit only.

The simplest us a diode and a resistor.

*****
If you talk about mains AC, then there is another problem.
The dangerous high AC mains voltage needs to be lowered and galvanically isolated, to prevent from electrical shock.

Klaus

 

[electronicman26]

Hi,

LEDs are DC, current driven devices.
They can operate on AC with a driver circuit only.

The simplest us a diode and a resistor.

*****
If you talk about mains AC, then there is another problem.
The dangerous high AC mains voltage needs to be lowered and galvanically isolated, to prevent from electrical shock.

Klaus

thanks for your reply
I am newbie in this field of study, I decide to have a Comprehensive comparison between T8 led tube that makes from strip leds and fluorscent lamps, in this way I meet some basic questions
a kind of t8 linear led tube (4ft and 20W) work with AC voltage and can replace as fluorscent lamp (ofcourse not need starter and ballast), It seems this type of lamp has a driver in its tube, is it true?
that the input of driver is ac voltage and output of it is dc voltage?
then the strip of leds drive with a dc voltage (for example 12 v) now what is the current? is it dc?
I read this paper :
https://www.sciencedirect.com/science/article/pii/S037877881200134X
I cant understand why the auther said the currnet of leds is non-sinusoidal and based on this discuss about power factor
if the input of leds(after driver circuit) is dc voltage and dc current, then why the auther said this?

 

[andre_luis]

Is there any LED that works with ac directly?

Even if hypothetically you could safety simplify your circuit eliminating transformer, such as with a kind of RCD network (diode rectifer+resistor+capacitor), you must be aware that LEDs used on this circuit topology are components having a much lower ability to handle the typical transients of electrical mains if compared with bulb lamps, burning easily, so that you must take certain precautions, such as the addition of suppression components if you expect some reliability on this product.

 

[KlausST]

Hi,

Yes, a LED tube has a driver inside.

DC LED current?
It will never be negative, but it bay be pulsed /pwm'd DC or any other wavform.

Power factor is only possible on the AC side. Here mains side.

Klaus

 

[FvM]

Modern mains supplied LED lamps have a built-in AC/DC converter, usually with high power factor. This is also the case for LED tube shown in post #1.

The quality of LED lighting has been considerably improving in the last years, the report compiled in 2012 may be outdated in several regards. I have no personal experience with retrofit LED tubes, todays LED bulbs are clearly superior to fluorescent energy saving lamps.

 

[electronicman26]

Hi,

Yes, a LED tube has a driver inside.

DC LED current?
It will never be negative, but it bay be pulsed /pwm'd DC or any other wavform.

Power factor is only possible on the AC side. Here mains side.

Klaus

Is it true that we say the input of driver circuit is AC voltage source (sinusoid) and the output voltage of driver (equal to input voltage of led strip) is DC?
can power factor just be defined for driver circuit? (the voltage of driver circuit is sinusoid but the current is non-sinusoid?? )
why the current waveform of a LED that drive with dc voltage may be pulsed ??