Which Driver Chip to be used for L.E.D.

[koolguy]

Hi,

I need a suggestion for driving L.E.D. several series and parallel combination, to be used at voltage less than ~80V to avoid shock.
The micro controller will be used for controlling it..!!

 

[alec_t]

You need to be more specific, Ritesh.

 

[koolguy]

Hello
I want to make led screen flashing effect so i use smps or rectifier which increase cost and size power i need some sort of const currrent like this

 

[ronsimpson]

Where are you getting the power from? Power line 220vac?? or 80vdc??
The "80 volts" is that the power in? or Is the 80 volts across the LEDs.

 

[koolguy]

Actually the main supply is 220v AC
so it will be used to drive LED string at 80v to avoid danger shock
rest is your suggestion

 

[ronsimpson]

Do you want to get from 220v ac to 80v dc (regulating current not voltage)? LEDs are current devices not voltage devices.
Do you want isolation? With out isolation the LEDs will be sitting on the power line.
What power level? 40 watts?

 

[koolguy]

So, what will be better ?
How to add isolation in it?
There will be several hundred leds to be connected

 

[ronsimpson]

So, what will be better ?

Many people don't understand LEDs. It is better to make a current regulator.

How to add isolation in it?

transformer. (small transformer)

There will be several hundred leds to be connected

I don't know how big you want to make the project. I would use 1 watt or 3 watt LEDs so there is a smaller number.

Please, how much power in watts?
I can send data on 20 watt or 100 watt or 2 watt.

 

[ronsimpson]

Here is a isolated design for 20 watts. (36 volts and 550mA)
http://www.powerint.com/sites/default/files/PDFFiles/der396.pdf
Is this what you are looking for?

 

[koolguy]

Actually, I need chip for constant current operating at line voltage will be also fine.
because at more voltage you can make large string less wire nest.
in slide you can see this type of led screens
**broken link removed**

 

[ronsimpson]

The PDF. that I pointed at is constant current, but it is built for a light bulb.

When I made LED signs each LED was addressable. (each LED could be turned on/off, color, brightness) There was no string. They ran from low voltage DC.
**broken link removed**
This picture (below) is probably the only one with a string of LEDs. The link in post #9 will do this job.
**broken link removed**

 

[koolguy]

Anyway, I found one thing more in L.E.D.'s that in string most probably one LED gets OFF and rest remain in working condition. why it happens to LED, what is reason behind it it should break all all but it passes current rest remain ON.

 

[alec_t]

If a LED fails short-circuit it will pass current to the remaining LEDs. If you are not using a constant-current source as the driver then the remaining LEDs in the string will get more current than before, so will be more likely to fail.

 

[koolguy]

If a LED fails short-circuit it will pass current to the remaining LEDs

OK, Sometimes it does not pass.
Why does it happens??

 

[audioguru]

Usually when an LED fails it does not conduct. In a series string then all LEDs do not light.
A semiconductor manufacturer makes an IC that detects a non-conducting LED because it has a high voltage across it then it shorts that LED allowing the remaining LEDs to light.

 

[koolguy]

Ok, I have seen that circuit is very typical.

 

[koolguy]

Usually when an LED fails it does not conduct. In a series string then all LEDs do not light.
A semiconductor manufacturer makes an IC that detects a non-conducting LED because it has a high voltage across it then it shorts that LED allowing the remaining LEDs to light.

My Brain needs to understand why does it happens, and how to detect the LED we are using is fine..which chip are you talking.
really curious to know more about LEDs

 

[koolguy]

hello
I have seen that LM3464 for driver purpose can you pls tell about is more about this projects....

 

[picbits]

hello
I have seen that LM3464 for driver purpose can you pls tell about is more about this projects....

Here you go, here is the datasheet, it has schematics and details about how to use it.
https://www.ti.com/lit/ds/symlink/lm3464.pdf

 

[audioguru]

My Brain needs to understand why does it happens, and how to detect the LED we are using is fine..which chip are you talking.
really curious to know more about LEDs

One of the semiconductor manufacturers makes the IC that detects a burned out open circuit LED and shorts it so that remaining LEDs in series with it continue to light.
All the traffic lights in my city use LEDs and I can see burned out LEDs in some of the lights. Each traffic light color has many LEDs so they are probably all in series. They must use that IC that shorts the open LEDs.

Most of the street lights in my city also use LEDs that are also probably in series. They are controlled by a modem with a little antenna on top, instead of being controlled by an LDR.