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[SOLVED] Multi independent PWM

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Xenon02

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Hello !

I have 24 high power LED drivers and each one of them requires independent PWM, is there any IC that has couple of independent PWM channels and I can program it using any interface ?
 

Hi,

each one of them requires independent PWM
Why independently?

and .. why no specifications? It makes a big difference whether you are looking for 16 bit 10 MHz PWM or 8 bit 1kHz PWM.
Also power supply, signal voltage levels, interface...

I did a quick internet search for "channel pwm generator ic" and immediately found LT8500.
Is this similar to what you are looking for?

Klaus
 
PSOC 5LP family :

1711306495291.png


This is a SOC, the screen shot is one chip solution. I added from its resource lib the USBUART as easy way to control
the solution from PC or whatever. If you wanted SPI or I2C or CAN or....thats also doable.

As you can see from its component catalog (a component is an onchip resource) there are lots of resources left for
other tasks.

Here is whats on the SOC, multiple copies in most cases :

1711306755465.png


Each component has a rich lib of f() calls to control in real time, so you are not
writing a bunch of drivers, rather just one at a high level.

IDE (PSOC Creator or MODBUS) and compiler free.

Dev board I think would do it ~ $15 CY8CKIT-059


Regards, Dana.
 
Last edited:

Why independently?

and .. why no specifications? It makes a big difference whether you are looking for 16 bit 10 MHz PWM or 8 bit 1kHz PWM.
Also power supply, signal voltage levels, interface...

I did a quick internet search for "channel pwm generator ic" and immediately found LT8500.
Is this similar to what you are looking for?

I have 30 LEDs that are 6W, 1A also all of them are parallel and not series, and they have to work independently so I can change the Width in the PWM for the brightness control of each led separately.
The one you've told me is the LED driver, but it is not a constant current driver so it might work !
I tried to type PWM generator IC and usually I found LED driver so I thought automatically that the output is constant current that with PWM can change how it works but this one is not a constant current but just a PWM.

Interface could be anything to be honest I just needed the PWM generator. I don't know how much the constant current driver takes current from PWM pin hmmmm the driver is : AL1791AFE-13, I found only PWM internal pulldown current but nothing of how much current it takes from PWM that I provide. And I don't know how much current I can take from the PWM generator you've told me. I am a bit clueless ;D
 

  1. What is the application and LED datasheet?
  2. What greyscale resolution?
  3. PWM must have a current limiter, not CC.
  4. Are you restricted by any DC supply ?
  5. Have you done a thermal design?
You may need 24 high active powers switches.
Do U know what to expect for the temperature of each LED with 24*6W ~150W
They are not electrically in parallel but might be thermally.
 
Last edited:

I added into design the onchip SAR and onchip MUX in order to monitor each LEDs
current draw. Allow you to match brightness or control patterns of brightness.

Again this is all one chip

1711328254985.png



Note you would need a current sense R in each LED channel to ground
for the SAR to sense current thru LED.


Regards, Dana.
 

I was also thinking how to find more elements like LT8500 because when I check the LED drivers they usually are constant current and not PWM output or they are constant current (sink) with PWM. But I was looking for only PWM output and not current sink IC / constant current output.
The LT8500 is kinda okey with that, it is PWM without constant current (sink). But usually I just find drivers with constant current and max 3 PWM.

Dana I see what you've showed me but I don't know what PSoC is neither I don't know how to use it or how it looks like. I was trying to find a specific IC because they are specialized in this particular thing.
This PSoC is similar to Logisim I used sometimes or FPGA using premade blocks.

I was looking just for PWM generator nothing more ;> Because I couldn't find anything just LED drivers so far but LT8500 is a good idea but wanted to know how to find more propositions to choose.
 

Hello!

Why independently?

Let's go back to the question. I don't think it's relevant to ask why independently,
that's his problem.
Let's assume he wants exactly what he says, powering LEDs, most likely each of them
with a different brighness, not more.

PWM are usually made using a counter.
Let's cal it C, and let's state that it counts from 0 to C-1.
You can make a PWM by defining counters, usually calld CCR.
And you have to specify the mode.

1. Set a max value, called C above.
2. Set a CCR value for led 1, let's call it CCR1
3. Set the mode. Processor dependent, but you can usually
say hat the output bit is set by 0 and reset by CCR1.

From 0 to CCR1 -1, the output bit will be 1
From CCR1, the output will be 0.

Here you are.

Now the number of LEDs addressable by PWM will depend on how many timers
you have and how many CCR registers you have for each timer.

is there any IC that has couple of independent PWM channels and I can program
it using any interface ?

Don't know what you mean by programming any IC using any interface, but here
is the deal: any processor having timers can do at least part of what you are
aiming to. Part of it only because I don't know any processor with that many
timers (I mean timers x CCR registers). Maybe some high end ST processors,
but in this case, it's a bit silly to use a 20 USD processor to blink LEDs.
Why not using a sub-dollar processor with one SPI input and a few PWM outputs?
In this case, you just need to address each of these processors with a "master"
processor which will decide which ratio to power which LED.

And the interface to program it... what about C language?

Dora.

Hello !

I have 24 high power LED drivers and each one of them requires independent PWM, is there any IC that has couple of independent PWM channels and I can program it using any interface ?
 

This is not hard to answer but without a LED datasheet, and answers to my previous post, you are making this almost impossible.

There are many LED backlit TV's with 12, 24 and 32 channels
 
Last edited:

Why independently?
I asked, because the OP states that the LED drivers need independent PWM...
.. while I in my house have several LED drivers connected in parallel (one common PWM)

So I understand it´s not the requirement by the LED driver to get independent PWM, but it´s the OP´s requirement to drive them independently.

I´m back when there are useful specifications. I just see a lot of riddles in text.
Microcontrollers can do soft_PWM ... it just depends on the PWM requirements asked in post#2.

Klaus
 

I was also thinking how to find more elements like LT8500 because when I check the LED drivers they usually are constant current and not PWM output or they are constant current (sink) with PWM. But I was looking for only PWM output and not current sink IC / constant current output.
The LT8500 is kinda okey with that, it is PWM without constant current (sink). But usually I just find drivers with constant current and max 3 PWM.

Dana I see what you've showed me but I don't know what PSoC is neither I don't know how to use it or how it looks like. I was trying to find a specific IC because they are specialized in this particular thing.
This PSoC is similar to Logisim I used sometimes or FPGA using premade blocks.

I was looking just for PWM generator nothing more ;> Because I couldn't find anything just LED drivers so far but LT8500 is a good idea but wanted to know how to find more propositions to choose.
Dana I see what you've showed me but I don't know what PSoC is neither I don't know how to use it or how it looks like.

Its a variant on FPGA in that you drag and drop various chip resources onto design canvas,
config with a right click, then route to pins and other blocks. It has ARM core in it and a
lot of analog, all routable. Each resource has its own lib of function calls to do real time
manipulation of resource, and timing is also done for you in the way part is speced and
laid out. Its rare you have to touch that. So pretty much all design work is done at high
level. It also has ability to do custom resources thru schematic capture and or Verilog. I
have added 64 bit shifters to it and 3 digit binary to BCD types of additions. Community
has added 74HC logic libs and cplds and DDS and.....Folks have used it to create oscilloscopes,
lab filters, instrumentation, tons of consumer products.....so the merge of routability + analog
+ logic + cpu all in one part. With new dual arm core parts crypto and non stop computing
easy to achieve and Bluetooth apps.....

So this is in it as standard lib parts in it, and using its fabric you can add to that.

1711360009210.png


Examples of projects done (tool has tons, community many more) :




It is a System On Chip.


Regards, Dana.
 
Last edited:

So I understand it´s not the requirement by the LED driver to get independent PWM, but it´s the OP´s requirement to drive them independently.

I´m back when there are useful specifications. I just see a lot of riddles in text.
Microcontrollers can do soft_PWM ... it just depends on the PWM requirements asked in post#2.

Okey so I am driving the LEDs with the driver AL1791AFE-13 for each 30 LEDs to make a lamp that can adapt it's brightness to the environment. So each LED has to have independent PWM is it now more sufficient ?

All I asked is the PWM generator multichannel, or rather how to find one. Because I usually find the LED constant current driver (the output is current sink) they have the PWM but I wanted just the PWM without constant current on the output.
I don't know what the PWM has to be that's why I asked how to find one ? I am still in a process of designing and I don't know all details yet because I recently (2-3 days ago) came up with idea of finding independent PWM to drive this LED Driver.
Microcontrollers usually have 3-4 independent PWM output, but I wanted to find an IC that is a PWM generator with many channels and each channel can be changed independently (the width of the output PWM signal).
 

Hi,

You seem to neither read posts nor datasheets.

Klaus
 
Last edited:

So the unknown LEDs are distributed on long wires with some independent light sensors unaffected by LEDs on long cables driven by a central PWM and current limiter.

I can imagine there will be many challenges with this concept.
 

You seem to neither read posts nor datasheets.

I read and I even said that some of the stuff that you require is still unknown for me I just asked a really simple question but seems to be to much.
Yup I don't read post why not and not datasheets because I have to understand everything why not.

Thanks I guess I'll try again on my own.

So the unknown LEDs are distributed on long wires with some independent light sensors unaffected by LEDs on long cables driven by a central PWM and current limiter.

I can imagine there will be many challenges with this concept.

I guess ?
Lamp in which each LED can have different brightness intensivity. Like each LED has this driver from Analog I have mentioned so there are 30 drivers from Analog. And each of them have the PWM input that requires to just give him the PWM signal. I have the drivers and etc just looking for PWM generator or how to find them because I usually read they are LED drivers or something.

But to be honest I didn't find a lot of help here so maybe I'll try again on my own ...
 
Thanks I guess I'll try again on my own.
In post#2 I asked for
*supply, signal voltage levels, interface...
--> did you answer the question?

***

In post#2 I told you about LT8500. I also asked:
* Is this similar to what you are looking for?
--> I still don´t know whether you find it suitable, and if not, why?

It took you 14 posts to eventually say what LED driver you use. ... that is the very information for frequency, signal levels, duty cycle .. asked in post#2

Still you say:
I don't know what the PWM has to be
While a PWM is defined by frequency, signal levels, duty cycle.

***

But yes, blame it on us!

Klaus
 

Hello !

I have 24 high power LED drivers and each one of them requires independent PWM, is there any IC that has couple of independent PWM channels and I can program it using any interface ?
Another option is the TLC5947 from Texas Instruments. It's a 24-channel PWM driver with a serial interface, allowing for independent control of each channel. You can program it using a variety of microcontrollers and interfaces.
 
It took you 14 posts to eventually say what LED driver you use. ... that is the very information for frequency, signal levels, duty cycle .. asked in post#2

Check post#5 I said which driver I use .... I have said what driver it is.


In post#2 I asked for
*supply, signal voltage levels, interface...
--> did you answer the question?

Supply, signal voltage levels as I have said is unknown for me because I don't know what level it must be. I wanted to know how to find these elements that are PWM generators and not LED drivers constant current with PWM dimming.
I've answered it the way I could.


In post#2 I told you about LT8500. I also asked:
* Is this similar to what you are looking for?
--> I still don´t know whether you find it suitable, and if not, why?

I said with excitement in post#5 that this is the PWM type of IC I am looking for but wanted to find more options.
It looks fine and suitable. I will have to figure out how to use him and that's all. But I can also search for more options right ? Like different interface. I don't mind this one I am just saying.

But I usually found only LED driver constant current with PWM dimming and not PWM generators when I typed PWM generators IC.


While a PWM is defined by frequency, signal levels, duty cycle.

***

But yes, blame it on us!

Sure I am the bad one. I am looking a way to search them ... The details what it has to be or what frequency of that PWM has to be is a detail I will look at when I find the way to find PWM generators to pick and choose which one suits me more ...
I don't know when you go to the store you already know what to buy ? You probably find something that has better price or better things you know what it is but you don't know which one exactly so you search which one is suitable, so I am looking for a key word in digikey or somewhere to find couple of PWM generators.
I only found LED driver constant current with PWM dimming and not PWM generators like LT8500 I want to find more of these. And find out which one is suitable.


I don't know how to ask this question, because I am not looking for a specific model of PWM generator but the way to find a bigger selection. Because I don't know yet ...

But yea my bad why not.
 

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