# led drivers in parallel



## reddly (Mar 21, 2013)

Hi,

I've recently joined the forum here in hopes to find an answer to a basic type of question that I've googled countless times and has left me only more confused.

I'm working on building an led. It's a bit of a pet project at the moment but if I can make it work then it will be a huge positive impact to myself and my family. 
So details:
-using 1 watt leds ( dx sku 133095 )
-using these stars ( dx sku 101147 )

-driving 320 mA, 30w constant current ( dx sku 42905 )


So my understanding is that I can wire up to 30 1 watt led in series from 1 driver (though not recommended) but 20-25 1 watt led from 1 driver should be fine.

What I don't understand is how many of the drivers can be wired in parallel? I was thinking it was simply 1 per 3 prong plug. Then I found a DIY that a person wired 3 drivers in parallel to a single 3 prong plug. So what are the limits to how many drivers I can wire in parallel? More importantly how do I figure this out ? (that way I can actually learn something) 

If anything else seems out of wack here let me know, this is my first real attempt at building something this large with multiple drivers in parallel and leds in such long strings.


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## monkeyboy (Mar 21, 2013)

:welcome: 
In response to your question; Yes of course you can.

As long as you're connecting a separate string of led's to each driver, there is no problem with wiring several drivers in parallel from the same plug. (although obviously you shouldn't exceed the maximum current that the plug can handle). Whether or not you can safely connect lots of wires into a single plug is a different matter though. I'm sure you'll figure something out.


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## reddly (Mar 21, 2013)

Thankyou for the quick reply. I suppose the next question is how do I determine how many drivers I can connect in parallel from a typical north american socket (120v, I assume probably 15amps) if the driver uses 30watts and has a CC of .350 mA ?

Rather how would I determine how many I can connect ? I'm sure there is some simple math involved in figuring it out but I'm unaware of what exactly I should be factoring in.


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## monkeyboy (Mar 22, 2013)

Note that 320mA is the output current not the input. Dealextreme doesn't state input current or power consumption though as it would vary with input voltage.

use P=IV to calculate max power for the socket.
Power(watts) = current(amps) x voltage(volts) = 15 x 120 = 1800W maximum

Let's guess that the worse case scenario power consumption is 60W, then we can connect about 30 drivers in parallel.


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## SemiMan (Mar 22, 2013)

reddly said:


> Hi,
> 
> I've recently joined the forum here in hopes to find an answer to a basic type of question that I've googled countless times and has left me only more confused.
> 
> ...




Just a bit of a word of caution, the output voltage from these drivers is high enough to give you a good shock, or a dangerous shock if you happen to be wet. There are no safety approvals on the unit and though it has one glowing review, 2 other people gave it 1 star which may indicate quality issues.

Semiman


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## reddly (Mar 22, 2013)

Wow! thats a lot of drivers.

I want to say a really big thankyou for all the help, especially showing me how you came to that number so that I can figure it out for myself in future. 

And Semiman, thankyou for your words of caution. Though I had looked at the reviews I hadn't given it to much thought. More consider a driver is a driver. But with those words of caution from someone far more experienced than I, perhaps I'll look around for another driver that might have been approved by one of the regulatory agencies. 

Big thankyou to both of you for your input and the time you've taken to help me out.


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## monkeyboy (Mar 22, 2013)

I'm curious as to what you're building with all those blue LED's? All I can think of is incredibly bright christmas tree lights.
if we know what you're building and what your budget is, we might be able to better help you.


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## reddly (Mar 22, 2013)

Well the blues are just one color that seemed simple to aquire and pretty cheap but I was planning on many colors to be honest. At the moment this is more of an experiment to see how I can make my own led lights for various applications (outside lighting, interior lighting, lamps, desk lights etcetc) around the house and if any of them work out, I intend to take them to my cabin. My cabin is off the grid so switching to leds is almost a must at this point. I was worried that I could only connect 2 or 3 drivers in parallel which would (and at the same time wouldn't) be a lot of leds. With the information you have provided I can work out whats possible, even if I step up to 3w leds.

If this works out with these cheap ones I may step up to 3w or 5w leds, and I may also try buying the ones that are pre-attached to the stars. But all that in time, for now its merely a little garage hobby work for me to play with. But my end goal is replace most of my cabin lighting with Leds, before using them for anything else.


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## monkeyboy (Mar 23, 2013)

That is not an optimal solution for indoor lighting. There are much better and much simpler solutions with current LED technology. For example, I would use a single cree MT-G2 (or MT-G) LED to light a whole room. In which case you wouldn't have to connect any drivers in parallel. This LED can put out more light than a 100W incandescent bulb and is far more efficient than those no-name 1W led's from DX. Probably cheaper too in terms of cost per lumen. The MT-G2 is a 12 die LED and comes in 3 different versions with the dice internally wired in different combinations of series and parallel which would give you more flexibility in terms of driver choice.

I would use the 36V 0.5A version for indoor use at home with mains power and the 9V 2A version or the 6V 3A version for battery power and/or outdoor use. You'd need to do some research to find adequate drivers for each situation. There are a lot of different drivers available that would be suitable. 

Also, don't forget about heat sinking. The LED(s) will need to be mounted to a large heat sink to dissipate the heat.


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## reddly (Mar 23, 2013)

I suppose it turns out that I have a lot more to learn. Off to start googling, I'm sure I'll be posting more questions back in the forum soon.

Monkeyboy I wanted to say it again, thankyou. I really appreciate all the time you have taken to help me with my questions and advice on what would work best given my circumstances.


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## seecol (Apr 3, 2013)

The FAN5607 constant-current parallel LED driver from Fair child Semiconductor provides analog and/or pulse-width-modulation brightness control for LCD back lighting in ultra-portable applications. It uses a three-mode charge pump and achieves 93% peak efficiency. Internal auto-sense circuitry maintains high efficiency, even when driving less than a maximum of four LEDs, and ensures very tight current matching over the full range of LED current. Also, it requires no external control signal to maintain efficiency when driving fewer than four LEDs. It comes in a 4- by 4-mm molded lead less package (MLP).


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## SemiMan (Apr 4, 2013)

seecol said:


> The FAN5607 constant-current parallel LED driver from Fair child Semiconductor provides analog and/or pulse-width-modulation brightness control for LCD back lighting in ultra-portable applications. It uses a three-mode charge pump and achieves 93% peak efficiency. Internal auto-sense circuitry maintains high efficiency, even when driving less than a maximum of four LEDs, and ensures very tight current matching over the full range of LED current. Also, it requires no external control signal to maintain efficiency when driving fewer than four LEDs. It comes in a 4- by 4-mm molded lead less package (MLP).




Curious as to how you expect a hobbyist with limited LED knowledge and limited electronics knowledge to implement a working circuit using the FAN5607 that only comes in a surface mount MLP package? The part is not even suitable for what he is doing.

Semiman


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