horticulture led lamp - constant current circuit to drive LEDs, efficiency and heat problems

Thread Starter

andrea8723432

Joined Nov 6, 2020
9
Hi, I'm andrea.
I study electronic engineering and I'm trying to design horticulture led lamp. I'm sorry but I don't speak English very well.
I have designed some constant current circuits but now I want to design something different with modular approch.
can I post links to products?
I have chosen the LEDs (2 LEDs): 37 Volt, 720 mA --> 24.5 W
I have chosen the LED heat sink.
My project consists of a 60-100 watt power source, 4 leds in parallel. I need to convert 220v AC power line to 37 V DC. I didn't choose the 220V ac-dc main power supply so I don't know its output voltage (it could be 40 Volts). I want to design the most efficient constant current circuit for drive every single led.
I've chosen to power the LEDs in parallel and not in series because I want to use a modular approach (if I want to use 10 LEDs I just have to change the power supply).
I want to design an efficient circuit with minimal heat problem. could you help me find the most suitable components to drive the leds? I know how to design constant current circuit but I don't know which one is the best.
can I post links to products and sites?
Thank you
Andrea
 

bertus

Joined Apr 5, 2008
21,258
Hello,

You do not need a 37 Volts power source, but a 700 mA constant current source.
Leds are current driven and not voltage.

Bertus
 

Thread Starter

andrea8723432

Joined Nov 6, 2020
9
This is another problem. I have found many boards and products that perform the function I am looking for. these products are similar to the ones you linked to me but I don't want to buy from chinese sites. the other problem is that i cant spend much money.

I can write here the specifications that I have decided for my project:
- quite cheap;
- I want to use only one main power line;
-I don't want to use components from chinese sites like aliexpress. I always use Chinese boards and components because they perform functions well and are cheap. this time I want to use safer and more reliable electronic components.

I would like to buy everything from sites that I believe are reliable such as mouser or digikey, and I want to sell products quickly.
thanks
 
You can't parallel LEDs unless you parallel a set of (LED+Resistor). Your most efficient method would be PWM and not really constant current, but constant average current.

To get your raw voltage you will need to design a line switchmode power supply with isolation.
 

Thread Starter

andrea8723432

Joined Nov 6, 2020
9
You can't parallel LEDs unless you parallel a set of (LED+Resistor). Your most efficient method would be PWM and not really constant current, but constant average current.

To get your raw voltage you will need to design a line switchmode power supply with isolation.
Are you sure? the solution proposed by bertus seems good to me.
https://www.mouser.com/ProductDetail/MEAN-WELL/LDD-700H?qs=erfQA2AIGbXYF3x8KGE0pA==
I can connect one LDD-700H in series to every LED end connect the four pairs in parallel.
 

Thread Starter

andrea8723432

Joined Nov 6, 2020
9
Hello,

Did you have a look at what I posted:
He could have a look at some 700 mA meanwell drivers:
https://nl.mouser.com/MEAN-WELL/Power/Power-Supplies/LED-Power-Supplies/_/N-axgjt?P=1yxt6tzZ1z0zl9b

Bertus
this solution seems good to me. I found https://www.mouser.com/ProductDetail/MEAN-WELL/LDD-700H?qs=erfQA2AIGbXYF3x8KGE0pA==
I would like to power with 720 mA and not 700 mA but I don't find anything cheap.
I want to design a component like this to save money. the problem is efficiency and heat.
Do you have any idea what could be the best custom alternative?
Do you have a tip on how to economically convert 220VAC to 9-56Vin of LDD-700H component?
Thanks for all
 

Thread Starter

andrea8723432

Joined Nov 6, 2020
9
I need to design a led block with this https://www.mouser.com/ProductDetail/MEAN-WELL/LDD-700H?qs=erfQA2AIGbXYF3x8KGE0pA== in series to the LED. I want these blocks in parallel. I don't want use one component to drive 2 or 3 leds.
can you answer to this part of my message?
"
I would like to power with 720 mA and not 700 mA but I don't find anything cheap.
I want to design a component like this to save money. the problem is efficiency and heat. Do you have any idea what could be the best custom alternative?
Do you have a tip on how to economically convert 220VAC to 9-56Vin of LDD-700H component?
"
Thanks
Andrea
 

Thread Starter

andrea8723432

Joined Nov 6, 2020
9
Hello,

When you want to drive single leds, have a look at this 700 mA driver:
https://nl.mouser.com/ProductDetail/MEAN-WELL/APC-35-700?qs=21bV/TPs%2Bw9S34m0jXtW0A==

You will not notice the difference between 700 and 720 mA.

Bertus
maybe I haven't explained my problem well.
I have attached the idea of the project. the constant_current_circuit+LEDs blocks are connect in parallel
is it okay to use LDD-700H series component with a 37v 720ma led?
Do you have any idea what could be the best custom alternative circuit to LDD- 700H? my priorities are efficiency and heat.
thanks for all
Andrea
 

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bertus

Joined Apr 5, 2008
21,258
Hello,

Using the LDD 700, you will need a power supply of at least 40 Volts as your leds require 37 Volts and the voltage drop of the LDD 700 is minimum 3 Volts.
An 48 Volts power supply would work fine.
I would take a 4 ampere power supply, to have a little headroom, for 4 leddriver / led combinations.

Bertus
 

Thread Starter

andrea8723432

Joined Nov 6, 2020
9
thanks for answer.
I prefer design the constant current circuit. I want use LM317HVT/NOPB.
what is the best constant current circuit? there are a lot of circuit but I don't know what is the best option.
specs: vin=40v, corrent_max= 2.5A.
I want set 720 mA with the most efficient circuit. I will buy heat sink for led and lm317
 

bertus

Joined Apr 5, 2008
21,258
Hello,

The LM317 will likely not work as you need a larger voltage drop of about 4 volts (3 volt for the regulator and 1.25 volt for the resistor)
The LDD 700 will be more effeicient.

Bertus
 
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