drive circuit for 10 LEDs( not strip)

Thread Starter

Patrick19

Joined May 22, 2019
11
Please help me with design of drive circuit ( electric scheme) for these 10 Green SMD LEDs in order to avoid electric shock, short circuit damage, especially to assure a constant 20mA current to every LED, and forward voltage 3,2V :

with If - Forward Current: 20mA and Vf - Forward Voltage: 3,2V

If one LED is damaged , circuit would balance electric current or stop power supply for every LED.

data sheet :

https://ro.mouser.com/ProductDetail...eGfSY3csMkdgyOOAg6kv27McJjvoUqH/vTOfP8fK0Yw==
 

dl324

Joined Mar 30, 2015
16,846
If you want to insure a constant 20mA current, you'll need to use current sources. If your requirement is less demanding, you can use current limiting resistors instead.

What supply voltage were you planning to use and do you really need 20mA.

When operated at a conservative current, LEDs will last 10's of thousands of hours. When they start failing, they still emit some light.
 

Thread Starter

Patrick19

Joined May 22, 2019
11
I have found a
If you want to insure a constant 20mA current, you'll need to use current sources. If your requirement is less demanding, you can use current limiting resistors instead.

What supply voltage were you planning to use and do you really need 20mA.

When operated at a conservative current, LEDs will last 10's of thousands of hours. When they start failing, they still emit some light.
Dear sir,
I have found a
Constant Current Dimmable Miniature LED Drivers 3W 350ma & 700ma
link : https://www.downlightsdirect.co.uk/...-led-driver-constant-current.html#description

It has 3.6V and 700ma . can you make a sketch with these 10 LEDs and this driver ?
thank you.
 

Audioguru

Joined Dec 20, 2007
11,248
Your little LEDs are designed for 20mA. The LED driver will explode them with 700mA. Is that how you select things?
The output voltage of some of the 700mA LED drivers is 3.6V but there is no datasheet to show the minimum voltage.
The forward voltage of some of your little LEDs is 3.2V but the datasheet shows that some need 3.7V. Then they WILL NOT WORK with a current-limiting resistor for each LED.

You can use the 700mA LED driver to light 2V red LEDs, each with a current-limiting resistor, but then the expensive current regulating parts will be wasted.
 
Last edited:

Bernard

Joined Aug 7, 2008
5,784
Power source still unstated. AC adapter 12 V output is connected to boost converter constant current / constant V . V set to 35V, I set to 20 mA. LED series connected. If worried about single LED failure shunt each LED with a 5V zener diode.
 

BR-549

Joined Sep 22, 2013
4,928
I am not sure if I understand your post. If one LED fails, are you saying that you want the other LEDs to continue working?
 

Dodgydave

Joined Jun 22, 2012
11,285
Then you need a Series Led driver, your leds are rated at 3.2V each @ 20mA, if you put 10 in Series your psu needs to be rated at 35V or higher with the current limit needed.
 
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