Author Topic: LED Driver current setting of floodlight  (Read 592 times)

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Offline TantalumTopic starter

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LED Driver current setting of floodlight
« on: January 20, 2022, 03:37:58 pm »
Hello

I have bought some cheap Chinese 12-24VDC "20W" floodlights and I wanted to add a module that would allow me to dim the brightness. Fortunately, the LED driver has a dedicated pin for that feature, it will be easy to modify.

Now the problem.

I was verifying the original PCB of the floodlight, and there are something strange with the current settings.
It's a PT4115 LED driver, (NOT PT4115E), max 30VDC, 1.2A. The LEDs are 3.2V, 150mA max I thing.
Datasheet: https://www.led-stuebchen.de/download/PT4115E.pdf

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I was checking the sens resistors, and realized that they were out of specs. There are 2 resistors in //, 91 & 82mOhm which makes an equivalent 43mOhm resistor, which is not enough according to the datasheet (minimum 82mOhm = 1.2A max).
A 43mOhm resistor sets the current to 2.36A! Way too much for a 1.2A max led driver.

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When I analyze the led network, I can't figure out how much current is actually flowing through each LED.
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Can someone help me answering the following questions:

Q1: Is this default setting a problem (=reliability issue)?
Q2: How much current flow through each led?
Q3: Is the giant ground loop a problem (V+ on the left, ground on the other side?

Thank you



 
« Last Edit: January 20, 2022, 03:39:39 pm by Tantalum »
 

Offline tunk

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Re: LED Driver current setting of floodlight
« Reply #1 on: January 20, 2022, 04:01:24 pm »
Q2: Looks like there's two LEDs in series and 12 in parallell. Divide by 12 to get the average current.
 


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