repurposing el-cheapo ebay smps modules as led drivers

[dannyf]

I did this a while ago and thought I would document it after a quick discussion with someone last week.

Those el-cheapo smps modules from eBay can be reconfigured as constant current led drivers, very easily. The output current can be programmed with a small resistor (minimum power dissipation on that resistor) for a given smps.

In my exercise, I showed how it could be done with a eBay LM2596 module - they sell for less than $2 delivered. All you need is a resistor + your led string. Three wires to the module and you have for yourself a high efficiency LED drivers, good for 3amp, likely lower for a knock-off, .

https://dannyelectronics.wordpress.com/2016/05/24/repurposing-smps-modules-as-led-drivers/

Here is my measurement of output current of 120ma, programmed with a 10ohm resistor. Output impedance at about 5K.

Other smps modules can be used as well.

[JacquesBBB]

This is nice, but why not simply using the CC versions of these same ebay modules whic will be more efficients ?

[dannyf]

It depends.

I'm not a fan of a typical switching mode cc LED driver, like pt4115: they work by pulsating current through the LED.

The approach proposed here is really a voltage driver in that a non pulsating DC voltage is applied to the LED so that AA constant current is maintained. That type of appraoches appeals to me.

Plus, it is always fun to do it yourself, especially using a device for something it isnt designed for.

[Seekonk]

Lifting pin 5 on the 2596 also makes a convenient on/off.

[dannyf]

Lifting pin 5 on the 2596 also makes a convenient on/off.

Good for low frequency pwm,

[Jasper]

Why keep the module's original voltage divider in circuit? Removing them seems like it would be simpler.

[ebclr]

Check this

http://www.aliexpress.com/item/3A-LM2596-LED-Driver-DC-DC-Step-down-Buck-Converter-Adjustable-CC-CV-Power-Supply-Module/32584936195.html?spm=2114.01010208.3.282.vUvAEc&ws_ab_test=searchweb201556_8,searchweb201602_4_10037_10017_507_10033_10032_401_10040,searchweb201603_3&btsid=678f4760-c8bc-4186-b90a-dc0d9e26731f

[dannyf]

I added the wiring and measurements for the MP1584 smps modules: https://dannyelectronics.wordpress.com/2016/05/24/repurposing-smps-modules-as-led-drivers/

A solid performer with a small footprint: the module is barely the size of a quarter.

Why keep the module's original voltage divider in circuit? Removing them seems like it would be simpler.

leaving in the divider makes no difference for the proposed application as a led driver, and it allows you to go back to use it as voltage regulator. The decision seems to be a simple one here.

[rob77]

what about no-load condition ? e.g. when one led in the string fails. - that will yield having the current sense resistor as the bottom resistor in the voltage divider in the feedback loop - and it will shoot the output voltage into the sky. probably even destroying the chip