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# Description of the step down converter based on LM2596S DC-DC step down 3.2-35V

grala1 6942 12
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• Hello.
Below I present a description of the step-down converter based on the LM2596S-ADJ chip.

The prices of the converter start on Aliexpress from less than \$ 0.60 with shipping, prices with shipping on Polish auction portals start from about PLN 7.
The maximum input voltage for the converter is 35 V (the converter IC itself can withstand a higher voltage, but the limitation here is the electrolytic capacitor at the input, which here has 35 V - you can find converters with a 50 V capacitor).
The output voltage is regulated by a potentiometer in the range from 3.2 to 35 V, efficiency up to approx. 3 A.
Converter dimensions: 44 x 20 x 13 mm
The converter was tested with an artificial load for input voltages of 12, 15 and 24 V and for output voltages of 12 and 5 V. During the tests, voltages and currents on the input and output sides of the converter were measured, power and efficiency were calculated.
Below I present the measurement results.
Input voltage 12V, output voltage 5V:

Input voltage 24V, output voltage 5V:

Input voltage 15V, output voltage 12V:

Input voltage 24V, output voltage 12V:

The diagram below shows the efficiency of the converter depending on the current consumed from the converter. We have shown the efficiency for 4 different variants.

As you can see from the diagram, the efficiency of the converter is not a constant value and it can be seen here that the highest efficiency of this converter is at 15 V input voltage and 12 V output voltage, and the lowest at 24 V input voltage and 5 V output voltage.
It can also be seen that the efficiency also varies with the load on the inverter.
As you can see, the efficiency of this converter does not exceed 85%, where many sellers give even greater value in their descriptions.
The graph shows that for the input voltage of 24 V and output voltage of 12 V at approx. 2 A, the efficiency is approx. 88% - I did not notice it during the measurements, but I would consider this value as an error when reading the value from the artificial load display or an error when entering the value to Excel - it only came out when creating the chart.
It can also be seen from the measurements that it is not always possible to load the converter with 3 A and expect that it will hold the voltage at the output.
I also tested the converter temperature for the configuration where the efficiency was the worst - 24 V / 5 V. With a consumption of 2.5 A in this configuration, the converter temperature after 30 minutes was approx. 48 ° C.
Below is a link to the description of a converter based on the same circuit, but with built-in voltage measurement on the input and output sides.
https://www.elektroda.pl/rtvforum/viewtopic.php?p=16964656#16964656

Can you write similar article? Send message to me and you will get SD card 64GB.
grala1
VAG group specialist
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grala1 wrote 9499 posts with rating 3981, helped 1363 times. Live in city Kalisz. Been with us since 2006 year.
• ditomek
Level 21
Good job.
The parameters will definitely be useful because the device is really popular.
And as with the quality of the components and the ability of the inverter to work continuously.
I would like to use it in several power supplies (12-> 5) and I am wondering about the service life.
• Pelos
Level 11
The question is, is it the original LM National ...
• macgyver96
Level 17
Good job.
The only thing missing is the oscillograms under various loads, unfortunately I experienced that this converter is terribly messy at the output and with sensitive systems you need to take care of good filtration.
• lukiiiii
Level 28
Do not reverse connect the wires (plus and minus) because the LM2596S explodes.
• User removed account
Level 1
• zygmuntf
Level 11
@lukiiiii: What voltage is at the output of the damaged converter with the LM2596 chip?

Has anyone "managed" to burn this chip so that Uout ? Uin; if so, under what circumstances? The post by @ grala1 on the XL4005 shows that the damaged module is at least not dangerous for the powered device ...
• lukaszd82
Level 30
I have built 3 power supplies on the LM2596-5 and they run for 2 years 24/7 without any problems. The systems consume about 1.5A and the power supply is 12V.
In addition, the systems (along with the rest of the components for the construction of the converter) are recycled. I desoldered the whole from the damaged light-ethernet converters. In the above-mentioned devices, they worked 24/7 for 10 years (maybe with 2 breaks for about 2 weeks). Generally, it is very difficult to damage this system ... unless we connect the power supply the other way round;>
In addition, I made a friend to a GPS power supply in exchange for a damaged one. He drove it in the car until the GPS collapsed. So the makeshift power supply survived the powered device (battery died and cold February appeared ...)
• CMS
zygmuntf wrote:
What voltage is at the output of the damaged LM2596 converter?

All wise books "tell" what happens when the circuit works properly and as intended. There is no one that says something about how a broken system behaves, because it cannot be defined.

Answering the second question, yes, a situation may arise when the damaged system gives full input voltage at the output. And if the power source has a significant current, then after such damage, in addition to full voltage, we can also get "a lot of Amps". I managed to evaporate about 5mm of a path 0.03mm thick and 2mm wide. Count yourself what current flowed at 40V.
• zygmuntf
Level 11
Agree that this cannot be read in books. Sometimes, however, a practitioner who has burned several (teen) systems, or even a manufacturer's representative can tell a lot. Once, in the second of these ways, I found interesting information on the protection of a certain DC-DC converter for powering LEDs in critical situations, such as a choke short circuit or a Schottky diode breakdown (this is a bit beyond the topic of the thread).

The calculations gave me 2.8 kA, but I made them for room temperature and did not take into account the internal resistance of your power supply
• CMS
zygmuntf wrote:
The calculations gave me 2.8 kA

So you can see how much electricity can flow temporarily.

zygmuntf wrote:
Sometimes, however, a practitioner who has burned down several (teen) systems,

That's why I mentioned the example above. Though I've only burned three so far.
• lukiiiii
Level 28
zygmuntf wrote:
@lukiiiii: What voltage is at the output of the damaged converter with the LM2596 chip?

I didn't measure it because I was a bit shocked. probably 0 or Uin.
• jakobs84
Level 12
Hello

How to achieve these 2.8kA? :P

28V and 2.5A Vin after a while Vin = Vout and pufff after the circuit, is it "a lot of Amps"? Is no load ??

best regards