Its supposed to be a switch mode regulator with voltage feedback from its output to ensure the voltage does not go higher than what it was designed for...

Yes,that is what it actually does,indeed.
They ensure the voltage doesn't go higher than what it design for,but,from your acquaintance with those kind LM2596S modules(that have the same components as in my photo:coil,chip,trimpot,4 capacitors,2 resistors,diode and led),does it valid also on the startup moments?or an inrush current will flow out of the module,at startup moments,forward to the connected device?
If yes,is there a need to connect in the output of the module a tvs diode or a varistor to prevent that?as i don't think that there is a place on the finished item to add the capacitor and the resistors,as LadySpark has suggested.

 

To be clear again, I am making a point about the regulator semiconductor again not the module. I have used many a switchmode regulator (the active component again, not the module), and none of them ever produced a spike at power up, if they had, I would have a bunch of 3.3V or 5V components that would be fried downstream.
The inrush will be on the input side of the module.
The integrity of the module I couldn't say anything about though. If you have a scope, you could try to capture the output.

 

To be clear again, I am making a point about the regulator semiconductor again not the module. I have used many a switchmode regulator (the active component again, not the module), and none of them ever produced a spike at power up, if they had, I would have a bunch of 3.3V or 5V components that would be fried downstream.
The inrush will be on the input side of the module.
The integrity of the module I couldn't say anything about though. If you have a scope, you could try to capture the output.

Okay,i understood your(and MisterBill2)clarifications and i take it into acount that you are not particularly referring to my module in the photo as you are not familiar with the source of it.
So if i got it right,in general,the inrush current will be in the input side,not on the outside,right?
This module has:

1. Built in temperature protection.
2. Built in current limit function.
3. Built in output short-circuit protection function.

Don't they protect from those rush current to go out the module to the device,even on start-up?
If something will fail,like an electrolytic capacitor,Aren't those built-in protections should protect the connected device?

 

If any shunt capacitor in the module fails, typically excess leakage or shorted circuit, the output would be reduced or zero. Not any spike.
Transients in a regulates supply are typically from the feedback response being slower than the control system response. That would not appear to be an issue with the module in consideration.

 

If any shunt capacitor in the module fails, typically excess leakage or shorted circuit, the output would be reduced or zero. Not any spike.
Transients in a regulates supply are typically from the feedback response being slower than the control system response. That would not appear to be an issue with the module in consideration.

So,i guess it is right to say that there is no need to use tvs diodes or varistors in those kind of modules,right?
For example,if i will connect the module input to a regulated standard wall wart(transformer)and a voltage surge will get into the wall wart(through the outlet),the surge won't forward to the 2596S module as the wall wart is regulated.But if the wall-wart is not regulated and the voltage surge will flow forward to the LM2596S module,Can the module deal with the surge(not a surge from lightning)?

 

So,i guess it is right to say that there is no need to use tvs diodes or varistors in those kind of modules,right?
For example,if i will connect the module input to a regulated standard wall wart(transformer)and a voltage surge will get into the wall wart(through the outlet),the surge won't forward to the 2596S module as the wall wart is regulated.But if the wall-wart is not regulated and the voltage surge will flow forward to the LM2596S module,Can the module deal with the surge(not a surge from lightning)?

In general, it won't work. It is necessary to install an input filter and a suppressor at the input. But even in this case, a short-term overvoltage at the output cannot be avoided.

 

In general, it won't work. It is necessary to install an input filter and a suppressor at the input. But even in this case, a short-term overvoltage at the output cannot be avoided.

The whole purpose of an actual REGULATOR is to suppress any variations of the input voltage so that they do not appear in the regulator output. Of course, there is undoubtedly an input voltage range specified for the particular regulator under consideration. Almost all voltage regulator devices and systems do have a limit as to the maximum input voltage they can handle.
And if a supplier will not, or can not, provide that information then do not deal with them because they are either incompetent or dishonest.

 

I asked 3 times from the seller to send me the datasheet with diagram circuit.
The first time,he just copy and paste the description of the item from the product page.
Second time,he copy a photo of the module from a random website that just marked how to connect the wires(output/input).
Third time,he just sent me a random diagram circuit that he found somewhere in the web,which is not even close to the module he sells.
Besides the fact that there was the LM2596 chip in the circuit,the connections and the values were differents,there were missing components or there were more components that are not exist in the actual module.
I guess,MisterBill2,that this is an example to a supplier that you were talking about.
Thank you all for your help.

 

I asked 3 times from the seller to send me the datasheet with diagram circuit.
The first time,he just copy and paste the description of the item from the product page.
Second time,he copy a photo of the module from a random website that just marked how to connect the wires(output/input).
Third time,he just sent me a random diagram circuit that he found somewhere in the web,which is not even close to the module he sells.
Besides the fact that there was the LM2596 chip in the circuit,the connections and the values were differents,there were missing components or there were more components that are not exist in the actual module.
I guess,MisterBill2,that this is an example to a supplier that you were talking about.
Thank you all for your help.

The diagram, if it uses te same IC device, , may actually provide enough information to understand the operation of the system. Maybe.

 

View attachment 317315

A round the web,there are a lot of diagrams with the same IC device.I found a diagram(see above)that is almost exactly the same as the module in my photo(same number of components,same value).I was expected from the seller,as you adviced before,to send me at least a real diagram of his module and not some randomly diagram that he picked from the web which doesn't even close to the module itself.It shows that the seller is not serious.
Btw,do all the IN-BUILT protections that this module has(over temperature protection function,current limit function and output short-circuit protection)are actually built in the IC itself and they will work at any designed diagram or you need to connect some component in a specific way to the IC in order that they work?
In other words,according to the circuit diagram above and assuming that the IC is really LM2596s
Are the 3 protection functions that i have mentioned
working at this circuit?

Why isn’t reading the datasheet for a microcircuit a leisure activity?

 

The whole purpose of an actual REGULATOR is to suppress any variations of the input voltage so that they do not appear in the regulator output. Of course, there is undoubtedly an input voltage range specified for the particular regulator under consideration. Almost all voltage regulator devices and systems do have a limit as to the maximum input voltage they can handle.
And if a supplier will not, or can not, provide that information then do not deal with them because they are either incompetent or dishonest.

In general, it won't work. It is necessary to install an input filter and a suppressor at the input. But even in this case, a short-term overvoltage at the output cannot be avoided.

Bordodynov's statement is accurate.

When designing, the buck regulator design specification should have included an acceptable percentage of output "overshoot" because it cannot be avoided. The output capacitor plays a critical role for control of overshoot.

 

The one possible cause for momentary output over-voltage could happen whan adjusting RV1, if there is a momentary opening of te wiper connection. Increasing the resistance increases the output, and so a momentary open could cause an over voltage pulse. But not really a spike.

 

I have noticed that you answer one to another,but not to my question,while i even attached a diagram circuit.

Why isn’t reading the datasheet for a microcircuit a leisure activity?

I read several of them,but my knowledge in electronic is not at the level that i can fully understand them.
The words:"In-Built protection"apparently mean that the protections are built inside the IC itself,but the datasheet doesn't say how it works.
So in refer to the previous diagram circuit,in that circuit,do the 3 protection work?

Bordodynov's statement is accurate.

When designing, the buck regulator design specification should have included an acceptable percentage of output "overshoot" because it cannot be avoided. The output capacitor plays a critical role for control of overshoot.

In the previous diagram circuit there is an 220uF/35V output electrolytic capacitor,which,as you mentioned,should control the overshoot.
So,if we assume that all the parts in my diagram circuit are original and well connected,is it okay to connect the module as it is(of course according to voltage limit)?or i should expect for a problem when i turn it on(start-up)or turn it off(shut the power for the module)?
Btw,the module is ready to use item,it isn't meant to be changed.

 

In the previous diagram circuit there is an 220uF/35V output electrolytic capacitor,which,as you mentioned,should control the overshoot.
So,if we assume that all the parts in my diagram circuit are original and well connected,is it okay to connect the module as it is(of course according to voltage limit)?or i should expect for a problem when i turn it on(start-up)or turn it off(shut the power for the module)?
Btw,the module is ready to use item,it isn't meant to be changed.

There are component manufacturing tolerances and variances involved.
If startup overshoot is that critical, you should check the output with a scope to be sure.

 

If none of the components have failed there should not be any startup spike in the output voltage. Adding another capacitor across the output will assure that the initial voltage rises under control.

 

If none of the components have failed there should not be any startup spike in the output voltage. Adding another capacitor across the output will assure that the initial voltage rises under control.

Do you mean another electrolytic capacitor with the same value(220uF/35V)?

 

Okay,since i didn't get any answer for the addition capacitor value,as misterbill2 suggested,i assume that it should be the same value as the output capacitor.
Thanks for all the replies.

 

OK, I was off-line for a while, I was not aware. A physically larger capacitor can better handle any surge power with less heating.
As for voltage rating, more than the output voltage. As for capacitance, that is not so very critical, although matching the value in the supply is reasonable.

 

OK, I was off-line for a while, I was not aware. A physically larger capacitor can better handle any surge power with less heating.
As for voltage rating, more than the output voltage. As for capacitance, that is not so very critical, although matching the value in the supply is reasonable.

We are talking about adding a second electrolytic capacitor in the output together with the one that is already there,Yes?(so we have 3 electrolytic capacitors in sum).
Or maybe you meant to replace(not add)the output capacitor with a physically larger one/higher voltage?
I assume that you meant to add another one,but just to verify that.

 

We are talking about adding a second electrolytic capacitor in the output together with the one that is already there,Yes?(so we have 3 electrolytic capacitors in sum).
Or maybe you meant to replace(not add)the output capacitor with a physically larger one/higher voltage?
I assume that you meant to add another one,but just to verify that.

I meant additional capacitors, not replacing any.