Asking for help with SMPS Transformer (with photos)

Thread Starter

Lumenosity

Joined Mar 1, 2017
622
Hello,
I have this Transformer from a SMPS.

It has 13 pins and I am not even sure which side is Primary and which side is secondary,
I'm wondering if you can help me identify the Primary and secondary sides and also
Why is it that Pins 1-7 are all connected? Is that normal for a SMPS transformer?

ANY insight you could give me on this transformer, how to understand the pins or what it is designed to do and how would help.

Bottom View
Transformer-1.jpg

Top View
Transformer-2.jpg

These 7 pins are all connected either intentionally or due to electrical problem.
Transformer-3.jpg

Pins 8-11 are connected together. Pins 12-13 are connected together.
Transformer-4.jpg

Here is the transformer on the board
Transformer-5.jpg

Here is the board with transformer removed. The object to the right is solder wick.
Transformer-6.jpg

Thank you.
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
622
Easiest would be to find the schematic and read it...
No schematic available.
The guy below tried to get information on the same transformer. His words verbatim......
Tried that route. That's why I posted here.
Maybe someone here is very knowledgeable about these transformers.

What "might" have to happen is a complete unwind / teardown and rebuild of it....just to get familiar with them.

Cannot get schematics anywhere .
 

Delta Prime

Joined Nov 15, 2019
1,149
Hello there! :) The transformer of yours looks like a Switch Mode Power Supply design topology for a embedded system or a DC-DC flyback converter because a flyback converter is a better option as compare to other topologies for low power design and for generating multiple output voltage levels.
An Embedded system requires different voltage levels for its proper functioning because the components used in any embedded system required different voltage levels as per their specifications. DC to DC converters come in to flavors, isolated and non-isolated grounds. For a "Hobbyist" they are made specifically for that particular circuit and cannot be used for anything else. They are proprietary.
 

Ramussons

Joined May 3, 2013
1,061
It has 13 pins and I am not even sure which side is Primary and which side is secondary,
I'm wondering if you can help me identify the Primary and secondary sides and also
Why is it that Pins 1-7 are all connected? Is that normal for a SMPS transformer?
First, the transformer pins Are Not Inter Connected. The photos very clearly show independent wires coming from the transformer to those pins.
Yes, the windings have very low resistance and there will be "continuity" between the pins. Those are SMPS transformers and they rarely fail.

It is not possible to define the "primary" and "secondary" (and a "feedback") winding without the schematic.

If the power unit is not working, look for blown fuses and / or switching transistors, to start with. But you will need to identify the controller IC before you can really begin troubleshooting.

From the photos of the PCB and the bottom view of the transformer, I would think that the Left Bottom 1,2 and 3,4 are the ends of a Bifilar winding of the Secondary and the Left Top pair is the feedback winding. The Right hand side are the primary windings and it maybe a Half Bridge switching setup.
 
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Thread Starter

Lumenosity

Joined Mar 1, 2017
622
First, the transformer pins Are Not Inter Connected. The photos very clearly show independent wires coming from the transformer to those pins.
Yes, the windings have very low resistance and there will be "continuity" between the pins. Those are SMPS transformers and they rarely fail.

It is not possible to define the "primary" and "secondary" (and a "feedback") winding without the schematic.

If the power unit is not working, look for blown fuses and / or switching transistors, to start with. But you will need to identify the controller IC before you can really begin troubleshooting.

From the photos of the PCB and the bottom view of the transformer, I would think that the Left Bottom 1,2 and 3,4 are the ends of a Bifilar winding of the Secondary and the Left Top pair is the feedback winding. The Right hand side are the primary windings and it maybe a Half Bridge switching setup.
Thank you. Very helpful information.
The cause of failure for this power supply was accidental reverse voltage connection to a 12v deep cycle marine battery so I was concerned that that could have damaged the transformer. I was not aware of the low resistance being able to make the winding appear connected so that is significant and helps a lot.

Since my multimeter cannot distinguish between these individual coils on the transformer, is it correct to assume that an LCR meter is the only way to check the transformer windings?

Thanks again for your advice and help.
 

MisterBill2

Joined Jan 23, 2018
9,292
Easiest would be to find the schematic and read it...
Part of the reason that the pins all seem to be connected is that solder bridge between pins 3 and 4. There may be other bridges as well. AND, quite often there are windings in series that do have a common pin connection.
The nature of switch supply transformers is that they are very application specific, and so I wonder why it was removed from that supply, if it has not failed.
 

Dodgydave

Joined Jun 22, 2012
10,050
No schematic available.
The guy below tried to get information on the same transformer. His words verbatim......
Tried that route. That's why I posted here.
Maybe someone here is very knowledgeable about these transformers.

What "might" have to happen is a complete unwind / teardown and rebuild of it....just to get familiar with them.
Pins 8 to 13 is the primary side, as this is a switch mode psu circuit being pulsed, and the transistors Q1 ,Q2 ..
 
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Thread Starter

Lumenosity

Joined Mar 1, 2017
622
Part of the reason that the pins all seem to be connected is that solder bridge between pins 3 and 4. There may be other bridges as well. AND, quite often there are windings in series that do have a common pin connection.
The nature of switch supply transformers is that they are very application specific, and so I wonder why it was removed from that supply, if it has not failed.
Good observation. I hadn't noticed that but upon closer inspection you are right.
Thanks.
The reason for removal was actually discussed here......
https://forum.allaboutcircuits.com/threads/help-30v-5a-3-outlet-transformer-bench-supply.174301/
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
622
One additional question I thought is this.....

If all the pins are connected via the solder bridge, how would one test the transformer using an LCR meter ?

Don't you need to know which leads go to which winding for an Inductance test ?
 

MisterBill2

Joined Jan 23, 2018
9,292
One additional question I thought is this.....

If all the pins are connected via the solder bridge, how would one test the transformer using an LCR meter ?

Don't you need to know which leads go to which winding for an Inductance test ?
If even one winding is short circuited by that solder bridge then the test results will be incorrect. And unless the transformer core is cracked or damaged, or the windings look burned, it is not likely that the transformer has failed. Transformers like that very seldom fail. Usually a switcher supply stops working because a semiconductor device has failed. So why was the transformer even suspected???
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
622
If even one winding is short circuited by that solder bridge then the test results will be incorrect. And unless the transformer core is cracked or damaged, or the windings look burned, it is not likely that the transformer has failed. Transformers like that very seldom fail. Usually a switcher supply stops working because a semiconductor device has failed. So why was the transformer even suspected???
1). Lack of knowledge of electronics and especially transformers (this is the journey to improve that)
2). Because the board "seems to be shorted" across the main power rails (to the novice)
3). I dropped it.
 

LesJones

Joined Jan 8, 2017
3,497
As you have not told us anything about the function of the board I am making the following assumptions. As I can see a common mode filter choke I assume the the input to the board is your local AC mains supply. As you say its was connected to a large battery with the polarity reversed I am assuming it was connected to the output. In post #15 you say it appears to be sorted across the "main power rails" what do you mean by this ? Do you mean the AC input terminals , the high voltage DC rail from the rectified mains or do you mean the output ? If you mean the output then you have probably destroyed the output rectifier diodes which have probably failed short circuit so you will be measuring the resistance of the transformer secondary which will have a VERY LOW resistance so you consider it to be a short circuit.

Les.
 
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