Transformer identification

[clockbiscuit]

Hello EEVblog forums. This is my first post.

I am not super familiar with the nomenclature used to describe transformers. I have come across a small transformer and was wondering how I can identify just what I am looking at. You can see the part in the image attached, it is approximately 40mm across and has "ES-P4910-1" and "RIC 0639" printed on the top. There are 8 electrical terminals on the part, my suspicions are that there is two secondary windings on the part used for generating 5v and 3.3v power rails within the device it was from.

Any clues? 

[mariush]

That's a transformer designed for switching power supplies. It's meant to run at 30-100 kHz, not 50-60 Hz as regular (classic) transformers works so without a proper controller, that transformer is useless to you.

The pinout.. it's unlikely to be what you think it is. But it depends on the device you pulled that from, what those pins are about.

[Kremmen]

Yes, clues.
Like mariush already noted, that is a transformer for a switchmode PSU. Or it could conceivably be a pulse transformer to drive a big half-bridge but most likely not.
There are a great variety of different switchmode PSU topologies and this of course belongs to one of the transformer isolated kind. Typcal of those are the flyback converter and forward converter. Both have a primary winding and one or more secondary windings. Additionally, the single transistor forward converter typically has an extra winding on the primary side to handle transformer core flux reset. Both kinds may also provide an extra winding to supply the controller chip that drives the main switches of the PSU.
A big difference between the 2 is that the flyback transformer is not really a transformer - it is more like 2 coupled inductors. The difference may appear trivial to the uninitiated, but in fact it is crucial. Unlike a real transformer, during the main switch 'on' time the flyback "transformer" stores energy in the magnetic flux of the core and releases it during the switch 'off' time to the secondary circuit. This requirement is reflected in the fact that a flyback core usually has an air gap for storage of the flux energy whereas the true transformer of the forward converter does not. This difference is not visible from outside so you have no way of visually telling what you have in your hands.
The only sure way to find out is to measure the coil inductances and the stray inductance using an LCR meter. That will give you an idea of the winding arrangement and the nature of the component. Even then it is highly risky to use it for anything like an off-line application unless you definitely know what is the original primary winding and that it was meant for that application. Otherwise the isolation and creepage distances inside may not be up to the task.

All in all, these salvaged SMPS transformers are problematic because you usually cannot tell where they came from (unless you salvage them yourself and recognize the circuit) and they also cannot be disassembled for rewinding, due to the fact that the core is usually glued together and breaks  when opened by force. So just toss it and look for something more usable.

[clockbiscuit]

This is all very interesting. The part is from a Koyo PLC that had its 5v rail shorted out. I didnt realise that this was even a switch mode supply - I pulled it out because I couldn't measure anything across the secondary side. but I was probably barking up the wrong tree there because of all this high fq stuff...

How would someone decode the part numbers used on these things anyway? I thought it was pretty odd that google didnt seem to provide any useful results. Perhaps I didn't look hard enough.

[Terabyte2007]

To me, one of the big mysteries of life. Finding documentation on transformers is much like finding Jimmy Hoffa! I have around 40-50 transformers ranging from small switch-mode to large linear supply versions, and I usually do three things.

A) Use an LCR meter to determine the characteristics such as Pri/Sec, taps, impedance. I then label them and test them with a circuit I built for doing so.

B) If I salvage from an old supply or board, identify the I/O's and driving circuits to help in labeling the transformer for future use.

C) Last resort, try Google with every variation of part number printed on the transformer and cross your fingers!

Generally, you can just look at a transformer and place it into two classifications which can help you narrow it down. Linear PS's and Switch Mode PS's. There are some variations but these can help you narrow it down.

[Kremmen]

Thats the reason i said to toss them. They are of course potentially quality components but as a rule it is next to impossible to find any useful data. Most are bespoke components made by a mfg for the particular application and the type code is customer specific, not to be found anywhere we can reach.

[Terabyte2007]

Thats the reason i said to toss them. They are of course potentially quality components but as a rule it is next to impossible to find any useful data. Most are bespoke components made by a mfg for the particular application and the type code is customer specific, not to be found anywhere we can reach.

I can not disagree with you. But, speaking for myself, I can not throw most away as some are pretty expensive to buy, and they are very usable if you have the proper info on them.

[Kremmen]

Sure if you have the time, energy and skill to find the info or provide it by measurement. But it is a long road and success is not guaranteed.

[peter.mitchell]

I usually just keep them to wind inductors on to.

[uoficowboy]

That's a transformer designed for switching power supplies. It's meant to run at 30-100 kHz, not 50-60 Hz as regular (classic) transformers works so without a proper controller, that transformer is useless to you.

The pinout.. it's unlikely to be what you think it is. But it depends on the device you pulled that from, what those pins are about.

How are you able to identify it as a switch mode transformer?

[mariush]

How are you able to identify it as a switch mode transformer?

Due to size, ratio between wire and ferrite/iron/metal core material and having worked with a ton of switching power supplies. You could shorten it to "experience".



 

[clockbiscuit]

Heres some context - this is the circuit I pulled the transformer off.

240v is fed in from the top and theres a couple of power rails that come out on the right. I know the 5v rail had been shorted out and I am guessing theres probably a 3.3v rail too. I did try changing out the regulator because i figured it was an easy target - this didn't work so i traced things back and found this transformer wasn't giving me anything sensible (fairly sure i mis-diagnosed that by the sounds of this thread though)

Anyway, does this look like a typical switch-mode supply to you guys?, I would expect to see some kind of controlling chip if that was the case...

Clearly there's an optically isolated side to the circuit (the bottom), and the 240v has a diode bridge rectification up the top. This transformer might have been being used for some dc-dc voltage conversion for my supply rails. What do you guys think?

[fluxcapacitor]

This is all very interesting. The part is from a Koyo PLC that had its 5v rail shorted out. I didnt realise that this was even a switch mode supply - I pulled it out because I couldn't measure anything across the secondary side. but I was probably barking up the wrong tree there because of all this high fq stuff...

How would someone decode the part numbers used on these things anyway? I thought it was pretty odd that google didnt seem to provide any useful results. Perhaps I didn't look hard enough.

koyo plc . Whats the model number

[mariush]

Yes, it's a switching power supply.

In very simplified way (and with probably some mistakes but you get the idea)

F1 is fuse, RTH1 is a thermistor used to limit inrush current, The coil thing above the bridge rectifier is a common mode inductor (for ac filtering) , the gray rectangle on the right is an X capacitor (again for AC filtering), the blue things on the right are Y capacitors.
AC voltage comes through those, goes in the bridge rectifier BR1 , then gets smoothed out by the two big capacitors and you have 110-120v / 220-240v  x 1.41 V DC

The to-220 transistor (or mosfet maybe) with heatsink turns on and off sending pulses through the transformer, resulting in some output on the secondary side as magnetic field in the transformer forms. The D3 On the other side are two diodes on a package like this:  -[###||-><-||###]- which convert the AC back to DC voltage which then goes through C12, C13, the inductor with 100 on it, the other capacitors etc.

There's either some circuit or there's a smaller winding on the secondary side which helps something on the secondary side send a signal through the optocoupler back to the primary side to a transistor, basically telling it  how often and for how long of a period the large transistor should stays on. When the voltage is too big on the secondary side, the primary side receives through the optocoupler a signal to chill, to slow down.
If there's more current pulled, the primary side gets message to send pulses more often though the transformer to keep the voltage in check.

I'm not exactly sure what IC4 is for, it may be just a basic linear regulator generating some lower voltage from the output.

It's a bit more complex than this as there's two optocouplers and some transistors and that IC5 I can't figure out from a simple picture, but the fact is ... this is a switching power supply.

If you want to learn more, see for example this link  (page 107 and forward,  2.1.1 An Introduction to Switched Mode Power Supply
Topologies) : http://www.nxp.com/documents/application_note/APPCHP2.pdf

These two application notes also contain a lot of information about switching power supply topologies:

Microchip AN1114 Switch Mode Power Supply (SMPS) Topologies (Part I) : http://ww1.microchip.com/downloads/en/AppNotes/01114A.pdf
Microchip AN1207 Switch Mode Power Supply (SMPS) Topologies (Part II) : http://ww1.microchip.com/downloads/en/appnotes/01207b.pdf

[Kremmen]

I concur with mariush's analysis and add one comment: the electrolytic caps on the board are Matsushita/Panasonic and Nichicon - both quality brands so this PSU is not you average cheapo garage model.
The secondary side ICs may very well be simple linear regulators. That would make perfect sense especially if the main switcher is a flyback design with not the greatest cross-regulation between secondaries. Especially as there are no secondary side coupled inductors in sight. In such a case one secondary is fed back to close the control loop to the primary switcher but that leaves the other secondaries sensitive to load variations. So you increase their voltage a bit in the transformer and stabilize it using a linear chip.
The second opto is a mystery. Usually you only have the one transmitting the signal to break the 'on' period of the main switch but here you have two. Could it be some kind of tricky double regulation to keep 2 secondaries from overvolting at the same time in parallel? Who knows.

But is is definitely a switchmode PSU; either flyback or forward topology

(P.S. 2 of the caps look like they could be Nippon Chemi-Con, another OK brand.)

P.P.S. The primary side "transistor/MOSFET" looks suspiciously big - far larger than a regular TO-220. How many legs does it have and where do they go exactly? That could be your controller and main switch rolled into one.

[clockbiscuit]

Jesus you guys know your stuff. I will be taking a thorough look through this.

Mariush; you're quite right IC4 is a basic linear regulator and D3 is setup just as you described (it has a nice picture of the diode configuration printed on the front).

I am sort of surprised that the components are of any special quality - koyo is known as a cheap and nasty brand of PLC. Fact is the thing broke because they did not fuse or limit the draw on the 5v rail exposed within the RJ16 connector used for RS232 comms with the thing. I am proud to say at least I didn't break this one myself 

The device is a Koyo DL06, I have no idea if a service manual would be available for something like this - I found searching google for PLC and schematic brought up a gorillian results for industrial control systems...

[fluxcapacitor]

i found this document, not sure if itll be of any use.

http://www.automationdirect.com/static/manuals/d006userm/ch2.pdf