Chip identification

[Mjolinor]

I have a 8 pin surface mount chip that I suspect is a dual opamp/comparator.

It is in a Chinese ultrasonic cleaner and the numbers have been removed (groan).

It drives  a pair of MOSFETS that are connected, in totem, across rectified mains to make the 40kHz for the transducers.

What I can decipher of the number from looking at several different boards is: IR2XXXS

I cannot identify the XXX, the other alphanumeric digits are correct.

It is connected thus:
1
2
3 ground
4 470 ohm >>> MOSFET 2 gate
5 100 ohm >>> 15 volts
6
7 470 ohm >>> MOSFET 1 gate
8

It seems logical that 1+2 are + and - for one output and 6+8 are + and - for the other output.

Does it ring a bell with anyone?

If it is an amp then it sure has odd pin configurations.

[TurboTom]

There's a huge variety of half bridge gate drivers available by Infineon's Internation Rectifier branch. It may be difficult to chose the right one, as an example the IR2102S. There are different drive current and protection function options, as well as inverting and non-inverting ones or some with an input/inhibit logic. I'm afraid you've got to dig a little deeper into the schematic to find out what it actually is. Or, if something's left of the driver chip, decapsulate the die and check on the microscope if there's an identifier on the metallisation.

It's definitely no OPAMP, though 

[chekhov]

It looks like a gate driver, there are plenty of them (look into selection table):
https://www.infineon.com/cms/en/product/power/gate-driver-ics/?filterValues=~(search~%27IR2~packageName~(~%27SOIC*208N))&visibleColumnIds=name,opn,orderOnline,productStatusInfo,496_nom,290_114_nom,290_113_nom,350_nom,358,551,852,347,851,608,packageName,640_nom,157_nom,853_min,853_max,853_nom,854_min,854_max,856_nom,855_nom,859_149_nom,860_150_nom

And it seems that your pinout does not match common pinout in manuals, or just please don't miss other power rails/verify again where pin 1.

[Mjolinor]

Thank you both. I will be able to at least get the pinouts and general working even if I can't get specific.

I think the electronic world is leaving me behind.

I do not think the chip is blown but I am just struggling with the feedback mechanism. The BJT version of the board has a small ferrite transformer feeding to the gates but the MOSFET version does not have that feedback so I aint yet figured how the thing adjusts the oscillation for optimum frequency.

[Mjolinor]

It looks like a gate driver, there are plenty of them (look into selection table):

And it seems that your pinout does not match common pinout in manuals, or just please don't miss other power rails/verify again where pin 1.

Pin1 goes off board to the control board and is marked PWM on the cable socket.

I didn't bother tracing the other pins. It was pretty much a waste of time until I found what the chip was, if it had been a power opamp of some sort then I would have got lost in the feedback trying to work out plus and minus hence the plea for help.

Work in progress.

[fzabkar]

This pinout looks plausible (except maybe CS):

https://www.infineon.com/dgdl/Infineon-AUIR2085S-DS-vNA-EN.pdf?fileId=5546d462533600a4015355a82609133f

This document matches drivers with suitable switches, so maybe the MOSFETs will give you a clue:

https://www.infineon.com/dgdl/Infineon-EiceDRIVER_Gate_Driver_ICs-ProductSelectionGuide-v01_01-EN.pdf?fileId=5546d46250cc1fdf015110069cb90f49

[Mjolinor]

No match yet. Here are a couple of pics of two different boards. I do have another ten or so but they are not dismantled. I will do that if I need to.

It looks to me like the digit after 2 is probably a 9 then a 4 perhaps.

Why do they do this.

[TurboTom]

Can you post detail photos of the PCB top and bottom? If you ask me, the still visible part of the chip inscription could well indicate it's an IR2101S. If the connection matches is a different question and could indicate that the assumption is wrong, but in order to get assistance from the forum, these photos would definitely be a big help.

[Mjolinor]

I will draw the schematic when I get round to it. The circuit is very similar to the BJT version and they suffer from the same fault, blowing up. A fix attempted by the Chinese by removing two of the diodes in the bridge may well, in theory make the average power the same as 110 but the peak is what kills them.

Sorting this feedback path is something I would just like to know to get the schematic but probably isn't necessary as the same fix that works on the BJT will probably work on the FET version.

I can't seem to get a good picture but here is what I could get.

I can sort it now, the pointer about gate drivers was all I needed. It wasn't even on my radar, old decrepit etc etc.

http://rollingpast.com/john/ultrasonic/

[m k]

the still visible part of the chip inscription could well indicate it's an IR2101S.

Round top in the middle seems to be missing.
Is IR2111S  very different?

[Mjolinor]

Quick check and IR2085S seems correct on all pins apart from current sense. It is marked PWM on the silk screen but remember this is Chinese so may not be what one expects it to be.

I also note that the "floating" supply is not actually floating, it has a common earth/ground/negative and is 15 volts.

[fzabkar]

If you disconnect the gates from the MOSFETs, does the gate driver self oscillate? If so, at what frequency? Does this frequency match the choice of RC at the OSC pin?

What are the part numbers of the MOSFETs? We may be able to work backwards and locate their recommended gate drivers.

What are the supply voltages? Which pins?

[Mjolinor]

I am pretty sure it will not oscillate if I do that. There will be a feedback mechanism from the LC on the outputs somewhere.

The MOSFETS are 24N50 and they blow for fun when switching mains.

This is the BJT version of the same thing.

http://rollingpast.com/john/ultrasonic/Screenshot%20-%20130715%20-%2010:52:26.png

It remains the same in the MOSFET version for all of the power parts of the circuit apart from the feedback circuit, transistors and components values. As far as I have worked out there is no feedback but they will not work without it. You can see that the BJT versions self tunes and if you crunch the numbers it comes out about 43 kHz. The MOSFET version will be the same.

This is a close up of the gate control circuit including the PWM pin that goes off board to the control circuit.

http://rollingpast.com/john/ultrasonic/my_photo-10.jpg

I don't really need to know now what the specific chip is, it is not duff and works fine. I just need to reduce the power the thing draws so that it stops self destructing. Easy enough.

The OSC pin is fed from the pin on the right marked IR21 through a 10k resistor. Another meaningful Chinese set of digits.

[TurboTom]

It's got to be an IR2184S, in this case "PWM" would supply the switching frequency and "IR21"(?) would control the shutdown function via Q2. Moreover, this half-bridge driver provides ample amounts of output current, so it's possible to switch substantial mosfets fast enough for the present job. And with a 600V high-side margin, it's suitable for direct mains applications...

This still doesn't explain why your mosfets are failing. Does the failure cause collateral damage (i.e. blowing resistors, damaging the driver) or does it just blow the mains fuse and with the replacement of the damaged transistor(s), everything's working again for the time being?

In that case, I could well imagine that the problem is located completely elsewhere, for example a wonky contact at the ultrasound transducers. Since the output circuit appears to be some kind of resonant LC arrangement, if the power won't be consumed in the transducers, it will be reflected and may easily damage the mosfets. Same thing may happen if there's an internal connection problem in one of the power capacitors. I guess you've got to check a lot of components with accurate equipment (decent LCR bridge) if something appears slightly "off"... Some faults will be virtually impossible to identify with low-level meters, like arc-overs in inductors.

Seems like a decent piece of work...   

[Mjolinor]

The problem (I think) is the inductor values. I am not as familiar with the MOSFET version as I am with the BJT version. I spent months sorting out the BJT one a good few years ago and can now make them work reliably provided normal rules are followed like don't run them without water and don't run them too long. The current version of the BJT one is now sold with the modifications that I worked out some number of years ago.

Both circuits are designed for 110 volt operation and the only thing they do to sell them in the UK and Europe is to remove one diode from the main bridge so that it only runs half of the time. This is not a fix it is a "maybe it will work long enough for people to forget where they bought it"

In order to make them work properly you have to change the inductor values.

I agree with your choice of device I think. I will look at it later today.

I am beginning to wonder about the feedback not being there, it seems a tad strange to me.

This part of the circuit is driven from a transformer that is nothing to do with the main power parts. This transformer has two outputs, 15 V and 5 V. The 15 Vac is rectified and fed to a 7815, the output from that is taken through a 7805 . All fairly straightforward. Now the 5 Vac winding has one side connected to the common ground and is then fed, as AC to the control board where there are two 16 pin SM DILs with their numbers removed. This is what provides the PWM signal.

It is looking maybe something like the AC cross over provides a start and the board free runs for half a mains cycle (10ms) then waits for the next mains cross over. Not understanding it really yet but I don't really need to, I reckon if I sort he inductances then it will work reliably.

[Mjolinor]

Brain fart. I let the smoke out.

I thought I would power up the control side of the thing and not the power side in order to see what it does. Fed mains up the 15 volt output of the transformer instead of the mains input. The LEDs all flashed rather brightly in the brief instant before the circuit breaker blew in the cellar. Good job I had to go down there really, if I had stayed in the loft the cloud of smoke would have choked me.

I have to pull another one apart now, this one is toast.

[fzabkar]

I would think that the 110V version would have a wire running between neutral and the junction of the two 1uF filter capacitors. This is the typical voltage doubler configuration used in dual mains voltage designs. IMO it doesn't make sense for a rectifier diode to be removed.

[Mjolinor]

I can absolutely guarantee that it is not like that. The whole thing is a 110 volt design and they remove the diode so that it work (briefly) on 230 volts.

That is why they have such a bad reputation. The markings on the ferrite transformer and inductor confirm that. They are marked 110/220 so the side connected to the centre of the capacitors and the centre of the transistors is a 110 volt winding.

Here is a pic of a completely unmodified board. Note the diode missing, bottom right.

http://rollingpast.com/john/ultrasonic/unmodified.jpg

[Mjolinor]

Well. Shocked.

The oscillator does free run at about 43 kHz. More interestingly when you turn on the ultrasonic it is modulated so runs from about 40 kHz to just under 44 kHz with about a 200 us period (5 kHz frequency)

[Mjolinor]

More looking, measuring, contemplating and hypothesising later:

There is no feedback to self tune the oscillation for resonance as there is in the BJT version.

I reckon that the manufacturers of these things tune (small preset on control board sealed with hot glue) each cleaner at manufacture for approximate resonance on the transducer capacitance / transformer inductance / mechanical resonance.

They modulate that centre frequency (now measured at 38 to 46 kHz) so that tolerances during manufacture can be looser and you can more safely use these cleaners for electronic boards where you always run the risk of resonating bond wires if you use a fixed frequency cleaner.

Clever stuff.

It also seems to me that this setup will make a really good induction heater with some beefy capacitors and small heating coil/inductor.