Overheat of IRM-20-15 power module - Page 1
Forum section: electronics / beginners

author: VEGETA
author_rank: Super Contributor
timestamp: October 01, 2025, 06:06:48 am
content: Hello,I made a prototype of a power supply i am working on, with some differences compared to previous revisions. They both use the same power module IRM-20-15 and the exact same buck regulators but the new prototype power module heats a lot.the circuit works perfectly fine, all functions and rails are fine. Except that the excessive heat while using the same loads and so on...the circuit consists of:buck 1 - 5v. max 2 ampsbuck 2 - 3.3v or 5v (selectable). max 600 mA.buck 3 - 9v or 12v (selectable). max 300 mA.Aux buck - 3.3v. just for signaling and in future potentially esp32 powering... really nothing major. during tests it wasn't used at all.the design is 4 boards with 2 internal ones fully ground pour, there are a lot of ground vias to share heat as well and stitch plains.I posted the layout with many notes on it to help show if there is a problem.I measured voltages, all were very good. no drop voltage from the module at all, no short circuit...etc.version 1 had a different layout and shape, also without aux buck. produced no heat at full function but this one has excessive heat.in version 2 I also checked the inductors and caps temperature and they were cold... the heat source is the power module which also leaked much heat to nearby components and board area.kindly check and advise what to do about it.I am trying to figure out what went wrong, I thought the power module may be faulty so i desoldered it and replaced it with a known good one but still same issue. I do not think I did any bad mistake on layout side too....thanks in advance.

author: Nominal Animal
author_rank: Super Contributor
timestamp: October 01, 2025, 08:57:29 am
content: Quote from: VEGETA on October 01, 2025, 06:06:48 amDid you measure the power (or voltage and current) on both the input and the output of the power module?My own hobbyist designs tend to be small, making getting rid of excess heat difficult, so I prefer to use power modules with much higher maximum output than what I intend to use, simply because they tend to operate more efficiently and generate less heat. It is not universally true by any means, as it is a consequence of cost-optimized power modules, but something to consider. That is, I wouldexpectpower modules to run hot if run at their maximum capacity.

author: VEGETA
author_rank: Super Contributor
timestamp: October 01, 2025, 09:38:40 am
content: Quote from: Nominal Animal on October 01, 2025, 08:57:29 amI measured voltages but not currents.However, the exact same module on a previous version runs cold. the difference should not make any additional power consumption. Both were tried on the same load (sega saturn va0) with same input.the module must be this one due to very tight space available, and as i said it was working perfectly fine in previous version.this version I added an aux rail which wasn't used during the testing, dual mosfet (ideal diode + load switch) to all the rails with very small resistance and I saw that they were all cold. Also, a simple flip flop chip with some small transistors which all send signals... these weren't used in the testing.do you see anything majorly wrong with the layout? like, would it help if i route power to the buck3 and aux buck using top layer instead of going to bottom then up? maybe add other bigger thermal vias to cover more unpopulated area in the ground plain? or maybe increase the width of positive power trace and make it a bit thicker? but it is already good.I am really confused about this as it has worked fine on earlier prototype.if i wanna use the absolute maximum for all rails it won't exceed 15W which is a big margin to 20W rated value. it's total output efficiency is about 84% so for 15W it would be 2.4W wasted which is not much for that size. Some official test reports mentions very low temperature when full load similar to the one i got with version 1.so what is the case for version 2??the aux power supply is the same as 3.3v rail, it only powers a cd4013 d-flip flop chip which does nothing unless a signal is received. the buck 3 for 9 or 12v rail which should be just a signal to scart tv but i put 300 mA as a maximum... today i will measure on a system which does not require 9v/12v but rather only 5v rail.if you can figure out anything from my layout or so please tell me. I was just this close to go to market with this highly requested product... to only find the thermals like this.

author: VEGETA
author_rank: Super Contributor
timestamp: October 01, 2025, 09:44:31 am
content: measuring the power is kinda trick as i connect it to output device via a wiring harness with 6 wires, 2 ground and 4 for other rails. i would need to cut 5v trace and measure, then 3.3v and so on. for input power it is hard since it is via regular figure-8 cable and i do not have a clamp meter.if the input figure8 cable is not tightly connected, will this result in heat being generated like this? I feel the connector does not couple nicely with the cable but still do not see this as a reason.

author: Nominal Animal
author_rank: Super Contributor
timestamp: October 01, 2025, 01:12:48 pm
content: Quote from: VEGETA on October 01, 2025, 09:38:40 amNo, but it's outside my know-how anyway.What I suspect is a tin whisker or PCB stackup problem, with the power module seeing much higher load (because the problem acts like an extra low-value resistor on the output), very close to the power module. Possibly a via almost connecting the outputs, or a solder ball underneath the module, or some such. Or maybe some non-heated flux (so it stayed conductive!) trapped on the PCB surface, acting like a low-value resistor.Comparing the input and output power would tell if that is the case. Comparing the input to output power, even if using a rough wall wart household power meter, would tell. At 15V 1.1A output (when all your outputs are at the higher option and loaded to your stated maximum loads), the output should be 16.5W, and the output about 16.5W / 84% ≃ 19.6W (based on its typical efficiency stated in thedatasheet), so the module should dissipate about 3.1W. The datasheet derating curve shows that the module should be able to do this in ambient temperatures of up to 60°C. Dissipating 3.1W will heat it up for sure, but the datasheet does not tell how good the potted surface is in transferring the heat to ambient air.(If you compare the IRM-20-15 toIRM-30-15, you'll see that at 16.5W output (80% for IRM-20-15, 55% for IRM-30-15) the maximum ambient temperature is 60°C for IRM-20-15, and about 70°C for IRM-30-15, indicating the latter should run several degrees Celsius cooler at the same load, perhaps up to 10°C cooler. However, if you didn't see excess heat at the same output load in the first PCB, this is not the issue, andsomething— most likely something conductive between the power module output and ground — on this new PCB causes the excess heat.)Another option would be to desolder the power module, and measure the load on the PCB when using a lab power supply instead of the IRM-20-15 module (with voltage set to 15 V and current limit to about 1.5A). If my suspicion about an unwanted conduction path on the PCB is right, you should see the power supply hit the current limit immediately.

author: VEGETA
author_rank: Super Contributor
timestamp: October 01, 2025, 06:51:48 pm
content: well after some testing it turns out that the module does heat to that degree even on version 1... maybe v2 is slightly hotter but overall similar.IRM-30 is good but definitely not gonna fit unless i do double sided placement of components. it would increase the cost of it for sure.don't know what to do now

author: VEGETA
author_rank: Super Contributor
timestamp: October 01, 2025, 10:01:39 pm
content: I inserted IRM-30-15 in the board to compare it to 20 version in terms of price. This thing MUST get all components to the bottom layer. Green is the IRM-30 and black is IRM-20.However, I am worried if it would cause more issues like more ripple and noise since I would need to route input power back then route the output power forward towards the output connector.

author: Nominal Animal
author_rank: Super Contributor
timestamp: October 02, 2025, 06:39:17 am
content: Does the IRM-20-15 need to sit on the PCB, or could you use an interposer PCB and double-tall pin headers or simply thick multi-strand wires to put it further away, keeping the waste heat off your PCB?Or is it more that you cannot get rid of the extra heat from the IRM-20-15 in your enclosure?You could consider epoxying the IRM-20-15/IRM-30-15 directly to the enclosure for maximum heat dissipation, and just use thick multi-strand wires (and heatshrink covering the solder joint) to connect it to your current PCB.Just going off the datasheet typical efficiencies (84% for IRM-20-15, 88% for IRM-30-15, the latter should have quarter less waste heat output at the same load, likely even more due to the much higher rated maximum power. Why quarter? Because 100%-84% = 16%, 100%-88% = 12%, and <12% of X> is 25% less than <16% of X>. And that is just based on the typical efficiency. The added effect of maximum load being only 55% of the rated load of IRM-30-15, rather than 78.5% of the rated load on IRM-20-15, and the larger surface area of the bigger body/encapsulation epoxy and thus better thermal conduction to ambient air, should mean the difference is even greater in actual temperature rise.I suggest you do one IRM-30-15 and one IRM-20-15, both with soldered wires to the current PCB, and simply compare their surface temperatures at the same load. Since they have the same epoxy encapsulation material, you can use an infrared thermometer, and compare their temperature rises. For example, if IRM-20-15 heats from 20°C to 60°C, I would expect the IRM-30-15 to heat from 20°C to less than 50°C, or at least 25% lower temperature rise because of the reasoning above. (Do note that these are very rough figures, because we do not have the actual power-to-temperature rise curves of either module, and I'm just very crudely approximating the differences based on the little information we have.)(If you have a programmable load, then connecting only the IRM-20-15 or IRM-30-15 to it, powered from mains AC, and measuring the steady-state surface temperature increase from ambient at a few different loads, letting the module temperature stabilize at each load, all without extra airflow from e.g. surrounding fans, would yield a VERY USEFUL load-to-temperature rise curves, that I seriously wish MeanWell would publish themselves. It's the kind of information that makes designers' work much easier. And you wouldn't have to rely on purely theoretical guesstimates like mine, or buy all possible modules and test them in practice!)Personally — and remember I am only a hobbyist who does non-commercial one-offs, soIdo not need to minimize cost at all! — I would prefer anMPM-30-15or anRPS-30-15, because of the minimal leakage (2×MOPP). Although the leakage on IRM-20/IRM-30 is low, having almost none of it makes my designs work better and reduce the likelihood of ground loops.

author: VEGETA
author_rank: Super Contributor
timestamp: October 02, 2025, 07:47:17 am
content: Quoteit must be soldered directly, and heat cannot be taken out since there is no heatsink or so. it sits in a game console.QuoteI have used MPM-30-12 in a previous product which sells till today. However, it is a lot more expensive and I will use IRM-30 in the next iteration.However for this product, looks like I can go with IRM-30 as my only option. It is weird why 20W module wasn't enough for this application, or that the 20W module from Meanwell heats more than it should.In the previous product, MPM-30 (and you can assume IRM-30) runs nicely. It does not heat but rather a bit warm, totally acceptable and actually you can assume it is cold. That product is powering a more powerful console (22W rated vs ~10W rated) so I can expect IRM-30 to run even colder.the challenge is to fit the components on BOTH sides which is something I never did before. it will increase the price as well.Routing power input and output is kinda tricky and not straightforward but doable.