EEVblog 1518 - Hoymiles Solar Microinverter TEARDOWN

Depotting, teardown, and some reverse engineering schematic analysis of the 400W Hoymiles solar microinverter.

00:00 - Hoymiles 400W Micro Inverter
01:05 - Removing the silicone thermal potting compound
04:20 - Mains wiring and dangers of high voltage DC string inverters
05:43 - Installation requirements. Electrican vs solar installer
06:40 - PCB top side
07:54 - Anti-islanding safety feature
09:56 - What's a bit of flex...
10:48 - Bottom the PCB
11:41 - Reverse engineering time
15:57 - Mains voltage and frequency detection
17:03 - Schematic

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#ElectronicsCreators #solar #microinverter

[jusaca]

Really interesting! I would love a teardown of a different micro inverter! I always think you can learn quite a lot when you compare two different products and check what the two manufactures did similiar and where they differ. That's the interesting part! :D

[Korni]

Those little transformers TR100 and TR101 are actually current transformers to measure the current in the respective switching MOSFET and winding. 
The current passes through the metal strip over the top of the ferrite core ( primary winding with 1 turn) and inside the core is the secondary winding with e.g. 100 turns. The sec winding is accessible on the two outermost pins on the left side. all the remaining Pins are NC and soldered just for mechanical stability.

[quetzal]

I have 17 Enphase microinverters on my roof, installed 7 years ago. Over last 2 years, four of them have failed one by one, which is about 600 times their claimed failure rate of 50 per million per year. I suspect they would have lasted longer in Arizona or Australia, but in wet, humid and often overcast Southeast US, with all the thermal expansion and contraction, you just can't keep moisture out of those boxes no matter how hard you try. Theoretically they are under warranty but kind of a nightmare getting them replaced, because I'm too old to be getting up on the roof and the outfit that installed them is no longer in business. Enphase doesn't like dealing with homeowners anyway, so I have to find a certified Enphase installer willing to work on somebody else's system, not so easy. And the icing on the cake, so to speak - the warranty doesn't cover labor!

[theshemullet]

Thanks! I liked the way you did the schematic over the parts. Makes it a lot easier to comprehend.

[RickS-zjsu]

Dave the TMS320 is a mainstay of solar (and motor control). Especially the Piccolo family. Why? They have a High Resolution PWM (HRPWM) that uses some magic technique to get PWM resolution greater than the clock for very precise mico adjustments. I think it's 150pico second steps (less than 200ps anyway)! I expected to see a TMS320 and lo and behold we have it.

[nissarin]

Regarding the AC plug - there are essentially two versions: daisy chain (double AC plug) or trunk like this one (you plug it into "T" connector on trunk AC cable)

[McTroyd]

I had never heard of Hoymiles before the hardware appeared in your mailbag. Apparently we've all been missing out. Looks like they're ticking all the boxes for safety and reliability. Thanks for the teardown, despite the goop.

[XynxNet]

Love your Video. Cried a bit though watching you tearing down a unit, which was very hard to get for month here due to supply chain issues. The educational aspect was worth it, though.

[redsquirrelftw]

That was a cool tear down. A video on how these work would actually be really cool. Ex: how do they sync with the grid, and how do they detect if it goes down. Especially when there are many of these on the grid, how does one inverter not think another inverter is "the grid" and keep going, for example. I presume it goes by current draw, if grid goes down it will try to pull massive current?

[MattyEngland]

I had to replace the relays on a full size inverter that weighed about 30kg. Some scary caps in there, I definitely triple checked they were discharged 👍 Was a very nicely designed piece of kit, very high quality boards in it.

[onit]

The electrolytic capacitors store energy to balance the 2x50Hz mains power pulsation, not clouds or birds covering the panel.

[abisaiamatalo]

Great video. Watching all the way from Western Kenya.

[AnatoFIN]

That goo looked nice, I’m ordering 10 of these. I would love a teardown of a different micro inverter!

[JFirnQ]

Very interesting teardown and going through the path like that. I would like to see another to see how they compare to be honest.

[todayonthebench]

To a degree I wouldn't be surprised if the "transformer" Dave suspects to be the main isolation transformer to simply be an inductor.

And instead have the two DC-DC converters handle the isolation. And I suspect this to be the case given the two optocouplers top left at 21:30 going over to towards the "transformer". And there is more optocouplers on the back of the board for this region too.

The advantage of isolating in the DC-DC ones is that one can make a compact design able to handle high power.
And then use a class D output stage to generate the low frequency AC for the mains voltage. Ferrite transformers don't tend to like low frequency stuff, especially at high currents. Tends to over saturate and do a poor job. But this isn't a problem if one switches a class D amp at high frequencies to generate a low frequency signal. Efficiency is typically fairly decent too.

[tanishqbhaiji]

Thank you Dave, I really wanted to see a teardown of a microinverter.

[InssiAjaton]

Interesting black "goo". I have disassembled two IGBT modules at different times. In comparison to your semi rigid stuff, what I found inside was crystal clear stuff (except the black burnt traces indicating electrical tunneling). But, clear or already burnt, it still was sticky and stretchy beyond my belief. The modules were about 6" by 3" by 0.5". They contained a 6 diode 3-phase rectifier bridge and 4 IGBT H-bridge for variable frequency drive and a "bonus" IGBT for a brake. It took me over ten hours to pull most of the goo out with tweezers, forceps, small screw driver and exacto knife. Half of the time was spent on cleaning my tools with paper towels...

[Randrew]

A few years ago I opened an Enphase microinverter and it was fully potted with the same kind of material. Yup, it liked to stick in components like inductors :) In my case, the potting material seemed to kind of flow back into place with a little bit of heat and time - warmed it over 30 minutes or so on low temp in my "projects oven" in the garage.

Looking back in my circuit pics, the Enphase inverters (at least the model I have) don't have fusing in the PV input side either. And they have the same double-transformers that you showed here, so I'll guess the same push-pull "interleaved" drive that you pondered of them. I apparently didn't take pictures of the bottom side where the FETs live.

[russellashburn]

It would be cool to see some testing on these before you tear them down. Hooking them up to the lab power supplies and measuring output waveform and the thermal output at the case would be examples. Maybe also do some over driving of the inputs and see what breaks first?

[TobyRobb]

I enjoyed this teardown. Pretty popular devices right now.