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Forum Index : Electronics : Heric Inverter

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kentfielddude
Senior Member

Joined: 09/05/2019
Location: United States
Posts: 112

Posted: 04:00pm 28 Aug 2026

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Was watching the EEVblog teardown of a Deye hybrid inverter. It uses a HERIC topology — an H-bridge plus two anti-parallel IGBTs that give the current somewhere to freewheel, which disconnects the panels from the grid during the off state of every PWM cycle. The two IGBTs hand over at each mains zero crossing, one for each half cycle.

The reason you'd bother: with the bridge off and the array floating, the common-mode voltage stays put instead of swinging at switching frequency. That's what kills the leakage current through the panel capacitance to earth, and it's what lets you get away with no transformer and still pass RCD and EMC. The efficiency is a nice side effect but it's not really the point.

Looks pretty simple. This guy Fraunhofer patented it back in 2002 and have gone after quite a few manufacturers over it, mostly settling out of court for royalties with the threat of a sales ban hanging over things. SMA ended up doing the same trick on the DC side instead with their H5, basically to get around it.

Patent world is weird. There's also that annoying one on recording video locally while streaming a lower quality version wirelessly at the same time, which is why you get cameras that'll do one or the other but not both.

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