Very Efficient APFC Circuit In Faulty Industrial 960 Watt Power Supply

August 25, 2025 by Maya Posch 2 Comments

The best part about post-mortem teardowns of electronics is when you discover some unusual design features, whether or not these are related to the original fault. In the case of a recent [DiodeGoneWild] video involving the teardown of an industrial DIN-rail mounted 24 V, 960 Watt power supply, the source of the reported bang was easy enough to spot. During the subsequent teardown of this very nicely modular PSU the automatic power factor correction (APFC) board showed it to have an unusual design, which got captured in a schematic and is explained in the video.

Choosing such a APFC design seems to have been done in the name of efficiency, bypassing two of the internal diodes in the bridge rectifier with the external MOSFETs and ultrafast diodes. In short, it prevents some of the typical diode voltage drops by removing diodes in the path of the current.

Although not a new design, as succinctly pointed out in the comments by [marcogeri], it’s explained how even cutting out one diode worth of voltage drop in a PSU like this can save 10 Watt of losses. Since DIN rail PSUs rarely feature fans for active cooling, this kind of APFC design is highly relevant and helps to prevent passively cooled PSUs from spiraling into even more of a thermal nightmare.

As for the cause behind the sooty skid marks on one of the PCBs, that will be covered in the next video.

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Repurposing Server PSU For Your Charging Needs

July 17, 2012 by Mike Szczys 21 Comments

That grey box at the top of the photo is a modular power supply unit for a rack-mounted server system. [Sebastian] decided to repurpose it as a charging source for his RC batteries. He chose this HP DPS-600PB because of its power rating, efficiency, and you can get them at a reasonable price.

This is an active power factor corrected (APFC) PSU, which he says draws 40% less current than the non-APFC variety. Since he sometimes charges batteries in the field from a generator this is a big plus. But a bit of modification is necessary before it can be used as a source.

Since this is a rack device it has a set of connectors on the back. For power there are spade connectors which mate with a fin on the rack. He soldered positive and negative leads between the spades to interface with the battery chargers. The PSU won’t fire up if it’s not in the rack, so some jumper wires also need to be added connecting three of the interface pins.

With his modding all worked out he went on to use two PSUs for a 24V source, housing them to a nice carrying case while at it.