[Noisebridge-discuss] Fwd: [BerkTIPGlobal] Fwd: Re: [HH] UPS Tutorial & Teardown
john_re at fastmail.us
Tue Aug 13 18:11:02 UTC 2013
----- Original message -----
From: "Peter (peabo) Olson" <peabo at peabo.com>
To: hardwarehacking at blu.org, Tom Metro <tmetro+hhacking at gmail.com>
Subject: Re: [HH] UPS Tutorial & Teardown
Date: Mon, 12 Aug 2013 23:11:39 -0400 (EDT)
On August 12, 2013 at 2:28 AM Tom Metro <tmetro+hhacking at gmail.com>
> Here's a video that describes the 3 major architectures for
> uninterruptable power supplies, then tears apart an APC rack mount UPS
> to match up the real components to the theoretical block digram:
> I went into it figuring I already knew how a UPS worked, but still
> learned some things. (AVR UPSs really just use an auto transformer and a
> couple of relays to implement voltage boosting/reduction? That's
> surprisingly granular.)
The mind-bending moment occurs towards the end, when he tries to find
circuit which charges the backup battery. It seemingly is not there.
Imagine an H-bridge driving the primary of a transformer that is
out when the UPS has no line input. Cool. Imagine the same H-bridge
input is available. It is sort of backward. Enough that the protective
of the MOSFETs are conducting. What do you have then? A bridge
supplying current back to the battery, which coincidentally has some
capacitors to filter the voltage and help charge the battery.
Ingenious. Well it is a little more complicated, but that is the basic
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