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From: "Richard Freeman"
Subject: Re: How to do a 220V AC to 12V DC and 24V DC without a transformer ?
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Date: Thu, 16 Jan 2003 09:50:42 +1100
NNTP-Posting-Date: Wed, 15 Jan 2003 17:48:40 EST
"Vincent Clerc" wrote in message
> I have to design a circuit that connects to the main power (220V AC) and
> transform it to 24V DC (3 amps) and 12V DC (3Amps too).
> Given the amps, a transformer based solution is to big and emits too much
most Transformerless solutions will generate even more heat than a
Transformer (in the order of 1200W or about a bar radiator with one bar on
type of heat)
> using a switching regulator but I don't know how to do that (AC/DC
> without transformer, lots of Amps).
SMPSs for this sort of application use Transformers
> Does any one have a method (or schematic) to do that ??
very very very low duty cycle PWM with a feedback loop would probably do it.
BUT ! (VERY VERY BIG BUT)
The low voltage side would not be isolated from the mains and therefore
would be VERY VERY DANGEROUS as there would be in the order of 360V DC on
1) put up with the extra weight of a Transformer if the secondary side is
going to be earthed a Toroidal Transformer will save space and weight
2) buy an off the shelf SMPS which does what you want given the level of
expertise you appear to have (judging by your need to ask this question) may
be the safest bet and of course even an SMPS will generate quite a bit of
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