>-----Original Message-----
>From: markp@CANNONTECH.COM [mailto:markp@CANNONTECH.COM]
>Sent: 12 July 2004 14:13
>To: PICLIST@MITVMA.MIT.EDU
>Subject: [EE]: Switching Power Supply Design Questions
>
>
>I am beginning the design of a switching power supply.  The
>input must accept 120VAC or 125VDC and the output needs to be
>24VDC at 3A. Exceptional efficiency is not required.  There
>are many application and design notes available to assist with
>such a design, however, I have some questions for some of you experts.
>
>I could do this with a bridge on the front end followed by a
>simple buck converter.  However, isolation between input and
>output is required.  I could accomplish this using a flyback
>arrangement but it seems I would be stuck with getting a
>custom wound transformer, which is something I don't want to do.
>
>I'm thinking about having the front end bridge followed by a
>non-regulated switcher and transformer and some filtering
>circuitry.  This will provide the isolation I need with an off
>the shelf transformer.  I'll then take this isolated DC and
>apply it to a classic buck converter that utilizes an off the
>shelf inductor.  It seems strange to chop the DC up twice but
>this appears like a simple way to get the required isolation
>while using off the shelf parts.
>
>Any comments would be appreciated.  Thanks.
>
>M Peterson

The SEPIC converter topology puts a capacitor between the input and output.
Not technicaly "isolation" but may be good enough for your requirements?

Regards

Mike

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