From: Chris Carlen
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Subject: Re: 87% ... Design requirements are here
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Date: Thu, 26 Dec 2002 18:48:06 GMT
NNTP-Posting-Date: Thu, 26 Dec 2002 10:48:06 PST
Organization: EarthLink Inc. -- http://www.EarthLink.net
Harry Dellamano wrote:
>>My, but you Brits are a cheeky bunch. Ok, then. For starters I would
>>ascertain some basic design information such as the input voltage range
>>required, the output voltage and current ranges required including
>>abnormal loads, and efficiency, noise, ripple and EMI requirements. It
>>seems keeping the magnetics as simple as possible is very important to
>>Chris, but if it were my project, I would probably go to a true flyback
>>or a push-pull dc-to-dc converter, depending on what Chris answered about
>>the project requirements.
> Hi Analog,
> Cheeky, yes. Brit, no.
> I agree, we do not have a complete spec from Chris. With that, I propose we
> can use any topology to get the job done. Hopefully this challenge it open
> to anyone interested. The designs should be submitted to a.b.s.e. on a clean
> schematic with critical parts numbers included.
Here are the constraints I am working with. If you want to work with
these parameters, then I would be able to contribute to testing. You
draw, I build and test. Final design should be "open-source" hardware
(freely offered and able to be copied and distributed as long as
original contributors' names are included.) If you don't want to do it
this way, then I can't participate in testing, and will have to make my
own device on my own, using only conceptual guidance from this forum.
11-25VDC input voltage range. 12W maximum output power. 90-350V
adjustable output voltage. Circuit should still operate down to 8V
input, but at reduced output power. If you don't like this, then forget
this 8V input functioning requirement.
Prefer a boost or flyback topology, isolation of output voltage from
input is *not* needed, but if a flyback "transformer" rather than plain
inductor is better for meeting design requirements or simplifying
circuitry, then use it.
Regulation and output ripple specs are not critical, you decide. Must
tolerate short circuited outputs, and open circuited outputs. A default
minimum load resistor or current sink is Ok, as long as it works over
the entire 90-350V output and can be disconnected if desired.
85% minimum efficiency (default load power dissipation may be included
in efficiency calcs.) No EMI requirements, for hobby use. If any extra
circuitry is needed to reduce EMI, it should be easy to and obvious how
to strip it from the basic system if it is not desired, without breaking
Preferrably use an E19/8/5 standard core size, gapped to whatever is
needed, using 3C90 or 3C94 material. Max switching frequency 200kHz. I
have these cores in these materials on hand, and some small 3F3 and 3E5
toroids on hand if needed for gate drives, but these shouldn't be needed
for a flyback anyway.
I will be leaving for Thailand on Dec 29, and will return the week of
Jan 18. If you can wait until then, I'll start testing when I return.
Otherwise, do what you want, I'll be interested to see the results when
Christopher R. Carlen
Suse 8.1 Linux 2.4.19