Dwayne Reid wrote:
> I've mentioned in the past that I had done a design for a very low
> cost DC-DC converter but that I was reluctant to share details until
> I had published it.  I'm happy to say that I finally got off my
> rear-end and did just that.
>
> Its in Electronic Design's Ideas For Design column as linked here:
> <<http://electronicdesign.com/article/ideas-for-design/build_your_own_ultra_low_cost_isolated_dc_dc_converter.aspx>http://electronicdesign.com/article/ideas-for-design/build_your_own_ultra_low_cost_isolated_dc_dc_converter.aspx>
>
> A few details:
>
> 8-32 Vdc input, 5Vdc @ 50 mA output.  Efficiency not measured but
> probably around 80% when loaded.  Much worse when un-loaded because
> unused current is dissipated in a zener diode.  This was absolutely
> NOT a concern for me because the load was essentially constant.
>
> Very low cost.  I'm using this in a couple of products and our
> component cost is about $0.60 including the common-mode choke that
> I'm using as a transformer.  We purchased several thousand pieces of
> that choke for about US $0.25 each several years ago.
>
> Really strange oscillator circuit based on one section of a dual or
> quad comparitor.  I've used both LM393 and LM339 comparitors and they
> work really well.  Oscillator relies on the open-collector output of
> the comparitor.
>
> Hope this is able to help someone.

Looks very interesting. Why was 2N5401 selected for Q1 (as opposed to a FET, 
for example)? How noisy is the circuit?

Vitaliy 

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist