On Thu, Jun 26, 2008 at 9:32 PM, Thomas C. Sefranek <tcs@cmcorp.com> wrote:
>
> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
> Xiaofan Chen
> Sent: Thursday, June 26, 2008 1:04 AM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] 12 or 24V?
>
> Say if you have a single-stage buck converter, the efficiency from
> 24V->5V will be better than 48V->5V. 12V-->5V is even better.
>
> Xiaofan
>
> What???
>
> Not in my experience, they all are the same efficiency.
>
> O.K. Remind me what I have forgotten...

Typically Buck Converter works better when duty ratio is
between 0.2 to 0.8 (or 0.1 to 0.9). The efficiency will get
worse when the duty ratio is above 0.9 or below 0.1.

Of course this depends on the particular converter used.
I am now testing a 10V-32V --> 5V DC/DC converter
using synchronous buck converter. I am using one of
the best PWM controller available (LTC3835-1) in terms
of size and efficiency (well above 90% at 1A load). The
best efficiency is at 10V and the worst is at 32V.

Xiaofan
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