--===============1435851370==
Content-Type: text/plain; charset="gb2312"
Content-Transfer-Encoding: quoted-printable
X-MIME-Autoconverted: from 8bit to quoted-printable by pch.mit.edu id m3IHVfJo008811

=20
I went to Wikipedia and it tells that for a switching mode power supply, =
it is a AC-DC-AC-DC process, and since the latter conversions are at high=
 frequency, thus they need a much smaller transformer. This makes sense t=
o me, although I still don't know which one might have a higher efficienc=
y. They must have their own reason of living in the world.
=20
Would you recommend any stable and trustable power supply brand?  I need =
about 12-15V DC adjustable  and 15-20A at output.



> Date: Fri, 18 Apr 2008 09:49:27 -0700> From: marcel@carrietech.com> To:=
 piclist@mit.edu> Subject: Re: [EE]how does a power supply provide curren=
t limiting function> > >> > What makes this big difference, the MFJ one d=
oes not have a transformer> > inside?> > ________________________________=
_________________________________> >> > Hi,> one of them (the 2nd) is a l=
inear supply, while the other one (the first) is> a switching supply.> In=
 a linear supply, excess power is dissipated (meaning it needs to be big>=
 for heatsinking, plus a big line transformer), whereas in a switchmode> =
supply, the voltage conversion is very efficient, ideally 100%, so there =
is> no need for that much heatsinking, and there is also no need for a li=
ne> transformer.> Current limiting can be easily implemented in both case=
s (generally it's> done by using a sense resistor with a very small value=
 and measuring the> voltage drop across it), but in one case I guess they=
 chose not to.> - Marcel> -- > http://www
 .piclist.com PIC/SX FAQ & list archive> View/change your membership opti=
ons at> http://mailman.mit.edu/mailman/listinfo/piclist
_________________________________________________________________
MSN =D6=D0=CE=C4=CD=F8=A3=AC=D7=EE=D0=C2=CA=B1=C9=D0=C9=FA=BB=EE=D7=CA=D1=
=B6=A3=AC=B0=D7=C1=EC=BE=DB=BC=AF=C3=C5=BB=A7=A1=A3
http://cn.msn.com
--===============1435851370==
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Disposition: inline
Content-Transfer-Encoding: 7bit

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

--===============1435851370==--