Re: PWM in a switching power supply
- From: w_tom <w_tom1@xxxxxxxxxxx>
- Date: Fri, 27 May 2005 18:23:52 -0400
> ... its Fourier spectrum will ONLY contain the fundamental
> frequency and harmonics.
That's correct and consistent with what I had posted. Those
harmonics are the different frequencies. As those harmonics
increase magnitude (contain more energy), then the transformer
is confronted by other frequencies with more power. As noted
earlier, this can cause increased energy dissipation in the
transformer and elsewhere.
Meanwhile I did not even try to say where most energy is
lost. Why do criticize me for something that was not even
posted? To argue semantics?
An unloaded power supply must not be damaged by no load.
Any power supply that is damaged by a no load condition is
typical of something bought by a bean counter - the enemy of
innovators, responsible manufacturers, and those educated in
computer electronics. No load must not damage a properly
designed switching power supply.
> Someone who's an expert at filter design could very well not
> know the first thing about switcher design.
So what? That is not what I said and is completely
irrelevant to what I did say. A filter expert need not know
anything about switching power supplies. But a power supply
designer better damn well understand the principles of filter
design. Why does Joel read reverse logic into a post? Why
post what is both irrelevant and not even stated? Joel is
arguing semantics rather than trying to help or answer the
OP. Don't let him confuse you.
Joel Kolstad wrote:
> Uh, no, it doesn't! If I give you a periodic signal of a certain frequency,
> it doesn't matter WHAT it 'looks' like, its Fourier spectrum will ONLY contain
> the fundamental frequency and harmonics. Changing what it 'looks' like (e.g.,
> the duty cycle of a square wave) only changes the magnitudes of the harmonics.
>
> > This and other compromises are why the switching
> > power supply cannot have 100% efficiency.
>
> Overall most switchers lose far more efficiency in the switches than they do
> in the core.
>
> > Unloaded switching power supplies do not break.
>
> Some do. :-) Although you could convince me that such switchers are, by
> definition, poorly designed.
>
> > Chokes permit energy at some frequency to be converted to
> > energy at other frequencies. Chokes permits the design to
> > intergrate filters with sharper cutoff frequencies. Chokes
> > are essential to better EMC solutions. Chokes can store
> > energy at certain key operational points.
>
> Where do you get this stuff? Some generic "everything you wanted to know
> about electronics" encyclopedia? A lot of what you say is factually correct,
> just not at all relevant to the discussion at hand.
>
> > To better appreciate the value
> > and energy conservation of chokes, learn fundamentals of
> > filter design.
>
> Someone who's an expert at filter design could very well not know the first
> thing about switcher design. They're pretty disparate areas of design, and
> really only start to overlap somewhat when you discuss output filtering,
> resonant designs, etc.
>
> ---Joel Kolstad
.
- References:
- PWM in a switching power supply
- From: BradBrigade
- Re: PWM in a switching power supply
- From: w_tom
- Re: PWM in a switching power supply
- From: Joel Kolstad
- PWM in a switching power supply
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