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fredo
Guest
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 Posted:
Sat Nov 26, 2005 5:35 pm Post subject:
rectifier efficiency |
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At higher frequencies, the rectifier seems to perform lower conversion
efficiency.
What is the reason?
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John Popelish
Guest
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| Posted:
Sat Nov 26, 2005 5:35 pm Post subject:
Re: rectifier efficiency |
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fredo wrote:
| Quote: | At higher frequencies, the rectifier seems to perform lower conversion
efficiency.
What is the reason?
In over simplified terms, the junction stores charge carriers. It |
takes a while for them to fill up and provide a low resistance path
when the junction is forward biased, and a while for them to be pulled
out of the junction before it acts like an insulator when reverse
biased. The higher the frequency, the bigger part of each cycle these
transient processes take. |
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fredo
Guest
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| Posted:
Sun Nov 27, 2005 5:35 pm Post subject:
Re: rectifier efficiency |
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Thank you for your response.
Just from what you mentioned, it seems that while this junction moves
from the condition of a forward-biased to a reverse-biased, at higher
frequency, it always causes some delay. Right? And this delay is the
cause of the low conversion efficiency in low-frequency rectifier.
Then, should there be a high frequency rectifier attaining some better
efficiency in terms of conversion efficiency?
Besides, while considering power dissipation across the diodes, at high
frequencies, the power efficiency between IN and OUT is a great
variation. I wonder if this is only a matter of matching.
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John Popelish
Guest
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| Posted:
Mon Nov 28, 2005 1:35 am Post subject:
Re: rectifier efficiency |
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fredo wrote:
| Quote: | Thank you for your response.
Just from what you mentioned, it seems that while this junction moves
from the condition of a forward-biased to a reverse-biased, at higher
frequency, it always causes some delay. Right? And this delay is the
cause of the low conversion efficiency in low-frequency rectifier.
Then, should there be a high frequency rectifier attaining some better
efficiency in terms of conversion efficiency?
|
There are several rectifier technologies that have different
frequency-efficiency relationships. There are PN junction diodes made
with various semiconductor materials and with process variations
(doping, grading, additional elements added to alter the lifetimes
charge carrier pairs, etc) to optimize various properties and
compromise others. There are also Schottky half junction diodes that
involve a metal, semiconductor junction. Conduction in these
materials does not involve positive charge carriers in the metal half
of the junction, only electrons. This type is very fast at switching
from conducting to insulating, but have high junction capacitance that
passes some current in the reverse biased direction. They also have
much lower reverse break down voltages than PN junctions made with the
same semiconductor material. but also about half of the forward biased
voltage drop. When made with a very high band gap semiconductor, they
can achieve hundreds of volts reverse capability.
| Quote: | Besides, while considering power dissipation across the diodes, at high
frequencies, the power efficiency between IN and OUT is a great
variation.
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Not sure what your point is. The difference between power in and
power out should be the power dissipated by the diode.
| Quote: | I wonder if this is only a matter of matching.
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Finding the best technology and device type for a given application is
a big part of the design problem. Keeping up with the technological
advances and production availability is an ongoing task. |
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