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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: I ran some simulations (long, and images) posted by Jacques on April 23, 2006 at 11:24:46:
I have one very small suggestion.Conventional p-n junction rectifiers, found in most audio components, have the property of storing charge to support forward conduction. When the transformer secondary voltage falls below the filter capacitor voltage, the rectifiers that were feeding the capacitor turn off, but not before this stored charge is released. The release comes in the form of a small pulse of reverse current, with a very steep cutoff.
This is why HexFRED rectifiers were developed. The reverse current pulses represent a significant power loss for the high frequencies employed by switching power supplies. HexFRED and similar diodes use refined geometry and doping profiles to minimize the stored charge requirement.
CREE silicon carbide Schottky rectifiers were developed to avoid the stored charge altogether for high voltage applications: Schottky diodes are majority-carrier devices and do not exhibit this power loss mechanism, but silicon Schottky diodes are limited to low reverse voltages.
Both the HexFRED and silicon carbide Schottky rectifiers have been used by tweakers to reduce the power supply noise in conventional audio products.
I'm not sure how you could model the effect of the reverse current pulses on the power supply harmonics. Perhaps there is an application note for one of the advanced rectifiers with some detail on the stored charge.
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Follow Ups
- Beautiful! Thank you! - Al Sekela 14:51:27 04/23/06 (0)
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