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John Swenson LPS


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Jakiś czas temu John Swenson inżynier z USA zrobił wrzutkę na diyaudio swojego pomysłu na zasilacz liniowy oparty na diodach Schottky-a oraz dławiku będący filtrem dla wysokich częstotliwości. Od tego czasu pomysł został sprawdzony i okrzyknięty świetnym, prostym i tanim projektem na diy zasilacza do zastosowań audio z bardzo niskimi zakłóceniami na wyjściu. Schemat projektu dla 5 DCV w załączniku.

 

The traditional cap only filter (transformer, diode bridge, big cap) produces raw DC with a sawtooth riding on top. That sawtooth produces lots of high frequency components that the regulator has to deal with. Traditional regulators do very well at low frequencies, but have lousy characteristics at high frequencies which means a fair amount of those high frequency components from the cap-only filter get through to the regulator. Fancy discrete regulators do well at blocking the high frequency components, but add cost and complexity to a PS. Our approach is to use a properly designed choke-based supply whose ripple is a perfect sine wave, no high frequency components, thus a traditional regulator works very well. The discrete regulator is not needed to deal with the high frequency components, since there aren't any.

 

All diode types except Schottkys emit a burst of ultrasonic noise as they turn off. This noise can go forward into the load circuit AND it can go back into the AC line, and it can also excite the transformer resonance. The "slow" diodes still have this ultrasonic noise. Schottkys are the only type which do not have this noise. Schottkys also usually have about half the voltage drop of other diode types and are usually faster. Which type to use depends a lot on what your supply looks like and what you are trying to optimize for.

With a traditional low voltage design with a large cap right after a bridge you get large current spikes, these produce a large amount of high frequency noise which needs to be filtered by what comes after the cap. In this type of circuit the slow diodes can help cut down on the extent of the high frequencies generated by the sharp high current pulse. BUT they still generate the ultrasonic noise.

 

This is another reason why we like to use the choke-based design. With the choke there is no steep high current pulse, so no disadvantage to Schottky diodes. You get the advantage of no ultrasonic noise, lower voltage drop (so lower power consumption in the diode) and no big massive current pulses.

 

Od tego czasu projekt rozwinął sie do stanu komercyjnego. Firma UpTone zaczęła oferować 2-wyjściowy regulowany zasilacz JS-2 ($925 ?!)

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JS-2_interior_master.jpeg

 

Więcej info na temat rozwoju projektu na github:

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Jestem ciekaw czy ktoś z Państwa miał doświadczenie z tym projektem.

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