DC/DC Converter (the proper diode)

[polfort]

Hi there.

Looking at the schematic (http://cds.linear.com/docs/Datasheet/3471fb.pdf) on page 16, I am asking myself what kind of diodes are recommended for a boost topology.
It is certain that it should be a fast switching diode, its capacity should be as low as possible.
What I am in doubt of is the minimum reverse voltage it must handle.
I am only referring to the boost up circuit build up around switch 1. As far as I understand, the maximum reverse voltage in that circuit is equal to the max. output voltage.
I

 

[indulis]

That is correct, but that is a minimum... go a bit higher to account for any spikes.

 

[Kevin Weddle]

A fast switching diode might not be necessary for a DC to DC power supply. Schotkey diodes have a P region that is just metal, don't quote me. But the diodes you want have the voltage and current specifications that are just adequate. Using high current diodes, or low current diodes at their maximum rating, is not efficient.

 

[Hero999]

A fast switching diode might not be necessary for a DC to DC power supply.

No.

A DC-DC converter is a switched mode power supply which switches at a high frequency so a fast switching diode is required.

Using high current diodes, or low current diodes at their maximum rating, is not efficient.

That's true, you shouldn't puch components to their maximum ratings and with diodes you have the advantage of a lower voltage loss at currents much less than the maximum rating.

 

[Kevin Weddle]

What diode couldn't you use in a DC to DC converter? Designs are mainly based on operating charactersitics. Most common diodes switch fast for many circuits, including DC to DC converters.

 

[www.electronworks.co.uk]

Your diode needs to be a Schottky diode for its speed. Any normal diode (1N4001 etc)will be too slow, the energy in the inductor will not dissipate quick enough into the output capacitor and you will get a spike where the diode and inductor meet. Not good for noise and long life of the diode

 

[indulis]

Your diode needs to be a Schottky diode for its speed.

Definitely not true. Many factors are considered when selecting diodes in DC-DC