I just found an interesting Schottky-rectifier from Vishay, the V30100S:
http://www.vishay.com/docs/88941/v30100s.pdf
Especially for power amps the extremely low forward voltage could be very handy, it's just 0.55 V for 10 A and only 0.4 V for 2 A - lower than any of these high-speed diodes.
Unfortunately reverse current is very high, at least one order of magnitude larger than other rectifiers. Junction capacitance is also very large*.
Does somebody see a drawback to this?
The price is rather low, it's tempting to use them for the power amp...
Have fun, Hannes
*could be useful for pushing resonances into harmless areas, where's the Snubber-article...
http://www.vishay.com/docs/88941/v30100s.pdf
Especially for power amps the extremely low forward voltage could be very handy, it's just 0.55 V for 10 A and only 0.4 V for 2 A - lower than any of these high-speed diodes.
Unfortunately reverse current is very high, at least one order of magnitude larger than other rectifiers. Junction capacitance is also very large*.
Does somebody see a drawback to this?
The price is rather low, it's tempting to use them for the power amp...
Have fun, Hannes
*could be useful for pushing resonances into harmless areas, where's the Snubber-article...
h_a said:
Scottky Power diodes have lower VF than silicon. I have seen some Power Schottky with 0.60 Volt10 Ampere. But do not remember which ones.
Schottky is always high speed, more or less. The question is if high speed is good or not so good, when delivering higher currents 50-60 Hertz AC.
To one supply that is supposed to be CLEAN DC = 0 Hertz AC.
Paralleling Schottkys would lower Voltage drop a bit further. As this halfs the current in each diode. Say using 8 diodes in a bridge. ( Normally 4 )
Ordinary Silicon Diodes can also be paralleled, to lower VF a bit.
I have never used anyhing but low cost silicon rectifier diodes.
And I am quite sure
I Never In My Life Will use anything but low cost SILICON here
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glass passivated silicon is what is used in most high current bridges. glass passivated devices are about 1.1V forward drop. when your rail voltages are +/- 50 V or more, a few tenths of a volt wouldn't get me to spend 2 or 3 times as much money on a bridge. there are now silicon carbide diodes out there. for now they're more expensive, and have a 2 volt drop, but are really high speed devices made for switching power supplies operating at 1 Mhz or higher. i think they can handle more current per square millimeter than silicon or schottky devices.
Seems some of you are too lazy to read all posts, eh?
The ones I can easily access have 1.4 V at 50 A...
Maybe you should enjoy a look at the linked datasheet first? These are 30 A Schottkys with 250 A peak rating. Not much difference to silicon at all.
Read the first post carefully and try again
A standard Schottky is not much lower than Silicon at same currents.
Have fun, Hannes
The ones I can easily access have 1.4 V at 50 A...
Maybe you should enjoy a look at the linked datasheet first? These are 30 A Schottkys with 250 A peak rating. Not much difference to silicon at all.
Read the first post carefully and try again
A standard Schottky is not much lower than Silicon at same currents.
Have fun, Hannes
I must admit that I usually fly over most (though not all) posts, including yours.
Having said that, if I look at the datasheets that I have at hand and compare diodes of the same rating (ok, my shottky’s are dual devices) the shottkys have invariably a much lower forward voltage drop than the standard diodes.
Example Ixys DSEP 15-03A (15 A, 300 V) VF _ IF = 15 A: TVJ = 150°C 1.21V, TVJ = 25°C 1.68 V
IR 16CTQ100 (16Amp, 100V) VFM Max. Forward Voltage Drop 0.72 V @ 8A (Per Leg) at TJ = 25 °C 0.58 V @ 8A (0.69 V @ 16A) TJ = 125 °C
The datasheets have diagrams with the related curves, and it becomes even more apparent. Same with other packages / higher current ratings, e.g. IR 40CPQ100 against various 30A diodes.
Thanks for the reference to the IR-schottky!
I'm not a diode guru, I have to admit that I randomly picked a cheap Schottky diode with comparable ratings from the Digikey-catalogue and it didn't perform that well.
So the IR 16CTQ100 is 0.72 V at 25°C at 8 A (you state 0.58 V). For identical conditions the V30100S is about 0.52 V.
Ok that's not that much.
The really nice thing is the price! Your IR 16CTQ100 costs at Digikey 1.93 Euro in the uninsulated TO-220 package, the VF30100S goes for 1.17 Euro in the insulated TO-220 package.
It's not exactly half the price, but good value for the money for sure. There are even standard Silcon-bridges that cost more than 4 of these.
Have fun, Hannes
I'm not a diode guru, I have to admit that I randomly picked a cheap Schottky diode with comparable ratings from the Digikey-catalogue and it didn't perform that well.
So the IR 16CTQ100 is 0.72 V at 25°C at 8 A (you state 0.58 V). For identical conditions the V30100S is about 0.52 V.
Ok that's not that much.
The really nice thing is the price! Your IR 16CTQ100 costs at Digikey 1.93 Euro in the uninsulated TO-220 package, the VF30100S goes for 1.17 Euro in the insulated TO-220 package.
It's not exactly half the price, but good value for the money for sure. There are even standard Silcon-bridges that cost more than 4 of these.
Have fun, Hannes
OK, omitted the comma after 25 °C - thanks for spotting
On prices, Ebay is your frind; I found all my diodes (IXYS FREDs, IR Shottky's) at Ebay well below EUR 1 per piece, often still in the original tubes, and even the same types that boutique component suppliers (Thel in Germany) sell for an arm and a leg. Lastly, I suggest to use PSUDII to model your power supply to get the max current peaks, and if low forward voltage drop is your primary goal, run them hot (but not too hot).
Schottkys are the best when you are after low drop.
No question about this
The only hookup with schottkys is that they often come for a bit lower voltages.
But if your power supplies are not too high voltage, then it is a good option to get lowest power losses.
I do not know the current developement in power Schottky.
But I wouldn't be surprised if there are now higher voltage devices, too.
Now there is, of course, an easy way to compensate: One extra winding in your transformer secondary .....
Best Regards to Dannemark, Dannebrogen och Hannes
You are quite alright by me, man!
The old school very, very Gentle Man of Svea Rike = Sve-rige = Sweden
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No question about this
The only hookup with schottkys is that they often come for a bit lower voltages.
But if your power supplies are not too high voltage, then it is a good option to get lowest power losses.
I do not know the current developement in power Schottky.
But I wouldn't be surprised if there are now higher voltage devices, too.
Now there is, of course, an easy way to compensate: One extra winding in your transformer secondary .....
Best Regards to Dannemark, Dannebrogen och Hannes
You are quite alright by me, man!
The old school very, very Gentle Man of Svea Rike = Sve-rige = Sweden
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