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Registered Member #3964
Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332
Hi, I am thinking of using a bridge diode in replacement for the use of Single high current high voltage diode HALF WAVE. (please see photos below to see what i mean) KBPC3510 (BRIDGE DIODE 35 AMPS / 1000V) =>
Since it is sharing on a same Die (meaning identical internal construction), my concern is the current and voltage that will flow in it, since it has parallel diodes so the is the current equally distributed?? also, the voltage? in series diode so it also share the voltage and reads half of the voltage across it.
So is the total rating will be 2kV, 70 Amps if in single application? (but of course the voltage drop will be doubled)
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Voltage rating could be double, depends on the internal construction and check isolation test to casing in datasheet. The package is made for 35 A, so it will still only be able to dissipate heat from 35A.
Registered Member #3964
Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332
I think current capacity will also be doubled, because the bridge diode's rating of 35 Amps, is per diode. Since during the positive Half cycle of ac to be rectified will pass only one diode on the bridge, that diode is rated 35 Amps max loading. if there are 2 diodes in parallel, this will allow for more current (x2) to flow on it. However, there should be a critical identicality of both diodes in parallel due to the equality of the power (energy) flows in it so it will not burn up,(due to unequal loading, thermal increase for the diode that suffers more)
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Power diodes usually tend to share the current well, even if they are not "matched", as the "static" resistance of the die becomes much more significant than the "dynamic" one.
Registered Member #3964
Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332
Steve Conner wrote ...
Look at it this way: In normal use, each diode passes 35A half of the time, and no current for the remaining time.
In your application, all of the diodes would pass 35A all of the time, so the total heat dissipation would be doubled.
Also as far as I know, bridge rectifiers aren't integrated, they use 4 separate silicon dice, so matching isn't guaranteed.
What do you mean by all of the time? Isn't that only positive cycles they will conduct and thermally dissipate since they are all in one direction? do you mean - the current will pass in the diode even if in negative cycles?
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
The ratings of diodes are usually the average rectified current.
If the average rectified current of a full wave bridge is 35A, each diode passes 35A half of the time and 0A half of the time, so only sees 17.5A of average current.
However if the average rectified current of a half wave rectifier would be 70A, the whole diode (made of 4 individual diodes) would pass 140A half of the time and 0A half of the time, so each diode would pass 70A half of the time and 0A the other half. The component would be overloaded. So, the average rectified current when you use the bridge like a half wave rectifier, is still only 35A.
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Bridge diode to Single diode
