Can I equivalently use these power diodes for this test application?

[floppy32]

I need to make a test load as shown below:

As seen above, the test load is mimicking a laser diode. It is composed of two of this Schottky power diodes in series and a 100 W 50 mΩ resistor (to measure the current.)

My problem is I can only use through hole and buy from a specific vendor, so instead of the diodes above I'm planning to use two of this one in series.

In terms of current, I don't see a problem to exchange and forward voltage drops are similar. Is that correct? In my case, the diodes are dual Schottky. iShould they be connected in series like this below?

 

[stenzer]

Hi,

usually it is not recommended to parallel two diode to share the current, especially if a single one can not handle the complete current, i.e. in case one of the two diodes fail open. Due to not perfect matching, one diode (the one with lower forward voltage drop) will carry more current than the other. Have a look here[1]. This application note gives an good insighet.

[1] https://www.st.com/content/ccc/reso...df/jcr:content/translations/en.DM00098381.pdf

BR

 

[SWRmeter]

I need to make a test load as shown below:

As seen above, the test load is mimicking a laser diode. It is composed of two of this Schottky power diodes in series and a 100 W 50 mΩ resistor (to measure the current.)

My problem is I can only use through hole and buy from a specific vendor, so instead of the diodes above I'm planning to use two of this one in series.

In terms of current, I don't see a problem to exchange and forward voltage drops are similar. Is that correct? In my case, the diodes are dual Schottky. iShould they be connected in series like this below?

if you HAVE to do this, then you should put a v v small resistor in series with EACH diode.

 

[FvM]

The comments about parallel connection are more or less inappropriate for the application. The diodes of a dual diode are tightly thermally coupled, with about 1 K/W thermal resistance between junction and case. Easy to calculate that there's no risk of thermal runaway, even in DC operation.

 

[stenzer]

Hi,

dual diode are tightly thermally coupled

I agree on that. But I'm not aware about the matching of a dual diode with respect to their forward voltage. If it comes to e.g. BJTs it is mentioned in the datasheet [1]. How this looks like for diodes, I'm not aware of and I can not remember I have seen this mentioned in a diode datasheet so far.

Further, the a single diode of the pair in question can only handle 10 A, at least by checking the same component manufactured by an other company [2, 3]. As a single one can not handle the total current, I personally would not parallel them, but this is my personal based on several safety assesments.

[1] https://www.diodes.com/assets/Datasheets/ds30436.pdf
[2] https://www.vishay.com/docs/89192/mbr20100.pdf
[3] https://www.onsemi.com/pdf/datasheet/mbr20100ct-d.pdf

BR

 

[FvM]

I agree, type variation between diode chips of parallel legs can be a problem. Unfortunately there's no matching specification. Checking matching with a diode tester can help to sort out marginal exemplars.