[SOLVED] Diode reverse recovery current and forward recovery voltage

[bowman1710]

Hi guys,

For this part:

**broken link removed**

It mentions zero reverse recovery voltage and zero recovery voltage.

Am I right in saying, that normally a diode when switched in the reverse condition, the diode normally conducts in the other direction as the forward voltage bleeds off. During this time current flowing through this will be fairly large (compared to leakage). Is this just saying that there will non of these characteristics in this part?

Also how does this effect efficiency compared to having a device with a lower Vf value? Is it better to have this zero voltage/current or a lower Vf diode?

 

[FvM]

Reverse recovery and forward recovery effects are established by minority charge carriers that have to be pulled out of respectively pushed into the junction of bipolar diodes. Schottky diodes are (theorectically) free of recovery charge.

These effects are observed in swaitching operation (dynamic characteristics) while forward voltage is a static parameter. Which parameters are more important depends on the application, e.g. switching frequency and switched voltage.

 

[D.A.(Tony)Stewart]

Cree states " This is a majority carrier diode, so there is no reverse recovery charge" but then no test results are given.

There are 4 separate losses; 2 dynamic , turn On, off and steady On conduction loss and reverse leakage loss.

But the switch interaction be included as losses and gains interact between diode and switch. Then there is a designer option of di/dt effects.

It turns out Cree's majority carrier Si-C power diode has worse conduction losses than similar Si diodes but much lower dynamic losses and zero reverse loss. Apparently that link reports improvement with higher di/dt on Si-C diodes so the net gain is lower losses at higher frequency switched loads.

They cost a lot more though.

Here Si-C diode is compared with others with 2006 technology.

Si-C has improved for superior performance and like MOSFETs have in recent years, expect more improvements in future.

Also GaN diodes have similiar lower dynamic losses and higher dynamic prices. **broken link removed**

 

[bowman1710]

Thanks FVM for you input,

Cree states " This is a majority carrier diode, so there is no reverse recovery charge" but then no test results are given.

I too thought this was weird, especially from the data sheet just saying zero this and zero that but no backup data or test results given

I did look at eGaN but as in that report they are not suited for high power applications, more fast switching applications which is not what I need at the moment but are great devices (but pricey as you say).

I did find a good paper they have done on it which helps a bit.

**broken link removed**

I think in this situation it comes down to cost over losses really. I guess I will calculate all losses and see whether what is saved by this zero recovery and is it worth while for this cost. Also, in a practical sense whether it actually works as it should etc.

Thanks for the help

 

[FvM]

As a general rule, silicon-metal schottky diodes are good for low voltage appllications, not only fast switching. Si-C is interesting for HV + fast switching, switching frequencies > 50 kHz. For moderate frequency HV, superfast silicon diodes are usually preferable.