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Help with choosing diode for boost converter

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fabiodl:
I am building a boost converter 5V to 15.5V using an mt3608.
As a reference, I use this commercial module.
Figures refOpen and refLoad show its output (the oscilloscope is ac coupled) when it is open and when there's a 103mA load (a 150 ohm resistor used as a load).

To be sure it is not due to layout differences, I stripped the parts out of a module and soldered my own parts on it.
When only the inductor and the capacitors are replaced (with   this inductor SRR1050A-220Y
and  these caps C3216X5R1V226M160AC) I get the outputs in figures clOpen and clLoad for open output and 150 ohm load, respectively. The ripple when the output is open is slighly smaller, the one over load is slightly worse.

The problem rises when I replace the original diode (with marking SS34) with  this diode SSA34HE3_A/H. As shown in figures dOpen and dLoad, the output ripple reaches 4Vpp when under load.

I also tried  this diode SS34FA and an 1N5817, which I found in the datasheet for another boost converer (the mc34063ad) but they are even worse.

With what criteria should I choose the diode? I thought I just needed something with low Vf, enough high reverse V and enough current capability, but I am clearly missing something

trobbins:
You don't provide info on what the C and L were, and why you chose the alternatives.   Also no info on how and where you probed for the waveforms.

fabiodl:
The original C and L were 10uf and 22uH, respectively.
I probed the waveforms at the module's output.

nctnico:
How are you probing? Likely you are picking up the switching noise which does depend on the speed and recovery parameters of the diode. A soft-recovery diode combined with an RC snubber can reduce the noise a lot. However you have to realise that the switching noise is picked up by your probe through radiated emissions; the load doesn't see it.

Siwastaja:
Reverse recovery time (and possibly sharpness, if it is of a type which has reverse recovery time) is absolutely critical. Think about it: if the diode still conducts for some time when the MOSFET has turned on, the diode and MOSFET form a total short circuit over the low-impedance capacitance you have at the output!

Hence, a schottky type tends to be the only sensible choice; traditional Schottky for low voltages, SiC for high voltages. Schottky diodes have no reverse recovery time (although they do have junction capacitance which causes a similar switching loss element, but this usually isn't a huge problem; by all means calculate it to be pedantic).

Before SiC diodes, we were forced to balance  between minimal reverse recovery time and softness factor, and possibly add RC snubbers to dampen the oscillation caused by the short circuit current charging layout parasitic L; or just slow down the MOSFET turn-on time. All such measures caused quite some heavy switching loss. Now with SiC diodes available, with zero reverse recovery time, such practices are usually not needed at all.

Of course, with your 15.5V output voltage, SiC is not needed, a standard schottky (for switching applications!) does better, and such parts have been available for several decades now.

But keep your eye on the reverse leakage spec of the schottky diodes. Lowest Vf types, looking appealing at first sight, may have very high off-time leakage, possibly causing thermal runaway. Likely not a huge problem at Vr=15.5V, unless you run very close to maximum ratings or fail at cooling the devices.

Don't fall into the trap of wondering where the reverse recovery times are listed. Ignore the parameter in parametric searches and don't look for it in the datasheets: it's not listed because schottky diodes do not have this thing at all. (Took me a year to figure this out...)

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