LScamper wrote:
OK first things first. The D13009K that you ordered is not an FET, it is a transistor! I don't know what the actual part that gave up is, I have not tried to look it up. You can not just replace a transistor with an FET!!! The drive circuit is much different.
Second, the buzzing most likely is an inductor saturating. As you increase the output the inductor stays on longer and the voltage across it increases. At some point it will saturate. When that happens the current will spike in the output transistors or FET which ever is used. When the current spikes the power dissipation (heat) increases rapidly as you have seen.
Next is the rating of the transistors that you ordered, 12A. With two in parallel as it looks to be that would only be good for 24 Amps. Surprised they survived at 30 A, but still not sure what the actual parts in the supply are.
Yep, the part specified is a BJT and not a FET so now the design is much, much different...
