So today, I conducted a long-duration (over two hours) fan driver circuit load test for my Buce module.

This is a load test of the fan driver circuit continuously outputting 100mA of current. As seen, the inductor heated up to 59.1°C (with an ambient temperature of 21°C and a supply voltage of 30V).

This is a load test of the fan driver circuit continuously outputting 400mA of current. As seen, the inductor heated up to 81.9°C.

Finally, with a 500mA load current test, the inductor heated up to 87.4°C.

Even though the test results show that the Buce module's circuit pretty much meets the specs, it's interesting that the heat source isn't the tiny SOT-23-6 Buck regulator you'd expect, but the inductor. 

You might think 87°C is bad for the circuit, but for a fan driver, it rarely runs at full power for long. Even if the circuit can handle it, your ears probably can't stand the fan noise. 

Of course, there's still room for improvement in heat dissipation, so the next version will have a better PCB layout for better cooling and use a better inductor without changing the size.