Hello everyone, I need some help please. I wanted to design a circuit stepping 24 V down to 20 V for driving a dc brushless blower (SFD-BB9733H24) which is rated for 24 V and 0,5 A a bit slower. With my bench power supply I tried running the motor directly powered with 20 V and it ran perfectly fine and showed a current consumption maybe around 250 mA or 300 mA if I remember correctly. I used the TI Power Designer for choosing a buck converter circuit and it gave me the one in the upper right corner of the schematic. When powering up the PCB the motor sometimes starts spinning for a short moment and then stops. I assume that the circuit can't handle the current and therefore the output voltage breaks down? The 24 V didn't break down. Did I miss something in my design? In the oscillogram you can see the voltage across the motor. J3 is just a shorted jumper. I thought about the possibility to later add a resistor there if I am not satisfied with the fan speed.
EDIT: Now something definitely might be broken. The output was stable at 20 V when the fan was disconnected. Now the output measures 27 V (fan disconnected) and the fan spins constantly at its maximum speed with around 24 V while spinning.