Power supply failing when turned on, but doesn't fail if voltage is slowly applied?
What you are looking for is called a &quot;soft-start&quot; circuit.
It can be as simple as an NTC thermistor or &quot;inrush current limiter&quot;.  It is just a resistor with a large temperature coefficient.  This means it will have good resistance at first, but quickly go to near zero resistance as the circuit comes up.