We are using MP173A in a buck configuration with Vin = 250VDC. When unloaded, our 250V supply rises from 0 to 250V in approximately 10ms. The issue we are having is that the MP173A starts up around 10V, so the current drawn from our supply is very high as the MP173A boots up, because the MP173A is trying to start before our supply is at 250V. The 250V is also being dragged down as it is trying to start up, though it does get to 250V output eventually. Is it possible to increase the UVLO threshold on MP173A to approximately 230V? Is there a way to implement this functionality externally?
Our 250V supply is inside of a box I’ll call “Device A” and the MP173A is inside of a box I’ll call “Device B”. Device A and Device B are connected with a long cable. The MP173A is the only power supply inside Device B, so we do not have any power available (for use in active circuits that might form a discrete implementation of a UVLO load switch, for example) until it is fully started up. I am familiar with P-channel MOSFETs being used a load switches, and we could perhaps drive the gate with a resistive divider from our 250V input, but we would require the P-channel MOSFET to turn on very quickly to avoid our main issue of the MP173A turning on too early and drawing too much current from our supply.
Thanks in advance for your help.