The minimum load is to ensure that the DC-DC converter can operate within the manufacturer’s specification. Otherwise the output voltage level will be unstable or out of tolerance.
In most cases, we can find the minimum load requirement from the datasheet specifications for the power supply. For example, XP Power’s DDC15 series shows no minimum load required. (Please note that there will be no output current when there is no load.)
But in some cases, you may not find this minimum load information clearly in the specification. You may need to math your way to an answer from the specifications you’re given. For example, the CUI PYB15-Q24-S3 datasheet shows that its minimum output current is 200mA. Given its fixed 3.3V output, its minimum load can bet determined with a simple Ohm’s Law calculation. 3.3V/ 200mA = 16.5ohm
Similarly, linear regulators may need a minimum load to operate correctly. For more information on regulator minimum loading, take a look here: