I am trying to determine what exactly is causing the below switching regulator/ DC-DC converter module to not maintain its rated output voltage.
I am using the SPBW03G-03, which has a listed maximum output current of 700mA and an output voltage of 3.3V. The input side of the regulator is driven by approximately 45 VDC (32 VAC rectified), which is within the 18-75V input voltage limit.
What I have observed is that essentially any load will draw down the output voltage of the regulator. At full load (all inputs on, all outputs/relays activated), I am drawing approximately 150 mA, which is well within the maximum output current of the regulator. The output voltage at my full load case drops to right at 2.98V, and holds there. When the load is removed, the regulator returns to just under 3.3V (measures at about 3.28 with DMM and Oscope). The voltage drop is most pronounced when the three relays are activated (note: the relays are rated for 3V operation) with the rest of the circuit having relatively small impacts on the voltage.
Below are snapshots of my schematic. I should note I have a dummy load in for the TeensyLC just for circuit testing, and am manually triggering inputs and outputs. I apologize for the regulator not being shown, I have not gotten around to adding it to my schematic yet.
This is the first project for which I have used a switching regulator, so am am wondering if there are any significant pitfalls that I could be missing. The Meanwell documentation is limited, but I know most of the other DC/DC modules suggest input and output capacitors, which I currently have not implemented.
If anyone has some suggestions as to what the issue might be, or what noobie mistakes I have made, I would appreciate the feedback.