internal feedback loop
The AG30P12 HV modules are not like any other kind of HV module. They contain only a driver, I mean the control input sets somehow the output voltage but it has no internal feedback. I played with it a lot and discovered that they have just two transistors as a driver circuit. Something like this
So the control is very non-linear, the output is not stable at all. The CTRL input is just transistor base bias. I strongly suggest adding an internal feedback loop using an opamp This is part of the HV supply I built for GEM detector project
The opamp may need some compensation, but in my case worked stable without it. It is possible of course to make a feedback loop in the FPGA but with all ADC and DAC latencies, it would be not trivial. Also, safety issues may arrive since the output is out of control when the digital loop is not working. Another issue is that the CTRL input range is quite narrow so it greatly reduces effective DAC resolution