Good day to all. Not long ago, I started designing InnoSwitch3-CP based UPS on an output voltage of 24V and a current of 2A. Of course, if you open the DataSheet to this chip, then the manufacturer does not mention any 24V, but it’s about 5V, 6V, 9V, 12V, 15V. But without hesitation, calculating the feedback divider at 24V, picking up the necessary 220/24 transformer and calculating the necessary nodes in the circuit a bit, I proceeded to wiring the printed circuit board. In practice, when the circuit board was already at hand and nothing stopped me from starting my UPS, I ran into a problem. Namely, as it turned out, the projected UPS functioned in the twentieth century, but the picture changed dramatically when the minimum load was connected. In the process of experiments, even with a load of 224 ohms, my UPS did not start. After that, I began to study in more detail all types of protection of the InnoSwitch3-CP chip used by me, as well as having armed myself with a multimeter and an oscilloscope, I began to analyze the operation of my UPS. As a result of all the research, I came to the conclusion that the protection works in the secondary circuit and it is connected with the "Output Constant Current and Constant Power Regulation", or with the "Output Overload Protection", but either because of the "clumsy" level of English, or from Because of problems with logic, I can’t figure out how to get around these problems. Maybe someone who has a lot more experience than me in designing the UPS can suggest a solution to the problem, and maybe someone worked with this chip and also encountered similar difficulties. Do not judge strictly, I attach a link to the topic: oscillograms, the circuit of my UPS, the DataSheet of the transformer as well as the DataSheet of the microcircuit. I would also like to immediately clarify about the output. In the passport of the microcircuit, a threshold voltage of VOUT 27V is indicated, then why PI EXPERT recommends installing a zener diode on this output?