Other Parts Discussed in Thread: UCC28740,
Hello, I am debugging a self-designed flyback switching power supply with an input of 90-900VAC and an output of 24VDC. I use the UCC28740 chip and adopt the relevant power supply circuit from the PMP41009 design. Why is it that when the input is 250VAC, after rectification, the measured voltage at the HV pin is 12V, the chip cannot work normally, and the voltage at the VDD pin is only 1.2V? May I ask what the reason is? Is this power supply circuit not suitable for my design?
