Hi All,
I'm designing a capacitive power supply for 230V mains. I understand that UL requires a fuse and an MOV for safety (see Figure 10 of Microchip's AN954, here), however I'm having difficulty in defining the fuse breaking current specificiation and size (energy handling rating) of the MOV.
In my circuit, assuming there's double insultation between L and N, the maximum normal current that could flow is around 60mA and under single fault conditions this could rise to 2A. The inrush current is limited to 800mA normally for 0.5ms. So I think a 100mA 'T' type fuse would be OK. My concern is that the MOV would absorb transients from the mains and during that short time could take quite a few amps. What should the breaking current of the fuse be, and how big should the MOV be?
Any help appreciated.
Mark.
I'm designing a capacitive power supply for 230V mains. I understand that UL requires a fuse and an MOV for safety (see Figure 10 of Microchip's AN954, here), however I'm having difficulty in defining the fuse breaking current specificiation and size (energy handling rating) of the MOV.
In my circuit, assuming there's double insultation between L and N, the maximum normal current that could flow is around 60mA and under single fault conditions this could rise to 2A. The inrush current is limited to 800mA normally for 0.5ms. So I think a 100mA 'T' type fuse would be OK. My concern is that the MOV would absorb transients from the mains and during that short time could take quite a few amps. What should the breaking current of the fuse be, and how big should the MOV be?
Any help appreciated.
Mark.