Fuse F2 protects versus over-current conditions, i m sorry can happen when the voltage is within regular limits. Imagine a quick in, say, D2. That short would draw excessive current and blow fuse F2.
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The fuse is there as second protection. Overvoltage or overstress beyond the rating the the devices could cause semiconductor switches choose Q1 to short. In this case the D1 TVS maker protects the semiconductors native an overvoltage condition, however relies on the fuse, F1 to blow if the overvoltage lasts long enough. If there were no TVS device and Q1 shorted, F1 would certainly blow avoiding further damage and also potentially hazardous conditions.
The role of a fuse is typically to avoid fire - that"s the simple protection a fuse offers - between power supply and also appliance there might be a couple of feet or metres of cable - if a quick circuit occurs in the appliance, the cable can easily come to be overheated (due come excess current) and also burn or rupture that is insulation. Without a fuse to "protect" the cable, this can lead come the direct ignition of product in the residence or workplace and suddenly what start off as a minor incident ends up with a structure burning come the ground.
Side impacts of course are danger to anyone coming into call with ruptured cable and also receiving an electric shock. A fuse prevents this by protecting the cable.
When it involves protecting "loads", a zener diode and fuse carry out a slightly different job. Lock are dubbed zener barriers in the petrochem and coal industries since they limit the voltage in ~ the terminals that "otherwise safe" equipment and also this considerably reduces the threat of one ignitable gas explode or dust explosion.
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In your case F2 simply protects the devices that is associated to her output and also F1 most likely protects the cable in between power supply and also appliance.