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Close the switch to eliminate the surges through the diode.A flyback diode is a diode used to eliminate flyback,which is the sudden voltage spike seen across an inductive load when its supply voltage is suddenly reduced or removed. When a fully energized inductor gets disconnected (when the transistor turns off) the accumulated charge has nowhere to go. Once the transistor turns on again the stored energy releases in a sudden jolt in the form of a high voltage spike. A flyback diode solves the problem by allowing the inductor to draw
current from itself (thus, "flyback") in a
continuous loop until the energy is dissipated through losses in the wire, diode etc. thus striving the inductor. This lasts no more than a few mS. Flyback diodes are used whenever inductive loads are switched off by silicon components: in relay drivers, H-bridge motor drivers, and so on. A switched-mode power supply also
exploits this effect, but the energy is not dissipated to heat and instead used to pump a packet of additional charge into a capacitor, in order to supply power to a load.
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