Flyback Diode. A flyback diode is a diode connected across an inductor used to eliminate flyback which is the sudden voltage spike seen across an inductive load when its supply current is suddenly reduced or interrupted. The flyback diode reduces the high voltages present when coils are switched off.
A flyback diode or freewheeling diode is placed with reverse polarity from the power supply and in parallel to the relay s inductance coil. The use of a diode in a relay circuit prevents huge voltage spikes from arising when the power supply is disconnected. A flyback diode is a diode placed in parallel with a coil in switching circuits.
If the voltage across a flyback diode is negative circuit current is flowing and switch is closed no current can flow from the diode it is off or reverse biased.
It is used in circuits in which inductive loads are controlled by switches and in switching power supplies and inverters. Inductive flyback refers to the voltage spike created by an inductor when its power supply is suddenly reduced or removed. The above image shows the same inductor circuit but with additionally a flyback diode. A flyback diode is also called as freewheeling diode.
