Inductive Kickback and Flyback Diode – Inductor

Inductors don’t instantly start or stop conducting current. That is a problem for series components that are trying to stop the current instantly. The inductor raises the voltage as needed to keep the current flowing for a brief period of time. That may fry some components.

Inductive flyback or kickback flashes an LED demo circuit for learning electronics shorts 87
Inductive flyback or kickback flashes an LED demo circuit for learning electronics shorts 87

A reverse biased diode that is parallel to the inductor wont conduct current while the power is applied. That will be when the switch is closed in example shown in the diagram.

When power is cut off, the magnetic field that the inductor built up collapses and keeps pushing current while it collapses. It will build a large voltage if need be to keep that current flowing. That is called kickback.

That current can be redirected to flow through the parallel diode and back to the inductor. The current will stop as soon as the magnetic field is done collapsing.

An LED shouldn’t be used as the flyback diode for a practical circuit. Usually a rectifier diode is used. But, for low voltage demonstration purposes, you can watch the LED light up briefly when the inductor kicks. You will also notice that right when closing the mechanical switch, the LED flashes sometimes. That’s called switch bounce, where the mechanical switch contacts touch each other, but then bounce apart briefly before coming back into contact again.

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