Protecting Inductive Loads with a Flyback Diode

When inductive loads are connected to output lines, a large counter-electromotive force may occur at switching time because of the energy stored in the inductive load. These flyback voltages can damage the outputs and/or the power supply.

To limit these flyback voltages at the inductive load, install a flyback diode across the inductive load. For best results, mount the flyback diode within 18 inches of the load. The following figure shows an example of using an external flyback diode to protect inductive loads.