freewheelingdioder

A freewheeling diode, also known as a flyback diode, snubber diode, or suppressor diode, is a diode connected in parallel with an inductive load, such as a relay coil or motor. Its primary purpose is to protect switching elements, like transistors or integrated circuits, from voltage spikes that can occur when the inductive load is switched off.

When an inductive load is energized, it stores energy in its magnetic field. Upon de-energization, the magnetic field collapses, inducing a large reverse voltage (back EMF) across the inductor. This induced voltage can be significantly higher than the supply voltage and can exceed the breakdown voltage of the switching element, leading to its damage or destruction.

The freewheeling diode is connected in reverse bias during normal operation. However, when the switching element turns off, the induced reverse voltage forward biases the freewheeling diode. This allows the current flowing through the inductor to continue to circulate through the diode and the inductor itself, forming a closed loop. This freewheeling action dissipates the stored energy in the inductor as heat, gradually reducing the current and preventing the voltage spike from reaching the switching element.

By providing a path for the inductive current to flow, the freewheeling diode effectively clamps the voltage across the switching element to a safe level, typically around the forward voltage drop of the diode plus the supply voltage. This simple yet crucial component significantly extends the lifespan and reliability of electronic circuits that control inductive loads. Freewheeling diodes are commonly found in motor control circuits, relay drivers, and power switching applications.