When working with MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), a common challenge is dealing with avalanche energy. MOSFETs can experience voltage spikes due to inductive loads, leading to damaging energy surges that might cause permanent damage to the component. This phenomenon occurs when a MOSFET is subjected to a reverse voltage that exceeds its maximum threshold, triggering an avalanche breakdown.

The Problem :

The solution to preventing MOSFET damage from avalanche energy is simple: use a flyback diode (also called a freewheeling diode) to safely absorb these voltage spikes. The diode offers a path for the excess current to flow, protecting your MOSFET.

Example :

Imagine you’re controlling a motor with a MOSFET. When the motor suddenly turns off, its magnetic field collapses, creating a voltage spike. Without a diode, this spike could damage your MOSFET. But if you add a flyback diode across the motor, it will safely redirect the spike’s energy, ensuring the MOSFET stays intact.

Sample Calculation :

To calculate the required flyback diode’s reverse voltage, consider the MOSFET’s Vds rating (e.g., 30V).

Choose a diode with a reverse voltage rating of at least 30% higher (e.g., 40V).

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