In inductive load circuits, such as those containing solenoids, motors, or relays, the flyback diode (also known as a freewheeling diode or snubber diode) plays a crucial role in protecting the circuit from voltage spikes and potential damage. Inductive loads store energy in their magnetic fields when current flows through them. When the current is interrupted or suddenly reduced, such as when turning off a solenoid or motor, this stored energy seeks a path to discharge.
The function of the flyback diode is to provide a safe and controlled path for this stored energy to dissipate. It is connected in parallel with the inductive load, with its anode connected to the positive terminal of the load and its cathode connected to the negative terminal.
During normal operation, when the current flows through the inductive load, the flyback diode is in a reverse-biased state and remains non-conductive, having little to no effect on the circuit. However, when the power to the load is turned off or interrupted, the inductor attempts to maintain the current flow. Without the flyback diode, this sudden reduction in current could result in a rapid collapse of the magnetic field around the inductor, leading to a significant voltage spike in an attempt to keep the current flowing.
The flyback diode quickly becomes forward-biased when the voltage across the inductor exceeds its threshold voltage. This allows the stored energy to circulate through the diode in a loop, bypassing the rest of the circuit. As a result, the voltage spike is suppressed, and the energy is harmlessly dissipated across the diode. By providing this safe discharge path, the flyback diode helps prevent damage to sensitive components and ensures the overall stability and reliability of the circuit.
In summary, the function of the flyback diode in inductive load circuits is to protect the circuit from voltage spikes and potential damage by providing a controlled path for the dissipation of the inductor's stored energy when the current is interrupted.