Standard Diode in Flyback Protection: Working & Benefits

Introduction : Inductive loads such as coils, relays, and motors generate potentially damaging voltage spikes when switched off. A standard diode used across such loads; commonly called a flyback or freewheeling diode which provides a safe discharge path. This page delves into the working of standard diodes used for flyback protection and outlines their important benefits in preserving circuit components and improving reliability. It is also known as snubber diode.

Flyback Diode For motor protection

The figure-1 depicts freewheeling diode connected across the coil. Inductive load generate high voltage transients when switched OFF. Freewheeling diode provides safe discharge paths which prevents component damage.

The figure-2 depicts freewheeling diode across motor terminals. Motor protection needs high current capability and thermal considerations.

For brushed DC motors, simple freewheeeling diode is connected across motor terminals.

For stepper motors, individual diodes on each winding or integrated drive protection. Let us understand working of the circuit.

• Motor runs when current flows through the motor and diode is reverse biased (i.e. OFF).
• Motor stops when inductive kickback creates high voltage spike.
• Diode conducts and provides safe discharge path for stored magnetic energy.

Without diode protection voltage spike can reach to about 200 to 500 V and destroys control switches, relays or ECU. Moreover this causes radio interference (EMI).

With Flyback diode, voltage is limited to about 9V+0.7V diode drop. It protects all control electronics and offers smooth motor operation.v

Advantages of Flyback Diode

Following are some of the benefits of flyback diode.

1. When inductive load (e.g. motor, coil, relay) is switched off, the collapsing magnetic field generates high voltage spike. The flyback diode provides safe path for this spike and protects components and devices from damage.
2. It reduces EMI as diode helps to reduce sharp transitions.
3. Increases reliability and component lifespan.
4. Flyback diodes are simple and lower in cost.
5. The diode allows current to decay gradually which reduces stress in circuits.
6. Protects circuit from reverse voltage effects.

Conclusion: By safely dissipating energy stored in inductors and preventing harmful voltage spikes, these diodes prolong device life and enhance safety.