A diode is a commonly used component in electronic circuits. It has the characteristic of unidirectional conductivity, meaning current can only flow through the diode in one direction.

Diodes play a crucial role in various modulation circuits such as rectifier circuits, detector circuits, and voltage regulator circuits. It is thanks to the invention of components like diodes that we have today's rich and diverse electronic information world.

In many control circuits, we can see one or two diodes connected in parallel with a relay. So what is the function of these diodes?

Generally, relays are controlled by a transistor to open and close the relay. The relay coil closes when energized and opens when de-energized.

So what is the function of the diode?

Relay with a Diode in Parallel When the relay is closed, the circuit enters the working state, and an induced electromotive force (EMF) is generated in the coil.

However, at the moment the relay opens, according to the principle of electromagnetic induction, the current cannot change abruptly. The induced EMF generated in the coil will produce a reverse voltage on the components in the circuit.

If the reverse voltage is higher than the reverse breakdown voltage of the component, it may damage the component in the circuit.

To prevent component damage, a freewheeling diode can be connected in parallel across the circuit.

When the current flowing through the coil disappears, the induced electromotive force generated by the coil is dissipated through the circuit formed by the diode and the coil, thus providing freewheeling protection and protecting other components in the circuit from reverse voltage.