Working Principle of Automotive Ignition Coil

The ignition coil is able to transform the low voltage from the vehicle into high voltage due to its structure, which is similar to a standard transformer with a larger turns ratio between the primary and secondary coils. However, the way an ignition coil operates is different from a regular transformer. Ordinary transformers work continuously, while ignition coils work intermittently, storing and releasing energy at different frequencies based on the different speeds of the engine.

When the primary coil is connected to the power source, a strong magnetic field develops around it as the current increases, and the iron core stores this magnetic energy. When the switch device disconnects the primary coil circuit, the magnetic field of the primary coil decays rapidly, inducing a high voltage in the secondary coil. The faster the magnetic field of the primary coil disappears, the larger the current at the moment when the current is broken, and the greater the turns ratio of the two coils, the higher the voltage induced by the secondary coil.