Ignition Control Module: Description and Operation

Power Stage And System:

PURPOSE
The ignition amplifier (1) functions as an electronic switch controlling the current in the ignition coil on command from the ECU (3). This function is comparable to the operation of the points in a mechanical ignition system, in that it opens and closes the coil primary ground connection.

OPERATION AND SIGNAL
Once the ECU has computed the ignition timing (based on the input signals), the value is converted into a control signal for the ignition amplifier.

When the signal goes high (+ 5V), the ignition amplifier permits the ignition coil to charge.

When the signal falls (to 0V), the ignition amplifier interrupts the current in the ignition coil primary windings, inducing a high-tension pulse in the secondary windings.

The ignition amplifier incorporates a circuit which monitors and controls the current used to charge the ignition coil (2). This keeps the voltage supplied to the coil at a constant level, assuring a full charge at all times.

Since the ignition amplifier generates heat, the unit is mounted on a heat sink attached to the body for adequate cooling. A good contact between the unit and heat sink is necessary for reliable operation of the ignition amplifier.