Lesson3/Learning Event 3
CAPACTIVE-DISCHARGE IGNITION SYSTEM
FIGURE 28. CAPACITIVE-DISCHARGE IGNITION SYSTEM.
This system offers several advantages over the other systems.
It is similiar to full transistor-magnetic control, except that certain components have been added to
the primary circuit. These are the power converter, capacitor, and thyristor or siliconcontrolled
rectifier (SCR). The power converter has an output voltage of 250 to 300 volts. This voltage is
used to charge the capacitor with the thyristor in its off condition. When the thyristor rate (1)
receives a signal from the pulse generator, the circuit from the anode (2) to the cathode (3) is
closed, and the capacitor immediately discharges at a high rate through the primary. A high
secondary voltage can be reached about 100 times faster with the capacitive-discharge system than
with the inductive systems. This decreases spark plug fouling, materially increasing potential spark
plug life. Another advantage is that it uses less current than either the conventional system or the
other solid-state systems. This means less demand on the battery during starts and a potentially
longer battery life.