What is a Capacitor-Discharge Ignition System?

When operating vehicles or other systems that run on engines, an ignition device is required to spark the fuel mixture which in turn burns to create the energy needed to operate the system. In particular, a capacitor-discharge ignition system, or a CDI system, is an instantaneous ignition system that builds charge and discharges in a fraction of a second, allowing for a quick closing or opening of the electrical circuit passing through the system. As a complex system with many components that contribute to its powerful electric current, the CDI system has specific applications and advantages. As such, this blog will offer insight to the operating principle of a capacitor-discharge system and its many parts.

A CDI system begins when the user engages with the ignition to begin the engine, such as by turning a key on a motorbike. The system then generates and stores a charge before sending it to start the engine. The power passes through a capacitor and is then transferred to an induction coil, that of which acts as a transformer to allow the energy to undergo it without interference. As such, a CDI system allows an engine to stay running so long as there is a constant charge within the power source. Of the many components that comprise this system, it can be broken down into a few main parts: the stator, the charging coil, the hall sensor, the flywheel, and the timing mark.

The flywheel is a round, magnetic component that turns on the crankshaft, and the stator is a flat component used to contain the electrical coils of wire as well as turn on the induction coil and the battery charging circuits. Within the stator is the charging coil, that of which supplies power to the spark plug as the flywheel operates. At the same time, a hall sensor is used to detect the exact point when the flywheel’s magnet switches poles from north to south. When this change in polarity occurs, the system sends one tiny pulse to the CDI box, causing it to dump its energy from the charging capacitor to the high voltage transformer. The transformer then absorbs all unused energy.

Similar to the trigger point on the flywheel, the timing mark is a trigger point on the stator plate that allows a certain amount of positive charge to enter the capacitor. Finally, the circuit trigger is often a switch used to identify when the capacitor is fully charged and stop any charge from entering the capacitor. With a very quick charging time, the capacitor-discharge ignition system is ideal for applications where significant dwell time during ignition is not available. At the same time, CDI systems generate a great amount of electromagnetic noise and therefore are rarely used by automobile manufacturers.

For applications where capacitor-discharge ignition systems work well, consider sourcing the various high-caliber components your system requires from ASAP NSN Parts, a leading online distributor of electrical part types. Owned and operated by ASAP Semiconductor, we boast around-the-clock service and access to an ever-expanding inventory of over 2 billion parts unparalleled in size and quality. When you take the time to browse our catalog, as organized into categories on our website, make sure to submit a Request for Quote (RFQ) form for any items that seem of interest to you. Our team of market professionals will use their purchasing power and expertise to offer custom quotes with competitive pricing and rapid lead times within 15 minutes of receiving any form, so get started today. We are readily available to answer your calls or emails, and we look forward to hearing from you.


August 3, 2022

Recent Twitter Posts

ASAP Semiconductor's Certifications and Memberships

Thank You for Visiting.

Don’t forget That You Can Always Get an Instant RFQ Within Fifteen Minutes Or Less. All You Need to Do Is Fill Out the form On Our Home Page, and You Can Get Started today.

Request for Quote

We use cookies to ensure that we give you the best experience on our website. If you continue to use this site we will assume that you are happy with it.