Electronic spark advance for breakerless ignition systems using phase locked loop techniques

The necessity for a low pollution engine has increased the requirement to control ignition spark advance. Seven engine parameters may need to be measured and be used to control the spark advance. The complexity of mechanical systems to control such spark advance warrants an investigation of electronic control. Electronic spark advance has been investigated with a variety of analog and digital circuits. It now appears that the PLL (Phase Locked Loop) technique offers the most promise in terms of simplicity, cost, and noise immunity. Figure 1 is a basic block diagram of a complete electronic advance ignition system.