Ionization Current Detection for Homogeneous Charge Compression Ignition (HCCI) on Dual Mode Engines Using a Compact Flyback Circuit

This work discusses the detection of ionization current for Homogeneous Charge Compression Ignition (HCCI) on dual mode engines using a compact and versatile flyback circuit. Since spark plugs come already incorporated in the engines, they are commonly used for sensing the ionization current to monitor Spark Ionization (SI) and HCCI systems. The main challenge of this work was to propose a compact and versatile flyback circuit coupled to an ion measuring stage to monitor the ionization current to control HCCI systems. For the experimental validation of the proposed flyback circuit, the spark plug was implemented with the aid of a metallic needle positioned at different distances from a ground plane by means of a micrometer screw in order to vary the ionization current in the range of 1μA to 2mA. As a result, besides being compact, the proposed flyback circuit was improved with a low pass RC filter at its output, which meant a peak-to-peak output voltage ripple below 1.5% in relation to the maximum DC output voltage controlled in the range of 200 to 700V.