초록 ▼

A biasing circuit for an ion current measurement system draws power from a primary side of the ignition coil, and applies a positive polarity bias voltage to a low voltage side of a secondary winding of the ignition coil. The biasing circuit includes a silicon-controlled rectifier (SCR) which has an

A biasing circuit for an ion current measurement system draws power from a primary side of the ignition coil, and applies a positive polarity bias voltage to a low voltage side of a secondary winding of the ignition coil. The biasing circuit includes a silicon-controlled rectifier (SCR) which has an on state for carrying spark current during a spark interval of operation, and further includes an off state which prevents the stored biasing voltage on a capacitor from being shunted to ground, thereby allowing ion current sensing through the low voltage side of the secondary winding. The low on-state voltage drop of the SCR during conduction of spark current minimizes losses of spark energy.

대표청구항 ▼

[ What is claimed is:] [1.] An apparatus for detecting a combustion event in a cylinder of an internal combustion engine having a spark plug proximate said cylinder, said apparatus comprising:an ignition coil having a primary winding and a secondary winding, said primary winding having a first end c

[ What is claimed is:] [1.] An apparatus for detecting a combustion event in a cylinder of an internal combustion engine having a spark plug proximate said cylinder, said apparatus comprising:an ignition coil having a primary winding and a secondary winding, said primary winding having a first end coupled to a power supply, said secondary winding having a first end coupled to said spark plug;a switch coupled to a second end of said primary winding opposite said first end, said switch being configured to cause a primary current to flow through said primary winding;a biasing circuit coupled to said second end of said primary winding and said second end of said secondary winding and configured to bias said spark plug with a bias voltage for producing an ion current indicative of the combustion event, said biasing circuit including a silicon-controlled rectifier (SCR) having an anode coupled to said second end of said secondary winding and configured to conduct a spark current through said secondary winding when an ignition voltage at said anode of said SCR reaches a predetermined level.