Ignition control circuit providing temperature and battery voltage compensated coil current control

Abstract

An automotive ignition system (50) includes a control circuit (52) operable to drive a coil current switching device (24) connected between an ignition coil (30) referenced at battery voltage (VBATT) and a sense resistor (RS) referenced at ground potential. The control circuit (52) includes a drive circuit (20) and voltage trip circuit (54) defining a reference voltage (VTH) for comparison with a sense voltage (VS) developed across the sense resistor (RS) due to increasing coil current (IC) through the ignition coil (30). As the sense voltage (VS) increases to the reference voltage (VTH), the voltage trip circuit (54) produces a trip voltage signal (VTRIP) to which the drive circuit (20) is responsive to deactivate the coil current switching device (24). The voltage trip circuit (54) is configured such that the reference voltage (VTH) is temperature and battery voltage, and optionally engine speed, dependent. The trip voltage signal (VTRIP) thus carries this same dependency so that ignition coil charging time may be. optimally controlled under varying temperature, battery voltage, and optionally engine speed, conditions.

Dependencies are inferred from the claim text.