Development of a High-Pressure Injector Driving Circuit for Controlling the Air-Fuel Ratio of GDI Engines

An electric driving circuit for the high-pressure (H.P.) injector is required to be designed to be capable of rapid response and precise air-fuel ratio control for GDI engines. In this study, a three-stage power MOSFETs driving circuit for the H.P. injector is designed and tested to verify its feasibility. The experiments for the fuel injection quantities of the H.P. injector are conducted under the conditions of 60-100 bar fuel pressures, 1200~2000μs injecting pulse durations and DC 40~70V executing supply voltages. Next, PWM control is introduced to the last pulse holding current in the three-stage power MOSFETs driving circuit for the rapid response to turn off the H.P. injector. Also, the measured data of the H.P. injector fed by the three-stage MOSFETs driving circuit are defined as the fuel injection curves. The coefficients of polynomial equations can be determined from the fuel injection curves by the Polynomial Curve Fitting (PCF) method and can be implemented in the developed ECU. The ECU demonstrates the ability to control the fuel injection quantities and injection timing rapidly and precisely.