Apparatus for controlling the operating current of electromagnetic devices

In an apparatus for controlling solely the actuation current supplied to an electrical device, in particular to one or more electromagnetic fuel injection valves having actuating coils which respond to fuel injection control pulses supplied by the fuel injection system of an internal combustion engine, the duration of said pulses being dependent substantially on engine air throughput and engine speed (rpm) and said duration of said pulses determining the amount of fuel admitted by said valves, said apparatus including positive and negative power supply lines;

• an output circuit connected to the actuating coils of the fuel injection valves for providing actuation of said fuel injection valves, said output circuit having a fully conducting or a fully turned off state, said output circuit including:
• a feedback-controlled driver and logic circuit for receiving said fuel injection control pulses from said fuel injection system;
• and
• sensing means for sensing the actual magnitude of the actuation current in the actuating coils of said injection valves and for generating a control variable as a function thereof, the improvement comprising:
• a feedback circuit including:
• a two-point controller circuit connected to said driver and logic circuit and to said sensing means for receiving the control variable from said sensing means;
• and a set-point switching circuit for receiving trigger pulses coincident with said fuel injection control pulses, said set-point switching circuit being connected to said two-point controller circuit for providing an increased set-point signal to said two-point controller circuit at the beginning of each fuel injection control phase, said two-point controller circuit serving to render said output circuit either fully conducting, at least when the beginning of a fuel injection control pulse is received by the feedback-controlled driver and logic circuit, or fully turned-off.