A HYSTERESIS AND LEVEL SHIFT CIRCUIT FOR AUTOMOTIVE IGNITION COIL DRIVERS
Original Publication Date: 1997-Sep-01
Included in the Prior Art Database: 2002-Jun-05
Semiconductor power devices, such as Insulated Gate Bipolar Transistors (IGBT), have been used as automotive ignition coil drivers for years. It is advantageous for an ignition IGBT to have a monolithic hysteresis input stage to receive Electronic Spark Timing (EST) signals. The hysteresis input circuit prevents an IGBT from being falsely triggered by noise signals. Furthermore, the emitter of an IGBT normally has a potential difference from system ground or the EST signal ground (EST-LO ). This is due to the parasttic resistance and inductance of the cable between emitter of the IGBT and the ground terminal of a battery. Since current flow through an IGBT is directly controlled by the voltage between the gate and emitter of the IGBT, the monolithic input stage circuit therefore needs to shift the ground level of EST signals.