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A HYSTERESIS AND LEVEL SHIFT CIRCUIT FOR AUTOMOTIVE IGNITION COIL DRIVERS

IP.com Disclosure Number: IPCOM000008322D
Original Publication Date: 1997-Sep-01
Included in the Prior Art Database: 2002-Jun-05
Document File: 2 page(s) / 89K

Publishing Venue

Motorola

Related People

2. John Shen: AUTHOR [+2]

Abstract

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.

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MOTOROLA Technical Developments

A HYSTERESIS AND LEVEL SHIFT CIRCUIT FOR AUTOMOTIVE IGNITION COIL DRIVERS

by 2. John Shen and Stephen P. Robb

  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.

  A monolithic input stage circuit is described which provides hysteresis input and level shift functions. Figure I is a generalized circuit diagram which includes the input stage circuit, the main IGBT, other circuit function blocks, such as gate drive and/or protective circuits, and parasitic resistance and inductance. Note that the monolithic circuits exclusively consist of n-channel MOSFETs, poly-Si diodes and resistors, which can be fabricated along with the main IGBT without requiring major

process changes. The input stage circuit has a power supply node Vdd, two EST input signal nodes

EST-HI and EST-LO, and two output signal nodes connected to the gate drive circuit and emitter of the IGBT respe...