Kickback-limited soft-shutdown circuit for a coil

Abstract

Circuits and methods for controlling a coil current are disclosed. The control utilizes current sources to source/sink charge to/from a capacitance of a switching device to turn the switching device ON/OFF. When turned OFF, the switching device blocks coil current from flowing, which can create a large kickback voltage on the coil. To reduce the large kickback voltage, the capacitance can be discharged slowly by a small discharge current. The disclosed circuits and methods provide a gradual reduction of the coil current at a rate that is slow enough to prevent a spark while minimizing a period for shutdown to prevent overheating. The disclosed systems and methods may be simpler than other approaches because the soft shutdown is no ramp signal is required for the reduction. Instead, a rate of gate capacitance discharge is controlled to maintain the kickback voltage at a particular level.