Module-integrated GMR-based current sensing for closed loop control of a motor drive

Current sensor integration in commercial power semiconductor modules is generally based on shunt resistance methods. The resulting losses and lack of galvanic isolation present opportunities for improvement. This paper describes the integration of sub-millimeter sized giant magnetoresistive (GMR) point field detectors (PFDs) into commercial IGBT modules to provide nearly-lossless, galvanically isolated current sensing capabilities. The IGBT modules are installed into a three-phase inverter motor drive, and the GMR-based integrated current sensors are used for closed-loop current control in a field oriented induction motor drive. Finite element analysis (FEA) of the module interconnect structures is used to determine detector locations offering the highest possible bandwidth current measurements. Additional PFDs are used to decouple rotating magnetic field disturbances or bias fields from permanent magnets. The same GMR PFDs are also used to provide temperature measurements that are used to decouple the effects of changing temperature.