Techniques minimize switching-device failures in inductive circuits

All electronic circuits generally use inductive elements, such as transformers, coils, or relays, and some applications, such as stepper motors, also have inductive loads. Unfortunately, the failure of switching devices in inductive circuits is a frequent problem and causes system failure. Switchingtransistor and MOSFET failure is common in motor drivers, switched-mode power supplies, and similar electronic systems. The causes for the switch failures can be intrinsic or extrinsic. In an intrinsic failure, the device itself may be faulty, it may have undergone degradation, or it may have a latent defect that initial device testing did not detect. Extrinsic causes of failure include simply misapplying the device or making it operate beyond its safe-operating-area characteristic during normal operation of the system. In this case, the device is bound to fail due to excessive stress. The stress can be electrical (Figure 1) or thermal overstress.