Thermally optimized demagnetization of inductive loads [power IC load switching]

Switching inductive loads, without free-wheeling diodes, to achieve fast switch-off times, is an important application for integrated smart power circuits. It requires an integrated overvoltage protection and the ability of the integrated circuit to dissipate the energy stored in the inductive load within short periods of time. In this paper, an optimized demagnetization strategy is introduced which allows for switching off large inductive loads quickly without exceeding the critical junction temperature. It is shown that for a given power transistor, the energy capability can be increased by approximately 50% compared to the state-of-the-art switch-off procedure. A circuit implementation is presented which has been implemented on a testchip. Measurement results are shown which demonstrate the advantages of the new approach.