Patents Represented by Attorney Chein-Hwa Tsao CH Emily LLC
  • Patent number: 7999600
    Abstract: A circuit for limiting di/dt caused by a main switching FET during its turn-off against an inductive switching circuit is proposed. The circuit for limiting di/dt includes an auxiliary inductor in series with the main switching FET for inducing an auxiliary inductive voltage proportional to di/dt; an auxiliary FET in parallel with the main switching FET; the auxiliary FET gate is connected to produce a gate voltage equal to the auxiliary inductive voltage. When the di/dt tends to exceed a predetermined maximum rate of decrease the auxiliary FET produces an auxiliary current component counteracting further decrease of the di/dt. The main switching FET and the auxiliary FET can be formed from a single die with shared source and drain; the auxiliary inductor can be implemented as a parasitic inductance of an inherently required bonding wire connecting the main switching FET to its device terminal to simplify packaging with reduced cost.
    Type: Grant
    Filed: June 5, 2009
    Date of Patent: August 16, 2011
    Assignee: Alpha and Omega Semiconductor, Inc.
    Inventor: Sanjay Havanur