Patent ID: 6157095
Filing Date: 2000-12-05
Classification: H01F

Abstract:
A control circuit for controlling current flow through an inductive load powered by a unipolar power source, comprising:first, second and third electronic switches connected in sequential series between positive and negative terminals of said power source and said second and third switches connected in series between positive and negative terminals of said load;the first switch being connected to allow or block positive voltage therethrough, the second switch being connected to block positive voltage and allow negative voltage therethrough, and the third switch connected to allow or block negative therethrough;said third switch being connected in a subcircuit to develop a negative voltage drop across the load during a discharge condition; anda drive circuit for closing of the said first switch to connect positive voltage from the power source across the load causing an increasing load current, opening of the first switch and closing the third switch to disconnect the power source from the load and short circuit the inductive current, and opening of the third and first switches to direct decaying inductive current through the subcircuit causing a negative voltage across the load, the subcircuit and the third switch together providing a path for current flow resulting in rapid decay of the inductive current;wherein said subcircuit includes a zener diode and a diode connected in series between a gate and a drain of the third switch whereby upon opening of the first and third switches, said third switch is closed by the negative voltage across the subcircuit of the zener diode and the diode and said subcircuit provides a path for rapid decay of the inductive current flow.