Inductive load discharge current recirculation circuit with selectable "fast" and "low" modes

Claim 1

A circuit for recirculating discharge current of an inductive load driven from a supply rail of an electrical supply by means of a switthing power transistor functionally connected between said supply rail and a first terminal of said inductive load, the other terminal of which is grounded, and having a base to which a driving signal generated by a control circuit is fed, capable of permitting recirculation of said discharge current under two different recirculation voltages which is selected for implementing a slow recirculation or a fast recirculation of said discharge current and characterized by comprising a recirculation NPN transistor having an emitter connected to said first terminal of the inductive load, a collector connected to ground and a base connected to the anode of a zener diode, the cathode of which is connected to the cathode of a second diode, the anode of which is connected to said ground; a current source capable of delivering to the base of said NPN recirculation transistor a current sufficient to drive the latter to saturation for implementing a slow recirculation of the discharge current of the inductive load through the recirculation NPN transistor itself at a recirculation voltage which is substantially equal to the saturation voltage of the recirculation transistor; and means for interrupting delivery to the base of the recirculation NPN transistor of said saturating current for implementing a fast recirculation of the discharge current of the inductive load through the NPN recirculation transistor itself at a recirculation voltage which is substantially equal to the sum of the voltage drop across said second diode, the voltage of said zener diode and the baseemitter voltage of said recirculation NPN transistor.