Abstract: A device for detecting and discriminating operating faults in an electrical power supply circuit comprises a control circuit integrating a power transistor controlling the electric supply of a load, detectors and a logic circuit connected to a computer by two lines, an input/output control line and a selection line. The computer selectively and successively controls, by specific combinations of logic signals applied on the input/output control line and the selection line, several logic sub-circuits for the detection and identification of operating faults in the power supply circuit of the load, such faults being permanent control, short circuit and open circuit, the circuit in return imposing on the input/output control line logic levels representative of the presence of absence of operating faults, during the time intervals in which the computer is configured to read these levels. For a plurality of the power supply circuits, the selection line is common to all such power supply circuits.

Abstract: The device comprises a comparator (3) to diagnose a possible short-circuit of an inductive load (2), the supply to which is controlled by a power transistor (1) of the DMOS type. On blocking of the transistor (1), a high negative voltage appears at the terminals of the load, which is liable to damage the comparator (3). In order to protect the non-inverting input of the comparator, there is connected between said input and the load (2) a junction isolation "vertical" NPN transistor (8) exhibiting a reverse voltge Vebo greater than said negative voltage. The collector of the transistor (8) is connected to the supply +Vbat by the N-type substrate of a "smart" power integrated circuit, the emitter of the transistor (8) being isolated from the substrate by a P-type zone. Application to the control of an inductive load in automobile electronics.

Abstract: The circuit according to the invention controls the supply to an inductive load by a power transistor of the N-channel MOS type, placed on the side of the positive terminal of a supply source delivering a voltage +Vbat. The conduction of the transistor is maintained by means of a gate voltage Vs>+Vbat supplied by a voltage multiplier. On cutting off this voltage, there is blocking of the transistor and discharge of the load, which rapidly develops a high negative voltage. An interconnecting transistor than prevents the return to conduction of the power transistor while, according to the invention, a transistor of the P-channel MOS type isolates the gate of the interconnecting transistor to authorize the application to said gate of the negative voltage developed by the inductive load. The invention has application to the control of actuators for the automobile industry.