Self-protective fuel pump driver circuit

A self-protective circuit including a fuel pump energized by a source of electrical potential, comprising semiconductor switch means in series with said fuel pump and said source of electrical potential, said semiconductor switch means having an ON state conducting current and completing a current path from said source of electrical potential through said fuel pump to energize said fuel pump, said semiconductor switch means having an OFF state blocking current to de-energize said fuel pump, and self-protective subcircuit means sensing abnormal conditions of voltage and current or current alone in said semiconductor switch means indicating a probable faulty condition in said fuel pump and turning OFF said semiconductor switch means to de-energize said fuel pump for a cooling-off interval for said semiconductor switch means, and automatically turning said semiconductor switch means back ON after said cooling-off interval to re-energize said fuel pump, without manual intervention by the operator, wherein said self-protective subcircuit means includes overvoltage sensor means sensing abnormal voltage across said semiconductor switch means while current is flowing therethrough, and overcurrent sensor means sensing abnormal current flow through said semiconductor switch means, and wherein;

• said overvoltage sensor means comprises a transistor having base drive voltage developed across said semiconductor switch means to bias said transistor into conduction, and means sensing current flow through said semiconductor switch means and operatively coupled to said transistor such that if the sensed current flow through said semiconductor switch means is above a given minimum current flow then conduction of said transistor turns OFF said semiconductor switch means;
• said overcurrent sensor means comprises a capacitor charged by current through said semiconductor switch means such that if said capacitor is charged above a given threshold voltage said overcurrent sensor means turns OFF said semiconductor switch means;
• said overvoltage sensor means comprises a second transistor base driven into conduction by conduction of said first mentioned transistor, and a third transistor base driven into conduction by said minimum current flow through said semiconductor switch means, said second and third transistors being connected in series and completing a circuit to disable gate drive for said semiconductor switch means;
• said overcurrent sensor means comprises a fourth transistor base driven into conduction by said capacitor charged above said given threshold, conduction of said fourth transistor completing a circuit to disable said gate drive for said semiconductor switch means;

A self-protective circuit including a fuel pump energized by a source of electrical potential, comprising:

• semiconductor switch means in series with said fuel pump and said source of electrical potential, said semiconductor switch means having an ON state conducting current and completing a current path from said source of electrical potential through said fuel pump to energize said fuel pump, said semiconductor switch means having an OFF state blocking current flow to de-energize said fuel pump, said semiconductor switch means has a pair of main terminals connected in series with said fuel pump and said source of electrical potential and a gate terminal for applying a gate drive bias to turn ON said semiconductor switch means;
• overcurrent sensor means sensing initial surge current through said semiconductor switch means at initial turn-on of said semiconductor switch means, and decreasing the conductivity of said semiconductor switch means to limit said surge current to a given maximum level, to protect said semiconductor switch means from excessive current density said overcurrent sensor means comprises a current sensing resistor connected in series with said main terminals of said semiconductor switch means, and a transistor having base drive voltage developed across said current sensing resistor to bias said transistor into conduction, said transistor being connected to said gate terminal of said semiconductor switch means such that conduction of said transistor lowers said gate drive bias for said semiconductor switch means;
• overvoltage and minimum current flow sensor means sensing a given minimum current flow through said semiconductor switch means in combination with abnormal voltage across said semiconductor switch means indicating a probable faulty condition in said fuel pump and turning OFF said semiconductor switch means to de-energize said fuel pump to provide a cooling-off interval for said semiconductor switch means and automatically turning said semiconductor switch means back ON after said cooling-off interval to re-energize said fuel pump, all without manual intervention by the operator, said overvoltage and minimum current flow sensor means comprises a second transistor having base drive voltage developed across said semiconductor switch means to bias said second transistor into conduction, and means sensing current flow through said semiconductor switch means and operatively coupled to said second transistor such that if the sensed current flow through said semiconductor switch means is above said minimum current flow then conduction of said second transistor turns OFF said semiconductor switch means;
• timer means triggered by conduction of said second transistor if said sensed current flow through said semiconductor switch means is above said minimum current flow, said timer means disabling said gate drive for said semiconductor switch means for a set time interval, after which said semiconductor switch means is turned back ON.

A self-protective circuit including a fuel pump energized by a source of electrical potential, comprising:

• semiconductor switch means in series with said fuel pump and said source of electrical potential, said semiconductor switch means having an ON state conducting current and completing a current path from said source of electrical potential through said fuel pump to energize said fuel pump, said semiconductor switch means having an OFF state blocking current flow to de-energize said fuel pump, said semiconductor switch means has a pair of main terminals connected in series with said fuel pump and said source of electrical potential and has a gate terminal for applying gate drive bias to turn ON said semiconductor switch means;
• a first stage protective subcircuit sensing the initial surge current through said semiconductor switch means at turn-on of said semiconductor switch means, and decreasing the conductivity of said semiconductor switch means to limit said surge current to a given maximum level, to protect said semiconductor switch means from excessive current density, said first stage protective subcircuit comprises a current sensing resistor connected in series with said main terminals of said semiconductor switch means, and a transistor having base drive voltage developed across said current sensing resistor to bias said transistor into conduction, said transistor being connected to said gate terminal of said semiconductor switch means such that conduction of said transistor lowers said gate drive bias for said semiconductor switch means;
• a second stage protective subcircuit sensing current exceeding a given minimum current flow through said semiconductor switch means and an overvoltage across said semiconductor switch means indicating a probable faulty condition in said fuel pump, and turning OFF said semiconductor switch means, said second stage protective subcircuit comprises a second transistor having base drive voltage developed across said semiconductor switch means to bias said second transistor into conduction, and means sensing current flow through said semiconductor switch means and operatively coupled to said second transistor such that if the sensed current flow through said semiconductor switch means is above said minimum current flow then conduction of said second transistor turns OFF said semiconductor switch means;
• a third stage protective subcircuit sensing long term increased current flow through said semiconductor switch means indicating a probable deteriorating condition in said fuel pump, and turning OFF said semiconductor switch means,
• said third stage protective subcircuit comprises a capacitor charged by current through said semiconductor switch means such that if said capacitor is charged above a given threshold voltage it turns OFF said semiconductor switch means;
• said second and third protective subcircuits turn OFF said semiconductor switch means for a given cooling-off interval, after which said semiconductor switch means is automatically turned back ON.