초록 ▼

A self-protective driver circuit with automatic reset features is provided for a marine electric fuel pump (2, 102) energized by the boat battery (4, 104) as controlled by a series connected semiconductor switch (6, 106). A first stage protective subcircuit (28, 128) senses surge current through the

A self-protective driver circuit with automatic reset features is provided for a marine electric fuel pump (2, 102) energized by the boat battery (4, 104) as controlled by a series connected semiconductor switch (6, 106). A first stage protective subcircuit (28, 128) senses surge current through the semiconductor switch at initial turn on with the fuel pump at rest and causes the semiconductor switch to depart from saturated conduction and thus limit the current until the pump starts running and the current decreases to a safer level, to protect the semiconductor switch from excessive current. A second stage protective subcircuit (36, 136) senses a given minimum current flow through the semiconductor switch in combination with abnormally high conduction voltage across the semiconductor switch, indicating a stalled or electrically shorted fuel pump, and in conjunction with a timer (58, 164) quickly turns OFF the semiconductor switch for a given time interval for cooling-off purposes, after which the semiconductor switch is automatically turned back ON, with the cycle repeating as necessary. A third stage protective subcircuit (82, 184) senses long term increased current flow through the semiconductor switch indicating a deteriorating condition in the fuel pump, and in conjunction with the timer turns OFF the semiconductor switch for the given time interval after which the semiconductor switch is automatically turned back ON to re-energize the fuel pump, the cycle repeating as necessary.

대표청구항 ▼

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 p

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 comparator having inverting and noninverting inputs, one of said inputs being connected to said transistor, the other of said inputs being connected to said semiconductor switch means, said comparator having an output disabling gate drive for said semiconductor switch means in response to a given overvoltage across said semiconductor switch means causing conduction of said transistor as sensed by said one input of said comparator means if there is said minimum current flow through said semiconductor switch means as sensed by said other input of said comparator means; said overcurrent sensor means comprises a second comparator having inverting and non-inverting inputs, one of said inputs of said second comparator being connected to said capacitor, the other of said inputs of said second comparator being connected to a given reference, said second comparator having an output disabling said gate drive for said semiconductor switch means in response to long term increased current flow through said semiconductor switch means charging said capacitor above said given threshold.