Shunt means for protecting a power supply against back emf

Claim 2

A protective circuit for protecting a unidirectional power supply from inverse-polarity voltages origInating in a load connected to the power supply, said circuit comprising: a discharge circuit, connected across the input terminals of the load, said discharge circuit including, in series, a signalcontrolled gate device actuatable from a normal nonconductive condition to a conductive condition in response to an applied signal; sensing means, connected in circuit with the load, for developing a control signal in response to an inverse-polarity voltage in the load circuit that exceeds the instantaneous forward-polarity voltage from the power supply; said sensing means comprising a first unidirectionally conductive device connected in series with the power supply and the load and a sensing impedance connected in parallel with said unidirectionally conductive device; a shunt impedance connected across said power supply; and means for applying the control signal to the gate device in the discharge circuit to actuate the gate device to its conductive condition and thereby prevent application of an inversepolarity current to the power supply.

Claim 3

A protective circuit for a unidirectional power supply, according to claim 1, and further comprising an additional unidirectionally conductive device, connected in series with said sensing impedance, with a polarity to preclude current flow through said sensing impedance in the direction of current flow through said first unidirectionally conductive device.

Claim 4

A protective circuit for a unidirectional power supply, according to claim 1, in which said shunt impedance comprises a discharge resistance and another resistance connected in series with each other from the positive power supply terminal to the negative power supply terminal, and in which said gate device is a signal-controlled semiconductor device having an anode connected to the common junction of said two resistances, a cathode connected to one terminal of said sensing impedance, and a gate electrode connected to another terminal on said sensing impedance.

Claim 5

In combination with a load connected to a rectifier system serving as a direct current power supply, circuit means nonresponsive to a first voltage corresponding to the output voltage of the power supply, but, responsive to a second voltage corresponding substantially to an inverse polarity voltage which may be induced in the load, said second voltage having an amplitude greater than said first voltage and smaller than the inverse voltage characteristic of said power supply, said circuit means comprising, in combination: a unidirectionally conductive device connected in the load circuit and having an anode connected to a first terminal of the load and a cathode connected to the negative terminal of the power supply; a sensing resistance having its terminals connected to the anode and cathode, respectively, of said unidirectionally conductive device; a signal-controlled semiconductor gate device having an anode connected to a juncture of the positive terminal of the power supply and a second terminal of the connected load, having a cathode connected to the anode of said unidirectionally conductive device, and having a gate electrode connected to said sensing resistance; and shunt resistance means having one terminal connected to the anode of said gate device and having a second terminal connected to the cathode of said unidirectionally conductive device.

Claim 6

In combination with a load connected to a rectifier system serving as a direct current power supply, circuit means nonresponsive to a first voltage corresponding to the output voltage of the power supply, but, responsive to a second voltage corresponding substantially to an inverse polarity voltage which may be induced in the load, said second voltage having an amplitude greater than said first voltage and smaller than the inverse voltage characteristic of said power supply, said circuit means comprising, in combination: a unidirectionally conductive device connected in the load circuit and having an anode connected to a first terminal of the load and a cathode connected to the negative terminal of the power supply; a sensing resistance having its terminals connected to the anode and cathode, respectively, of said unidirectionally conductive device; a signal-controlled semiconductor gate device having an anode connected to a juncture of the positive terminal of the power supply and a second terminal of the connected load, having a cathode connected to the anode of said unidirectionally conductive device, and having a gate electrode connected to said sensing resistance; and shunt resistance means having one terminal connected to the anode of said gate device and having a second terminal connected to the cathode of said unidirectionally conductive device.

Claim 7

In a circuit constructed in accordance with claim 4, a discharge resistance connected in series between the anode of the gate device and the positive terminal of the power supply.

Claim 8

A voltage-responsive circuit for protecting a rectifier system from harmful inverse polarity voltages emanating from a load connected to the rectifier system, said circuit comprising: a normally open discharge path connected across the input terminals of said load, said discharge path including a signal-controlled solid-state switching device and operable to close said discharge path upon application of a predetermined signal Current to a gate terminal of the said controlled switching device from an inverse voltage related source of gate current comprising a polarity-responsive sensing circuit including a diode serially connected in forward bias relation between the load and the rectifier system, a sensing resistance connected in shunt relation to said diode, and a shunt resistance connected in shunt relation to the output terminals of said rectifier system and dimensioned and arranged to cooperate with said diode and said sensing resistance to provide a predetermined gate signal voltage across said sensing resistance to cause said switching device to conduct contingent upon occurrence of an excess of inverse voltage over the instantaneous value of forward voltage.

Claim 9

A voltage-responsive circuit for protecting a rectifier system from harmful inverse polarity voltages emanating from a load connected to the rectifier system, said circuit comprising: a normally open discharge path connected across the input terminals of said load, said discharge path including a signal-controlled solid-state switching device and operable to close said discharge path upon application of a predetermined signal Current to a gate terminal of the said controlled switching device from an inverse voltage related source of gate current comprising a polarity-responsive sensing circuit including a diode serially connected in forward bias relation between the load and the rectifier system, a sensing resistance connected in shunt relation to said diode, and a shunt resistance connected in shunt relation to the output terminals of said rectifier system and dimensioned and arranged to cooperate with said diode and said sensing resistance to provide a predetermined gate signal voltage across said sensing resistance to cause said switching device to conduct contingent upon occurrence of an excess of inverse voltage over the instantaneous value of forward voltage.

Claim 10

A voltage-responsive protective circuit as defined in claim 6 and further comprising a current-limiting device serially connected into said discharge path.