Current limited temperature responsive circuit

Claim 2

A temperature responsive circuit comprising: a temperature sensitive device, a first current source connected in series with the temperature sensitive device for generating a given current, detecting means having an output for providing a voltage signal which varies with the temperature sensed by the temperature sensitive device, a current-limiting arrangement connected to the output of the detecting means, the current limiting arrangement comprising a current mirror having first and second similar transistors with a main current path between first and second electrodes of the second transistor providing an output current of the circuit and a second current source providing a current for the current mirror which is related to said given current when the voltage signal at the output of the detecting means represents a temperature below a critical temperature and providing a current which drops with an increase in temperature beyond the critical temperature to cause the output current of the circuit to fall with an increase in temperature beyond the critical temperature.

Claim 3

A temperature responsive circuit according to claim 1, wherein the first and second transistors each have first and second main electrodes and a control electrode and with the control electrode of the second transistor connected to the first main electrode and the control electrode of the first transistor, and with the first electrode of the second transistor providing an output of the circuit and the second current source connected to the second main electrodes of the first and second transistors, the first main electrode of the first transistor being connected via a resistance to the output of the detecting means for causing a voltage at the control electrodes of the first and second transistors to vary with the output voltage of the detecting means.

Claim 4

A temperature responsive circuit according to claim 1 wherein the temperature sensitive device comprises a first temperature sensitive element having a positive temperature coefficient of resistance and a second temperature sensitive element having a negative temperature coefficient of resistance and with each of the temperature sensitive elements connected in series with the first current source, and wherein the detecting means comprises a comparator for comparing a voltage across the first temperature sensitive element with a voltage across the second temperature sensitive element and for providing at the output of the detecting means said voltage signal and which is related to a difference between the voltages across the first and second temperature sensitive elements.

Claim 5

A temperature responsive circuit according to claim 3, wherein the second temperature sensitive element comprises a bipolar transistor having its base electrode and one of its emitter and collector electrodes connected to a reference voltage supply line and the other one of its collector and emitter electrodes connected to one input of the comparator, and wherein the first temperature sensitive element comprises a resistor connected between the reference voltage supply line and another input of the comparator.

Claim 6

A temperature responsive circuit according to claim 4, wherein the comparator comprises third and fourth similar transistors each having first and second main electrodes and a control electrode and each being connected in series with a respective one of the first and second temperature sensitive elements, the control electrode of the fourth transistor being connected to the second main electrode and the control electrode of the third transistor, and wherein the output of the detecting means comprises the first main electrode of the fourth transistor.

Claim 7

A temperature responsive circuit according to claim 5, wherein the first current source comprises two similar transistors each having first and second main electrodes and a control electrode and each having its main electrodes connected in series with a respective one of the third and fourth transistors, a further transistor similar to the two similar transistors of the first current source and having first and second main electrodes connected in series with a current generator and having a control electrode connected to one of its first and second main electrodes and to the control electrodes of the two similar transistors of the first current source.

Claim 8

A temperature responsive circuit according to claim 1 wherein the second current source comprises two similar transistors each having first and second main electrodes and a control electrode and each having its main electrodes connected in series with a respective one of the first and second transistors, and a further transistor similar to the two similar transistors and having first and second main electrodes connected in series with a current generator and having a control electrode connected to one of its first and second main electrodes and to the control electrodes of the two similar transistors of the second current source.

Claim 9

A temperature responsive circuit according to claim 1 wherein the output of the circuit provides a bias current for limiting the current passing through a power semiconductor device and in that the temperature sensitive device is integrated close to the power semiconductor device.

Claim 10

A temperature responsive circuit according to claim 2 wherein the temperature sensitive device comprises a first temperature sensitive element having a positive temperature coefficient of resistance and a second temperature sensitive element having a negative temperature coefficient of resistance and with each of the temperature sensitive elements connected in series with the first current source, and wherein the detecting means comprises a comparator for comparing a voltage across the first temperature sensitive element with a voltage across the second temperature sensitive element and for providing at the output of the detecting means said voltage signal and which is related to a difference between the voltages across the first and second temperature sensitive elements.

Claim 11

A temperature responsive circuit according to claim 9, wherein the second temperature sensitive element comprises a bipolar transistor having its base electrode and one of its emitter and collector electrodes connected to a reference voltage supply line and the other one of its collector and emitter electrodes connected to one input of the comparator, and wherein the first temperature sensitive element comprises a PTC resistor connected between the reference voltage supply line and another input of the comparator.

Claim 12

A temperature responsive circuit according to claim 10, wherein the comparator comprises third and fourth similar transistors each having first and second main electrodes and a control electrode and each being connected in series with a respective one of the first and second temperature sensitive elements, the control electrode of the fourth transistor being connected to the second main electrode and the control electrode of the third transistor, and wherein the output of the detecting means comprises the first main electrode of the fourth transistor.

Claim 13

A temperature responsive circuit according to claim 3, wherein the comparator comprises third and fourth similar transistors each having first and second main electrodes and a control electrode and each being connected in series with a respective one of the first and second temperature sensitive elements, the control electrode of the fourth transistor being connected to the second main electrode and the control electrode of the third transistor, and wherein the output of the detecting means comprises the first main electrode of the fourth transistor.

Claim 14

A temperature responsive circuit according to claim 12, wherein the first current source comprises two similar transistors each having first and second main electrodes and a control electrode and each having its main electrodes connected in series with a respective one of the third and fourth transistors, a further transistor similar to the two similar transistors of the first current source and having first and second main electrodes connected in series with a current generator and having a control electrode connected to one of its first and second main electrodes and to the control electrodes of the two similar transistors of the first current source.

Claim 15

A temperature responsive circuit according to claim 3 wherein the second current source comprises two similar transistors each having first and second main electrodes and a control electrode and each having its main electrodes connected in series with a respective one of the first and second transistors, and a further transistor similar to the two similar transistors and having first and second main electrodes connected in series with a current generator and having a control electrode connected to one of its first and second main electrodes and to the control electrodes of the two similar transistors of the second current source.

Claim 16

A temperature responsive circuit according to claim 4 wherein the second current source comprises two similar transistors each having first and second main electrodes and a control electrode and each having its main electrodes connected in series with a respective one of the first and second transistors, and a further transistor similar to the two similar transistors and having first and second main electrodes connected in series with a current generator and having a control electrode connected to one of its first and second main electrodes and to the control electrodes of the two similar transistors of the second current source.

Claim 17

A temperature responsive circuit according to claim 15 wherein the output of the circuit provides a bias current for limiting the current passing through a power semiconductor device and in that the temperature sensitive device is integrated close to the power semiconductor device.

Claim 18

A temperature responsive circuit according to claim 3 wherein the output of the circuit provides a bias current for limiting the current passing through a power semiconductor device and in that the temperature sensitive device is integrated close to the power semiconductor device.

Claim 19

A temperature responsive circuit comprising: a temperature sensitive device having first and second current branches including first and second temperature sensitive elements having complementary temperature coefficients thereby to produce first and second temperature-dependent voltages, a first current source having first and second current branches coupled in series with the first and second current branches of the temperature sensitive device to first and second terminals of a source of DC supply voltage, current generator means coupled to said first current source for producing a given current in said first current source, a detection circuit coupled to said temperature sensitive device and responsive to said first and second temperature dependent voltages to produce at its output a voltage signal that varies with the temperature sensed by the temperature sensitive device, and a current limiter circuit coupled to the detection circuit output and comprising; a current mirror circuit having first and second similar transistors, a current output terminal coupled to the second transistor, means coupling the first transistor to said output of the detection circuit, and a second current source coupled to the current mirror circuit to provide a current for the current mirror circuit which is related to said given current when said voltage signal represents a sensed temperature below a critical temperature and further provides a current for the current mirror circuit which decreases for an increase in temperature above the critical temperature whereby an output current in the current output terminal decreases for said increase in temperature above the critical temperature.

Claim 20

A temperature responsive circuit comprising: a temperature sensitive device having first and second current branches including first and second temperature sensitive elements having complementary temperature coefficients thereby to produce first and second temperature-dependent voltages, a first current source having first and second current branches coupled in series with the first and second current branches of the temperature sensitive device to first and second terminals of a source of DC supply voltage, current generator means coupled to said first current source for producing a given current in said first current source, a detection circuit coupled to said temperature sensitive device and responsive to said first and second temperature dependent voltages to produce at its output a voltage signal that varies with the temperature sensed by the temperature sensitive device, and a current limiter circuit coupled to the detection circuit output and comprising; a current mirror circuit having first and second similar transistors, a current output terminal coupled to the second transistor, means coupling the first transistor to said output of the detection circuit, and a second current source coupled to the current mirror circuit to provide a current for the current mirror circuit which is related to said given current when said voltage signal represents a sensed temperature below a critical temperature and further provides a current for the current mirror circuit which decreases for an increase in temperature above the critical temperature whereby an output current in the current output terminal decreases for said increase in temperature above the critical temperature.

Claim 21

A temperature responsive circuit as claimed in claim 18 wherein; said first and second temperature sensitive elements have a positive temperature coefficient and a negative temperature coefficient, respectively, and said second current source is coupled to said current generator means.

Claim 22

A temperature responsive circuit as claimed in claim 18 wherein; said detection circuit comprises third and fourth transistors serially connected in said first and second current branches, respectively, with said first and second temperature sensitive elements, respectively, and said first and second current sources form second and third current mirror circuits with said current generator means.