Claims
- 1. A semiconductor switch comprising a power transistor and a temperature sensor integrated therewith for providing a control signal to switch off the power transistor when the sensor reaches a predetermined thermal condition;
- said power transistor being an insulated gate field effect transistor formed by a semiconductor body (10) having therein a first region (13) of a first conductivity type adjacent a surface of said body and a plurality of device cells (11) in said body, each device cell (11) comprising
- a second region (32) within said first region (13) and which is of a second conductivity type opposite to said first conductivity type;
- a third region (33) within the second region (32) and which is of said first conductivity type; and
- an insulated gate (34) overlying a conduction channel (35) formed thereby in said second region (32) for providing a gatable conductive path between the third region (33) and the first region (13);
- said temperature sensor comprising a thermally responsive semiconductor device formed by a plurality of further device cells (11') within the semiconductor body (10), each said further device cell (11') comprising
- a further second region (32') within said first region (13) and which is of said second conductivity type;
- a further third region (33') within the further second region (32') and which is of said first conductivity type; and
- a further insulated gate (34') overlying a conduction channel (35') formed thereby within the further second region (32'), said further gate (34') being electrically connected to either of said third and further third regions (33, 33');
- said further device cells constituting a parasitic bipolar transistor having a leakage current which varies with temperature and from which the temperature sensor derives a control signal for switching off the power transistor when said predetermined thermal condition is reached.
- 2. A semiconductor switch according to claim 1, wherein the third region (33') of each further device cell (11') is electrically connected to the second region (32') thereof.
- 3. A semiconductor switch according to claim 1, wherein at least the second regions (32) of the power transistor each have therein a more highly doped central area.
- 4. A semiconductor switch according to claim 1, wherein the further device cells of the temperature sensor are provided adjacent the periphery of the power (semiconductor device) transistor.
- 5. A semiconductor switch according to claim 1, wherein the further device cells of the temperature sensor are provided amongst the device cells of the power (semiconductor device) transistor.
- 6. A semiconductor switch according to claim 1, wherein the temperature sensor further comprises: a second thermally responsive Semiconductor device similar to the first-named thermally responsive semiconductor device, one of the two thermally responsive semiconductor devices being provided adjacent and the other remote from the power transistor; and means responsive to the leakage currents of the two thermally responsive devices for deriving said control signal to switch off the power transistor when the difference in the temperatures sensed by the two thermally responsive semiconductor devices exceeds a predetermined value.
- 7. A semiconductor switch according to claim 2, wherein at least the second regions (32) of the power transistor each have therein a more highly doped central area.
- 8. A semiconductor switch according to claim 2, wherein the further device cells of the temperature sensor are provided adjacent the periphery of the power transistor.
- 9. A semiconductor switch according to claim 3, wherein the further device cells of the temperature sensor are provided adjacent the periphery of the power transistor.
- 10. A semiconductor switch according to claim 2, wherein the further device cells of the temperature sensor are provided amongst the device cells of the power transistor.
- 11. A semiconductor switch according to claim 2, wherein the temperature sensor further comprises: a second thermally responsive semiconductor device similar to the first-named thermally responsive semiconductor device, one of the two thermally responsive semiconductor devices being provided adjacent and the other remote from the power transistor; and means responsive to the leakage currents of the two thermally responsive devices for deriving said control signal to switch off the power transistor when the difference in the temperatures sensed by the two thermally responsive semiconductor devices exceeds a predetermined value.
Priority Claims (1)
Number |
Date |
Country |
Kind |
9206058 |
Mar 1992 |
GBX |
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Parent Case Info
This is a continuation of application Ser. No. 08/015,697, filed Feb. 9, 1993 abandoned.
US Referenced Citations (7)
Continuations (1)
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Number |
Date |
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Parent |
15697 |
Feb 1993 |
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