Current dependent thermal shutdown

Patent metadata

Field	Value
Publication number	US-10490995-B2
Application number	US-201715674545-A
Country	US
Kind code	B2
Filing date	Aug 11, 2017
Priority date	Aug 11, 2017
Publication date	Nov 26, 2019
Grant date	Nov 26, 2019

Abstract

According to an example, a device comprises a pass element and a controller. The controller is configured to receive a measurement of a current through the pass element. Based on the measurement of the current, the controller is configured to select a thermal shutdown threshold. The controller is further configured to turn off the pass element based on a determination that a temperature of the pass element is greater than the thermal shutdown threshold.

First claim

What is claimed is:

1. A device comprising:
a first pass element; and
a controller configured to:
receive a measurement of a current through the first pass element;
select, based on the measurement of the current, a thermal shutdown threshold; and
turn off the first pass element based on a determination that a first temperature of the first pass element is greater than the thermal shutdown threshold.

2. The device of claim 1 , further comprising:
a substrate having the first pass element arranged thereon; and
a first temperature sensor arranged on the substrate and configured to output a measurement of the first temperature to the controller, wherein the determination that the first temperature is greater than the thermal shutdown threshold is based on the measurement of the first temperature.

3. The device of claim 2 , wherein the controller is configured to select the thermal shutdown threshold from a first temperature level in case the measurement of the current through the first pass element is greater than or equal to a predetermined current threshold, and a second temperature level in case the measurement of the current through the first pass element is less than the predetermined current threshold.

4. The device of claim 3 , wherein the predetermined current threshold is based on a maximum allowable current for which the first pass element can heat to a second temperature greater than or equal to a specified thermal limit due to self-heating.

5. The device of claim 3 , wherein the first temperature level is lower than the second temperature level.

6. The device of claim 3 , further comprising:
a second pass element arranged on the substrate; and
a second temperature sensor arranged on the substrate, wherein a difference between the first temperature level and the second temperature level is based on a specified maximum mismatch error between the first and second temperature sensors.

7. The device of claim 6 , wherein the first temperature sensor is arranged within a first predetermined distance of the first pass element, and the second temperature sensor is arranged within a second predetermined distance of the second pass element.

8. The device of claim 1 , wherein the controller is further configured to receive an indication of a voltage drop across the first pass element and to select the thermal shutdown threshold based further on the indication of the voltage drop across the first pass element.

9. The device of claim 8 , wherein the controller is further configured to:
estimate a power dissipation of the first pass element based on the measurement of the current through the first pass element and the indication of the voltage drop across the first pass element; and
select the thermal shutdown threshold based on the estimate of the power dissipation of the first pass element.

10. The device of claim 8 , wherein the indication of the voltage drop across the first pass element comprises a measurement of a voltage at an output of the first pass element; and wherein the device further comprises a voltage sense subcircuit configured to measure the voltage at the output of the first pass element and output the measurement of the voltage to the controller.

11. The device of claim 1 , further comprising:
a current sense subcircuit configured to measure the current through the first pass element and output the measurement of the current to the controller.

12. The device of claim 11 , wherein the first pass element comprises a power transistor comprising a drain, a gate and a source, and the current sense subcircuit comprises a sensing transistor comprising a drain, a gate and a source, the source of the power transistor coupled to the source of the sensing transistor, the gate of the power transistor coupled to the gate of the sensing transistor, the drain of the power transistor configured to output the current through the first pass element and the drain of the sensing transistor configured to output the measurement of the current through the first pass element.

13. The device of claim 11 , wherein the current sense subcircuit includes a resistor in series with the first pass element.

14. The device of claim 1 , wherein the current through the first pass element is pulsed, and the measurement of the current represents an average of the current.

15. The device of claim 1 , wherein the current through the first pass element is a positive current flowing out of the first pass element.

16. A device comprising:
a pass element;
a controller configured to receive a measurement of a current through the pass element, the controller comprising:
means for selecting, based on the measurement of the current, a thermal shutdown threshold; and
means for turning off the pass element based on a determination that a temperature of the pass element is greater than the thermal shutdown threshold.

17. The device of claim 16 , further comprising:
a substrate having the pass element arranged thereon; and
a first temperature sensor arranged on the substrate and configured to output a measurement of the temperature to the controller, wherein the determination that the first temperature is greater than the thermal shutdown threshold is based on the measurement of the temperature.

18. The device of claim 17 , wherein the controller further comprises:
means for selecting the thermal shutdown threshold from a first temperature level in case the measurement of the current through the pass element is greater than or equal to a predetermined current threshold, and a second temperature level in case the measurement of the current through the pass element is less than the predetermined current threshold.

19. A method comprising:
turning on a pass element;
selecting a thermal shutdown threshold to turn off the pass element at a first temperature threshold;
measuring a current through the pass element; and
switching the thermal shutdown threshold to a second temperature threshold, based on the measurement of the current through the pass element.

20. The method of claim 19 , wherein the first temperature threshold is higher than the second temperature threshold, the method further comprising:
determining, based on the measurement of the current through the pass element, that the current is greater than or equal to a current threshold; and
switching the thermal shutdown threshold to the second temperature threshold based on the determination.

21. The method of claim 20 , further comprising:
determining, based on a measurement of a temperature from a temperature sensor, that the temperature is greater than or equal to the thermal shutdown threshold; and
turning off the pass element.

22. The method of claim 19 , wherein the first temperature threshold is lower than the second temperature threshold, the method further comprising:
switching the thermal shutdown threshold to the second temperature threshold based on a determination that the current through the pass element is less than a current threshold.

Assignees

• Infineon Technologies Ag

Inventors

• Stanculescu Sergiu
• Simion Alexandru

Classifications

• H02H5/044

  using a semiconductor device to sense the temperature · CPC title

• H02H1/0007

  concerning the detecting means (in general G01R or other subclasses of G01; reed switches H01H71/2445) · CPC title

• H02H3/085

  making use of a thermal sensor, e.g. thermistor, heated by the excess current (also responsive to the temperature of the protected device H02H5/041, thermal images H02H6/00) · CPC title

• H02H5/041 Primary

  additionally responsive to excess current (H02H5/048 takes precedence) · CPC title

• G01R19/165

  Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values · CPC title