Timer-based thermal protection for power components of a switch mode power supply

Patent metadata

Field	Value
Publication number	US-10298040-B2
Application number	US-201615273804-A
Country	US
Kind code	B2
Filing date	Sep 23, 2016
Priority date	Sep 23, 2016
Publication date	May 21, 2019
Grant date	May 21, 2019

Abstract

The maximum time that external components of a switch mode power supply over-conduct is determined by an actual ambient temperature at which the devices are operating before they are turned on. Their operation time is thus extended when temperatures are low and decreased when temperatures are high.

First claim

What is claimed is:

1. A switch-mode power supply comprising:
a transistor, configured to provide current to a load from a battery having an output voltage, the output voltage from the battery changing responsive to load applied to the battery through the transistor, the transistor having an input node, which is coupled to the battery, an output node that is coupled to the load and a control node, wherein signals applied to the control node determine whether the transistor is on and conductive or, off and non-conductive;
a processor having a control input and an output coupled to the control node of the transistor, the processor being configured to switch the transistor on and off and thereby control the transistor to provide current to the load, an output voltage at the output node of the transistor provided to the load being independent of an input voltage at the input node of the transistor from the battery but dependent on an amount of current flowing through the transistor from the battery, the processor additionally configured to shut off the transistor responsive to an inhibit signal received by the processor at the processor's control input;
a thermal protection circuit coupled to the processor's control input, the thermal protection circuit comprising an ambient temperature sensor, a counter and a comparator, the thermal protection circuit being configured to provide a the inhibit signal to the processor responsive to:
an ambient temperature as determined by the ambient temperature sensor;
the output voltage of the battery; and
an amount of time that the transistor is on and providing current to the load.

2. The switch mode power supply of claim 1 , wherein the thermal protection circuit is configured to set a time which the inhibit signal is provided to the processor responsive to the ambient temperature to cause the processor to shut off the transistor.

3. The switch mode power supply of claim 1 , wherein the counter is configured to count up and to one of reset and count down.

4. The switch mode power supply of claim 1 , wherein the counter is a timer.

5. The switch mode power supply of claim 1 , wherein the thermal protection circuit comprises:
a maximum count register,
wherein the comparator is operatively coupled to the counter and the maximum count register, the comparator having an output terminal which is configured to provide the inhibit signal to the processor;
wherein the maximum count register holds a count value which is determined by the ambient temperature.

6. The switch mode power supply of claim 5 , further comprising:
a second comparator having a first input coupled to the input node of the transistor, a second input and an output, wherein the counter has a first input coupled to the output of the second comparator, a second input for receiving an oscillating signal and an output, the output of the counter is coupled to an input of the comparator, the comparator comparing the output of the counter with the count value of the maximum count register.

7. The switch mode power supply of claim 5 , wherein the counter maintains a second count value that is based at least in part upon a voltage at the control input of the transistor, wherein the comparator compares the count value of the maximum count register with the output of the counter.

8. The switch mode power supply of claim 7 , wherein the counter increments or decrements responsive at least in part upon the voltage at the control input of the transistor.

9. The switch mode power supply of claim 1 , wherein the thermal protection circuit comprises a loop counter and wherein the thermal protection circuit is configured to limit the amount of time that the transistor is on by a count limit determined by the loop counter.

10. The switch mode power supply of claim 1 , wherein the processor is formed on a semiconductor die, and wherein the thermal protection circuit comprises a semiconductor device that is also formed on the semiconductor die.

11. A method of protecting external power components of a switch mode power supply from thermal damage, the method comprising:
determining an ambient temperature in real time;
determining a maximum length of time to permit current to flow through the external power components using the ambient temperature;
providing current to a load through the external power components and, starting a timer when a voltage of a battery, to which the external power components are coupled, falls below a predetermined voltage level;
comparing an elapsed time as measured by the timer to the maximum length of time determined from the ambient temperature; and
shutting off current to the load through the external power components when the elapsed time equals or exceeds the maximum length of time determined from the ambient temperature.

12. The method of claim 11 , wherein the step of determining a maximum length of time to permit current to flow through the external power components using the ambient temperature comprises obtaining a maximum length of time from a table of time values, which are indexed in the table by ambient temperature values.

13. The method of claim 11 , wherein the step of determining a maximum length of time to permit current to flow through the external power components using the ambient temperature comprises, evaluating an equation that correlates a maximum length of time to ambient temperatures.

14. The method of claim 11 , wherein the step of determining a maximum length of time to permit current to flow through the external power components using the ambient temperature comprises determining a maximum length of time using a loop counter.

15. A switch-mode power supply comprising:
a transistor configured to provide current to a load from a battery having an output voltage, the output voltage from the battery changing responsive to load applied to the battery through the transistor, the transistor having a first node, which is coupled to the battery, a second node that is coupled to the load and a control node, wherein a voltage applied to the control node at least partly determines whether the transistor is on and conductive or off and non-conductive;
a processor having a control input and an output coupled to the control node of the transistor, the processor being configured to switch the transistor on and off and thereby control the transistor to provide current to the load, the processor additionally configured to shut off the transistor responsive to an inhibit signal received by the processor at the processor's control input;
a thermal protection circuit coupled to the processor's control input, the thermal protection circuit comprising an ambient temperature sensor, a counter and a first comparator, the thermal protection circuit being configured to provide the inhibit signal to the processor responsive to:
an ambient temperature as determined by the ambient temperature sensor;
the battery output voltage; and
the amount of time that the transistor is on and providing current to the load.

16. The switch-mode power supply of claim 15 , wherein the thermal protection circuit further comprises data storage for storing a maximum count value, wherein the first comparator is operatively coupled to an output of the counter and the data storage, the first comparator having an output which generates the inhibit signal.

17. The switch-mode power supply of claim 16 , wherein the ambient temperature sensor is coupled to the data storage such that the maximum count value is based upon an output of the ambient temperature sensor.

18

Assignees

• Continental automotive systems inc

Inventors

• Zarkhin Mikhail
• Fisch Alfons

Classifications

• H02H3/08

  responsive to excess current (responsive to abnormal temperature caused by excess current H02H5/04) · CPC title

• B60L2240/525

  Temperature of converter or components thereof · CPC title

• G05B15/02

  electric · CPC title

• H02H3/243

  for DC systems · CPC title

• H02M1/08

  Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters · CPC title