Cooking appliance and method for limiting cooking utensil temperatures using time-to-target criteria

1. A method for operating a cooking appliance, the method comprising:

providing power to the heating source according to a first control mode, the first control mode comprising calculating a time interval t limit for a temperature of a cooking utensil positioned on the heating source to reach a target temperature limit T limit ;

determining whether the time interval t limit to reach the target temperature limit T limit is less than or equal to a predetermined time interval limit t turn _ off and, if so, then

providing power to the heating source according to a second control mode, the second control mode comprising reducing the heating source power to a minimum power level P min and incrementing a timer t off ;

determining whether the timer t off has surpassed a threshold time t thr and, if so, then

providing power to the heating source according to a third control mode,

wherein power is provided to the heating source in the third control mode using a proportional-integral or proportional-integral-derivative control algorithm.

2. The method of claim 1 , wherein the first control mode comprises

providing power to the heating source based on a power level input.

3. The method of claim 1 , wherein a temperature sensor contacts a bottom surface of the cooking utensil to sense the temperature of the cooking utensil.

4. The method of claim 1 , further comprising, if the time interval t limit to reach the target temperature limit T limit is greater than the predetermined time interval limit t turn _ off ,

determining whether the temperature of the cooking utensil is at least equal to the target temperature limit T limit and, if so, then

proceeding to providing power to the heating source according to the second control mode.

5. The method of claim 4 , further comprising, if the temperature of the cooking utensil is less than the target temperature limit T limit ,

continuing to provide power to the heating source according to the first control mode.

6. The method of claim 1 , further comprising, if the time interval t limit to reach the target temperature limit T limit is less than or equal to the predetermined time interval limit t turn _ off ,

determining whether the temperature of the cooking utensil is at least equal to an enabling threshold temperature T thr before proceeding to providing power to the heating source according to the second control mode.

7. The method of claim 1 , further comprising, if the timer t off has not surpassed the threshold time t thr ,

determining whether a temperature of a cooking utensil positioned on the heating source is at least equal to the target temperature limit T limit and, if so, then

proceeding to providing power to the heating source according to the third control mode.

8. The method of claim 7 , further comprising, if the temperature of the cooking utensil is less than the target temperature limit T limit ,

determining whether the temperature of the cooking utensil is less than or equal to a disabling threshold temperature T resume and, if so, then

returning to providing power to the heating source according to the first control mode.

9. The method of claim 1 , further comprising determining whether to transition from the second control mode to the first control mode and, if so, then

returning to providing power to the heating source according to the first control mode.

10. The method of claim 9 , wherein determining whether to transition from the second control mode to the first control mode comprises comparing a temperature of a cooking utensil positioned on the heating source to a disabling threshold temperature T resume .

11. The method of claim 1 , further comprising determining whether to transition from the third control mode to the first control mode and, if so, then

returning to providing power to the heating source according to the first control mode.

12. The method of claim 11 , wherein determining whether to transition from the third control mode to the first control mode comprises comparing a temperature of a cooking utensil positioned on the heating source to a disabling threshold temperature T resume .

13. A cooking appliance, comprising:

a heating source;

a temperature sensor, the temperature sensor positioned to sense the temperature of a bottom surface of a cooking utensil when the cooking utensil is placed on or adjacent to the heating source;

an energy control device for modulating the power provided to the heating source;

a controller, the controller in operative communication with the temperature sensor and the energy control device, the controller configured for

providing power to the heating source according to a first control mode, the first control mode comprising calculating a time interval t limit for a temperature of a cooking utensil positioned on the heating source to reach a target temperature limit T limit ;

determining whether the time interval t limit to reach the target temperature limit T limit is less than or equal to a predetermined time interval limit t turn _ off and, if so, then

providing power to the heating source according to a second control mode, the second control mode comprising reducing the heating source power to a minimum power level P min and incrementing a timer t off ;

determining whether the timer t off has surpassed a threshold time t thr and, if so, then

providing power to the heating source according to a third control mode,

wherein power is provided to the heating source in the third control mode using a proportional-integral or proportional-integral-derivative control algorithm.

14. The cooking appliance of claim 13 , wherein the temperature sensor is a spring-loaded temperature sensor.

15. The cooking appliance of claim 13 , further comprising a shield extending circumferentially around the temperature sensor.

16. A cooking appliance, comprising:

a heating source;

a temperature sensor, the temperature sensor positioned to sense the temperature T sensed of a bottom surface of a cooking utensil when the cooking utensil is placed on or adjacent to the heating source;

an energy control device for modulating the power provided to the heating source;

a controller, the controller in operative communication with the temperature sensor and the energy control device, the controller configured for

providing power to the heating source according to a first control mode, the first control mode comprising calculating a time interval t limit for a temperature of a cooking utensil positioned on the heating source to reach a target temperature limit T limit ;

determining whether the time interval t limit to reach the target temperature limit T limit is less than or equal to a predetermined time interval limit t turn _ off and, if so, then

providing power to the heating source according to a second control mode, the second control mode comprising reducing the heating source power to a minimum power level P min and incrementing a timer t off ;

determining whether the timer t off has surpassed a threshold time t thr and, if so, then

providing power to the heating source according to a third control mode;

comparing the temperature T sensed sensed by the temperature sensor to a disabling threshold temperature T resume to determine if the temperature T sensed of the cooking utensil is less than the disabling threshold temperature T resume and, if so, then

 providing power to the heating source according to the first control mode,

 wherein power is provided to the heating source in the third control mode using a proportional-integral or proportional-integral-derivative control algorithm.

17. The cooking appliance of claim 16 , wherein the controller is further configure for, if the time interval t limit to reach the target temperature limit T limit is greater than the predetermined time interval limit t turn _ off ,

determining whether the temperature of the cooking utensil is at least equal to the target temperature limit T limit and, if so, then proceeding to providing power to the heating source according to the second control mode but, if not, then continuing to provide power to the heating source according to the first control mode.

18. The cooking appliance of claim 16 , wherein the controller is further configured for, if the timer t off has not surpassed the threshold time t thr ,

determining whether a temperature of a cooking utensil positioned on the heating source is at least equal to the target temperature limit T limit and, if so, then proceeding to providing power to the heating source according to the third control mode, but if the temperature of the cooking utensil is less than the target temperature limit T limit ,

determining whether the temperature of the cooking utensil is less than or equal to the disabling threshold temperature T resume and, if so, then

returning to providing power to the heating source according to the first control mode.

19. The cooking appliance of claim 16 , wherein power is provided to the heating source in the third control mode using a proportional-integral control algorithm wherein the power provided to the heating source equals the sum of an integral term I and the product of a proportional gain factor K p and a temperature error T err .

20. The cooking appliance of claim 16 , wherein the time interval t limit is calculated as a difference between the target temperature limit T limit and a current cooking utensil temperature T sensed ( 0 ), divided by a rate of change ΔT of the temperature T sensed sensed by the temperature sensor.