ELECTRONIC POWER CONTROL FOR COOKTOP HEATERS

COMMANDE DE PUISSANCE ELECTRONIQUE POUR RONDS DE CUISINIERE

English Abstract

A power control system for an electric cooktop. The power level is set by a knob connected to a potentiometer. Potentiometer information is digitally communicated by a controller over a serial communication bus to a power unit. The power unit communicates power level display information back to the controller over the same serial communication bus. The display information is displayed as numbers on a digital display by the controller. The power unit controls a heating element of the cooktop according to the potentiometer information. A second potentiometer can be added to control a second heating element by operating. as a slave to the first controller. Further, multiple heating elements can be controlled by-a single potentiometer by dividing the angular rotation into.multiple segments or ranges.

French Abstract

Un système de commande de puissance pour une surface de cuisson électrique. Le niveau de puissance est établi par un bouton connecté à un potentiomètre. Les renseignements du potentiomètre sont communiqués numériquement par un organe de commande sur un bus de communication série à une unité de puissance. L'unité de puissance communique les renseignements d'affichage de niveau de puissance à l'organe de commande sur le même bus de communication série. Les renseignements d'affichage sont affichés par des nombres sur un afficheur numérique par l'organe de commande. L'unité de puissance commande un élément chauffant de la surface de cuisson selon les renseignements du potentiomètre. Un deuxième potentiomètre peut être ajouté pour commander un deuxième élément chauffant par un fonctionnement d'esclave par rapport au premier organe de commande. De plus, de multiples éléments chauffants peuvent être commandés par un seul potentiomètre en divisant la rotation angulaire en de multiples segments.

Claims

What is claimed:


1. A power control system for controlling a plurality of heating elements, the
control system
comprising:

a first rotational control input having a first range of angular rotation and
a second range of
angular rotation;

a first heating element; and

a second heating element;

wherein a position of the control input in the first range controls the first
heating element
and a position of the control input in the second range controls the second
heating
element.


2. The control system of claim 1, further comprising a thermal limiter
associated with one of the
first heating element and the second heating element.


3. The control system of claim 1, wherein the position of the control input in
the second range
concurrently controls the first heating element and the second heating
element.


4. The control system of claim 3, wherein the second heating element surrounds
the first
heating element.


5. The control system of claim 1, further comprising a third heating element;
and wherein the
second heating element is a bridge element located between the first heating
element and the
third heating element.


6. The control system of claim 5, further comprising a second rotational
control input having a
first range of angular rotation and a second range of angular rotation;

wherein a position of the second control input in the first range controls the
third heating
element; and

wherein a position of second control input in the second range disables
control by the first
control input and concurrently controls the first heating element, the second
heating
element, and the third heating element.


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7. A power control system for controlling a plurality of heating elements, the
control system
comprising:

a first rotational control input;

a second rotational control input having a first range of angular rotation and
a second range
of angular rotation;

a first heating element;

a second heating element; and

a third heating element;

wherein the second heating element is a bridge element positioned between the
first
element and the third element;

wherein the first control input controls the first heating element;

wherein a position of the second control input in the first range controls the
third heating
element; and

wherein a position of the second control input in the second range causes the
first control
input to concurrently control the first heating element, the second heating
element, and
the third heating element.


8. The control system of claim 7, further comprising a thermal limiter
operatively associated with
at least one of the first heating element, the second heating element, and the
third heating
element.


9. The control system of claim 7, wherein the first rotational control input
has a first range of
angular rotation and a second range of angular rotation; wherein the a
position of the first
control input in the first range controls the first heating element; and
wherein a position of the
first control input in the second range concurrently controls the first
heating element and the
second heating element.


10. The control system of claim 9, wherein the position of the second control
input in the second
range causes each of the position of the first control input in the first
range and the position of
the first control input in the second range to concurrently control the first
heating element, the
second heating element, and the third heating element.


11. The control system of claim 9, wherein the position of the second control
input in the second
range causes a position of the first control input in a full range of the
first control input to

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concurrently control the first heating element, the second heating element,
and the third
heating element.


12. A power control system for an electric heating element, the control system
comprising:

a communication bus;

a controller connected to the communication bus;

a variably resistive device connected to the controller;

a digital display connected to the controller; and

a power unit connected to the communication bus, the power unit having a power
output;

wherein the variably resistive device controls a level of the power output,
and
wherein a relationship between rotation of the variably resistive device and
the level of the
power output is nonlinear.


13. A power control system for an electric heating element, the control system
comprising:

a communication bus;

a controller connected to the communication bus;

a variably resistive device connected to the controller;

a digital display connected to the controller; and

a power unit connected to the communication bus, the power unit having a power
output;
wherein the power unit has a second power output, and wherein:

a position of the variably resistive device in a first range of angular
rotation controls a level
of the first power output; and

a position of the variably resistive device in a second range of angular
rotation controls a
level of the second power output.


14. A power control system for an electric heating element, the control system
comprising:

a communication bus;

a controller connected to the communication bus;

a variably resistive device connected to the controller;

a digital display connected to the controller; and

a power unit connected to the communication bus, the power unit having a first
power,
output and a second power output; wherein:

a position of the variably resistive device in a first range of angular
rotation controls a level
of the first power output; and


19


a position of the variably resistive device in a second range of angular
rotation concurrently
controls the level of the first power output and a level of the second power
output.


15. The control system of claim 14, further comprising:

a second variably resistive device; and

a third power output of the power unit; wherein:

a position of the second variably resistive device in a first range of angular
rotation controls
a level of the third power output; and

a position of the second variably resistive device in a second range of
angular rotation
disables control by the variably resistive device and concurrently controls
the level of
the first power output, the level of the second power output, and the level of
the third
power output.


16. The control system of claim 14, further comprising a heating element
comprising a first
subelement connected to said power output and a second subelement connected to
said
second power output.


17. The control system of claim 16, further comprising a thermal limiter
operatively associated
with the heating element.


18. A power control system for an electric heating element, the control system
comprising:

a communication bus;

a controller connected to the communication bus;

a first variably resistive device connected to the controller;

a digital display connected to the controller; and

a power unit connected to the communication bus, the power unit having a first
power
output, a second power output, and a third power output; and

a second variably resistive device; wherein

the first variably resistive device controls a level of the first power
output;

a position of the second variably resistive device in a first range of angular
rotation controls
a level of the second power output; and

a position of the second variably resistive device in a second range of
angular rotation
causes the first variably resistive device to concurrently control the level
of the first
power output, a level of the second power output and a level of the third
power output.




19. The control system of claim 18, wherein:
a position of the first variably resistive device in a first range of angular
rotation controls the
level of the first power output; and
a position of the first variably resistive device in a second range of angular
rotation controls
the level of the second power output.

20. The control system of claim 19, wherein the position of the first variably
resistive device in
the second range of angular rotation concurrently controls the level of the
first power output
and the level of the second power output.

21. The control system of claim 18, wherein the position of the second
variably resistive device
in the second range of angular rotation causes a position of the first
variably resistive device
in a first range of angular rotation to concurrently control the level of the
first power output, the
level of the second power output and the level of the third power output; and
wherein the
position of the second variably resistive device in the second range of
angular rotation causes
a position of the first variably resistive device in a second range to
concurrently control the
level of the first power output, the level of the second power output and the
level of the third
power output.

22. A power control system for an electric heating element, the control system
comprising:
a communication bus;
a controller connected to the communication bus;
a control input device connected to the controller, the control input device
having a first
control range and a second control range;
a digital display connected to the controller; and
a power unit connected to the communication bus, the power unit having a power
output;
wherein over the first control range, incrementing the control input device by
one power
setting level causes the power unit increase a power output level by a first
step size;
and
wherein over the second control range, incrementing the control input device
by one power
setting level causes the power unit to increase a power output level by a
second step
size being greater than the first step size.


21



23. The power control system of claim 22 wherein the control input device
comprises a variable
resistive device.

24. The power control system of claim 22 wherein the control input device
comprises a
rotational control device.

25. The power control system of claim 22 wherein setting the control input
device within the
second control range results in greater power output than setting the control
input device
within the first control range.

26. A power control system for controlling power to electrical heating
elements, the system
comprising:
a communication bus;
a first power controller for controlling power to a heating element of an
oven, the first power
controller being connected to the communication bus;
a second power controller for controlling power to a heating element of a
cooktop, the
second power controller being connected to the communication bus;
wherein when one of the first power controller and the second power controller
initiates a
lockout condition, the other one of the first power controller and the second
power
controller initiates a corresponding lockout condition in response to a
lockout signal
being provided on the communication bus.

27. The system of claim 26, wherein the lockout condition is initiated for the
purpose of at least
one of:
preventing operation of the second power controller during a self-cleaning
operation of the
first power controller; and
preventing initiation of the self-cleaning operation of the first power
controller during a
heating operation of the second power controller.

28. An electronic cooktop control system comprising:
a cooktop including a first heating element and a second heating element;
an electronic controller operatively connected to the cooktop; and
a rotary position input operatively connected to the electronic controller;

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wherein the electronic controller controls a heating level of the cooktop in a
first manner in
response to rotation of the rotary position input in a first direction,
wherein the electronic controller controls the heating level of the cooktop in
a second
manner in response to rotation of the rotary position input in a second
direction, and
wherein control of the heating level of the cooktop in the first manner
includes controlling
the first heating element without the second heating element, and control of
the heating
level of the cooktop in the second manner includes controlling the second
heating
element.

29. The electronic cooktop control system of claim 28, wherein the control of
the heating level of
the cooktop in the second manner includes controlling the first heating
element concurrently
with the second heating element.

30. The electronic cooktop control system of claim 29, wherein the second
heating element
surrounds the first heating element.

31. The electronic cooktop control system of claim 29, wherein the second
heating element is
adjacent to the first heating element.

32. The electronic cooktop control system of claim 31, wherein the cooktop
further includes a
third heating element adjacent to the second heating element, and wherein the
control of the
heating level of the cooktop in the second manner includes concurrently
controlling the first
heating element, the second heating element and the third element.

33. The electronic cooktop control system of claim 28, wherein the rotation of
the rotary position
input in the first direction includes rotation that progressively increases in
angular magnitude,
and the rotation of the rotary position input in the second direction includes
rotation that
progressively decreases in angular magnitude.

34. The electronic cooktop control system of claim 33, wherein the rotation of
the rotary position
input in the first direction includes rotation of the rotary position input
from a first position
toward a second position that is greater in angular magnitude than the first
position.


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35. The electronic cooktop control system of claim 33, wherein the rotation of
the rotary position
input in the second direction includes rotation of the rotary position input
from a first position
toward a second position that is lesser in angular magnitude than the first
position.

36. The electronic cooktop control system of claim 28, wherein the rotation of
the rotary position
input in the first direction overlaps the rotation of the rotary position
input in the second
direction.

37. The electronic cooktop control system of claim 28, wherein the rotation of
the rotary position
input in the first direction includes rotation in a clockwise fashion from a
zero position, and the
rotation of the rotary position input in the second direction includes
rotation in a counter-
clockwise direction from the zero position.

38. The electronic cooktop control system of claim 37, wherein the zero
position is at a 12
o'clock position of the rotary position input.

39. The electronic cooktop control system of claim 28, wherein the rotary
position input includes
a variable resistive device.

40. The electronic cooktop control system of claim 39, wherein the variable
resistive device is a
potentiometer.

41. The electronic cooktop control system of claim 28, further including a
sensor for sensing a
temperature of the cooktop.

42. The electronic cooktop control system of claim 41, wherein the sensor is
for controlling the
heating level of the cooktop.

43. The electronic cooktop control system of claim 42, wherein the sensor is
connected to the
electronic controller.

44. The electronic cooktop control system of claim 42, wherein the sensor is
connected to the
first heating element.


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45. The electronic cooktop control system of claim 42, wherein the sensor is a
thermal limiter.
46. The electronic cooktop control system of claim 28, wherein control of the
heating level of the
cooktop in the first manner includes controlling the heating level with a
first degree of
precision, and control of the heating level of the cooktop in the second
manner includes
controlling the heating level with a second degree of precision.

47. A power control system for controlling a plurality of heating elements
including a first heating
element and a second heating element, the control system comprising:
a digital communication bus;
an electronic controller including an input and an output;
a rotary position input operatively connected to the input of the controller;
and
a power unit operatively connected to the electronic controller, the power
unit having a first
power output that supplies powering electrical energy to the first heating
element, and a
second power output that supplies powering electrical energy to the second
heating
element,
wherein rotation of the rotary position input in a first manner controls a
level of the first
power output and rotation of the rotary position input in a second manner
controls a
level of the second power output, and
wherein the electronic controller and the power unit communicate
bidirectionally over the
digital communication bus.

48. The power control system of claim 47, wherein rotation of the rotary
position input in the first
manner controls the first heating element without the second heating element,
and the
rotation of the rotary position input in the second manner controls the second
heating
element.

49. The power control system of claim 48, wherein the rotation of the rotary
position input in the
second manner controls the first heating element concurrently with the second
heating
element.

50. The power control system of claim 49, wherein the second heating element
surrounds the
first heating element.





51. The power control system of claim 49, wherein the second heating element
is adjacent to
the first heating element.

52. The power control system of claim 49 further comprising:
a third power output of the power unit; and
a third heating element powered by the third power output,
wherein the rotation of the rotary position input in the second manner
concurrently controls
the first heating element, the second heating element and the third element.

53. The electronic cooktop control system of claim 47, wherein the rotation of
the rotary position
input in the first manner overlaps the rotation of the rotary position input
in the second
manner.

54. The power control system of claim 47, wherein the rotation of the rotary
position input in the
first manner includes rotation in a first direction, and the rotation of the
rotary position input in
the second manner includes rotation in a second direction.

55. The power control system of claim 54, wherein the rotation of the rotary
position input in the
first direction includes rotation of the rotary position input from a first
position toward a second
position that is greater in angular magnitude than the first position, and
wherein the rotation of
the rotary position input in the second direction includes rotation of the
rotary position input
from a first position toward a second position that is lesser in angular
magnitude than the first
position.

56. The power control system of claim 54, wherein the rotation of the rotary
position input in the
first direction includes rotation in a clockwise fashion from a zero position,
and the rotation of
the rotary position input in the second direction includes rotation in a
counter-clockwise
direction from the zero position.

57. The power control system of claim 54, wherein the zero position is at a 12
o'clock position of
the rotary position input.

58. The power control system of claim 47, wherein the rotation of the rotary
position input in the
first manner includes rotation over a first range of angular rotation, and the
rotation of the

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rotary position input in the second manner includes rotation over a second
range of angular
rotation.

59. The power control system of claim 47, wherein the rotary position input
includes a variable
resistive device.

60. The power control system of claim 59, wherein the variable resistive
device is a
potentiometer.

61. An electronic cooktop control system comprising:
an electronic controller that controls a heating level of a heating element in
response to
rotation of a rotary position input, wherein the electronic controller
determines whether
the rotation is clockwise or counter-clockwise and determines an angular
position of the
rotary position input;
wherein the electronic controller controls the heating level of the heating
element with a first
degree of precision using a first relationship between heating level and a
range of
angular positions of the rotary position input in response to and based on
rotation in the
clockwise direction from a starting point, and with a second degree of
precision using a
second relationship between heating level and another range of angular
positions of the
rotary position input in response to and based on rotation in the counter-
clockwise
direction from the starting point,
wherein the first relationship is different than the second relationship and
wherein the first
degree of precision provides control of the heating level with a different
precision than
the second degree of precision.

62. The electronic cooktop control system of claim 61 wherein said range of
angular positions of
the rotary position input overlaps said another range of angular positions the
rotary position
input.

63. The electronic cooktop control system of claim 61 further including a
sensor to monitor the
heating level of the heating element.

64. The electronic cooktop control system of claim 63 wherein the sensor is
further used to
adjust the heating level of the heating element.


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65. An electronically controlled cooktop comprising:
a first heating element and a second heating element; and
an electronic controller having a rotary position input;
wherein, when the rotary position input is rotated in a first direction from a
start position at
which both heating elements are off, the electronic controller controls
heating of the first
element and a heating level of the second heating element remains
substantially
constant, and further wherein the electronic controller controls heating of
the first and
second heating elements together when the rotary position input is rotated in
a second
direction from the start position.

66. The cooktop of claim 65 wherein the first direction is clockwise or
counter-clockwise and the
second direction is opposite from the first direction.

67. The cooktop of claim 66 wherein the first and second heating elements are
large and small
heating elements of a single burner.

68. The cooktop of claim 66 wherein the rotary position input can be rotated
more than 180
degrees in both the clockwise and counterclockwise directions.

69. A power control system for an electric heating element, the control system
comprising:
a digital communication bus;
a controller connected to the digital communication bus;
a variably resistive device connected to the controller;
a power unit connected to the digital communication bus, the power unit having
a first
electrical power output having an on state and an off state that together form
a duty
cycle and a second electrical power output also having an on state and an off
state that
together form a duty cycle; and
an electrically resistive cooktop heating element connected to said first
electrical power
output,
wherein the controller and the power unit communicate bidirectionally over the
digital
communication bus.


28



70. The control system of claim 69, further comprising a switch alternatively
supplying the first
electrical power output of the power unit with a first voltage and a second
voltage, the second
voltage being higher than the first voltage.

71. The control system of claim 69, wherein the variably resistive device
controls a level of the
first electrical power output causing the controller to adjust the duty cycle
in accordance with a
resistance of the variable resistive device.

72. The control system of claim 69, further comprising a digital display
connected to the
controller, wherein the digital display indicates a level of the first
electrical power output.

73. The control system of claim 69, wherein the controller is a master
controller and the control
system further comprises:
a slave variably resistive device connected to the master controller;
wherein the slave variably resistive device controls a level of the second
electrical power
output.

74. The control system of claim 69, wherein the variably resistive device
controls a level of the
first electrical power output and a level of the second electrical power
output.

75. A power control system for controlling a power output, the control system
comprising:
analog input means for setting a power level;
a digital communication bus;
an electronic control means for receiving input from the analog input means,
wherein the
electronic control means is connected to the digital communication bus;
a power means, connected to the digital communication bus, for providing a
first electrical
power output having an on state and an off state that together form a duty
cycle,
wherein the duty cycle is based on a signal received from the electronic
control means
and corresponding to an angular position of the analog input means that
indicates the
set power level, wherein the power means provides additional electrical power
outputs;
an electrically resistive cooktop heating element connected to said first
electrical power
output; and
additional electrically resistive cooktop heating elements respectively
connected to said
additional electrical power outputs,


29



wherein the electronic control means and the power means communicate
bidirectionally
over the digital communication bus.

76. A power control system for an electric heating element, the control
comprising:
a power means for supplying power, the power means having a first electrical
power output
having an on state and an off state that together form a duty cycle and a
second
electrical power output;
a control means for controlling the power means, the control means being in
bidirectional
communication with the power means over a digital communication bus;
a variably resistive control input means for setting the duty cycle of the
first electrical power
output, the variably resistive control input means connected to the control
means;
an electrically resistive cooktop heating element connected to said first
electrical power
output; and
another electrically resistive cooktop heating element connected to said
second electrical
power output.

77. The control system of claim 76, further comprising a switching means for
alternatively
supplying the first electrical power output of the power means with a first
voltage and a
second voltage, the second voltage being higher than the first voltage.

78. The control system of claim 76, wherein the control input means controls a
level of the first
electrical power output.

79. The control system of claim 76, further comprising a display means for
displaying
information corresponding to the duty cycle setting of the power output
received from the
control means, wherein the display means indicates a level of the first
electrical power output.

80. The control system of claim 76, wherein the control input means controls a
level of the first
electrical power output and a level of the second electrical power output.

81. A method of controlling a plurality of power outputs, comprising steps of:
inputting power setting information to an electronic controller by an analog
input device;
providing a first electrical power output and a second electrical power
output, the outputs
each having an on state and an off state which form a duty cycle for each
output;





the electronic controller adjusting the duty cycle of the first power output
according to a
position in a first predetermined range of positions of the analog input
device;
the electronic controller adjusting the duty cycle of the second power output
according to
position in a second predetermined range of positions of the analog input
device;
delivering power from the first power output to a first electrically resistive
cooktop heating
element; and
delivering power from the second power output to a second electrically
resistive cooktop
heating element.

82. The control system of claim 81, wherein a relationship between rotation of
the variably
resistive device and the adjustment of the duty cycle is nonlinear.

83. An electronic cooktop control system comprising:
a cooktop including a first heating element;
an electronic controller operatively connected to the cooktop; and
a rotary position input operatively connected to the electronic controller;
wherein the electronic controller controls a heating level of the cooktop in a
first manner in
response to rotation of the rotary position input in a first direction, and
wherein the electronic controller controls the heating level of the cooktop in
a second
manner in response to rotation of the rotary position input in a second
direction.

84. The electronic cooktop control system of claim 83, wherein the heating
level is associated
with the first heating element.

85. The electronic cooktop control system of claim 83, wherein the cooktop
further includes a
second heating element.

86. A power control system for controlling a plurality of heating elements
including a first heating
element and a second heating element, the control system comprising:
a digital communication bus;
an electronic controller including an input and an output;
a rotary position input operatively connected to the input of the controller;
and
a power unit operatively connected to the electronic controller, the power
unit having a first
power output that supplies powering electrical energy to the first heating
element, and a

31



second power output that supplies powering electrical energy to the second
heating
element, wherein rotation of the rotary position input in a first manner
controls a level of
the first power output and rotation of the rotary position input in a second
manner
controls a level of the second power output, and
wherein the electronic controller and the power unit communicate
bidirectionally over the
digital communication bus.

87. The power control system of claim 86 further comprising:
a first heating element powered by the first power output; and
a second heating element powered by the second power output.
88. An electronic cooktop control system comprising:
an electronic controller that controls a heating level of a heating element in
response to
rotation of a rotary position input, wherein the electronic controller
determines whether
the rotation is clockwise or counter-clockwise and determines an angular
position of the
rotary position input;
wherein the electronic controller controls the heating level of the heating
element with a first
degree of precision using a first relationship between heating level and a
range of
angular positions of the rotary position input in response to and based on
rotation in the
clockwise direction from a starting point, and with a second degree of
precision using a
second relationship between heating level and another range of angular
positions of the
rotary position input in response to and based on rotation in the counter-
clockwise
direction from the starting point,
wherein the first relationship is different than the second relationship and
wherein the first
degree of precision provides control of the heating level with a different
precision than
the second degree of precision.

89. The electronic cooktop control system of claim 88 wherein the first
direction is clockwise or
counter-clockwise and the second direction is opposite from the first
direction.


32

Description

s. CA 02391688 2002-06-26
~ ' ii '
r C
ELECTRONIC POWER C0~1TROL FOR COOKTOP HEATERS
BACKGROUND OF THE INVENTION
(000x] The present invention relates to. the field of electronic controls and
more specifically to an electronic power control system for cookfop heating
elements.
[0002] Conventional controls for electric cooktops utilize so-called "infinite
switches." The infinite switch comprises a bimetal switch to -control an
electric
heating element. Current flowing in the bimetal switch causes it to physically
move
through a process of heating and cooling. This movement causes the switch
contacts
to open and close, thereby, controlling the power applied to the heating
element.
(0003) The infinite switch uses pulse width modulation to control the power
output, and thus the temperature of the heating element. Rotation of the
infinite
switch changes the relationship of the closed and open times or duty cycle. As
the
switch is rotated to a higher setting the contacts remain closed for a longer
period of
time, raising the heating element temperature. Conversely, rotating the switch
to a
lower setting causes the contacts to remain closed for a shorter period of
time,
lowering the heating element temperature.
[0004] Recently, electronic controls have been increasing in popularity.
Electronic controls are capable of providing a more precise level of heating.
Further, associated digital controls a:re easier to read than an analog dial,
allowing
the quick setting of desired heat levels. Electronic controls are also capable
of
providing advanced features, such as a safety lockout.:
[OOOSj Analog controls remain desirable because their associated rotational
control knobs are often easier to manipulate and more convenient for the user
than
the button-type controls conventionally associated with electronic controls.

CA 02391688 2002-06-26
' al ' '
Likewise, using a duty cycle to control the level of heating remains
desirable,
because it allows the heating elements'to provide very low levels of heat,
including
levels suitable for warming operations.'
BRIEF SUMMARY OF THE INYENTI~hI
[0006) The present invention provides a power control system for an electric
heating element: The control system comprises a communication bus, a
controller
connected to the communication bus; a vaxiably resistive device connected to
the
controller, a digital display connected to the controller, and a power unit
connected
to the communication bus, the power unit having a power output.
[0007] According to another aspect; the present invention provides a method
of controlling a power output comprising.the steps of: inputting power setting
information to an electronic controller by a variably resistive device, and
adjusting a
duty cycle of a power output by the electronic controller according to the
angular
position of the variably resistive device.
(0008] According to yet another aspect; the present invention provides a
power control system for controlling a plurality of heating elements. The
control
system comprises a first rotational control input having a first range of
angular
rotation and a second range of angular rotation, a first heating element, and
a second
heating element. A position of the eonfrol input in the first range controls
the first
heating element and a position of the control input in the second range
controls the
second heating element.
j0009] According to a further aspect, the present invention. provides a power
control system for controlling a plurality of heating elements. The control
system

CA 02391688 2002-06-26
' ;i
comprises a first rotational control input, a second rotational control input
having a
first range of angular rotation and a second range of angular rotation, a
first heating
element, a second heating element, and athird heating element. The second
heating
element is a bridge element positioned between the first element and the third
element. The first control input controls the first heating element. A
position ofthe
second control input in the first range controls the third heating element,
and a
position of the second control input in: he second range causes the first
control input
to concurrently control the first heating element, the second heating element,
and the
third heating element.
j0010] According to a further aspect, the present invention provides a
method of controlling a plurality of power outputs comprising steps of:
inputting
power setting information to an electronic controller by a variably resistive
device,
the electronic controller adjusting a duty cycle of a first power output
according to a
position in a first predetermined range of positions of the variably resistive
device,
and the electronic controller adjusting a duty cycle of a second power output
according to position in a second predetermined range of positions ofthe
variably
resistive device.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
(0011 J FIG. l is :a schematic, representation of a power control system
connected to an electric cooktop according to an embodiment of the present .
invention;
[00I2], FIG. 1A is a schematic'representation of a control scheme of a power
control system according town embod'iment'of the present invention;

v CA 023916882002-06-26
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s ,
[0013] FIG. 2 is plot of power; output according to an embodiment of the
present invention;
[0014] FIG. f is schematic representation of a control scheme of a power
control system according to another embodiment of the present invention;
[0015] FIG. 4 is schematic representation of a control scheme of a power
control system according to a further embodiment of the present invention;,
[00I6] FIG. S is schematic representation of a control scheme of a power
control system according to a further embodiment of the present invention;
[0017] FIG. 6 is schematic representation of a control scheme of a power
control sysfem according to a further embadirnent of the present invention;
[0018] FIG. 7 is schematic repiresentation of a control scheme of a power
control system according to a further embodiment of the present invention;
[0019] FIG. 8 is schematic representation of a control scheme of a power
control system according to a further embodiment of the present invention; and
[0020] FIG. 9 is a schematic representation of power and communication
connections of a power unit and user interface units according to an
embodiment of
the present invention.
DETAILED DESCRIPTION OF TI3E INVENTION
[0021] The present invention provides a rotational control knob to operate a
power controller which provides a duty cycle-controlled power output. FIG. 1
is a
schematic representation of an embodiment of the present invention in which a
power control system l0 is provided for an electric cooktop 12. The power
control
system 10 includes a power unit 14 and a plurality of user interface units 16,
16s.
4

s CA 02391688 2002-06-26
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The user interface units 16, 16s axe connected to the power unit 14 by a
communication bus 18 and the power unit 14. is connected to individual heating
elements 20 of the cooktop. The heating elements 20 are electrically resistive
and
are heated by current flowing through them.
[0022] The power unit 14 includes an electronic controller for controlling
power output to the heating elements 20. Further, the power unit 14 is
connected to
an electronic oven control unit 22. The oven control unit 22 controls various
operations of an oven (not shown), including the initialization of an oven
cleaning
cycle. The oven control unit 22 communicates bidirectionally with the power
unit
14 via a two-line oven control communication bus 23 fox synchronizing certain
operations between the operation of the oven by the oven control unit 22 and
the
operation of the cooktop heating elements 20 bX the power unit 14.
Specifically, by
way of the oven control communication bus 23the power unit L4 is capable of
instructing the oven control unit 22 to lockout or prevent the initiation of a
cleaning
cycle or other operation when one or more of the heating elements 20 are in
use.
Likewise, the oven control unit 22 is capable of instructing the power unit 14
to
lockout the powering of any cooktop heating element 20; such as when a
cleaning
cycle has been initiated or after a lockout button has been pressed. As used
herein,
the term "lockout" refers generally to the disabling of control or operation
of some
aspect of the power control system 10 .
[0023] Each user interface unit 16, 16s-includes a potentiometer 24, 24s and
a power level display 26, 26s. Each taster user interface unit 16 further
includes an
electronic controller 28. A knob is attached, to manually control the rotation
of the
potentiometer 24; 24s. The potentiometer 24; 24s acts as a~rotational control
input

CA 02391688 2002-06-26
a , ; ,'
device. An angular position of the potentiometer 24, 24s, and thus the knob,
is
determined by the electronic controller 28 based upon known values
representing the
relationship between angular position and potentiometer resistance. The
angular
position is communicated to the power unit 14 via the communication bus 18.
Display information is communicated by the power unit 14 back to the
electronic
controller 28 via the communication bus l 8. It is contemplated that other
variably
resistive devices, such as rheostats, can be substituted for the
potentiometers 24, 24s
according to the present invention. ;
[~024J Each electronic controller 28 controls its respective display 26, 26s
based upon the display information received from the power unit 14. Each power
level display 26, 26s is a two-digit seven-segment light-emitting diode (LED)
display for indicating a power level orsetting based on a level chosen by the
user
using the respective potentiometer 24,; 24s. The power level is displayed on
the
display 26; 26s as "LO" indicating the, lowest setting, "HI" indicating the
highest
setting; or as a number from 1.0 to 9:0 in predetermined increments;
indicating an
intermediate setting. A larger number indicates a higher level of power: The
power
level display 26, 26s is also used fox displaying other messages, as further
explained
herein, including warning messages and error codes. it is contemplated that
other
types of digital displays can be substituted for the two-digit LED display 26,
26s,
such as a liquid crystal displays (LCDs), plasma displays, mechanical
displays,
cathode ray tubes (CRTs), vacuum fluorescent displays (VFDs), discrete LEDs,
discrete LEDs arranged in a clock-like fashion, LED bar graphs, and the like.
(0025] The display 26, 26s is also used in the present embodiment to display
a visual indication that the respective heating element 20 has been locked out
of
6

' CA 02391688 2002-06-26
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operation by displaying "--". The oven control unit 22 includes a buzzer or
other
audible warning device to emit an audible warning. Further, using the oven
control
communication bus 23; the power unit l4 can instruct the oven control unit 22
to
emit an audible warning tone when a user attempts to operate the heating
elements
20 that have been locked out. Thus; the power unit 14 can cause an audible
tone to
be generated without requiring a separate audible warning device to be
provided to
the power unit 14.
[0026] In FIG: 1A; a simple control scheme is illustrated by way of example.
The power output to a heating element 20' is controlled by turning a
respective
potentiometer 24' through its entire or full range of angular rotation. A
small
segment or range of the angular rotation is used to turn the heating element
20'
completely off. The potentiometer 24' is provided with a physical detent, or
other
tactile indication or the like, to indicate when the "off range" is correctly
engaged
The term "single potentiometer" is used herein with reference to a
potentiometer
operating to control a single heating element over the potentiometer's entire
range,
such as the potentiometer 24' shown in FIG. l A.
[0027] In the embodiment of FIG. l, the user interface units 16, 16s are
provided in pairs consisting of a master unit 16' and a slave unit 16s. The
potentiometer 24s and the display 26s of the slave unit 16s are connected to
the
controller 28 of the master unit 16. The master unit l6 communicates with the
power unit l4 for both user interface units 16, 16s via the communication bus
18.
[0028] The power unit 14 also delivers pulse width modulated output
current to each heating element 20: The power unit 14 controls current and/or
voltage to each heating element 20 to produce the desired output power to
power the

w CA 02391688 2002-06-26
ii ' a
heating elements 20.
[0029) The duty cycle of the output current delivered to each heating
element 20 is determined by the angular position of a respective one of the
potentiometers 24, 24s. Duty cycle is expressed as a ratio of current on-time
to the
period (sum of current on-time and off time). As explained above, the power
level
provided to each heating element 20 is displayed on the respective power level
display 26, 26s.
j0030] In the embodiment of F'IG. l, the output power provided to the
heating elements 20 is fixed as 240 VAC, which would typically be provided
from
two-phase utility power. It should be appreciated that-maximum output power is
equal to the maximum output voltage multiplied by the unmodulated output
current.
Thus, it is contemplated that the volfa~e of the output power could also be
modulated, in addition to the duty cycle of the current; by thepower unit I4-
to .
control the output power. For example switching from 240 VAC to 120 VAC, by
utilising a single phase of the two-phase utility power, could be used to
provide
additional control, especially for achieving lower power outputs.
[0031] For a single potentiometer; such as in the example of FIG. 1A, the
relationships between angular position, display 'information and output power
are
determined according to Table 1, below. The output power is expressed as a
percentage of maximum output power; or the dutycycle times 100 percent.
8

i'ABLE 1



24 54 42 9.0 95


25 42 30 Hi
100


(0032] Since
the power
level is
controlled
electronically,
the relationship


between the
potentiometer
angular position
and the power
output can
be nonlinear,


and even nonuniform
such that
the relationship
cannot be
expressed
as an equation.


For example,
the power
level is
incremented
in steps
of 0.2 from
1.0 to 3.0
and in


larger steps
of 0.5 from
3.0 to 9.0:
This allows
more control
in the lower
heating


ranges, which'is
useful for
cooking and
keeping food
warm. Turning
the


potentiometer
to above
330 degrees
and below
30 degree
, in the
off xange,
turns the


power completely
off. As referred
to herein;
zero degrees
is at a I2
o'clock position


on the potentiometer
and succeeding
degrees are
measured
in a clockwise
fashion.


[0033] Alternatively,
as embodied
in the various
alternative
control schemes


of FIGS. 3-8,
one potentiometer
can be used
to control
two or more
power outputs,


and thus two
or more heating
elements.
A potentiometer
being used
in this way
is


referred to
herein as
a "dual potentiometer."
According
to this alternative


embodiment
of the present
invention,
;one portion
of the total
angular rotation
of a


dual potentiometer
controls
power to
a first element
and the other
portion of
the


angular rotation
controls
power to
both the
first element
and a second
element.



Potenti-Potentiometer Power Output
Angle (%
.


ometer Leve! of max.


Position Displaypower)


MinimumMaximum


1 330 318 Lo 1


2 318 306 1.0 2


3 306 294 1.2 3



23 66 54 8.5 90



~ CA 02391688 2002-06-26
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s
Table 2, below, illustrates the operation of a dual potentiometer according to
this
alternative control scheme.



Potenti-Dual er Angle Power Output
Potentiomet from (%
0


ometer ~ Left Right Lever of max.
Side Side


PositionMinimum MaximumMinimum 11r1aximumDisplaypower)--


1 196 190 170 164 Lo 1
-


2 201 196 164 159 1.0 2


3 207 201 159 153 1.2 3 '



23 319 313 47 41 _8.5 90


24 324 319 41 36 ~ 9.0 95


25 330 324 36 30 Hi 100


[0034] The specific numbers or values shown in Tables I and 2 are given by
way of example and can be modified as appropriate to meet the needs of a
particular
application.
[0035] FIG. 2 is a plot of potentiometer position versus duty cycle (in
percent of maximum power) as embodied by the control schemes of Tables 1 and 2
above. As set forth in Tables 1 and 2, each "potentiometer position" relates
to an
angular range of potentiometer rotation. Thus, although the potentiometer
rotates
smoothly throughout its range; the duty cycle is- controlled in discrete steps
corresponding to the specifrc ranges of potentiometer rotation set forth in
Tables 1
and 2. The minimum duty cycle of the present embodiment is 1%, as shown in
FIG.
(0436] FIG. 3 shows another embodiment in which a dual potentiometer 124
is arranged to control a dual heating element 120, having concentrically
arranged
inner heating element 120b and outer heating element 120a. The left portion
124L of
TABLE 2

' CA 02391688 2002-06-26
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the angular rotation of the dual potentiometer 124, from 190 to 330.degrees,
controls
power to the inner heating element 120b only, and the right portion 1248 of
the
angular rotation of the dual potentiometer 124, from 170 to 30 degrees;
controls both
heating elements 120a, 120b simultaneously.
[0037] FIG. 4 shows another embodiment using a dual potentiometer 224a to
control a single heating element 220a and a separate bridge heating element
220b.
The bridge heating element 220b provides heating between the single .heating
element 220a and a second heating element 22Dc spaced apart from the single
element 220a. The dual potentiometer 224a operates similarly to the dual
potentiometer 124a of the embodiment of FIG. 3, Specifically, the Ieft portion
224aL of the angular rotation of the dual potentiometer 224a controls power to
the
single heating element 220a only, and the right portion 224aR of the angular
rotation
of the dual potentiometer 224a, controls both the single heating element 220a
and
the bridge element 220b simultaneously. Power to the, second single heating
element
220c is controlled by a single potentiometer 224b:
[0038] FIG. 5 shows an embodiment using two potentiometers 324a, 324b to
control three heating elements: two single heating elements 320a, 320c and a
bridge
heating element 320b. The first potentiometer 324a controls the first single
heating
element 320a around its entire angular-rotatiori 324a1. The second
potentiometer
324b is a "modified single pfltentiometer;" wherein 324b controls the second
single
heating element 320c over most of its angular rotation 324bM, except that a
small
range 324bB of the angular rotation is used to enable bridge control: A
physical
detent, or the like, indicates that the second potentiometer 324b is set on
the bridge
control range 324bB. When bridge control is enabled by the second
potentiometer
11

~ CA 02391688 2002-06-26
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324b; the first potentiometer 324a simultaneously controls all three heating
elements
320a-c over its entire angular rotation 324a2. This allows all three heating
elements
320a-c to be easily and accurately set to the same power Ievel.
[0039] FIG. 6 shows an embodiment which uses principles from both the
embodiment of FIG. 4 and the embodiment of FIG. 5. Like the embodiment of FIG.
S, a second potentiometer 424b; being.a modified single potentiometer,
controls only
a second single heating element 420c over most of its angular rotation 424bM
and
places the first potentiometer 424a in bridge control mode at a bridge control
range
424bB. The first potentiometer 424a of FIG. 6 is a dual potentiometer and
operates
much like the first potentiometer 224a of FIG. 4,;controlling the first
heating
element 420a over the left portion of rotation 424aLI and controlling both the
first
heating element 420a and the bridge hating element 420b over the right portion
424aR l -o.f angular rotation. When the first potentiometer 424a of FIG. 6 is
placed
in bridge mode by the second potentiometer 424b, the first potentiometer-424a
controls all three heating elements 420a-cover either portion 424aL2, 424.aR2
of its
angular rotation.
[0040] FIG. 7 is a variation on;the embodiment of FIG. 6. The first
potentiometer 524a normally acts as a dual potentiometer, independently
controlling
the first heating element 520a over its left portion 524aL and controlling
both the
bridge element 520b and the first heating element 520a over its right portion
524aR.
When bridge control is enabled, the first potentiometer 524a acts as a single
.
potentiometer. That is, when the second potentiometer 524b, being a modified
single potentiometer, is placed in its bridge range 524bB, the first
potentiometer
524a controls all three heating elements 520,a-c over its entire range 524aE
of
12

' CA 02391688 2002-06-26
' ii '
angular rotation: This provides more precise control of power than the scheme
of
FIG. 6.
[U041] FIG. 8 is an additional embodiment for controlling two single heating
elements 620a, 620c and a bridge heating element 620b. First and second
potentiometers 624a, 624b are both dual potentiometers: The first
potentiometer
624a controls the first single heating element 620a over the left portion
624aL of its
angular rotation and controls both the first single heating element 620a and
the
bridge heating element 620b simultaneously over the right portion 624aR of its
angular rotation. The second potentiometer 624b controls the second single
heating
element 620c over the right portion 624bR of its angular rotation and controls
all
three heating elements 62Oa-c simultaneously over the left portion 624bL of
its
angular rotation. When the second potentiometer 624b is controlling ail three
heating elements 620a-c, the first po entiometer 624a is disabled from
controlling
any of the heating elements 620a-c.
[0042] Referring again to FIG. l, thermal limners 30 are provided to prevent
the heating elements 20 from overheating and potentially causing damage, such
as
when the heating elements 20 are covered by a flat glass cooking surface. Each
limiter 3O comprises two bi-metallic thermostatic switches or limiter
elements: a
high temperature witchand a low temperature switch:
[0043] The high temperature switch in each limner 30 is connected directly
to a corresponding heating element 20. The high temperature switch opens at
temperatures above thl, such as SOO degrees Celsius, thus disconnecting power
from
the heating element 20.. Once the heating element 20 cools below th=, the high
temperature switch closes, reconnecting power to the heating element 20. It is
13

' CA 02391688 2002-06-26
:~
contemplated that the high temperature switch could be connected in a
different
manner; for example by being connected via the controller of the power unit
14.
rather than directly to the heating element 20.
[0044] The low temperature switch in each limiter 30 is connected to the
power unit 14. The low temperature switch opens when the temperature falls
below
tjo, such as 50 or 70 degxees Celsius. When the low temperature switch is
closed, the
power unit 14 causes a heat warning to be displayed on the seven-segment power
level display 26, 26s, such as "HE" for element, "HS" for hot surface, "HC"
for hot
cooktop, or other appropriate display, indicating that the cooking surface at
the
respective heating element 20 is too hot to touch. Alternatively, a warning
lamp or
indicator could be used to display the heat warning.
[0045] As a further alternative; the low temperature switch or limner
element can be replaced by a timing mechanism which causes the heat warning to
be
displayed for a predetermined period of time, after which the respective
heating
element 20 should have predictably fallen below too. The timing mechanism can
be
implemented by the electronic controller of the power unit 14, or by some
other ',
known means. Nonvolatile memory, such as an EEPROM, can be provided to the
power unit l4 to retain timing information in the event of a power failure:
[0046] FIG. 9 illustrates a communication-and power connection
arrangement according to an embodiment of the present invention including a
power
board 714 and two master user interface units 716L; 7168. Communication
between
the master user interface units 716L, 7168 and the power board714 is
accomplished
by a one wire serial communication bu ox wire 718,provided in a wiring harness
730. In addition to the communication wire 718; the 5-wire harness 730 also

~ CA 02391688 2002-06-26
v ~ ;~
includes +12 VDC, ground, +5 VDC, and an identification wire. With the
exception
of the identification wire, each of the S wires is connected from the power
unit 714
to each of the master user interface units 716L, 7168.
[0047] The identification wire 732 carries a +5V identificatiom signal from
the power unit 714 to the right master user interface unit 7168, telling the
unit 7168
that its position is "right." Since there is no connection between the
identification
wire 732 and the left master user interface unit 716L, the unit 716L will not
receive
the identification signal, causing the unit 716L to identify its position as
"left." It
should be appreciated that the "right" and "left" positions can be transposed
without
departing from the present invention.
[0048] Potentiometer angle information from a master interface unit 716L,
7168 or a slave user interface unit 716LS, 7I6RS is digitally encoded by the
microprocessor in the respective master user interface unit 7168; 7I6S and
sent to
the power unit 714 via the communication bus 718; similarly to that described
above
with reference to FIG. 1. Likewise, digital display information is sent from
the
power unit 7I4 to the user interface units 7 i 6L~ 7168, via the communication
bus
718. An identification code is included-in each communication to identify the
sender or recipient user interface unit as the left master unit 716L, the left
slave unit
716LS, the right master unit 7168, the right slave unit 716RS. The
identification
code also indicates whether the corresponding potentiometer is being used as a
single or dual potentiometer, whereby,the power board 714 controls the user
interface unit 716 and its corresponding heating element according to the
appropriate set of data, as exemplified in Tables 1 and 2.

M
~ 02391688 2002-06-26


i1


0049] A 3-bit identification
code is shown in the
following table:


TABLE 3


Description ~ LeftIRightMaster/SlaveSinglelDual


Pair (b2)Unif (b,)Element
(bo)


Left pair, Master unit, 0 - 0 0
Single element


Left pair, Master unit, 0 0 1
Dual element


Left pair, Slave unit, 0 1 , 0
Single element


Left pair, Slave unit; 0 1 1
Dual element '


Right pair, Master unit, 1 ' 0 0
Single element


Right pair, Master unit; 1 0 1
Dual element


Right pair, Slave-unit, 1 1 0
Single element


Right pair, Slave unit, 1 1 1 [
Dual element


[0050] The remaining wires in the wiring harness 730 are used for providing
operating voltages to the user interface units 716L, 716LS, 7168, 716RS.
(0051] It sho~.tld be evident that this disclosure is by way of example and
that
various changes may be W ade by adding; modifying or eliminating details
without
departing from the fair scope of the teaching contained in this disclosure.
The
invention is therefore n:ot limited to particular details of this disclosure
except to the
extent that the following claims are necessarily o limited.
16

Representative Drawing