Abstract:
An apparatus and a method for measuring temperature in a cooking appliance, both of which utilize a circuit for reading an input from a thermal resistive device. By including a processor and an amplifier in the circuit, embodiments reduce the number of processor pins required to modify the amplified input arising from the amplifier. In one embodiment, the processor utilizes a single processor pin, through which is distributed a control output corresponding to the input and modifying the operating parameters of the amplifier.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates generally to cooking appliances, and more particularly to embodiments of an apparatus and a method for temperature control on a cooking appliance. 
         [0002]    Temperature control on cooking appliances such as stoves, ovens, and ranges typically requires amplification of a signal from a temperature sensor located in the heated cavity of the appliance. The amount of amplification is reflected by temperature bands, which indicate the amount of gain and shift applied to the signal. Conventional schemes select the appropriate temperature band using combinations of discrete elements such as resistors and transistors and multiple outputs of a corresponding processing device. The number of temperature bands is limited by the available combinations of elements and/or outputs allocated for the scheme. 
         [0003]    Therefore it is advantageous to provide an improved scheme for temperature control that increases the number of temperature bands. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    In one embodiment, a cooking appliance with a cavity heated by a heating element. The cooking appliance comprises a temperature sensor under constant voltage, the temperature sensor in communication with the cavity. The cooking appliance also comprises an amplification circuit coupled to the temperature sensor, the amplification circuit comprising an amplifier for amplifying a first input from the temperature sensor. The cooking appliance also comprises a processor having an output pin coupled to the amplifier, wherein the first input is amplified by an amount corresponding to a control output conducted through the output pin from the processor. 
         [0005]    In another embodiment, a method for monitoring temperature in a cavity of an oven. The method comprises steps for generating a first input respecting the temperature of the cavity and selecting a temperature band from the first input. The method also comprises a step for formulating a control output corresponding to the temperature band. The method further comprises a step for communicating the control output via a single output pin and a step for generating a second input in response to the output. 
         [0006]    In yet another embodiment, a temperature control circuit comprises a temperature sensor under constant voltage. The temperature control circuit also comprises a voltage divider coupled to the temperature sensor, an operational amplifier coupled to a first leg of the voltage divider, and a processor coupled to a second leg of the voltage divider. The temperature control circuit defined wherein the processor has an output pin coupled to the operational amplifier, and wherein the processor is operatively configured to generate a control output that identifies a temperature band respecting the operating parameters of the operational amplifier. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Reference is now made briefly to the drawings, in which: 
           [0008]      FIG. 1  is a schematic diagram of an exemplary embodiment of a temperature control circuit. 
           [0009]      FIG. 2  is a schematic diagram of another exemplary embodiment of a temperature control circuit. 
           [0010]      FIG. 3  is a flow diagram of an exemplary embodiment of a method for selecting a temperature band in a temperature control circuit, such as the temperature control circuits of  FIGS. 1 and 2 . 
           [0011]      FIG. 4  is a perspective view of an exemplary cooking appliance, on which is incorporated a temperature control circuit, such as the temperature control circuits of  FIGS. 1 and 2 . 
       
    
    
       [0012]    Like reference characters designate identical or corresponding components and units throughout the several views, which are not to scale unless otherwise indicated. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    A temperature control circuit is described that is useful to regulate the temperature in cooking appliances such as ovens, ranges, stoves, and related cooking devices. Exemplary temperature control circuits are often incorporated into more complex control structures, which facilitate the operation of the cooking appliance. Depending on factors such as model type and the sophistication of the cooking appliance, the control structure also includes processors configured to regulate a multitude of functions and options that, in addition to temperature control, include cleaning functions, the operation of multi-functional displays, and myriad cooking functions for broiling, baking, and convection cooking. 
         [0014]    Because space in the housing of these cooking appliances is limited, however, making these and other functions and options available to the consumer is difficult, competing instead with other interests such as design parameters that desire to maintain or even reduce the footprint of the control structure. Embodiments of the temperature control circuit described below address each of these interests by reducing the number of pins on the processor that are necessary for regulating temperature. This reduction makes pins available for use in connection with other options and functions without the need to modify the control structure such as through the addition of components, circuitry, and the like. Moreover, in addition to maintaining the overall footprint of the control structure, the temperature control circuit also improves the temperature control function such as by increasing the resolution and accuracy of the temperature measurement. 
         [0015]    Further understanding of these concepts can be had in connection with the schematic block diagram of  FIG. 1 , in which there is depicted an exemplary embodiment of a temperature control circuit  100 . In the present example, the temperature control circuit  100  includes a temperature sensor  102  such as a resistive thermal device (RTD) that is located in communication with a heated cavity  104  of an oven  106 . The temperature sensor  102  is coupled to a power supply  108 , with one example providing to the temperature sensor  102  a constant voltage with a nominal value of 5 VDC. The temperature control circuit  100  also includes a variety of circuitry  110 , which includes a processor circuit  112  and an input circuit  114  coupled to the processor circuit  112 . In one embodiment, the input circuit  114  includes a voltage divider  116  and an amplification circuit  118 . 
         [0016]    At a relatively high level, configurations of the circuitry  110  include one or more groups of electrical circuits that are each configured to operate, separately or in conjunction with other electrical circuits, to sense the temperature in the heated cavity  104 . The electrical circuits of the circuitry  110  can communicate with other circuits (and/or devices), which execute high-level logic functions, algorithms, as well as firmware and software instructions. Exemplary circuits of this type include, but are not limited to, discrete elements such as resistors, transistors, and capacitors, as well as microprocessors and other logic devices such as field programmable gate arrays (“FPGAs”) and application specific integrated circuits (“ASICs”). While all of the discrete elements, circuits, and devices function individually in a manner that is generally understood by those artisans that have ordinary skill in the electrical arts, it is their combination and integration into functional electrical groups and circuits that generally provide for the concepts that are disclosed and described herein. 
         [0017]    The electrical circuits of the circuitry  110 , and more particularly the processor circuit  112 , may be implemented in a manner that can physically manifest theoretical analysis and logical operations. This implementation is useful to facilitate resolution of inputs, e.g., the inputs of the temperature sensor  102 . These electrical circuits can replicate in physical form an algorithm, a comparative analysis, and/or a decisional logic tree, each of which operates to assign the output and/or a value to the output that correctly reflects one or more of the nature, content, and origin of the changes that occur and that are reflected by the relative inputs from, e.g., the input circuit  114 . 
         [0018]    In one implementation, rather than utilizing a single input from the temperature sensor  102 , the temperature control circuit  100  is configured to analyze a plurality of inputs. These inputs include in one example a temperature input arising from the temperature sensor  102  and an amplified input that is the amplified version of the temperature input. These two inputs are compared such as to determine a measured difference in temperature readings corresponding, respectively, to the temperature input and the amplified input. In one embodiment, a measured difference that exceeds about 50° C. is flagged as an error. 
         [0019]    This configuration overcomes issues with resolution consistent with single input circuitry, such as issues in which the temperature input may not provide enough resolution over the range of temperatures for the heated cavity  104 . Amplification of the temperature input to the amplified input and subsequent comparison of the amplified input and the temperature input, however, may be utilized to more accurately analyze the temperature of the heated cavity  104 . In one implementation, this comparison provides a means to monitor operation of, e.g., the oven, so as to identify failure of one or more components. Such failure can cause calibration issues, and more particularly, failure of the temperature sensor may lead to further calibration issues in self-cleaning ovens. 
         [0020]    By way of example, and as depicted in  FIG. 1 , the temperature sensor  102  generates a temperature input T 1  respecting the temperature in the heated cavity  104 . This temperature input T 1  is received by the input circuit  114  such as at the voltage divider  116 . The voltage divider  116  in turn generates a pair of divided inputs that include a course temperature input T course , having parameters similar to the temperature input T 1 , and an amplified temperature input T amplified . The latter, i.e., the amplified temperature input T amplified , is received by the amplified circuit  118 , which generates a fine temperature input T fine , which is in effect the amplified version of temperature input T 1 . 
         [0021]    Exemplary configurations of the processor circuit  112  are coupled to the input circuit  114  and more particularly to the amplified circuit  118 . This coupling permits a control output C output  from the processor circuit  112  to influence the parameters of the fine temperature input T fine . The control output C output  is selected in response to the course temperature input T course  that is received by the processor circuit  112 . In one example, the control output C output  changes the operation of the amplified circuit  118  such as by setting one or more operating parameters that effect the amplification of the amplified temperature input T amplified  to the fine temperature input T fine . 
         [0022]    Referring now to  FIG. 2 , there is depicted another exemplary embodiment of a temperature control circuit  200  in which elements such as resistors and capacitors are configured so as to affect the concepts discussed above. Like numerals are used to identify like components as between  FIGS. 1 and 2 , wherein the numerals are increased by  100  (e.g.,  100  is now  200  in  FIG. 2 ). For example, the temperature control circuit  200  includes a temperature sensor  202  in a heated cavity  204  of an oven  206 . The temperature control circuit  200  also includes a power supply  208 , and circuitry  210  with a processor circuit  212  and an input circuit  214 , the latter, i.e., the input circuit  214 , being configured with a voltage divider  216  and an amplification circuit  218 . 
         [0023]    In one embodiment, the temperature control circuit  200  includes a microprocessor  220  such as the ASIC and/or FPGA described above. The microprocessor  220  includes a plurality of processor pins  222 , and particular to the discussion below the processor pins  222  are configured with a course input pin  224 , a fine input pin  226 , and a control output pin  228 . The temperature control circuit  200  also includes an operational amplifier  230  with an amplifier output  232  coupled to the fine input pin  226 . The operational amplifier  230  also includes amplifier inputs  234  such as a control input  236 , which is coupled to the control output pin  228 , and an amplified input  238  that is coupled to the voltage divider  216 . The temperature control circuit  200  also includes a digital-to-analog converter  240 , which in the present example is located internal to the microprocessor  220 . 
         [0024]    Microprocessors of the type used as the microprocessor  220  are configured to provide an output such as the control output C output  via the control output pin  228 . This output is often digitized or in the form of a digital output or digital signal such as a voltage between 0 and Vcc, wherein Vcc is the voltage supplied to the microprocessor from the power supply (e.g., power supply  108 ). In the present example, Vcc is 5 V dc, but can vary in connection with the various configurations of, e.g., the control structure discussed above. For compatibility with the operational amplifier  230 , the output is converted to an analog consistent voltage. The conversion can be achieved by providing the D/A converter  240 . Exemplary microprocessors are configured for such conversion such as by including the D/A converter  240  therein (as depicted in  FIG. 2 ) or otherwise being configured with functionality to provide the output in the form for use by, e.g., the operational amplifier  230 . Other embodiments of the temperature control circuit  200 , however, are also contemplated in which the D/A converter (or the digital-to-analog functionality) is located external to the microprocessor  220 . 
         [0025]    The microprocessors are likewise configured via the construction and compilation of internal circuitry and/or implementation of executable instructions to select the output from one or more inputs. These inputs include, but are not limited to, the course temperature input T course  received via the course input pin  224 . By way of example, the microprocessor selects operating parameters of the operational amplifier in response to the course temperature input T course  and formats the output (e.g., the control output C output ) to modify the operation amplifier in accordance with the selected operating parameters. The operating parameters are used to tune the fine temperature input T fine  received at the fine input pin  226 . In one example, the number of processor pins  222  to generate the fine temperature input T fine  does not exceed three. In another example, the operating parameters include the gain and shift applied by the operation amplifier. Other operating parameters are also available such as those parameters consistent with operational amplifiers of the type contemplated herein. 
         [0026]    In one embodiment, the operating parameters correspond to one or more temperature bands. These temperature bands identify particular parameters of the fine temperature input T fine  that are analyzed by the microprocessor  220  to reflect the actual temperature of the heated cavity  104 . The number of temperature bands can vary in connection with the selected configuration of the microprocessor, with one construction of the temperature control circuit  200  providing more than the 8 temperature bands found in conventional construction of temperature sensing circuitry, which utilize discrete elements such as resistors and transistors. Likewise in another construction the number of temperature bands is a function of the binary combination of bits available in the D/A converter (e.g., D/A converter  240  ( FIG. 2 )). In one example, the number of temperature bands can be at least about  128 , while other examples can utilize at least about 256 temperature bands. 
         [0027]    To further illustrate the selection of the temperature bands by way of the temperature control circuits discussed above, referenced can now be had to the exemplary embodiment of a method  300  of  FIG. 3 . The method  300  includes steps  302 ,  304 ,  306 ,  308 , and  310 , the execution of which is useful to controlling the temperature of an oven. In one embodiment, the method  300  includes a step  302  for generating a first input respecting the temperature of a heated cavity of the oven. The method  300  also includes a step  304  for selecting a temperature band from the first input and a step  306  for formulating an output corresponding to the selected temperature band. The method further includes a step  308  for communicating the output via a single pin such as the control output pin  228  ( FIG. 2 ) and a step  310  for generating a second input in response to the output. 
         [0028]    In one embodiment, one or more processors such as the processor circuit  112  and the microprocessor  220  execute one or more of the steps outlined above. This execution can be in the form of executed instructions such as are consistent with software and/or firmware instructions. By way of example, these instructions can include operations that compare the various inputs such as the course temperature input T course  and the fine temperature input T fine . Differences between these inputs can be used to select and/or adjust the output, or in one example the difference is used to change the operating parameters of the operational amplifier. These changes are made in response to one or more of the temperature bands, thus providing real-time adjustment to the resolution and accuracy of the temperature control circuit as described herein. 
         [0029]    Implementation of the method  300  of  FIG. 3  and the temperature control circuits  100  and  200  of  FIGS. 1 and 2  respectively, is relevant with respect to the exemplary embodiment of a cooking appliance  400  in  FIG. 4 . The cooking appliance  400  is depicted in the form of a free-standing range  402  including an outer body or cabinet  404  that includes a generally rectangular cooktop  406 . A cavity  408  is positioned below cooktop  406  and has a front-opening access door  410 . The cavity  408  can include a heating element (not shown) disposed therein, wherein operation of the heating element changes the temperature of the cavity  408  such as during cooking. A range backsplash  412  extends upward from a rear portion  414  of cooktop  406  and contains a multi-functional display  416  for selecting operative features of heating elements for cooktop  406  and/or the cavity  408 . Cooking appliance  400  is provided by way of illustration rather than limitation, and accordingly there is no intention to limit application of the present invention to any particular appliance or cooktop, such as range  402  or cooktop  406 . In addition, it is contemplated that temperature control circuits discussed herein are applicable to many types of cooking appliances including, but not limited to, electric, gas, and duel fuel cooking appliances, e.g., a gas cooktop with an electric oven. 
         [0030]    Cooktop  406  includes four surface burners  418 ,  420 ,  422 , and  424 , which are positioned in spaced apart pairs  426  and  428  positioned adjacent each side of cooktop  406 . In one embodiment, each pair of burners  426  and  428  is surrounded by a recessed area (not shown in  FIG. 4 ) of cooktop  406 . The recessed areas are positioned below an upper surface  430  of cooktop  406  and serve to catch any spills on cooktop  406 . Each burner  418 ,  420 ,  422 , and  424  extends upwardly through an opening in cooktop  406 , and a grate assembly  432  is positioned over each respective pair of burners  426  and  428 . Each grate assembly  432  includes a respective frame  434  and separate supporting grates  436 ,  438 ,  440 , and  442  are positioned above the cooktop recessed areas and overlie respective burners  418 ,  420 ,  422 , and  424 . 
         [0031]    Noted is that the configuration the temperature control circuits of the present disclosure are compatible with the electric, gas, and duel-fuel type variations of the cooking appliance  400 . Moreover, whereas cooktop  406  includes various components that might be configured for certain types of variations, it is equally as likely that one or more of these components would not be useful in connection with other variations. Examples of these variations include, but are not limited to, gas burners, electric burners, induction burners, and any combinations, derivations, and modifications thereof. 
         [0032]    In one embodiment, temperature control circuits such as temperature control circuits  100  and  200  are coupled to the cavity  108 . RTD temperature sensors can communicate with the interior of the cavity  108 , providing the temperature input (e.g., the temperature input T 1 ). In another embodiment, temperature sensors such as the temperature sensor  102  and  202  are coupled to the cooktop  406  such as in thermal communication with one or more of the burners (e.g., burners  418 ,  420 ,  422 , and  424 ). This thermal communication permits the temperature sensors to monitor temperature of (or proximate) the corresponding burner, thus providing the temperature input. Remaining portions of the temperature control circuit and related control structure are configure to operate in conjunction with the selected burner to maintain, monitor, and regulate temperature as disclosed and described herein. 
         [0033]    It is contemplated that numerical values, as well as other values that are recited herein are modified by the term “about”, whether expressly stated or inherently derived by the discussion of the present disclosure. As used herein, the term “about” defines the numerical boundaries of the modified values so as to include, but not be limited to, tolerances and values up to, and including the numerical value so modified. That is, numerical values can include the actual value that is expressly stated, as well as other values that are, or can be, the decimal, fractional, or other multiple of the actual value indicated, and/or described in the disclosure. 
         [0034]    This written description uses examples to disclose embodiments of the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defied by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.