Abstract:
A speed cooking oven includes a combination of radiant cooking units and a microwave cooking unit manually controllable using a rotary dial input selector coupled to a control panel for user selection of desired oven features. An alphanumeric display displays prompts and information to guide users through a feature selection process. A microprocessor executes a cooking algorithm based upon user defined constants entered via the rotary dial according to prompts on the alphanumeric display.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application No. 60/115,744, filed Jan. 13, 1999 and U.S. provisional application No. 60/150,395, filed Aug. 23, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to ovens and, more particularly, to a control system for a combination oven using both radiant and microwave energy. 
     Known ovens are either, for example, microwave or radiant cooking type ovens. For example, a microwave oven includes a magnetron for generating RF energy used to cook food in the oven cooking cavity. Although microwave ovens cook food more quickly than radiant ovens, microwave ovens do not brown the food. Microwave ovens therefore typically are not used to cook as wide a variety of foods as radiant ovens. 
     Radiant cooking ovens include an energy source such as lamps which generate light energy used to cook the food. Radiant ovens brown the food and generally can be used to cook a wide variety of foods. Radiant ovens, however, cook foods slower than microwave ovens. 
     Microwave and radiant cooking ovens typically include an array of keypads mounted to a control panel for enabling an operator to enter and select the feature options, and a numerical key pad numbered 0-9. The complexity of the control panel and the number of keypads mounted to the control panel increases as the appliance functionality and features increase. Such control panels are often complex for users to understand, offer little flexibility to the users, and do not provide users with an opportunity to adjust or review in-progress cooking without terminating the cooking. The complexity and inflexibility of such control systems increases a likelihood that the food will be cooked correctly. 
     Accordingly, it would be desirable to provide a user friendly, flexible, and easily controlled oven which provides the speed advantages of a microwave oven with the appealing browning advantage of a radiant ovens to cook a wide variety of foods. 
     BRIEF SUMMARY OF THE INVENTION 
     In an exemplary embodiment of the invention a speed cooking oven includes a microwave cooking unit for delivering microwave energy and at least one radiant cooking unit for delivering radiant energy into a cooking cavity. A control panel is operatively connected to the microwave cooking unit and radiant cooking unit for user manipulation to select desired oven features including pre-programmed cooking algorithms and manually entered cooking algorithms. A microprocessor is coupled to the control panel for executing a manually entered control algorithm based upon at least one of a user selected total COOK TIME and user selected POWER LEVEL for the microwave cooking unit and the radiant cooking unit. 
     The control panel includes a plurality of input keys and a rotary dial input selector for easy selection of desired features by rotating the dial and depressing the dial to enter a selection. An alphanumeric display is provided to prompt a user for control information and guide the user through the oven feature selection process. The oven is operable in a microwave only cooking mode, a lightwave only cooking mode and a speed cooking mode utilizing both radiant cooking units and microwave cooking units. Thus, a variety of foods may be quickly cooked and browned in the oven, and a flexible and straightforward cooking mode and control selection process is provided with the user friendly control panel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of a combination oven including a control system; 
     FIG. 2 is a front view of the control system shown in FIG. 1; 
     FIG. 3 is a perspective schematic view of a portion of the oven shown in FIG. 1; 
     FIG. 4 is a schematic illustration of the radiant cooking unit and the microwave cooking unit relative to the cooking cavity; 
     FIG. 5 is a schematic illustration of the lower lamp of the oven shown in FIG. 3; 
     FIG. 6 is a schematic illustration of the reflector for the upper lamps of the oven shown in FIG. 3; 
     FIG. 7 is an illustration of a portion of the turntable of the oven shown in FIG. 3; 
     FIG. 8 is a schematic illustration of the cooking cavity of the oven shown in FIG. 3, including a damper to control air flow; 
     FIG. 9 is a functional block diagram of the oven shown in FIG. 1; 
     FIG. 10 is a circuit schematic diagram of the oven shown in FIG. 1; 
     FIG. 11 is a timing diagram illustrating target and command times for energizing the cooking elements; 
     FIGS. 12-15 illustrate messages displayed when adjusting/entering the power level and cooking time; 
     FIG. 16 is a flow chart illustrating process steps executed when adjusting the cook time; 
     FIG. 17 is a flow chart illustrating process steps for lamp power level control; and 
     FIG. 18 is a flow chart illustrating process steps for the soft start of the Halogen lamps. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is directed, in one aspect, to operation of an oven that includes at least two types of cooking elements, such as radiant and microwave cooking elements. Although one specific embodiment of radiant/microwave cooking oven is described below, it should be understood that the present invention can be utilized in combination with many other such ovens and is not limited to practice with the oven described herein. 
     FIG. 1 is a front view of an oven  10  including a control system  12  Oven  10  includes a body  14  which is constructed of a top  16 , a bottom  18  which is connected to top  16  with a first side  20 , a second side  22 , and a rear side (not shown). Body  14  houses a cooking cavity (not shown) for receiving food (not shown) during cooking. A door  26  is hingedly attached to a front face  28  of body  14  and is pivotable to selectively open and close with a handle  29  to access the cooking cavity. Door  26  includes a window  30  fabricated from dark tinted glass having a thickness of about ⅛ inches which can withstand high temperatures, as is known in the art. Window  30  permits a user to visually inspect the cooking cavity during cooking without exposing the user to intense light generated while oven  10  is operated. Oven  10  also includes an extruded vent grill  32 . 
     Control system  12  includes a control panel  40  for selecting control information (not shown in FIG. 1) and a control interface  44  for providing visual information about the cooking to a user. Control panel  40  includes a touch control area  46 , described in more detail below, which provides the user with many feature options available during cooking. Control panel  40  also includes a rotary dial  48  configured to permit a user to select control information for cooking. Control panel  40  is operatively responsive to any selection of control information the user inputs using touch control area  46  and rotary dial  48 . 
     FIG. 2 is a front view of control system  12  including control panel  40  and control interface  44 . Control interface  44  is mounted to control panel  40  and includes alphanumeric display  50 . Alphanumeric display  50  displays the current time of day when oven  10  is not in operation. Additionally, during entry of control inputs by the user, alphanumeric display  50  provides visual prompts that guide the user through a selection process to select available options. In one embodiment, alphanumeric display  50  is a vacuum fluorescent display or LED type of display which displays multiple lines. 
     Control panel  40  includes touch control area  46  and rotary dial  48 . A user may select control inputs using touch control area  46 , rotary dial  48 , or a combination of rotary dial  48  and touch control area  46 . Touch control area  46  includes a face surface  52  which includes a plurality of keys  54  (described in more detail below) which extend from face surface  52  and are configured to permit a user to enter control inputs and activate feature options. Rotary dial  48  is rotationally attached to oven  10  and extends through an opening  56  in surface face  52 . Each key  54  is connected to a control (not shown) which includes a microprocessor (not shown) or other electronic elements for executing user selected feature options. 
     Keys  54  provide a user with oven feature options and various cooking functions and are electrically operable when depressed by a user applying a minimal amount of pressure. More specifically, keys  54  include a COOK touch control pad  60 , a START/PAUSE touch control pad  62 , a MANUAL COOK touch control pad  64 , a CLEAR/OFF touch control pad  66 , a POWER LEVEL touch control pad  68 , a DELAY START touch control pad  70 , a TIMER touch control pad  72 , a MICROWAVE touch control pad  74 , a MICRO EXPRESS touch control pad  76 , a VENT FAN touch control pad  78 , a REMINDER touch control pad  80 , an OPTIONS touch control pad  82 , a HELP touch control pad  84 , and a SURFACE LIGHT touch control pad  86 . 
     Rotary dial  48  interacts with several of keys  54  and is connected to a control (not shown) which includes a microprocessor (not shown) or other electronic elements for executing user selected oven features. Rotary dial  48  is also connected to a select switch (not shown) which is operatively engaged when the user applies a moderate pressure to depress rotary dial  48  into opening  56 . 
     Rotary dial  48  is configured to be rotated in a clockwise direction  94  or in a counter-clockwise direction  96 . Rotation in clockwise direction  94  increments a numerical selection value (not shown) and scrolls non-numerical selections in ascending alphabetical order. Rotation in counter-clockwise direction  96  decrements the numerical selection value and scrolls non-numerical selections in reverse-alphabetical order. Rotary dial  48  is configured to provide tactile feedback to a user simultaneously as rotary dial  48  is rotated. The tactile feedback allows the user to determine an amount of rotation (not shown). In one embodiment, the tactile feedback has a resolution of approximately 15-25 counts per revolution. As such, when rotary dial  48  is rotated, the user will feel approximately 15-25 “stopping points” and thus, will sense an amount of rotation of rotary dial  48 . 
     Oven features may be selected using touch control area  46 , rotary dial  48 , or a combination of rotary dial  48  and touch control area  46 . In operation, plurality of keys  54  are configured to function in cooperation with rotary dial  48 . Initially, a mode of oven  10  is selected from a lightwave only mode, a microwave only mode, and a speed cooking mode. Depressing touch control pad  60  results in the processor causing control interface  44  to visually prompt the user with alphanumeric display  50  for selections for the lightwave mode of oven  10 . Depressing microwave touch control pad  74  results in the processor causing control interface  44  to visually prompt the user with alphanumeric display  50  for selections for the microwave mode of oven  10 . Additionally, depressing microwave touch control pad  74  energizes a cooking lamp (not shown) to briefly illuminate the food being cooked. 
     Depressing COOK touch control pad  60  and rotating rotary dial  48  results in alphanumeric display  50  displaying pre-programmed control information including a listing of food types commonly cooked with a lightwave mode of oven  10 . 
     Depressing MANUAL COOK touch control pad  64  and rotating rotary dial  48  permits the user to manually input control information before the cooking of the food is started, including the length of time for cooking and the power levels to be applied by oven  10 . Additionally, depressing MANUAL COOK touch control pad  64  and then rotating rotary dial  48  permits the user to select combinations of non-preprogrammed cooking information. 
     Keys  54  also provide additional options and features to the user. Depressing POWER LEVEL touch control pad  68  enables the user to alter any pre-programmed suggested power levels. Depressing DELAY START touch control pad  70  permits the user to select a time of day for cooking to begin. Depressing TIMER touch control pad  72  permits the user to program the processor to control a timer. After an amount of time programmed into the timer has elapsed, the audible alarm sounds to indicate that the amount of time has elapsed. 
     Rubber tactile switch covers are located over each key pad of control panel  40 , and dial  48  is provided for making multiple selections. Selections are made using dial  48  by rotating dial  48  clockwise or counter-clockwise and when the desired selection is displayed, pressing dial  48 . The various selections available, in an exemplary embodiment, from dial  48  are set forth in Appendix A. Instructions and selections are displayed on alphanumeric display  50 . 
     The following functions can be selected by user manipulation of control panel  40 . 
     CLEAR/OFF Selecting this pad stops all cooking and erases the current program. 
     DELAYED Selecting this pad results in a delay in the start 
     START of cooking. 
     HELP Selecting this pad enables an operator to find out more about the oven and its features. 
     MICROWAVE Selecting this pad enables defrosting, heating beverages, reheating leftovers, popcorn, vegetables, and all types of microwave cooking. 
     MICROWAVE Selecting this pad enables quick and easy 
     EXPRESS warming of a sandwich, or reheat of coffee. 
     OPTIONS Selecting this pad enables access to the auto 
     ON/OFF night light, beeper volume control, clock, clock display, and display scroll speed features. 
     OVEN LIGHT Selecting this pad during microwave cooking illuminates the cavity. 
     POWER LEVEL Selecting this pad enables adjusting the power levels for speed cooking and microwave cooking. 
     REMINDER Selecting this pad enables an operator to select a time at which an alarm is to sound. 
     REPEAT LAST Selecting this pad facilitates cooking repetitive items such as cookies and appetizers. 
     SPEED COOK Selecting this pad enables an operator to 
     MANUAL manually enter speed cooking time and power levels. 
     START/PAUSE Selecting this pad enables an operator to start or pause cooking. 
     SURFACE LIGHT Selecting this pad turns ON/OFF the surface light for the cooktop. 
     TIMER ON/OFF Selecting this pad controls a general purpose timer (e.g., minutes and seconds). 
     VENT FAN Selecting this pad enables an operator to clear the cooktop area of smoke or steam. 
     FIG. 3 is a perspective schematic view of a portion of oven  10 . Oven  10  includes a shell  120 , and a cooking cavity  122  is located within shell  120 . Cooking cavity  122  is constructed using high reflectivity (e.g., 72% reflectivity) stainless steel. Halogen lamps  124  and  126 , and a reflective plate  128  are mounted to an upper panel  130  of shell  120 . As described below in more detail, a halogen lamp also is located at a lower section of shell  120 . An exhaust system  132  also is mounted to shell  120 . Air flows through cavity  122  in a direction indicated by arrow  134 . A cooling system  137  is mounted to shell  120  for cooling oven components. Exemplary dimensions of oven  10  are set forth below. 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Shell 
                   
               
               
                   
                 Exterior Height (front) 
                 15 11/16″ 
               
               
                   
                 Exterior Height (rear) 
                 16 1/2″ 
               
               
                   
                 Exterior Width 
                 29 4/5″ 
               
               
                   
                 Exterior Depth 
                 14 4/5″ 
               
               
                   
                 Cooking Cavity 
               
               
                   
                 Cavity Height 
                  8 2/5″ 
               
               
                   
                 Cavity Width 
                 19 2/7″ 
               
               
                   
                 Cavity Depth 
                 13 3/5″ 
               
               
                   
                   
               
             
          
         
       
     
     FIG. 4 is a schematic illustration of oven  10 , and particularly of halogen lamp cooking units  150  and  152  and microwave cooking unit  154  relative to cooking cavity  122 . As shown in FIG. 3, upper cooking unit  150  includes two halogen lamps  124  and  126  and cooking unit  152  includes one halogen lamp  156 . Lamps  124 ,  126 , and  156 , in an exemplary embodiment, are 1500 W halogen lamps having a color temperature of 2300K, output power of 4.5 kW with 7% in the light wave range of 0.4 um to 0.7 um, 20% to 25% in the light wave range less than 1.0 um, and 36% in the light wave range of 0.4 um to 1.35 um. Lamp  124  is referred to as the upper center lamp, and lamp  126  is referred to as the upper exterior lamp. Lamp  156  is referred to as the lower lamp. Glass plates  158  and  160  extend over cooking units  150  and  152  between lamps  124 ,  126 , and  156  and cavity  122 . Also, twist mesh screens  162  and  164  having an opening ratio of 80% are provided for additional protection. Additional details are provided below with respect to reflector  128 . A magnetron  166  of microwave cooking unit  154  is located on a side of cavity  122 . Magnetron  166 , in an exemplary embodiment, is rated at 1000 W and delivers 950 W into cavity  122 . 
     With respect to lower lamp  156 , and referring to FIG. 5, lamp  156  is located off center and at an angle relative to a bottom surface  172  of cavity  122 . Such location of lower lamp  156  results, for example, in lowering the temperature of the rollers on turntable  136 . 
     FIG. 6 is a schematic side illustration of reflector  128 . Reflector  128  includes angular side sections  180  and  182  and angular center sections  184  and  186 . The dimensions (in millimeters) indicated in FIG. 5 are exemplary and have been found suitable for at least one oven. By selecting the reflector dimensions as indicated in FIG. 5, upper lamps  124  and  126  are believed to provide more even cooking of items located on turntable  136 . 
     FIG. 7 illustrates a portion of turntable  136 . Turntable  136  has an open grille construction with a 70% energy transmission. Turntable  136  rotates at about 6 r.p.m. and has a diameter of about 11⅛″. Turntable  136  includes metal segments  190  with ceramic rollers  192 , one of which is illustrated within circle  194 . 
     FIG. 8 illustrates a damper  194  located below microwave cooking unit  154 . Damper  194  is open when in the microwave only mode to enable air to flow through cavity  122 . In the speed cooking and radiant only mode, damper  194  closes to prevent air from flowing in a reverse direction and back towards microwave cooking unit  154 . 
     FIG. 9 is a functional block diagram of oven  10 . As shown in FIG. 8, oven  10  includes a mounting system  200 , a structural system  202 , a control system  204 , an electrical system  206 , RF generation  208 , a component cooling system  210 , halogen lamps  212 , and a food containment system  214 . Various features of each system are indicated in FIG.  8 . Mounting system  200  is provided to enable mounting oven over the range. Mounting system  200  also provides connection with an exhaust to enable removal of fumes from over the cooktop into the exhaust. Structural system  202  generally refers to shell  120 , which provides an enclosure. Control system  204  includes an interface, i.e., keypads  112  and dial  48 , and also distributes power to the other oven systems. Electrical system  206  powers the control and safety devices. RF generation  208  is performed by magnetron  166 , and RF energy output by magnetron  166  is selectively used to cook food in food containment system. Component cooling system  210  is provided to cool the other system and to remove moisture from cavity  122 . Halogen lamps  212  generate light energy used for cooking food in food containment system  214 . 
     FIG. 10 is a schematic diagram of oven  10 . Power is provided to oven  10  via lines L 1 , L 2 , and N. Relays R 1 -R 13  are connected to a microprocessor or microcomputer which is programmed to control the opening and closing thereof. Lower lamp  156  is electrically connected to line L 1  via a thermal cut off  300 . Energization of lower lamp  156  is controlled by relays R 1  and R 2 . A triac is in series with relay R 1  to provide a soft start, as described below in more detail. Upper lamps  126  and  124  are connected to line L 2  via thermal cut offs  304  and  306 . Triacs  308  and  310  are in series with relay R 4 . 
     Relays R 1  and R 4  are air gap type relays, and are in series with triacs  302  and  308 , respectively. Relays R 1  and R 4  are closed in the soft start operation of respective lamps  124 ,  126 , and  156  to enable energization of triacs  302  and  308 . After completion of the soft start, relays R 1  and R 4  are open. Relays R 2 , R 3 , and R 6  are controlled by the micro computer to close after the soft start is completed to maintain energization of lamps  124 ,  126 , and  156  based on the particular power setting. 
     Oven  10  also includes an upper blower motor  312  and a lower blower motor  314  for cooling. A rectifier circuit  316  is provided for rectifying an AC input signal to a DC output signal to be supplied to a solenoid  317 . Solenoid  317 , when energized, closes damper  194 . Thermal cut outs  318  and  320  and a fuse  322  also are provided to protect oven components, e.g., from overheating or an overcurrent condition. Cooktop lamps  324  are electrically connected in series with a triac  326  and are provided for illuminating the cooktop. Rectifier circuit  316  and solenoid  317  may be replaced with a small synchronous motor. 
     A vent motor  328  having low, slow, and high speeds selectable via relays R 7 , R 8 , and R 9  is provided for removing fumes from over the cooktop. An oven lamp  330 , a fan motor  332 , and a turn table motor  334  are controlled by separate relays R 10 , R 11 , and R 12 . A primary interlock switch  336  is located in door  102  and prevents energization of cooking elements unless door  102  is closed. A relay R 13  controls energization of microwave cooking unit  154 . Microwave cooking unit  154  includes a high voltage transformer  338  which steps up the supply voltage from 120V to 2000V. A high voltage capacitor  340  and a high voltage diode  342  circuit steps up the voltage from transformer  338  from 2000V to 4000V. This high voltage is supplied to magnetron  166  and the output of magnetron  166  is supplied to a waveguide  344  which directs RF energy into cooking cavity  122 . As also shown in FIG. 9, oven  10  includes a door sensing switch  346  for sensing whether door  102  is opened, a humidity sensor  348  for sensing the humidity in cooking cavity  122 , a thermistor  350 , and a base thermostat  352 . 
     With respect to speed cooking operation of oven  10 , the microcomputer controls relays R 1 -R 6  and R 13  based on the power level either associated with the preprogrammed cooking program or manually entered. In the speed cooking mode, for example, if a power level  9  is selected, the upper exterior lamp  124  has a target on-time of 29 seconds of a 32 second duty cycle, upper center lamp  126  has a target on-time of 25 seconds of a 32 second duty cycle, lower lamp  156  has a target on-time of 29 seconds of a 32 second duty cycle, and magnetron  16  has a target on-time of 29 seconds of a 32 second duty cycle. A duty cycle of 32 seconds is selected for one particular implementation. However, other duty cycles could be utilized. Set forth below is a chart which sets forth the target on-times based on power level. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
               
               
                   
                 Upper 
                 Upper 
                   
                   
               
               
                   
                 Exterior 
                 Center 
                 Lower 
                   
               
               
                 Power Level 
                 Lamp 
                 Lamp 
                 Lamp 
                 Magnetron 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                 1 
                 3 
                 3 
                 3 
                 3 
               
               
                 2 
                 6 
                 5 
                 6 
                 6 
               
               
                 3 
                 10 
                 8 
                 10 
                 10 
               
               
                 4 
                 13 
                 11 
                 13 
                 13 
               
               
                 5 
                 16 
                 14 
                 16 
                 16 
               
               
                 6 
                 19 
                 16 
                 19 
                 19 
               
               
                 7 
                 22 
                 19 
                 22 
                 22 
               
               
                 8 
                 26 
                 22 
                 26 
                 26 
               
               
                 9 
                 29 
                 25 
                 29 
                 29 
               
               
                 10 
                 32 
                 27 
                 32 
                 32 
               
               
                   
               
             
          
         
       
     
     To increase lamp reliability, a soft start operation is used when energizing lamps  124 ,  126 , and  156 . Particularly, in accordance with the soft start operation, triacs  302 ,  308 , and  310  are utilized to delay lamp turn-on. For example, upper exterior lamp  126  and lower lamp  156  are delayed for one second from commanded turn-on to actual turn-on. Upper center lamp  124  is delayed for two seconds from commanded turn-on to actual turn-on. Therefore, the target turn-on times are different from the commanded on-times. Set forth below is a table containing the commanded on-times based on power level selected. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
               
               
                   
                 Upper 
                 Upper 
                   
                   
               
               
                   
                 Exterior 
                 Center 
                 Lower 
                   
               
               
                 Power Level 
                 Lamp 
                 Lamp 
                 Lamp 
                 Magnetron 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                 1 
                 4 
                 5 
                 4 
                 3 
               
               
                 2 
                 7 
                 7 
                 7 
                 6 
               
               
                 3 
                 11 
                 10 
                 11 
                 10 
               
               
                 4 
                 14 
                 13 
                 14 
                 13 
               
               
                 5 
                 17 
                 16 
                 17 
                 16 
               
               
                 6 
                 20 
                 18 
                 20 
                 19 
               
               
                 7 
                 23 
                 21 
                 23 
                 22 
               
               
                 8 
                 27 
                 24 
                 27 
                 26 
               
               
                 9 
                 30 
                 27 
                 30 
                 29 
               
               
                 10 
                 32 
                 29 
                 32 
                 32 
               
               
                   
               
             
          
         
       
     
     For example, if upper lamps  124  and  126  are to operate at power level  7 , then upper lamp  124  would be commanded to operate for 21 seconds and upper exterior lamp  126  would be commanded to operate for 23 seconds. Lamps  124  and  126  would be commanded to turn-on for 21 and 23 seconds, respectively, at the beginning of each 32 second duty cycle. Due to the soft-start delays, lamps  124  and  126  would actually be on for 19 seconds (lamp  124 ) and 22 seconds (lamp  126 ) of each 32 second duty cycle. 
     FIG. 11 is a timing diagram illustrating the state of lamps  124 ,  126 , and  156 , and magnetron  166 . In the example, refrigerated crescent rolls are to be cooked in accordance with the following: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Total Time: 
                 4:30 
               
               
                   
                 Upper Power Level: 
                 10 
               
               
                   
                 Lower Power Level: 
                 3 
               
               
                   
                 Microwave Power Level: 
                 3 
               
               
                   
                   
               
             
          
         
       
     
     As shown in FIG. 11, upper center lamp  124  is commanded on (dashed line) two seconds before it actually turns on (solid line). Lamp  124  is on for 27 seconds of each 32 second period. Upper exterior lamp  126  is always on during this period. Lower Lamp  156  is on one second after it is commanded to turn on, and is on for 10 seconds out of each 32 second period. Magnetron  166  has no delay between command and execution of on time, and is on for 10 seconds of each 32 second period. 
     An operator may enter control information, including a selected total cooking time and power levels for desired cooking units, as well as adjusting the cooking time and power level of the upper lamps, the lower lamp, and the microwave during operation. For manual entry of parameters to a control algorithm, MANUAL COOK control pad  64  is depressed and “Select COOK TIME” is displayed on alphanumeric display  50 . By rotating rotary dial  48  to increment or decrement the displayed cooking time, a COOK TIME may be selected and rotary dial  48  depressed to enter the selected COOK TIME. Once COOK TIME is entered, a message “Select UPPER POWER” is displayed as shown in FIG.  11 . Rotation of dial  48  then enables an operator to select the upper power level (clockwise rotation increases the power level and counter clockwise rotation decreases the power level). When dial  48  is pressed to enter the selection, a short beep sounds and “Select LOWER POWER” is displayed as shown in FIG.  13 . Dial rotation then alters the current lower power level, and when dial  48  is pressed to enter the selection, a short beep is sounded. Then, “Select MICRO POWER” is displayed as shown in FIG.  14 . Dial rotation now alters the microwave power level. When dial  48  is pressed to enter the selection, a short beep is sounded and the OVEN icon flashes and the SELECT icon is turned off. “ADJUST TIME or START” is then displayed as shown in FIG.  15 . The time may be adjusted or the START pad pressed. 
     A user may depress control panel POWER LEVEL pad  68  to adjust power levels of desired cooking units during operation of oven  10 . When the power level pad is pressed at an acceptable time during lightwave cooking, i.e., one or more of the lamps are energized, the cooking countdown continues and the UPL (FIG.  11 ), LPL (FIG. 12) and MPL (FIG. 13) displays appear. The same operation as described above is utilized except that after entering the new microwave power level, 2 short beeps are sounded and the countdown and UPL, LPL and MPL display continue for 2.0 seconds. After 2.0 seconds, the UPL, LPL and MPL displays are removed and only the cooking countdown continues. If the power level pad is pressed when it is not allowed to change/enter or recall the power level, a beep signal (0.5 seconds at 1000 hz) sounds and the message “POWER LEVEL MAY NOT BE CHANGED AT THIS TIME” scrolls on alphanumeric display  50 . After the scroll has completed, the previous foreground features return. If the power level pad is pressed at a time when a change/entry is allowed, but no dial rotation or entry occurs within 15 seconds, the UPL, LPL and MPL display are removed and alphanumeric display  50  returns to the cooking countdown. 
     FIG. 16 is a flow chart  400  illustrating process steps executed when adjusting the cook time during cooking operations. During cooking operations, a main cooking routine COOK is executed. If dial  48  is not moved  404 , the main cooking routine continues to be executed  406 . If dial  48  is moved  404 , then the microcomputer determines whether a time change can be made, e.g., is the time remaining within the change limits  408 . For example, if only 15 seconds remain in a cooking operation, no time change may be allowed to prevent an operator from shutting down a cooking operation by rotating dial  48  until zero is displayed, sometimes referred to as a “hard shutdown”, which may not be desirable. If the remaining time is not within the change limits, then the main cooking routine continues to be executed  406 . If the remaining time is within the change limits, then the micro computer determines whether dial  48  was moved clockwise  410 . If no (i.e., dial  48  was moved counterclockwise), then for each increment that dial  48  is moved, the cook time is decremented by one second  412 . If yes, then for each increment that dial  48  is moved, the cook time is incremented by one second  414 . 
     FIG. 17 is a flow chart illustrating process steps  450  for lamp power level control. Such control is used to control energization of lamps  124 ,  126 , and  156  (FIG.  9 ). More particularly, a main cooking routine  452  is executed during normal cooking operations. A power counter is incremented  454  for each one second interval, and the microcomputer then checks whether a power cycle is complete  456 . For example, and as explained above, each duty cycle has a duration of 32 seconds. If the duty cycle is complete, then the power counter is reset  458 . If the duty cycle is riot complete, or after resetting the counter, then the micro computer checks whether the power count is greater than the “on time”  460 . The “on time” is equal to the time corresponding to the selected power level for each lamp, as explained above. If the power count is greater than the “on time”, then the particular lamp is de-energized  462  and cooking continues with the main cooking routine  464 . If the power count is less than or equal to the “on time”, then the micro computer checks whether the lamp is already on  466 . If yes, then cooking operations continue  464 . If no, then the micro computer checks whether the soft start has been completed  468 . If the soft start has been completed, then operations continue with the cooking routine  464 . If soft start operations are not complete, then the soft start routine is called  470 . 
     FIG. 18 is a flow chart illustrating process steps for the soft start routine  500 . As explained above, the soft start for the halogen lamps is utilized to increase the lamp reliability. When routine  500  is called from the power level control routine  502 , the microcomputer increments a soft start counter  504 . The micro computer then determines whether the soft start is complete (e.g., depending on the lamp, the soft start has a duration of 1 or 2 seconds, as explained above). If soft start is complete, the microcomputer resets the soft start counter  508 , turns on the lamp control relay  510 , and turns off the lamp control triac  512 . Operations then proceed to the cooking routine  514 . If soft start is not complete, the micro computer turns on the, lamp control triac for a soft start count×10% of the line cycle  516 . Operations then proceed to the cooking routine. 
     The glass of oven door  26  (shown in FIG. 2) is very dark and does not enable visualization of food within cavity  122  (shown in FIG. 2) unless at least one of the Halogen lamps is on and sufficiently energized to illuminate cavity  122 . Therefore, in some cooking operations such as the microwave only mode of cooking or when radiant cooking at low power levels, and in order to visualize food in cooking cavity  122 , an operator may select the microwave button on control panel  40 . When this pad is selected during cooking, the microcomputer energizes upper center lamp  124  for four seconds at full power (i.e., power level  10 ), with a soft start, i.e., two seconds of soft start and two seconds of power level  10  energization for a total of four seconds, as described above. Lamp  124  illuminates the cooking cavity sufficiently so that an operator can visualize the food through window  30 . 
     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.