Power control for cooking appliance with multiple heating units

An electric cooking appliance comprising:

• a plurality of heating units for heating cooking utensils placed in proximity thereto, said heating units being arranged in two groups, a first group adapted for energization by a first AC power signal and a second group adapted for energization by a second AC power signal 180.degree. out of phase relative to said first power signal, at least one of said first and second groups comprising more than one heating unit, the heating units of said first and second groups each being connected to a common neutral power line;
• user actuable input selection means for enabling the user to select one of a plurality of power settings for each of said heating units;
• switch means associated with each of said heating units for independently coupling the appropriate one of said first and second power signals to its associated heating unit, each of said switch means being switchable between a conductive state and a non-conductive state;
• said power control means including memory means for storing a plurality of power control words divided into a first set and a second set, said first and second sets of control words each containing a control word for each user selectable power setting, each of said control words comprising a plurality of bits, each bit having an ON state and an OFF state, the bit pattern for each control word defining the pulse repetition rate for the corresponding user selectable power setting;
• said second set comprising control words corresponding to each of said control words in said first set, and identical thereto, except that the bit patterns for said control words in said second set are offset relative to those in said first set to minimize the alignment of ON bits between words in said second set and words in said first set;
• said power control means including means for selecting control words from said first and second sets for each heating unit according to the user selected power settings for each heating unit and means for sequentially testing the state of each bit in the selected control;
• said power control means being operative to select control words for the selected power settings from said first and second sets so as to minimize the concurrent application of current pulses to heating units energized by the same power signal and to maximize the concurrent application of current pulses to heating units energized by different power signals, thereby minimizing peak current pulses in said common neutral line.