Optimum time ratio control system for microwave oven including food

Abstract

An optimized time ratio control system for a microwave oven including a food surface browning system. The system is particularly useful where the available power is insufficient to operate both the browning system and the microwave energy generating system at the same time, and where the browning system has a relatively high thermal mass. A timing means is effective to establish successive time share cycles. Each time share cycle includes both a long browner ON time interval during which the browning system is energized at its full rated power level and an alternating interval, with the time ratio therebetween under user control. During the alternating intervals, the browning system and the microwave energy generating system are alternately energized, with the time ratio therebetween under the same user control. The overall relative apportionment to microwave cooking power is primarily determined during the alternating intervals with what is essentially duty cycle power level control employing power pulses of relatively short duration. The overall relative apportionment to browner power is primarily determined by the time intervals between the long browner ON time intervals, which between intervals are actually the alternating intervals. During those times during the alternating intervals when the browning system is energized, the browning system is at least kept warm. To compensate for a reduction in this 'keep warm' power as the relative apportionment to browner power is decreased during the alternating interval, such as by user control, the long browner ON time intervals are lengthened as the percentage of microwave power increases and the percentage of browning power decreases.