Abstract: A microwave oven uses a full wave full bridge inverter for supplying energy to a cooking magnetron by way of a power transformer. The inverter is controlled by a microprocessor which acts upon a control circuit having an oscillator. Two feedback loops are provided for controlling the operation of the magnetron. A relatively slow feedback loop uses the microprocessor to adjust inverter operation in order to stabilize the magnetron power output. A relatively fast feedback loop senses current passing through a primary of a power transformer. A signal based on the sensed current is provided to a comparator and compared to a reference. If the signal from the current sensor indicates that the current has become excessive, the comparator generates a shutdown signal which will stop the generation of gating pulses to the transistor switches of the inverter.