Magnetron with microprocessor based feedback control

摘要

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. The relatively fast feedback loop protects the circuitry against sudden current increases which might otherwise damage components before the microprocessor would have time to adjust the inverter operation.