Patent ID: 6884977

Claim:
A variable-frequency inverter microwave ovens comprising: a magnetron that generates electromagnetic waves; a direct current (DC) voltage generator that rectifies and smooths a commercial alternating current (AC) voltage to generate a DC voltage, the commercial AC voltage being an inverter drive voltage; a switcher that performs a switching operation based on said DC voltage from said DC voltage generator to generate an AC voltage that drives said magnetron, said switcher including a plurality of switches that are turned on/off in response to said DC voltage from said DC voltage generator; variable-frequency controller that controls a switching frequency of said switcher according to a level of said DC voltage from said DC voltage generator to maintain said AC voltage from said switcher at a constant level; and magnetron drive voltage generator that converts said AC voltage from said switcher into a high-power DC voltage and transfers said converted DC voltage to said magnetron to drive said magnetron, said variable-frequency controller comprising: a DC voltage input node that receives said generated DC voltage; a current source that supplies a switching current for the switching operation of said switcher, based on said DC voltage inputted to said DC voltage input node; and a frequency generator that generates a predetermined frequency in accordance with an amount of said switching current supplied from said current source and outputs said predetermined frequency to said switcher.