Inverter-type microwave oven power supply

Claim 1

A power supply for a magnetron in a microwave oven, said magnetron having an anode and a cathode, said cathode having to be incandescent in order for the magnetron to effectively conduct anode current, said power supply comprising: rectifier means connected with an AC source and operable to provide periodic relatively low-magnitude low-frequency DC voltage pulses; inverter means powered by these DC voltage pulses and operable, but only when receiving an actuating input of trigger pulses synchronized with the DC voltage pulses, to provide at an inverter ouput intermittent periodic bursts of relatively low-magnitude high-frequency squarewave voltage, said squarewave voltage being of frequency substantially higher than that of said DC voltage pulses; transformer connected with said inverter ouput and operative to provide at a secondary output voltage-magnified transformations of said intermittent periodic bursts of relatively high-magnitude high-frequency squarewave voltage; a series-combination of an inductor and a capacitor connected across this secondary output, said series-combination being resonant at or near the frequency of said squarewave voltage and operative to provide at a tertiary output intermittent periodic bursts of relatively high-magnitude high-frequency sinusoidal voltage; rectifier and filter means connected with said tertiary output and operative to rectify and filter said bursts of high-magnitude high-frequency voltage, and to provide to the magnetron intermittent periodic low-frequency anode current pulses; conditioning means operative to provide heating power to said cathode, thereby to make it incandescent; and actuating means operative to provide said actuating input, but only after said conditioning means has provided said heating power for at least a minimum period of time.