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US 3,943,317 AGranted
Microwave oven power supply circuit
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorSchun-ichi Nagamoto
Life of this patent
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Abstract
A microwave oven having a defrosting means including a bidirectional thyristor provided in a power source circuit and a control circuit for on-off controlling the thyristor, whereby microwave radiation can be intermittently irradiated on the foodstuff to obtain effective defrosting. Also, surge current at the time of start and end of the microwave oscillation is prevented.
Claims2
A microwave oven power supply circuit, comprising:
- a microwave oscillator;
- an A.C. source;
- a high voltage transformer having a primary winding coupled to said A.C. source and a secondary winding coupled to said microwave oscillator;
- a bidirectional thyristor coupled between said primary winding and said A.C. source;
- and
- a control circuit coupled to a gate electrode of said bidirectional thyristor for controlling the ON-OFF switching of said thyristor to thereby control the flow of current between said A.C. source and said transformer primary, said control circuit including:
- a rectifying circuit coupled to said A.C. source for rectifying and smoothing the A.C. source voltage to obtain a ripple-containing D.C. voltage as its output,
- a negative gate thyristor astable multivibrator circuit coupled to and controlled by the output of said rectifying circuit,
- a transistor circuit coupled to said astable multivibrator and to said A.C. source for superimposing said ripple-containing D.C. voltage onto said A.C. source voltage, and
- means coupling the output of said transistor circuit to said bidirectional thyristor gate electrode to turn said thyristor on at a phase angle of approximately 80.degree. relative to said A.C. source.
7 more elements
Dependencies are inferred from the claim text.