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(11) | EP 0 477 023 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Gas detection for microwave ovens |
| (57) In a gas detecting circuit of a microwave oven, current flowing through a gas sensor
(13) is constantly maintained even if the power supply voltage (Vcc) is varied. A
voltage across the gas sensor (13) varies with the resistance of the gas sensor (13),
depending upon an amount of gas produced in cooking food, and is supplied to a microcomputer
(1) to correctly set a cooking time of food. The microcomputer (1) controls the entire
cooking operation of food, and the circuit further comprises a power supply voltage
input unit (2) for supplying an input voltage to operate the microcomputer (1), a
gas sensor (13) for sensing an amount of gas produced in the microwave oven in cooking,
an amplifier (12) for amplifying the differential value between a first voltage (Vx)
divided from the power supply voltage and a second voltage (Vx′) having the same initial
potential as that of the first voltage (Vx), and allowing the output potential Ve
of the amplifier (12) to be varied on the basis of the variation of the resistance
of the gas sensor (13), and a filtering means (14) for filtering ripple components
of the output voltage (Ve). |