Induction heating conditioner

Abstract

The goal is to keep costs down while enabling detection of the position of the object being heated on the top plate without interrupting the heating process. [Solution] An induction heating cooker that inductively heats an object to be heated placed on a top plate, comprising an oscillation circuit including a sensor coil provided on the underside of the top plate, and a frequency detection circuit that detects the frequency of the signal output by the oscillation circuit, wherein the oscillation circuit comprises the sensor coil, a first capacitance element connected in series to a first terminal which is one end of the sensor coil, a second capacitance element which is a capacitance to ground and connected in series to a second terminal which is the other end of the sensor coil, and an inverting amplifier circuit using an operational amplifier, the input terminal of which is connected to the second terminal of the sensor coil and the output terminal of which is connected to the first terminal of the sensor coil via the first capacitance element.

Claims

1. This system uses induction heating to heat an object placed on a top plate. An oscillation circuit including a sensor coil provided on the back side of the top plate, The system includes a frequency detection circuit that detects the frequency of the signal output by the oscillation circuit, The aforementioned oscillator circuit The aforementioned sensor coil, A first capacitive element connected in series to the first terminal, which is one end of the sensor coil, A second capacitance element, which is a capacitance to ground, is connected in series to the second terminal, which is the other end of the sensor coil, An induction cooker having an inverting amplifier circuit using an operational amplifier, wherein an input terminal is connected to the second terminal of the sensor coil, and an output terminal is connected to the first terminal of the sensor coil via the first capacitive element.

2. The induction heating cooker according to claim 1, wherein the capacitance of the second capacitance element is greater than the capacitance of the first capacitance element.

3. The sensor coil further comprises a third capacitive element connected in series with the second terminal of the sensor coil. The induction heating cooker according to claim 1, wherein the input terminal of the inverting amplifier circuit is connected to the second terminal of the sensor coil via the third capacitance element.

4. The induction heating cooker according to claim 3, wherein the oscillation frequency of the oscillation circuit, determined by the inductance of the sensor coil and the capacitance of the first capacitance element, is higher than the polar frequency with a 180° phase change caused by the third capacitance element and the inverting amplifier circuit.

5. The aforementioned sensor coil is constructed by stacking two planar coils, each wound in opposite directions, spaced apart in the thickness direction, and connecting their inner ends. The first terminal is formed by the outer end of one of the planar coils. The induction heating cooker according to claim 1, wherein the second terminal is formed by the outer end of the other planar coil.

6. The aforementioned sensor coil is constructed by stacking two planar coils, each wound in the same direction, spaced apart in the thickness direction, and connecting their inner ends. The first terminal is formed by the outer end of one of the planar coils. The inner end of the one planar coil constitutes the second terminal, The induction cooker according to claim 1, wherein the outer end of the other planar coil is connected to ground.

7. The induction heating cooker according to claim 4 or 5, wherein the two planar coils are formed layer by layer on a printed circuit board.

8. The aforementioned sensor coil is constructed by overlapping two planar coils, each wound in the same direction, on the same plane such that their conductors are staggered, and connecting their inner ends. The first terminal is formed by the outer end of one of the planar coils. The induction heating cooker according to claim 1, wherein the second terminal is formed by the outer end of the other planar coil.

9. The induction heating cooker according to claim 7, wherein the two planar coils are formed in the same layer on the printed circuit board.

10. The induction heating cooker according to claim 1, wherein the sensor coil and the first capacitance element are selected such that the oscillation frequency of the oscillation circuit is 1 MHz or more and 10 MHz or less.

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