US5111014A — Electromagnetic cooker including load control

Claim 1

Independent Claim 180 words

An electromagnetic cooking apparatus comprising: DC (direct current) power supply means for producing DC power from low-frequency AC (alternating current) power; DC-to-AC inverting means coupled to the DC power supply means and including a switching element and a heating coil, for inverting the DC power inputted from the DC power supply means into high-frequency AC power so as to heat an article by energizing the heating coil with the high-frequency AC power, thereby electromagnetically inducing eddy currents within the article; monitoring means for monitoring the DC power inputted into the DC/AC inverting means so as to produce a DC input power signal; setting means coupled to the DC/AC inverting means, for setting an ON-time duration of the switching element; and, judging means for judging whether or not the article to be heated corresponds to a heatable load electromagnetically loaded on the heating coil in response to the DC input power signal produced from the monitoring means after a predetermined time duration has passed from a beginning of the ON-time duration, thereby controlling the inverting operation of the DC/AC inverting means.

Claim 2

Dependent Claim 180 words

An electromagnetic cooking apparatus comprising: DC (direct current) power supply means for producing DC power from low-frequency AC (alternating current) power; DC-to-AC inverting means coupled to the DC power supply means and including a switching element and a heating coil, for inverting the DC power inputted from the DC power supply means into high-frequency AC power so as to heat an article by energizing the heating coil with the high-frequency AC power, thereby electromagnetically inducing eddy currents within the article; monitoring means for monitoring the DC power inputted into the DC/AC inverting means so as to produce a DC input power signal; setting means coupled to the DC/AC inverting means, for setting an ON-time duration of the switching element; and, judging means for judging whether or not the article to be heated corresponds to a heatable load electromagnetically loaded on the heating coil in response to the DC input power signal produced from the monitoring means after a predetermined time duration has passed from a beginning of the ON-time duration, thereby controlling the inverting operation of the DC/AC inverting means.

Claim 3

Dependent Claim 94 words

An electromagnetic cooking apparatus as claimed in claim 1, further comprising: input controlling means coupled to the DC/AC inverting means, for receiving switching conditions of the switching element to output an input controlling signal; and, ON/OFF-controlling means interposed between the input controlling means and DC power supply means, for turning ON/OFF the power suppply operation of the DC power supply means in response to the input controlling signal at a timing period defined by a time constant smaller than a thermal time constant determined by a heat capacity of a material of the article.

Claim 4

Dependent Claim 74 words

An electromagnetic cooking apparatus as claimed in claim 2, wherein said ON/OFF-controlling means includes: a triac interposed between the DC power supply means and an AC power source for supplying the low-frequency AC power; and, a trigger circuit for generating a trigger pulse in response to the input controlling signal, so as to trigger a ate of the triac, whereby the production of DC power by the DC power supply means is turned ON/OFF.

Claim 5

Dependent Claim 32 words

An electromagnetic cooking apparatus as claimed in claim 1, wherein said DC/AC inverting means further includes: a resonance capacitor series-connected to the switching element so as to form a series resonance circuit.

Claim 6

Dependent Claim 17 words

An electromagnetic cooking apparatus as claimed in claim 1, wherein said switching element is a bipolar transistor.

Claim 7

Dependent Claim 18 words

An electromagnetic cooking apparatus as claimed in claim 1, wherein said switching element is an insulated-gate bipolar transistor.

Claim 8

Dependent Claim 97 words

An electromagnetic cooking apparatus as claimed in claim 1, further comprising: an oscillation stopping timer for setting a stopping time period of the DC/AC inverting circuit so as to stop the inverting operation of the DC/AC inverting circuit for a predetermined stopping time period; and, a load detecting timer for producing a load detecting timer signal after the stopping time period, so as to prohibit judgment operation by the judging means for a predetermined prohibit time period, whereby the judgment operation by the judging means is carried out after the prohibit time period within the ON-time duration.

Claim 9

Dependent Claim 44 words

An electromagnetic cooking apparatus as claimed in claim 7, wherein said stopping time period is selected to be approximately 3 seconds, and said prohibit time period is selected to be about 10 milliseconds, and the ON-time duration is selected to be approximately 3.03 seconds.

Claim 10

Dependent Claim 49 words

An electromagnetic cooking apparatus as claimed in claim 1, wherein said DC/AC inverting means further includes: a pulse width modulation drive circuit for driving the switching element in a pulse width modulation mode, the pulse width of which is modulated, based upon the ON-time duration of the switching element.

Claim 11

Dependent Claim 27 words

An electromagnetic cooking apparatus (200) as claimed in claim 1, wherein said DC power supply means includes: a bridge circuit constructed of two diodes and two thyristors.

Claim 12

Dependent Claim 147 words

An electromagnetic cooking apparatus comprising: DC (direct current) power supply means for producing DC power from low-frequency AC (alternating current) power; DC-to-AC inverting means coupled to the DC power supply means and including a switching element and also a heating coil, for inverting the DC power inputted from the DC power supply means into high-frequency AC power so as to heat an article by energizing the heating coil with the high-frequency AC power, thereby electromagnetically inducing eddy currents within the article; monitoring means for monitoring switching conditions of the switching element so as to output a switching condition signal; and, ON/OFF-controlling means for turning ON/OFF power supply operation of the DC power supply means in response to the switching condition signal at a timing period defined by a time constant smaller than a thermal time constant determined by a heat capacity of a material of the article.

Claim 13

Dependent Claim 147 words

An electromagnetic cooking apparatus comprising: DC (direct current) power supply means for producing DC power from low-frequency AC (alternating current) power; DC-to-AC inverting means coupled to the DC power supply means and including a switching element and also a heating coil, for inverting the DC power inputted from the DC power supply means into high-frequency AC power so as to heat an article by energizing the heating coil with the high-frequency AC power, thereby electromagnetically inducing eddy currents within the article; monitoring means for monitoring switching conditions of the switching element so as to output a switching condition signal; and, ON/OFF-controlling means for turning ON/OFF power supply operation of the DC power supply means in response to the switching condition signal at a timing period defined by a time constant smaller than a thermal time constant determined by a heat capacity of a material of the article.

Claim 14

Dependent Claim 32 words

An electromagnetic cooking apparatus as claimed in claim 11, wherein said DC/AC inverting means further includes: a resonance capacitor series-connected to the switching element so as to form a series resonance circuit.

Claim 15

Dependent Claim 17 words

An electromagnetic cooking apparatus as claimed in claim 11, wherein said switching element is a bipolar transistor.

Claim 16

Dependent Claim 18 words

An electromagnetic cooking apparatus as claimed in claim 11, wherein said switching element is an insulated-gate bipolar transistor.

Claim 17

Dependent Claim 41 words

An electromagnetic cooking apparatus as claimed in claim 11, wherein said switching condition monitoring means includes: a short circuit current detecting circuit for detecting a short circuit current flowing through the switching element so as to produce the switching condition signal.

Claim 18

Dependent Claim 20 words

An electromagnetic cooking apparatus as claimed in claim 11, wherein said ON/OFF-controlling means is operated in a zerocross switching mode.

Claim 19

Dependent Claim 47 words

An electromagnetic cooking apparatus as claimed in claim 11, wherein said DC/AC inverting means further includes: a pulse width modulation drive circuit for driving the switching element in a pulse width modulation mode, the pulse width of which being modulated in response to the switching condition signal.

Claim 20

Dependent Claim 41 words

An electromagnetic cooking apparatus as claimed in claim 17, further comprising: control circuit selecting circuit for alternatively selecting one of said pulse width modulation circuit and ON/OFF-controlling means based upon the switching condition signal derived from the switching condition monitoring means.

Claim 21

Dependent Claim 55 words

An electromagnetic cooking apparatus as claimed in claim 17, further comprising: an output setting unit for setting an output of said DC/AC inverting means to produce an output setting signal; and, a control circuit selecting circuit for alternatively selecting one of said pulse width modulation circuit and ON/OFF-controlling means based upon the output setting signal.

Claim 22

Dependent Claim 58 words

An electromagnetic cooking apparatus as claimed in claim 17, further comprising: an input current detecting circuit for detecting an input current flowing through an AC power source for supplying the low-frequency AC power; and, a control circuit selecting circuit for alternatively selecting one of said pulse width modulation circuit and ON/OFF-controlling means based upon the output setting signal.

Claim 23

Dependent Claim 30 words

An electromagnetic cooking apparatus as claimed in claim 20, wherein said input current detecting circuit includes: a zerocross signal generator; an analog-to-digital converter, a 4-bit binary counter, and a decoder.

Claim 24

Dependent Claim 26 words

An electromagnetic cooking apparatus as claimed in claim 11, wherein said DC power supply means includes: a bridge circuit constructed of two diodes and two thyristors.

Claim 25

Dependent Claim 71 words

An electromagnetic cooking apparatus as claimed in claim 11, wherein said ON/OFF-controlling means includes: interposed between the DC power supply means and an AC power source for supplying low-frequency AC power; and, a trigger circuit for generating a trigger pulse in response to the input controlling signal so as to trigger a gate of the triac, whereby the production of DC power by the DC power supply means is turned ON/OFF.

Claim 26

Dependent Claim 41 words

An electromagnetic cooking apparatus as claimed in claim 11, wherein said low frequency of the AC power is selected from 50 Hz to 60 Hz approximately, whereas said high frequency of the AC power is selected to be approximately 25 KHz.

Claim 27

Dependent Claim 145 words

An electromagnetic cooking apparatus comprising: a DC (direct current) power supply means for producing DC power from low-frequency AC (alternating current) power; DC-to-AC inverting means coupled to the DC power supply means and including a switching element and heating coil, for inverting the DC power inputted from the DC power supply means into high-frequency AC power so as to heat an article by energizing the heating coil with the high-frequency AC power, thereby electromagnetically inducing eddy currents within the article; monitoring means for monitoring switching conditions of the switching element so as to output a switching condition signal; and, ON/OFF-controlling means for turning ON/OFF the inverting operation of the DC/AC inverting means in response to the switching condition signal at a timing period defined by a time constant less than a thermal time constant determined by a heat capacity of a material of the article.

Claim 28

Dependent Claim 145 words

An electromagnetic cooking apparatus comprising: a DC (direct current) power supply means for producing DC power from low-frequency AC (alternating current) power; DC-to-AC inverting means coupled to the DC power supply means and including a switching element and heating coil, for inverting the DC power inputted from the DC power supply means into high-frequency AC power so as to heat an article by energizing the heating coil with the high-frequency AC power, thereby electromagnetically inducing eddy currents within the article; monitoring means for monitoring switching conditions of the switching element so as to output a switching condition signal; and, ON/OFF-controlling means for turning ON/OFF the inverting operation of the DC/AC inverting means in response to the switching condition signal at a timing period defined by a time constant less than a thermal time constant determined by a heat capacity of a material of the article.

Claim 29

Dependent Claim 32 words

An electromagnetic cooking apparatus as claimed in claim 25, wherein said DC/AC inverting means further includes: a resonance capacitor series-connected to the switching element so as to form a series resonance circuit.

Claim 30

Dependent Claim 17 words

An electromagnetic cooking apparatus as claimed in claim 25, wherein said switching element is a bipolar transistor.

Claim 31

Dependent Claim 18 words

An electromagnetic cooking apparatus as claimed in claim 25, wherein said switching element is an insulated-gate bipolar transistor.

Claim 32

Dependent Claim 41 words

An electromagnetic cooking apparatus as claimed in claim 25, wherein said switching condition monitoring means includes: a short circuit current detecting circuit for detecting it short circuit current flowing through the switching element so as to produce the switching condition signal.

Claim 33

Dependent Claim 72 words

An electromagnetic cooking apparatus as claimed in claim 25, further comprising: a resonance voltage feedback circuit for receiving a resonance voltage form said switching element to output a resonance voltage feedback signal; and, an oscillator for oscillating a pulse width modulation signal in response to the resonance voltage feedback signal under the control of the ON/OFF-controlling means, the pulse width of which is modulated in response to the resonance voltage feedback signal.

Claim 34

Dependent Claim 42 words

An electromagnetic cooking apparatus as claimed in claim 25, further comprising: a control circuit selecting circuit for alternatively selecting one of said pulse width modulation circuit and ON/OFF-controlling means based upon the switching condition signal derived from the switching condition monitoring means.

Claim 35

Dependent Claim 23 words

An electromagnetic cooking apparatus as claimed in claim 25, wherein said DC power supply means includes a bridge circuit constructed of four diodes.

Claim 36

Dependent Claim 41 words

An electromagnetic cooking apparatus as claimed in claim 25, wherein said low frequency of the AC power is selected from 50 Hz to 60 Hz approximately, whereas said high frequency of the AC power is selected to be approximately 25 KHz.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1995-05-05	1995-11-04	1996-05-05	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1999-05-05	1999-11-04	2000-05-05	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2003-05-05	2003-11-04	2004-05-05	$7700.00	Window Closed / Lapsed

Electromagnetic cooker including load control

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