Inductive cooking range and cooktop
First Claim
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1. An induction cooking apparatus, comprising:
- an electrical power source for providing, from an AC powerline, a DC power signal including a plurality of powerline half cycles;
a power inverter circuit, including an L/C network with a work coil coupled to said DC power signal for inducing heating current in metallic cookware and a switching means for intermittently connecting said L/C network with said DC power signal; and
an analog/digital control circuit coupled to said power inverter circuit, said analog/digital circuit including a user input for selecting a cooking temperature to be generated in said cookware, digital means generating a start signal for initiating operation of said power inverter circuit and for generating a stop signal for stopping operation of said power inverter circuit to define a period of operation of said power inverter circuit for generation of said cooking temperature, said digital means being coupled to said user input, and an analog circuit including gate means for generating gating pulses for operation of said power inverter circuit and feedback means coupled with said work coil for generating trigger signals to sustain generation of said gating pulses by said gate means after said power inverter circuit is started by said digital means.
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Abstract
An induction cooking apparatus and method for inductively heating cookware is provided. An analog/digital circuit, including a microprocessor, generates a plurality of gating pulses for operating the power inverter circuit and monitors the operation of the power inverter circuit. The microprocessor provides signals to start and stop the inverter circuit, and determines a period of uninterrupted power inverter circuit operation corresponding to a desired cooking temperature. Analog circuitry is provided for sustaining operation of the power inverter circuit after the power inverter circuit is started, and for compensating for variations in cookware materials.
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Citations
49 Claims
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1. An induction cooking apparatus, comprising:
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an electrical power source for providing, from an AC powerline, a DC power signal including a plurality of powerline half cycles; a power inverter circuit, including an L/C network with a work coil coupled to said DC power signal for inducing heating current in metallic cookware and a switching means for intermittently connecting said L/C network with said DC power signal; and an analog/digital control circuit coupled to said power inverter circuit, said analog/digital circuit including a user input for selecting a cooking temperature to be generated in said cookware, digital means generating a start signal for initiating operation of said power inverter circuit and for generating a stop signal for stopping operation of said power inverter circuit to define a period of operation of said power inverter circuit for generation of said cooking temperature, said digital means being coupled to said user input, and an analog circuit including gate means for generating gating pulses for operation of said power inverter circuit and feedback means coupled with said work coil for generating trigger signals to sustain generation of said gating pulses by said gate means after said power inverter circuit is started by said digital means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. An induction cooking apparatus having an inverter circuit comprising:
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a DC power supply for supplying a plurality of DC power half cycles from an AC powerline; an inverter circuit having an induction heating coil connected at one end to said DC power supply; an insulated gate bipolar transistor connected to the other end of said induction heating coil for conducting current of a first polarity through the heating coil; a diode connected in parallel with said transistor for conducting current of an opposite polarity through said induction heating coil; a zero crossing detector for generating zero crossing reference signals of the AC powerline; a microprocessor for supplying an initial inverter start signal to said inverter circuit, said microprocessor receiving said zero reference signals from said zero crossing detector and starting said inverter circuit at a low voltage generated by said DC power supply, selecting a number of powerline half cycles of inverter operation corresponding to a user-desired cooking temperature, and generating signals to interrupt operation of the inverter circuit to obtain the user-desired cooking temperature and to prevent unacceptable operation; and an analog circuit referenced to a voltage of said DC power supply for sensing the presence of cookware made of proper material, and for generating timing signals for sustaining compensated acceptable operation of said inverter circuit after said inverter circuit is started by said microprocessor. - View Dependent Claims (22, 23, 24, 25, 26)
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27. A method for heating metallic cookware with a work coil of an inductive heating device, comprising the steps of:
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generating a plurality of gating pulses for operating a power inverter circuit wherein a start pulse is generated by digital circuitry and subsequent pulses are generated by analog circuitry; starting said power inverter circuit at substantially zero applied voltages of powerline half cycles; adjusting pulse durations of a plurality of gating pulses during a start period to start said power inverter circuit at reduced power; determining during an initial portion of each powerline half cycle whether acceptable cookware is positioned near said work coil, wherein if after said first initial portion it is determined that acceptable cookware is present, then said power inverter circuit is operated through a remainder of said half cycle, and wherein if at the end of said first initial portion it is determined that no acceptable cookware is present, then said power inverter is commanded by said digital circuitry to stop; and adjusting pulse durations of said gating pulses supplied to said power inverter to compensate for cookware materials other than that of a predetermined standard for said cookware material. - View Dependent Claims (28, 29, 30, 31)
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32. In a cooking range having an induction heating burner connectable to any AC powerline including an inverter circuit for induction heating of a cooking utensil, and having a control circuit providing a range user with control of the induction burner, including the temperature generated by the cooking utensil, the improvement comprising:
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a digital control portion in communication with the range user providing a signal to start the inverter circuit with an initially reduced power output, a signal to interrupt operation of the inverter circuit in response to the absence of acceptable cookware at the burner, and signals to interrupt operation of the inverter circuit for variable intermittent times to control the temperature generated by the cookware and thereafter restart the inverter circuit during cooking, and an analog control portion generating triggering signals for continuous operation of the inverter circuit once started and in the absence of said interrupting signals from the digital control portion, and signals to compensate for cookware made of materials with differing electromagnetic properties during cooking and to interrupt, through said digital control portion, operation of said inverter circuit if no acceptable cookware is present at the burner. - View Dependent Claims (33, 34, 35)
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36. In an induction cooking apparatus, comprising a DC voltage source of a filtered plurality of AC powerline half cycles, a power inverter including an induction heating coil, a semiconductor switch providing, upon operation, an electric current path from said DC voltage source through said induction heating coil, and a control for switching said semiconductor switch ON and OFF to provide induction heating of cookware adjacent said induction heating coil, the improvement comprising a capacitor connected across said DC voltage source at the input of the induction heating coil, a pan-present circuit connected with said capacitor and generating a no pan voltage from the voltage of said capacitor including first window means for said no pan voltage permitting generation of said no pan voltage for only a small initial portion of each powerline half cycle following each zero voltage event, second window means permitting generation of said no pan voltage only during the OFF periods of said semiconductor switch, and an integrator to accumulate said no pan voltage only during a plurality of semiconductor switch OFF periods in the small initial portions of each powerline half cycle, said no pan voltage being thereby generated from recovery of said DC voltage source from electric current through the inductor heating coil and being applied to said control to interrupt operation of said semiconductor switch.
- 37. In an induction cooking apparatus including a DC power supply, a power inverter circuit including an induction heating coil and a switching circuit for providing electric current pulses from said DC power supply through said induction heating coil, and a control for operating said switching circuit and generating with said induction heating coil an induction heating field, the improvement wherein said switching circuit for said induction heating coil comprises an insulated gate bipolar transistor, and said control comprises analog circuitry connected with said induction heating coil to generate, once started, operating signals of variable duration for said insulated gate bipolar transistor based on the phase of a voltage of the induction heating coil.
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41. A method for heating metallic cookware using an interrupted flow of electric current through an inductive work coil, comprising
providing a signal to start the interrupted flow of electric current through said inductive work coil by the application of DC voltage pulses to the inductive work coil during a working period; -
developing phase differences of voltage across the induction work coil resulting from the interrupted flow of electric current, developing trigger signals from the phase differences of voltage across the induction work coil and generating therefrom electric current gating signals controlling the interrupted flow of electric current through the inductive work coil, said electric current gating signals providing a continuous interrupted flow of electric current through said inductive work coil so long as the DC voltage pulses are applied until a stop signal is provided. - View Dependent Claims (42, 43, 44, 45, 46, 47, 48, 49)
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Specification