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Publication Date: 2014-Nov-14
Document File: 6 page(s) / 104K

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An embodiment of the present invention operates a system at its lowest continuous operating frequency. While operating in this manner, a relatively low power will be provided to the induction coil; however, even this low power may exceed the desired power demanded by the user for certain applications, for example, in cooking applications. Because this lower desired power cannot be achieved by the inverter in continuous mode, a cycling skipping or duty cycling mode must be offered to bring the average power output of the system lower. By utilizing cycle skipping or duty cycling, the output power of the system will be reduced by the laws of averaging power based on how many cycles are skipped and when, or the percent duty cycle of the system.

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The present invention is drawn to a method and control for adjusting power levels of an induction cooktop resonant power inverter for low power situations. Induction stoves are popular due to their advantages over other types of stoves, and have gained consumer favor in recent years though these stoves have been known for decades. Similarly to a traditional electric stove, the induction stove uses electricity to generate heat. Traditional electric stoves heat by use of a coil of metal or another resistive element through which an electric current is run. Induction stoves, however, generate an oscillating magnetic field that causes the cooking vessel, pot, pan, skillet, or other article in which food can be placed, to be heated itself. Unlike traditional electric stoves where a circular heating element is heated to then heat the cooking vessel placed thereon, normally no portion of the cook-top itself is directly heated by the induction heating element.

    The induction stove has a wire coil located beneath the cook-top, which receives an alternating electrical current, and thereby creates an oscillating magnetic field. When a cooking vessel comprised of ferromagnetic material is placed on the cooktop, the ferromagnetic material is heated by the oscillating magnetic field. This occurs by means of magnetic hysteresis loss in the ferromagnetic material as well as eddy currents created in the ferromagnetic material, which generate heat due to the electrical resistance of the material.

    Induction stovetops provide many advantages over other stove types. One advantage of induction stoves is that the surface of the cook-top is typically formed of a


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smooth material, such as ceramic glass, that is easy to clean and pleasant aesthetically. This is contrasted with gas stoves, which are difficult to clean due to their deep recesses for grates on which cooking vessels are placed and protrusions for the gas outlets. Induction cook-tops also provide a safety benefit over traditional stoves. The heating elements of both traditional electric and gas stoves remain hot and dangerous while heating and for a long period of time after the stove has been turned off.

    One problem users of heat induction cooking surface systems may encounter occurs when the power provided by the system is too high for the user's purpose. This over delivery of power occurs even when the power supplied by the induction coil of the system is relatively low or the lowest the system can provide. Embodiments of the present invention will allow a user to operate the system as the user wishes when the power demanded by the user is lower than the power provided by the system at its lowest continuous operating frequency. This problem is solved the present invention as described herein.

Figure 1 is an embodiment of a heat induction cooking surface.

Figure 2 is a...