# US 2014/0197160 A1 · Systems and methods for protecting switching elements in an induction heating system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0197160 A1 - Document ID: US20140197160A1 - Status: Published application - Kind: A1 - Application number: 13/740,520 - Filed: 2013-01-14 - Published: 2014-07-17 - Earliest claimed: 2013-01-14 - Assignees: General Electric Company - Applicants: General Electric Company - Inventors: Mingwei Shan; Gregory Francis Gawron, SR.; Daniel Vincent Brosnan; John Michael Kulp, JR. - Web page: https://patentgrep.com/patent/US20140197160A1 ## CPC - H05B 6/062: {for cooking plates or the like} - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL ## Abstract The present disclosure provides systems and methods for protecting switching elements in an induction heating system. A switching power loss associated with a switching element of the induction heating system can be calculated and an operating frequency of the induction heating system can be adjusted based upon the switching power loss. According to one aspect, the switching power loss can be classified into one of a plurality of threat zones based upon the magnitude of the switching power loss and the operating frequency can be adjusted based upon the threat zone into which the switching power loss is classified. According to another aspect, the switching power loss can be calculated based at least in part on a duty cycle of an output signal. The duty cycle of the output signal can provide an indication of the proximity of the operating frequency of the induction heating system to resonance. ## Claims ### Claim 1 A method of operating an induction heating system, the method comprising: calculating a switching power loss associated with a switching element of the induction heating system, the switching element being a component of a power supply circuit configured to supply a power signal to an induction heating coil of the induction heating system at an operating frequency; and adjusting the operating frequency of the induction heating system based at least in part on the switching power loss. ### Claim 2 (depends on 1) The method of claim 1, wherein the operating frequency of the induction heating system is adjusted such that the switching power loss is within a safe operating area associated with the switching element. ### Claim 3 (depends on 1) The method of claim 1, wherein adjusting the operating frequency of the induction heating system based at least in part on the switching power loss comprises: classifying the switching power loss into one of a plurality of threat zones based upon the magnitude of the switching power loss; and adjusting the operating frequency of the induction heating system based upon the threat zone into which the switching power loss is classified. ### Claim 4 (depends on 1) The method of claim 1, wherein calculating a switching power loss associated with a switching element of the induction heating system comprises: detecting a feedback signal in the induction heating system, the feedback signal being associated with a signal flowing through the induction heating coil; comparing the feedback signal to a reference signal to generate an output signal having a duty cycle, the duty cycle of the output signal being based at least in part on a percentage of the feedback signal that is greater or less than the reference signal, the duty cycle of the output signal corresponding to the proximity of the operating frequency to resonance; and calculating the switching power loss associated with the switching element based at least in part on the duty cycle of the output signal. ### Claim 5 (depends on 4) The method of claim 4, wherein the feedback signal comprises a voltage across a shunt resistor in a path of the signal flowing through the induction heating coil. ### Claim 6 (depends on 4) The method of claim 4, wherein calculating the switching power loss associated with the switching element based at least in part on the duty cycle of the output signal comprises: determining an input voltage of the power signal supplied to the induction heating coil; determining a coil current flowing through the induction heating coil; and calculating the switching power loss associated with the switching element based upon the input voltage, the coil current, and the duty cycle of the output signal. ### Claim 7 (depends on 6) The method of claim 6, wherein determining a coil current flowing through the induction heating coil comprises: determining a shunt current flowing through a shunt resistor, the shunt resistor being in a path of the signal flowing through the induction heating coil; and calculating the coil current flowing through the induction heating coil based upon the shunt current and the duty cycle of the output signal. ### Claim 8 (depends on 1) The method of claim 1, wherein adjusting the operating frequency of the induction heating system based at least in part on the switching power loss comprises: comparing the switching power loss to a first threshold loss value; and increasing the operating frequency of the induction heating system to a first frequency value when the switching power loss is greater than or equal to the first threshold loss value. ### Claim 9 (depends on 8) The method of claim 8, wherein adjusting the operating frequency of the induction heating system based at least in part on the switching power loss further comprises: comparing the switching power loss to a second threshold loss value when the switching power loss is less than the first threshold loss value, the second threshold loss value being less than the first threshold loss value; increasing the operating frequency of the induction heating system according to a frequency step table when the switching power loss is greater than or equal to the second threshold loss value but less than the first threshold loss value, the frequency step table providing a plurality of steps respectively corresponding to a plurality of operating frequency values; and setting a system flag to a first indicator level when the switching power loss is greater than or equal to the second threshold loss value. ### Claim 10 (depends on 9) The method of claim 9, wherein the operating frequency of the induction heating system is increased by two steps of the frequency step table when the switching power loss is greater than or equal to the second threshold loss value but less than the first threshold loss value. ### Claim 11 (depends on 9) The method of claim 9, wherein adjusting the operating frequency of the induction heating system based at least in part on the switching power loss further comprises: comparing the switching power loss to a third threshold loss value when the system flag is set to the first indicator level, the third threshold loss value being less than the second threshold loss value; setting the system flag to a second indicator level when the switching power loss is less than the third threshold loss value; and operating the induction heating system in a normal operating mode when the system flag is set to the second indicator level. ### Claim 12 An induction heating system comprising: an induction heating coil operable to inductively heat a load with a magnetic field; a power supply circuit configured to supply a power signal to the induction heating coil at an operating frequency, the power supply circuit including at least one switching element; a detector circuit configured to detect a feedback signal associated with a signal flowing through the induction heating coil, the detector circuit providing an output signal having a duty cycle, the duty cycle of the output signal being based at least in part on a percentage of the feedback signal that is greater or less than a reference signal, the duty cycle of the output signal corresponding to the proximity of the operating frequency to resonance of the induction heating system; and a control circuit configured to control the power supply circuit; wherein the control circuit is further configured to: calculate a switching power loss associated with the at least one switching element based at least in part on the duty cycle of the output signal; and adjust the operating frequency of the induction heating system based at least in part on the switching power loss. ### Claim 13 (depends on 12) The induction heating system of claim 12, wherein the control circuit is configured to adjust the operating frequency of the induction heating system such that the switching power loss is within a safe operating area associated with the switching element. ### Claim 14 (depends on 12) The induction heating system of claim 12, wherein the detector circuit comprises a shunt resistor in a path of the signal flowing through the induction heating coil, the feedback signal comprising a voltage across the shunt resistor. ### Claim 15 (depends on 12) The induction heating system of claim 12, wherein the control circuit is configured to calculate a switching power loss associated with the at least one switching element by performing operations comprising: determining an input voltage of the power signal supplied to the induction heating coil; determining a coil current, the coil current flowing through the induction heating coil; and calculating the switching power loss associated with the switching element based upon the input voltage, the coil current, and the duty cycle of the output signal. ### Claim 16 (depends on 12) The induction heating system of claim 12, wherein the control circuit is configured to adjust the operating frequency of the induction heating system based at least in part on the switching power loss by performing operations comprising: comparing the switching power loss to a first threshold loss value; and increasing the operating frequency of the induction heating system to a first frequency value when the switching power loss is greater than or equal to the first threshold loss value. ### Claim 17 (depends on 16) The induction heating system of claim 16, wherein the control circuit is configured to adjust the operating frequency of the induction heating system based at least in part on the switching power loss by performing further operations comprising: comparing the switching power loss to a second threshold loss value when the switching power loss is less than the first threshold loss value, the second threshold loss value being less than the first threshold loss value; increasing the operating frequency of the induction heating system according to a frequency step table when the switching power loss is greater than or equal to the second threshold loss value but less than the first threshold loss value, the frequency step table providing a plurality of steps respectively corresponding to a plurality of operating frequency values; and setting a system flag to a first indicator level when the switching power loss is greater than or equal to the second threshold loss value but less than the first threshold loss value. ### Claim 18 (depends on 17) The induction heating system of claim 17, wherein the control circuit is configured to adjust the operating frequency of the induction heating system based at least in part on the switching power loss by performing further operations comprising: comparing the switching power loss to a third threshold loss value when the system flag is set to the first indicator level, the third threshold loss value being less than the second threshold loss value; setting the system flag to a second indicator level when the switching power loss is less than the third threshold loss value; and operating the induction heating system in a normal operating mode when the system flag is set to the second indicator level. ### Claim 19 A method for protecting a switching element of a power supply circuit in an induction cooktop, the method comprising: calculating a switching power loss associated with the switching element; classifying the switching power loss into one of a plurality of threat zones based upon the magnitude of the switching power loss; and adjusting the operating frequency of the power supply circuit based upon the threat zone into which the switching power loss is classified. ### Claim 20 (depends on 19) The method of claim 19, wherein calculating a switching power loss associated with the switching element comprises: obtaining a feedback signal from the induction cooktop using a shunt resistor, the feedback signal related to a signal flowing through an inductive heating coil of the induction cooktop; comparing the feedback signal with a reference signal to obtain an output signal that has a duty cycle, the duty cycle of the output signal corresponding to the percentage of the feedback signal that is greater than the reference signal; and calculating the switching power loss associated with the switching element based at least in part on the duty cycle of the output signal.