EP2939499B1 - An induction heating cooktop - Google Patents

An induction heating cooktop Download PDF

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Publication number
EP2939499B1
EP2939499B1 EP13818200.1A EP13818200A EP2939499B1 EP 2939499 B1 EP2939499 B1 EP 2939499B1 EP 13818200 A EP13818200 A EP 13818200A EP 2939499 B1 EP2939499 B1 EP 2939499B1
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EP
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Prior art keywords
current
power switch
induction coil
switch
vessel
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EP13818200.1A
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German (de)
French (fr)
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EP2939499A1 (en
Inventor
Namik Yilmaz
Hakan Suleyman YARDIBI
Metin ASTOPRAK
Metin OZTURK
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Arcelik AS
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Arcelik AS
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/06—Control, e.g. of temperature, of power
    • H05B6/062—Control, e.g. of temperature, of power for cooking plates or the like
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2213/00—Aspects relating both to resistive heating and to induction heating, covered by H05B3/00 and H05B6/00
    • H05B2213/03—Heating plates made out of a matrix of heating elements that can define heating areas adapted to cookware randomly placed on the heating plate
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2213/00—Aspects relating both to resistive heating and to induction heating, covered by H05B3/00 and H05B6/00
    • H05B2213/05—Heating plates with pan detection means

Definitions

  • the present invention relates to an induction heating cooktop wherein it is detected whether the vessel placed thereon is at the appropriate heating position.
  • the induction heating cooktop functions according to the principle of heating a cast iron or steel ferromagnetic cookware, for example a pot, with the magnetic field effect generated by the induction coil.
  • a cast iron or steel ferromagnetic cookware for example a pot
  • high amount of electric current is passed through the power switch (IGBT-Insulated Gate Bipolar Transistor, diode or MOSFET) on the circuit board.
  • IGBT-Insulated Gate Bipolar Transistor, diode or MOSFET the power switch
  • HBSR half bridge series resonant
  • SSQR single switch quasi-resonant
  • the single switch quasi-resonant circuits are preferred due to cost advantage; however, they operate in a narrower energy frequency range and can deliver power to the cookware only within a certain voltage and power range.
  • problems are encountered in detecting different kinds of cookware and the changes in position of the cookware on the cooktop burner. Furthermore, difficulties arise in detecting the position of the cookware in mains voltage fluctuations and at different temperature conditions.
  • multi coil - multi zone structure is used, heating can be maintained on the entire cooktop surface and flexibility is provided for the user.
  • induction coils of various shapes and sizes are situated on the cooktop surface.
  • the detection of the cookware position and furthermore the characteristic features like the diameter, type and the ferromagnetic properties during power transmittance to the cookware is quite critical for products wherein multi coil and also the single switch quasi-resonant circuits (SSQR) are used.
  • SSQR single switch quasi-resonant circuits
  • the European Patent Application No. EP2282606 relates to an induction apparatus control method.
  • the presence or absence of the vessel on the induction coil, the resistivity and the dimensions thereof are detected by comparing the resonance voltage with a predetermined fixed reference voltage in the control unit.
  • JP2011023163 a rice cooker is explained wherein existence or nonexistence of a pan on the induction heater or whether or not the pan is located at a designated position is detected under unstable power source voltage conditions.
  • the document GB2062985 discloses an induction heating cooktop comprising a bridge rectifier that converts the alternating current into direct current, a filter circuit disposed at the outlet of the bridge rectifier, a resonant circuit having an induction coil that provides the heating of the vessel placed thereon and a resonant capacitor connected in parallel to the induction coil, a power switch that drives the resonant circuit, a freewheeling diode connected in parallel to the power switch and providing continuity of the induction coil current in the resonant circuit during the non-conduction times of the power switch, a collector node whereon resonance voltage is generated, and a control unit that regulates the operation of the power switch.
  • the aim of the present invention is the realization of an induction heating cooktop wherein the position of the vessel placed on the induction coil is detected precisely under variable mains input voltage and temperature conditions.
  • the induction heating cooktop realized in order to attain the aim of the present invention, explicated in the first claim and the respective claims thereof, comprises a bridge rectifier that converts the alternating current into direct current, a filter circuit disposed at the outlet of the bridge rectifier, a resonant circuit having an induction coil that provides the heating of the vessel placed thereon and a resonant capacitor connected in parallel to the induction coil, a power switch that drives the resonant circuit, a freewheeling diode connected in parallel to the power switch and providing continuity of the induction coil current in the resonant circuit during the non-conduction times of the power switch, a collector node whereon resonance voltage is generated, a control unit that regulates the operation of the power switch, and a current detection circuit connected in series to the power switch and the freewheeling diode, wherein the current detection circuit converts the switch current passing through the power switch and the freewheeling diode into voltage data and thus provides the monitoring of the switch current, and the control unit calculates the diode conduction
  • the current detection circuit is formed of a current detection resistor connected in series to the power switch and the freewheeling diode or formed of a current transformer connected in series to the freewheeling diode and a current detection resistor connected in parallel to the secondary side of the current transformer.
  • a comparator connected in parallel to the terminals of the current detection resistor generates square wave output signals with periods equal to the diode conduction times by detecting the times of the switch current passes through the freewheeling diode and the power switch.
  • the control unit determines the absence of the vessel on the induction coil or that the vessel has been slid from over the induction coil more than permitted and interrupts the induction coil current if the periods, that are equal to the diode conduction times, of the output signals of the comparator are greater than the threshold output signal periods recorded in its memory.
  • the induction heating cooktop (1) comprises a bridge rectifier (2) that converts the alternating current received from the mains into direct current, a high frequency filter circuit (3) disposed at the outlet of the bridge rectifier (2) comprising a DC-line inductor and a DC-line capacitor and delivering DC voltage within a certain frequency range by filtering the voltage generated at the DC-line, a resonant circuit (6) having an induction coil (4) that provides the heating of the vessel (K) placed thereon and a resonant capacitor (5) connected in parallel to the induction coil (4), a power switch (7), for example an IGBT (Insulated Gate Bipolar Transistor), having a collector and an emitter, that drives the resonant circuit (6), that is in conducting state in the turned-off position, providing the resonant capacitor (5) to be charged during the turn-off time, that interrupts conduction in the turned-on position, providing the resonant capacitor (5) to be discharged during the non-conduction time and that provides the energy to be delivered
  • the conduction times wherein the power switch (7) is in the turned-off position are determined by the power scale setting made by the user.
  • the non-conduction times wherein the power switch (7) is in the turned-on position is determined by the control unit (11) depending on the characteristic features of the vessel (K) placed on the induction coil (4), alignment of the vessel (K) on the induction coil (4), AC mains voltage conditions and the temperature of the vessel (K).
  • the resonant capacitor (5) is first charged then discharged during non-conduction times of the power switch (7) and the coil current (I L ) passes through the freewheeling diode (8) while the resonant capacitor (5) is being discharged.
  • Resonance voltage (Vce) is generated at the collector node (9) and energy is transferred from the induction coil (4) to the vessel (K).
  • the power switch (7) is changed from the turned-on position to the turned-off position, in other words from the non-conducting state to the conducting state and energy is stored in the induction coil (4) during the conduction time while the power switch (7) is in the turned-off position.
  • the induction heating cooktop (1) of the present invention comprises a current detection circuit (12) connected in series to the power switch (7) and the freewheeling diode (8), that converts the switch current (Is) passing through the power switch (7) and the freewheeling diode (8) into voltage data in the non-conduction times wherein the power switch (7) is in the turned-on position and power is transferred from the induction coil (4) to the vessel (K) and thus provides the monitoring of the switch current (Is), and further comprises the control unit (11) that calculates the diode conduction time (Td) of the switch current (Is) passing through the freewheeling diode (8) by monitoring the switch current (Is) converted into voltage data and received from the current detection circuit (12) and that compares the diode conduction time (Td) with a threshold diode conduction time (Td-threshold) recorded in its memory, thus determining whether or not the vessel (K) is present on the induction coil (4) or whether alignment of the vessel (K) on the in
  • the control unit (11) detects the switch current (Is) passing through the power switch (7) and the freewheeling diode (8) as converted into voltage data by means of the current detection circuit (12) and calculates the diode conduction time (Td) wherein the switch current (Is) passes through the freewheeling diode (8) in the non-conduction times of the power switch (7) by monitoring the switch current (Is). According to the diode conduction time (Td), the control unit (11) determines whether or not the vessel (K) is present on the induction coil (4) and if the vessel (K) is present on the induction coil (4) determines whether the vessel (K) is in the appropriate position, in other words whether the vessel (K) is aligned with the induction coil (4).
  • the diode conduction time (Td) is dependent on the discharging time of the resonant capacitor (5).
  • the discharging time of the resonant capacitor (5) changes depending on the position of the vessel (K) placed on the induction coil (4). For example, resistance on the induction coil (4) decreases as the vessel (K) is moved from its aligned position on the induction coil (4) and the resonant capacitor (5) short-circuits by discharging rapidly.
  • the rapid discharging of the resonant capacitor (5) increases the diode conduction time (Td) and the control unit (11) decides that the vessel (K) is not present on the induction coil (4) (the vessel (K) is lifted) or that the vessel (K) is not aligned with the induction coil (4) (the vessel (K) is slid more than permitted) and interrupts current transmission to the induction coil (4).
  • the current detection circuit (12) comprises a current detection resistor (13) that is connected in series to the power switch (7) and the freewheeling diode (8) and that converts the switch current (Is) into voltage data ( Figure 1 ).
  • the control unit (11) receives the voltage data defining the switch current (Is) from the terminals of the current detection resistor (13).
  • the current detection circuit (12) comprises a current transformer (14) connected in series to the power switch (7) and the freewheeling diode (8) and decreasing the switch current (Is) to a level that can be detected by the control unit (11) and furthermore comprises the current detection resistor (13) connected in parallel to the secondary side of the current transformer (14) ( Figure 2 ).
  • the induction cooking cooktop (1) comprises a comparator (15) that is connected in parallel to the current detection resistor (13), that generates square wave output signals (S1) by detecting the times (Td) the switch current (Is) passes through the freewheeling diode (8) and the power switch (7), and thus that provides easy monitoring of the switch current (Is).
  • the comparator In the non-conduction (turned-on) times of the power switch (7) when the induction coil (4) transfers energy to the vessel (K), the comparator (15) generates square wave output signals (S1) with a low supply voltage (Vcc) amplitude such as 5V and with periods of the times between the points where the switch current (Is) passes through the freewheeling diode (8) being equal to the diode conduction times (Td) ( Figure 3 ).
  • the control unit (11) determines that the vessel (K) is not present on the induction coil (4) or the vessel (K) is not appropriately aligned on the induction coil (4), in other words, that the vessel (K) is "slid” or “lifted”, if the output signal (S1) time (Td) of the comparator (15) is greater than the threshold signal time (Td-threshold) (Td>Td-threshold) recorded in its memory and interrupts the current of the induction coil (4).
  • induction heating cooktops (1) called “flexi-zone” or “multi-zone”, having more than one induction coil (4), each driven by a single power switch (7), the presence or absence of the vessel (K) on the induction coil (4) and whether or not the vessel (K) is in the appropriate position is determined and energy is transferred to the vessel (K) in a safe manner under variable mains voltage and temperature conditions.
  • the power switch (7) and the other electronic circuit elements are prevented from being damaged.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Induction Heating Cooking Devices (AREA)
  • Cookers (AREA)

Description

  • The present invention relates to an induction heating cooktop wherein it is detected whether the vessel placed thereon is at the appropriate heating position.
  • The induction heating cooktop functions according to the principle of heating a cast iron or steel ferromagnetic cookware, for example a pot, with the magnetic field effect generated by the induction coil. In order to drive the induction coils that generate magnetic fields, high amount of electric current is passed through the power switch (IGBT-Insulated Gate Bipolar Transistor, diode or MOSFET) on the circuit board. In the state of the art, half bridge series resonant (HBSR) circuits formed by using two power switches and two resonant capacitors, and single switch quasi-resonant (SSQR) circuits formed by one power switch and one resonant capacitor are used for driving a single induction coil. The single switch quasi-resonant circuits (SSQR) are preferred due to cost advantage; however, they operate in a narrower energy frequency range and can deliver power to the cookware only within a certain voltage and power range. In induction heating cooktops wherein the single switch quasi-resonant circuits (SSQR) are used, problems are encountered in detecting different kinds of cookware and the changes in position of the cookware on the cooktop burner. Furthermore, difficulties arise in detecting the position of the cookware in mains voltage fluctuations and at different temperature conditions. In some induction heating cooktops, multi coil - multi zone structure is used, heating can be maintained on the entire cooktop surface and flexibility is provided for the user. In this type of induction heating cooktops, induction coils of various shapes and sizes are situated on the cooktop surface. Under variable mains voltage, input voltage depending on the power setting and at variable temperature conditions, the detection of the cookware position and furthermore the characteristic features like the diameter, type and the ferromagnetic properties during power transmittance to the cookware is quite critical for products wherein multi coil and also the single switch quasi-resonant circuits (SSQR) are used. The cookware cannot be heated efficiently and the electronic circuit controlling the induction coil can be damaged if sliding or lifting of the cookware from the cooktop cannot be properly detected.
  • The European Patent Application No. EP2282606 relates to an induction apparatus control method. The presence or absence of the vessel on the induction coil, the resistivity and the dimensions thereof are detected by comparing the resonance voltage with a predetermined fixed reference voltage in the control unit.
  • In the European Patent No. EP1629698 , an induction cooking system comprising a power inverter, a microprocessor, a protection circuit and a pan detection circuit is explained.
  • In the Japanese patent application no. JP4371108 , an induction heating cooking device that comprises a cookware detection circuit is explained.
  • In the Japanese patent application no. JP2011023163 , a rice cooker is explained wherein existence or nonexistence of a pan on the induction heater or whether or not the pan is located at a designated position is detected under unstable power source voltage conditions.
  • In the Japanese Patent Application No. JP2007066837 , a rice cooker is explained wherein the presence of kitchenware such as spoon, knife on the induction heater is detected under fluctuating power source voltage conditions.
  • The document GB2062985 discloses an induction heating cooktop comprising a bridge rectifier that converts the alternating current into direct current, a filter circuit disposed at the outlet of the bridge rectifier, a resonant circuit having an induction coil that provides the heating of the vessel placed thereon and a resonant capacitor connected in parallel to the induction coil, a power switch that drives the resonant circuit, a freewheeling diode connected in parallel to the power switch and providing continuity of the induction coil current in the resonant circuit during the non-conduction times of the power switch, a collector node whereon resonance voltage is generated, and a control unit that regulates the operation of the power switch.
  • The aim of the present invention is the realization of an induction heating cooktop wherein the position of the vessel placed on the induction coil is detected precisely under variable mains input voltage and temperature conditions.
  • The induction heating cooktop realized in order to attain the aim of the present invention, explicated in the first claim and the respective claims thereof, comprises a bridge rectifier that converts the alternating current into direct current, a filter circuit disposed at the outlet of the bridge rectifier, a resonant circuit having an induction coil that provides the heating of the vessel placed thereon and a resonant capacitor connected in parallel to the induction coil, a power switch that drives the resonant circuit, a freewheeling diode connected in parallel to the power switch and providing continuity of the induction coil current in the resonant circuit during the non-conduction times of the power switch, a collector node whereon resonance voltage is generated, a control unit that regulates the operation of the power switch, and a current detection circuit connected in series to the power switch and the freewheeling diode, wherein the current detection circuit converts the switch current passing through the power switch and the freewheeling diode into voltage data and thus provides the monitoring of the switch current, and the control unit calculates the diode conduction time of the switch current passing through the freewheeling diode by monitoring the switch current and compares the diode conduction time with a threshold diode conduction time recorded in its memory, thus determining whether or not the vessel is present on the induction coil or whether alignment of the vessel on the induction coil is appropriate.
  • The current detection circuit is formed of a current detection resistor connected in series to the power switch and the freewheeling diode or formed of a current transformer connected in series to the freewheeling diode and a current detection resistor connected in parallel to the secondary side of the current transformer.
  • In an embodiment of the present invention, a comparator connected in parallel to the terminals of the current detection resistor generates square wave output signals with periods equal to the diode conduction times by detecting the times of the switch current passes through the freewheeling diode and the power switch.
  • The control unit determines the absence of the vessel on the induction coil or that the vessel has been slid from over the induction coil more than permitted and interrupts the induction coil current if the periods, that are equal to the diode conduction times, of the output signals of the comparator are greater than the threshold output signal periods recorded in its memory.
  • In the induction heating cooktop of the present invention, whether or not the vessel is present on the induction coil and the alignment position on the induction coil is detected reliably all through the heating process under unfavorable conditions where the AC mains input voltage is variable.
  • The induction heating cooktop realized in order to attain the aim of the present invention is illustrated in the attached figures, where:
    • Figure 1 - is the schematic view of the control circuit of an induction heating cooktop.
    • Figure 2 - is the schematic view of the control circuit of an induction heating cooktop in an embodiment of the present invention.
    • Figure 3 - is the graphic showing the change, with respect to time, in the switch current passing through the power switch and the freewheeling diode and change in the voltage generated on the power switch in the control circuit of the induction heating cooktop.
    • Figure 4 - is the graphic showing the output signals of the comparator used in the control circuit of the induction heating cooktop.
  • The elements illustrated in the figures are numbered as follows:
    1. 1. Induction heating cooktop
    2. 2. Bridge rectifier
    3. 3. Filter circuit
    4. 4. Induction coil
    5. 5. Resonant capacitor
    6. 6. Resonant circuit
    7. 7. Power switch
    8. 8. Freewheeling diode
    9. 9. Collector node
    10. 10. Drive circuit
    11. 11. Control unit
    12. 12. Current detection circuit
    13. 13. Current detection resistor
    14. 14. Current transformer
    15. 15. Comparator
  • The induction heating cooktop (1) comprises a bridge rectifier (2) that converts the alternating current received from the mains into direct current, a high frequency filter circuit (3) disposed at the outlet of the bridge rectifier (2) comprising a DC-line inductor and a DC-line capacitor and delivering DC voltage within a certain frequency range by filtering the voltage generated at the DC-line, a resonant circuit (6) having an induction coil (4) that provides the heating of the vessel (K) placed thereon and a resonant capacitor (5) connected in parallel to the induction coil (4), a power switch (7), for example an IGBT (Insulated Gate Bipolar Transistor), having a collector and an emitter, that drives the resonant circuit (6), that is in conducting state in the turned-off position, providing the resonant capacitor (5) to be charged during the turn-off time, that interrupts conduction in the turned-on position, providing the resonant capacitor (5) to be discharged during the non-conduction time and that provides the energy to be delivered from the induction coil (4) to the vessel (K), a freewheeling diode (8) connected in parallel to the power switch (7) and providing continuity of the induction coil (4) current (IL) (will be referred to as "coil current (IL)" hereinafter) in the resonant circuit (6) during the non-conduction (turn-on) times of the power switch (7), a collector node (9) whereon resonance voltage (Vce) or in other words the collector-emitter voltage of the power switch (7) is generated during the non-conduction (turn-on) times of the power switch (7), a drive circuit (10) providing the power switch (7) to be driven with the drive voltage at the required level and a control unit (11), for example a microcontroller, that regulates the operation of the power switch (7) by controlling the drive circuit (10).
  • During the heating process implemented in the induction heating cooktop (1), the conduction times wherein the power switch (7) is in the turned-off position are determined by the power scale setting made by the user. The non-conduction times wherein the power switch (7) is in the turned-on position is determined by the control unit (11) depending on the characteristic features of the vessel (K) placed on the induction coil (4), alignment of the vessel (K) on the induction coil (4), AC mains voltage conditions and the temperature of the vessel (K). The resonant capacitor (5) is first charged then discharged during non-conduction times of the power switch (7) and the coil current (IL) passes through the freewheeling diode (8) while the resonant capacitor (5) is being discharged. Resonance voltage (Vce) is generated at the collector node (9) and energy is transferred from the induction coil (4) to the vessel (K). At the lowermost level of the resonance voltage (Vce), the power switch (7) is changed from the turned-on position to the turned-off position, in other words from the non-conducting state to the conducting state and energy is stored in the induction coil (4) during the conduction time while the power switch (7) is in the turned-off position.
  • The induction heating cooktop (1) of the present invention comprises a current detection circuit (12) connected in series to the power switch (7) and the freewheeling diode (8), that converts the switch current (Is) passing through the power switch (7) and the freewheeling diode (8) into voltage data in the non-conduction times wherein the power switch (7) is in the turned-on position and power is transferred from the induction coil (4) to the vessel (K) and thus provides the monitoring of the switch current (Is), and further comprises the control unit (11) that calculates the diode conduction time (Td) of the switch current (Is) passing through the freewheeling diode (8) by monitoring the switch current (Is) converted into voltage data and received from the current detection circuit (12) and that compares the diode conduction time (Td) with a threshold diode conduction time (Td-threshold) recorded in its memory, thus determining whether or not the vessel (K) is present on the induction coil (4) or whether alignment of the vessel (K) on the induction coil (4) is appropriate.
  • The control unit (11) detects the switch current (Is) passing through the power switch (7) and the freewheeling diode (8) as converted into voltage data by means of the current detection circuit (12) and calculates the diode conduction time (Td) wherein the switch current (Is) passes through the freewheeling diode (8) in the non-conduction times of the power switch (7) by monitoring the switch current (Is). According to the diode conduction time (Td), the control unit (11) determines whether or not the vessel (K) is present on the induction coil (4) and if the vessel (K) is present on the induction coil (4) determines whether the vessel (K) is in the appropriate position, in other words whether the vessel (K) is aligned with the induction coil (4).
  • The diode conduction time (Td) is dependent on the discharging time of the resonant capacitor (5). The discharging time of the resonant capacitor (5) changes depending on the position of the vessel (K) placed on the induction coil (4). For example, resistance on the induction coil (4) decreases as the vessel (K) is moved from its aligned position on the induction coil (4) and the resonant capacitor (5) short-circuits by discharging rapidly. The rapid discharging of the resonant capacitor (5) increases the diode conduction time (Td) and the control unit (11) decides that the vessel (K) is not present on the induction coil (4) (the vessel (K) is lifted) or that the vessel (K) is not aligned with the induction coil (4) (the vessel (K) is slid more than permitted) and interrupts current transmission to the induction coil (4).
  • In an embodiment of the present invention, the current detection circuit (12) comprises a current detection resistor (13) that is connected in series to the power switch (7) and the freewheeling diode (8) and that converts the switch current (Is) into voltage data (Figure 1). The control unit (11) receives the voltage data defining the switch current (Is) from the terminals of the current detection resistor (13).
  • In another embodiment of the present invention, the current detection circuit (12) comprises a current transformer (14) connected in series to the power switch (7) and the freewheeling diode (8) and decreasing the switch current (Is) to a level that can be detected by the control unit (11) and furthermore comprises the current detection resistor (13) connected in parallel to the secondary side of the current transformer (14) (Figure 2).
  • In another embodiment of the present invention, the induction cooking cooktop (1) comprises a comparator (15) that is connected in parallel to the current detection resistor (13), that generates square wave output signals (S1) by detecting the times (Td) the switch current (Is) passes through the freewheeling diode (8) and the power switch (7), and thus that provides easy monitoring of the switch current (Is).
  • In the non-conduction (turned-on) times of the power switch (7) when the induction coil (4) transfers energy to the vessel (K), the comparator (15) generates square wave output signals (S1) with a low supply voltage (Vcc) amplitude such as 5V and with periods of the times between the points where the switch current (Is) passes through the freewheeling diode (8) being equal to the diode conduction times (Td) (Figure 3).
  • The control unit (11) determines that the vessel (K) is not present on the induction coil (4) or the vessel (K) is not appropriately aligned on the induction coil (4), in other words, that the vessel (K) is "slid" or "lifted", if the output signal (S1) time (Td) of the comparator (15) is greater than the threshold signal time (Td-threshold) (Td>Td-threshold) recorded in its memory and interrupts the current of the induction coil (4).
  • By means of the present invention, in induction heating cooktops (1) called "flexi-zone" or "multi-zone", having more than one induction coil (4), each driven by a single power switch (7), the presence or absence of the vessel (K) on the induction coil (4) and whether or not the vessel (K) is in the appropriate position is determined and energy is transferred to the vessel (K) in a safe manner under variable mains voltage and temperature conditions. The power switch (7) and the other electronic circuit elements are prevented from being damaged.
  • It is to be understood that the present invention is not limited by the embodiments disclosed above and a person skilled in the art can easily introduce different embodiments. These should be considered within the scope of the protection postulated by the claims of the present invention.

Claims (6)

  1. An induction heating cooktop (1) comprising a bridge rectifier (2) that converts the alternating current into direct current, a filter circuit (3) disposed at the outlet of the bridge rectifier (2), a resonant circuit (6) having an induction coil (4) that provides the heating of the vessel (K) placed thereon and a resonant capacitor (5) connected in parallel to the induction coil (4), a power switch (7) that drives the resonant circuit (6), a freewheeling diode (8) connected in parallel to the power switch (7) and providing continuity of the induction coil (4) current in the resonant circuit (6) during the non-conduction times of the power switch (7), a collector node (9) whereon resonance voltage (Vce) is generated, and a control unit (11) that regulates the operation of the power switch (7), the induction heating cooktop (1) being characterized in that - the induction heating cooktop (1) comprises a current detection circuit (12) connected in series to the power switch (7) and the freewheeling diode (8), - the current detection circuit (12) converts the switch current (Is) passing through the power switch (7) and the freewheeling diode (8) into voltage data and thus provides the monitoring of the switch current (Is), and - the control unit (11) calculates the diode conduction time (Td) of the switch current (Is) passing through the freewheeling diode (8) by monitoring the switch current (Is) and compares the diode conduction time (Td) with a threshold diode conduction time recorded in its memory, thus determining whether or not the vessel (K) is present on the induction coil (4) or whether alignment of the vessel (K) on the induction coil (4) is appropriate.
  2. An induction heating cooktop (1) as in Claim 1, characterized in that the current detection circuit (12) comprising a current detection resistor (13) that is connected in series to the power switch (7) and the freewheeling diode (8) and that converts the switch current (Is) into voltage data.
  3. An induction heating cooktop (1) as in claim 1, characterized in that the current detection circuit (12) comprises a current transformer (14) connected in series to the power switch (7) and the freewheeling diode (8) and decreasing the switch current (Is), the current detection circuit (12) further comprising a current detection resistor (13) connected in parallel to the current transformer (14).
  4. An induction cooking cooktop (1) as in claim 2 or claim 3 characterized in that a comparator (15) that is connected in parallel to the current detection resistor (13) and that generates square wave output signals (S1) by detecting the times (Td) the switch current (Is) passes through the freewheeling diode (8) and the power switch (7).
  5. An induction heating cooktop (1) as in Claim 4, characterized in that the comparator (15) that generates square wave output signals (S1) with periods being equal to the diode conduction times (Td).
  6. An induction heating cooktop (1) as in Claim 5, characterized in that the control unit (11) determines that the vessel (K) is not present on the induction coil (4) or the vessel (K) is not appropriately aligned on the induction coil (4) and interrupts the current of the induction coil (4) if the time (Td) of the output signal (S1) of the comparator (15) is greater than the threshold signal time recorded in its memory.
EP13818200.1A 2012-12-11 2013-12-11 An induction heating cooktop Active EP2939499B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
TR201214456 2012-12-11
PCT/EP2013/076210 WO2014090868A1 (en) 2012-12-11 2013-12-11 An induction heating cooktop

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EP2939499A1 EP2939499A1 (en) 2015-11-04
EP2939499B1 true EP2939499B1 (en) 2016-12-07

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3562266B1 (en) 2018-04-23 2020-08-05 Whirlpool Corporation System and method for controlling quasi-resonant induction heating devices
EP3700297B1 (en) 2017-11-23 2022-03-02 Samsung Electronics Co., Ltd. Cooking device and control method thereof

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Publication number Priority date Publication date Assignee Title
KR102069580B1 (en) 2017-06-26 2020-01-23 엘지전자 주식회사 Pot detecting sensor and induction heating apparatus including thereof
KR102069583B1 (en) 2017-06-26 2020-01-23 엘지전자 주식회사 Induction heating apparatus and pot detection method thereof

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GB2062985B (en) * 1979-11-12 1983-11-02 Matsushita Electric Ind Co Ltd Small load detection by comparison between input and output parameters of an induction heat cooking apparatus
JP2811609B2 (en) * 1991-06-19 1998-10-15 松下電器産業株式会社 Pot detection device for induction heating cooker
ES2353987T3 (en) * 2005-06-02 2011-03-08 Panasonic Corporation INDUCTION HEATING EQUIPMENT.
WO2010137498A1 (en) * 2009-05-26 2010-12-02 三菱電機株式会社 Induction cooking device and induction heating method
JP2011023163A (en) * 2009-07-14 2011-02-03 Panasonic Corp Rice cooker

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3700297B1 (en) 2017-11-23 2022-03-02 Samsung Electronics Co., Ltd. Cooking device and control method thereof
US11622422B2 (en) 2017-11-23 2023-04-04 Samsung Electronics Co., Ltd. Cooking apparatus and method of controlling the same
EP3562266B1 (en) 2018-04-23 2020-08-05 Whirlpool Corporation System and method for controlling quasi-resonant induction heating devices

Also Published As

Publication number Publication date
CN105230120A (en) 2016-01-06
WO2014090868A1 (en) 2014-06-19
CN105230120B (en) 2017-05-03
EP2939499A1 (en) 2015-11-04

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