Method and induction heating device for determining a temperature of a cooking vessel base

Patent metadata

Field	Value
Publication number	US-10085303-B2
Application number	US-95239910-A
Country	US
Kind code	B2
Filing date	Nov 23, 2010
Priority date	Nov 26, 2009
Publication date	Sep 25, 2018
Grant date	Sep 25, 2018

Abstract

An induction heating device comprises a frequency converter that generates a high-frequency drive voltage from an intermediate circuit voltage generated at least temporarily as a function of an AC mains voltage, a resonant circuit having an induction heating coil, with the drive voltage applied to the resonant circuit, and a temperature detection device that determines a temperature of a cooking vessel base which is heated by means of the induction heating coil. An auxiliary voltage source generated the intermediate circuit voltage over predefined time periods at a constant level. The frequency converter generates the drive voltage over time periods such that the resonant circuit oscillates at a natural resonant frequency in a substantially de-attenuated manner, and the temperature detection device further measuring at least one oscillation parameter over the time periods, and to evaluate the at least one measured oscillation parameter in order to determine the temperature.

First claim

The invention claimed is:

1. A method for determining a temperature of a cooking vessel base which is heated by means of an induction heating coil, comprising:
generating an intermediate circuit voltage at least temporarily as a function of an AC mains voltage;
generating a high-frequency drive voltage from the intermediate circuit voltage;
applying the drive voltage to a resonant circuit comprising the induction heating coil, said resonant circuit having a natural resonant frequency;
generating the intermediate circuit voltage over predefined time periods at a constant level;
generating the drive voltage over the predefined time periods, wherein the generated drive voltage makes the resonant circuit oscillate at said natural resonant frequency in a de-attenuated manner;
measuring at least one oscillation parameter comprising at least one detected resonant frequency of the resonant circuit over the predefined time periods;
determining, via at least one processor, the temperature of said cooking vessel base based on the measured at least one detected resonant frequency of the resonant circuit during a duration comprising the predefined time periods; measuring a current profile through the induction heating coil or a voltage profile across the induction heating coil; and generating the drive voltage synchronously to the measured current profile or to the measured voltage profile, wherein the generated drive voltage makes the resonant circuit oscillate at said natural resonant frequency in a de-attenuated manner over the time periods.

2. The method according to claim 1 , further comprising:
determining zero crossings in the AC mains voltage; and
selecting the time periods in the region of the zero crossings.

3. The method according to claim 2 , wherein the time periods are centred with respect to the zero crossings.

4. The method according to claim 1 , wherein the time periods have a duration in a range of 50 μs to 1000 μs.

5. The method according to claim 1 , wherein the at least one oscillation parameter comprises one from the group of the natural resonant frequency, an amplitude of a resonant circuit voltage, an amplitude of a resonant circuit current, or a phase shift between the resonant circuit voltage and the resonant circuit current.

6. The method according to claim 1 , wherein the intermediate circuit voltage is generated over the time periods at a level in a range of 10 V to 50 V.

7. The method according to claim 1 , wherein a frequency of the drive voltage or a pulse duty factor of the drive voltage is varied for the purpose of setting a heating power, which is to be output by the induction heating coil, at times outside the time periods.

8. The method according to claim 1 , further comprising:
generating the drive voltage by means of a half-bridge circuit comprising two IGB transistors, with the IGB transistors being driven by a control signal;
generating a power setting signal as a function of a heating power which is to be output;
generating a de-attenuation signal as a function of the measured current profile or the measured voltage profile; and
selecting the power setting signal as the control signal at times outside the time periods, and selecting the de-attenuation signal as the control signal at times within the time periods.

9. The method according to claim 8 , wherein the control signal is generated at the edges of the time periods by logically combining the power setting signal and the de-attenuation signal.

10. An induction heating device comprising:
a frequency converter configured to generate a high-frequency drive voltage from an intermediate circuit voltage which is generated at least temporarily as a function of an AC mains voltage;
a resonant circuit having an induction heating coil, with the drive voltage applied to the resonant circuit;
a temperature detection device configured to determine a temperature of a cooking vessel base which is heated by means of the induction heating coil;
an auxiliary voltage source which is designed to generate the intermediate circuit voltage over predefined time periods at a constant level,
wherein the frequency converter is designed to generate the drive voltage over the time periods such that the resonant circuit oscillates at a natural resonant frequency in a de-attenuated manner, and
wherein the temperature detection device is designed to measure at least one oscillation parameter of the oscillation over the time periods, and to evaluate the at least one measured oscillation parameter in order to determine the temperature; and a current sensor configured to measure a current profile through the induction heating coil or a voltage profile across the induction heating coil, wherein the frequency converter is designed to generate the drive voltage in synchronism with the measured current profile or the measured voltage profile, wherein the generated drive voltage makes the resonant circuit oscillate at the said natural resonant frequency in a de-attenuated manner over the time periods.

11. An induction heating device according to claim 10 , further comprising:
a zero crossing detector designed to determine zero crossings of the AC mains voltage; and
a control device designed to select the time periods in the region of the zero crossings.

12. The induction heating device according to claim 10 , wherein the auxiliary voltage source is designed to generate an auxiliary voltage at a level in a range of 10 V to 50 V.

13. The induction heating device according to claim 10 , further comprising:
a half-bridge circuit comprising two IGB transistors which are driven by a control signal, with the frequency converter being designed to generate a power setting signal as a function of a heating power which is to be output, and a de-attenuation signal as a function of the measured current profile or the measured voltage profile; and
a controller configured to select the power setting signal as the control signal at times outside the time periods, and to select the de-attenuation signal as the control signal at times over the time periods.

14. The induction heating device according to claim 13 , further comprising:
a gate driver circuit driving the IGB transistors, with the auxiliary voltage source configured to supply a supply voltage to the gate driver circuit.

15. The method of claim 1 , wherein:
determining further comprises determining the temperature of the cooking vessel base by evaluating a characteristic curve associating a cooking vessel base temperature with the resonant frequency.

Assignees

• Schilling Wilfried
• Schoenherr Tobias
• Kappes Werner
• Volk Martin
• Ego Elektro Geraetebau Gmbh

Inventors

• Schilling Wilfried
• Schönherr Tobias
• Kappes Werner
• Volk Martin

Classifications

• H05B2213/07

  Heating plates with temperature control means · CPC title

• G01K11/26

  of resonant frequencies · CPC title

• H05B6/062 Primary

  for cooking plates or the like · CPC title