EP4210435A1 - Procédé et dispositif de mesure de la puissance sur une bobine de chauffage par induction - Google Patents

Procédé et dispositif de mesure de la puissance sur une bobine de chauffage par induction Download PDF

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Publication number
EP4210435A1
EP4210435A1 EP22210273.3A EP22210273A EP4210435A1 EP 4210435 A1 EP4210435 A1 EP 4210435A1 EP 22210273 A EP22210273 A EP 22210273A EP 4210435 A1 EP4210435 A1 EP 4210435A1
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EP
European Patent Office
Prior art keywords
duty cycle
induction heating
converter
voltage
heating coil
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP22210273.3A
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German (de)
English (en)
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EP4210435B1 (fr
Inventor
Christian Egenter
Max-Felix Müller
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EGO Elektro Geratebau GmbH
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EGO Elektro Geratebau GmbH
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Publication of EP4210435A1 publication Critical patent/EP4210435A1/fr
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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

Definitions

  • the invention relates to a method for measuring power at an induction heating coil in an induction hob and a device that is designed to carry out this method, in particular a device that is part of an induction hob.
  • an operator When operating an induction heating coil of an induction hob, it is not only important that an operator can specify a desired power level as a power level, which is then approximately maintained with larger deviations or less accuracy.
  • a very precise setting of the power on an induction heating coil may be desirable, particularly in the case of a coordinated operation of a plurality of adjacent induction heating coils which are covered by a common cooking vessel. What matters here is the power actually generated by the induction heating coil in conjunction with the heated cooking vessel, so that it should be able to be recorded as precisely as possible. Then regulations and automatically running cooking programs can run as precisely as possible.
  • the invention is based on the object of creating a method as mentioned at the outset and a device for carrying out the method as mentioned at the outset, with which problems of the prior art can be solved and in particular it is possible to measure a power generated by an induction heating coil as precisely as possible and preferably with to be able to measure with as little effort as possible.
  • the induction heating coil or a transmitter coil of a device for the wireless transmission of power to a consumer is controlled by a converter, in particular a converter of a power unit or the like. an induction hob.
  • the converter is operated in a half-bridge or full-bridge circuit. Furthermore, the converter is operated with a frequency and with a duty cycle, with both the frequency and the duty cycle being able to be varied to adjust the power output by the induction heating coil. Furthermore, the current is measured through the induction heating coil, which is relatively easy and accurate to measure.
  • At least in one operating mode of driving the induction heating coil there is a switch between driving with a 1st duty cycle and driving with a 2nd duty cycle.
  • This change can take place with varying frequency, which is explained in more detail below.
  • the 2nd duty cycle is determined by subtracting the 1st duty cycle from 1 and the duration of the 2nd duty cycle is determined by subtracting a duration of the 1st duty cycle from a total cycle time.
  • the voltage is measured or determined across the half bridge or across the full bridge, with which the induction heating coil is controlled. It is thus possible that by changing the duty cycle, errors when measuring the voltage and thus when measuring the power can be compensated for or calculated out, so to speak.
  • This zero crossing brings significant advantages in the switching behavior in the converter as well as in the disturbance behavior and with regard to mains feedback.
  • an averaging is carried out over two directly consecutive half-waves of the named voltage or mains voltage or supply voltage.
  • the advantage here is that external or external changes to a cookware or device to be operated, such as its temperature or installation position, can be assumed to be constant within 20msec, i.e.
  • the same load condition and the deviation are measured in the first half-wave and in the second half-wave of the measurement corresponds to the measurement error of control.
  • the averaging is advantageously carried out by directly determining an average value of the two measured powers, ie adding them and dividing them by two. This is a very simple and accurate computational procedure.
  • the aforesaid compensation or the aforesaid averaging can take place in a very finely divided manner.
  • the resulting high switching frequency for the converter or circuit breakers contained therein, in particular IGBT does not represent a problem and can be easily managed by them.
  • the power at the induction heating coil can be measured permanently, so to speak. In particular, a power measurement is always correct immediately after two half-waves, since the 1st duty cycle and the 2nd duty cycle were controlled and measured once. A performance measurement is always completely up-to-date, so to speak.
  • the power measurement is correct even after each half-wave, since two consecutive half-waves can always be taken for the calculation, so it is always overlapping, so to speak.
  • the mains half-waves 1, 2, 3, 4, 5 can always be measured alternately with DC and (1-DC).
  • mains half-wave 1 the power measurement is initially wrong.
  • mains half-wave 2 the measurement at mains half-waves 1+2 can be averaged.
  • mains half-wave 3 the measurement can be averaged for mains half-waves 2+3, after mains half-wave 4, the measurement for mains half-waves 3+4 can be averaged, and so on. It is therefore not absolutely necessary to use the measurement at mains half-waves 1+2 and then at mains half-waves 3+4.
  • control with the 1st duty cycle can be used for more than two half-waves of the aforementioned voltage or mains voltage, and then control with the 2nd duty cycle can be used for the same number of half-waves of the voltage or mains voltage.
  • This is a way to switch between duty cycles less frequently and thus cause fewer switching operations, potentially making the method easier to perform.
  • actuation it is possible for actuation to be carried out with each of the duty cycles for an even number of half-waves.
  • this number of half-waves of the voltage or mains voltage is used for activation with the 1st duty cycle and with the 2nd duty cycle until a predetermined power for the induction heating coil changes, until the operating point and thus the switching behavior of the converter change.
  • the measured power does not correspond to the target power or is below it, it makes sense to keep the switching interval short in order to obtain a measured value more quickly.
  • the measuring interval can be extended. Switching between DC and (1-DC) does not change the power output, but only reduces the measurement error.
  • a measurement interval during which a power is determined at the induction heating coil and which is also completely required for this determination, consists of equal parts of the control with the 1st duty cycle and of the control with the 2. Duty cycle exists.
  • the power at the induction heating coil is only finally determined after the control with the two duty cycles has been carried out completely, the current and voltage naturally being measured in the manner described above during the entire time.
  • a measurement interval for determining the power at the induction heating coil can consist of two intervals of half-waves of a voltage or mains voltage with which the converter is supplied. It can advantageously be provided that in a 1st interval the converter is operated with the 1st duty cycle and in a 2nd interval the converter is operated with the 2nd duty cycle.
  • the 1st interval and the 2nd interval are of the same length, so that in turn the same proportions are used for each of the two duty cycles for the correct determination of the power at the induction heating coil.
  • a measurement interval can include fewer half-waves, specifically exactly two half-waves, of an aforementioned voltage for supplying the converter. These are advantageously two consecutive half-waves, see above that, so to speak, measurements are taken during an entire full wave. Provision can be made for the 1st duty cycle to be used during the first half-wave and for the 2nd duty cycle to be used during the other or directly subsequent half-wave.
  • the integral of the product of voltage and current over time can be calculated over the intervals of activation with the 1st duty cycle and activation with the 2nd duty cycle to determine a power at the induction heating coil. These are the currently measured current and the currently measured voltage at the induction heating coil.
  • the voltage across the induction heating coil is estimated from the activation of power switches or semiconductor switches of the converter.
  • a switching delay of the switch is also taken into account. In this way, a voltage can be estimated as well or as accurately as possible.
  • the same duty cycle can be used during a number of consecutive half-waves of the voltage or mains voltage without being changed. Only then is the other duty cycle used.
  • the number of half-waves per duty cycle is advantageously the same in each case.
  • At least the number of half-waves over which the average is taken should consist of equal parts of DC and (1-DC).
  • a different number of 1st and 2nd duty cycle can be calculated out by appropriate unequal weighting.
  • the 1st duty cycle is between 0 and 0.5. It is therefore smaller than the 2nd duty cycle.
  • the upper switching element is switched on for shorter than half the period for duty cycles less than 0.5, while the lower switching element in this example is switched on for shorter than half the period for duty cycles greater than 0.5. Both the 1st and the 2nd duty cycle result in the same output AC voltage of the inverter.
  • the operation does not change when the induction heating coil is activated with regard to the power specified for it and a cooking vessel heated with the induction heating coil, which is placed above it on a hob plate and at least covers this induction heating coil to a significant extent, does not move will no longer change between the duty cycle of the control. So it is possible that the Control takes place permanently with the same duty cycle. For this special case, it is then assumed that the power generated by the induction heating coil does not change and therefore no current or updated power measurement is required. This allows the control to be simplified without the power measurement becoming inaccurate.
  • the temperature should not change when the method is carried out, because the power is shifted at an operating point that remains the same as a result of a temperature change.
  • the induction heating coil then simply produces a different output.
  • this change occurs relatively slowly, preferably as a kind of drift, so that an occasional remeasurement would be sufficient to eliminate the error that occurs, for example at least every 10 seconds, 60 seconds or 120 seconds.
  • At least two induction heating coils are each operated on a half bridge of the converter on the same intermediate circuit, alternatively they are operated on a full bridge of the converter.
  • these two induction heating coils are each operated synchronously with any predetermined power, which can also differ by at least 30%, in particular by at least 60%.
  • any duty cycle can be provided or specified.
  • a difference can be at least 30% or at least 60%.
  • the power and duty cycle can be adjusted as desired.
  • the duty cycle for all induction heating coils on this converter can be changed synchronously, so that the interaction with the at least second converter is also neutralized by the switching.
  • the current of the inverter through the inductor leads to a double operating frequency ripple of the intermediate circuit voltage in the inverter, because the switching of the inverter from the upper arm of the inverter to the lower arm of the inverter and back again causes a reversal of the direction of the current in the intermediate circuit capacitor.
  • harmonics of the current are also excited by the induction coil in addition to the fundamental.
  • the second harmonic of the current which has its excitation maximum at a duty cycle of 0.25 or 0.75, together with the double frequency of the ripple of the intermediate circuit voltage, now results in the output power of the inverter increasing in addition to the power in the induction heating coil can supply or remove additional power from the intermediate circuit capacitor.
  • a device designed according to the invention as mentioned at the outset has a converter, in particular a conventional and known converter for induction heating coils, a control and at least two half bridges or at least one full bridge for the converter.
  • the control is designed to carry out the method described above and to measure the power currently generated by the induction heating coil as precisely as possible in different ways.
  • Control can be provided either only for the converter or on the converter.
  • the actuation can be a controller, in particular a microcontroller, for the entire device.
  • a specification for a power to be generated by the at least one induction heating coil can also be entered on it by an operator.
  • the aforementioned converter advantageously has an intermediate circuit, this intermediate circuit being connected to exactly one half bridge, to exactly two half bridges or to at least one full bridge. In this way, a simple and practical structure can be achieved.
  • the device is preferably installed in an induction hob or part of an induction hob. This has one or two such converters, with each converter advantageously being fed from a separate phase of a three-phase connection in a household or house that is only provided for it. A large number of such induction heating devices is arranged under the hob plate, for example eight to twenty-four.
  • an induction hob 11 is shown with a hob plate 13, on the underside of which two induction heating coils 15a and 15b are arranged.
  • the induction hob 11 has a hob controller 16 and separate power electronics 17, which is in particular designed as a converter.
  • the power electronics 17 controls the induction heating coils 15a and 15b. It receives its commands, in particular with regard to the amount of power to be generated, from the hob controller 16, so to speak.
  • the hob controller 16 contains a control device with control elements including a display for an operator, as is customary.
  • a cooking vessel 20, which is to be heated with this, is set up above the left-hand induction heating coil 15a.
  • the power electronics 17 essentially contain a previously described converter 18 . A section of it is in the 2 shown.
  • the power switches Z1 and Z2 are designed as IGBTs in the usual way, as are the diodes D1 and D2 as freewheeling diodes with the parallel resonant circuit capacitances C3 and C4. An intermediate circuit capacitor C5 is present.
  • the diodes D3 to D6 form a rectifier.
  • the induction heating coil 15a is controlled by the converter 18 and heats the cooking vessel 20 placed above it, which here corresponds to the R shown or is represented by it.
  • the converter 18 or the rectifier is fed on the left-hand side from a supply voltage, preferably the mains voltage in a household. It can be a single phase with a two-phase or three-phase connection of the induction hob 11 .
  • the driving of the converter 18 of the induction heating coil 15a for heating the cooking vessel 20 alternates between driving with a first duty cycle DC and driving with the second duty cycle, which is determined as (1-DC).
  • a first duty cycle DC DC
  • driving with the second duty cycle which is determined as (1-DC).
  • This can be done with the provisions explained above, for example that there is a changeover between the two duty cycles either within a half cycle of a supply voltage to which the converter 18 is connected, or in each case at a zero crossing of the supply voltage.
  • the duration of the activation with the first duty cycle should correspond to the duration of the activation with the second duty cycle.
  • the intermediate circuit voltage is present at the intermediate circuit capacitor C5, for example.
  • the 4 shows the course of the inductor current I, which thus flows through the induction heating coil 15a.
  • driving with (1-DC) leads to a mirroring of the peak currents along the x-axis. This means that in the first mains half-wave the negative currents are larger in amplitude than the positive currents, while in the second mains half-wave, i.e. when driving with the second duty cycle, the positive amplitudes are larger than the negative amplitudes.
  • FIG 5 shows the course of the inductor current in detail, namely when operating with the first duty cycle DC.
  • This duty cycle DC is selected according to the desired power for the induction heating coil 15a, which has been entered by an operator at the operating device 16. So this is on the 4 referred to the left half-wave there in the range of around 5 msec.
  • the 6 shows the inductor current with the second duty cycle (1-DC), but shifted by the duration of half a half-wave with 10 msec, i.e. around 15 msec. Comparing the two representations shows that the two Processes roughly correspond to each other when mirrored along a horizontal mirror axis.
  • the invention it is thus easily possible with the invention to form the power at the induction heating coil 15a as a product of inductor current and voltage, and then to integrate this over time. This can be carried out mathematically either in the power electronics 17 or in the cooktop control 16 .
  • induction heating coil 15b could be operated on the half-bridge of the converter 18.
  • These two induction heating coils 15a and 15b can be operated synchronously, ie with the same duty cycle DC or (1-DC).
  • the duty cycle can also be specified as desired for the two induction heating coils, as can the power. Only the duty cycle is then changed synchronously and simultaneously for these two induction heating coils. According to the invention, it takes place synchronously and simultaneously for all induction heating coils operated on the converter 18 .
  • the duty cycle can advantageously also be changed in order to set a desired output, which is specified in particular by the cooktop control 16 by means of an operator input.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Induction Heating (AREA)
EP22210273.3A 2022-01-10 2022-11-29 Procédé et dispositif de mesure de la puissance sur une bobine de chauffage par induction Active EP4210435B1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE102022200166.4A DE102022200166A1 (de) 2022-01-10 2022-01-10 Verfahren und Vorrichtung zum Messen einer Leistung an einer Induktionsheizspule

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EP4210435A1 true EP4210435A1 (fr) 2023-07-12
EP4210435B1 EP4210435B1 (fr) 2024-07-24

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2506665A2 (fr) * 2011-03-28 2012-10-03 BSH Bosch und Siemens Hausgeräte GmbH Dispositif d'appareil de cuisson
EP2731403A1 (fr) * 2011-07-08 2014-05-14 Mitsubishi Electric Corporation Cuisinière à induction et programme associé
DE102018214485A1 (de) * 2017-09-07 2019-03-07 BSH Hausgeräte GmbH Haushaltsgerätevorrichtung
US20210204367A1 (en) * 2018-01-03 2021-07-01 Lg Electronics Inc. Induction heating apparatus having improved interference noise cancellation and output control functions
US20210352772A1 (en) * 2020-05-06 2021-11-11 Lg Electronics Inc. Induction heating apparatus and method for controlling same

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20210135854A (ko) 2020-05-06 2021-11-16 엘지전자 주식회사 유도 가열 장치 및 유도 가열 장치의 제어 방법

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2506665A2 (fr) * 2011-03-28 2012-10-03 BSH Bosch und Siemens Hausgeräte GmbH Dispositif d'appareil de cuisson
EP2731403A1 (fr) * 2011-07-08 2014-05-14 Mitsubishi Electric Corporation Cuisinière à induction et programme associé
DE102018214485A1 (de) * 2017-09-07 2019-03-07 BSH Hausgeräte GmbH Haushaltsgerätevorrichtung
US20210204367A1 (en) * 2018-01-03 2021-07-01 Lg Electronics Inc. Induction heating apparatus having improved interference noise cancellation and output control functions
US20210352772A1 (en) * 2020-05-06 2021-11-11 Lg Electronics Inc. Induction heating apparatus and method for controlling same

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Publication number Publication date
DE102022200166A1 (de) 2023-07-13
EP4210435B1 (fr) 2024-07-24

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