EP2469972B1 - Cooking device and method of controlling the cooking device which diminish in an iterative manner a flicker characteristic. - Google Patents

Description

The invention is based on a cooking device device according to the preamble of claim 1.

The publication EP 1 951 003 B1 discloses an induction hob with at least two heating frequency units operated according to a particular method to prevent intermodulation noises. According to this method, both heating-frequency units are operated at an identical first frequency in a first time period. In a second period of time, one heating frequency unit is switched off, while the other heating frequency unit is operated at a second frequency. The two frequencies as well as the relative lengths of the two time segments are adjusted so that a mean output power of each heating frequency unit corresponds to an operator selected heating power.

The object of the invention is in particular to provide a generic Gargerätevorrichtung, which is network compliant in any operating condition. The object is achieved by the features of claim 1 and the method claim 9, while advantageous embodiments and refinements of the invention can be taken from the dependent claims.

The invention is based on a cooking device device with at least two heating frequency units and with at least one control unit, which is provided to set a respective average output power of the heating frequency units.

It is proposed that the control unit is provided to iteratively reduce a patch parameter. The cooking device device is preferably a hob device and particularly advantageous as an induction hob device educated. By "provided" is intended to be understood in particular specially programmed and / or designed and / or equipped. A "heating frequency unit" should in particular be understood to mean an electrical unit which generates an oscillating electrical current, preferably with a frequency of at least 1 kHz, in particular of at least 10 kHz and advantageously of at least 20 kHz, for operation of at least one heating unit. A "heating unit" is to be understood in particular a unit which is intended to at least partially convert electrical energy into heat and thus in particular to heat a food to be cooked. In particular, the heating unit comprises a radiant heater, a resistance heater and / or preferably an induction heater, which is intended to convert electrical energy indirectly via induced eddy currents into heat. The heating frequency unit comprises in particular at least one inverter, which preferably comprises two switching units. A "switching unit" is to be understood in particular a unit which is intended to interrupt a parts of the switching unit comprehensive line path. Preferably, the switching unit is a bidirectional unipolar switch which in particular allows a current flow through the switch along the conduction path in both directions and in particular short-circuits an electrical voltage in at least one polarity direction. Preferably, the inverter comprises at least two bipolar transistors with insulated gate electrode and particularly advantageously at least one damping capacitor. A "conduction path" is to be understood as meaning, in particular, an electrically conductive conductor piece between two points.

A "control unit" is to be understood, in particular, as an electronic unit which is preferably at least partially integrated in a control and / or regulating unit of a cooking appliance, in particular an induction hob. Preferably, the control unit comprises a computing unit and in particular in addition to the computing unit, a memory unit with a control program stored therein. Preferably, the control unit is provided to control the heating frequency units by means of electrical control signals and / or to regulate. An electrical "control signal" is to be understood in particular a signal having an electrical voltage of at most 30 V, preferably of at most 20 V and more preferably of at most 10 V, which is supplied in particular in at least one operating state, the inverters of the heating frequency units. Preferably, the control signal has a periodicity at least at times, in particular with a period of at most 1 ms, in particular of at most 0.1 ms and advantageously of at most 0.05 ms. Particularly advantageously, the control signal is a square-wave signal, which in particular can assume two values, preferably a switch-on value and a switch-off value. Preferably, each of the two values corresponds to a switching position of the inverters. A "frequency" of a heating frequency unit is to be understood in particular as the frequency of the control signal controlling the heating frequency unit.

An "output power" is to be understood, in particular, as meaning an electrical power which, in at least one operating state, is transmitted from a heating frequency unit to a heating unit. Preferably, the output power is transmitted by an electric current. The output power is preferably converted in the heating unit at least partially and particularly advantageously at least to a large extent into a heat flow. A "mean output power" is to be understood in particular a time-averaged output power. Preferably, the control unit is provided to set the average output power such that a selected by an operator heating power is achieved, in particular for each heating zone of a hob. A "Flickerkenngröße" should be understood as a parameter that represents a measure of flicker. By "flicker" is meant in particular a subjective impression of instability of a visual perception, which is caused in particular by a light stimulus whose luminance or spectral distribution varies with time. In particular, flicker can be caused by a voltage drop of a mains voltage. The flicker characteristic is preferably an overall output power difference, preferably between two times of two time ranges and particularly advantageous two adjacent time ranges. A "total output power" is to be understood as meaning, in particular, a sum of the output powers of all heating-frequency units at a particular point in time. A "total output power difference" is to be understood in particular as a difference of the total output powers at two different points in time. By the fact that the control unit is intended to "iteratively reduce" a patch parameter, it should be understood, in particular, that the control unit is intended to execute a loop-shaped algorithm, the patch characteristic preferably being smaller in each loop of the algorithm than in a previous one Loop. Preferably, the control unit is provided to reduce a total output power difference between times of two, preferably adjacent, time periods.

Such a configuration can ensure that the cooking appliance device operates in line with the network in each operating state. Furthermore, the flicker characteristic can always be controlled and, in particular, lowered below a statutory and / or normative limit. Furthermore, a control unit can be provided with an advantageously simple control algorithm.

It is also proposed that the control unit is provided to lower the flicker characteristic below a threshold. The limit value is preferably a value defined by at least one statutory requirement and / or standard, in particular the standard DIN EN 61000-3-3. This will ensure compliance with legal and / or regulatory limits. In particular, a perceptible by a human swaying a light intensity due to voltage fluctuations in a mains voltage can be avoided thereby.

In a preferred embodiment of the invention, it is proposed that the control unit is provided for a time interval in at least two subintervals split taking into account at least one output power. Preferably, the control unit is provided to operate at least one of the heating frequency units in the sub-intervals, each with a different output power. Preferably, the control unit is provided to operate the heating frequency units in each case in a sub-interval with constant operating parameters, in particular a constant frequency and / or a constant duty cycle. In particular, a ratio of a time duration in which the control signal assumes the switch-on value within a period duration to the period duration of the control signal is to be understood as a "duty cycle". This ensures that any heating power selected by an operator can be delivered while largely avoiding intermodulation noise. A "substantial avoidance of intermodulation noise" should be understood in particular that intermodulation noises at a frequency of 17 kHz and smaller at a distance of 1 m from the cooking appliance a sound pressure level of at most 20 dB, in particular of at most 10 dB, preferably of at most 5 dB and particularly advantageous of a maximum of 0 dB. Preferably, the intermodulation sounds are inaudible to an average hearing operator.

Advantageously, the control unit is provided to reduce the patch parameter between the two sub-intervals. By the fact that the control unit is intended to "reduce the flicker characteristic between the two subintervals", it should be understood in particular that the control unit is intended to be identical with the flicker characteristic calculated from operating parameters of the two subintervals, which is identical in particular to the total output power difference of the two subintervals is to downsize and preferably iteratively to downsize. As a result, an advantageously low-flicker transition from one sub-interval to the other sub-interval can be achieved.

In a particularly preferred embodiment of the invention it is proposed that the control unit is provided to gradually reduce a frequency of at least one of the heating frequency units. Preferably, a Reduction in equidistant steps. In particular, a step size of 30 Hz to 90 Hz, preferably 50 Hz to 70 Hz and particularly advantageously about 60 Hz. This can be a reliable algorithm can be created, which comes within a short time advantageous to a result.

It is also proposed that the control unit is intended to use as start value a frequency between 60 kHz and 90 kHz. In particular, the control unit is intended to use as start value a frequency between 70 kHz and 80 kHz, and particularly advantageously about 75 kHz. A "start value" should be understood in particular to be a numerical value for the loop-shaped algorithm which is used in a first loop of the algorithm and which is changed by the algorithm in subsequent loops of the algorithm. As a result, an average runtime of the algorithm can be advantageously reduced.

In a further embodiment of the invention it is proposed that the control unit is provided to adapt a duty cycle. Preferably, in at least one operating state at a fixed frequency of one of the heating frequency units by changing the duty cycle, the output power can be changed. By the fact that "the control unit is intended to adapt a duty cycle", it should be understood in particular that the control unit is intended to change the duty cycle of at least one of the heating frequency units, thereby changing the output power at a fixed frequency in at least one operating state to reach the heating frequency unit. Preferably, the control unit is provided to keep temporally as constant as possible by varying the duty cycle of at least one of the two Heizfrequenzeinheiten a total output power of both Heizfrequenzeinheiten in at least one operating state. As a result, a more continuous output of the heating frequency units can be made possible. Furthermore, flexibility of the algorithm can be increased.

Advantageously, the control unit is provided to use as start value a duty cycle between 0.4 and 0.6. In particular, the control unit is provided to use as the starting value a duty cycle between 0.45 and 0.55 and particularly advantageously about 0.5. As a result, an average runtime of the algorithm can be advantageously reduced.

Furthermore, a method is proposed with a cooking device device with at least two heating frequency units, in which a respective average output power of the heating frequency units is set, wherein a flicker characteristic is iteratively reduced. As a result, the flicker characteristic can always be controlled and lowered in particular under a statutory and / or prescribed by standards limit.

Furthermore, a cooking appliance, in particular a hob, proposed with a Gargerätevorrichtung invention. Preferably, the hob is an induction hob.

Further advantages emerge from the following description of the drawing. In the drawing, an embodiment of the invention is shown.

Fig. 1

ein Induktionskochfeld mit einer erfindungsgemäßen Gargerätevorrichtung mit zwei Heizfrequenzeinheiten,

Fig. 2

ein beispielhaftes nicht maßstabsgetreues Steuersignal der Heizfrequenzeinheiten,

Fig. 3

beispielhafte Leistungs-Frequenz-Kurven für die zwei Heizfrequenzeinheiten,

Fig. 4

je eine beispielhafte Leistungs-Zeit-Kurve für die zwei Heizfrequenzeinheiten und

Fig. 5

ein Ablaufdiagramm eines erfindungsgemäßen Verfahrens.

Show it:

Fig. 1

an induction hob with a cooking appliance device according to the invention with two heating frequency units,

Fig. 2

an exemplary not to scale control signal of the heating frequency units,

Fig. 3

exemplary power frequency curves for the two heating frequency units,

Fig. 4

each an exemplary power-time curve for the two heating frequency units and

Fig. 5

a flow diagram of a method according to the invention.

Fig. 1 shows a trained as induction hob 16 cooking appliance. The induction hob 16 comprises a hob plate 18, in particular of a glass ceramic, on which in a known manner three heating zones 20, 22, 24 are marked. The hob plate 18 is arranged horizontally in an operational state of the induction hob 16 and provided for setting up cooking utensils. Furthermore, touch-sensitive operating elements 26 and display elements 28 of an operating and display unit 30 of the induction hob 16 are marked on the hob plate 18 in a known manner. The induction hob 16 further comprises a cooking device device with two heating frequency units 10, 12 arranged below the hob plate 18 and with a control unit 14 arranged below the hob plate 18 Fig. 1 are components which are arranged below the cooking plate 18, dashed lines, wherein functional relationships are indicated by means of arrows. The control unit 14 is integrated in a control and regulation unit 32 of the induction hob 16. One of the heating zone 20 associated and disposed below this induction heating unit is powered by the heating frequency unit 10 with energy. One of the heating zone 22 associated and arranged below this induction heating unit and another of the heating zone 24 associated and arranged below this induction heating unit are supplied via a switching unit 34 of the cooking appliance by the heating frequency unit 12 with energy. The switching unit 34 is provided for operating the two induction heating units assigned to the two heating zones 22, 24 in a known manner in a time division multiplex controlled by the control unit 14. An operator can select a heating level for each of the heating zones 20, 22, 24 by means of the operating and display unit 30. The control unit 14 is provided to set a respective average output power P _0A , P _{0B of} the heating frequency units 10, 12, so that the selected Heizzstufen the heating zones 20, 22, 24 are achieved, in particular using the time division multiplex, while Intermodulationsgeräusche be avoided. The control unit 14 controls the heating frequency unit 10 by means of a control signal V _A (t) and the heating frequency unit 12 by means of a control signal V _B (t).

Fig. 2 shows by way of example a non-to-scale control signal V _A (t) in a Cartesian coordinate system. On a ordinate axis 36, a control voltage V _A and on a abscissa axis 38, a time t is plotted. The control signal V _A (t) during a sub-interval T _{2 of} a time interval T is a rectangular signal with a switch-on value V ₀ and a switch-off value of 0 volts. The switch-on value V ₀ is held during a switch-on time t ₀ . A period of the rectangular signal is T ₀ . During a period of time (T ₀ -t ₀ ), the turn-off value is held. A frequency f of the control signal V _A (t) is calculated from a reciprocal of the period T ₀ . The frequency f is usually between 30 kHz and 100 kHz. A duty cycle D _{A of} the control signal V _A (t) is calculated from a quotient of the switch-on time t ₀ divided by the period T ₀ . An envelope 40 of the control signal V _A (t) is shown in dashed lines. While V _A (t) takes the form of the rectangular signal, an inverter of the heating frequency unit 10 is periodically switched in accordance with a periodic change of the ON value V ₀ and the OFF value. This results in a high-frequency alternating current to an operation of the heating zone 20 associated induction heating unit. During a subinterval T _{1 of} the time interval T with T ₁ = T - T ₂ , the control signal V _A (t) is identical to zero. After the time interval T has elapsed, V _A (t) repeats.

Hereinafter, it is assumed that the heating frequency unit 10 in a continuous operation requires a higher frequency f for generating the average output power P _0A than the heating frequency unit 12 for generating the average output power P _0B also in a continuous operation. However, the reverse case would also be conceivable. Fig. 3 shows in a Cartesian coordinate system by way of example a power frequency curve P _A (f) and for different duty cycles D _B = d _j (j = 1, ..., n) different power frequency curves P _B (f). On an ordinate axis 42 are output powers P _A and P _{B of} the heating frequency units 10, 12 applied. On an abscissa axis 44, the frequency f is plotted. The heating frequency unit 12, which requires a lower frequency f to achieve the average output power P _0B in a continuous operation, is operated in the two subintervals T ₁ and T _{2 of} the time interval T with fixed frequencies f ₁ and f ₂ and with duty cycles D _B1 and D _B2 operated. The heating frequency unit 10 is operated at the frequency f ₂ in the partial interval T ₂ , in which the heating frequency unit 12 is operated at the higher frequency f ₂ > f ₁ .

Fig. 4 shows in a Cartesian coordinate system by way of example two power-time curves P _A (t) and P _B (t). The output powers P _A and P _{B of} the heating frequency units 10, 12 are plotted on an ordinate axis 46. The time t is plotted on an abscissa axis 48. Fig. 4 shows how the heating frequency unit 12 in the first sub-interval T ₁ with the frequency f ₁ and the duty cycle D _{B1 is} operated while the heating frequency unit 10 is turned off. In the second sub-interval T ₂ , both heating-frequency units 10, 12 are operated with the same frequency f ₂ > f ₁ and with duty cycles D _A and D _B2 . As a result, intermodulation hum can be effectively avoided. For the heating frequency unit 10, the output power P _A during the sub-interval T _{2 is} greater than the average output power P _0A . The mean output power P _0A results from the product of the output power P _A with the quotient of the subinterval T ₂ divided by the time interval T: $${\mathrm{P}}_{\mathrm{0}\mathrm{A}}={\mathrm{P}}_{\mathrm{A}}\times {\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="imgf0001.png"\; state="\{\{state\}\}">T</figure-callout>}}_{\mathrm{2}}/\mathrm{T}\mathrm{,}$$

In the present example, an output power P _B1 for the heating frequency unit 12 in the first sub-interval T _{1 is} greater than the average output power P _0B . In the second sub-interval T ₂ , on the other hand, an output power P _B2 is smaller than the average output power P _0B . The mean output power P _0B results as a weighted time average from the output _powers P _B1 and P _B2 : $${\mathrm{P}}_{\mathrm{0}\mathrm{B}}={\mathrm{<figure-callout\; id="1"\; label="P\; B"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">P\; </figure-callout>}}_{\mathrm{B}}\times {\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">T</figure-callout>}}_{\mathrm{1}}/\mathrm{T}+{\mathrm{<figure-callout\; id="2"\; label="P\; B"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P\; </figure-callout>}}_{\mathrm{B}}\times {\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="imgf0001.png"\; state="\{\{state\}\}">T</figure-callout>}}_{\mathrm{2}}/\mathrm{T}\mathrm{,}$$

A determination of the sub-intervals T ₁ and T ₂ , the frequencies f ₁ and f ₂ and the duty D _A and D _B2 is carried out under iterative minimization of a flicker F under a set by the standard DIN EN 61000-3-3 limit F _G. The patch characteristic F is an overall output difference F = P _B1 - (P _A + P _B2 ) between the two sub-intervals T ₁ and T ₂ . The control unit 14 is intended to be a in Fig. 5 to perform a flowchart illustrated method for minimizing the patch characteristic F. The method starts with a step 58 after a selection of heating powers for the heating zones 20, 22, 24 by an operator. Considering an operation of the heating zones 22, 24 in the time division multiplex, the average output power P _0A and P _{0B is} determined for the heating frequency units 10, 12. For the frequency f ₂ , a starting value of 75 kHz is selected. In a step 60, a starting value of 0.5 is selected for the duty cycles D _A , D _B1 and D _B2 . In a step 62, a time x is determined which divides the time interval T into the sub-intervals T ₁ and T ₂ . This is done with the aid of the relationship x = P _0A / P _A × T. In a step 64, the output powers P _B1 and P _{B2 are determined} during the sub-intervals T ₁ and T ₂ for the heating frequency unit 12, so that the mean Output power P _0B results. From the output power P _B1 , the frequency f _{1 is} determined. In a step 66, the patch characteristic F is calculated. In a branch 68 it is checked whether the flicker characteristic F is greater than the limit value F _G. If this is not the case, then the method ends with a step 70. The method has then as a result of the time x, the frequencies f ₁ and f ₂ and the duty cycles D _A , D _B1 and D _B2 for the heating frequency units 10, 12 determined , so that the flicker characteristic F corresponds to the standard.

If the flicker characteristic F is greater than the limit value F _G , then in a step 72 the duty cycle D _{B2 is} decreased by a value of 0.05. In a branch 74 it is checked whether the duty cycle D _{B2 is} equal to zero. If the duty cycle D _{B2 is} not equal to zero, there is a jump to step 64, in which a redetermination of the output powers P _B1 and P _B2 occurs. If the duty cycle D _{B2 is} equal to zero, the duty cycle D _{B2 is} reset to 0.5 in a step 76. Instead, will the duty cycle D _A is lowered by a value of 0.05. In a branch 78 it is checked whether the duty cycle D _{A is} equal to zero. If the duty cycle D _{A is} not equal to zero, there is a jump to step 62, in which a redetermination of the time x takes place. If the duty cycle D _{A is} equal to zero, the frequency f ₂ is reduced by a value of 60 Hz in a step 80. In addition, a jump is made to step 60 in which the duty cycles D _A and D _{B2 are} reset to 0.5 become.

In an alternative embodiment, adaptation of the duty cycles D _A and D _{B2 can} also be dispensed with. It is also conceivable that only one of the duty cycles D _A or D _{B2 is} adjusted. Alternatively, an induction hob can also have four induction heating units, wherein two of the induction heating units are each connected via a switching unit to a heating frequency unit. As an alternative or in addition to operation in a time multiplex, two induction heating units assigned to a heating frequency unit can also be operated by any other method that appears appropriate to a person skilled in the art. Furthermore, it is also conceivable that more than two induction heating units are assigned to a heating frequency unit. reference numeral 10 Heizfrequenzeinheit 72 step 12 Heizfrequenzeinheit 74 branch 14 control unit 76 step 16 Induction hob 78 branch 18 Hotplate 80 step 20 heating zone P _0A Average output power 22 heating zone P _0B Average output power 24 heating zone T ₀ period 26 operating element T time interval 28 display element T ₁ subinterval 30 Operating and display unit T ₂ subinterval 32 Control unit X time 34 switching unit t Time 36 axis of ordinates t ₀ on time 38 abscissa f frequency 40 envelope f ₁ frequency 42 axis of ordinates f ₂ frequency 44 abscissa D _A duty cycle 46 axis of ordinates D _B duty cycle 48 abscissa D _B1 duty cycle 58 step D _B2 duty cycle 60 step d _j duty cycle 62 step V _A (t) control signal 64 step V _A control voltage 66 step V ₀ Switch-on 68 branch P _A (f) Power-frequency curve 70 step P _B (f) Power-frequency curve P _A output P _B output P _B1 output P _B2 output P _A (t) Power-time curve P _B (t) Power-time curve

Claims (10)

1. Cooking appliance device having at least two heat frequency units (10, 12) and having at least one control unit (14), which is provided to set a respective average output power (P _0A , P _0B ) of the heat frequency units (10, 12), wherein the control unit (14) is provided to diminish a flicker characteristic (F), which represents a measure of flicker, characterised in that the control unit (14) is provided to iteratively diminish the flicker characteristic (F).
2. Cooking appliance device according to claim 1, characterised in that the control unit (14) is provided to reduce the flicker characteristic (F) to below a limit value (F_G ).
3. Cooking appliance device according to claim 1 or 2, characterised in that the control unit (14) is provided to divide a time interval (T) into at least two sub-intervals (T ₁, T ₂) by taking at least one output power (P_A ) into account.
4. Cooking appliance device according to claim 3, characterised in that the control unit (14) is provided to diminish the flicker characteristic (F) between the two sub-intervals (T ₁, T ₂).
5. Cooking appliance device according to one of the preceding claims, characterised in that the control unit (14) is provided to gradually diminish the frequency (f ₂) of at least one of the heat frequency units (10, 12).
6. Cooking appliance device according to claim 5, characterised in that the control unit (14) is provided to use a frequency (f ₂) between 60 kHz and 90 kHz as a start value.
7. Cooking appliance device according to one of the preceding claims, characterised in that the control unit (14) is provided to adjust a pulse duty factor (D_A , D _B2).
8. Cooking appliance device according to claim 7, characterised in that the control unit (14) is provided to use a pulse duty factor (D_A , D _B2) between 0.4 and 0.6 as a start value.
9. Method with a cooking appliance device having at least two heat frequency units (10, 12), in particular according to one of the preceding claims, in which a respective average output power (P _0A , P _0B ) of the heat frequency unit (10, 12) is set, wherein a flicker characteristic (F), which represents a measure of flicker, is diminished, characterised in that the flicker characteristic (F) is iteratively diminished.
10. Cooking appliance, in particular hob, having a cooking appliance device according to one of claims 1 to 8.

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