EP2832182B1 - Induction heating device - Google Patents

Description

The invention is based on an induction heating device according to the preamble of claim 1.

From the prior art, an induction hob is known, which comprises an induction heating device with two heating frequency units and four heating inductors. Between the Heizfrequenzeinheiten and the Heizinduktoren a switching unit is arranged, which is intended to assign the Heizinduktoren the Heizfrequenzeinheiten. The induction heater further comprises four identical current sensor units which are connected in series with the heating inductors.

From the European patent application EP 2 068 598 A1 already an induction cooker and a control method is known. The induction heating cooker includes a plurality of heating coil groups, each of the heating coil groups including a plurality of heating coils connected in series, a plurality of inverters for individually supplying high frequency voltages to the respective heating coil groups, and a controller for controlling the operation of the inverters to control the high frequency voltages the heating coil groups are supplied based on the number of heating coils within the respective Heizspulengruppen on which at least one cooking vessel is arranged.

The object of the invention is, in particular, to optimize a generic Induktionsheizvorrichtung advantageous. The object is achieved by the features of claim 1, while advantageous embodiments and modifications of the invention can be taken from the dependent claims.

The invention is based on an induction heating device with at least two heating inductors, at least one heating frequency unit for supplying the heating inductors with a heating current, at least one resonance capacitor unit, at least one first current sensor unit and at least one second current sensor unit, each arranged in at least one resonant circuit and at least one measurement a Heizstromkenngröße are provided.

It is proposed that the first current sensor unit and the second current sensor unit have a different accuracy. Preferably, the two current sensor units are formed differently by a current sensor unit integrated in a power supply unit. By "provided" is intended to be understood in particular specially programmed and / or designed and / or equipped. A "heating inductor" is to be understood in particular a heating element with at least one induction heating, which is intended by induction effects, in particular by inducing electric current and / or by Ummagnetisierungseffekte, in a, preferably ferromagnetic, in particular metallic, heating means, in particular a cooking utensil, in an oven wall and / or in a radiator, which is arranged in an oven to cause heating of the heating means. In particular, the induction heating element is provided, in at least one operating mode, in which the induction heating is connected to a supply electronics, in particular the Heizfrequenzeinheit connected, a power of at least 100 W, in particular of at least 500 W, preferably at least 1000 W and more preferably at least 2000 W in particular to convert electrical energy into electromagnetic field energy, which is finally converted into heat in a suitable heating medium.

A "heating frequency unit" is to be understood in this context, in particular an electrical unit, which is an oscillating electrical signal, preferably with a frequency of at least 1 kHz, in particular of at least 5 kHz, preferably of at least 10 kHz, particularly advantageously of at least 15 kHz and in particular of at most 100 kHz for a heating inductor. In particular, the heating frequency unit is intended to provide a maximum electrical power required by the heating inductor of at least 1000 W, in particular of at least 1500 W, preferably of at least 2000 W and particularly advantageously of at least 2500W. The heating frequency unit comprises in particular at least one inverter, which preferably has at least two, preferably series-connected, bidirectional unipolar switches, which are in particular formed by a transistor and a diode connected in parallel, and particularly advantageously at least one damping capacitor connected in parallel to the bidirectional unipolar switches, which is in particular formed by at least one capacitor. Preferably, the heating frequency unit is supplied by a rectifier unit with a rectified alternating current.

A "resonance capacitor unit" is to be understood as meaning, in particular, a unit which has at least one resonance capacitor. In this context, a "resonance capacitor" is to be understood as meaning, in particular, a capacitor which in at least one operating state has a frequency of at least 1 kHz, in particular of at least 5 kHz, preferably of at least 10 kHz and particularly advantageously of at least 15 kHz is discharged, in particular in a predetermined by the heating frequency unit clock. A "resonant circuit" is to be understood in particular as meaning a circuit and preferably an ac circuit which has at least one heating inductor and preferably a resonant capacitor of the resonant capacitor unit and in which in at least one operating state high-frequency alternating current with a frequency of at least 1 kHz, in particular of at least 5 kHz, preferably of at least 10 kHz and particularly advantageously flows of at least 15 kHz. In terms of circuitry, the current sensor units are preferably arranged on a side of the heating frequency unit facing away from the rectifier unit.

A "heating current characteristic" should be understood in this context, in particular a variable characterizing the heating current, in particular a voltage drop and preferably an induction voltage. By the fact that the current sensor units are provided "for a measurement of at least one Heizstromkenngröße", should also be understood in particular that the current sensor units are provided to detect a presence and / or a nonexistence of the heating current. By the fact that the current sensor units are "of different types", it should be understood in particular that the two current sensor units are of different types and / or have a different accuracy. The term "accuracy" should be understood in this context in particular as a collective term for precision and / or accuracy. A "precision" is to be understood in particular as meaning a quantitative measure for a scattering of measured values of several measurements of an electric current about an average value of the measured values. In this context, a "correctness" is to be understood in particular as meaning a quantitative measure for a deviation of an average of a plurality of measured values from measurements of an electrical current from the true value of the electrical current.

Such an embodiment can advantageously be used to optimize an induction heating device. In particular, an advantageous adaptation of current sensor units to given requirements can be made possible. Furthermore, operational reliability can be increased advantageously, since in particular a cost-effective current sensor unit can be provided for monitoring a function of a switching unit. A "switching unit" is to be understood in particular a unit which comprises at least one switching element with preferably at least three electrical connections. Preferably, the switching element is designed as a changeover switch which opens at least a first circuit in a switching operation and closes a second circuit.

In a preferred embodiment of the invention, it is proposed that the first current sensor unit has an at least substantially higher accuracy than the second current sensor unit. By "at least substantially higher accuracy" should be understood in particular an at least much higher precision and / or at least much higher accuracy. An "at least substantially higher precision" is to be understood as meaning, in particular, a scattering of measured values of a plurality of measurements of an electric current about an average value of the measured values by at least 20%, in particular by at least 40%, preferably by at least 60% and particularly advantageously by at least 80% , By an "at least much higher accuracy" should in particular by at least 40%, preferably at least 60% and more preferably at least 80% lower deviation of an average of several measured values from measurements of an electric current from the true value of the electric Electricity can be understood. Preferably, only the first current sensor unit is provided for this purpose and in particular suitable for carrying out a precise measurement of a time profile of the heating current for an estimation of a heating power and / or an effective value of the heating current. This can reduce costs.

In a particularly preferred embodiment of the invention, it is proposed that the first current sensor unit is provided in at least one operating state to measure a total current supplied by the heating frequency unit. As a result, an advantageous hob control can be realized. In particular, overstressing and in particular overheating of the heating frequency unit can be avoided.

Advantageously, the induction heating device comprises at least one switching unit, which is provided in at least one operating state to assign the heating frequency unit one of the heating inductors. As a result, a number of heating frequency units can be advantageously reduced compared to a number of heating inductors, which in particular can save costs.

Furthermore, space can be saved and a cooling unit for cooling the heating frequency units can be made smaller. Furthermore, by using a time-division multiplexing method, in which certain heating inductors are periodically supplied with energy by certain heating-frequency units, an advantageously high operating comfort can still be achieved.

In a further embodiment of the invention, it is proposed that the first current sensor unit is arranged in terms of circuitry between the heating frequency unit and the first switching unit. By the fact that a first unit is "arranged in terms of circuitry between a second and a third unit", it should be understood in particular that at least one current path from the second unit to the third unit exists, which is different in particular from a ground line and in which the first unit is arranged. As a result, a measurement of a total current supplied by the heating frequency unit can be made particularly advantageous.

Advantageously, the first current sensor unit is arranged in terms of circuitry between one of the heating inductors and the resonance capacitor unit and, in terms of circuitry, immediately adjacent to the resonance capacitor unit. The fact that a first unit is arranged "in terms of circuit technology immediately adjacent to a second unit should in particular mean that, in particular, between the first unit and the second unit only electrical conductors and components with an electrical resistance of at most 50 Ω, in particular of a maximum of 10 Ω, preferably of at most 5 Ω and particularly advantageously of a maximum of 1 Ω are arranged and that in particular a current path is unbranched from the first unit to the second unit. As a result, further advantageous control variants can be made possible.

It is also proposed that the second current sensor unit is at least provided to determine a presence of the current through one of the heating inductors. Preferably, the second current sensor unit is circuit technology arranged immediately adjacent to one of the heating inductors. Preferably, the second current sensor unit is formed so simple that it is only suitable for detecting the presence of the current. As a result, costs can be reduced particularly advantageous.

In a further embodiment of the invention it is proposed that the induction heating device comprises at least three connection points, which are intended to be connected to at least two outer conductors and at least one neutral conductor of a power supply network. As a result, an overall output of the induction heating device can be advantageously increased.

Advantageously, the second current sensor unit comprises at least one conductor loop, which is provided to measure the Heizstromkenngröße inductively. A "conductor loop" should in particular be understood to mean a shaping of at least one electrical conductor, which preferably has at least one corner and / or at least one bend. An "electrical conductor" is intended in particular to be an electrically conductive element having a specific electrical resistance of at most 10 ^-6 Ωm, in particular of not more than 8 × 10 ^-7 Ωm, preferably of at most 6 × 10 ^-7 Ωm, and particularly advantageously of not more than 4 × 10 ^-7 Ωm at 20 ° C, which has at least one longitudinal extension, viewed in a developed state, which is at least 20 times, in particular at least 30 times, preferably at least 40 times and advantageously at least 50 times greater than at least a transverse to the longitudinal extent transverse extent. Preferably, the conductor loop is arranged on a circuit board and particularly advantageous on both upper sides of the board. Furthermore, the second current sensor unit is preferably coreless. As a result, a particularly cost-effective second current sensor unit can be provided. Furthermore, galvanic isolation can advantageously be achieved.

Further advantages emerge from the following description of the drawing. In the drawing, six embodiments of the invention are shown.

Fig. 1

ein Induktionskochfeld mit einer Induktionsheizvorrichtung in einer Draufsicht,

Fig. 2

ein Schaltbild der Induktionsheizvorrichtung aus Fig. 1 mit einer ersten und einer zweiten Stromsensoreinheit,

Fig. 3a

einen Teil der zweiten Stromsensoreinheit aus Fig. 2 in einer schematischen Darstellung,

Fig. 3b

den Teil der zweiten Stromsensoreinheit aus Fig. 3a in einem montierten Zustand in einer schematischen Darstellung

Fig. 4

einen Teil einer alternativen zweiten Stromsensoreinheit in einem montierten Zustand in einer schematischen Darstellung,

Fig. 5a

einen Teil einer weiteren zweiten Stromsensoreinheit in einer schematischen Darstellung,

Fig. 5b

den Teil der zweiten Stromsensoreinheit in einem montierten Zustand in einer schematischen Darstellung,

Fig. 6

ein Schaltbild einer weiteren Induktionsheizvorrichtung mit einer ersten und einer zweiten Stromsensoreinheit, wobei die erste Stromsensoreinheit an einer ersten Position angeordnet ist,

Fig. 7

ein Schaltbild einer weiteren Induktionsheizvorrichtung mit einer ersten und einer zweiten Stromsensoreinheit, wobei die erste Stromsensoreinheit an einer zweiten Position angeordnet ist, und

Fig. 8

ein Schaubild einer verallgemeinerten Induktionsheizvorrichtung.

Show it:

Fig. 1

an induction hob with an induction heater in a plan view,

Fig. 2

a circuit diagram of the induction heater off Fig. 1 with a first and a second current sensor unit,

Fig. 3a

a part of the second current sensor unit Fig. 2 in a schematic representation,

Fig. 3b

the part of the second current sensor unit Fig. 3a in a mounted state in a schematic representation

Fig. 4

a part of an alternative second current sensor unit in a mounted state in a schematic representation,

Fig. 5a

a part of a further second current sensor unit in a schematic representation,

Fig. 5b

the part of the second current sensor unit in an assembled state in a schematic representation,

Fig. 6

1 is a circuit diagram of a further induction heating device having a first and a second current sensor unit, wherein the first current sensor unit is arranged at a first position,

Fig. 7

a circuit diagram of another induction heating device having a first and a second current sensor unit, wherein the first current sensor unit is arranged at a second position, and

Fig. 8

a diagram of a generalized induction heating.

FIG. 1 shows a trained as induction hob 54a cooking appliance in a plan view. The induction hob 54a includes a cooktop panel 56a. The cooktop panel 56a is made of a glass ceramic. In a mounting position, the hob plate 56a is arranged horizontally and provided for setting up cooking utensils (not shown). On the hob plate 56a are in known Way four heating zones 58a, 60a, 62a, 64a marked. The induction hob 54a comprises an induction heating device for heating the heating zones 58a, 60a, 62a, 64a.

FIG. 2 shows a circuit diagram of the induction heater FIG. 1 The induction heating device has four heating inductors 10a, 12a, 14a, 16a below the hob plate 56a, one of the heating zones 58a, 60a, 62a, 64a being associated with each of the heating inductors 10a, 12a, 14a, 16a. The heating device has two heating frequency units 18a, 20a, by means of which the heating inductors 10a, 12a, 14a, 16a can be supplied with high-frequency alternating current. The two heating frequency units 18a, 20a each include an inverter 66a, 68a. The inverter 66a includes a first insulated gate bipolar transistor (hereinafter abbreviated as "IGBT") 70a and a second IGBT 72a connected in series with the first IGBT 70a. In addition, the inverter 68a has a first IGBT 74a and a second IGBT 76a connected in series with the first IGBT 74a. Alternatively, instead of the IGBTs, any other switching unit that appears appropriate to those skilled in the art can be used, but preferably a bidirectional unipolar switch. Furthermore, heating frequency units may additionally have an attenuation capacitor arranged in particular parallel to a bidirectional unipolar switch.

The induction heating device is intended to be connected via connection points 42a, 44a, 46a to two outer conductors 48a, 50a and a neutral conductor 52a of a country-specific power supply network. Between one of the outer conductors 48a, 50a and the neutral conductor 52a is in each case an electrical voltage with a frequency of 50 Hz and an effective value of 230 V at. The induction heating device described is intended in particular for operation in Germany. The voltage tapped between the outer conductor 48a and the neutral conductor 52a is filtered and rectified in an operating state by a rectifier unit 78a, and then supplied to the heating frequency unit 18a. The between the outer conductor 50a and the neutral conductor 52a tapped voltage is filtered and rectified in an operating state by a rectifier unit 80a and then supplied to the heating frequency unit 20a. Thus, a rectified voltage is applied to an output of the rectifier unit 78a, which is applied between a collector of the IGBT 70a and an emitter of the IGBT 72a. Further, at an output of the rectifier unit 80a, a rectified voltage is applied, which is applied between a collector of the IGBT 74a and an emitter of the IGBT 76a.

Furthermore, the induction heating device has a switching unit 38a. The switching unit 38a comprises four switching elements 82a, 84a, 86a, 88a. The switching elements 82a, 84a, 86a, 88a are identical. The switching elements 82a, 84a, 86a, 88a are SPDT relays. Each of the switching elements 82a, 84a, 86a, 88a has first, second and third contacts. The first contact can be conductively connected to the second or the third contact by means of a corresponding activation. The first contact of the switching element 82a is conductively connected via a line 89a to an emitter of the IGBT 70a. The second contact of the switching element 82a is conductively connected to the first contact of the switching element 84a. The third contact of the switching element 82a is conductively connected via a line 90a to a first contact of the heating inductor 14a. The second contact of the switching element 84a is conductively connected via a line 92a to a first contact of the heating inductor 10a. The third contact of the switching element 84a is conductively connected via a line 94a to a first contact of the heating inductor 12a. In addition, the first contact of the switching element 86a is conductively connected via a line 95a to an emitter of the IGBT 74a. The second contact of the switching element 86a is conductively connected via the line 94a to the first contact of the heating inductor 12a. The third contact of the switching element 86a is connected to the first contact of the switching element 88a. The second contact of the switching element 88a is conductively connected via the line 90a to the first contact of the heating inductor 14a. The third contact of the switching element 84a is conductive connected via a line 96a to a first contact of the heating inductor 16a.

The induction heating apparatus further includes two resonance capacitor units 22a, 24a. The resonant capacitor unit 22a comprises two series-connected resonant capacitors 98a, 100a. The resonant capacitor unit 24a comprises two series-connected resonant capacitors 102a, 104a. A first contact of the resonant capacitor 98a is conductively connected to the collector of the IGBT 70a. A second contact of the resonance capacitor 98a is conductively connected to a second contact of the heating inductor 10a. A first contact of the resonance capacitor 100a is conductively connected to the second contact of the resonance capacitor 98a. A second contact of the resonance capacitor 100a is conductively connected to the emitter of the IGBT 72a. A first contact of the resonant capacitor 102a is conductively connected to the collector of the IGBT 74a. A second contact of the resonant capacitor 102a is conductively connected to a second contact of the heating inductor 16a. A first contact of the resonant capacitor 104a is conductively connected to the second contact of the resonant capacitor 102a. A second contact of the resonant capacitor 104a is conductively connected to the emitter of the IGBT 76a.

Furthermore, the induction heating device has a further switching unit 106a. The switching unit 106a comprises two switching elements 108a, 110a. The switching elements 108a, 110a are identical to the switching elements 82a, 84a, 86a, 88a. The first contact of the switching element 108a is conductively connected to a second contact of the heating inductor 12a. The second contact of the switching element 108a is conductively connected to the second contact of the heating inductor 10a. The third contact of the switching element 108a is conductively connected to the second contact of the heating inductor 16a. The first contact of the switching element 110a is conductively connected to a second contact of the heating inductor 14a. The second contact of the switching element 110a is conductive with the second Contact of the heating inductor 10a connected. The third contact of the switching element 110a is conductively connected to the second contact of the heating inductor 16a.

The induction heating device comprises two first current sensor units 26a, 28a, which measure a heating current supplied by the heating frequency units 18a, 20a, wherein a control unit (not shown) of the induction hob 54a uses this information in a known manner to control and / or regulate the heating frequency units 18a, 20a. The first current sensor unit 26a measures the heating current flowing through the line 89a. The first current sensor unit 28a measures the heating current flowing through the line 95a. Thus, in an operating state, the first current sensor units 26a, 28a respectively measure a total heating current supplied by the respective heating frequency unit 18a, 20a. The first current sensor units 26a, 28a are each arranged in a resonant circuit. The first current sensor units 26a, 28a measure the heating current in each case by electromagnetic induction in a conductor loop, whereby a galvanic separation can be achieved directly. The first current sensor units 26a, 28a are specially designed for measuring the high-frequency heating current and have a correspondingly high accuracy in the frequency range between 20 kHz and 100 kHz.

By means of the switching unit 38a, an assignment of the heating frequency units 18a, 20a to the heating inductors 10a, 12a, 14a, 16a can be made by the control unit. Furthermore, by means of the switching unit 106a, an allocation of the resonance capacitor units 22a, 24a to the heating inductors 10a, 12a, 14a, 16a can be made by the control unit. Thus, in spite of a smaller number of heating frequency units 18a, 20a than on heating inductors 10a, 12a, 14a, 16a, an advantageously high operating comfort can be achieved. In particular, costs can be saved due to the smaller number of heating frequency units 18a, 20a.

For operational safety monitoring of a switching function of the switching unit 38a is essential. So are in particular those potentially unsafe To avoid operating conditions in which another heating inductor 10a, 12a, 14a, 16a than actually desired by an operator is heated, for example due to a malfunction of the switching unit 38a. For this purpose, second current sensor units 30a, 32a, 34a, 36a are provided, which detect at least one presence of the heating current in the lines 90a, 92a, 94a, 96a. The second current sensor units 30a, 32a, 34a, 36a are respectively arranged in the immediate vicinity of the heating inductors 10a, 12a, 14a, 16a and thus in resonant circuits. The second current sensor units 30a, 32a, 34a, 36a operate on the principle of electromagnetic induction, which can also be achieved by a galvanic isolation. The first current sensor units 26a, 28a and the second current sensor units 30a, 32a, 34a, 36a are of different types. Thus, the first current sensor units 26a, 28a each have at least substantially higher accuracy than the second current sensor units 30a, 32a, 34a, 36a. The second current sensor units 30a, 32a, 34a, 36a can be designed such that they are only suitable for determining the presence of the heating current in the relevant line 90a, 92a, 94a, 96a. In an operating state, it is determined by the control unit whether current is flowing only through those lines 90a, 92a, 94a, 96a through which current should actually flow. If an unexpected current flow occurs in one of the lines 90a, 92a, 94a, 96a, this is an indication of a malposition of the switching unit 38a. When such a malposition occurs, the control unit causes at least a shutdown of the heating frequency units 18a, 20a and optionally an output of an error message and / or a maintenance request.

For the second current sensor units 30a, 32a, 34a, 36a, any current sensor units which appear reasonable to the person skilled in the art come into consideration, in particular those in FIGS FIGS. 3a, 3b, 4 . 5a and 5b shown. The second current sensor units 30a-c, 32a-c, 34a-c, 36a-c shown here have in common that they each comprise a conductor loop 40a-c, which is provided to inductively measure the heating current.

FIG. 3a shows a part of the second current sensor unit 30a in a schematic representation. Corresponding parts of the second current sensor units 32a, 34a, 36a are constructed identically. The conductor loop 40a of the current sensor unit 30a is mounted on a board 136a. The conductor loop 40a extends partially on an upper side 138a and partly on an underside 140a of the board 136a. Parts of the conductor loop 40a, which run on the bottom 140a of the board 136a, are in the FIGS. 3a and 3b shown in dashed lines. About bushings 142a, of which in the FIGS. 3a and 3b For reasons of clarity, only one is designated in each case, the parts of the conductor loop 40a are conductively connected by the circuit board 136a from the upper side 138a to the lower side 140a. The conductor loop 40a has at least substantially a cuboid outer contour and, together with the feedthroughs 142a, forms a coil whose coil surface is oriented perpendicular to the printed circuit board 136a.

FIG. 3b shows a schematic representation of the second current sensor unit 30a in an assembled state. In the installed state, the line 92a, which is electrically insulated from an environment, is guided along the top side 138a of the board 136a and at least substantially parallel to the coil surface. In an operating state, a voltage proportional to the time change of the heating current is induced in the conductor loop 40a by the high-frequency heating current in the line 92a. By means of a suitable measuring circuit (not shown), the presence of the heating current in the line 92a can thus be detected. Depending on the measuring circuit, even a frequency of the heating current can be determined, whereby an association with one of the heating frequency units 18a, 20a can be made possible, namely the heating frequency unit 18a, 20a, which is operated at the same frequency.

In the FIGS. 4 . 5a . 5b . 6 . 7 and 8th five further embodiments of the invention are shown. The following descriptions are essentially limited to the differences between the embodiments, with respect to the same components, features and functions on the description of the other embodiments, in particular the FIGS. 1 . 2 . 3a and 3b , can be referenced. To distinguish the embodiments, the letter a in the reference numerals of the embodiment in the FIGS. 1 . 2 . 3a and 3b by the letters b to f in the reference numerals of the embodiments of FIGS. 4 . 5a . 5b . 6 . 7 and 8th replaced. With regard to identically named components, in particular with regard to components having the same reference numerals, it is also possible in principle to refer to the figures and / or the description of the other exemplary embodiments, in particular, FIGS FIGS. 1 . 2 . 3a and 3b , to get expelled.

FIG. 4 shows a part of another second current sensor unit 30b in a schematic representation. The conductor loop 40b of the current sensor unit 30b is also mounted on a board 136b. As in the previous case, components which are arranged along an underside 140b of the board 136b are also shown in dashed lines in FIG. The present embodiment differs from the previous exemplary embodiment only in that a return line 144b coming from a heating inductor 10b and insulated from an environment is additionally arranged in antiparallel to a line 92b leading to the heating inductor 10b, so that a heating current flows in anti-parallel. In this case, the line 92b is guided along an upper side 138b of the board 136b and the return line 144b is guided along the lower side 140b. Both the line 92b and the return line 144b are aligned at least substantially parallel to a coil surface of a coil formed by the conductor loop 40b and feedthroughs 142b. By such a structure, a sensitivity twice as high as in the previous embodiment can be achieved.

FIG. 5a shows a part of another second current sensor unit 30c in a schematic representation. The conductor loop 40c of the current sensor unit 30c is also applied to a board 136c. The conductor loop 40c runs partially on an upper side 138c and partly on an underside 140c of the board 136c. Parts of the conductor loop 40 c, which run on the bottom 140 c of the board 136 c, are in the FIGS. 5a and 5b shown in dashed lines. About accomplishments 142c, of which in the FIGS. 5a and 5b For clarity, only one is designated, the parts of the conductor loop 40c are conductively connected by the board 136c from the top 138c to the bottom 140c. The conductor loop 40c has at least substantially a toroidal outer contour and, together with the feedthroughs 142a, forms a Rogowski coil. In a middle of the Rogowski coil, a recess 146c is provided in the board 136c. The recess 146c is circular in a vertical view of the board 136c.

FIG. 5b shows a schematic representation of the second current sensor unit 30c in an assembled state. A relative to an environment electrically insulated line 92c, which is provided to a power supply of a heating inductor 10c, is guided in the mounted state through the recess 146c. In an operating state, a voltage proportional to the time change of the heating current is induced in the conductor loop 40c by the high-frequency heating current in the line 92c. By means of a suitable measuring circuit (not shown), the presence of the heating current in the line 92c can thus be detected. Depending on the measuring circuit, a frequency of the heating current can also be determined here, whereby an assignment to a heating frequency unit 18c, 20c can be made possible, namely to the heating frequency unit 18c, 20c, which is operated at the same frequency.

FIG. 6 shows a circuit diagram of another induction heating device of an induction hob 54d. The induction heating device is intended to be connected via connection points 42d, 46d to only one outer conductor 48d and one neutral conductor 52d of a country-specific power supply network. Between the outer conductor 48d and the neutral conductor 52d, an electrical voltage with a frequency of 50 Hz and an effective value of 230 V is applied. The induction heating device described is intended in particular for operation in Germany. For an induction heater intended for US operation, the frequency is 60 Hz and the RMS value is 110 V. The voltage between the outer conductor 48d and the neutral conductor 52d tapped voltage is filtered in one operating state by a rectifier unit 78d and rectified and then fed in parallel two Heizfrequenzeinheiten 18d, 20d. The heating frequency units 18d, 20d each include an inverter 66d, 68d each having two IGBTs 70d, 72d, 74d, 76d. Thus, at an output of the rectifier unit 78d, a rectified voltage is applied, which is applied between a collector of the IGBT 70d and an emitter of the IGBT 72d. Further, at the output of the rectifier unit 78d, a rectified voltage is applied, which is applied between a collector of the IGBT 74d and an emitter of the IGBT 76d.

Furthermore, the induction heating device has a switching unit 38d. The switching unit 38da comprises six switching elements 82d, 84d, 86d, 88d, 108d, 110d. The switching elements 82d, 84d, 86d, 88d are identical. The switching elements 82d, 84d, 86d, 88d are SPDT relays. Each of the switching elements 82d, 84d, 86d, 88d, 108d, 110d has first, second, and third contacts and a coil. The first contact can be conductively connected to the second or the third contact by means of a corresponding activation. The first contact of the switching element 82d is conductively connected via a line 89d to an emitter of the IGBT 70d. Further, the second contact of the switching element 82d is connected to the first contact of the switching element 84d. The third contact of the switching element 82d is conductively connected to the first contact of the switching element 86d. The second contact of the switching element 84d is conductively connected via a line 92d to a first contact of a heating inductor 10d. The third contact of the switching element 84d is conductively connected via a line 94d to a first contact of a heating inductor 12d. The second contact of the switching element 86d is conductively connected via a line 90d to a first contact of a heating inductor 14d. The third contact of the switching element 86d is conductively connected via a line 96d to a first contact of a heating inductor 16d. In addition, the first contact of the switching element 88d is conductively connected via a line 95d to an emitter of the IGBT 74d. Further, the second contact of the switching element 88d is connected to the first contact of the switching element 110d. The third contact of the Switching element 82d is conductively connected to the first contact of the switching element 108d. The second contact of the switching element 110d is conductively connected via the line 92d to the first contact of the heating inductor 10d. The third contact of the switching element 110d is conductively connected via the line 94d to the first contact of the heating inductor 12d. The second contact of the switching element 108d is conductively connected via the line 90d to the first contact of the heating inductor 14d. The third contact of the switching element 108d is conductively connected via the line 96d to the first contact of the heating inductor 16d.

The induction heating apparatus further includes two resonance capacitor units 22d, 24d. The resonant capacitor unit 22d comprises two series-connected resonant capacitors 98d, 100d. The resonant capacitor unit 24d comprises two series-connected resonant capacitors 102d, 104d. A first contact of the resonance capacitor 98d is conductively connected to the collector of the IGBT 70d and the collector of the IGBT 74d. A second contact of the resonant capacitor 98d is conductively connected to a second contact of the heating inductor 10d and a second contact of the heating inductor 12d. A first contact of the resonant capacitor 100d is conductively connected to the second contact of the resonant capacitor 98d. A second contact of the resonance capacitor 100d is conductively connected to the emitter of the IGBT 72d and the emitter of the IGBT 76d. A first contact of the resonance capacitor 102d is conductively connected to the collector of the IGBT 70d and the collector of the IGBT 74d. A second contact of the resonant capacitor 102d is conductively connected to a second contact of the heating inductor 14d and a second contact of the heating inductor 16d. A first contact of the resonant capacitor 104d is conductively connected to the second contact of the resonant capacitor 102d. A second contact of the resonant capacitor 104d is conductively connected to the emitter of the IGBT 72d and the emitter of the IGBT 76d.

The induction heater also includes two first current sensor units 26d, 28d, each of which measures a total current supplied by the heating frequency units 18d, 20d in the respective lines 89d, 95d. Further For example, the induction heater includes second current sensor units 30d, 32d, 34d, 36d which detect at least one presence of the heating current in the lines 90d, 92d, 94d, 96d. The second current sensor units 30d, 32d, 34d, 36d are each arranged in circuit configuration in the immediate vicinity of the heating inductors 10d, 12d, 14d, 16d. For the second current sensor units 30d, 32d, 34d, 36d, any current sensor units that appear reasonable to the person skilled in the art come into question, in particular those in FIGS FIGS. 3a, 3b, 4 . 5a and 5b shown.

FIG. 7 shows a circuit diagram of an alternative induction heating device of an induction hob 54e. The present induction heater is largely identical to the induction heater of the embodiment of FIG FIG. 6 built up. It differs only in a position of first current sensor units 26e, 28e. In the present exemplary embodiment, these are arranged in terms of circuit technology between heating inductors 10e, 12e, 14e, 16e and resonance capacitor units 22e, 24e and, in terms of circuitry, immediately adjacent to the resonance capacitor units 22e, 24e. The first current sensor unit 26e is arranged between a second terminal of the heating inductor 10e and a second terminal of the heating inductor 12e and a second terminal of a resonance capacitor 98e and a first terminal of a resonance capacitor 100e. The first current sensor unit 28e is arranged between a second terminal of the heating inductor 14e and a second terminal of the heating inductor 16e and a second terminal of a resonance capacitor 102e and a first terminal of a resonance capacitor 104e. This arrangement of the first current sensor units 26e, 28e is preferred when two heating inductors 10e, 12e, 14e, 16e are each operated by their own heating frequency unit 18e, 20e, but on a single common resonant capacitor unit 22e, 24e. In this case, the heating frequency units 18e, 20e are operated at the same frequency, wherein a setting of a heating power of the heating inductors 10e, 12e, 14e, 16e is performed via a relative phase shift.

FIG. 8 FIG. 12 is a diagram of an induction heater of an induction hob 54f. FIG. The present induction heater is a generalization of the induction heaters from the Figures 2 . 6 and 7 The induction heater is generally provided for connection to one or more outer conductors 48f and to a neutral conductor 52f. In the following, the induction heater is described only for an outer conductor 48f. However, the corresponding parts are identical for the other outer conductors. Further, in FIG. 8 For clarity, only for the outer conductor 48f an identification of components with reference numerals. The induction heater has a rectifier unit 78f for each outer conductor 48f. Furthermore, for each outer conductor 48f, the induction heating device comprises one or more heating frequency units 18f, which in the case of a plurality of heating frequency units 18f are supplied with a rectified voltage in parallel by the rectifier unit 78f. An allocation of the heating frequency unit 18f or the heating frequency units 18f to heating inductors 10f, 12f, 14f is possible via a switching unit 38f. It should be noted that via phase-spanning lines 112f, 114f, 116f a connection to Heizinduktoren the other outer conductor is possible. Via a further switching unit 106f, it is possible to associate one or more resonance capacitor units 22f of the induction heating apparatus with the heating inductors 10f, 12f, 14f. Here too, phase-spanning lines 118f, 120f, 122f are provided, which allow a connection to heating inductors of the remaining outer conductors. The induction heating device further comprises a control unit 124f, which is provided via a decoupling unit 126f for controlling and / or regulating the heating-frequency units 18f. The decoupling unit 126f provides for a galvanic decoupling.

For first current sensor units, two different sensor positions 128f, 130f per outer conductor 48f are possible, with only one sensor position 128f, 130f being designated for the sake of clarity. The sensor positions 128f are arranged in terms of circuitry between the heating frequency units 18f and the switching units 38f. The sensor positions 130f are circuit-wise between the switching units 106f and the resonance capacitor units 22f. Two different sensor positions 132f, 134f are provided for the second current sensor units, with only one sensor position 132f, 134f being designated for the sake of clarity. The sensor positions 132f are arranged in terms of circuitry between the switching units 38f and the heating inductors 10f, 12f, 14f. The sensor positions 134f are arranged in terms of circuitry between the heating inductors 10f, 12f, 14f and the switching units 106f. reference numeral 10 heating inductor 64 heating zone 12 heating inductor 66 inverter 14 heating inductor 68 inverter 16 heating inductor 70 IGBT 18 Heizfrequenzeinheit 72 IGBT 20 Heizfrequenzeinheit 74 IGBT 22 Resonant capacitor unit 76 IGBT 24 Resonant capacitor unit 78 Rectifier unit 26 First current sensor unit 80 Rectifier unit 28 First current sensor unit 82 switching element 30 Second current sensor unit 84 switching element 32 Second current sensor unit 86 switching element 34 Second current sensor unit 88 switching element 36 Second current sensor unit 89 management 38 switching unit 90 management 40 conductor loop 92 management 42 junction 94 management 44 junction 95 management 46 junction 96 management 48 outer conductor 98 resonant capacitor 50 outer conductor 100 resonant capacitor 52 neutral 102 resonant capacitor 54 Induction hob 104 resonant capacitor 56 Hotplate 106 switching unit 58 heating zone 108 switching element 60 heating zone 110 switching element 62 heating zone 112 Inter-phase management 114 Inter-phase management 116 Inter-phase management 118 Inter-phase management 120 Inter-phase management 122 Inter-phase management 124 control unit 126 decoupling unit 128 sensor position 130 sensor position 132 sensor position 134 sensor position 136 circuit board 138 top 140 bottom 142 execution 144 return 146 recess

Claims (10)

1. Induction heating apparatus with at least two heating inductors (10a-f, 12a-f, 14a-f, 16a-e), at least one heating frequency unit (18a-f, 20a-e) to supply the heating inductors (10a-f, 12a-f, 14a-f, 16a-e) with a heating current, at least one resonance capacitor unit (22a-f, 24a-e), at least one first current sensor unit (26a-e, 28a-e) and at least one second current sensor unit (30a-e, 32a-e, 34a-e, 36a-e), each of which being arranged in at least one resonance circuit and being provided for measuring at least one heating current parameter, characterised in that the first current sensor unit (26a-e, 28a-e) and the second current sensor unit (30a-e, 32a-e, 34a-e, 36a-e) have a different accuracy.
2. Induction heating apparatus according to claim 1, characterised in that the first current sensor unit (26a-e, 28a-e) has an at least essentially higher accuracy than the second current sensor unit (30a-e, 32a-e, 34a-e, 36a-e).
3. Induction heating apparatus according to claim 1 or 2, characterised in that the first current sensor unit (26a-e, 28a-e), in at least one operating state, is provided to measure a total current supplied by the heating frequency unit (18a-e, 20a-e).
4. Induction heating apparatus according to one of the preceding claims, characterised by at least one switching unit (38a-f) which, in at least one operating state, is provided to assign the heating frequency unit (18a-f, 20a-e) one of the heating inductors (10a-f, 12a-f, 14a-f, 16a-e).
5. Induction heating apparatus according to claim 4, characterised in that the first current sensor unit (26a-2, 28a-e) is arranged in terms of circuit technology between the heating frequency unit (18a-e, 20a-e) and the switching unit (38a-e).
6. Induction heating apparatus according to one of the preceding claims, characterised in that the first current sensor unit (26e, 28e) is arranged in terms of circuit technology between one of the heating inductors (10e, 12e, 14e, 16e) and the resonance capacitor unit (22e, 24e) and in terms of circuit technology immediately adjacent to the resonance capacitor unit (22e, 24e).
7. Induction heating apparatus according to one of the preceding claims, characterised in that the second current sensor unit (30a-e, 32a-e, 34a-e, 36a-e) is at least provided to determine a presence of the current through one of the heating inductors (10a-e, 12a-e, 14a-e, 16a-e).
8. Induction heating apparatus according to one of the preceding claims, characterised in that the second current sensor unit (30a-e, 32a-e, 34a-e, 36a-e) comprises at least one conductor loop (40a-e), which is provided to measure the heating current parameter inductively.
9. Induction heating apparatus according to one of the preceding claims, characterised by at least three terminal points (42a-c, 42f, 44a-c, 46a-c, 46f), which are provided to be connected to at least two external conductors (48a-c, 48f, 50a-c) and at least one neutral conductor (52a-c, 52f) of a power supply network.
10. Cooking appliance, in particular induction hob (54a-f), with an induction heating apparatus according to one of the preceding claims.

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